 However, CCR5 inhibitors such as vicriviroc, as well as other entry inhibitors of HIV-1, inhibit the initial stages of the virus life cycle.HIV binds to and fuses with the target T-cells or macrophages with the help of gp120 and gp41, the only two proteins that are currently known to be exhibited on the surface of the viral envelope.One molecule of each protein associates noncovalently with the other on the viral membrane, and three of these units aggregate to form the gp120/gp41 heterotrimer, which traps the gp41 in a conformationally metastable state.