HIV-1 egress is gated through late endosomal membranes.

HIV-1 buds from the surface of activated T lymphocytes. In macrophages, however, newly formed HIV-1 particles amass in the lumen of an intracellular compartment. Here, we demonstrate by live-cell imaging techniques, by immunocytochemistry and by immuno-electron microscopy that HIV-1 structural proteins, particularly the internal structural protein Gag, accumulate at membranes of the late endocytic compartment in a variety of cell types and not just in monocyte/macrophage-derived cells. Recent biochemical and genetic studies have implicated components of the mammalian vacuolar protein sorting pathway in retroviral budding. Together with those observations, our study suggests that HIV-1 morphogenesis is thoroughly rooted in the endosomal system.