HIV Entry Revisited

Abstract

HIV has long served as a model for viruses that enter cells by direct fusion at the plasma membrane. Miyauchi et al. (2009) now provide compelling evidence that HIV enters cells primarily by endocytosis.

Figure 1. Entry Pathways for HIV

By visualizing the mixing of viral lipids (red) and contents (blue) with host cell membranes and cytosol, respectively, Miyauchi et al. (2009) observe three distinct routes for entry of host cells by HIV. These include endocytic events in which two-colored HIV particles are internalized, undergo lipid mixing with the vesicle membrane, and deliver their contents into the cytoplasm (A). There are fusion events that occur at the plasma membrane and proceed at least to the stage of hemifusion (B). These are followed by subsequent endocytosis and content mixing. There are also fusion events at the plasma membrane that do not result in any subsequent content mixing (C).