ROLE OF VIF DURING PACKING OF THE CORE OF HIV-1

The viral infectivity factor gene vif of human immunodeficiency virus type 1 (HIV-1) has been shown to enhance the cell-free infectivity of HIV-1 virus particles. Previous studies have demonstrated that vif inc reases viral infectivity at the time of virus production, most likely by affecting viral protein processing, virus assembly, or virus matura tion. The effect of vif on the assembly and maturation of HIV-1 propag ated in CEM, Jurkat, and SupT1 cells was examined by electron microsco py and goniometer analysis. CEM and Jurkat cells are nonpermissive and partially permissive for the replication of vif- defective viruses, r espectively, while SupT1 cells are completely permissive. In CEM and J urkat cultures, the morphology of immature vif+ and vif- virions was s imilar but immature virus particles were observed at a slightly higher frequency in cultures infected with the vif- virus. At later stages o f virus maturation, however, nonhomogeneous packing of the core was de tected in the majority of vif- virus particles produced in CEM and Jur kat cells. In the absence of vif, the cone-shaped virus core contained dense material in its broad end but, in contrast to vifi+ virions, th e material inside its narrow end appeared transparent. The narrow part of the vif- virus core was surrounded by a shell and was attached to the viral envelope by a core-envelope link structure. Vif- virus parti cles with a lateral body of core material adjacent to the viral envelo pe were also observed more frequently in CEM and Jurkat cultures. In c ontrast, in SupT1 cultures the morphology of mature vif+ and vif- viru s particles was similar. These results suggest that vif is associated with an effect during the final stages of packing of the viral nucleop rotein core. This effect may be important for the infectivity of HIV-1 virus particles. (C) 1994 Academic Press, Inc.