This animation represents the third step in HIV cell entry: fusion. It identifies gp41 as a drug target (Enfuvirtide).
Mechanism of action of enfuvirtide (Fuzeon). From Wikipedia
Enfuvirtide works by disrupting the HIV-1 molecular machinery at the final stage of fusion with the target cell, preventing uninfected cells from becoming infected. A biomimetic peptide, enfuvirtide was rationally designed to mimic components of the HIV-1 fusion machinery and displace them, preventing normal fusion. Drugs that disrupt fusion of virus and target cell are termed entry inhibitors or fusion inhibitors.
HIV binds to the host CD4+ cell receptor via the viral protein GP120; upon binding, GP120 deforms allowing the viral protein GP41 to embed itself into the host cell’s plasma membrane. Enfuvirtide binds to GP41 preventing the creation of an entry pore for the capsid of the virus, keeping it out of the cell.
Maraviroc is an entry inhibitor. Specifically, maraviroc blocks the chemokine receptor CCR5 which HIV uses as a coreceptor to bind and enter a human helper T cell. Because HIV can also use another coreceptor, CXCR4, an HIV tropism test such as a trofile assay must be performed to determine if the drug will be effective