Teach Online Glossary

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.

< 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.





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 birth¾shortly 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.


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).





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.


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.


PMN (Polymorphonuclear) Cell: see NEUTROPHIL.


Pneumocystis Carinii Pneumonia (PCP): a lung infection caused by Pneumocystis carinii (which is either a PROTOZOA or FUNGUS¾it 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.


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.



Rosiglitatzone: a drug used to lower blood TRIGLYCERIDES.


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.


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.


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.


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.



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.



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.



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).


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-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.



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.


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, too¾its 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.


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.




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.


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.


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.


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.


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.


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.


< 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.



< Y >

Yeast Infection: see CANDIDIASIS.

< Z >


Zalcitabine: see DIDEOXYCYTIDINE.

Zaleplon (Sonata): a hypnotic used to treat insomnia.


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.


Zoloft: see SERTRALINE.

Zolpidem (Ambien): a hypnotic used for insomnia.

Zovirax: see ACYCLOVIR.


© 2003 Gay Men's Health Crisis