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Definitions R through S
Randomized trial: A study in which participants are
randomly assigned to either a treatment or a placebo arm.
Reactogenicity: The capacity to produce adverse
reactions.
Reagent: Any chemical used in a chemical reaction
or test.
Receptor: A molecule on the surface of a cell that
serves as a recognition or binding site for antigens, antibodies or other cellular or
immunologic components.
Recombinant: An organism whose genome contains
integrated genetic material from a different organism.
Regulatory genes: HIV genes (nef, rev, tat) that
regulate viral replication in infected cells.
Regulatory T cells: T cells that direct other
immune cells to perform special functions. The chief regulatory cell, the CD4+ T cell or
T-helper cell, is HIV's main target.
Retrovirus: HIV and other viruses that carry their
genetic material in the form of RNA and have the enzyme reverse transcriptase.
Reverse transcriptase: The enzyme produced by HIV
and other retroviruses that allows them to synthesize DNA from their RNA.
Seroconversion: The development of antibodies to a
particular antigen. When people develop antibodies to HIV or an experimental HIV vaccine,
they "seroconvert" from antibody-negative to antibody-positive.
Serostatus: Results of a test for a specific
antibody.
SF-2: An HIV-1 isolate used in vaccine development.
SF-2 belongs to clade B, the clade to which most HIV-1 found in North America and Europe
belong.
SHIV: Genetically engineered hybrid virus having an
HIV envelope and an SIV core.
SIV: Simian immunodeficiency virus. An HIV-like
virus that infects and causes an AIDS-like disease in some species of monkeys.
STD: Sexually transmitted disease.
Statistical significance: The probability that an
event or difference occurred by chance alone.
Sterilizing immunity: An immune response that
completely eliminates an infection.
Stratification: Separation of a sample or
population into subgroups, according to some characteristic.
Subtype: Also called a clade.
Subunit HIV vaccine: A genetically engineered
vaccine that contains only part of HIV.
Surrogate marker: An indirect measure of disease
progression. In HIV disease, the number of CD4+ T cells/mm3 of blood is often used as a
surrogate marker.
Syncytia: Giant cells formed by the fusion of an
HIV-infected cell with one or more uninfected ones.
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