Background:  Numerous cellular proteins have now been implicated as participants in the assembly and release of infectious HIV virions from target cells. The HIV Gag protein appears to be targeted to lipid raft microdomains of the plasma membrane, where it interacts with spatially sequestered proteins. The presence of actin and actin-binding proteins in virions even after permeabilization with cyclodextrin, have lead to the suggestion that they may form part of a “viroskeleton” that maintains virion integrity. We tested the hypothesis that disruption of microfilaments would interfere with the assembly of infectious virions.

Methods:  Latrunculin and Jasplakinolide, which stabilize and disrupt microfilaments, were used to shift the balance between G and F actin in virus producing transfected cells. Immunoblot and immunofluorescence were used to confirm the activity of these agents. p24 ELISA was used to monitor virus release. Virions were pelleted through sucrose gradients to separate virions from drug-containing medium, and their infectivity was assessed using Hela-LTR-b galactosidase (Magi) indicator cells

Results:  Latrunculin and jasplakinolide markedly and reversibly altered the actin cytoskeleton, but did not diminish virion release. More importantly, virion infectivity was unaltered by disruption of the cytoskeleton.

Conclusions:  The actin cytoskeleton does not appear to play a role in the production of infectious HIV, and actin is likely incorporated into virions in a passive fashion.

Keywords: actin; assembly; virion