Specific targeting to CD4+ cells of recombinant vesicular stomatitis viruses encoding human immunodeficiency virus envelope proteins.

We generated replication-competent, recombinant vesicular stomatitis viruses (VSVs) expressing the human immunodeficiency virus (HIV) envelope protein or an HIV-VSV chimeric envelope protein in which the cytoplasmic domain of the HIV envelope protein was replaced with that from the VSV glycoprotein (G). These recombinants were generated with HIV type 1 (HIV-1) envelopes from both laboratory and primary isolates of HIV-1. The replication-competent recombinant viruses were stable and expressed the foreign proteins at high levels from extra transcription units in VSV. The foreign proteins were processed appropriately and transported to the cell surface. The incorporation of HIV gp120 into VSV particles was demonstrated biochemically only for the construct expressing the chimeric envelopes containing the VSV G cytoplasmic domain. The incorporation of the chimeric HIV envelope protein into the membrane of the recombinant VSV was also demonstrated by electron microscopy with gold-conjugated antibodies. To determine whether specific infection of CD4-positive cells could be demonstrated for these recombinants, we neutralized VSV infectivity due to VSV glycoprotein with anti-VSV serum. The neutralized recombinants expressing the chimeric envelope were able to infect only HeLa cells expressing CD4, and this CD4-specific infectivity was neutralized with anti-HIV serum. This assay also detected a 100-fold-lower titer of CD4-specific infectivity for the VSV recombinant expressing the wild-type HIV envelope. Our results illustrate that it is possible to express functional HIV envelopes from the VSV genome and target the recombinant virus to an alternative receptor. The recombinants may also prove useful as HIV vaccines.