HIV/AIDS Glossary

 

AIDS Medical Glossary and Drug Chart

This Glossary was created by the staff of Gay Men’s Health Crisis. Gay Men's Health Crisis (GMHC) is a not-for-profit, volunteer-supported and community-based organization committed to national leadership in the fight against AIDS. To learn more click here: http://www.gmhc.org/index.html

A - D  |  E - J  |  K - O  |  P - Z

 

Definitions are given by the full name of the term or generic name of the drug, not by the abbreviation or brand name. For example, the definition of KS will be found under Kaposi's Sarcoma. The only abbreviations commonly used within definitions are HIV, AIDS, RNA, DNA, and FDA.

Terms used that are defined elsewhere in the Glossary are in CAPITALS.

The drug chart lists alternative names for commonly prescribed medications.

3TC: see LAMIVUDINE.

5-FC: see FLUCYTOSINE.

A

Abacavir (Ziagen, ABC): a NUCLEOSIDE ANALOG or NRTI made by GlaxoSmithKline. Abacavir is one of the three component drugs in TRIZIVZIR. Life-threatening allergic reaction can occur in three to five percent of people who are starting abacavir.

Abelcet: see AMPHOTERICIN B.

Accelerated Approval: expedited FOOD AND DRUG ADMINISTRATION (FDA) approval of a new treatment based on early SURROGATE MARKER data from clinical studies. The purpose of accelerated approval is to hasten the availability of new drugs for serious or life-threatening conditions.

Acemannan (Carrisyn): the potentially active ingredient in aloe vera juice. A few IN VITRO studies have suggested that acemannan has activity against HIV and also up-regulates CELL-MEDIATED IMMUNITY.

Acetaminophen (Tylenol): a synthetic drug that reduces fever and pain. It is often found in cold and flu medications.

Acidophilus: BACTERIA found in yogurt that may help restore a supportive bacterial environment in an intestinal tract if the normal intestinal bacterial population ("flora") has been disturbed by disease or ANTIBIOTICS. Ingesting acidophilus also may be useful in preventing CANDIDIASIS (THRUSH), including in the vagina.

Acquired Immune Response: see IMMUNE SYSTEM.

Acquired Immunodeficiency Syndrome (AIDS): the late stage of the illness triggered by infection with HUMAN IMMUNODEFICIENCY VIRUS (HIV). According to the official definition published by the CENTERS FOR DISEASE CONTROL (CDC), a person receives an AIDS diagnosis when he or she has a CD4 CELL COUNT of less than 200 and/or certain OPPORTUNISTIC CONDITIONS common with advanced IMMUNE DEFICIENCY (see AIDS-DEFINING ILLNESS).

AACTG: see ADULT AIDS CLINICAL TRIALS GROUP.

Activated CD4 Cells: CD4 CELLS that have come in contact with an ANTIGEN-PRESENTING CELL and are dividing. Compare RESTING CD4 CELLS.

Activity: the ability of a drug to control or inhibit a PATHOGEN. Activity may be determined in the laboratory and differs from EFFICACY, which is the ability of a treatment to alter the course of clinical disease.

Activity Study: a study or trial that tests the ACTIVITY of a drug.

ACTU: see AIDS CLINICAL TRIALS UNIT.

Acupressure: a Chinese therapy that is based on ACUPUNCTURE but uses finger pressure rather than needles. Acupressure is used to relieve tension, stress and pain, perhaps due to the release of endorphins.

Acupuncture: A Chinese therapy that uses needles to press energy ("chi") points on the body's surface. It may be useful as a means to reduce pain, to aid in quitting smoking or to treat alcoholism and drug abuse.

Acute: refers to intense, short-term symptoms or illnesses that either resolve or evolve into long-lasting, CHRONIC disease manifestations.

Acute HIV Infection: see PRIMARY HIV INFECTION.

Acyclovir (Zovirax): an ANTIVIRAL drug used in the treatment of herpes simplex virus 1 (fever blisters, cold sores), herpes simplex virus 2 (genital herpes) and herpes zoster (SHINGLES). (See HERPES VIRUS.) Acyclovir comes in the form of capsules or pills, ointment or injection. Acyclovir causes few SIDE EFFECTS, occasionally nausea, vomiting or headaches.

ADAP: see AIDS DRUG ASSISTANCE PROGRAM.

ADC: see AIDS DEMENTIA COMPLEX.

ADCC: see ANTIBODY-DEPENDENT CELL-MEDIATED CYTOTOXICITY.

Adefovir Dipivoxil (Hepsera, bis-POM PMEA): a NUCLEOTIDE ANALOG made by Gilead Sciences, approved to treat HEPATITIS B infection. A program to develop a higher dose of adefovir for the treatment of HIV was halted due to NEPHROTOXICITY.

Adenine: one of the four bases of RNA (which also includes CYTOSINE, GUANINE and URACIL) and DNA (which also includes cytosine, guanine and THYMINE).

Adenopathy: an enlargement of the LYMPH NODES or other glands.

Adenosine: a NUCLEOSIDE of ADENINE. DIDANOSINE (ddI) is an ANALOG of adenosine.

Adenovirus: a group of VIRUSES that causes upper respiratory tract infections, including the common cold, as well as gastrointestinal and eye infections.

Adherence: the degree to which a patient sticks to a schedule for taking medicines. Non-adherence may lead to drug RESISTANCE. A synonym for compliance.

Adipocyte: a cell that makes up fat tissue.

Adipogenesis: a process by which STEM CELLS mature into ADIPOCYTES, or fat cells.

Adipose: fat.

Adjuvant: in VACCINES, a substance added to increase the IMMUNE RESPONSE to the ANTIGEN.

Adjuvant Therapy: a secondary therapy that is intended to improve the outcome of primary therapy. For example, after removing a cancerous tumor (primary therapy), CHEMOTHERAPY is often used as adjuvant therapy.

Administration: the way in which a drug is taken, e.g., orally or by injection.

Adrenal Glands: a pair of glands located on the kidneys. The adrenal glands secrete steroid hormones, CORTISOL and adrenaline.

Adriamycin: see DOXORUBICIN.

Advanced HIV Infection: see ACQUIRED IMMUNODEFICIENCY SYNDROME.

Adverse Event: a toxic reaction to a medical therapy. These can be mild (headache, drowsiness) to severe (kidney or liver failure, seizures, PERIPHERAL NEUROPATHY). Also see SIDE EFFECT.

Adverse Reaction: see ADVERSE EVENT.

Aerosolized: a form of a drug that has been made into a fine mist for inhalation.

Affective: relating to psychological mood.

Affective Illness: a condition that affects moods, e.g., DEPRESSION.

Agenerase: see AMPRENAVIR.

Agonist: (1) A drug or other substance that enhances the effect of another drug or substance; (2) an agent that promotes cellular activity by binding to a CELL SURFACE RECEPTOR. Compare to ANTAGONIST.

AIDS: see ACQUIRED IMMUNODEFICIENCY SYNDROME.

AIDS Clinical Trials Unit (ACTU): a site at which AIDS drug CLINICAL TRIALS, sponsored by the NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES (NIAID), are performed.

Adult AIDS Clinical Trials Group (AACTG): a network of medical centers around the country in which federally funded CLINICAL TRIALS are conducted to test the safety and effectiveness of treatments for HIV infection and its complications.

ACTG studies are sponsored by the NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES (NIAID), a branch of the NATIONAL INSTITUTES OF HEALTH (NIH). See also: Pediatric AIDS Clinical Trials Group (PACTG)

AIDS-Defining Illness: one of the serious illnesses that occurs in HIV-positive individuals and a reason for an AIDS diagnosis according to the CENTERS FOR DISEASE CONTROL's definition of AIDS. Among these conditions are PNEUMOCYSTIS CARINII PNEUMONIA (PCP), MYCOBACTERIUM AVIUM COMPLEX (MAC), AIDS DEMENTIA COMPLEX, AIDS WASTING SYNDROME, invasive cervical cancer and KAPOSI'S SARCOMA (KS).

AIDS Dementia Complex (ADC): a brain disorder in people with AIDS that results in the loss of cognitive capacity, affecting the ability to function in a social or occupational setting. Its cause has not been determined exactly, but may result from HIV infection of cells in the brain or an inflammatory reaction to HIV infection.

AIDS Drug Assistance Program (ADAP): ADAPs serve people with HIV/AIDS who are uninsured or underinsured, including those who are not disabled and, therefore, ineligible for programs like Medicaid. ADAPs are authorized by the RYAN WHITE CARE ACT. Federal funding goes to states, which use a portion of the money to provide HIV/AIDS drugs, including PROPHYLAXIS and treatments of OPPORTUNISTIC CONDITIONS, to those who cannot otherwise afford the medications.

AIDS-Related Complex (ARC): an archaic term for a stage before AIDS, with symptoms such as swollen LYMPH NODES, long-lasting night sweats, fevers and unusual weight loss. Also commonly called symptomatic HIV infection. The term is no longer officially recognized by the CENTERS FOR DISEASE CONTROL.

AIDS-Related Wasting: see WASTING SYNDROME.

a-IFN: see ALPHA INTERFERON.

Alanine Aminotransaminase (ALT): a liver ENZYME, like ASPARTATE AMINOTRANSAMINASE, that plays a role in PROTEIN METABOLISM. Elevated SERUM levels of ALT are a sign of liver damage from disease or drugs. ALT is also known as serum glutamic pyruvic transaminase (SGPT).

Albendazole (Albenza): an approved treatment for two types of tapeworm larvae, which has been proposed as a treatment for MICROSPORIDIOSIS. The drug works by inhibiting cellular movement. Albendazole frequently impairs liver function and occasionally produces life-threatening reductions in total white blood cell (LEUKOCYTE) count.

Albenza: see ALBENDAZOLE.

Alfa Interferon: see ALPHA INTERFERON.

Alkaline Phosphatase: an ENZYME produced in the liver as well as in bone and other tissues. Elevated SERUM levels of the enzyme are indicative of liver disease, BILE DUCT obstruction in particular.

Allele: an alternate form of a specific GENE on a chromosome. Each allele is an individual member of a gene pair and is inherited from one parent.

Alopecia: hair loss.

Alpha Interferon (alfa-IFN, Roferon, Intron A, Pegasys, PEG-Intron): 1) a substance secreted by virally infected cells that strengthens the defenses of nearby uninfected cells. 2) alfa-IFN is an approved treatment for KAPOSI'S SARCOMA, HEPATITIS B and HEPATITIS C. Also see INTERFERON, PEGYLATED INTERFERON.

ALT: see ALANINE AMINOTRANSAMINASE.

Alternative Medicine: a catch-all phrase for a long list of treatments or medicinal systems, including traditional systems such as Chinese or Ayurvedic medicine as well as homeopathy, various herbal and many other miscellaneous treatments that have not been accepted by the mainstream, or Western, medical establishment. Alternative medicine may also be referred to as COMPLEMENTARY MEDICINE. The designation alternative medicine is not equivalent to HOLISTIC MEDICINE.

Ambien: see ZOLPIDEM.

Ambulatory: the ability to walk or move about unaided. Ambulatory care usually refers to outpatient medical care, and an ambulatory patient is one who is not bedridden.

Amdoxovir: an experimental NUCLEOSIDE ANALOG from Gilead Sciences.

Amebiasis: see AMOEBIASIS.

Amenorrhea: a temporary or permanent suppression of menstruation.

Amino Acid: any of the nitrogen-containing ORGANIC MOLECULES that are the building blocks for PROTEINS. The human body uses 20 of the 80 amino acids found in nature.

Amitriptyline (Elavil): a TRICYCLIC ANTIDEPRESSANT that is also sometimes used to treat pain.

Amoebiasis: a parasitic intestinal infection caused by tiny unicellular microorganisms called amoebas. Symptoms include diarrhea, bloating and abdominal pain. Also called amebiasis.

Amphotericin B (Fungizone, Abelcet, AmBisome): an INTRAVENOUS drug for treatment of CRYPTOCOCCAL MENINGITIS, CANDIDIASIS, HISTOPLASMOSIS and coccidiomycosis and other fungal infections. TOXICITIES are severe and include fevers, chills, headache, ANOREXIA, nausea, vomiting, diarrhea, kidney damage and NEUTROPENIA. LIPID-complexed, somewhat safer, forms of IV amphotericin B (brand names: Abelcet, AmBisome) are available.

Amprenavir (Agenerase): a PROTEASE INHIBITOR made by GlaxoSmithKline. It is available in capsule form or as an oral suspension. Common ADVERSE EVENTS are nausea and vomiting. There is also a heavy PILL BURDEN. A PRODRUG of amprenavir (see VX-175/GW-433908) is in development and may require fewer and smaller capsules.

Amyl Nitrate (Poppers): an inhalant that dilates the blood vessels, producing a temporary high. It is used recreationally to enhance sexual enjoyment. Amyl nitrate should not be used with Viagra (SILDENAFIL CITRATE).

Amylase: a starch-splitting ENZYME secreted by salivary glands and the pancreas to aid digestion of food. An increase in amylase SERUM levels may indicate PANCREATITIS, a possible life-threatening consequence of DIDANOSINE (ddI).

Anabolic: refers to metabolic processes that build new tissue in the body. Compare CATABOLIC.

Anabolic Steroid: a synthetic STEROID used to increase muscle mass and weight. Anabolic steroids are versions of the natural hormone TESTOSTERONE but have fewer masculinizing, or androgenic, effects. Anabolic steroids have been used to reverse AIDS-related WASTING SYNDROME in men with low testosterone levels, although long-term safety and EFFICACY of this treatment are not known.

Anadrol: see OXYMETHOLONE.

Analgesic: both noun and adjective, refers to a compound or therapy that reduces pain. Tylenol, aspirin and the OPIATES are examples of analgesic drugs.

Analog (Analogue): a molecule that resembles another molecule structurally and that can, often, be substituted for the original. NUCLEOSIDE ANALOGS are non-functioning analogs of molecules that HIV uses to copy its DNA.

Anaphylaxis: a severe allergic reaction to an ANTIGEN, causing airway closure, low blood pressure and lung spasms. In the absence of treatment, this condition ultimately leads to life-threatening shock (collapse due to insufficient blood flow in the body) and death. Prompt treatment with an injection of epinephrine reverses the symptoms.

Ancobon: see FLUCYTOSINE.

Androgen: a HORMONE or synthetic substance with masculinizing (or androgenic) effects, such as TESTOSTERONE.

Anecdotal Evidence: evidence that has not been confirmed by controlled scientific methods, usually presented as individual case reports.

Anemia: the incapacity of blood to transport enough oxygen to the body's tissues. Anemia may be caused by an abnormally low number of red blood cells or insufficient or defective HEMOGLOBIN, the PROTEIN that carries oxygen in red blood cells. It is a condition that is often caused by AZT (ZIDOVUDINE), as well as by other drugs and illnesses that suppress red blood cell production in the BONE MARROW.

Anergic: relating to the IMMUNE SYSTEM's inability to produce a marked reaction in response to foreign ANTIGENS. For example, HIV-infected individuals who do not react to the TUBERCULOSIS skin test (see PURIFIED PROTEIN DERIVATIVE TEST) even though they have contracted a tuberculosis infection are considered to be anergic.

Angiogenesis: the process of new blood vessel growth. Tumors and KAPOSI'S SARCOMA lesions stimulate angiogenesis to supply themselves with blood.

Anorexia: a lack or loss of appetite that leads to significant decline in weight.

Antagonist: a characteristic of drugs when their combined effect is less than the sum of their individual effects. Compare AGONIST.

Antibiotic: an agent that kills or inhibits the growth of microorganisms, especially a compound similar to those produced by certain FUNGI for destroying BACTERIA. An antibiotic is used to combat infection.

Antibody: a disease-fighting PROTEIN created by the IMMUNE SYSTEM, also known as IMMUNOGLOBULIN. Antibodies coat, mark for immune destruction or render harmless foreign matter such as BACTERIA, VIRUSES or dangerous toxins. Antibodies also tag virus-infected cells, making them vulnerable to attack by the IMMUNE SYSTEM. Each antibody attaches itself to a single specific chemical sequence (EPITOPE) in an ANTIGEN.

Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC): an IMMUNE RESPONSE that results when ANTIBODIES attach to ANTIGENS on the surface of a cell. The cell that is covered by the antibodies is destroyed by white blood cells (LEUKOCYTES).

Antibody-Mediated Immunity: a type of IMMUNE RESPONSE that involves the mobilization of B CELLS, which produce ANTIBODIES.

Antibody Positive: the presence of ANTIBODIES in the blood that indicates previous exposure to a particular ANTIGEN.

Antiemetic: a drug that lessens nausea and vomiting.

Antigen: a foreign substance, usually a PROTEIN that stimulates an immune response. An antigen may have several subunits called EPITOPES that are targets of specific ANTIBODIES or CYTOTOXIC T LYMPHOCYTES.

Antigen Presenting Cell (APC): a cell, such as a MACROPHAGE or DENDRITIC CELL, that digests foreign bodies and exhibits the resulting pieces of the PROTEIN (ANTIGEN) on its surface in an effort to find and activate the CD4 CELLS responsive to that antigen.

Antioxidant: a substance that prevents or reverses OXIDATION. Antioxidants are produced by the body and can be added to the diet (e.g., VITAMINS A, C and E).

Antiretroviral (ARV): a substance that stops or suppresses the activity of a RETROVIRUS, such as HIV. NUCLEOSIDE ANALOGS and PROTEASE INHIBITORS are examples of antiretroviral drugs.

Antisense Drug: a synthetic segment of DNA or RNA that locks onto a strand of DNA or RNA with a complementary sequence of NUCLEOTIDES. Antisense drugs are designed to block viral genetic instructions, marking them for destruction by cellular ENZYMES, in order to prevent the building of new VIRUS or the infection of new cells.

Antiviral: a substance that stops or suppresses the activity of a VIRUS, including a RETROVIRUS.

Antivirogram: a phenotypic resistance assay made by Virco (see PHENOTYPIC ASSAY).

Anxiolytic: a drug or substance that reduces anxiety.

APC: see ANTIGEN PRESENTING CELL.

Aphasia: the loss of ability to speak or understand speech.

Aphthous Ulcer: a painful sore in the mouth or esophagus of unknown cause with a deep eroded base. Aphthous ulcers are common in people with HIV and are treated with CORTICOSTEROIDS or THALIDOMIDE.

Apoptosis: cellular self-destruction that can be triggered by stimulation of particular CELL SURFACE RECEPTORS. It is a metabolic process driven by cellular ENZYMES in which the cell's CHROMOSOMES and then the cell itself breaks down into fragments. The IMMUNE SYSTEM can trigger apoptosis to eliminate unneeded cells.

ARC: see AIDS-RELATED COMPLEX.

Area Under the Curve (AUC): a measure of the total exposure of a drug or total effect of a treatment during a period of time. Defined by charting on a graph the changes in the critical variable over a period of time and then calculating the area between the curve and the horizontal axis (which represents elapsed time from the start of the study). Blood levels of drug and VIRAL LOAD during treatment are two parameters frequently quantified by the AUC. See also TIME-AVERAGED DIFFERENCE (DAVG).

Arm: one of the groups in a CLINICAL TRIAL.

Armamentarium: the collection of treatments available for a particular condition.

Arteriosclerosis: hardening of the arteries.

Arthralgia: joint pain.

ARV: See ANTIRETROVIRAL

As-Treated (AT) Analysis: a type of analysis of a CLINICAL TRIAL in which only the data from those patients who completed the study are included. Compare INTENT-TO-TREAT ANALYSIS.

Ascites: an accumulation of abdominal fluid due to low blood albumin, which is a potential complication from CIRRHOSIS.

Ascorbate: see ASCORBIC ACID.

Ascorbic Acid: an ANTIOXIDANT used to produce collagen (which is used for healing wounds) and strengthen connective tissues. It may also help immune function. Deficiency leads to scurvy. Also called ascorbate or VITAMIN C.

-ase: a suffix indicating that a substance is an ENZYME.

Aspartate Aminotransaminase: a liver ENZYME, like ALANINE AMINOTRANSAMINASE, that plays a role in PROTEIN METABOLISM. Elevated SERUM levels of AST are a sign of liver damage from disease or drugs. AST is also known as serum glutamic oxaloacetic transaminase (SGOT).

Aspergillus: a FUNGUS that infects the lungs, causing a disease known as aspergillosis. The infection can spread through the blood to other organs and cause lesions in the skin, ear, nasal sinuses and lungs, as well as occasionally in the bones, MENINGES, heart, kidneys or SPLEEN.

Assay: a test.

Association: a relationship that is more than would be expected by pure chance, but which is not necessarily causal.

AST: see ASPARTATE AMINOTRANSAMINASE.

Asthenia: weakness, debility.

Asymptomatic: without signs or symptoms of disease or illness.

Ataxia: lack of muscular coordination; a disorder of gait.

Atazanavir (Reyataz): an HIV PROTEASE INHIBITOR made by Bristol-Myers Squibb.

Atorvastatin (Lipitor): a LIPID-lowering drug.

Atovaquone (Mepron): an oral medication for mild to moderate cases of PNEUMOCYSTIS CARINII PNEUMONIA and, in some cases, TOXOPLASMOSIS. Atovaquone should be used with caution with RIFAMPIN, which can lower atovaquone blood levels.

Atrophy: a wasting or shrinking of cells, tissue, organs or muscle.

Attenuated Virus: a weakened VIRUS strain that can no longer infect or produce disease. An attenuated virus might potentially be used as a VACCINE.

Atypia: an abnormality in the cells of the cervix that can be discovered through a PAP SMEAR.

AUC: see AREA UNDER THE CURVE.

Autoimmune Disease: an ailment caused by an IMMUNE RESPONSE against an individual's own tissues or cells.

Autologous: referring to a naturally occurring substance derived from and used within the same individual. Compare ENDOGENOUS.

Average: the result of adding several quantities together and dividing the total by the number of quantities. For example, the average of 10, 20, and 60 is 30 (10 + 20 + 60 = 90 divided by 3 is 30). Also called the mean. Compare MEDIAN.

Azidothymidine: see ZIDOVUDINE.

Azithromycin (Zithromax): an ANTIBIOTIC approved for the prevention of MYCOBATERIUM AVIUM COMPLEX (MAC) as well as treatment of CHLAMYDIA and bacterial infections of the skin and respiratory tract. It may also have activity against TOXOPLASMOSIS and CRYPTOSPORIDIOSIS. SIDE EFFECTS include nausea, diarrhea, dizziness, sensitivity to sunlight and vaginal CANDIDIASIS.

Azole: a member of a class of antifungal drugs that includes FLUCONAZOLE and ITRACONAZOLE.

AZT: see ZIDOVUDINE.

B

B Cell (B Lymphocyte): a type of LYMPHOCYTE that is a precursor to PLASMA cells. During infections, individual B cell clones multiply and are transformed into plasma cells, which produce large amounts of ANTIBODIES against a particular ANTIGEN on a foreign MICROBE. This transformation mainly occurs through interaction with the appropriate CD4 CELLS.

B Lymphocyte: see B CELL.

Bacteremia: the presence of BACTERIA in the blood.

Bacteria (singular: Bacterium): single-celled organisms belonging to a primitive group of living things characterized by a lack of certain cellular components found in more advanced organisms.

Bacterial Vaginosis: a bacterial infection of the vagina.

Bactrim: see TRIMETHOPRIM/SULFAMETHOXAZOLE.

Base Pairing: during genetic replication, the process where nucleic acid bases pair with their complements (ADENINE pairs with THYMINE or URACIL and CYTOSINE pairs with GUANINE).

Baseline: the initial time point in a CLINICAL TRIAL or treatment REGIMEN, just before someone starts to receive the treatment in question. At this reference point, measurable values such as CD4 CELL COUNT and VIRAL LOAD are recorded so they can be compared to later results. Safety and EFFICACY of a drug are often determined by monitoring changes from the baseline values.

bDNA Assay: see BRANCHED DNA ASSAY.

Benzodiazepine: a class of psychoactive drugs used to treat anxiety, insomnia or pain. Examples include alprazolam (Xanax), diazepam (Valium) and clonazepam (Klonopin).

Beta Carotene: a compound that is converted to VITAMIN A in the body. Beta carotene is a red-orange pigment found in dark green and yellow fruits and vegetables. It is a nontoxic source of vitamin A.

Beta-2 Microglobulin: a PROTEIN of the IMMUNE SYSTEM found in the blood. Elevated blood levels of this protein are associated with immune activation and are weakly predictive of worsening of HIV infection.

BIA: see BIOELECTRICAL IMPEDANCE ANALYSIS.

Biaxin: see CLARITHROMYCIN.

Bicyclam: a class of compounds that affect HIV's ability to bind to healthy cells. (See FUSION INHIBITOR.)

BID: abbreviation for bis in die, a Latin phrase meaning twice a day. A drug prescribed this way should be taken every twelve hours.

Bile: a fluid secreted from the liver into the small intestine.

Bile Duct: a tract connecting the liver and small intestine through which BILE flows.

Bilirubin: a red pigment occurring in liver BILE, blood and urine. Bilirubin is the product of the breakdown of HEMOGLOBINin red blood cells. It is removed from the blood and processed by the liver, which secretes it into the digestive tract via the bile. An elevated level in blood SERUM can be an indication of liver disease, drug-induced liver impairment or hemolysis (breakdown of red blood cells). An increase in the unconjugated form of bilirubin is a side effect of the HIV PROTEASE INHIBITOR, ATAZANAVIR, and is considered non-toxic.

Binding Site: an area where two protein molecules join together. For example, CYTOKINES bind to CELL SURFACE RECEPTORS and the GP120 PROTEIN of HIV binds to the CD4 CELL SURFACE RECEPTOR.

Bioavailability: the extent to which an oral medication is absorbed in the digestive tract and reaches the bloodstream.

Bioelectrical Impedance Analysis (BIA): a technique for indirectly measuring body fat, BODY CELL MASS, extracellular mass and extracellular fluid. Not as accurate as other measurements, it has been used to monitor changes in body composition in people with HIV.

Biopsy: the removal of a small piece of tissue either surgically or with a small aspiration needle so it can be microscopically examined to determine the type or extent of a particular disease.

Bitter Melon (MAP-30): the fruit of a Chinese vine related to the cucumber. MAP-30, which has shown some anti-HIV activity in the test tube, can be extracted from bitter melon. Little information about EFFICACY or proper use is available.

Bleomycin: a drug used to treat cancer that interferes with the reproduction of cancerous cells. Bleomycin is used as a treatment for KAPOSI'S SARCOMA (KS).

Blinded: a term used to describe a CONTROLLED TRIAL where the participants do not know which ARM of the trial they are in and precisely which study treatment they are receiving. If researchers do not know either, the trial is DOUBLE-BLINDED.

Blood-Brain Barrier: the protective barrier that restricts the passage of many substances from the blood to the tissues of the brain. Not all drugs can cross this barrier.

Blood-Brain Penetration: the ability of a drug or other substance to cross the BLOOD-BRAIN BARRIER.

Blood Plasma: see PLASMA.

Blood-Retina Barrier: the barrier that prevents the passage of most substances from the blood to the RETINA, making it difficult to treat eye disease with systematically administered medicines, e.g., pills and intravenous infusions.

Blood Sugar: GLUCOSE in the blood.

Bloodwork: various laboratory tests that analyze characteristics of the blood.

BLQ: see BELOW THE LIMIT OF QUANTIFICATION.

BMI: see BODY MASS INDEX.

Bodily Fluids: refers to liquids naturally produced by the body such as urine, saliva and tears. The only bodily fluids having a high risk for transmission of HIV are blood, semen, vaginal secretions and breast milk.

Body Cell Mass: consists of cells in the muscles and organs, as well as circulating cells. The body cell mass consumes oxygen and produces carbon dioxide, and it is the compartment where all metabolic activity occurs.

Body Composition: what makes up the body, e.g., fat, LEAN BODY MASS, water. Abnormal changes in body composition with fat redistribution, generally referred to as LIPODYSTROPHY, have been noted in people on ANTIRETROVIRAL medications. See also WASTING SYNDROME.

Body Mass Index (BMI): an index used to relate a person's weight and height. The BMI is a person's weight in kilograms divided by height in meters squared. It correlates strongly with total body fat content in adults.

Bone Marrow: soft tissue located in the cavities of bones. It is the site of blood cell production.

Bone Marrow Suppression: a SIDE EFFECT of many anticancer and ANTIVIRAL drugs, including AZT (ZIDOVUDINE).

Bone marrow suppression may lead to a decrease in red blood cells (ANEMIA), white blood cells (LEUKOPENIA) or PLATELETS (THROMBOCYTOPENIA). Such reductions, respectively, result in fatigue and weakness, susceptibility to infections and spontaneous or excess bleeding.

Branched DNA (bDNA) Assay: a test developed by the Chiron Corporation for measuring the amount of HIV (as well as other VIRUSES) in blood PLASMA. The result of this test is also known as the VIRAL LOAD. The test uses a signal amplification technique, which creates a luminescent signal whose brightness depends on the amount of viral RNA present. Test results are calibrated in numbers of virus particle equivalents per milliliter of plasma (copies/ml). The bDNA test returns a result about half that of the POLYMERASE CHAIN REACTION (PCR) TEST, which uses a different technique.

Bronchitis: a disease marked by INFLAMMATION of the bronchial tubes in the lungs.

Bronchodilator: an inhalant that can reduce coughing, wheezing and shortness of breath.

Bronchoscopy: a diagnostic examination in which a fiber optic tube is inserted in the throat to enable a doctor to see the trachea and the lungs. Bronchoscopy is often used to detect PNEUMOCYSTIS CARINII PNEUMONIA (PCP).

Bronchospasm: a contraction of the muscle of the bronchi, often seen in asthma.

Buffalo Hump: see DORSAL FAT PAD

Buffered: refers to pills that include an antacid to neutralizing stomach acid, which may help reduce stomach upset or increase BIOAVAILABILITY of a drug.

Bupropion (Wellbutrin): an antidepressant that is a weak blocker of serotonin and norepinephrine. A lower dose formulation (Zyban) is used for cigarette smoking cessation. RITONAVIR may increase blood levels of bupropion, requiring a lower dose of the latter.

Burkitt's Lymphoma: a cancerous tumor, frequently involving jaw bones, ovaries and abdominal LYMPH NODES. The disease is common in Africa and has been associated with EPSTEIN-BARR VIRUS.

Buyers' Club: a nonprofit group formed to import AIDS-related therapies that are available in other countries but are not yet approved by the FDA for use in the United States. These products may be sold abroad for purposes that are not related to AIDS or HIV infection, and their use in HIV/AIDS remains speculative.

C

Cachexia: a general weight loss and wasting occurring in the course of a CHRONIC disease.

CAF: see CELL ANTIVIRAL FACTOR

Calanolide A: a compound derived from a latex tree that works as a NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR (NNRTI) and shows some anti-HIV activity. Manufactured by Sarawak MediChem Pharmaceuticals, it is currently in PHASE II CLINICAL TRIALS.

Canarypox Virus: a VIRUS that does not cause disease in humans and that is used in VACCINE research, including HIV vaccine research.

Cancer: any MALIGNANT growth.

Candida: a group of yeast-like FUNGI, in particular Candida albicans, that infect the mouth as well as other MUCOUS MEMBRANES in the esophagus, intestines, vagina, throat, skin and lungs. Oral or recurrent vaginal candida infection is an early sign of IMMUNE SYSTEM deterioration, diabetes or steroid use.

Candidiasis: an infection due to CANDIDA yeast. The symptoms of oral candidiasis (THRUSH) and vaginal candidiasis (formerly called monilia) include pain, itching, redness and white patches in their respective sites. Some common treatments are

CLOTRIMAZOLE, NYSTATIN and miconazole.

Canker Sore: see APHTHOUS ULCER.

Cannabinoids: components of cannabis, including TETRAHYDROCANNABINOL (THC) (see CANNABIS).

Cannabis: a plant that contains TETRAHYDROCANNABINOL (THC), an active ingredient in marijuana. Medical uses of cannabis, or THC, include stimulation of appetite and reduction of nausea.

Capravirine (AG 1549): an experimental NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR from Agouron.

Capsid: a part of some VIRUSES that surrounds their GENOME protecting it from the environment.

Carbohydrate: an ORGANIC MOLECULE made up solely of carbon, hydrogen and oxygen. Carbohydrates may be made up of only one or two components (mono- or di-saccharides, also called "sugars") or be complex chains of individual units (polysaccharides or "starches").

Carcinogen: a substance or agent that can cause the growth of cancer.

Carotenoids: a class of carotenes, such as BETA CAROTENE.

Carrisyn: see ACEMANNAN.

Case-Controlled Study: a RETROSPECTIVE STUDY that starts with the identification of people who have a disease or condition (the cases) and those who do not (the controls). Researchers then look for similarities and differences between the cases and controls regarding the factor or factors under investigation.

CAT Scan: see COMPUTED TOMOGRAPHY SCAN.

Catabolic: refers to metabolic processes that break down tissue in the body.

Catalase: a naturally occurring ANTIOXIDANT enzyme.

Category A (FDA): a drug for which adequate and well-controlled studies of pregnant women fail to demonstrate a risk to the fetus during pregnancy.

Category B (FDA): a drug for which animal reproduction studies fail to demonstrate a risk to the fetus although adequate and well-controlled studies have not been conducted.

Category C (FDA): a drug for which safety in human pregnancy has not been determined and animal studies are either positive for fetal risk or have not been conducted. Pregnant women should not use category C drugs unless the potential benefits outweigh the potential risk to the fetus.

Category D (FDA): a drug for which there is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experiences. In certain cases, the potential benefits from the use of this drug in pregnant women may be acceptable despite its potential risks.

Category X (FDA): a drug for which studies in animals or reports of adverse reactions in humans have indicated that the risk associated with its use clearly outweighs any possible benefit for a pregnant woman.

Catheter: a semi-permanent plastic or synthetic tube, usually implanted in the chest or arm for a long term, used for metered administration of a drug into the veins. See also HICKMAN CATHETER® - (HICKMAN is a registered trademark of C. R. Bard, Inc. and its related company, BCR, Inc.) and PERIPHERALLY INSERTED CENTRAL CATHETER (PICC) LINE.

CBC: see COMPLETE BLOOD COUNT.

CCR5: a seven-looped PROTEIN structure that normally occurs on the surface of certain IMMUNE SYSTEM cells and acts as a CHEMOKINE receptor site. After HIV binds to the cellular receptor CD4, the R5-using strain must then bind to CCR5 before the virus can enter the cell. People who lack CCR5 receptors seem to be very resistant to HIV infection and, if infected, have a slow progression to AIDS. Compare CXCR4.

CD4: one of the PROTEIN structures on the surface of a human cell that allows HIV to attach, enter, and thus infect the cell. CD4 molecules are present on CD4 CELLS (helper T lymphocytes), MACROPHAGES and DENDRITIC CELLS, among others. Normally, CD4 acts as an accessory molecule, forming part of larger structures (such as the T CELL RECEPTOR) through which T cells and other cells signal each other. In particular, it participates in the interaction between CD4 cells and the MAJOR HISTOCOMPATABILITY COMPLEX class II molecules on ANTIGEN PRESENTING CELLS.

CD4 Cell: a type of T lymphocyte involved in protecting against viral, fungal and protozoal infections. The CD4 cell modulates the IMMUNE RESPONSE to an infection through a complex series of interactions with ANTIGEN PRESENTING CELLS (MACROPHAGES, DENDRITIC CELLS and B CELLS) and those LYMPHOCYTES that directly attack foreign ANTIGENS (B cells, again, and CD8 CELLS). CD4 cells are the primary target of HIV, and it is mainly the destruction of CD4 cells that leads to the progression of HIV disease. CD4 cells are also called helper T cells.

CD4 Cell Count: the most commonly used SURROGATE MARKER for assessing the state of the IMMUNE SYSTEM. Also called T4 cell count. As CD4 cell count declines, the risk of developing OPPORTUNISTIC CONDITIONS increases. Normal CD4 cell counts are greater than 800 per cubic millimeter of blood. According to the CENTERS FOR DISEASE CONTROL, a CD4 cell count below 200 is an AIDS-defining condition.

CD4 Percent: the percentage of total LYMPHOCYTES made up by CD4 CELLS. A common measure of immune status, CD4 percent is about 40 percent in healthy individuals and can be below 20 percent in persons with AIDS.

CD4 Receptor: see CD4.

CD4/CD8 Ratio: the ratio of CD4 CELLS to CD8 CELLS. A common measure of IMMUNE SYSTEM status, the ratio is around 1.5 to 2.0 CD4 cells to 1.0 CD8 cell in healthy individuals and falls as CD4 CELL COUNTS fall in persons with HIV infection.

CD8 Cell: a type of T CELL that bears the RECEPTOR for CD8 on its surface. The CD8 receptor helps cells interact with the ANTIGEN-presenting MAJOR HISTOCOMPATABILITY COMPLEX class I molecules on other cells. Some CD8 cells -which are called CYTOTOXIC T LYMPHOCYTES - recognize and kill cancerous cells and those infected by intracellular PATHOGENS (some BACTERIA, VIRUSES and MYCOPLASMA). Other CD8 cells are known as suppressor cells.

CDC: see CENTERS FOR DISEASE CONTROL.

Cell Antiviral Factor (CAF): a so-far unidentified soluble substance that is secreted by activated CD8 CELLS and that inhibits HIV replication within cells. CAF activity seems to be high in LONG-TERM NONPROGRESSORS but low in patients who have rapid disease progression.

Cell Lines: specific cell types bred in the laboratory for use in scientific experimentation.

Cell-Mediated Immunity (CMI): one type of IMMUNE SYSTEM response, coordinated by Th1 cells, in which disease is controlled by specific defense cells (CYTOTOXIC T LYMPHOCYTES) that kill infected cells. See TH1 RESPONSE.

Cell Surface Receptor: a molecule on a cell's surface that binds with various substances, causing changes in the activity of the cell. See also RECEPTOR.

Centers for Disease Control and Prevention (CDC): the federal public health agency serving as the center for preventing, tracking, controlling and investigating the EPIDEMIOLOGY of AIDS and other diseases.

Central Nervous System (CNS): the brain, spinal cord and the protective membranes (MENINGES) surrounding them.

Cerebrospinal Fluid (CSF): fluid that bathes the brain and the spinal cord. A sample of this fluid is often removed from the body for diagnostic purposes by a LUMBAR PUNCTURE (spinal tap).

Cervical Dysplasia: changes in the lining cells of the CERVIX that may progress to cancer if not treated in time. It is caused by HUMAN PAPILLOMAVIRUS (HPV). Cervical dysplasia is detected through a PAP SMEAR.

Cervical Intraepithelial Neoplasia: see CERVICAL DYSPLASIA.

Cervicovaginal Lavage (CVL): a technique in which a saline solution is sprayed into the vaginal vault and recovered for testing.

CVL can be used to determine HIV VIRAL LOAD in genital tract secretions.

Cervix: the lower, cylindrical terminus of the uterus that juts into the vagina and contains a narrow canal connecting the upper and lower parts of a woman's reproductive tract.

Chancroid: a highly contagious sexually transmitted disease caused by the Hemophilus ducreyi BACTERIUM. It appears as a pimple, chancre, sore or ulcer on the skin of the genitals. The lesion arises after an incubation period of three to five days and may facilitate the transmission of HIV. Usually treated with ERYTHROMYCIN or ceftriaxone.

Chart Review: a retrospective way of collecting data that involves examining patients' medical records.

Chemokine: a soluble chemical messenger that attracts white blood cells to a site of infection. There are two structural categories of chemokines: alpha (CXC) and beta (CC). Examples of chemokines that interfere with HIV activity are the beta chemokines MACROPHAGE INFLAMMATORY PROTEIN-1a, MACROPHAGE INFLAMMATORY PROTEIN-1b, and RANTES (REGULATED-UPON-ACTIVATION, NORMAL T-EXPRESSED AND SECRETED) and the alpha chemokine STROMAL CELL-DERIVED FACTOR-1.

Chemotaxis: the migration of cells along a chemokine gradient toward its source; a response to the chemical stimulus of a chemoattractant.

Chemotherapy: the use of chemical agents (drugs) in the treatment of a disease. The term commonly, but not always, refers to cancer treatment.

Chlamydia (Chlamydia trachomatis): the most common sexually transmitted BACTERIUM infecting the reproductive system. The infection is frequently ASYMPTOMATIC, but, if left untreated, it can cause sterility in women.

Cholestasis: obstruction of BILE within the BILE DUCT.

Cholesterol: a STEROID found in the tissues and blood PLASMA. Cholesterol circulates in the blood along with a PROTEIN (LIPOPROTEIN). LOW-DENSITY LIPOPROTEINS (LDLs) take cholesterol from the liver to body tissues while HIGH-DENSITY LIPOPROTEINS (HDLs) take cholesterol from the blood to be excreted. High levels of LDLs and/or low levels of HDLs are associated with heart disease and ARTERIOSCLEROSIS.

Chromosome: the thread-like structures in the nucleus (center) of a cell that carry genetic information. Each chromosome contains a double strand of twisted DNA. Along each strand of DNA lie the GENES.

Chronic: refers to symptoms and diseases that last for an extended period of time without noticeable change.

Cidofovir (Vistide): a NUCLEOTIDE ANALOG. Cidofovir is approved as systemic treatment for new or relapsing CYTOMEGALOVIRUS (CMV) RETINITIS. Its primary advantage over GANCICLOVIR and FOSCARNET is that cidofovir is administered intravenously on a weekly or a biweekly basis instead of daily, eliminating the need for an in-dwelling CATHETER. The chief SIDE EFFECT of intravenous administration is kidney damage, which can be very severe. To protect the kidneys, cidofovir must be administered with PROBENECID and INTRAVENOUS hydration. Cidofovir should not be used at the same time as other drugs that are toxic to the kidneys or in patients with impaired kidney function. Cidofovir is being tested for activity against KAPOSI'S SARCOMA (KS) and PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY (PML).

Cimetidine (Tagamet): an antiulcer drug that blocks histamine, a substance secreted by MAST CELLS that causes the symptoms of allergy. Cimetidine has been proposed as an IMMUNE-BASED THERAPY for HIV infection.

Cipro: see CIPROFLOXACIN.

Ciprofloxacin (Cipro): an oral ANTIBIOTIC approved for the treatment of many common bacterial and urinary infections. It is sometimes administered to treat MYCOBACTERIUM AVIUM COMPLEX (MAC) in combination with other drugs. Possible SIDE EFFECTS include gastrointestinal upset, seizures and rash.

Cirrhosis: a liver disease that results in FIBROSIS and nodule formation. It can also cause gastrointestinal problems, JAUNDICE and EDEMA. Although irreversible and a common cause of death, cirrhosis can be controlled with VITAMINS, diuretics and beta blockers. Cirrhosis can be caused by alcoholism, HEPATITIS and an obstruction in BILE flow.

Clade: one of the major, largely geographically isolated, HIV subtypes. Classification is based on differences in ENVELOPE PROTEIN. Clade B makes up the overwhelming majority of HIV in North America and Europe.

Clarithromycin (Biaxin): an ANTIBIOTIC approved for the prevention and treatment of MYCOBACTERIUM AVIUM COMPLEX (MAC) and also used for preventing this disease in people with AIDS. SIDE EFFECTS include diarrhea, nausea and abnormal taste. Clarithromycin may cause severe abdominal pain at high doses.

Clearance: the removal of something, often from the blood (e.g., through the kidneys).

Cleocin: see CLINDAMYCIN.

Clindamycin (Cleocin): an approved ANTIBIOTIC that may be an alternative treatment for PNEUMOCYSTIS CARINII PNEUMONIA (PCP) and (usually with PYRIMETHAMINE) TOXOPLASMOSIS. The most common SIDE EFFECT is diarrhea, which is caused by an overgrowth of an intestinal BACTERIUM called Clostridium difficile during clindamycin therapy.

Clinical: refers to physical signs and symptoms directly observable in the human body.

Clinical Endpoint: a predefined outcome (e.g., clinical improvement) in a CLINICAL TRIAL that signals a study result for a particular patient.

Clinical Trial: a study done to test an EXPERIMENTAL DRUG or procedure in human beings to see whether it is safe and effective, as well as to determine its proper dose.

Clotrimazole (Lotrimin, Mycelex): an approved antifungal drug used as a TOPICAL agent for oral and vaginal CANDIDIASIS.

Cmax: the maximum concentration of a drug in the body after dosing. Cmax is often associated with SIDE EFFECTS. See also PEAK LEVEL.

CMI: see CELL-MEDIATED IMMUNITY.

Cmin: the lowest concentration of a drug after dosing. See also TROUGH LEVEL.

CMV: see CYTOMEGALOVIRUS.

CNS: see CENTRAL NERVOUS SYSTEM.

Coat: see ENVELOPE.

Codon: a three-NUCLEOTIDE genetic subunit that determines which AMINO ACID is placed in sequence in a PROTEIN

chain. Mutations at specific HIV codons are associated with changes in the amino acid sequence of HIV's proteins and ENZYMES. Such MUTATIONS help HIV evade the effects of ANTIVIRAL drugs or specific IMMUNE RESPONSES.

Coenzyme Q10 (CoQ10): a substance that assists in the OXIDATION of nutrients within cells to create energy. It is also highly efficient at protecting internal and external cell membranes against oxidation and is sometimes proposed as a COMPLEMENTARY MEDICINE to combat AIDS-related conditions.

Cofactor: any agent or characteristic that enhances or activates disease progression.

Coformulation: the packaging of more than one drug into a single pill.

Cohort: a group of individuals with some characteristics in common that is the subject of a study of the EPIDEMIOLOGY or natural course of a disease.

Colitis: INFLAMMATION of the colon, a condition that causes abdominal pain and diarrhea.

Colony-Stimulating Factor (CSF): a PROTEIN found in SERUM that promotes differentiation of MONOCYTES. See GRANULOCYTE COLONY STIMULATING FACTOR (G-CSF) and GRANULOCYTE-MACROPHAGE COLONY STIMULATING FACTOR (GM-CSF).

Colposcopy: a procedure in which the surface of the uterine CERVIX is examined through a low-powered microscope for signs of CERVICAL DYSPLASIA or cancer. Colposcopy is a more accurate alternative to PAP SMEARS, but requires considerably more skill to perform.

Combination Therapy: using at least two drugs simultaneously to more effectively combat a disease. See HIGHLY ACTIVE ANTIRETROVIRAL THERAPY (HAART).

Combivir: The GlaxoSmithKline trade name for a pill that contains both ZIDOVUDINE (AZT) and LAMIVUDINE (3TC).

Community Programs for Clinical Research on AIDS (CPCRA): a branch of the NATIONAL INSTITUTES OF HEALTH'S Division of AIDS that supports CLINICAL TRIALS based on local networks of practicing physicians. These physicians collect data on their patients who are participating in a treatment trial.

Comorbidity: the coexistence of two or more diseases or conditions.

Compassionate Use: a process for providing EXPERIMENTAL DRUGS on an individual basis to very sick patients who have no treatment options, despite the fact that there is no sufficient data on the drug's effectiveness. Often, case-by-case approval must be obtained from the FDA for compassionate use of a drug. See also EXPANDED ACCESS PROGRAM, PARALLEL TRACK and TREATMENT INVESTIGATIONAL NEW DRUG.

Compazine: see PROCHLORPERAZINE.

Complementary Medicine: health care provided in addition to, or instead of, standard medical practice. See also ALTERNATIVE MEDICINE.

Complete Blood Count (CBC): a screening of the most important cellular components of the blood. A CBC includes the total white blood (LEUKOCYTE) count, counts of specific types of white blood cells, red blood cell count, HEMOGLOBIN level and PLATELET count.

Compliance: see ADHERENCE.

Compound Q (GLQ223): an extract of a Chinese wild cucumber. It is used in China to induce abortions and treat respiratory viruses. In this country, compound Q has been tested and used in the community as an anti-HIV treatment, but is now largely out of favor. Possible SIDE EFFECTS of this INTRAVENOUS medication include anaphylactic reactions (see ANAPHYLAXIS) and seizures.

Computed Tomography Scan (CT Scan): a form of x-ray examination that utilizes a special beam to produce a detailed series of images of body sections. A CT scan is also referred to as a CAT (computed axial tomography) scan.

Consensus interferon (CIFN): a novel, recombinant type 1 intereron containing 166 amino acids. CIFN was derived by scanning the sequences of several natural alpha interferons and assigning the most frequently observed amino acid in each corresponding position. CIFN, when compared on an equal mass basis with interferon (IFN) alfa-2a and alfa-2b in in vitro assays, typically displays 5-10 times higher biological activity.

Condyloma Acuminatum: a projecting warty growth on the external genitals or the anus caused by infection with the HUMAN PAPILLOMAVIRUS (HPV). It is usually a benign or non-cancerous growth. Condyloma acuminatum is also referred to as genital warts or verruca acuminata.

Confide: see HOME-BASED HIV TESTING KITS.

Confounding Factor: a variable that differs between the treatment and control groups in a study that could affect the results.

Conjunctivitis: an INFLAMMATION of the conjunctiva, which constitutes the thin protective membrane on the inner surface of the eyelids.

Contraindication: a condition or circumstance that prevents prescribing a certain treatment to an individual patient.

Control Arm: the group of participants in a CLINICAL TRIAL that receives a standard treatment and/or a PLACEBO. Those receiving the experimental treatment are compared to the control arm.

Controlled Trial: a clinical study in which one group of participants receives an EXPERIMENTAL DRUG while another group receives either a PLACEBO or an approved standard therapy. When participants do not know which group they are in, the trial is BLINDED. When the researchers are kept from knowing, too, then the trial is DOUBLE-BLINDED.

CoQ10: see COENZYME Q10.

Correlation: the statistical strength of association between two variables.

Cortex: the outer portion of an organ.

Corticosteroid: any STEROID HORMONE obtained from the CORTEX or outer portion of the ADRENAL GLAND or any synthetic substitute for such a steroid. Corticosteroids are immunosuppressive and include prednisone, corticosterone, cortisone and aldosterone.

Cortisol: a naturally occurring STEROID, secreted by the ADRENAL GLAND that affects the METABOLISM of GLUCOSE, PROTEINS and fat.

CPCRA: see COMMUNITY PROGRAMS FOR CLINICAL RESEARCH ON AIDS.

Creatinine: the product of the breakdown of creatine, an important molecule involved in energy transfer within muscle cells. The level of creatinine in the blood and urine provides a measure of kidney function.

Crix Belly: the accumulation of fat in the lower abdomen. So-called because it was first noted in association with Crixivan (INDINAVIR), although other ANTIRETROVIRALS or HIV disease itself could also be involved. See LIPODYSTROPHY.

Crixivan: see INDINAVIR.

Cross-Resistance: the phenomenon in which a MICROBE that has acquired RESISTANCE to one drug to which it has not been exposed through direct exposure to one or more other drugs. Cross-resistance arises because the site of activity of several drugs is the same, resulting in identical genetic resistance MUTATIONS.

Cross-Sectional Study: a study that examines and analyses predefined variables at a fixed time or over a short period, as opposed to a LONGITUDINAL STUDY that observes patients over time.

Cryotherapy: the use of liquid nitrogen to freeze and destroy a lesion or growth, sometimes used to induce scar formation and healing to prevent further spread of a condition (for example, warts or MOLLUSCUM CONTAGIOSUM).

Cryptococcal Meningitis: an OPPORTUNISTIC CONDITION caused by the FUNGUS Cryptococcus neoformans and involving the membranes surrounding the brain and spinal cord. Symptoms may include severe headache, confusion, sensitivity to light, blurred vision, fever and speech difficulties. Left untreated, the disease can lead to coma and death. Standard treatments are AMPHOTERICIN B (as INDUCTION THERAPY) and FLUCONAZOLE (as MAINTENANCE THERAPY).

Cryptococcus: a FUNGUS that is usually harmless, but can cause MENINGITIS in people with AIDS. It is found in pigeon droppings.

Cryptosporidiosis: an OPPORTUNISTIC CONDITION caused by the intestinal parasite Cryptosporidium parvum, a very common parasite in animals. Transmission occurs through ingestion of food or water contaminated with animal feces (this can include tap water, some bottled waters and water from lakes and ponds). The parasite grows in the intestines and BILE DUCTS and causes severe, CHRONIC diarrhea, especially in people with AIDS. There are no standard treatments, but HIGHLY ACTIVE ANTIRETROVIRAL THERAPY (HAART) and PAROMOMYCIN can be effective.

CSF: see CEREBROSPINAL FLUID or COLONY-STIMULATING FACTOR.

CT Scan: see COMPUTED TOMOGRAPHY SCAN.

CTL: see CYTOTOXIC T LYMPOCYTE.

Culture: the process of growing BACTERIA or other cells in a special laboratory medium.

Curcumin: an ingredient of the spice turmeric. Laboratory studies have suggested that curcumin inhibits HIV replication by blocking the LONG TERMINAL REPEAT region on HIV's GENES, but a 1996 CLINICAL TRIAL found no ANTIVIRAL effect.

Cutaneous: relating to the skin.

CVL: see CERVICOVAGINAL LAVAGE.

CXCR4: a seven-looped PROTEIN structure that normally occurs on the surface of certain IMMUNE SYSTEM cells and acts as a CHEMOKINE receptor site. After HIV binds to the cellular receptor CD4, the X4-using strain must then bind to CXCR4 before the virus can enter the cell. Compare CCR5.

Cyclobut G: see LOBUCAVIR.

CYP: see CYTOCHROME P450.

Cysteine: an AMINO ACID.

Cytidine: a NUCLEOSIDE of CYTOSINE. LAMIVUDINE (3TC) and DIDEOXYCYTIDINE (ddC) are analogs of cytidine.

Cytochrome P450 (CYP): a family of ENZYMES in the liver that metabolizes drugs and other fat-soluble substances. Certain medications, e.g., RITONAVIR, inhibit some of the P450 enzymes, in particular P450 3A4 (also called CYP3A4), affecting the liver's ability to break down other drugs. Inhibiting this enzyme will increase blood levels of medications that it normally metabolizes and dose adjustments may be necessary in order to prevent SIDE EFFECTS or overdosing. Conversely, NEVIRAPINE and EFAVIRENZ are examples of drugs that stimulate CYP3A4 causing reduced blood levels of drugs metabolized by the enzyme.

Cytokine: one of the PROTEINS produced by white blood cells (LEUKOCYTES) that act as chemical messengers between cells. Cytokines can stimulate or inhibit the growth and activity of various immune cells. Examples of cytokines are the various INTERLEUKINS and TUMOR NECROSIS FACTOR ALPHA.

Cytomegalovirus (CMV): a HERPES VIRUS infection that causes serious illness in people with AIDS. CMV can develop in any part of the body but most often appears in the RETINA of the eye, the nervous system, the colon or the esophagus.

Cytomegalovirus (CMV) Polyradiculopathy: CMV infection of the spinal roots (the bundles of nerves coming out of the spinal cord), leading to generalized weakness and paralysis.

Cytomegalovirus (CMV) Retinitis: CMV infection of the RETINA. The lesions it causes lead to deterioration in vision and ultimately blindness if untreated.

Cytosine: one of the four bases that makes up RNA (which also includes ADENINE, GUANINE and URACIL) and DNA (which also includes adenine, guanine and THYMINE). See also CYTIDINE.

Cytostatic: able to stop the growth of cells.

Cytotoxic: able to kill cells.

Cytotoxic T Lymphocyte (CTL): a type of CD8 or, less often, CD4 lymphocyte that kills diseased cells infected by a specific VIRUS or other intracellular MICROBE. CTLs interact with ANTIGEN bearing MAJOR HISTOCOMPATIBILITY COMPLEX (MHC) class I molecules on infected cells and have the prime role in CELL-MEDIATED IMMUNITY.

Cytovene: see GANCICLOVIR.

D

d4T: see STAVUDINE.

dAPD: see AMDOXOVIR

Dapsone: an antileprosy drug used in the treatment and prophylaxis of PNEUMOCYSTIS CARINII PNEUMONIA (PCP) and other diseases. Possible SIDE EFFECTS include skin rash, fever, gastrointestinal upset and destruction of red blood cells. Patients should avoid taking dapsone with buffered DIDANOSINE (ddI) or take it two hours before taking buffered ddI since the buffer reduces intestinal absorption of dapsone.

Daraprim: see PYRIMETHAMINE.

Data and Safety Monitoring Board (DSMB): an independent panel of clinical research experts responsible for the ongoing review and, when necessary, modification or termination of a CLINICAL TRIAL to insure the safety of participants.

Daunorubicin: a drug used to treat leukemia and a BONE MARROW suppressant. See also DAUNOXOME.

DaunoXome: a CYTOTOXIC CHEMOTHERAPY approved for FIRST-LINE TREATMENT for advanced KAPOSI'S SARCOMA. It consists of a preparation of DAUNORUBICIN encapsulated in LIPOSOMES, which increases the drug's stability while moderating its TOXICITIES. DaunoXome's main SIDE EFFECT is NEUTROPENIA, which can be managed with GRANULOCYTE COLONY STIMULATING FACTOR (G-CSF, Neupogen).

DAVG: see TIME-AVERAGED DIFFERENCE.

ddC: see DIDEOXYCYTIDINE.

ddI: see DIDANOSINE.

"d" drug: any of the NUCLEOSIDE ANALOGS ddI, d4T or ddC.

Deca Durabolin: see NANDRALONE DECANOATE.

Dehydroepiandrosterone (DHEA): a HORMONE produced by the ADRENAL GLAND. Levels of DHEA are often low in people with HIV. Its biological role in the body is unclear. Some of it is converted into TESTOSTERONE and other androgenic STEROIDS. There have been anecdotal reports of the benefits of DHEA for a variety of conditions, but there is little hard evidence to support these claims. DHEA is readily available through BUYERS' CLUBS and health food stores.

Delavirdine (Rescriptor): a NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR (NNRTI) from Agouron/Pfizer. SIDE EFFECTS include temporary skin rash in 20 percent of patients and, less frequently, nausea, headache, fatigue and diarrhea.

Delayed-Type Hypersensitivity (DTH): a cell-mediated immune reaction (see CELL-MEDIATED IMMUNITY) to certain foreign ANTIGENS applied on the surface or just under the skin. The reaction, consisting of a red bump or induration (hardening), takes 24 to 48 hours to develop. DTH, which is the process involved in the reaction to poison ivy and poison oak as well as to the TUBERCULOSIS skin test, is often used in tests of IMMUNE SYSTEM competence.

Dementia: see AIDS DEMENTIA COMPLEX.

Demographics: the statistical characteristics (e.g., age, income, vital statistics) of human populations.

Dendritic Cells: immune cells with long, tentacle-like branches called dendrites. Among the dendritic cells are the

LANGERHANS CELLS of the skin and FOLLICULAR DENDRITIC CELLS in the LYMPH NODES. Most dendritic cells (other than follicular dendritic cells) function as ANTIGEN PRESENTING CELLS.

Deoxyribonucleic Acid (DNA): a double-stranded molecule that makes up the CHROMOSOMES in the center of a cell and that carries genetic information in the form of GENES. The genetic code utilized by DNA resides in the varying sequences of the four NUCLEOTIDE bases: ADENINE, GUANINE, THYMINE and CYTOSINE.

Depression: a CHRONIC or recurrent mental state characterized by hopelessness and lack of motivation and energy. Other major symptoms include loss of appetite and either excessive or inadequate sleep.

Dermatitis: INFLAMMATION of the skin.

Desensitization: gradually increasing the dose of a medicine in order to overcome potentially severe allergic reactions.

Desensitization procedures are sometimes used when administering TRIMETHOPRIM/SULFAMETHOXAZOLE (Bactrim) for the first time to avoid a fever or skin reaction.

DEXA: see DUAL-ENERGY X-RAY ABSORBTIOMETRY.

DHEA: see DEHYDROEPIANDROSTERONE.

Dialysis: the separation of smaller molecules from larger molecules. Hemodialysis is a purification of the blood of persons whose kidneys no longer function.

Didanosine (ddI, Videx): a NUCLEOSIDE ANALOG from Bristol-Myers Squibb that inhibits infection of new cells by HIV. SIDE EFFECTS can include nerve damage in the hands and feet (PERIPHERAL NEUROPATHY) and damage to the pancreas (PANCREATITIS). Using ddI in combination with other drugs (including alcohol and DIDEOXYCYTIDINE [ddC]) can increase the risk of side effects. ddI must be taken on an empty stomach.

Dideoxycytidine (ddC, Zalcitabine, Hivid): a NUCLEOSIDE ANALOG from Hoffman La-Roche that inhibits infection of new cells by HIV. Possible SIDE EFFECTS include nerve damage in the hands and feet (PERIPHERAL NEUROPATHY) and sores in the mouth. The combination of ddI (DIDANOSINE) and ddC significantly increases the risk of peripheral neuropathy.

Didox: a RIBONUCLEOTIDE REDUCTASE inhibitor, similar to HYDROXYUREA.

Diflucan: see FLUCONAZOLE.

Distal: further from the center of the body or from a central reference point.

DNA: see DEOXYRIBONUCLEIC ACID.

Dorsal: relating to or located on or near the back.

Dorsal Fat Pad (Buffalo Hump): an enlargement at the lower, back-of-the-neck and shoulder region consisting of fat tissue. A form of fat redistribution associated with the use of ANTIRETROVIRALS. While it can be uncomfortable and unappealing, a dorsal fat pad is not a serious condition. Sometimes surgery or LIPOSUCTION can successfully remove a fat pad.

Dose-Escalating: describes a preliminary CLINICAL TRIAL in which the amount of a drug is either periodically increased or increased with each new trial ARM that is added. Used to determine how well a drug is tolerated in people and what its optimum dose might be, given the observed balance between ACTIVITY and SIDE EFFECTS.

Dose-Ranging: see DOSE-ESCALATING.

Double-Blinded: denotes a CLINICAL TRIAL in which neither the participants nor the doctors know who is receiving the EXPERIMENTAL DRUG and who is receiving the PLACEBO or standard comparison treatments. This method is believed to achieve the most accurate, generalizable results because neither the doctors nor the patients can affect the observed results with their psychological biases.

Down-Regulation: a reduction in the rate at which something happens.

Doxil (DOX-SL): a CYTOTOXIC CHEMOTHERAPY approved for KAPOSI'S SARCOMA (KS) consisting of a preparation of DOXORUBICIN encapsulated in LIPOSOMES which deliver significantly greater quantities of doxorubicin to the KS lesions while reducing the drug's SIDE EFFECTS. Side effects include nausea, vomiting, STOMATITIS, diarrhea and hair loss. Doxil causes a significant amount of NEUTROPENIA, which can be managed with GRANULOCYTE COLONY STIMULATING FACTOR (G-CSF).

Doxorubicin (Adriamycin): an INTRAVENOUS drug used in CHEMOTHERAPY for the treatment of cancer.

DOX-SL: see DOXIL.

Dronabinol (Marinol): a drug containing synthetic tetrahydrocannabinol (THC), the psychoactive ingredient in CANNABIS. It is used to stimulate appetite and reduce nausea and vomiting from CHEMOTHERAPY.

Drug-Drug Interaction: the effects that may occur when two or more drugs are used together. Such effects include changes of absorption in the digestive tract, changes in rate of the drugs' breakdown in the liver, new or enhanced SIDE EFFECTS and changes in the drugs' ACTIVITY.

Drug Holiday: an intentional, temporary suspension of drug therapy. This term is now generally distinguished from a STRUCTURED TREATMENT INTERRUPTION.

Drug Resistance: see RESISTANCE.

Drug Resistance Assay: a test used to help determine whether a virus, like HIV, is susceptible to certain drugs. See also RESISTANCE, GENOTYPIC ASSAY, PHENOTYPIC ASSAY.

Drug Resistance Mutation: a MUTATION in a PATHOGEN's genetic makeup that confers RESISTANCE to one or more drugs.

DSMB: see DATA AND SAFETY MONITORING BOARD.

DTH: see DELAYED-TYPE HYPERSENSITIVITY.

Dual-Energy X-Ray Absorbtiometry (DEXA): a type of body scan that creates a computer-generated image of the body. It is used to assess bone status and fat distribution.

Dyspepsia: digestive upset, which may include flatulence, heartburn, nausea or vomiting.

Dysphagia: difficulty in swallowing.

Dysplasia: abnormal changes or growth of cells and tissues. See CERVICAL DYSPLASIA.

Dyspnea: shortness of breath or difficulty in breathing.

Dysthymia: a mood disorder.

E

Early Access Program: see EXPANDED ACCESS PROGRAM.

EBV: see EPSTEIN-BARR VIRUS.

Echinacea: a commonly used herb for maintaining the IMMUNE SYSTEM. Little CLINICAL TRIAL data are available on the herb's value, if any, in HIV and AIDS.

Edema: swelling caused by an abnormal accumulation of fluid in body tissues.

Efavirenz (Sustiva, Stocrin): a NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR (NNRTI) from Bristol-Myers Squibb. Common SIDE EFFECTS include dizziness, insomnia, drowsiness, trouble concentrating, unusual dreams, rash, diarrhea and vomiting.

Effectiveness: the actual outcome produced by a drug for patients over time; considers "real world" factors such as tolerability in addition to EFFICACY.

Efficacy: strength or potency. The ability of a drug to control or cure an illness. Efficacy should be distinguished from ACTIVITY, which is limited to a drug's immediate effects on the MICROBE triggering the disease and from EFFECTIVENESS, which is considers it's use under "real world" conditions.

Elavil: see AMITRIPTYLINE.

Electrolytes: compounds that divide into electrically charged subunits (ions) when dissolved in water. Movement of these ions creates an electrical current. Electrolytes are found in varying amounts in blood PLASMA, tissues and cell fluids. The body must have the correct amount of the main electrolytes, including calcium, potassium and sodium, to maintain proper amounts of intracellular water, conduct nerve signals and allow for proper cellular response to CYTOKINES and other outside stimuli. Electrolyte solutions may be used as treatment to replenish fluids and electrolytes during episodes of dehydration.

Eligibility Criteria: see INCLUSION CRITERIA.

ELISA: see ENZYME-LINKED IMMUNOSORBENT ASSAY.

Emtricitabine (FTC): an experimental NUCLEOSIDE ANALOG from Gilead Sciences.

Encephalitis: a brain INFLAMMATION of viral or other microbial origin. Symptoms include headaches, neck pain, fever, nausea, vomiting and nervous system problems. Several types of OPPORTUNISTIC CONDITIONS can cause encephalitis.

Encephalopathy: a progressive, degenerative brain disease.

Endemic: widespread incidence of a particular disease in a certain population or region.

Endocarditis: a bacterial infection, most commonly caused by Staphylococcus aureus, that leads to INFLAMMATION of the heart valves. Endocarditis has been associated with INTRAVENOUS drug use. Although potentially fatal if untreated, it can be treated with ANTIBIOTICS.

Endocervix: the lining of the cervical canal.

Endocrine: 1. A HORMONE. 2. Pertaining to internal secretions.

Endocrine Gland: one of the organs in the body that produces HORMONES.

Endogenous: originating within the organism in question.

Endometrium: the MUCOUS MEMBRANE that lines the uterus.

Endothelium: a layer of flat cells that line the cavities of the heart and its blood and LYMPHATIC VESSELS.

Endpoint: a category of data used to compare the outcome between different ARMS of a CLINICAL TRIAL, it is the treatment effect of interest. Common endpoints are disease progression, death or alterations in such SURROGATE MARKERS as CD4 CELL COUNT or viral load. See also CLINICAL ENDPOINT.

Enfuvirtide (T-20, Fuzeon, Pentafuside): an approved FUSION INHIBITOR from Trimeris / Roche. It is administered as a SUBCUTANEOUS injection. Common SIDE EFFECTS include irritation at the injection site, fever and headache.

Enrollment Criteria: see INCLUSION CRITERIA.

Enteral: within or through the intestines.

Enteric: pertaining to the intestines.

Enteric Coating: a protective coating on a pill that allows its medication to remain undissolved until it has reached the small intestine.

Env Gene: the GENE in HIV that encodes information allowing the production of the GP160 ENVELOPE POLYPROTEIN, which later becomes the GP120 and GP41envelope PROTEINS.

Envelope: the outer covering of a VIRUS, sometimes called the coat.

Enzyme: a PROTEIN that acts as a catalyst.

Enzyme-Linked Immunosorbent Assay (ELISA): the most common test used to detect the presence of HIV ANTIBODIES in the blood, which indicate exposure to HIV. A positive ELISA test result must be confirmed by another test called a WESTERN BLOT.

Eosinophil: a type of GRANULOCYTE thought to play a role in fighting parasites and in producing allergic reactions. Its name comes from these cells'absorption of the red dye eosin.

Eosinophillic Folliculitis: an inflammatory reaction around hair follicles, characterized by very itchy PAPULES that may grow together to form plaques. The cause of this condition in people with AIDS has yet to be established, although the condition obviously involves invasion of the follicles by EOSINOPHILS. Partially successful treatment has been reported with ultraviolet light, STEROIDS, antihistamines and ITRACONAZOLE.

Epidemiology: the branch of medical science that studies the incidence, distribution and control of disease in a population.

Epithelial: refers to the cell linings covering most internal and external surfaces of the body and its organs.

Epitope: a unique molecular shape or AMINO ACID sequence carried on a microorganism that triggers a specific ANTIBODY or cellular IMMUNE RESPONSE.

Epivir: see LAMIVUDINE.

Epogen: a RECOMBINANT version of ERYTHROPOIETIN, a natural GLYCOPROTEIN that stimulates red blood cell production. Epogen is used as a treatment for drug-related ANEMIA, including that caused by ZIDOVUDINE (AZT). Epogen is made by Amgen. An identical product, known as Procrit, is made by Ortho Biotech.

Epstein-Barr Virus (EBV): a herpes-like virus that causes one of the two kinds of MONONUCLEOSIS (the other is caused by CYTOMEGALOVIRUS). It infects the nose and throat and is contagious. EBV lies dormant in the LYMPH NODES and has been associated with BURKITT'S LYMPHOMA and ORAL HAIRY LEUKOPLAKIA.

Erythrocyte: a red blood cell that carries oxygen throughout the body.

Erythrocytopenia: a low count of ERYTHROCYTES.

Erythromycin: an ANTIBIOTIC, often used to treat people who are allergic to penicillin or to treat penicillin-resistant infections.

Erythropoietin: a natural GLYCOPROTEIN that stimulates red blood cell production. See EPOGEN.

Estrogen: female sex HORMONES, either natural or synthetic.

Ethambutal (Myambutal): an ANTIBIOTIC used in COMBINATION THERAPY for treatment of mycobacterial infections such as TUBERCULOSIS and MYCOBACTERIUM AVIUM COMPLEX (MAC).

Etiology: the study of the causes or origin of disease.

Excipient: an inactive, soluble binding agent for incorporating an active drug into a pill.

Exclusion Criteria: criteria that are used to exclude certain people from CLINICAL TRIALS, often established for safety reasons. Some common exclusion criteria include pregnancy or the presence of OPPORTUNISTIC CONDITIONS.

Exogenous: originating outside the organism in question.

Expanded Access Program: refers to any of the FDA procedures (including COMPASSIONATE USE, PARALLEL TRACK and TREATMENT INVESTIGATIONAL NEW DRUG) that distributes EXPERIMENTAL DRUGS to patients who are failing on currently available treatments and also are unable to participate in ongoing CLINICAL TRIALS.

Experimental Drug: a drug that has not been approved by the FDA to treat a particular condition.

Extra-Ocular: outside of the eyes.

F

Famciclovir (Famvir): a PRODRUG for an ACYCLOVIR-like active compound. It has especially high BIOAVAILABILITY and is an approved therapy for SHINGLES and recurrent outbreaks of herpes simplex-2 (see HERPES VIRUS). SIDE EFFECTS are relatively infrequent but can include headache, nausea and fatigue.

Famvir: see FAMCICLOVIR.

Fanconi's Syndrome: dysfunction of the RENAL tubules whereby AMINO ACIDS, PROTEIN and GLUCOSE occur in the urine. Fanconi-like SYNDROME has been noted in people taking high doses of ADEFOVIR.

Fat Redistribution: see LIPODYSTROPHY.

FDA: see FOOD AND DRUG ADMINISTRATION.

FDC: see FOLLICULAR DENDRITIC CELL.

Fenofibrate: a drug used to lower blood LIPID levels.

Fibrosis: internal scarring.

First-Line Treatment: the optimal starting therapy for a TREATMENT-NAIVE patient. Due to the potential for the development of CROSS-RESISTANCE by HIV and other MICROBES, the choice of first-line medication(s) will affect the EFFICACY of succeeding (second-line) therapies.

Flagyl: see METRONIDAZOLE.

Floaters: drifting dark spots within the field of vision. Floaters can be caused by CYTOMEGALOVIRUS (CMV) RETINITIS, but also can appear in persons as a normal part of the aging process.

Fluconazole (Diflucan): an antifungal drug that is FDA-approved for treating and preventing CANDIDIASIS in the vagina, mouth, esophagus and other parts of the body. It is also approved for treating CRYPTOCOCCAL MENINGITIS and in this case is usually administered following two weeks of AMPHOTERICIN B. Possible SIDE EFFECTS include liver injury, ANAPHYLAXIS and skin peeling.

Flucytosine (5-FC, Ancobon): an antifungal drug that is indicated for the treatment of REFRACTORY fungal infections caused by CANDIDA and CRYPTOCOCCUS. In HIV-positive individuals, flucytosine is also used in combination with AMPHOTERICIN B or FLUCONAZOLE for treatment of CRYPTOCOCCAL MENINGITIS. Possible SIDE EFFECTS include liver damage.

Fluoxetine (Prozac): an antidepressant.

Fluvastatin: a drug used to lower blood CHOLESTEROL levels.

Fold Resistance: the number of times a drug's concentration needs to be multiplied in order to inhibit viral replication as compared to a REFERENCE VIRUS. For example, if it takes four times as much of a particular drug to inhibit viral replication in a mutant strain of HIV, as compared to a sample strain, then the mutant virus has a four-fold resistance to that drug. Currently, it is not known how great a fold resistance is required for treatment to fail, and this is likely to differ with different drugs and/or drug classes.

Folic Acid: a part of the VITAMIN B complex that is required for certain metabolic reactions.

Follicle: a small body cavity with a secretory or excretory function.

Follicular Dendritic Cell (FDC): a VIRUS-trapping DENDRITIC CELL found in LYMPH NODE follicles (see GERMINAL CENTER).

Fomites: dried droplets of respiratory secretions.

Fomivirsen (Vitravene): Isis Pharmaceuticals' ANTISENSE DRUG that is approved to treat CYTOMEGALOVIRUS (CMV) RETINITIS as an INTRAOCULAR injection.

Food and Drug Administration (FDA): an agency of the United States Department of Health and Human Services. Aside from regulating the safety of foods and cosmetics, the FDA regulates the testing of EXPERIMENTAL DRUGS and approves new medical products for marketing based on evidence of safety and EFFICACY.

Fortovase: see SAQUINAVIR.

Fosamprenavir: a PROTEASE INHIBITOR being developed by GlaxoSmithKline. Fosamprenavir is a PRODRUG of AMPRENAVIR.

Foscarnet (Foscavir): a FDA-approved ANTIVIRAL drug to treat CYTOMEGALOVIRUS (CMV) infection in the RETINA and elsewhere in the body. It is also approved for ACYCLOVIR-resistant herpes simplex virus in immune deficient persons. Kidney toxicity is a serious problem with foscarnet. Other SIDE EFFECTS include seizures, ANEMIA, nausea and skin rashes.

Foscavir: see FOSCARNET.

Fovea: a region in the middle of the RETINA (MACULA) that is responsible for detailed central vision.

Free HIV: HIV VIRUS that has not entered a cell. Free HIV can be found in blood and other bodily fluids, and it is this that is measured by VIRAL LOAD tests.

Free Radical: a chemically active, charged atom or complex of atoms containing an excess or deficient number of electrons. Radicals seek to transfer electrons from or to other atomic complexes in order to achieve a more stable configuration. This process can damage the large molecules within cells. See OXIDATION.

FTC: see EMTRICITABINE.

Funduscopy: a thorough eye screening in which the pupil is dilated and the RETINA and the base (fundus) of the eye are examined with an opthalmoscope for the presence of CYTOMEGALOVIRUS (CMV) RETINITIS or other opthalmological problems.

Fungal Infection: a range of distinct diseases caused by fungi (see FUNGUS). CANDIDIASIS, cryptococcosis (see CRYPTOCOCCUS) and HISTOPLASMOSIS are examples of AIDS-related fungal infections.

Fungizone: see AMPHOTERICIN B.

Fungus: one of a group of primitive, nonvascular plants lacking chlorophyll. Among the fungi are mushrooms, yeasts, and molds. Some fungi are single-celled but differ from BACTERIA in that they have a distinct nucleus and other cellular structures.

Fusin: see CXCR-4.

Fusion Inhibitor: a class of anti-HIV drugs designed to prevent HIV from fusing with, and thereby infecting, CD4 CELLS.

Fuzeon: see ENFUVIRTIDE

G

Gag Gene: an HIV GENE that contains the genetic code for the CAPSID PROTEINS.

Gamma Globulin: see IMMUNOGLOBULIN G.

Ganciclovir (Cytovene): an ANTIVIRAL drug sold in both INTRAVENOUS (IV) and oral forms. The intravenous form is FDA-approved as treatment of CYTOMEGALOVIRUS (CMV) RETINITIS in immune-deficient patients. The oral form is approved for preventing CMV in patients at risk and for MAINTENANCE THERAPY to control existing CMV retinitis after an initial course of IV ganciclovir. As maintenance therapy, oral ganciclovir is not as effective as IV ganciclovir. Ganciclovir's main SIDE EFFECT is BONE MARROW SUPPRESSION, leading to low white blood cell and PLATELET counts. Concurrent use with ZIDOVUDINE (AZT) is not tolerated by some.

Gardnerella: BACTERIA that frequently cause vaginitis.

Gastroenteritis: INFLAMMATION of the stomach and intestines, which can cause abdominal pain and diarrhea.

Gastrointestinal (GI) Tract: the organs that absorb and digest food and eliminate the waste products. The GI tract includes the mouth, esophagus, stomach, small and large intestines, colon and rectum.

G-CSF: see GRANULOCYTE COLONY STIMULATING FACTOR.

Gemfibrozil (Lopid): a drug used to lower blood TRIGLYCERIDES. Because gemfibrozil inhibits the CYP3A4 (see CYTOCHROME P450) pathway, it is not recommended for people on ANTIRETROVIRAL therapy.

Gene: a sequence of DEOXYRIBONUCLEIC ACID (DNA) in the CHROMOSOMES that determines the structure of a specific PROTEIN or ENZYME. Genes regulate the METABOLISM of individual cells and the development and specialization of body cells and tissues.

Gene Therapy: any of a number of experimental treatments in which cell GENES are altered or added to. As it concerns HIV, gene therapies attempt to provoke new immune activity, try to render cells resistant to infection or provoke the synthesis of ENZYMES that destroy viral material within cells.

Genital Herpes: see HERPES VIRUS.

Genital Ulcer Disease (GUD): ulcerative lesions on the genitals, usually caused by a sexually transmitted condition such as HERPES VIRUS, syphilis or CHANCROID. The presence of genital ulcers may increase the risk of transmitting HIV.

Genital Warts: see CONDYLOMA ACUMINATUM.

Genome: an organism's entire genetic code.

Genotype: the genetic makeup of an individual organism, determined by the sequence of NUCLEOTIDES in its GENES. See also PHENOTYPE.

Genotypic Assay: a blood test that determines the genetic sequences of an organism. In HIV, frequently performed in order to establish whether certain viral MUTATIONS conferring drug RESISTANCE are present. See also PHENOTYPIC ASSAY.

Germinal Center: one of a series of FOLLICLES or cavities around the periphery of LYMPH NODES. Germinal centers are the site of ANTIBODY production and are populated mostly by B CELLS but include a few T CELLS and MACROPHAGES. As HIV infection progresses, the germinal centers gradually decay.

GI Tract: see GASTROINTESTINAL TRACT.

GLQ223: see COMPOUND Q.

Glucophage: see METFORMIN.

Glucose: a sugar found in fruits and honey. If glucose is found in urine, it could be a sign of diabetes.

Glutamine: an AMINO ACID used by the IMMUNE SYSTEM, muscle tissue and the digestive system. It is used as a supplement to help increase strength and muscle size.

Glutathione (GSH): a key ANTIOXIDANT compound required for the smooth functioning of all cells. It is composed of three AMINO ACIDS: CYSTEINE, GLUTAMINE and GLYCINE. Besides acting as an antioxidant, glutathione is involved in PROTEIN synthesis, AMINO ACID transport, and in the recycling of other ANTIOXIDANTS, such as VITAMIN C.

Glycine: an AMINO ACID used to build PROTEINS.

Glycoprotein: a conjugate molecule made up of both PROTEIN and CARBOHYDRATE components.

Glycyrrhizin: a substance isolated from the root of the licorice plant. Used traditionally as an anti-inflammatory and liver-protecting agent. Possible SIDE EFFECTS include low potassium levels and high blood pressure.

GM-CSF: see GRANULOCYTE-MACROPHAGE COLONY STIMULATING FACTOR.

Gonorrhea: a common sexually transmitted bacterial infection. Symptoms include difficulty urinating, a greenish-yellow discharge and itching, burning or tenderness around the vagina or urethra. ANTIBIOTICS, such as ceftriaxone or Bactrim, are often used as treatment.

gp41: a GLYCOPROTEIN from HIV's outside ENVELOPE that complexes with GP120 to form the mechanism enabling HIV to latch onto and enter cells. gp41 uses a three-prong, harpoon-like mechanism to penetrate cell membranes.

gp120: a GLYCOPROTEIN on HIV's ENVELOPE that binds to the CD4 molecules and CHEMOKINE RECEPTORS on cells' outside membrane. Free gp120 in the body may be toxic to cells in its own right, causing CD4 CELL depletion in the IMMUNE SYSTEM through APOPTOSIS and neurological damage leading to AIDS DEMENTIA COMPLEX.

gp160: the precursor GLYCOPROTEIN to both of HIV's outer ENVELOPE PROTEINS: GP41 and GP120. Also refers to the gp120-

gp41 complex as it exists on the outside of mature HIV.

Grade 1 Adverse Event: a SIDE EFFECT that is usually transient, requires no special treatment and does not interfere with a patient's daily activities.

Grade 2 Adverse Event: a SIDEEFFECT that involves a little inconvenience or concern to the patient and may interfere with daily activities, but which usually can be controlled with simple therapeutic measures.

Grade 3 Adverse Event: a SIDE EFFECT that interrupts the patient's daily activities and which usually requires systemic drug therapy or other treatment.

Grade 4 Adverse Event: a SIDE EFFECT that is unacceptable and intolerable, or that is irreversible, or that causes the patient to be in imminent danger of death.

Granulocyte: a type of white blood cell (LEUKOCYTE) filled with sacs containing compounds that digest microorganisms. Granulocytes are part of the innate IMMUNE SYSTEM and have broad-based activity. They do not respond only to specific ANTIGENS as do B CELLS and T CELLS. Basophils, EOSINOPHILS and NEUTROPHILS are all granulocytes.

Granulocyte Colony Stimulating Factor (G-CSF, Neupogen): a natural HORMONE that stimulates production of GRANULOCYTES, a type of white blood cell (LEUKOCYTE). Its synthetic form has been approved by the FDA for prevention of drug-induced NEUTROPENIA.

Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF): a HORMONE that stimulates the production of NEUTROPHILS, MONOCYTES and MACROPHAGES. A synthetic form of GM-CSF (Leukine) is used to treat NEUTROPENIA.

Granulocytopenia: an abnormally low number of GRANULOCYTES in the blood, which increases risk of severe bacterial infection.

Granuloma Inguinale: a sexually transmitted disease, caused by Donovania granulomatis, that typically affects the groin, genitals or perianal area. It is usually treated with ANTIBIOTICS.

Growth Factor: one of many intercellular regulatory molecules that affects cell proliferation and maturation in various tissues.

GSH: see GLUTATHIONE.

Guanine: one of the four bases of RNA (which also includes CYTOSINE, ADENINE and URACIL) and DNA (which also includes cytosine, adenine and THYMINE).

Guanosine: a NUCLEOSIDE of GUANINE. ABACAVIR is an ANALOG of guanosine.

GUD: see GENITAL ULCER DISEASE.

GW-433908: see fosamprenavir.

H

HAART: see HIGHLY ACTIVE ANTIRETROVIRAL THERAPY.

Habitus: the physical characteristics or body shape of a person.

Half-Life: the amount of time required for half of a given substance (such as a drug) or half the current population of a given cell type to be eliminated from the body.

HBC: see HEPATITIS B VIRUS.

HCG: see HUMAN CHORIONIC GONADOTROPIN.

HCV: see HEPATITIS C VIRUS.

HDL: see HIGH DENSITY LIPOPROTEIN.

Helper T CELL: see CD4 CELL.

Hemarthrosis: bleeding into a joint.

Hematocrit: percent, by volume, of red blood cells in a particular amount of blood. The volume of red blood cells is obtained by separating the cells from other blood components by means of a centrifuge.

Hematoma: localized swelling that is filled with blood, caused by a rupture in the wall of a blood vessel. The blood is usually in an organ or a soft tissue space, such as muscle.

Hematopoietic System: the tissues that produce the cellular elements of peripheral blood.

Hematuria: red blood cells in the urine.

Hemiparesis: paralysis on one side of the body.

Hemodialysis: a medical procedure that uses a machine to perform the functions of the kidneys, e.g., filtering waste products from the bloodstream. It is often a treatment in end-stage kidney disease.

Hemoglobin: the iron-containing PROTEIN in red blood cells that carries oxygen through the bloodstream.

Hemolysis: destruction of the red blood cells.

Hemolytic Anemia: ANEMIA caused by the destruction of red blood cells.

Hemophilia: a genetic disorder that affects mostly men and prevents normal blood clotting. It is treated by life-long injections of a synthetic version of the clotting factor lacking in people with the disease.

Hemoptysis: coughing blood from the lungs, a possible indication of TUBERCULOSIS.

Hemorrhage: internal bleeding through ruptured or unruptured blood vessel walls.

Heparin: a chemical that prevents the blood from clotting.

Hepatic: refers to the liver.

Hepatitis: INFLAMMATION of the liver caused by MICROBES or chemicals. Often accompanied by JAUNDICE, enlarged liver, fever, fatigue and nausea and high levels of liver ENZYMES in the blood.

Hepatitis A infection: a self-limiting VIRUS-induced liver disease caused by hepatitis A virus (HAV). Hepatitis A is acquired through ingesting fecally contaminated water or food or engaging in sexual practices involving anal contact. Injection drug users who share unclean needles also are at risk.

Hepatitis B infection: a VIRUS-induced liver disease that usually lasts no more than six months, but becomes CHRONIC and life-threatening in 10 percent of the cases. Caused by the hepatitis B virus (HBV). The highly contagious hepatitis B virus can be transmitted through sexual contact, contaminated syringes and blood transfusions.

Hepatitis C infection: a VIRUS-induced liver disease caused by hepatitis C virus (HCV). It is more likely than hepatitis B to become CHRONIC and lead to liver degeneration (CIRRHOSIS).

Hepatoma: a liver tumor.

Hepatomegaly: liver enlargement.

Hepatotoxicity: TOXICITY affecting the liver.

Herpes Virus: a group of VIRUSES that includes herpes simplex type 1 (HSV-1), herpes simplex type 2 (HSV-2), CYTOMEGALOVIRUS (CMV), EPSTEIN-BARR VIRUS (EBV), VARICELLA ZOSTER VIRUS (VZV), human herpes virus type 6 (HHV-6) and KAPOSI'S SARCOMA (KS) herpes virus (HHV-8). Herpes simplex virus 1 (HSV-1) can cause painful cold sores or fever blisters on the lips, in the mouth or around the eyes; herpes simplex virus 2 (HSV-2) is usually transmitted sexually and generally causes lesions in the anus or the genital area.

Herpes Zoster: see both SHINGLES and VARICELLA ZOSTER VIRUS.

HGH: see HUMAN GROWTH HORMONE.

HHV-8 (KSHV, Kaposi's Sarcoma [KS] Herpes Virus): a HERPES VIRUS thought to trigger the development of KAPOSI'S SARCOMA lesions. HHV-8's mode of transmission has not been determined, but may possibly be spread by kissing.

Hickman Catheter®: (HICKMAN is a registered trademark of C. R. Bard, Inc. and its related company, BCR, Inc.) a flexible tube that can be surgically inserted into a large vein and left in place for a long period of time. Used to administer drugs such as FOSCARNET and AMPHOTERICIN B, which must be regularly and slowly introduced into the body but cannot be taken orally.

High Density Lipoprotein: a LIPOPROTEIN that contains more PROTEIN than fat, often called "good cholesterol."

Highly Active Antiretroviral Therapy (HAART): anti-HIV treatment, often including a combination of a PROTEASE INHIBITOR or NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR and two REVERSE TRANSCRIPTASE INHIBITORS, whose purpose is to reduce VIRAL LOAD to undetectable levels.

Histoplasmosis: an OPPORTUNISTIC CONDITION caused by a FUNGUS infection acquired by inhaling spores of the fungus present in soil or dust. The fungus is widespread only in the central United States and Latin America. The disease can cause fever, skin lesions, ANEMIA and respiratory distress. Histoplasmosis outside the lungs is an AIDS-DEFINING ILLNESS. AMPHOTERICIN B and ITRACONAZOLE are approved treatments.

HIV: see HUMAN IMMUNODEFICIENCY VIRUS.

HIV-1: see HUMAN IMMUNODEFICIENCY VIRUS TYPE 1.

HIV-2: see HUMAN IMMUNODEFICIENCY VIRUS TYPE 2.

HIV-Associated Adipose Redistribution Syndrome (HARS): a general term referring to the variety of body fat composition changes associated with ANTIRETROVIRAL therapy. The natural history and cause (or causes) is not clearly understood. See also LIPODYSTROPHY.

HIV Network for Prevention Trials (HIVNET): a group, funded by The National Institute of Allergy and Infectious Diseases (NIAID), that conducts domestic and international multi-center trials to evaluate promising interventions to prevent the transmission of HIV. Interventions studied include HIV VACCINES, TOPICAL MICROBICIDES, sexually transmitted disease (STD) treatment, PROPHYLAXIS to prevent VERTICAL TRANSMISSION, and behavioral risk reduction strategies.

HIV RNA: The genetic material of HIV. VIRAL LOAD ASSAYS test for HIV RNA and the result is usually reported as the number of copies per milliliter of plasma.

Hivid: see DIDEOXYCYTIDINE.

HIVIG: an ANTIBODY preparation taken from people who produce high levels of HIV antibodies. See PASSIVE IMMUNOTHERAPY.

HIVNET: see HIV NETWORK FOR PREVENTION TRIALS.

Hodgkin's Disease: a progressive malignant cancer of the lymphatic system. Symptoms include swollen LYMPH NODES, SPLEEN and liver, wasting, weakness, fever, itching, night sweats and anemia. Treatment includes radiation and CHEMOTHERAPY.

Holistic Medicine: various systems of health protection and restoration, both traditional and modern, that are reputedly based on the body's natural healing powers, the various ways the different tissues affect one another and the influence of the external environment. See also ALTERNATIVE MEDICINE.

Home Access: see HOME-BASED HIV TESTING KITS.

Home-Based HIV Testing Kits (Confide, Home Access): FDA-approved over-the-counter test kits available in pharmacies and by mail order. The kit is not actually used for home testing, but, rather, for home collection of samples. Purchasers send a small blood sample to the manufacturer for HIV-testing and then phone anonymously for their test results.

Homocysteine: a sulfur-containing AMINO ACID. High levels of homocysteine in the blood have been linked to increased risk of coronary artery disease and stroke.

Hormone: an active chemical substance formed in one part of the body and carried in the blood to other parts of the body where it stimulates or suppresses cell and tissue activity.

Host: an organism that supports the growth of a parasite or infectious organism.

HPV: see HUMAN PAPILLOMAVIRUS.

HU: see HYDROXYUREA.

Human Chorionic Gonadotropin (HCG): a HORMONE secreted during pregnancy to prevent the mother's body from rejecting the fetus as foreign. Commercial preparations have shown some effect against KAPOSI'S SARCOMA and HIV.

Human Growth Hormone (HGH): a PEPTIDE HORMONE secreted by the anterior pituitary gland in the brain. HGH enhances tissue growth by stimulating LEAN BODY MASS formation. RECOMBINANT, or genetically engineered, HGH (Serostim, produced by Serono Laboratories) is approved as a treatment to reverse AIDS-related WASTING SYNDROME.

Human Immunodeficiency Virus (HIV): a RETROVIRUS that is believed to cause AIDS. HIV can be transmitted sexually, by blood-to-blood contact, and perinatally (from mother to child).

Human Immunodeficiency Virus Type 1 (HIV-1): an infectious RETROVIRUS recognized as the agent that induces immune suppression leading to AIDS.

Human Immunodeficiency Virus Type 2 (HIV-2): a VIRUS closely related to HIV-1 that also leads to immune suppression. HIV-2 is not as virulent as HUMAN IMMUNODEFICIENCY VIRUS TYPE 1 and is epidemic only in West Africa.

Human Papillomavirus (HPV): a member of the papova family of VIRUSES. HPV causes warts or nipple-like protrusions on the skin. HPV has also been associated with cervical cancer in women as well as anal cancer in either sex.

Humatin: see PAROMOMYCIN.

Humoral: of or related to elements in the blood or other BODILY FLUIDS.

Humoral Immunity: the ANTIBODY-producing branch of the IMMUNE SYSTEM, the result of stimulation of B CELLS and Th2 T helper (CD4) cells. See TH2 RESPONSE.

Hycamtin: see TOPOTECAN.

Hydrea: see HYDROXYUREA.

Hydroxyurea (Hydrea, HU): an approved oral chemotherapeutic agent for leukemia and ovarian cancer. It is an experimental anti-HIV treatment. Hydroxyurea blocks the action of the cellular ENZYME RIBONUCLEOTIDE REDUCTASE, which helps produce the NUCLEOTIDES needed for DNA formation. By reducing the amount of functioning nucleotides, the compound makes intracellular HIV more sensitive to the defective NUCLEOSIDE ANALOGS. Hydroxyurea has been found to be particularly synergistic with ddI (DIDANOSINE) in lab tests. ADVERSE EVENTS primarily involve BONE MARROW SUPPRESSION.

Hyper-: a prefix meaning high, excessive, above normal.

Hypercholesterolemia: high levels of CHOLESTEROL in the blood.

Hypergammaglobulinemia: abnormally high blood levels of IMMUNOGLOBULINS (ANTIBODIES).

Hyperglycemia: high blood sugar.

Hypericin: a compound derived from the herb St. John's Wort. It is an experimental treatment for HUMAN PAPILLOMAVIRUS (HPV). Hypericin inhibits the assembly and SHEDDING of VIRUS particles in infected cells. A synthetic version has been developed. Hypericin's main SIDE EFFECT is extreme PHOTOSENSITIVITY. Clinical studies failed to show anti-HIV ACTIVITY at safe doses.

Hyperimmunoglobulinemia: high levels of ANTIBODIES.

Hyperkalemia: high levels of potassium in the blood.

Hyperlipidemia: high levels of blood LIPIDS.

Hyperplasia: excessive growth of nonmalignant cells.

Hypersensitivity: an abnormally exaggerated IMMUNE RESPONSE to an agent, such as a drug or an ANTIGEN.

Hypersusceptibility: when a MUTATION that allows HIV to resist one drug makes the VIRUS more SUSCEPTIBLE to another drug.

Hypertension: high blood pressure.

Hyperthermia: an experimental procedure that involves temporarily heating patients' body core to temperatures of up to 108 degrees F on the theory that this temperature kills free HIV and HIV-containing cells. One method for accomplishing this is by passing patients' blood through an external heater. This is called extracorporeal whole body hyperthermia. Side effects include death.

Hypertriglyceridemia: high levels of triglycerides in the blood.

Hypo-: a prefix meaning low, below normal.

Hypoglycemia: low levels of blood sugar.

Hypokalemia: low levels of potassium in the blood.

Hypoxia: low levels of oxygen in the blood.

I

IC: see INHIBITORY CONCENTRATION.

Idiopathic: a disease or condition with an unknown cause or origin.

IDU: injection (or INTRAVENOUS) drug user.

IFN: see INTERFERON.

Ig: see IMMUNOGLOBULIN.

IGF: see INSULIN-LIKE GROWTH FACTOR.

IL-1: see INTERLEUKIN-1.

IL-2: see INTERLEUKIN-2.

IL-4: see INTERLEUKIN-4.

IL-10: see INTERLEUKIN-10.

IL-12: see INTERLEUKIN-12.

IM: see INTRAMUSCULAR.

Immune-Based Therapy: anti-HIV treatment that aims to modulate, supplement or extend the body's IMMUNE RESPONSES against HIV infection or other diseases. Also called immunotherapy. Examples of immunotherapies for HIV include PASSIVE IMMUNOTHERAPY (PIT), INTERLEUKIN-2 and THERAPEUTIC VACCINES.

Immune Complex: the cluster formed by the combination of an ANTIGEN and an ANTIBODY.

Immune Deficiency: a breakdown or inability of certain parts of the IMMUNE SYSTEM to function, thus making a person susceptible to certain diseases that they would not have contracted with a healthy immune system. Immune deficiencies may be temporary or permanent and be triggered by genetic mutation, therapy with immune-suppressive drugs (as during organ transplants) or an infection such as HIV.

Immune Modulators: see IMMUNOMODULATOR.

Immune Reconstitution: the natural or therapy-induced revival of immune function in a body damaged by HIV infection, particularly after initiation of a highly potent ANTIVIRAL therapy.

Immune Response: the body's reaction to ANTIGENS, which results in their incapacitation or elimination.

Immune Suppression: see IMMUNOSUPPRESSION.

Immune System: the body's complicated natural defense against disruption caused by invading MICROBES and cancers. There are two aspects of the immune system's response to disease: innate and acquired. The innate part of the response is mobilized very quickly in response to infection and does not depend on recognizing specific PROTEINS or ANTIGENS foreign to an individual's normal tissue. It includes complement, MACROPHAGES, DENDRITIC CELLS and GRANULOCYTES. The acquired, or learned, immune response arises when dendritic cells and macrophages present pieces of antigen to LYMPHOCYTES, which are genetically programmed to recognize very specific AMINO ACID sequences (EPITOPES) that correspond to a particular microbe. The ultimate result is the creation of cloned populations of antibody-producing B CELLS and T CELLS primed to respond to a unique PATHOGEN.

Immune Thrombocytopenic Purpura (ITP): an immune disorder that results in a low number of PLATELETS in the blood. A common disorder in people with HIV, it often resolves as IMMUNE DEFICIENCY worsens. HIV-related ITP usually does not have serious consequences. Its cause has not been definitely determined, but probably has to do with the large number of ANTIBODY-ANTIGEN complexes sponged up by platelets; antibody-coated platelets are destroyed in the spleen. Treatment with AZT (ZIDOVUDINE) or an INTRAVENOUS IMMUNOGLOBULIN (IVIG) frequently alleviates the condition.

Immunization: the process of protecting an individual against communicable diseases by injecting weakened or killed infectious organisms or parts of their structure into the body to cause the IMMUNE SYSTEM to produce ANTIBODIES and activate T CELLS against the organism without causing the full-blown disease.

Immunocompetent: refers to an IMMUNE SYSTEM capable of developing a normal protective response when confronted with invading MICROBES or cancer.

Immunocompromised: refers to an IMMUNE SYSTEM in which the response to infections and tumors is subnormal.

Immunoglobulin (Ig): a general term for ANTIBODIES, which bind onto invading organisms, leading to their destruction. There are five

classes: IgA, IgD, IgM, IgE, IgG.

Immunoglobulin A (IgA): an IMMUNOGLOBULIN found in BODILY FLUIDS such as tears and saliva and in the respiratory, reproductive, urinary and gastrointestinal tracts. IgA protects the body's mucosal surfaces from infection.

Immunoglobulin D (IgD): ANTIBODIES, typically cell surface RECEPTORS, that remove ANTIGENS from the blood.

Immunoglobulin E (IgE): ANTIBODIES that activate an allergic response to foreign particles.

Immunoglobulin G (IgG): the prominent type of IMMUNOGLOBULIN existing in the blood. Also called gamma globulin.

Immunomodulator: a drug such as IL-2 that alters, suppresses or strengthens the body's IMMUNE SYSTEM.

Immunosuppression: weakening of the IMMUNE RESPONSE that occurs with HIV infection as well as with some ANTIVIRAL or anticancer treatments.

Immunotherapy: see IMMUNE-BASED THERAPY.

In Utero: refers to events that occur in the womb during pregnancy. Latin term for "in the uterus."

In Vitro: refers to laboratory experiments conducted in cell cultures grown in an artificial environment, for example in a test tube or culture plate. Latin term for "in glass."

In Vivo: refers to studies conducted within humans or animals; in a living, natural environment. Latin for "in a living body."

Incidence: the rate at which new cases of a disease occur, reported in a specified population over a period of time. See also PREVALENCE.

Inclusion Criteria: conditions that must be met in order to participate in a CLINICAL TRIAL. For example, inclusion in a trial could require a certain VIRAL LOAD or CD4 CELL COUNT.

IND: see INVESTIGATIONAL NEW DRUG.

Indication: the purpose or purposes for which a drug is prescribed. The FDA-approved indications appear on a printed insert included in the manufacturer's drug packaging.

Indinavir (Crixivan): a PROTEASE INHIBITOR from Merck. Indinavir must be taken every eight hours on an empty or mostly empty stomach; fat interferes with its absorption. Small KIDNEY STONES (NEPHROLITHIASIS) are a possible SIDE EFFECT, and patients are advised to drink 48 ounces of liquids per day to minimize the risk of developing stones. Other side effects include nausea, elevated BILIRUBIN levels, stomach pain, headache and diarrhea. There are significant DRUG-DRUG INTERACTIONS when indinavir is combined with other common HIV treatments.

Induction Therapy: the initial, concentrated phase of a particular treatment. See also MAINTENANCE THERAPY.

IFN-A: see ALPHA INTERFERON.

Inflammation: the body's response to tissue injury or infection, mainly localized in the affected tissues and adjacent blood vessels. Blood vessels' permeability is increased, and the area becomes heavily populated with white blood cells (LEUKOCYTES). Signs of inflammation are redness, swelling, pain and sometimes loss of function. Not all of these signs are necessarily present in any given case.

Informed Consent: the acknowledgement that an individual understands and agrees with the purpose, procedures, risks and requirements before participating in an experiment or beginning a therapy. Patients are provided with an "informed consent form" which indicates the potential risks, benefits and alternatives to the therapy in question, as well as their rights to withdraw consent. If a CLINICAL TRIAL is involved, the trial PROTOCOL is outlined, including details about what participants should expect to experience. After reading the informed consent form, individuals sign it to indicate that they understand its contents and agree to proceed with therapy under the conditions it outlines.

Infusion: the process of administering a medication to an individual by slowly injecting a dilute solution of the compound into a vein.

Infusions are often used when the digestive system does not absorb appreciable quantities of a drug that is also too bulky or too toxic to be given by quick injection.

INH: see ISONIAZID.

Inhibitory Concentration (IC): the amount of drug in the blood needed to suppress the reproduction of a MICROBE to a certain extent. For example, IC50 for an ANTIRETROVIRAL drug is the drug concentration needed to reduce HIV activity in cell culture by half. The higher the IC50 is, the more resistance HIV is exhibiting to that drug.

Innate Immune Response: see IMMUNE SYSTEM.

Institutional Review Board (IRB): a regulating committee composed of internal staff, hospital affiliates and community members that reviews and approves all human trials conducted within a particular hospital or research center. The IRB ensures that a trial is conducted in an ethical manner, with proper protection of human subjects.

Insulin: a HORMONE that controls the amount of sugar in the blood. A lack of or resistance to insulin leads to diabetes.

Insulin-Like Growth Factor (IGF): a naturally produced substance that has many of the same effects as GROWTH FACTOR. Two types of IGF are produced by the body, IGF-1 and IGF-2.

Integrase: the HIV ENZYME that inserts HIV's GENES into a cell's normal DNA. Integrase operates after REVERSE TRANSCRIPTASE has created a DNA version of the RNA form of HIV genes present in VIRUS particles. Drugs intended to block the action of integrase are in development.

Intent-to-Treat (ITT) Analysis: a type of data analysis used in CLINICAL TRIALS in which subjects are counted as treatment failures even if they drop out of the trial prior to conclusion. Also, all subjects are included in the analysis as long as they have been randomized. Compare to AS-TREATED ANALYSIS.

Interferon (IFN): one of a number of ANTIVIRAL PROTEINS that modulates the IMMUNE RESPONSE. Interferon alpha (IFN-A) is secreted by a virally infected cell and strengthens the defenses of nearby uninfected cells. A manufactured version of IFN-A (trade names: Roferon, Intron A) is an FDA-approved treatment for KAPOSI'S SARCOMA (KS), HEPATITIS B VIRUS and HEPATITIS C VIRUS. Interferon gamma (IFN-G) is synthesized by IMMUNE SYSTEM cells (NATURAL KILLER CELLS and CD4 CELLS). It activates MACROPHAGES and helps orient the immune system to a mode that promotes cellular immunity. See TH1 RESPONSE.

Interferon Alpha: see ALPHA INTERFERON.

Interferon Gamma: see INTERFERON.

Interim Analysis: an intermediary analysis of CLINICAL TRIAL data, performed at a point at which enough data have been gathered to derive preliminary, but not necessarily complete, conclusions. Interim analyses are performed to see whether continuation of a clinical trial is warranted.

Interleukin: one of a large group of GLYCOPROTEINS that acts as CYTOKINES to communicate between LEUKOCYTES. The interleukins are secreted by and affect many different cells in the IMMUNE SYSTEM. See also INTERLEUKIN-1, INTERLEUKIN-2, INTERLEUKIN-4, INTERLEUKIN-10 and INTERLEUKIN-12.

Interleukin-1 (IL-1): a CYTOKINE that is released early in an IMMUNE SYSTEM response by MONOCYTES and MACROPHAGES. It stimulates T CELL proliferation and PROTEIN synthesis. Another effect of IL-1 is that it causes fever. See also INTERLEUKIN.

Interleukin-2 (IL-2): a CYTOKINE secreted by Th1 CD4 CELLS to stimulate CD8 CYTOTOXIC T LYMPHOCYTES. IL-2 also increases the proliferation and maturation of the CD4 cells themselves. During HIV infection, IL-2 production gradually declines. Use of IL-2 therapy is under study as a way to raise CD4 cell counts and restore immune function. See also INTERLEUKIN.

Interleukin-4 (IL-4): a CYTOKINE secreted by Th2 CD4 CELLS that promotes ANTIBODY production by stimulating B CELLS to proliferate and mature. See also INTERLEUKIN.

Interleukin-10 (IL-10): a CYTOKINE released by immune cells. IL-10 reduces elevated levels of HIV-stimulating cytokines (see PROINFLAMMATORY CYTOKINES, TUMOR NECROSIS FACTOR ALPHA) and the inflammatory activity common to infection. See also INTERLEUKIN.

Interleukin-12 (IL-12): a CYTOKINE released by MACROPHAGES in response to infection that promotes the activation of CELL-MEDIATED IMMUNITY. Specifically, IL-12 triggers the maturation of Th1 CD4 CELLS, specific CYTOTOXIC T LYMPHOCYTE responses and an increase in the activity of NATURAL KILLER CELLS. IL-12 is under study as an IMMUNOTHERAPY in HIVinfection. See also INTERLEUKIN.

International Unit (IU): a measurement of the mass of certain VITAMINS and drugs based on their expected biological effects (thus, they vary from compound to compound). IUs are determined by international agreement.

Intolerant: unable to take a drug because of an ADVERSE EVENT or laboratory TOXICITY.

Intralesional: injected directly into a lesion.

Intramuscular (IM): injected directly into a muscle.

Intraocular: injected into the eye.

Intraocular Implant (Vitrasert): Chiron Vision's eye implant which is FDA-approved for the treatment of CYTOMEGALOVIRUS (CMV) RETINITIS. The implant is a five to eight month time-release device containing GANCICLOVIR that is placed inside the eye during a short surgical procedure. The implant is more effective at treating CMV retinitis than systemic therapies because it is able to deliver medication directly to the site of the infection, bypassing the BLOOD-RETINA BARRIER. Possible SIDE EFFECTS include temporary blurring of vision after the operation and RETINAL DETACHMENTS. The implant cannot prevent CMV in other parts of the body or in the other eye.

Intrapartum: during birth.

Intrathecal: injected directly into the membrane surrounding the spinal canal.

Intravenous (IV): injected directly into a vein.

Intravenous Immunoglobulin (IVIG): a sterile solution of concentrated ANTIBODIES extracted from healthy people. IVIG is used to prevent bacterial infections in patients with low or inappropriate antibody production. It is also used to restore low PLATELET counts (see IMMUNE THROMBOCYTOPENIC PURPURA).

Intravitreal: injected into the eye's VITREOUS HUMOR between the lens and the RETINA.

Intron A: see ALPHA INTERFERON.

Investigational New Drug (IND): status given an EXPERIMENTAL DRUG after the FDA approves an application to test it in people.

Invirase: see SAQUINAVIR.

IRB: see INSTITUTIONAL REVIEW BOARD.

Isolate: a genetically homogeneous HIV clone with distinguishing characteristics and extracted from a single source.

Isoniazid (INH): an orally administered drug used to treat or prevent TUBERCULOSIS infection. SIDE EFFECTS include liver INFLAMMATION and PERIPHERAL NEUROPATHY.

-itis: a suffix that indicates INFLAMMATION, usually due to infection, of the root word. For example, "vaginitis" means inflammation of the vagina.

ITP: see IMMUNE THROMBOCYTOPENIC PURPURA.

Itraconazole (Sporanox): an oral antifungal drug used for a number of AIDS-related fungal infections. Itraconazole concentrates in the skin and is particularly effective for skin conditions. Possible SIDE EFFECTS include digestive upset, rashes and headaches. A liquid form or suspension is FDA-approved for oral and esophageal CANDIDIASIS.

ITT Analysis: see INTENT-TO-TREAT ANALYSIS.

IU: see INTERNATIONAL UNIT.

IV: see INTRAVENOUS.

IVIG: see INTRAVENOUS IMMUNOGLOBULIN.

J

Jaundice: yellow pigmentation of the skin and whites of the eyes caused by elevated blood levels of BILIRUBIN. The condition is associated with liver or gallbladder disease or excessive destruction of red blood cells. The protease inhibitor atazanavir can cause jaundice as a side effect.

JC Virus: see PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY.

K

K Cell: A type of nonspecific LYMPHOCYTE that seeks out and kills any cells coated with any ANTIBODY. (The cells become coated because they are infected with VIRUS and display viral PROTEINS on their surface membranes.)

Kaplan-Meier Curve: a method for analyzing a therapy's EFFICACY or TOXICITY by graphically displaying "survival" or the occurrence of a study ENDPOINT or dropout. The Kaplan-Meier curve displays a statistical estimate of the percent of people receiving a given therapeutic REGIMEN who, at each observation point after entering a trial, continue to do acceptably well on their assigned therapy. Plotting the curves for a trial's different treatment ARMS on the same chart yields a comparison of the various regimens.

Kaposi's Sarcoma (KS): an AIDS-DEFINING ILLNESS consisting of individual cancerous lesions caused by an overgrowth of blood vessels. KS typically appears as pink or purple painless spots or nodules on the surface of the skin or oral cavity. KS also can occur internally, especially in the intestines, LYMPH NODES and lungs, and in this form is life-threatening. KS is most likely triggered by a species of HERPES VIRUS similar to EPSTEIN-BARR VIRUS (see HHV-8). Up to now, KS has been treated with ALPHA INTERFERON, radiation therapy (outside the oral cavity), and various systemic and intralesional cancer CHEMOTHERAPIES. Possible antiviral remedies, such as CIDOFOVIR and FOSCARNET, are now being examined, as well as TOPICAL treatments.

Kaposi's Sarcoma Herpes Virus: see HHV-8.

Karnofsky Performance Score: a scale for analyzing a patient's ability to perform certain ordinary tasks: 100 - normal, no complaints; 70 - unable to carry on normal activity; 50 - requires considerable assistance; 40 - disabled; 30 - hospitalization recommended.

Ketoconazole (Nizoral): an antifungal medication available in pill and liquid form that is effective against a variety of fungal infections such as oral, vaginal and esophageal THRUSH and cryptococcosis (see CRYPTOCOCCUS). Persons taking ketoconazole must have their liver function tested periodically because of the slight danger of serious liver damage.

Kidney Stone: a painful solid mass in the kidney or urinary system, caused by the solidification or precipitation of a dissolved substance in the urine.

Killer Cell: a generalized name for IMMUNE SYSTEM cells that kill cancerous and VIRUS-infected cells. Among the killer cells are killer T CELLS (CYTOTOXIC T LYMPHOCYTES), NATURAL KILLER CELLS and K CELLS.

Killer T Cell: see CYTOTOXIC T LYMPHOCYTE.

KS: see KAPOSI'S SARCOMA.

KSHV: see HHV-8.

L

Lactic Acidosis: a rare but deadly metabolic disorder. Symptoms can include weight loss, fatigue, malaise, nausea, vomiting, abdominal pain, shortness of breath and low SERUM bicarbonate levels. NUCLEOSIDE ANALOGS have been associated with mitochondrial toxicity, which can lead to lactic acidosis.

Lactobacillus: BACTERIA that create lactic acid.

Lactose Intolerance: the inability to digest milk products due to the lack of the ENZYME lactase, which breaks down milk sugar (lactose).

Lamivudine (3TC, Epivir): a NUCLEOSIDE ANALOG from GlaxoSmithKline with anti-HIV and anti-HEPATITIS B activity. Most common SIDE EFFECTS are nausea, headache, fatigue, diarrhea and ANEMIA.

Langerhans Cell: the type of DENDRITIC CELL found in the skin.

Last Observation Carried Forward (LOCF): a type of data analysis in CLINICAL TRIALS in which the last results before a subject drops out of the trial are counted as if they occurred at the end of the trial. Used when data are missing due to loss to follow-up.

Late Breaker: a presentation at a scientific conference that was submitted too late to be included in the original program but that was deemed to merit inclusion in the conference.

Latency: a QUIESCENT period during a disease process. Clinical latency is an ASYMPTOMATIC period in the early years of HIV infection. The period of latency is characterized in the peripheral blood by stable, slightly depressed CD4 CELL COUNTS and low HIV levels. Research indicates that HIV remains quite active in the LYMPH NODES during this period. Cellular latency is a condition that exists in some cells after HIV has integrated its GENOME into the cell's DNA but has not yet begun to replicate. Cellular latency may last for years, making the eradication of HIV from the body unlikely.

Lavage: the process of washing out an internal organ or cavity for treatment or to obtain a sample.

L-Carnitine: a naturally occurring cell constituent that modulates fat METABOLISM, in particular the mitochondrial intake of LIPID derivatives. L-carnitine has been proposed as a treatment for WASTING SYNDROME and the MYOPATHY associated with AZT (ZIDOVUDINE).

LDL Cholesterol: see LOW DENSITY LIPOPROTEIN CHOLESTEROL.

Lean Body Mass: the body's muscle and organ tissue.

Lecithinized Superoxide Dismutase (PC-SOD): a synthetic version of superoxide dismutase (SOD), one of the more potent ANTIOXIDANTS produced by the body.

Lentivirus: a subgroup of the RETROVIRUS family that includes HIV and is characterized by long periods of clinical LATENCY after infection.

Lesion: a disturbed area of tissue - a wound, ulcer, injury, nodule or tumor on the skin or elsewhere.

Leukine: see GRANULOCYTE-MACROPHAGE COLONY STIMULATING FACTOR.

Leukocyte: any of the various white blood cells, which together make up the IMMUNE SYSTEM. NEUTROPHILS, LYMPHOCYTES and MONOCYTES are all leukocytes.

Leukocytosis: an abnormally high number of LEUKOCYTES, or white blood cells, in the blood. This condition can occur during many types of infection and INFLAMMATION.

Leukopenia: an abnormally low number of total LEUKOCYTES, or white blood cells, circulating in the blood, frequently the result of drug-induced BONE MARROW SUPPRESSION.

LFT: see LIVER FUNCTION TEST.

Libido: sex drive.

Licorice: see GLYCYRRHIZIN.

Ligand: any molecule that binds to the surface of another molecule, such as an immune cell RECEPTOR. For examples of receptors see CCR5, CXCR-4, CD4.

Limit of Detection: refers to the SENSITIVITY of a quantitative diagnostic test, such as the VIRAL LOAD ASSAY. The limit of detection is the level below which the test can no longer accurately measure the amount of a substance, such as HIV RNA. If a person has an "undetectable" viral load, it does not mean that HIV is no longer present, but rather, that the test is not sensitive enough to measure the amount (see also RESERVOIR). Also called the limit of quantification.

Limit of Quantification: see LIMIT OF DETECTION.

LIP: see LYMPHOID INTERSTITIAL PNEUMONITIS.

Lipid: a fatty substance.

Lipitor: see ATORVASTATIN.

Lipodystrophy: a disturbance of fat METABOLISM that involves the absence of fat and/or the abnormal distribution of fat in the body. Currently, "lipodystrophy" is not clearly defined and the term is used to refer to a variety of SYNDROMES, including wasting in the face and extremities, an accumulation of abdominal fat and breast enlargement. The cause is unknown, but it could be a result of HIV infection and/or ANTIRETROVIRAL therapy.

Lipomas: tumors consisting of fat cells.

Lipomatosis: A disorder characterized by deposits of fat beneath the skin of the neck, upper body, arms and legs. The origin is uncertain, but it is thought to be genetic. Lipomatosis often occurs in conjunction with alcoholic liver disease, macrocytic ANEMIA and PERIPHERAL NEUROPATHY. It usually affects men and is most common in the Mediterranean.

Lipoprotein: a chemical compound made of fat and PROTEIN. Lipoproteins are found in the blood, where they carry CHOLESTEROL.

Liposome: microscopic globules of LIPIDS manufactured to enclose medications. The liposome's fatty layer is supposed to protect and confine the enclosed drug until the liposome adheres to the outer membrane of target cells. By delivering treatments directly to the cells needing them, drug EFFICACY may be increased while overall TOXICITY is reduced.

Liposuction: a surgical procedure in which fat deposits are suctioned from specific parts of the body, e.g., the abdomen, buttocks, hips, thighs, or back. Liposuction is sometimes used to treat truncal adiposity or BUFFALO HUMP, although results can vary.

Liver Enzyme: see both ALANINE AMINOTRANSAMINASE and ASPARTATE AMINOTRANSAMINASE.

Liver Function Test (LFT): a test that measures the blood SERUM level of any of several ENZYMES produced by the liver. An elevated liver function test is a sign of possible liver damage.

LOCF: see LAST OBSERVATION CARRIED FORWARD.

Log (Logarithm): formally, the number of times ten must be multiplied with itself to equal a certain number. For example, log 5 is 100,000 (10 x 10 x 10 x 10 x 10). VIRAL LOAD is often reported in terms of log. In addition, logs are used to measure changes in viral load. For example, a reduction in viral load from 100,000 to 1,000 copies/ml is a 2.0 log (or 99 percent) reduction (100,000 divided by 100 [2.0 log or 10 x 10] equals 1,000). Note that while a one log reduction is a ten-fold difference, a half log change is not a five-fold difference, rather a change of 3.16-fold (the square root of ten) because 100.5 or 101⁄2 = 3.16.

Logarithm: see LOG.

Long-Term Nonprogressor: an individual who has been infected with HIV for at least seven to twelve years (different authors use different time spans) and yet retains a CD4 CELL COUNT within the normal range and no evidence of disease progression.

Long-Term Survivor: a looser term than LONG-TERM NONPROGRESSOR that indicates any person with any stage of HIV infection, including AIDS, who has been stable over a period of years.

Long Terminal Repeat (LTR): the genetic material at each end of a genetic sequence. When the HIV genes are integrated into a cell's own GENOME, the LTR interacts with cellular and viral factors to initiate the transcription of the HIV DNA into an RNA form that is packaged in new VIRUS particles. Activation of the LTR is a major step in triggering HIV replication.

Longitudinal Study: a study that follows patients over an extended period of time.

Lopid: see GEMFIBROZIL.

Lopinavir (Kaletra, LPV): a PROTEASE INHIBITOR made by Abbott Laboratories. Kaletra (LPV/r) is a combination of lopinavir and a low dose of RITONAVIR, a drug that improves blood levels of lopinavir.

Lotrimin: see CLOTRIMAZOLE.

Lovastatin: a CHOLESTEROL-lowering drug.

Low Density Lipoprotein (LDL) Cholesterol: a LIPOPROTEIN that contains more fat than PROTEIN, often called "bad cholesterol."

LP: see LUMBAR PUNCTURE.

LTR: see LONG TERMINAL REPEAT.

Lumbar Puncture (LP): insertion of a needle into the lower spinal canal to obtain a sample of CEREBROSPINAL FLUID. Also called a spinal tap.

Lymph Fluid: a transparent, slightly yellow fluid that carries LYMPHOCYTES to and from the LYMPH NODES and helps to collect foreign MICROBES. Lymph is derived from tissue fluids. The fluid passes through the lymphatic ducts and then enters the bloodstream.

Lymph Gland: see LYMPH NODE.

Lymph Node: small bean-sized organs made up mostly of densely packed LYMPHOCYTES, LYMPH FLUID and connective tissue. Clusters of lymph nodes are widely distributed in the body and are essential to the functioning of the immune system. They are the main sites where acquired immune responses are launched (see IMMUNE SYSTEM and NAIVE T CELL). Lymph nodes are connected with each other, other lymphoid tissue and the blood by the LYMPHATIC VESSELS.

Lymphadenopathy: swelling or enlargement of the LYMPH NODES due to infection or cancer. The swollen nodes may be palpable or visible from outside the body.

Lymphatic Vessels: a body-wide network of channels, similar to the blood vessels, that transports LYMPH FLUID to the lymphoid tissue and into the bloodstream.

Lymphocyte: white blood cells that mature and reside in the lymphoid organs and are responsible for the acquired immune response (see IMMUNE SYSTEM). The two major types of lymphocytes are T CELLS and B CELLS.

Lymphoid Interstitial Pneumonitis (LIP): a type of pneumonia that affects 35 to 40 percent of children with AIDS and causes hardening of the lung membranes involved in absorbing oxygen. LIP is an AIDS-DEFINING ILLNESS in children.

Lymphoid Tissue: the organs of the lymph system throughout the body, including the BONE MARROW, THYMUS, LYMPH NODES, SPLEEN, tonsils, PEYER'S PATCHES and LYMPHOCYTE aggregates on mucosal surfaces.

Lymphokine: a substance produced by LYMPHOCYTES to precipitate various immune reactions. Lymphokines include the INTERFERONS and INTERLEUKINS and are a subset of the CYTOKINE family.

Lymphoma: a cancer of the LYMPHOID TISSUE, largely a solid tumor with cells arising from proliferating LYMPHOCYTES. Symptoms may include LYMPH NODE swelling, weight loss and fever. Some examples of lymphomas are BURKITT'S LYMPHOMA, HODGKIN'S DISEASE and NON-HODGKIN'S LYMPHOMA. Treatment involves radiation therapy (radiotherapy), CHEMOTHERAPY or both.

Lymphoproliferative Response: a specific IMMUNE RESPONSE that entails rapid T CELL replication. Standard ANTIGENS, such as tetanus toxoid, that elicit this response are used in lab tests of immune competence.

Lysis: the splitting and dissolution of cellular or viral material by chemical action.

M

MAC: see MYCOBACTERIUM AVIUM COMPLEX.

Macrophage: a large scavenger cell that ingests degenerated cells and foreign organisms. Macrophages exist in large numbers

throughout the body and contribute to the development of acquired immunity by acting as ANTIGEN PRESENTING CELLS. They also ingest and destroy foreign matter coated with ANTIBODIES. Macrophages can be infected by HIV.

Macrophage Inflammatory Protein-1 Alpha and Beta (MIP-1a, MIP-1b): CHEMOKINES that bind to the CCR5 RECEPTOR site and interfere with HIV's fusion with uninfected cells.

Macrophage-Tropic HIV (M-Tropic, CCR5-using HIV, NSI HIV): refers to strains of HIV that have an affinity for infecting

MACROPHAGES as well as CD4 CELLS. When entering new cells, M-tropic HIV usually binds to the CCR5 RECEPTOR in addition to the CD4 receptor. This type of HIV is generally a non-syncytia-inducing (NSI) virus (see SYNCYTIUM), it is the type of HIV that is transmitted sexually, and it is generally predominant until late stage disease.

Macula: the pigmented central area or "yellow spot" of the RETINA that is adjacent to the optic nerve. It is the most sensitive area of the retina and contains the FOVEA, a region that is responsible for detailed central vision.

Magnetic Resonance Imaging (MRI): a noninvasive, non-x-ray diagnostic technique based on the magnetic fields of hydrogen atoms in the body. MRI provides computer-generated images of the body's internal tissues and organs.

MAI (Mycobacterium Intercellulare): see MYCOBACTERIUM AVIUM COMPLEX.

Maintenance Therapy: extended drug therapy, usually at a diminished dose, administered after a disease has been brought under control. Maintenance therapy is utilized when a complete cure is not attainable, and a disease is likely to recur if therapy is halted. It is used for CHRONIC infections and tumors. So far, attempts at using maintenance therapy for HIV have been unsuccessful. See also INDUCTION THERAPY.

Major Histocompatibility Complex (MHC): two classes of molecules on cell surfaces. MHC class I molecules exist on all cells and hold and present foreign ANTIGENS to CD8 CYTOTOXIC T LYMPHOCYTES if the cell is infected by a VIRUS or other MICROBE. MHC class II molecules are found on the IMMUNE SYSTEM's ANTIGEN PRESENTING CELLS and display antigen to activate CD4 CELLS.

Malabsorption: inability of the GASTROINTESTINAL TRACT to absorb food, drugs or any substance needed to maintain good health; if not countered, leads to weight loss and AIDS WASTING SYNDROME.

Malaise: a vague feeling of discomfort or uneasiness, often the result of infection or a drug's SIDE EFFECTS.

Malignant: refers to cells or tumors growing in an uncontrolled fashion. Such growths may spread to and disrupt nearby normal tissue or reach distant sites via the bloodstream. By definition, cancers are always malignant, and the term malignancy implies cancer.

Manifestation: the outward sign that an illness is present; a symptom or condition.

MAP-30: see BITTER MELON.

Marinol (Dronabinol): an appetite stimulant composed of TETRAHYDROCANNABINOL (THC), the major psychoactive ingredient in marijuana (see CANNABIS).

Masked: see BLINDED.

Mast Cell: an IMMUNE SYSTEM cell filled with granules of inflammatory chemicals such as histamine. This cell is believed to play a leading role in generating the symptoms of allergy.

MDR-TB: see MULTI-DRUG RESISTANT TUBERCULOSIS.

"Me Too" Drug: an informal term used to describe a drug that offers little or no benefit over a similar drug that has already been approved by the FDA.

Mean: see AVERAGE.

Median: the midpoint in a series of numbers; half the data values are above the median, and half are below. For example, in the odd series 1, 4, 9, 12 and 33, 9 is the median. In the even series 1, 4, 10, 12, 33 and 88, 11 is the median (halfway between 9 and 12). Note, the median is not necessarily the same as the AVERAGE (or mean). For example, the median of 2, 6, 10, 22 and 40 is 10 but the average is 18.

Medulla: the inner portion of an organ.

Megace: see MEGESTROL ACETATE.

Megadosing: medical treatment with very large doses of a naturally occurring, supposedly nontoxic substance, usually a VITAMIN.

Mega-HAART: the use of six or more ANTIRETROVIRALS to treat HIV, typically some or all of which have been used previously by the individual.

Megestrol Acetate (Megace): an appetite stimulant approved for the treatment of weight loss in people with AIDS. Megestrol acetate is a synthetic version of the female hormone PROGESTERONE. Most of the weight gain it leads to has been found to be fat rather than PROTEIN. Possible SIDE EFFECTS include HYPERGLYCEMIA, occasional impotence and decreased LIBIDO in men and uterine bleeding in women.

Memory T Cell: a T CELL that bears RECEPTORS for a specific foreign ANTIGEN encountered during a prior infection or vaccination. After an infection or a vaccination, some of the T cells that participated in the response remain as memory T cells, and can rapidly mobilize and clone themselves should the same antigen be re-encountered during a subsequent infection.

Men Who Have Sex with Men (MSM): a term created to include MSM who do not identify as gay or bisexual.

Meninges: the membranes that envelope the brain and the spinal cord.

Meningitis: INFLAMMATION of the MENINGES. It may be caused by a BACTERIUM, FUNGUS or VIRUS.

Mepron: see ATOVAQUONE.

Meta-Analysis: a method of summarizing previous research by reviewing and combining results from multiple CLINICAL TRIALS. Meta-analyses are attempted when previous studies were too small individually to achieve meaningful or statistically significant results. Because combining data from disparate groups is problematic, meta-analyses usually are considered more suggestive than definitive.

Metabolism: the buildup, breakdown and excretion of substances, commonly used to refer to the breakdown of food (or drugs) and its transformation into energy.

Metformin (Glucophage): a drug used to treat high blood sugar.

Methadone: an oral or INTRAVENOUS OPIATE commonly used to control symptoms of withdrawal from heroin.

Metronidazole (Flagyl): an ANTIBIOTIC used to treat a variety of infections.

MHC: see MAJOR HISTOCOMPATIBILITY COMPLEX.

Microbe: a microscopic organism, such as a BACTERIA, FUNGUS, PROTOZOA or VIRUS.

Microbicide: refers to a range of products, in cream, gel, film, or suppository form, that would substantially reduce the transmission of HIV — and possibly other sexually transmitted infections (STIs) — when applied prior to sex.

Micronutrient: a VITAMIN or mineral that the body must obtain from outside sources. Micronutrients are essential to the body in small amounts because they are either components of ENZYMES or act as coenzymes in managing chemical reactions.

Microsporidiosis: an intestinal infection that causes diarrhea and wasting in people with HIV. It results from two different species of microsporidia, a protozoal parasite. Two common organisms that cause it are Enterocytozoon and Septata. Among the possible treatments are THALIDOMIDE and ALBENDAZOLE.

MIP-1alpha, MIP-1beta: see MACROPHAGE INFLAMMATORY PROTEIN-1 ALPHA AND BETA.

Mitochondria: a rod-shaped or oval body in cells that is the site of energy production by means of OXIDATION. Mitochondrial function can be interrupted by NUCLEOSIDE ANALOGS (LAMIVUDINE [3TC], STAVUDINE [D4T]) due to inhibition of gamma INTERFERON and DNA POLYMERASE, leading to lactic acidosis.

Mitogen: a substance that induces cell division.

Mitosis: the process of cell division.

MM: see MONONEURITIS MULTIPLEX.

Molluscum Contagiosum: a skin condition caused by a pox virus infection, distinguished by small dome-shaped papules (bumps) on the face, upper trunk or extremities. Current treatment is mainly cosmetic. It often involves application of liquid nitrogen to the papules as a means of excising them.

Monoclonal Antibody: an ANTIBODY produced by laboratory cultures of a single CELL LINE. The antibodies are all identical, binding with the same EPITOPE.

Monocyte: a large white blood cell that can leave the blood vessels and enter body tissue, at which point it becomes a MACROPHAGE.

Mononeuritis Multiplex (MM): a rare type of NEUROPATHY that causes patchy areas of movement and asymmetrical sensory abnormalities. MM tends to occur during the ASYMPTOMATIC, early period of HIV infection, but a more severe type, attributed to CYTOMEGALOVIRUS (CMV) infection, has been observed in people with advanced AIDS.

Mononucleosis: an infection caused by the EPSTEIN-BARR VIRUS (EBV) that leads to an increase in mononuclear LEUKOCYTES. Mononucleosis can be spread by saliva and is also known as the "kissing disease" (or simply "mono"). Symptoms include fever, fatigue, sore throat and swollen LYMPH NODES.

Monotherapy: the use of a single drug or therapy to treat a disease or condition.

Morbidity: having an illness or disease.

Mortality: death.

MRI: see MAGNETIC RESONANCE IMAGING.

MSM: see MEN WHO HAVE SEX WITH MEN.

M-Tropic: see MACROPHAGE-TROPIC.

Mucous Membrane: the moist layer of tissue lining the digestive, respiratory, urinary and reproductive tracts - all the body cavities with openings to the outside world except the ears.

Multi-Drug Resistant Tuberculosis (MDR-TB): a strain of TUBERCULOSIS (TB) that does not respond to two or more standard anti-TB drugs. MDR-TB usually arises when treatment is intermittent, thus permitting replication and allowing an accumulation of MUTATIONS in the TB BACTERIA that confer broader and broader drug RESISTANCE.

Multiple Regression Analysis: a statistical method used with one dependent variable and more than one independent variable.

Multivariate Analysis: a statistical analysis that involves more than one dependent variable.

Murine: of or relating to rodents, especially mice.

Mutagen: an agent that has a tendency to increase MUTATIONS.

Mutation: any alteration, loss, gain or exchange of genetic material within a cell or VIRUS. Mutations are perpetuated in succeeding generations of that cell or virus (or of an entire multicellular organism if the mutated cell is a sperm, egg or spore). They can occur spontaneously or in response to environmental factors, including drug therapy. See also RESISTANCE.

Myalgia: pain in one or more muscles.

Myambutal: see ETHAMBUTAL.

Mycelex: see CLOTRIMAZOLE.

Mycobacterium: a group of BACTERIA with many disease-causing members. The causative agents for TUBERCULOSIS, leprosy and MYCOBACTERIUM AVIUM COMPLEX (MAC) all belong to this group.

Mycobacterium Avium Complex (MAC): a serious OPPORTUNISTIC CONDITION caused by two similar BACTERIA (Mycobacterium avium and Mycobacterium intercellulare) found in the soil and dust particles. In AIDS, MAC can spread through the bloodstream to infect LYMPH NODES, BONE MARROW, liver, SPLEEN, spinal fluid, lungs and intestinal tract. Typical symptoms of MAC include night sweats, weight loss, fever, fatigue, diarrhea and enlarged spleen. MAC is usually found in people with CD4 CELL COUNTS below 95. CLARITHROMYCIN, AZITHROMYCIN, ETHAMBUTAL, RIFAMPIN, clofazimine and RIFABUTIN are some of the ANTIBIOTICS commonly used in MAC prevention and treatment. (Treatment of active infection usually involves combination therapy.)

Mycobacterium Intercellulare (MAI): see MYCOBACTERIUM AVIUM COMPLEX.

Mycobutin: see RIFABUTIN.

Mycoplasma: a group of BACTERIA, some of whose members cause disease in animals and humans. Mycoplasma are very simple one-celled organisms without an outer membrane. They penetrate and infect individual cells. Most commonly, mycoplasma causes pneumonia.

Mycosis: any disease caused by a FUNGUS.

Myelin: a fatty substance that covers and protects the nerves.

Myelitis: INFLAMMATION of the spinal cord.

Myelopathy: any disease affecting the spinal cord.

Myelosuppression: see BONE MARROW SUPPRESSION.

Myelotoxic: destructive to BONE MARROW.

Myocardial: refers to the heart's muscle mass.

Myopathy: progressive muscle weakness. Myopathy may arise as a toxic reaction to AZT (ZIDOVUDINE) or as a consequence of HIV infection itself.

N

NAC: see N-ACETYLCYSTEINE.

N-Acetylcysteine (NAC): a naturally occurring substance that is metabolized into the AMINO ACID CYSTEINE. Cysteine is one of the three components of the major cellular ANTIOXIDANT GLUTATHIONE, and people with HIV have decreased levels of this compound. Taking NAC will restore glutathione levels, but it remains to be proven whether this increase in glutathione has clinical benefit. See also OXIDATIVE STRESS.

Nadir: the lowest point.

Naive T Cell: a T CELL arising from the IMMUNE SYSTEM'S production of fresh cells in the BONE MARROW. Naive T cells respond to newly encountered PATHOGENS containing ANTIGENS the immune system has not processed before. The naive T cells' activation and proliferation create an acquired immune response (see IMMUNE SYSTEM) to the newly encountered pathogenic agent. After the disease is eradicated, a portion of the T cell population engendered by the activated naive T cells constitute a reservoir of memory cells, which proliferate and respond very quickly to any recurrence of the disease. See also MEMORY T CELL.

Nandralone Decanoate (Deca Durabolin): an injectable synthetic ANABOLIC STEROID being studied for the treatment of AIDS-related WASTING SYNDROME.

NASBA: see NUCLEIC ACID SEQUENCE-BASED AMPLIFICATION.

National Cancer Institute (NCI): a branch of the NATIONAL INSTITUTES OF HEALTH (NIH) that oversees considerable research in HIV and AIDS-related malignancies.

National Institute of Allergy and Infectious Diseases (NIAID): the federal agency that is responsible for a great deal of the government-sponsored AIDS research. NIAID is a branch of the NATIONAL INSTITUTES OF HEALTH (NIH).

National Institute of Mental Health (NIMH): a branch of the NATIONAL INSTITUTES OF HEALTH (NIH) that oversees neurologic and psychologic research.

National Institutes of Health (NIH): the federal agency responsible for overseeing government-sponsored biomedical research. It is divided into 24 institutes and research centers.

Natural History of Disease: the course of a disease when left untreated.

Natural History Study: a study that observes the development of a disease over time.

Natural Killer (NK) Cell: a type of LYMPHOCYTE that attacks and destroys foreign, VIRUS-infected and cancerous cells. NK cells are not targeted at specific ANTIGENS the way CYTOTOXIC T LYMPHOCYTES are. They are part of the innate rather than the acquired immune response (see IMMUNE SYSTEM).

NC = F: see NONCOMPLETER EQUALS FAILURE.

NCI: see NATIONAL CANCER INSTITUTE.

NDA: see NEW DRUG APPLICATION.

NebuPent: see PENTAMIDINE.

Nef: an HIV regulatory PROTEIN. HIV without nef appears to have lessened capacity to infect new cells. Nef also blocks HIV-infected cells from expressing CD4 and MAJOR HISTOCOMPATIBILITY COMPLEX (MHC) class I molecules on their surfaces, thus limiting the IMMUNE SYSTEM's ability to recognize and kill these cells.

Nelfinavir (Viracept): a PROTEASE INHIBITOR from Agouron / Pfizer, FDA-approved for adults and children over two years old. Nelfinavir should be taken two or three times a day with a meal or light snack. Its most common SIDE EFFECT is diarrhea. Nelfinavir can reduce blood levels of oral contraceptives and increase blood levels of other protease inhibitors.

Neonate: a newborn, typically up to four weeks of age.

Neoplasia: the abnormal growth of new tissue, consisting of a NEOPLASM or tumor.

Neoplasm: literally, a new growth. An abnormal growth of tissue, a tumor.

Neopterin: a substance present in BODILY FLUIDS that is elevated when the IMMUNE SYSTEM is activated. SERUM or CEREBROSPINAL FLUID neopterin levels were measured in early studies as a SURROGATE MARKER for HIV disease.

Nephritis: INFLAMMATION of the kidneys.

Nephrolithiasis: the formation of sediment or small stones in the kidneys. See also KIDNEY STONE.

Nephrotoxicity: damage to the kidneys.

Nerve Growth Factor (NGF): a naturally produced substance that has many roles in the maintenance of nerves and nerve cells, especially sensory ones. Synthetic, RECOMBINANT NGF is a proposed therapy for HIV- and drug-associated NEUROPATHIES.

Neupogen: see GRANULOCYTE COLONY STIMULATING FACTOR.

Neurologic: relating to the nervous system, including the brain.

Neuron: one of the electrically active cells that transmit signals within the brain or nervous system.

Neuropathy: disease or INFLAMMATION and degeneration of the nerves. See PERIPHERAL NEUROPATHY.

Neuropsychologic Tests: tests designed to measure certain aspects of brain function, such as memory, concentration, attention and visual/motor skills.

Neurotransmitter: a substance secreted by excited nerve cells (NEURONS) that conveys the nerve signal to another nerve cell across the gap, or synapse, between the two cells.

Neutralizing Antibody: ANTIBODIES that can directly block the infective capacity of a microorganism, particularly a VIRUS' ability to penetrate cells.

Neutrexin: see TRIMETREXATE.

Neutropenia: a shortage of NEUTROPHILS in the blood.

Neutrophil: a type of GRANULOCYTE that is especially protective against bacterial and fungal infections. Neutrophils are also called polymorphonuclear cells (PMNs) because of their internal structure.

Nevirapine (Viramune): Boehringer Ingelheim's NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR (NNRTI). Nevirapine is FDA-approved for treatment of HIV-infected adults in combination with NUCLEOSIDE ANALOGS. Possible SIDE EFFECTS include severe rash, fever and liver impairment. Nevirapine interacts with many other drugs.

New Drug Application (NDA): an application to the FDA asking for approval to market a new drug.

NGF: see NERVE GROWTH FACTOR.

NHL: see NON-HODGKIN'S LYMPHOMA.

NIAID: see NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES.

NIH: see NATIONAL INSTITUTES OF HEALTH.

NIMH: see NATIONAL INSTITUTE OF MENTAL HEALTH.

Nizoral: see KETOCONAZOLE.

NK Cell: see NATURAL KILLER CELL.

NNRTI: see NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR.

Noncompleter Equals Failure (NC=F): the most conservative type of analysis in which participants who drop out of a CLINICAL TRIAL are considered to have failed therapy.

Noncompliant: refers to a patient who is unwilling or unable to follow a treatment REGIMEN as prescribed.

Non-Hodgkin's Lymphoma (NHL): a LYMPHOMA made up of B CELLS and characterized by nodular or diffuse tumors that may appear in the stomach, liver, brain or BONE MARROW. After KAPOSI'S SARCOMA, NHL is the most common opportunistic cancer in people with AIDS.

Non-Nucleoside Reverse Transcriptase Inhibitor (NNRTI): a member of a class of compounds, including DELAVIRDINE, NEVIRAPINE and EFAVIRENZ, that acts to directly combine with and block the action of HIV's REVERSE TRANSCRIPTASE enzyme. In contrast, NUCLEOSIDE ANALOGS block reverse transcriptase by capping the unfinished DNA chain that the ENZYME is constructing.

Nonoxynol-9: an anti-microbial agent present in some spermicides and lubricants. Nonoxynol-9 has been shown to irritate mucosal linings, which may possibly facilitate HIV infection and its use is not recommended as an MICROBICIDE.

Non-Syncytium-Inducing HIV: see SYNCYTIUM; T-TROPIC HIV.

Norvir: see RITONAVIR.

NRTI: see NUCLEOSIDE ANALOG.

NSI Virus (Non-Syncytium-Inducing HIV): see SYNCYTIUM; T-TROPIC HIV.

NtRTI: see NUCLEOTIDE ANALOG.

Nucleic Acid Sequence-Based Amplification (NASBA): an ASSAY used to detect HIV VIRAL LOAD in blood PLASMA.

Nucleoside: a combination of one of five single or double ringed "bases" and a sugar (ribose for RNA or deoxyribose for DNA). These molecular units are the building blocks of DNA and RNA, the genetic material found in living organisms. Before being added to a DNA or RNA sequence, nucleosides must have a phosphate group added (see PHOSPHORYLATION).

Nucleoside Analog (Nucleoside Analog Reverse Transcriptase Inhibitor, NRTI): a type of ANTIVIRAL drug, such as AZT (ZIDOVUDINE), ddI (DIDANOSINE), ddC (DIDEOXYCYTIDINE) or d4T (STAVUDINE), whose structure constitutes a defective version of a natural NUCLEOSIDE. Nucleoside analogs may take the place of the natural nucleosides, blocking the completion of a viral DNA chain during infection of a new cell by HIV. The HIV enzyme REVERSE TRANSCRIPTASE is more likely to incorporate nucleoside analogs into the DNA it is constructing than is the DNA POLYMERASE that cells normally use for DNA construction.

Nucleoside Analog Reverse Transcriptase Inhibitor: see NUCLEOSIDE ANALOG.

Nucleotide: a building block of RNA and DNA that consists of a base, a sugar, and a phosphate group. A phosphorylated nucleoside (see NUCLEOSIDE and PHOSPHORYLATION).

Nucleotide Analog: TENOFOVIR, ADEFOVIR, CIDOFOVIR and other ANTIVIRAL compounds that function exactly like NUCLEOSIDE ANALOGS but are pre-activated through the addition of a phosphate group during their synthesis. This PHOSPHORYLATION is supposed to enhance the drug levels and activity achieved within cells. Nucleotide analogs typically are active against a wide range of VIRUSES, including HERPES VIRUSES, HEPATITIS B and sometimes HIV.

Nystatin: an antifungal drug used primarily as a topical agent for oral CANDIDIASIS (THRUSH).

O

Observational Study: a study that does not involve randomization but where available data are nonetheless analyzed to make treatment comparisons. Observational studies are subject to bias, which may render their conclusions less reliable than those obtained by well controlled randomized CLINICAL TRIALS. Still, they may be useful for hypothesis generation and defining the natural history of disease.

Octoxynol: a chemical used in spermicides.

Octreotide Acetate (Sandostatin): an antidiarrheal drug.

Ocular: relating to the eye.

Odynophagia: pain when swallowing.

Off-Label: use of a drug for a disease or condition other than the INDICATION for which it was approved by the FDA. For example, many doctors prescribe PAROMOMYCIN for CRYPTOSPORIDIOSIS, although it is not approved for treating this disease.

OHL: see ORAL HAIRY LEUKOPLAKIA.

OI (Opportunistic Infection): see OPPORTUNISTIC CONDITION.

Oocysts: the first stage in the life cycle of a parasitic PROTOZOAN.

Open-Label Trial: a study in which both researchers and participants know what drugs a person is taking and at what dose. Compare BLINDED.

Opiate: a natural or synthetic derivative of opium that has similar ANALGESIC and sedative effects.

Opportunistic Condition: an infection or cancer that occurs especially or exclusively in persons with weak IMMUNE SYSTEMS due to AIDS, cancer or immunosuppressive drugs such as CORTICOSTEROIDS or CHEMOTHERAPY. KAPOSI'S SARCOMA (KS), PNEUMOCYSTIS CARINII PNEUMONIA (PCP), TOXOPLASMOSIS and CYTOMEGALOVIRUS are all examples of opportunistic conditions. Also more loosely termed "opportunistic infection"(OI).

Oral Candidiasis: see THRUSH.

Oral Hairy Leukoplakia (OHL): a white lesion that appears on the side of the tongue and inside cheeks. The lesion appears raised, with a ribbed or "hairy" surface. OHL occurs mainly in people with declining immunity and may be caused by EPSTEIN-BARR VIRUS infection.

Organic Molecule: a molecule that comes, or came, from a living thing.

Orphan Drug: a status granted by the FDA to unpatentable medications developed for rare diseases. Orphan drug status gives the drug's manufacturer a seven-year right to exclusively market the compound. This protection of unpatentable orphan drugs encourages their development by greatly increasing their profitability.

Osteoporosis: loss of bone density due to depletion of calcium and bone PROTEIN.

Oxandrin: see OXANDROLONE.

Oxandrolone (Oxandrin): an oral ANABOLIC STEROID approved by the FDA in 1962 as a general remedy for weight loss in a variety of conditions including CHRONIC infection. Now being studied as treatment for AIDS-related WASTING SYNDROME.

Oxidation: a chemical reaction resulting from exposure to oxygen or other electron-seizing atoms or molecular combination of atoms (see FREE RADICALS). On the cellular level, oxidative reactions are the source of energy, but free radicals and other oxidizing agents can damage cellular components, such as membranes, and interfere with cells' regulatory systems.

Oxidative Stress: a highly oxidized environment within cells that is thought to promote HIV replication because cells are forced into a highly activated state due to loss of control of their regulatory systems.

Oxymetholone (Anadrol): an anabolic-androgenic STEROID used to treat ANEMIA.

P

p24: the main HIV core PROTEIN. It can be measured in blood and other BODILY FLUIDS.

p24 Antigen Test: a test that checks for the presence of HIV's capsid PROTEIN, P24, in SERUM. Unlike ANTIBODY tests, the p24 antigen test detects HIV directly.

P450 Enzyme System: see CYTOCHROME P450.

P Value: the probability that experimental results are attributable to chance alone. The lower the p-value, the more likely it is that the results are not due to chance. A p-value of less than 0.05 is considered statistically significant.

Package Insert: an FDA approved form containing the INDICATIONS, SIDE EFFECTS and other relevant information known about a drug, found inside any box of prescription drugs on pharmacy shelves.

Paclitaxel (Taxol): a chemotherapeutic drug extracted from the yew tree and used for the treatment of solid tumors. Taxol is a treatment for KAPOSI'S SARCOMA. It works by inhibiting cell division and has a long list of SIDE EFFECTS, in particular BONE MARROW SUPPRESSION (resulting in NEUTROPENIA).

Palliative: offering relief of symptoms or comfort without ameliorating the underlying disease process.

Pancreatic Enzymes: PROTEINS made by the pancreas that aid in digestion.

Pancreatitis: INFLAMMATION of the pancreas. Pancreatitis, an occasional SIDE EFFECT of ddI (DIDANOSINE), can result in severe abdominal pain and death. Its onset can be predicted by rises in blood levels of the pancreatic enzyme AMYLASE as well as increases in blood TRIGLYCERIDES.

Pancytopenia: low levels of all types of blood cells.

Pap Smear: a microscopic examination of the surface cells of the CERVIX, usually conducted on scrapings from the cervical opening. This assay is used to detect tissue changes that could be forerunners of cervical cancer.

Papillomavirus: the large group of papova VIRUSES that includes the cause of genital warts or condylomata (see CONDYLOMA ACUMINATUM). See also HUMAN PAPILLOMAVIRUS.

Papule: a small elevation or bump on the skin.

Parallel Track: a general term for a process for distributing experimental HIV and AIDS drugs to people who are otherwise unable to participate in ongoing CLINICAL TRIALS. It may function as a safety study under a national protocol that tells individual physicians how to administer the drug and what information to collect on their patients' experience. It is similar to TREATMENT INVESTIGATIONAL NEW DRUG, but can be instituted at an earlier phase in the drug's development, as soon as safety is demonstrated. See also EXPANDED ACCESS.

Parenteral: outside the digestive tract. This term refers to INTRAVENOUS, SUBCUTANEOUS and other non-oral modes of administering medications and therapies. See also ENTERAL.

Paresthesia: abnormal sensations such as burning or tingling ("pins and needles"). Paresthesia may constitute the first symptoms of PERIPHERAL NEUROPATHY, or it may be a limited drug SIDE EFFECT that does not worsen with time.

Paromomycin (Humatin): an ANTIBIOTIC in pill form used for suppression of infection by intestinal parasites, including AIDS-related CRYPTOSPORIDIOSIS. Possible SIDE EFFECTS include stomach upset and diarrhea.

Passive Immunotherapy (PIT): a process in which individuals with advanced disease (who have low levels of HIV ANTIBODY production) are infused with PLASMA rich in HIV antibodies or an IMMUNOGLOBULIN concentrate (HIVIG) made from such plasma. The plasma is obtained from ASYMPTOMATIC HIV-positive individuals with high levels of HIV antibodies.

Pathogen: any disease-provoking microorganism or material.

Pathogenesis: the manner in which a particular infectious MICROBE causes disease.

PBMC: see PERIPHERAL BLOOD MONONUCLEAR CELL.

PCP: see PNEUMOCYSTIS CARINII PNEUMONIA.

PCR: see POLYMERASE CHAIN REACTION.

PC-SOD: see LECITHINIZED SUPEROXIDE DISMUTASE.

Peak Level: the highest concentration of a drug in blood PLASMA, occurring soon after it is administered. Sometimes abbreviated as CMAX. Peak levels that are too high cause excess SIDE EFFECTS without necessarily enhancing the antimicrobial effects of the drug. See also TROUGH LEVEL.

Pegylated Interferon: INTERFERON that is attached to polyethylene glycol (PEG). Pegylation allows the interferon to last longer, thereby requiring less frequent administration. Two pegylated interferons are FDA approved to treat HEPATITIS C INFECTION, Peg-Intron and Pegasys.

Pelvic Inflammatory Disease (PID): a gynecological condition caused by an infection (usually sexually transmitted) that spreads from the vagina to the upper parts of a woman's reproductive tract in the pelvic cavity. PID takes different courses in different women, but can cause abscesses and constant pain almost anywhere in the genital tract. If left untreated, it can cause infertility or more frequent periods. Severe cases may invade the liver and kidneys, causing dangerous internal bleeding, lung failure and death.

Pentafuside: see ENFUVIRTIDE.

Pentam: see PENTAMIDINE.

Pentamidine (Pentam, NebuPent): an ANTIBIOTIC used in aerosol form as a prevention against PNEUMOCYSTIS CARINII PNEUMONIA (PCP) ("AEROSOLIZED pentamidine") and used intravenously to treat PCP. Possible SIDE EFFECTS of inhaled pentamidine include coughing, wheezing, shortness of breath and fatigue. Among the side effects of injected pentamidine are low blood sugar, PANCREATITIS, hypotension and kidney disease.

Pentoxifylline (Trental): a drug that reduces levels of TUMOR NECROSIS FACTOR (TNF). Pentoxifylline is FDA-approved for treatment of leg cramps and poor circulation. Possible SIDE EFFECTS include nausea and other digestive upset, dizziness and headache. CLINICAL TRIAL results in HIV have not been promising.

Peptide: a short sequence of AMINO ACIDS.

Percutaneous: through the skin.

Perinatal: around the time of birthæshortly before to shortly afterward.

Perinatal Transmission: see VERTICAL TRANSMISSION.

Perineum: the area between the anus and the scrotum (in men) or the vulva (in women).

Perioral Parasthesia: tingling in the mouth.

Peripheral Blood Mononuclear Cell (PBMC): circulating white blood cells with one nucleus, mainly LYMPHOCYTES and MONOCYTES.

Peripheral Neuropathy: nerve damage characterized by sensory loss, pain, muscle weakness and wasting of muscle in the hands or legs and feet. It may start with burning or tingling sensations or numbness in the toes and fingers. In severe cases, paralysis may result. Peripheral neuropathy may arise from an HIV-related condition or be the SIDE EFFECT of certain drugs, in particular some of the NUCLEOSIDE ANALOGS and CHEMOTHERAPY.

Peripherally Inserted Central Catheter (PICC Line): a CATHETER inserted into an arm vein and used for periods of up to three months. This catheter does not need to be surgically implanted and can be inserted at home by a trained nurse.

Persistent Generalized Lymphadenopathy (PGL): a condition common in people with HIV in which multiple LYMPH NODES are swollen for a long period of time.

Peyer's Patch: one of the large number of intestinal lymph nodules, which exist either alone or in aggregates.

PGL: see PERSISTANT GENERALIZED LYMPHADENOPATHY.

Phagocyte: a scavenger white blood cell that binds to and destroys foreign material, dead tissue and cells.

Phagocytosis: the process by which white blood cells such as MACROPHAGES engulf and destroy foreign material, dead tissues and cells.

Pharmacokinetics: the extent that the body is able to absorb, distribute and eliminate a drug over time.

Pharyngeal: relating to the throat.

Phase I Trial: the earliest stage CLINICAL TRIAL for studying an EXPERIMENTAL DRUG in humans, including first use in humans. Phase I trials generally involve a small number of individuals. Phase I trials provide an initial evaluation of a drug's safety and PHARMACOKINETICS - how the drug is absorbed, what tissues it reaches and how long it takes to leave the body. Such studies also usually test various doses of the drug (dose-ranging) to obtain an indication of the tolerable doses to use in later studies.

Phase I/II Trial: a trial designed to be decisive in a company's decision to develop an EXPERIMENTAL DRUG and may include evaluation of the drug's ACTIVITY. A "go/no go" trial.

Phase II Trial: a more advanced stage CLINICAL TRIAL that follows the PHASE I trials. A phase II trial gathers information on an EXPERIMENTAL DRUG's EFFICACY and safety. Data often are based on laboratory ASSAYS that provide quick, but indirect measurements of a drug's effect on disease (see SURROGATE MARKER). Phase II trials often involve a hundred people or more who are randomly assigned to take either the experimental drug or a "CONTROL" (the standard treatment for the disease or PLACEBO). Usually the trial is DOUBLE-BLINDED, which means that no one knows who is getting the experimental drug until the trial is completed and the results are analyzed.

Phase III Trial: an advanced stage CLINICAL TRIAL designed to conclusively show how well a drug works as compared to other treatments. Phase III trials are large and frequently involve multiple sites. They need to rely on definitive measures of effectiveness rather than SURROGATE MARKERS. Optimally a phase III trial would show whether a new drug extends survival or otherwise improves the health of patients on treatment (clinical improvement), but the FDA considers long-term reductions in VIRAL LOAD as proof of efficacy for anti-HIV medications. These studies generally last longer and are larger than PHASE II trials.

Phase IV Trial: a trial designed to evaluate the long-term safety and EFFICACY of a drug for a given INDICATION, as well as other uses for the drug, usually carried out as a post-marketing study after a drug has been approved by the FDA.

PhenoSense HIV: ViroLogic's PHENOTYPIC ASSAY.

Phenotype: an organism's functional capabilities and outward appearance. It is the physical expression of the GENOTYPE.

Phenotypic Assay: a test that measures some aspect of an organism's functions, for example, the amount of a certain drug needed to inhibit the growth of an HIV ISOLATE in a test-tube culture. If HIV has developed RESISTANCE to a certain drug, then higher than the normally administered amounts of that drug will be necessary to inhibit viral activity. PHENOSENSE and ANTIVIROGRAM are commercially available in the United States. See also GENOTYPIC ASSAY.

Phosphorylation: the addition of a phosphate group (phosphorus plus four oxygen atoms) to an ORGANIC MOLECULE. Phosphorylation is essential to many cellular processes, and it is one step required to convert NUCLEOSIDE ANALOGS into their active, triphosphate form.

Photosensitivity: heightened skin response to sunlight or ultraviolet light (rapid burning when exposed to the sun).

PHS: see PUBLIC HEALTH SERVICE.

PI: see PROTEASE INHIBITOR.

PICC Line: see PERIPHERALLY INSERTED CENTRAL CATHETER.

PID: see PEVLIC INFLAMMATORY DISEASE.

Pill Burden: refers to the number and size of pills required for a particular treatment or REGIMEN.

Pilot Trial: a feasibility study intended to gain preliminary information about EFFICACY, safety or a particular research hypothesis; they may be PHASE I or PHASE II TRIALS. Pilot trials are used to work out the details for further CLINICAL TRIALS.

Pioglitazone: a drug used to lower blood TRIGLYCERIDES.

PIT: see PASSIVE IMMUNOTHERAPY.

Placebo: a comparison substance against which EXPERIMENTAL DRUGS are sometimes compared. A placebo traditionally is an inactive substance resembling the experimental treatment. In placebo-controlled trials, the control group takes placebo, while the test group takes the experimental drug. Either group may receive a standard therapy in addition. Many placebo-controlled trials are also DOUBLE-BLINDED, which means that neither doctors nor patients know who is receiving drug or placebo.

Placebo-Controlled Trial: see PLACEBO.

Placenta: a temporary organ in the uterus that allows a fetus to receive nutrients, oxygen and other substances (such as medications) from the mother and to eliminate carbon dioxide and other wastes.

Plasma: the watery, yellowish fluid that carries white and red blood cells and PLATELETS through the circulatory system. Plasma is prepared for laboratory ASSAYS by treating whole blood with an anticoagulant and then centrifuging the fluid to separate out the cells.

Platelet: a small, specialized cell fragment that triggers the clotting of blood so that damaged vessels stop bleeding. Normally 150,000 to 300,000 platelets are found in one milliliter of blood, but platelet counts can become sharply depleted during HIV infection. (See IMMUNE THROMBOCYTOPENIC PURPURA.) Another function of platelets is to collect ANTIGEN-ANTIBODY complexes in the blood. Platelets coated with such complexes are eliminated in the SPLEEN. The source of platelets is the megakaryocyte cells in the BONE MARROW.

PML: see PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY.

PMN (Polymorphonuclear) Cell: see NEUTROPHIL.

PMPA: see TENOFOVIR.

Pneumocystis Carinii Pneumonia (PCP): a lung infection caused by Pneumocystis carinii (which is either a PROTOZOA or FUNGUSæit has characteristics of both). P. carinii grows rapidly in the lungs of people with AIDS and was formerly the leading AIDS-related cause of death. P. carinii infection sometimes may occur elsewhere in the body (skin, eye, SPLEEN, liver or heart).

Pol Gene: an HIV GENE that contains the genetic code for its viral ENZYMES.

Polycythemic: high levels of red blood cells.

Polymerase: an ENZYME that makes copies of genetic material.

Polymerase Chain Reaction (PCR): an IN VITRO process that is used to amplify (create unlimited numbers of) selected sections of DNA or RNA.

Polymerase Chain Reaction (PCR) Test: a very sensitive test that measures the presence or amount of RNA or DNA of a specific organism or VIRUS (for example, HIV or CYTOMEGALOVIRUS) in the blood or tissue. The result of an HIV PCR test is often referred to as VIRAL LOAD. PCR tests such as Hoffmann-La Roche's Amplicor quantitative PCR assay are used to gauge HIV disease progression and the effect of particular treatments on HIV infection. See also BRANCHED DNA (bDNA) ASSAY.

Polymorphonuclear (PMN) Cell: see NEUTROPHIL.

Polyneuropathy: a disease process involving a number of peripheral nerves.

Polyprotein: a string of PROTEINS created during viral replication. The ENZYME PROTEASE breaks down the polyprotein into smaller components that are used to create new VIRUS particles.

Poppers: see AMYL NITRATE.

Post-Exposure Prophylaxis: administering drug treatment to prevent disease in an individual after exposure to an infectious organism. For example, guidelines have been established for post-exposure prophylaxis of health care providers who have been exposed to HIV through needle sticks.

Post-Exposure Prophylaxis Registry: a prospective surveillance program designed to collect data on utilization, safety and outcome on the use of ANTIVIRAL agents in persons who receive POST-EXPOSURE PROPHYLAXIS for nonoccupational HIV exposure.

Post-Marketing Study: see PHASE IV TRIAL.

Postpartum: after childbirth.

Potentiation: an increase in ACTIVITY or EFFICACY, such an interaction between drugs that results in a SYNERGYSTIC effect.

PPD Test: see PURIFED PROTEIN DERIVATIVE TEST.

Pravachol (Pravastatin): a LIPID-lowering drug.

Pravastatin: see PRAVACHOL.

Preclinical: refers to the testing of EXPERIMENTAL DRUGS in the test tube or in animals - the testing that occurs before trials in humans may be carried out.

Prepartum: before childbirth, during pregnancy.

Prevalence: the total number of people in a specific population who are living with a particular condition or disease at a given time. See also INCIDENCE.

Preventive Vaccine: a VACCINE created to prevent a disease from occurring. Compare THERAPEUTIC VACCINE.

Primary Endpoint: see CLINICAL ENDPOINT.

Primary HIV Infection: the first few months after HIV infection. This initial infection precedes SEROCONVERSION and is sometimes characterized by fever, sore throat, headache, skin rash and swollen glands. Also called acute infection.

Primary Prophylaxis: see PROPHYLAXIS.

Principal Investigator: the head researcher responsible for organizing and overseeing a CLINICAL TRIAL.

PRN: a term used on prescriptions to mean "take as needed," from the Latin phrase pro re nata.

Probenecid: a drug that enhances the kidney's excretory functions. Patients receiving CIDOFOVIR for CYTO-MEGALOVIRUS (CMV) must take probenecid and INTRAVENOUS hydration with saline solution in order to protect the kidneys from damage caused by cidofovir buildup within kidney cells.

Prochlorperazine (Compazine): an ANTIEMETIC (anti-nausea) drug.

Procrit: see EPOGEN.

Prodrug: a compound that is converted within the body into the active form that has medical effects. For example, VALACYCLOVIR is a prodrug of ACYCLOVIR. Prodrugs are useful when the active drug may be too toxic to administer systemically, the active drug is absorbed poorly by the digestive tract or the body breaks down the active drug before it reaches its target.

Progesterone: a female HORMONE with anti-ESTROGEN effects. A synthetic version is used as a contraceptive.

Prognosis: the probable future course of disease in a patient.

Progressive Multifocal Leukoencephalopathy (PML): a rapidly debilitating OPPORTUNISTIC CONDITION caused by the "JC" virus, a polyoma virus that infects brain tissue and causes damage to the CENTRAL NERVOUS SYSTEM. Symptoms vary from patient to patient but include loss of muscle control, paralysis, blindness, problems with speech and an altered mental state. PML can lead to coma and death. There are no standard treatments for this disease.

Proinflammatory Cytokines: soluble chemical messengers produced by white blood cells (LEUKOCYTES) that trigger an INFLAMMATORY IMMUNE RESPONSE and may, as a SIDE EFFECT, stimulate HIV, which only infects and replicates in activated cells. See both TUMOR NECROSIS FACTOR ALPHA and INTERLEUKIN-2.

Proleukin: see INTERLEUKIN-2.

Prophylaxis: treatment to prevent the onset of a particular disease (PRIMARY PROPHYLAXIS) or recurrence of symptoms in an existing infection that has been brought under control (SECONDARY PROPHYLAXIS or MAINTENANCE THERAPY).

Prospective Study: refers to studies designed to follow the progress of a COHORT forward in time, rather than analyzing data from previous research. Compare RETROSPECTIVE STUDY.

Protease: an ENZYME that breaks apart PROTEINS. HIV's protease enzyme splits long strands of viral protein into the separate proteins constituting the viral core and the viral enzymes it contains. HIV protease acts at the stage when new virus particles are budding off a cell membrane.

Protease Inhibitor: a drug that binds to and blocks HIV PROTEASE from working, thus preventing the production of new functional viral particles.

Protease Paunch: an informal term used to describe an accumulation of fat in the abdomen. The SYNDROME is possibly linked to treatment with PROTEASE INHIBITORS. See also LIPODYSTROPHY.

Protein: large molecules made up of long sequences of AMINO ACIDS. Some HORMONES and all ENZYMES and cellular structural components are proteins. Three-fourths of the dry weight of most cells consists of proteins.

Proteinuria: the presence of PROTEIN in the urine.

Protocol: a plan that describes the plan details of a CLINICAL TRIAL, its rationale, goal, the drugs involved, their dosage levels, treatment duration and who and how many may participate.

Protozoa: a large group of one-celled (unicellular) animals, including amoebas. Some protozoa cause parasitic OPPORTUNISTIC CONDITIONS in people with AIDS, notably TOXOPLASMOSIS and CRYPTOSPORIDIOSIS.

Provirus: the status of HIV when it exists as proviral DNA inserted into the GENOME of the host cell.

Prozac: see FLUOXETINE.

Pruritic: itchy.

Psychostimulants: a class of drugs used to stimulate the CENTRAL NERVOUS SYSTEM. Psychostimulants are sometimes used in

the treatment of DEPRESSION. These medications are very addictive and may activate an addiction to stimulants (amphetamines) in a patient in recovery. SIDE EFFECTS include insomnia, loss of appetite, loss of weight and paranoia.

Psychotropic Drugs: drugs that affect an individual's behavior or mental functions.

Public Health Service (PHS): a federal agency that is part of the Department of Health and Human Services and oversees public health. The NATIONAL INSTITUTES OF HEALTH and CENTERS FOR DISEASE CONTROL belong to the Public Health Service.

Pulmonary: refers to the lungs.

Purified Protein Derivative (PPD) Test: a simple skin test used to detect prior exposure to TUBERCULOSIS (TB). PPD is injected under the skin of the forearm. After 48 to 72 hours, the injection site will exhibit a red, hard bump if a person has been infected with TB.

PWA: person or people with AIDS.

PWHIV: person or people with HIV.

Pyrimethamine (Daraprim): an oral antiprotozoa drug used in combination with SULFADIAZINE or CLINDAMYCIN to treat TOXOPLASMOSIS. Its many possible SIDE EFFECTS include severe allergic reactions and rashes, ANEMIA, LEUKOPENIA, THROMBOCYTOPENIA, insomnia and diarrhea.

Pyrogenic: fever-causing.

Q

q8h: an abbreviation used on prescriptions that means "take every 8 hours."

qd: an abbreviation used on prescriptions that means "take once a day." From the Latin quaque die.

Qualitative Assay: a test that determines the presence or absence of a substance.

Quantitative Assay: a test that measures the amount of a substance in a specified sample size.

Quiescent: inactive, resting, in a state of LATENCY.

Quinolone: a class of synthetic ANTIBIOTIC drugs with broad spectrum antibacterial activity; examples include CIPROFLOXACIN, ofloxacin and sparfloxacin.

R

Randomized Trial: a trial in which the participants are randomly assigned to receive their treatment, which could be a study medication, a standard treatment, or PLACEBO. Randomization minimizes the differences among groups by distributing people with particular characteristics among all the trial ARMS without BIAS.

RANTES: a CHEMOKINE that binds to the CCR5 RECEPTOR site and interferes with HIV's fusion with uninfected cells.

RBC: red blood cell.

Reactivation: when a previously latent infection becomes active again.

Receptor: specific PROTEINS, usually located on the surface of a cell, that bind with ANTIGENS, ANTIBODIES and chemical messengers. HIV binds with the CD4 portion of the T CELL receptor plus one of the CHEMOKINE receptors, usually either CCR5 or CXCR-4, in order to enter a cell.

Rechallenge: to administer a substance (drug, pathogen) a second time.

Recombinant: refers to compounds produced by laboratory or industrial cultures of genetically engineered living cells. A new GENE has been added to a cell's gene set to enable clones of the cell to produce large quantities of the desired compound. Recombinant compounds often are versions of naturally occurring substances that exist in low amounts in their original source. An example of a recombinant agent used in AIDS is recombinant HUMAN GROWTH HORMONE for AIDS WASTING SYNDROME.

Rectum: the terminal section of the large intestine, including the anus.

Reference Virus: a "standard" VIRUS used for comparison. For example, in HIV RESISTANCE testing the resistance or SUSCEPTIBILITY of a patient's virus is compared to that of a reference virus. See also FOLD RESISTANCE.

Refractory: refers to disease that is resistant to treatment.

Regimen: a prescribed drug treatment plan, specifying which drugs are to be used, in what doses and on what schedule.

Registration Trial: a trial designed to provide solid support for a drug's approval by the FDA.

Remission: a period when the signs and symptoms of a disease have been eliminated through treatment or by the IMMUNE RESPONSE. A disease may be in remission without a complete cure having been effected.

Remune: a THERAPEUTIC VACCINE consisting of killed HIV stripped of its ENVELOPE PROTEIN and mixed with a mineral oil-based ADJUVANT known as Incomplete Freund's Adjuvant. Proposed in the 1980s by Jonas Salk, the vaccine has shown little evidence of efficacy in clinical trials.

Renal: refers to the kidneys.

Repertoire: the full range of ANTIGEN recognized by the T and B CELLS that make up an individual's IMMUNE SYSTEM. Each clone of such cells targets a particular ANTIGEN. In AIDS, some scientists believe, when the CD4 CELLS are depleted to a certain point, entire clones may have been lost, thus reducing the CD4 cell repertoire leaving people vulnerable to OPPORTUNISTIC CONDITIONS. Increasing CD4 counts through treatment may not bring back the full range of cells, but rather multiply only those that are left. Various IMMUNE-BASED THERAPIES are being studied in an attempt to restore the full repertoire.

Rescriptor: see DELAVIRDINE.

Rescue Therapy: see SALVAGE THERAPY.

Reservoir: denotes a class of cells in the body that may harbor HIV long after antiretroviral therapy commences. Examples of such reservoirs include latently or chronically infected MACROPHAGES and LYMPHOCYTES. These are unaffected by current agents, which do not attack the HIV PROVIRUS within infected cells' nuclei. Other possible reservoirs are really SANCTUARIES, and include tissues such as the brain and testes, where drugs do not penetrate easily.

Residual Disease: a disease that has not been eradicated.

Resistance: reduction in a PATHOGEN's SENSITIVITY to a particular drug. Resistance is thought to result mainly from genetic MUTATION. In HIV, such mutations can change the structure of viral ENZYMES and PROTEINS so that an ANTIVIRAL drug cannot bind with them as effectively. Resistance detected by searching a pathogen's genetic makeup for mutations thought to confer lower SUSCEPTIBILITY is called genotypic resistance. Resistance found by successfully growing laboratory cultures of the pathogen in the presence of a drug is called phenotypic resistance. High-level resistance reduces a drug's virus-suppressing activity hundreds of times. Low-level resistance represents only a few-fold reduction in drug effectiveness. Depending on the toxicity of the drug, low-level resistance may be overcome by using higher doses of the drug in question. See also GENOTYPE, GENOTYPIC ASSAY, PHENOTYPE, PHENOTYPIC ASSAY.

Resistance Exercise: forms of exercise, such as weight lifting, that increase LEAN BODY MASS.

Resting CD4 Cell: a CD4 CELL that is not dividing. Compare ACTIVE CD4 CELL.

Reticuloendothelial System: the collection of MACROPHAGES and other white blood cells (LEUKOCYTES) that ingest infectious organisms such as BACTERIA and VIRUSES. It also includes the SPLEEN, liver and lymphoid system.

Retina: the multilayered, light-sensitive membrane lining the inner eyeball that sends visual images to the brain via the optic nerve.

Retinal Detachment: a condition in which a portion of the retina becomes separated from the inner wall of the eye. Retinal detachment can result from retinal disease such as CYTOMEGALOVIRUS (CMV) RETINITIS or GANCICLOVIR implants (see INTRAOCULAR IMPLANT). The condition can rapidly lead to vision loss, but is treatable by various surgical methods and by adding silicone to the eye's VITREOUS HUMOR to increase the pressure on the RETINA.

Retinitis: INFLAMMATION of the RETINA, usually caused by infections such as CYTOMEGALOVIRUS (CMV). If left untreated, it can lead to blindness.

Retrospective Study: a study that tries to answer a new medical question by reviewing data gathered in the past. A retrospective study cannot be rigorously designed and risks attributing effects to the wrong causes. Compare PROSPECTIVE STUDY.

Retrovir: see ZIDOVUDINE.

Retrovirus: a type of VIRUS that, when not infecting a cell, stores its genetic information on a single-stranded RNA molecule instead of the more usual double-stranded DNA. HIV is an example of a retrovirus. After a retrovirus penetrates a cell, it constructs a DNA version of its genes using a special ENZYME, REVERSE TRANSCRIPTASE. This DNA can then become incorporated into the cell's genetic material.

Rev: a regulatory PROTEIN produced by HIV within infected cells. Rev helps transport HIV RNA sequences (messenger RNA) out from the nucleus into the cell's cytoplasm, where it directs construction of proteins for new VIRUS particles.

Reverse Resistance: See HYPERSUSCEPTIBILITY.

Reverse Transcriptase (RT): a viral ENZYME that constructs DNA from an RNA template, which is an essential step in the life cycle of a RETROVIRUS such as HIV. The RNA-based GENES of HIV and other retroviruses must be converted to DNA if they are to integrate into the cellular GENOME.

Reverse Transcriptase Inhibitor: a drug that blocks a RETROVIRUS' replication by interfering with REVERSE TRANSCRIPTASE. See also NUCLEOSIDE ANALOG and NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR.

Ribavirin: a NUCLEOSIDE ANALOG approved as a treatment for respiratory syncytial VIRUS. Ribavirin also has shown ACTIVITY against HEPATITIS C and is used in combination with ALPHA INTERFERON. Its use in HIV infection is highly controversial.

Ribonuclease: one of two active regions of the REVERSE TRANSCRIPTASE ENZYME. After reverse transcriptase uses HIV's RNA to create a single strand of DNA, ribonuclease severs it from the original RNA.

Ribonucleic Acid (RNA): a single-stranded molecule composed of NUCLEOTIDE sequences. It is similar in basic structure to half of the double-stranded DNA. In cells, RNA transmits the code from the DNA-based GENES and instructs the cells' chemical machinery to produce structural PROTEINS and ENZYMES. The RNA segments in the cells represent copies of portions of the DNA sequences in the nucleus. In RETROVIRUSES, RNA is the sole repository of the viral genes.

Ribonucleotide Reductase: a viral ENZYME that creates building blocks of DNA by breaking down ribonucleotides. HYDROXYUREA inhibits ribonucleotide reductase.

Ribozyme: an experimental RECOMBINANT RNA/ENZYME combination designed to fit onto and cleave specific viral or cancerous genetic sequences from a cell's DNA. The GENE for an anti-HIV ribozyme may possibly be inserted into a cell to protect it from the VIRUS' activity. See also GENE THERAPY.

Rifabutin (Mycobutin): an oral drug approved by the FDA for preventing MYCOBACTERIUM AVIUM COMPLEX (MAC) in people with advanced HIV infection. Rifabutin is also used in combination with other drugs for the treatment of active MAC and TUBERCULOSIS infections. Possible SIDE EFFECTS include NEUTROPENIA, eye and muscle irritation and a brown-orange discoloration of skin and urine.

Rifampin: an ANTIBIOTIC used in COMBINATION THERAPY for treatment of MYCOBACTERIAL infections such as TUBERCULOSIS and MYCOBACTERIUM AVIUM COMPLEX. Rifampin cannot be used in conjunction with PROTEASE INHIBITORS.

Ritonavir (Norvir): a PROTEASE INHIBITOR from Abbott more commonly used to inhibit liver enzyme metabolism of other protease inhibitors. It is FDA-approved for adults and children over two years old. There are at least 25 drugs that should not be taken with ritonavir and many more that will require changes in dosing. SIDE EFFECTS include nausea, vomiting and diarrhea. Ritonavir interacts with many other medications.

RNA: see RIBONUCLEIC ACID.

Roferon: see ALPHA INTERFERON.

Rosiglitatzone: a drug used to lower blood TRIGLYCERIDES.

RT: see REVERSE TRANSCRIPTASE.

Rupture of Membranes: refers to the breaking of the amniotic sac (or "bag of waters") surrounding the fetus in a pregnant woman.

Ryan White CARE Act: federal legislation passed in 1990 to fund services for people with HIV/AIDS.

S

Saint John's Wort: an herb that is often used to treat depression or anxiety. A recent study found that St. John's Wort significantly decreases blood levels of INDINAVIR, and it probably does the same with other PROTEASE INHIBITORS, NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITORS and several other drugs. See also HYPERICIN.

Salvage Therapy: a somewhat loosely defined term that refers to drug REGIMENS used after initial therapies have failed. Also called rescue therapy.

Sanctuary: a tissue or organ like the brain and testes into which drugs penetrate at a low rate. Because of the reduced drug levels in such tissues, they may harbor replicating HIV long after the commencement of potent ANTIVIRAL treatment.

Sandostatin: see OCTREOTIDE ACETATE.

Saquinavir (Invirase, Fortovase): a PROTEASE INHIBITOR from Hoffman-La Roche. It is FDA-approved for HIV infection in combination with NUCLEOSIDE ANALOGS. Invirase, the first formulation of saquinavir, had low anti-HIV activity in the body because it was poorly absorbed in the intestines and rapidly metabolized by the liver. Combining saquinavir with RITONAVIR raises its blood levels by ten-fold, sufficient for ANTIVIRAL therapy. A later formulation of saquinavir (Fortovase), packaged in a soft gel capsule, increased intestinal absorption four times. The recommended dose of Fortovase is twice the recommended dose of the Invirase, leading to an eight-fold increase in blood levels. SIDE EFFECTS include nausea, diarrhea and abdominal pain.

Sarcoma: a MALIGNANT tumor of the skin and soft tissue.

Scavenger Cells: any one of a diverse group of white blood cells (LEUKOCYTES) with the capacity to engulf and destroy foreign material, dead tissues and cells. See also PHAGOCYTE, PHAGOCYTOSIS.

Schedule I Drug: a drug that, according to the U.S. Department of Justice, has a high potential for abuse, has no currently accepted medical use, and lacks safety data. Currently, heroin, LSD and marijuana are Schedule I drugs.

Schedule II Drug: a drug that, according to the U.S. Department of Justice, has a high potential for abuse, has a currently accepted medical use (possibly with severe restrictions), and, if abused, could lead to severe physical or psychological dependence. Currently, morphine, cocaine and METHADONE are Schedule II drugs.

Schedule III Drug: a drug that, according to the U.S. Department of Justice, has a potential for abuse, has an accepted medical use, and, if abused, could lead to moderate or low physical or psychological dependence. Currently, ANABOLIC STEROIDS and codeine are Schedule III drugs.

SDF-1: see STROMAL CELL-DERIVED FACTOR.

Second Generation: a drug that is in the same class (e.g., PROTEASE INHIBITORS or NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITORS) as an already approved drug (typically made by the same company) but that promises significant benefit over the former.

Secondary Infection: an infection that occurs while already infected with a different, related infection.

Secondary Prophylaxis: see PROPHYLAXIS.

Selective Serotonin Reuptake Inhibitor (SSRI): a class of antidepressant drugs that regulates levels of SEROTONIN. Among these drugs are Prozac (FLUOXETINE) and Zoloft (SERTRALINE). SSRIs are not usually sedating and may alleviate CHRONIC constipation. Possible SIDE EFFECTS include nausea and sexual dysfunction.

Seminal: of or related to semen.

Sensitivity: 1. the degree to which an organism is affected by a drug. See RESISTANCE. 2. A statistical measurement of how accurate a test is, eg. how likely it is that an antibody test will accurately provide a positive result when a person is HIV- positive. Compare to SPECIFICITY.

Sepsis: the presence of disease-causing organisms or their toxins in the blood or tissues and the associated inflammatory response to the infection.

Septicemia: a serious condition caused by large numbers of BACTERIA in the blood. This condition can be fatal. Symptoms are a sudden drop in blood pressure and changes in heart rate and temperature.

Septra: see TRIMETHOPRIM/SULFAMETHOXAZOLE.

Sequencing: sequential use of drugs from the same class (e.g., PROTEASE INHIBITORS or NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITORS). Due to CROSS-RESISTANCE, there is concern about whether drugs in the same class can be sequenced and, if they can, how to best sequence them.

Seroconversion: development of detectable ANTIBODIES to HIV in the blood as a result of infection. It normally takes several weeks to several months for antibodies to the VIRUS to develop after HIV transmission. When antibodies to HIV appear in the blood, a person will test positive in the standard ENZYME-LINKED IMMUNOSORBENT ASSAY (ELISA) test for HIV.

Seronegative: testing negative for an infection, such as HIV. Not having ANTIBODIES to a microorganism. A person can be seronegative and still have the infection in question since antibodies take some time to develop (it can take six months for HIV antibodies to become detectable).

Seropositive: testing positive for an infection, such as HIV.

Seroprevalence: the rate of positive SEROSTATUS within a population at a given time point.

Serostatus: the condition of having or not having detectable ANTIBODIES to a MICROBE in the blood as a result of infection. One may have either a positive or negative serostatus.

Serostim: see HUMAN GROWTH HORMONE.

Serotonin: a naturally occurring substance found in the brain and intestines that is released when blood vessel walls are damaged. It acts as a blood vessel constrictor and inhibits gastric secretions. Serotonin is also a NEUROTRANSMITTER. See SELECTIVE SEROTONIN REUPTAKE INHIBITOR.

Sertraline (Zoloft): an antidepressant.

Serum: the yellowish, cell-free liquid portion of the blood formed when a sample of whole blood is allowed to clot. See also PLASMA.

Serum Glutamic Pyruvic Transaminase (SGPT): see ALANINE AMINOTRANSAMINASE.

Set Point: the rate of HIV replication at steady state, after PRIMARY INFECTION. It is usually established by six months after SEROCONVERSION and is evaluated using the VIRAL LOAD test.

SGOT: see ASPARTATE AMINOTRANSAMINASE.

SGPT: see ALANINE AMINOTRANSAMINASE.

Shedding: the release of infectious particles.

Shingles (Herpes Zoster): a skin condition caused by reactivation of a VARICELLA ZOSTER VIRUS (VZV) infection, usually acquired in childhood (when it appears as chicken pox). Shingles consists of painful blisters on the skin that follow the path of individual nerves. The blisters generally dry and scab, leaving minor scarring. Standard treatment is with FAMCICLOVIR or ACYCLOVIR. See also HERPES VIRUS.

SI Virus: syncytia-inducing HIV. See SYNCYTIUM.

Side Effect: any reaction that results from a drug or therapy. The term usually refers to a negative event, such as nausea, blood disorders or NEUROPATHY. EXPERIMENTAL DRUGS must be evaluated for both short- and long-term side effects. Also called

adverse effect, ADVERSE EVENT or adverse reaction.

Significant: See Statistical Significance.

Sildenafil Citrate (Viagra): a drug used to treat male erectile dysfunction. PROTEASE INHIBITORS can increase blood levels of Viagra.

Simian: of or relating to monkeys.

Simian Immunodeficiency Virus (SIV): a RETROVIRUS found in monkeys that is closely related to HIV.

Simvastatin (Zocor): a CHOLESTEROL-lowering drug.

Sinusitis: INFLAMMATION of the nasal sinuses.

SIV: see SIMIAN IMMUNODEFICIENCY VIRUS.

SOD: see SUPEROXIDE DISMUTASE.

Sonata: see ZALEPLON.

Specificity: a statistical measurement of the accuracy of an ASSAY, in particular, how likely is the assay to accurately provide a negative result when the person is negative. Compare SENSITIVITY.

Spinal Tap: see LUMBAR PUNCTURE.

Spindle Cells: unusually shaped cells found in KAPOSI'S SARCOMA lesions.

Spleen: a large lymphatic organ in the upper left of the abdominal cavity with several functions: (1) trapping of foreign matter in the blood; (2) destruction of degraded red blood cells; (3) formation of new LYMPHOCYTES and ANTIBODY production; and (4) storage of excess red blood cells.

Sporanox: see ITRACONAZOLE.

Sputum Analysis: a method of detecting certain infections (especially TUBERCULOSIS) using a sample of sputum, the mucus matter that collects in the respiratory and upper digestive passages and is expelled by coughing. A sputum smear is cultured in the laboratory to increase the population of any BACTERIA it contains.

Squamous Cell: thin, flat cells that are on the surface of the skin.

SSRI: see SELECTIVE SEROTONIN REUPTAKE INHIBITOR.

St. John's Wort: see SAINT JOHN'S WORT, HYPERICIN.

Statins: a class of drugs that lower CHOLESTEROL.

Statistical Significance: an analytical evaluation of the results of a comparative trial or survey. Data yielding a difference in outcome depending on treatment or environmental factor are generally considered statistically significant if various mathematical procedures indicate that there is less than a one in twenty (5 percent) chance that the same results would occur through chance. See also P VALUE.

Stavudine (d4T, Zerit): an anti-HIV NUCLEOSIDE ANALOG from Bristol-Myers Squibb. Its most common SIDE EFFECT is PERIPHERAL NEUROPATHY.

STD: sexually transmitted disease.

Stem Cell: one of the precursor cells that are the source of all blood cells. Stem cells inhabit the BONE MARROW, where they begin their differentiation and maturation process, a process affected by the CYTOKINES and HORMONES that they encounter. Some

stem cells circulate in the blood.

Steroid: a member of a large family of structurally similar LIPID molecules. Steroid molecules have a basic skeleton consisting of four interconnected carbon rings. Different classes of steroids have different functions. All the sex HORMONES are steroids. CORTISOL and cortisone regulate many aspects of metabolism and, when administered medically, reduce swelling, pain and other manifestations of INFLAMMATION.

Stevens-Johnson Syndrome: a serious, sometimes fatal inflammatory disease characterized by fever, severe rash and blisters on the skin and open sores on the MUCOUS MEMBRANES. The SYNDROME may be triggered by a severe allergic reaction to certain drugs (e.g., TRIMETHOPRIM/SULFAMETHOXAZOLE and NEVIRAPINE).

STI: See STRUCTURED TREATMENT INTERRUPTION.

Stomatitis: INFLAMMATION of the MUCOUS MEMBRANES in the mouth.

Strain: a variant characterized by specific genetic features.

Stromal Cell-Derived Factor (SDF-1): a CHEMOKINE that binds to the CXCR-4 RECEPTOR site.

Structured Treatment Interruption (STI): a planned treatment interruption, typically under medical supervision. The purpose of an STI varies; for example, it can be used to see whether a patient's IMMUNE SYSTEM can control HIV after it has been undetectable for years, or it can be used in an attempt to get a person's viral population to revert from resistant to WILD TYPE.

Subcutaneous: below the skin, also refers to injecting medicines directly under the skin.

Substrate: the compounds acted upon by an ENZYME.

Subtype: a major subpopulation of a given organism, with a distinct genetic makeup. See CLADE.

Sulfa Drug: a group of ANTIBIOTIC drugs containing a particular sulfur-nitrogen (sulfonamide) unit, such as SULFADIAZINE. The drugs work by interfering with the METABOLISM of FOLIC ACID, a B VITAMIN. Many HIV-infected persons experience allergic reactions to sulfa drugs. In some cases this reaction can be overcome with a DESENSITIZATION protocol.

Sulfadiazine: a sulfa drug used in combination with PYRIMETHAMINE for treating TOXOPLASMOSIS. Possible SIDE EFFECTS include BONE MARROW SUPPRESSION.

Superoxide Dismutase (SOD): one of the major cellular ANTIOXIDANT ENZYMES. It removes surplus peroxide, an oxidizing FREE RADICAL. Superoxide dismutase comes in two forms, one containing zinc and the other containing manganese.

Surrogate Marker: a laboratory measurement or physical sign that does not directly reflect how sick a person is, but rather predicts the likely effect of a medication on their future disease status. CD4 CELL COUNT and VIRAL LOAD are examples of surrogate markers in HIV infection.

Susceptibility: the degree to which a virus can be inhibited by drugs. Compare RESISTANCE.

Sustiva: see EFAVIRENZ.

Symptomatology: the collected symptoms of a particular disease.

Syncytium (pl.: Syncytia): a giant cell formed by the fusion of an HIV-infected cell with one or more adjacent non-infected cells, observed in laboratory cell cultures. This clumping of cells leads to direct cell-to-cell infection and massive cell death. Strains of HIV are classified as SI (syncytia-inducing) or NSI (non-syncytia-inducing). SI strains infect T CELLS, both naturally occurring and laboratory bred lines, and bind to the CXCR4 RECEPTOR site. They are associated with rapid disease progression.

Syndrome: a set of related symptoms or manifestations of a disease that define a specific condition.

Synergy (adj.: Synergistic): the interaction of two of more treatments such that their combined effect is greater than the sum of the individual effects observed when each treatment is administered alone.

Systemic: concerning or affecting the body as a whole. A systemic therapy is one that the entire body is exposed to, rather than just the target tissues affected by a disease.

T

T Cell (T Lymphocyte): any LYMPHOCYTE that matures in the THYMUS. These include CD4 and CD8 CELLS.

T Helper Cell: see CD4 CELL.

T Lymphocyte: see T CELL.

T Lymphocyte-Tropic: see T-TROPIC.

T-Tropic HIV (T Lymphocyte-Tropic, CXCR4-using HIV; SI HIV): refers to strains of HIV that have an affinity for infecting CD4 CELLS,usually through the CXCR-4 RECEPTOR site. T-tropic HIV is generally of the SI variety (see SYNCYTIUM).

T4 Cell: see CD4 CELL.

T4 Cell Count: see CD4 CELL COUNT.

T-20: see ENFUVIRTIDE.

T-1249: an experimental FUSION INHIBITOR similar to ENFUVIRTIDE.

Tagamet: see CIMETIDINE.

Tat: an HIV PROTEIN that helps produce new complete HIV RNA GENOMES, and ultimately new VIRUS, from the HIV proviral DNA template present in infected cells. Tat may also be involved in: (1) the reactivation of other latent viruses in people with AIDS, such as JC virus, the cause of PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY (PML); (2) the development of AIDS-related KAPOSI'S SARCOMA (KS) by stimulating the formation of new blood vessels; and (3) the triggering of ANERGY and APOPTOSIS in CD4 CELLS.

Taxol: see PACLITAXEL.

TB: see TUBERCULOSIS.

TCA: see TRICYCLIC ANTIDEPRESSANT.

Telomeres: protective repetitive genetic fragments at the end of CHROMOSOMES.

Tenofovir (PMPA, Viread): an approved NUCLEOTIDE ANALOG from Gilead Sciences.

Teratogenicity: the ability to cause defects in a developing fetus. This is distinct from mutagenicity, which results in genetic mutations in sperms, eggs or other cells. Teratogenicity is a potential SIDE EFFECT of many drugs, such as THALIDOMIDE.

Testosterone: the naturally occurring male HORMONE. When administered as a drug it can cause gain in LEAN BODY MASS, increased sex drive and possibly aggressive behavior. Many men with HIV have low testosterone levels.

Tetrahydrocannabinol (THC): the psychoactive component of marijuana. See CANNABIS.

Th1 Response: an acquired IMMUNE RESPONSE whose most prominent feature is high CYTOTOXIC T LYMPHOCYTE activity relative to the amount of ANTIBODY production. The Th1 response is promoted by CD4+ "Th1" T helper cells. See also TH2 RESPONSE.

Th2 Response: an acquired IMMUNE RESPONSE whose most prominent feature is high ANTIBODY production relative to the amount of CYTOTOXIC T LYMPHOCYTE activity. The Th2 response is promoted by CD4+ "Th2" T helper cells. See also TH1 RESPONSE.

Thalidomide: a drug that reduces levels of TUMOR NECROSIS FACTOR (TNF) and inhibits ANGIOGENESIS. It is being studied as a treatment for AIDS-related WASTING SYNDROME, APHTHOUS ULCERS, diarrhea and KAPOSI'S SARCOMA. Potential SIDE EFFECTS include sedation, constipation, PERIPHERAL NEUROPATHY and severe birth defects in the infants born to women taking the drug during pregnancy.

THC: See TETRAHYDROCANNABINOL.

Therapeutic Index: the ratio between the toxic concentration of a drug and an effective one. To be a useful therapy, the therapeutic index has to be high. For example, if a drug can halt HIV replication in a patient, but only at levels high enough to kill the patient, tooæits therapeutic index is too low.

Therapeutic Vaccine: a therapy consisting of synthetic or prepared HIV ANTIGEN (e.g., GP160 or killed vaccine with its ENVELOPE stripped off). The vaccine is administered to people who already have HIV, usually along with an ADJUVANT to increase the effect. The goal is to heighten and broaden the IMMUNE RESPONSE to HIV, helping to halt disease progression. To date no therapeutic vaccine has demonstrated effectiveness, but several are being studied.

Thioctic Acid: a natural, thiol (sulfur-containing) ANTIOXIDANT that has a potent neutralizing effect on many FREE RADICALS.

Thioctic acid may have some activity against HIV.

Thrombocyte: see PLATELET.

Thrombocytopenia: low number of PLATELETS in the blood. See IMMUNE THROMBOCYTOPENIC PURPURA.

Thrush: an oral fungal infection. Also called oral candidiasis. See CANDIDIASIS.

Thymic Hormones: HORMONES produced by the THYMUS that are believed to play a role in the maturation of T LYMPHOCYTES and overall modulation of the IMMUNE SYSTEM. Versions of several of them have been under study as anti-HIV therapies - thymopentin and thymosin-a1 in particular.

Thymidine: a NUCLEOSIDE that is one of the basic components of DNA. ZIDOVUDINE (AZT) and STAVUDINE (d4T) are ANALOGS of thymidine.

Thymine: a nucleic acid base in DNA that pairs with ADENINE.

Thymosin Alpha: an IMMUNOMODULATOR that, among other things, increases LYMPHOCYTES' sensitivity to signaling molecules like ALPHA INTERFERON and INTERLEUKIN-2 (IL-2).

Thymus: a lymphoid organ in the chest that is the site of LYMPHOCYTE formation and maturation as well as the secretion of thymic HORMONES. An important function of the thymus is to weed out lymphocytes that react to PROTEINS produced by the body ("self-ANTIGENS"), thus preventing AUTOIMMUNE DISEASE. The thymus is a large organ during childhood, but begins to shrink during adolescence.

TID: a term used on prescriptions to mean, "take three times a day," from the Latin phrase ter in die.

Time-Averaged Difference (DAVG): the AVERAGE change in given variable over a particular period of time. Calculated by dividing the AREA UNDER THE CURVE (AUC) by the elapsed time since a study began. The effect of treatment on VIRAL LOAD is sometimes expressed in terms of the DAVG.

Time to Event (Time and Event Schedule): a method of compiling and evaluating data from CLINICAL TRIALS that allows for participants to enroll at different times.

TIND: see TREATMENT INVESTIGATIONAL NEW DRUG.

Tipranavir: an experimental PROTEASE INHIBITOR, licensed to Boerhinger-Ingleheim.

Titer: the concentration or ACTIVITY of a given dissolved substance, such as a drug, ANTIBODY or ANTIGEN, as measured by the solution's chemical reactivity in a "titration assay." In particular, the extent to which an antibody-PLASMA extract can be diluted before losing its ability to protect against the corresponding antigen.

TMP/SMX: see TRIMETHOPRIM/SULFAMETHOXAZOLE.

TNFa: see TUMOR NECROSIS FACTOR ALPHA.

Tomography: see COMPUTED TOMOGRAPHY (CT) SCAN.

Topical: applied directly to the skin.

Topoisomerase: an ENZYME that uncoils the tightly wound DNA in cells' nuclei so that cell division and replication can take place. See TOPOTECAN.

Topotecan (Hycamtin): an anticancer CHEMOTHERAPY FDA-approved for REFRACTORY metastatic ovarian cancer. It inhibits TOPOISOMERASE I and blocks cell division. Its main drawback is severe BONE MARROW SUPPRESSION, leading to life-threatening NEUTROPENIA.

Total Parenteral Nutrition (TPN): a liquid food substitute infused directly into a vein and designed to meet a person's entire nutritional needs. TPN provides an alternate nutritional route in cases of severe gastrointestinal distress and poor nutrient absorption. It strengthens the body and relieves the digestive tract while therapy for the underlying condition progresses.

Toxicity: the harmful SIDE EFFECTS of a given drug.

Toxoplasmosis ("toxo"): a life-threatening OPPORTUNISTIC CONDITION caused by the PROTOZOA Toxoplasma gondii.

Toxoplasmosis can affect a number of organs, but it most commonly causes ENCEPHALITIS (brain INFLAMMATION) with characteristic focal lesions. It is contracted by eating contaminated undercooked meat. There is a very small risk of contracting toxoplasmosis from contact with toxo-containing cat feces. Symptoms include headache, confusion, fever, dementia and paralysis. Standard treatment is a combination of PYRI- METHAMINE and SULFADIAZINE. TRIMETHOPRIM/SULFAMETHOXAZOLE (Bactrim or Septra) is the standard preventive in toxoplasma-positive patients with CD4 counts below 100.

TPN: see TOTAL PARENTERAL NUTRITION.

Trachea: the windpipe, the passage in the throat leading to the lungs.

Transcription: the synthesis of RNA from DNA.

Treatment-Experienced: refers to patients with a history of previous treatment for a particular condition. Compare TREATMENT-NAIVE.

Treatment Investigational New Drug (TIND): a FDA-approved program that allows a drug developer to give physicians an experimental medication for administration to seriously ill patients who have no other treatment options. In exchange, the doctor provides data on the safety and effectiveness of the drug. It is similar to PARALLEL TRACK, but is not limited to HIV and AIDS drugs and may be instituted only at a later stage in a drug's development after it has shown an indication of EFFICACY besides demonstrable safety.

Treatment-Naive: refers to patients with no history of previous treatment for a particular condition. Compare TREATMENT-EXPERIENCED.

Trental: see PENTOXIFYLLINE.

Tricyclic Antidepressant (TCA): a class of drugs such as Elavil used to treat depression. TCAs may be sedating and have been used for treating insomnia. TCAs also are used for the treatment of PERIPHERAL NEUROPATHY. SIDE EFFECTS include drowsiness, constipation and muscle pain. See also SELECTIVE SEROTONIN REUPTAKE INHIBITOR.

Triglyceride: The combination of glycerol with three separate chains of fatty acids. This is the basic structure of most fats and oils.

Trimethoprim/Sulfamethoxazole (TMP/SMX, Bactrim, Septra): a combination ANTIBIOTIC drug effective at preventing and treating PNEUMOCYSTIS CARINII PNEUMONIA (PCP). It also serves as a PROPHYLAXIS against TOXOPLASMOSIS. Possible SIDE EFFECTS include skin rash (which on rare occasions spreads to other body surfaces and becomes life-threatening STEVENS-JOHNSON SYNDROME), digestive disturbances, BONE MARROW SUPPRESSION and liver impairment.

Trimetrexate (Neutrexin): an INTRAVENOUS ANTIBIOTIC approved as an alternative treatment for moderate-to-severe PNEUMOCYSTIS CARINII PNEUMONIA (PCP) in cases of TRIMETHOPRIM/SULFAMETHOXAZOLE (TMP/SMX) failure or intolerance. Trimetrexate has serious BONE MARROW, liver, kidney and gastrointestinal TOXICITIES due to its interference with FOLIC ACID METABOLISM. It must be administered along with leucovorin (folinic acid, which becomes folic acid in the body) to ameliorate the BONE MARROW SUPPRESSION and other SIDE EFFECTS.

Triple Therapy: the use of three drugs, most often a PROTEASE INHIBITOR or NON NUCLEOSIDE ANALOG with two NUCLEOSIDE ANALOGS, in the treatment of HIV.

Trizivir: a pill from GlaxoSmithKline that combines ABACAVIR, ZIDOVUDINE (AZT) and LAMIVUDINE (3TC).

Troglitazone: a drug used to lower blood TRIGLYCERIDES. Because troglitazone induces the CYP3A4 (see CYTOCHROME P450) pathway, it is not recommended for people on ANTIRETROVIRAL therapy.

Tropism: an attraction to something; more specifically, the tendency of a VIRUS to preferentially infect a particular host tissue or cell. Viral tropism is determined in part by the interaction of structures on the viral envelope (see ENVELOPE, GP41, GP160, GP120) with host cell receptor sites (see RECEPTOR, CD4, CCR5, CXCR-4).

Trough Level: the minimum concentration of a drug in blood plasma, occurring at the time the next dose of a drug is administered. Sometimes abbreviated as CMIN. Achieving an adequate trough level that retains sufficient antimicrobial activity is important in avoiding the rise of drug resistant MICROBES. See also PEAK LEVEL.

Tuberculosis (TB): a disease caused by the BACTERIUM Mycobacterium tuberculosis. TB primarily infects the lungs, but it may attack almost any tissue or organ of the body. TB generally has a long latency period, and only about 10 percent of infected people with normal immunity ever experience active TB. For people with immune deficiencies, active TB is much more common. TB is transmitted in close quarters when a person with active TB coughs the MICROBE into the air.

Tumor Necrosis Factor Alpha (TNFa): a CYTOKINE produced by MACROPHAGES that helps activate T CELLS. It also may stimulate HIV activity. TNF levels can be elevated in people with HIV, and the molecule is suspected to play a part in HIV-related WASTING SYNDROME, NEUROPATHY and dementia.

U

Ultrasensitive: usually refers to VIRAL LOAD tests that can detect 50 or fewer copies of HIV RNA per cubic millimeter.

Undetectable: see LIMIT OF DETECTION.

Up-Regulation: an increase in the rate at which something happens.

Uracil: one of the nucleic acid bases that makes up RNA.

Uridine: a NUCLEOSIDE of URACIL.

Uveitis: INFLAMMATION of the uvea, the vascular middle coat of the eye within the outer white part (the sclera).

V

V3 Loop: refers to a portion of the HIV ENVELOPE PROTEIN, GP120, that plays a central role in enabling HIV VIRIONS to bind to uninfected cells. The AMINO ACID sequence of the V3 loop can mutate considerably.

Vaccine: a substance that contains RECOMBINANT ANTIGEN or weakened or killed infectious organisms. A vaccine provides long-term immunity against a PATHOGEN by producing an acquired IMMUNE RESPONSE giving rise to MEMORY T CELLS without causing disease. No effective HIV vaccine has yet been discovered. See IMMUNIZATION.

Valacyclovir (Valtrex): the PRODRUG of ACYCLOVIR. Valacyclovir is an ANTIVIRAL drug approved for the treatment of SHINGLES and recurrent genital HERPES. It also has been tried unsuccessfully as a preventive treatment of AIDS-related CYTOMEGALOVIRUS (CMV).

Valganciclovir: an experimental treatment for CYTOMEGALOVIRUS (CMV) RETINITIS.

Valtrex: see VALACYCLOVIR.

Varicella Zoster Virus (VZV): a HERPES VIRUS that causes chicken pox in children. Its REACTIVATION in adults causes SHINGLES.

Vector: a carrier or mode of transport for a parasite or disease-causing agent. Also a VIRUS genetically engineered to carry a desired DNA sequence into cells' nuclei - used for GENE THERAPY and VACCINES.

Verruca Acuminata: see CONDYLOMA ACUMINATUM.

Vertical Transmission: transmission of a PATHOGEN such as HIV from mother to fetus or baby during pregnancy or birth. Also called perinatal transmission.

Viagra: see SILDENAFIL CITRATE.

Videx: see DIDANOSINE.

Vif Gene: an HIV GENE that influences viral infection of the host cell.

Viracept: see NELFINAVIR.

Viral Load: the amount of HIV RNA per unit of blood PLASMA. An indicator of VIRUS concentration and reproduction rate, HIV viral load is employed as a measure of the success of ANTIRETOVIRAL therapy. It may be measured by POLYMERASE CHAIN REACTION, BRANCHED DNA ASSAYS and nucleic acid sequence based amplification (NASBA) and is expressed in number of copies of or equivalents to the HIV RNA GENOME per milliliter of plasma. (Note that there are two RNA copies per HIV virion.)

Viramune: see NEVIRAPINE.

Viremia: the presence of VIRUS in blood or blood PLASMA. Plasma viremia is a quantitative measurement of HIV levels similar to VIRAL LOAD but is accomplished by seeing how much of a patient's plasma is required to spark an HIV infection in a laboratory cell culture.

Virion: a complete VIRUS particle existing outside a cell.

Virology: the study of VIRUSES and viral diseases.

Virulence: the power of a microorganism to cause grave disease.

Virus: a noncellular PATHOGEN composed essentially of genetic material (DNA or RNA) surrounded by a PROTEIN ENVELOPE. Viruses can reproduce only within living cells into which they inject their genetic material. The viral GENES then subvert an infected cell's normal chemical processes to create new virus particles, usually killing the cell in the process.

Vistide: see CIDOFOVIR.

Vitamin: ORGANIC MOLECULES essential in small amounts for normal METABOLISM, growth and development of the body. See also MICRONUTRIENT.

Vitamin C: see ASCORBIC ACID.

Vitrasert: see INTRAOCULAR IMPLANT.

Vitravene: see FOMIVIRSEN.

Vitreous Humor: the gel-like substance that fills the eyeball between the lens and the retina.

Vpr Gene: a regulatory GENE in HIV whose function is not known.

Vpu Gene: a regulatory GENE in HIV whose function is not known.

VZV: see VARICELLA ZOSTER VIRUS.

W

Wasting Syndrome: an AIDS-DEFINING CONDITION characterized by unintentional loss of at least 10 percent of normal weight. The weight loss is largely the result of depletion of the PROTEIN in LEAN BODY MASS and represents a metabolic derangement frequent during AIDS.

Wellbutrin: see BUPROPION.

Western Blot: a test for detecting the specific ANTIBODIES to HIV in a person's blood. It commonly is used to verify positive ENZYME-LINKED IMMUNOSORBENT ASSAY (ELISA tests). A Western Blot test is more reliable than the ELISA, but it is more difficult and more costly to perform. All positive HIV antibody tests should be confirmed with a Western Blot test.

White Blood Cell: see LEUKOCYTE.

Wild Type Virus: naturally occurring HIV with an optimal genetic makeup and no artificially or lab-induced mutational defects. This term also refers to HIV that has not been exposed to ANTIVIRAL drugs and therefore has not accumulated MUTATIONS conferring drug RESISTANCE.

WinRho: see IMMUNE THROMBOCYTOPENIC PURPURA.

Y

Yeast Infection: see CANDIDIASIS.

Z

Zalcitabine: see DIDEOXYCYTIDINE.

Zaleplon (Sonata): a hypnotic used to treat insomnia.

ZDV: see ZIDOVUDINE.

Zerit: see STAVUDINE.

Ziagen: see ABACAVIR.

Zidovudine (AZT, ZDV, Retrovir): a NUCLEOSIDE ANALOG from GlaxoSmithKline. AZT is also approved for preventing maternal-fetal HIV transmission. Possible SIDE EFFECTS include BONE MARROW SUPPRESSION leading to ANEMIA, LEUKOPENIA or NEUTROPENIA, nausea, muscle weakness and headaches.

Zinc: an essential mineral often depleted in persons with HIV. Zinc is a component of many ENZYMES. It is important in protecting cells against excess OXIDATION and helps immune cells mature and function. Ingesting high doses of zinc can be harmful, however, because it interferes with the absorption of copper, another essential MICRONUTRIENT.

Zinc Finger Inhibitors: a class of experimental anti-HIV drugs.

Zinc Fingers: ZINC-containing AMINO ACID structures on the surface of one of HIV's core PROTEINS. The zinc fingers capture and help package HIV genetic material into newly budding VIRIONS. They also appear to play a role during the early stage of cell infection, by aiding REVERSE TRANSCRIPTASE.

Zithromax: see AZITHROMYCIN.

Zocor: see SIMVASTATIN.

Zoloft: see SERTRALINE.

Zolpidem (Ambien): a hypnotic used for insomnia.

Zovirax: see ACYCLOVIR.