Pseudotyping Human Immunodeficiency Virus Type 1 by Vesicular Stomatitis Virus G Protein Does Not Reduce the Cell-dependent Requirement of Vif for Optimal Infectivity: Functional Difference Between Vif and Nef

The functions of Vif and Nef in human immunodeficiency virus type 1 (HIV-1) infection have some similarities: Vif- and Nef-dependent enhancement of HIV-1 replication is cell type-specific, and defective mutations in these genes result in restricted proviral DNA synthesis in infected cells. It has recently been shown that pseudotyping HIV-1 by the envelope glycoprotein of vesicular stomatitis virus (VSV-G) targets HIV-1 entry to an endocytic pathway and suppresses the requirement of Nef for virus infectivity. In this study, we examined whether VSV-G pseudotyping suppresses the requirement of Vif for HIV-1 infectivity. It was found that pseudotyping HIV-1 by VSV-G did not compensate for the Vif function. Together with the findings that Vif does not influence virus binding/entry and virion incorporation of Env, it is concluded that Vif enhances HIV-1 infectivity at the post-entry step(s) independently of the Env function by a different mechanism to that of Nef.