HIV Vaccine Glossary

ADCC (antibody-dependent cellular cytotoxicity) -- an immune response in which an infected target cell that is coated with antibody is destroyed by an immune cell.

Adjuvant -- a substance sometimes included in a vaccine formulation to enhance or modify the immune-stimulating properties of a vaccine.

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 vaccine under study.

Adverse reaction (side effect) -- in a clinical trial, an unwanted effect detected in participants and attributed to the study vaccine.

AIDS (acquired immunodeficiency syndrome) -- the late stage of HIV disease, characterized by a deterioration of the immune system and a susceptibility to a range of opportunistic infections and cancers.

ALVAC-HIV™ -- a genetically engineered HIV vaccine composed of a live, weakened canarypox virus (ALVAC™) into which parts of genes for non-infectious components of HIV have been inserted. When ALVAC™ infects a human cell, the inserted HIV genes direct the cell to make HIV proteins. These proteins are packaged into HIV-like particles that bud from the cell membrane. These particles are not infectious but fool the immune system into mounting an immune response to HIV. ALVAC™ can infect but not grow in human cells, an important safety feature. (See also canarypox.)

Amino acid -- any of the 26 chemical building blocks of proteins.

Anamnestic response -- the heightened immunologic reaction elicited by a second or subsequent exposure to a particular pathogenic microorganism (e.g., bacterium, fungus, virus), toxin, or antigen. (See also memory cells.)

Anergy -- the loss or weakening of immune response to an irritating agent or antigen. Anergy can be thought of as the opposite of allergy, which is an overreaction to a substance. The strength of the immune response is often quantitatively evaluated by standardized skin tests. A small amount of solution containing an antigen known to cause a response, such as tetanus, mumps, or candida, is injected under the skin and the area checked for a localized skin reaction after 48 to 72 hours. Healthy people will develop a measurable area of redness at the injection site; people who are immune suppressed, such as people with AIDS, will have no measurable response to these skin tests.

Antibody -- an infection-fighting protein molecule in blood or secretory fluids that tags, neutralizes, and helps destroy pathogenic microorganisms (e.g., bacteria, viruses) or toxins. Antibodies, known generally as immunoglobulins, are made and secreted by B lymphocytes in response to stimulation by antigens. Each specific antibody binds only to the specific antigen that stimulated its production. (See also immunoglobulin; binding antibody; enhancing antibody; functional antibody; neutralizing antibody.)

Antibody-mediated immunity -- also called humoral immunity. Immunity that results from the activity of antibodies in blood and lymphoid tissue.