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.

< E >

Early Access Program: see EXPANDED ACCESS PROGRAM.


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.


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.


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.



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.


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.


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.


< 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.


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.


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.



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.


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.


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.


GW-433908: see fosamprenavir.

< H >


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.





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.


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®: 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-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.


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


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-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.



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 >


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

IDU: injection (or INTRAVENOUS) drug user.







IL-10: see INTERLEUKIN-10.

IL-12: see INTERLEUKIN-12.


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.


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.


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.


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 HIV infection. 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.


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

Invirase: see SAQUINAVIR.


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.


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.





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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.


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