FIG 7.

Effects of stoichiometry of CD4mc binding to the HIV-1 Env trimer on activation and inactivation. The proposed effect of binding of the CD4mc (red oval) to the subunits of the HIV-1 Env trimer is depicted. In all cases, the binding of a single CD4mc to the Env trimer leads to activation, and the binding of three CD4mc leads to inactivation. The binding of two CD4mc to the Env trimer leads to virus activation of infection in CD4-negative, CCR5-positive cells but results in virus inactivation during infection of CD4-positive, CCR5-positive cells.