The state or condition in which the body (or part of the body) is invaded by an
infectious agent (e.g., a
bacterium,
fungus or
virus), which multiplies and produces an injurious effect (active infection). As related to HIV: Infection typically begins when HIV encounters a CD4+ cell. The HIV surface protein
gp120 binds tightly to the
CD4 molecule on the cell's surface. The membranes of the
virus and the cell fuse, a process governed by
gp41, another surface protein. The
viral core, containing HIV's
RNA,
proteins and enzymes, is released into the cell. See
CD4 (
T4) or CD4+ Cells;
gp41;
gp120.