CD4 Envelope Interactions of HIV-1 and Related Human Retroviruses

Abstract

The externalized envelope molecules of all human and simian immunodeficiency viruses thus far described have been shown to bind to the CD4 molecule expressed on the surface of some T lymphocytes and monocytes. The interaction of the envelope with CD4 is important both early in infection where it mediates the initial adsorption of the virion to the cell surface, and later during viral replication where it may contribute to a variety of cytopathic effects as well as the down modulation of the CD4 molecule from the cell surface. We have evaluated the extent to which interactions between CD4 and the viral envelope vary among different members of the HIV-1, HIV-2 and SIV family of viruses, and have attempted to determine if these differences correlate with biological heterogeneity. We describe that remarkable differences do exist in the extent to which CD4-envelope binding occur and in the degree of CD4 modulation during viral replication. These differences may contribute both to the cytopathic potential of particular viruses, as well as in their ability to establish superinfection interference of related viral isolates.