116 Assembly and Release: New Targets for Antiretrovirals? A Waheed, C Adamson, A Ono, and Eric O Freed* HIV Drug Resistance Prgm, NCI, Frederick, MD, USA

HIV-1 particle production is a multistep process that begins with the transport of the newly synthesized Gag polyprotein precursor to the site of assembly, which, in most cell types, is the plasma membrane.  We have recently observed that the localization of HIV-1 assembly is regulated by the plasma membrane levels of the phosphoinositide PI(4,5)P2, indicating that this lipid is a cellular cofactor for Gag targeting. Membrane binding and virus assembly are promoted by the association of Gag with cholesterol-rich lipid raft microdomains at the cell surface.  Virus budding and release are stimulated by interactions between the “late” domain in the p6 region of Gag and components of the host cell endosomal sorting machinery, most notably Tsg101. Following release from the cell, the Gag and GagPol polyprotein precursors are proteolytically processed in a highly ordered fashion by the viral protease.  We have observed that depletion of cholesterol from virus-producing cells inhibits virus release, and ongoing studies demonstrate that the cholesterol-binding compound amphotericin B methyl ester (AME) disrupts both virus production and particle infectivity.  We have also reported that blocking the interaction between Gag and Tsg101 potently and specifically inhibits virus release from the cell surface. The release of other retroviruses can also be specifically disrupted by blocking interactions between their respective late domains and host cell machinery. These studies demonstrate that HIV-1 assembly and release are steps in the virus replication cycle that offer a variety of new targets for antiviral intervention.