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ACQUIRED IMMUNODEFICIENCY SYNDROME (AIDS): The most severe manifestation of infection with the human immunodeficiency virus (HIV). The Centers for Disease Control and Prevention list numerous opportunistic infections and neoplasms (cancers) which, in the presence of HIV infection, constitute an AIDS diagnosis. In addition, a CD4+ T-cell count below 200/mm3 in the presence of HIV infection constitutes an AIDS diagnosis. The period between infection with HIV and the onset of AIDS averages 10 years in the United States. People with AIDS often suffer infections of the lungs, brain, eyes and other organs, and frequently suffer debilitating weight loss, diarrhea and a type of cancer called Kaposi's sarcoma. Even with treatment, most people with AIDS die within two years of developing infections or cancers that take advantage of their weakened immune systems. See also CD4 (T4) or CD4+ Cells; Diarrhea; HIV Disease; Kaposi's Sarcoma; Opportunistic Infection; Wasting Syndrome.

ACTG: See AIDS Clinical Trials Group.

ACUTE INFECTION: An infection causing disease with a sudden onset, severity and (often) short course. As related to HIV infection: Once the virus enters the body, HIV infects a large number of CD4+ T cells and replicates rapidly. During this acute or primary phase of infection, the blood contains many viral particles that spread throughout the body, seeding themselves in various organs, particularly the lymphoid tissues. See also Acute Retroviral Syndrome; CD4 (T4) or CD4+ Cells; Infection; Lymphoid Organs.

ACUTE RETROVIRAL SYNDROME: The acute or primary HIV infection often passes unrecognized, but may be present as a mononucleosis-like syndrome within three months of the infection. The diagnosis is made by demonstrating HIV antibody seroconversion. See also Seroconversion.

ACYCLOVIR: (Acycloguanosine). A nucleoside analog antiviral drug used to treat the symptoms of the genital form of herpes simplex virus infection. See also Herpes Simplex Virus; Nucleoside Analog.

ADENOPATHY: Any disease involving or causing enlargement of glandular tissues, especially one involving the lymph nodes.

ADJUVANT: An ingredient-as in a prescription or solution-that facilitates or modifies the action of the principal ingredient. May be used in HIV therapies or for HIV vaccines.

ADMINISTRATION: (Route of Administration). A term used to refer to how a drug or therapy is introduced into the body. Systemic administration means that the drug goes throughout the body (usually carried in the bloodstream), and includes oral administration (by mouth) and intravenous administration (injection into the vein). Local administration means that the drug is applied or introduced into the specific area affected by the disease, such as application directly onto the affected skin surface (topical administration). The effects of most therapies depend upon the ability of the drug to reach the affected area, thus the route of administration and consequent distribution of a drug in the body is an important determinant of its effectiveness.

ADVERSE EVENT: In a clinical trial, an unwanted effect detected in participants. The term is used whether or not the effect can be attributed to the intervention under study.

ADVERSE REACTION: See Side Effects.

AEROSOLIZED: A form of administration in which a drug, such as pentamidine, is turned into a fine spray or mist by a nebulizer and inhaled. See also Pentamidine.

AETC: See AIDS Education and Training Centers.

AFFECTED COMMUNITY: This includes HIV-positive people, persons living with AIDS and other individuals, including their families, friends and advocates, directly impacted by HIV infection and its physical, psychological and sociological ramifications.

AGAMMAGLOBULINEMIA: A nearly total absence of immunoglobulins. See also Antibodies.

AIDS: See Acquired Immunodeficiency Syndrome.

AIDS CLINICAL TRIALS GROUP (ACTG): The ACTG is composed of a number of US medical centers that valuate treatment for HIV and HIV-associated infections. ACTG studies are sponsored by the National Institute of Allergy and Infectious Diseases.

AIDS DEMENTIA COMPLEX: About half the people infected with HIV, the virus that causes AIDS, develop infections or other problems involving the brain or spinal cord. These neurological complications may include inflammation of the brain (encephalitis), or of the membrane surrounding the brain (meningitis), infections of the brain, brain or spinal cord tumors, nerve damage, difficulties in thinking and behavioral changes (i.e., AIDS dementia complex) and stroke.

AIDSDRUGS: An online database service administered by the National Library of Medicine, with references to drugs undergoing testing against AIDS, AIDS-related complex and related opportunistic infections.

AIDSLINE: An online database service administered by the National Library of Medicine, with citations and abstracts covering the published scientific and medical literature on AIDS and related topics.

AIDS-RELATED CANCERS: Several cancers are more common or more aggressive in people infected with HIV, the virus that causes AIDS. These malignancies include certain types of immune system cancers known as lymphomas, Kaposi's sarcoma and anogenital cancers primarily affecting the cervix and the anus. HIV, or the immune suppression it induces, appears to play a role in the development of these cancers. See also Cervical Cancer; Kaposi's Sarcoma; Lymphoma.

AIDS-RELATED COMPLEX (ARC): 1. A term, not officially defined or recognized by the Centers for Disease Control and Prevention, that has been used to describe a variety of symptoms and signs found in some persons infected with HIV. These may include recurrent fevers, unexplained weight loss, swollen lymph nodes, and/or fungus infection of the mouth and throat. Also commonly described as symptomatic HIV infection. 2. Symptoms that appear to be related to infection by the HIV virus. They include an unexplained, chronic deficiency of white blood cells (leukopenia) or a poorly functioning lymphatic system with swelling of the lymph nodes (lymphadenopathy) lasting for more than three months without the opportunistic infections required for a diagnosis of AIDS. See also Wasting Syndrome.

AIDS SERVICE ORGANIZATION (ASO): A health association, support agency or other service active in the prevention and treatment of AIDS.

AIDSTRIALS: An online database service administered by the National Library of Medicine, with information about clinical trials of agents under evaluation against HIV infection, AIDS and related opportunistic infections.

AIDS WASTING SYNDROME: See Wasting Syndrome.

ALTERNATIVE THERAPY: In Western countries, alternative therapy refers to any type of medicine that supplements or is used in lieu of biomedicine (i.e., conventional medicine) or allopathic medicine. In other parts of the world, where traditional medicine predominates, the term may refer to biomedicine itself.

AMINO ACIDS: Any of a class of organic compounds having a carboxyl group (COOH) and an amino group (NH2). Some 22 amino acids are commonly found in animals, and more than 100 less common forms are found in nature, chiefly in plants. When the carboxyl carbon atom of one amino acid binds to the nitrogen of another with the release of a water molecule, a linkage called a peptide bond is formed. Chains of amino acids, joined head-to-tail in this manner, are synthesized by living systems and are called polypeptides (up to about 50 amino acids) and proteins (over 50 amino acids). See also Peptide; Proteins.

ANALOG: In chemistry, a compound with a structure similar to that of another compound, but differing from it in respect to certain components or structural makeup; it may have a similar or opposite action metabolically.

ANEMIA: A lower than normal number of red blood cells.

ANTIBIOTIC: An antimicrobial agent, derived from cultures of a microorganism or produced semisynthetically, used to treat infections.

ANTIBODIES: Molecules in the blood or secretory fluids that tag, destroy or neutralize bacteria, viruses or other harmful toxins. They are members of a class of proteins known as immunoglobulins, which are produced and secreted by B lymphocytes in response to stimulation by antigens. An antibody is specific to an antigen. See also Antigen; Lymphocyte.

ANTIGEN: A substance that, when introduced into the body, is capable of inducing the production of a specific antibody. See also Antibodies. ANTIRETROVIRAL AGENTS: Substances used against retroviruses such as HIV. See also Retrovirus.

ANTITOXINS: Antibodies that recognize and inactivate toxins produced by certain bacteria, plants or animals. See also Antibodies.

ANTIVIRAL: A substance or process that destroys a virus or suppresses its replication.

ARM: A group of participants in a clinical trial, all of whom receive the same treatment or placebo. See also Placebo.

ASO: See AIDS Service Organization.

ASYMPTOMATIC: Without symptoms. Usually used in AIDS literature to describe a person who has a positive reaction to one of several tests for HIV antibodies, but who shows no clinical symptoms of the disease.

ATTENUATED: Weakened or decreased. For example, an attenuated virus can no longer produce disease, but might be used to produce a vaccine.

AUTOANTIBODY: 1. An antibody that is active against some of the tissues of the organism that produced it. 2. An antibody directed against the body's own tissue. See also Antibodies.

AUTOIMMUNIZATION: The induction in an individual of an immune response to its own cells (tissue). See also Immune Response.

AZT: Azidothymidine (also called zidovudine or ZDV; the Burroughs-Wellcome trade name is Retrovir). One of the first drugs used against HIV infection, AZT is a nucleoside analog that suppresses replication of HIV. See also Nucleoside Analog.