Host factors involved in retroviral budding and release.

The plasma membrane is the final barrier that enveloped viruses must cross during their egress from the infected cell. Here, we review recent insights into the cell biology of retroviral assembly and release; these insights have driven a new understanding of the host proteins, such as the ESCRT machinery, that are used by retroviruses to promote their final separation from the host cell. We also review antiviral host factors such as tetherin, which can directly inhibit the release of retroviral particles. These studies have illuminated the role of the lipid bilayer as the unexpected target for virus restriction by the innate immune response.