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HIV/AIDS Glossary

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Acute Infection:
Any infection that begins suddenly, with intense or severe symptoms, is called acute. If the illness lasts more than a couple of weeks, it is called chronic.

AIDS (Acquired Immunodeficiency Syndrome): A disease caused by a retrovirus, HIV (human immunodeficiency virus), and characterized by failure of the immune system to protect against infections and certain cancers.

AIDS Clinical Trials Group (ACTG): A set of about 50 research centers around the country where federally funded drug trials are conducted.

AIDS-Related Complex: (ARC) A condition caused by HIV in which the person is positive for HIV and has clinical symptoms not generally as severe as those of AIDS.

Amphotericin B: A drug used to treat fungal infections, including candidiasis (thrush).

Antibiotic: A drug used to combat bacterial infection by killing bacteria or slowing their growth.

Antibody: A substance in the blood formed in response to invading disease agents such as viruses, fungi, bacteria, and parasites. Usually antibodies defend the body against invading disease agents, however, the HIV antibody does not give such protection.

Antibodies: Proteins produced by plasma cells in response to a specific foreign organism. These proteins in the blood tag, destroy, or neutralize bacteria, viruses, or other harmful toxins.

Antigen: An invading substance that may be the target of antibodies.

Antiviral: A substance that stops or suppresses the activity of a virus.

Antiretroviral: A treatment that may prevent HIV from damaging the immune system.

Asymptomatic: Having no signs or symptoms of a disease, yet able to transmit the causative agent.

AZT: SeeZidovudine.


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Bacteria: Microscopic organisms that can cause disease.

Bactrim: (trimethoprim/sulfamethoxazole). Also known as Septra. An antibacterial agent used to treat pneumocystis carinii pneumonia, among other diseases.

B-Cell: A white blood cell that makes antibodies against disease agents in the body.


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Candidiasis: A fungal infection which occurs in several places in the body, including the mouth or throat (thrush), in the vagina, or on the skin; a common opportunistic infection in people with HIV.

CD4 (T4): A protein receptor embedded in the cell surface of T-lymphocytes, monocytes/macrophages, Langerhans cells, astrocytes, keratinocytes, and glial cells. HIV invades cells by first attaching to the CD4 receptor molecules.

Centers for Disease Control: (CDC) Federal health agency that is part of the U.S. Department of Health and Human Services; provides national health and safety guidelines and statistical data on AIDS and other diseases.

CMV: (Cytomegalovirus) A virus related to the herpes family. CMV may occur without any symptoms or may result in mild flu-like symptoms. Severe infections can result in retinitis, hepatitis, mononucleosis, colitis, or pneumonia in persons with HIV. CMV is shed in body fluids such as urine, semen, saliva, feces, and sweat.

Cryptococcus: A fungal infection rarely seen in healthy persons but common in persons with HIV. Is acquired via the respiratory tract and characteristically spreads to the meninges (lining of the brain and spinal cord) and may also infect the kidneys and skin.

Cryptosporidiosis: An infection caused by a protozoan parasite found in the intestines of animals: it may be transmitted to humans by direct contact with an infected animal or by ingestion of contaminated food or water. The parasite grows in the intestine and causes severe chronic diarrhea in persons with HIV.

Cytokine: A chemical messenger secreted by immune cells to regulate immune activity.

Cytomegalovirus (CMV): A virus related to the herpes family that can cause fever, fatigue, enAWTxtBold d lymph glands, aching, and a mild sore throat. In AIDS, CMV infections can produce hepatitis, pneumonia, retinitis, and colitis. It can sometimes lead to blindness, chronic diarrhea, and death.


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ddC: (dideoxycytidine) A drug that inhibits HIV through inhibition of reverse transcription.

ddI: (dideoxyinosine) A drug that inhibits HIV through inhibition of reverse transcription.

DNA: (deoxyribonucleic acid) A complex protein that carries genetic information. HIV can insert itself into the DNA molecules inside human cells and establish dormant infection.


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ELISA (Enzyme-Linked Immunosorbent Assay): A blood test used to detect the presence of antibodies to HIV; results that show the presence of HIV antibodies must be confirmed by the Western Blot test before a person is considered to be HIV-infected. Has high degree of sensitivity (accurate for detecting true positive samples).

Encephalitis: Inflammation of the brain, frequently caused by a viral infection.

Esophageal Candidiasis: Serious fungal infection in the conduit between the mouth and the stomach (the esophagus).


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Factor VIII: One of the clotting factors in the blood. Congenital absence of Factor VIII results in hemophilia A.

Fungus: A general term used to denote a class of microbes including mushrooms, yeasts, and molds.


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Ganciclovir (DHPG): A drug used to treat cytomegalovirus infection.

Genome: The DNA that comprises the complete genetic composition of an organism.


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Hairy Leukoplakia: A whitish, slightly raised lesion that appears on the side of the tongue. Thought to be related to Epstein-Barr Virus infection.

Half-Life: The amount of time it takes for half of a dose of any drug to be eliminated from the body.

Helper-Suppressor Ratio: The ratio of "helper" T4 cells to "suppressor" T8 cells. The T4/T8 ratio is normally about 2, but in HIV-infected persons the ratio frequently drops below 1.

Hemophilia: An inherited disease that prevents the normal clotting of blood.

Hepatitis B: A viral infection that affects the liver and is transmitted only through blood-to-blood and sexual contact.

Herpes Virus: A family of viruses that cause herpes simplex (cold sores), herpes zoster (shingles), Epstein-Barr (infectious mononucleosis), and cytomegalovirus. These viruses tend to occur in a severe form in an immunocompromised person, such as one with HIV.

Histoplasmosis: A fungal respiratory disease.

HTLV-III: Human T-cell lymphotropic virus, type III. An earlier term for human immunodeficiency virus (HIV), the cause of AIDS.

Human Immunodeficiency Virus (HIV): HIV is the virus that causes the Acquired Immuno Deficiency Syndrome(AIDS). HIV attacks and slowly destroys the immune system by entering and destroying the cells that control and support the immune response system. After a long period of infection, usually 3-7 years, enough of the immune system cells have been destroyed to lead to immune deficiency. The virus can therefore be present in the body for several years before symptoms appear. When a person is immuno deficient, the body has difficulty defending itself against many infections and certain cancers, known as “opportunistic infections”.

It is possible to monitor the development and degree of immuno deficiency, and while the impacts of the disease can be mitigated with proper treatment, there is no cure for AIDS once a person is infected with HIV.

There are three main ways in which HIV is transmitted among people:
(i) By sexual contact
(ii) When infected blood is passed into the body (e.g., through blood transfusion or use of non-sterilized material)
(iii) From an infected mother to her child during pregnancy, childbirth or breastfeeding.

Human Immunodeficiency Virus, Type 1 (HIV-1): The retrovirus recognized as the etiologic agent of AIDS.

Human Immunodeficiency Virus, Type 2 (HIV-2): A virus very similar to HIV-1 that has been found to cause immune suppression. HIV-2 infections are found primarily in Africa.


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IL-2: A substance made by the immune system to fight off viruses and bacteria, called interleukin-2.

Immunocompetent: Capable of developing an immune response.

Immunocompromised: A state when the body's immune system defenses are lowered and the body is less able to resist infections and tumors.

Immunomodulator: A treatment that may help rebuild a damaged immune system.

Immunosuppressed: A state of the body in which the immune system defenses have been suppressed.

Interferon: A substance secreted by an infected cell which strengthens the defenses of nearby cells that are not yet infected. These substances are named differently according to their activity (interferon alpha, interferon gamma, etc.), and some have been manufactured into immune- modulating drugs.


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Kaposi's Sarcoma: A tumor of the blood-vessel wall or the lymphatic system: it usually appears as pink to purple, painless spots on the skin but may also occur internally in addition to or independent of cutaneous lesions. A form of skin cancer, recognized as raised non tender red or purplish spots on the skin. It may also occur internally (in the stomach, lungs, etc.) in addition to, or independent of, skin lesions.


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LAS (Lymphadenopathy Syndrome): Persistent swelling of lymph nodes associated with chronic infection. Also known as GLS (generalized lymphadenopathy syndrome) or PGL (persistent generalized lymphadenopathy).

Leukocytes: All white blood cells.

Lymph Nodes: A small collection of tissue that contain T-cells and B-cells; essential to the function of the immune system.


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Macrophage: A scavenger cell specializing in the ingestion and processing of AWTxtBold particulate matter, especially harmful bacteria. Macrophages are susceptible to infection by HIV and may serve as reservoirs for HIV.

Malabsorption Syndrome: Decreased intestinal absorption resulting in loss of appetite, muscle pain, and weight loss.

Meningitis: Infection and inflammation of the membranes that cover the brain and the spinal cord.

Mycobacterium Avium Complex (MAC): A serious opportunistic infection that causes symptoms including night sweats, high fever, cough, weight loss, general fatigue, malabsorption of food, and diarrhea.

Mycobacterium Avium Intracellulare: (MAI) An acid-fast bacillus that can cause infection of most internal organs. MAI infections are a common opportunistic infection of late-stage AIDS.


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National Institutes of Health (NIH): A federal agency of the U.S. Public Health Service that includes 13 institutes. NIH supports and does biomedical and health research, trains scientists, and writes and publishes scientific and medical reports.

Neutopenia: Low number of a certain type of white blood cells called neutrophils that fight bacterial and fungal infections.

Nonoxynol-9: A chemical used in some contraceptive creams, foams, and jellies that kills sperm and viruses. Used with a condom, it can offer added protection from HIV.

Nucleoside Analogue: A type of anti viral drug. Examples: AZT, ddI, or ddC.


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Oral Hairy Leukoplakia (OHL): A white lesion appearing on the tongue in patients with HIV; the lesion appears raised with a corrugated or "hairy" surface.


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Partner Notification: The process of informing the sexual and needle-sharing partners of an HIV-infected person that they may be at risk for the infection.

Pathogen: Any disease-producing microorganism or material.

p24: A core protein of HIV; levels of p24 are sometimes used as a surrogate marker of an anti-retroviral drug's efficacy.

p24 Antigen Level: A level that can be measured in blood and other body fluids. The test used to measure p24 levels detects the presence of a core protein fragment (p24) on HIV.

Pentamidine: A drug used to treat or prevent pneumocystis carinii pneumonia (PCP).

Peripheral Neuropathy: A disorder of the nerves, usually involving the feet or hands, and sometimes the legs and arms. Symptoms may include numbness, a tingling or burning sensation, sharp pain, weakness, and abnormal reflexes. In severe cases, paralysis may result.

Persistent Generalized Lymphadenopathy (PGL): Chronic, diffused, non cancerous lymph node enAWTxtBold ment.

Phase I: The classification of federally funded trials that test experimental drugs to determine their safety and find the most effective dose.

Phase II: The classification of federally funded trials that test an experimental drug to see how well it works and to study its side effects. Phase II trials often involve several hundred participants who are randomly assigned to take either the drug or a control (the standard treatment for the disease or no treatment at all, known as placebo). These trials are usually double-blinded, which means no one knows who is getting the drug until the trial is over. Length is several months to 2 years.

Phase III: Involves several hundred to several thousand patients. Duration is 1-4 years to test safety, effectiveness, and dosage levels.

Placebo: A look-alike "sugar pill" that is compared with an experimental treatment in a clinical trial. Placebos can be used when there is no other proven treatment for the disease being studied or when there is no immediate danger to withholding treatment temporarily.

Placebo-Controlled: A kind of study in which the experimental treatment being tested is compared to no treatment at all.

PLWA: People living with AIDS.

Pneumocystic Carinii Pneumonia (PCP): A fungal infection of the lungs; this the most common opportunistic infection in AIDS patients.

Polymerase Chain Reaction (PCR): A very sensitive test used in research to detect minute amounts of DNA from an organ.

Polymerase Chain Reaction Test: A test that can detect HIV by looking for the genetic information of the virus; the test can find the virus even if it is present in a very small amount or is hidden inside white blood cells.

Prophylaxis: A treatment given to a person to prevent them from getting a particular disease. Treatment intended to prevent the onset of an infection or disease.


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Recombinant: Manufactured; genetically engineered.

Resistance: Diminished effectiveness of a drug against a disease-causing organism.

Retinitis: A general term describing inflammation of the retina. CMV-induced retinitis is a common opportunistic infection in AIDS.

Retrovirus: A class of viruses which includes HIV. Retroviruses are so named because they carry their genetic information in RNA rather than DNA, and the RNA information must be translated "backwards" into DNA.

Reverse Transcriptase: An enzyme essential to the retrovirus that copies the viral RNA into DNA. AZT and other nucleoside analogues apparently inhibit the reverse transcription process.


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Seroconversion: The change from an absence of HIV antibodies in the blood to the presence of those antibodies.

Seroprevalence: The incidence of disease in a given population.

Serostatus: The condition of having or not having detectable antibodies in the blood serum as a result of infection. A person may have either a positive or negative serostatus.

Shingles: A condition caused by the same virus that causes chicken pox and is characterized by inflammation of nerve endings; an opportunistic infection common to people with AIDS.

Spectrophotometer: An instrument used to read the ELISA test for HIV antibodies; it reads the amount of color present to detect whether the blood has HIV antibodies.

STD: Sexually transmitted disease.

Surrogate markers: Levels of cells or proteins that indirectly indicate HIV activity and are used to mark disease progression.

Syncytium: A non functioning clump of cells that have fused together. HIV-infected cells fuse with non-HIV infected CD4+ cells, forming syncytia and compounding the destruction of CD4+ cells.

Syndrome: A group of symptoms and diseases that together are characteristic of a specific condition.


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T4 Cell: A type of T-lymphocyte. The T4 cell enhances the immune response to an infection through a complex series of interactions with other types of lymphocytes (B cells, T8 cells), macrophages, antibody-producing cells, and infectious organisms.

T4/T8 Ratios: The existence and complicated action of two types of white blood cells, one which naturally suppresses the immune system and the other which naturally mediates immune action. Together these T-cells keep the immune system in balance.

Thrush: A fungal infection of the mouth and throat caused by candida, marked by white patches in the oral cavity.

Treatment IND: A program to provide experimental treatment free of charge to patients who have no other available treatment options


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Wasting Syndrome: A condition characterized by involuntary weight loss of more than 10% of baseline body weight plus either chronic diarrhea or chronic weakness and fever for more than 30 days, when these conditions cannot be explained by any illness other than HIV.

Western Blot: A confirmation test for the presence of specific antibodies that is more accurate than the ELISA test for detecting true negatives.


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Zidovudine: (azidothymidine, ZDV, AZT, Retrovir) A thymidine nucleoside analog that inhibits HIV replication.

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