HIV-2 and SIV infection of nonprimate cell lines expressing human CD4: restrictions to replication at distinct stages.

Mouse, rat, rabbit, cat, and mink cell lines expressing human CD4 restrict entry of HIV-1 strains at the cell surface. We now report that CD4+ cat and rabbit cell lines are permissive to cell fusion induced by several HIV-2 and SIV strains. CD4+ rat and mouse cells are only sensitive to HIV-2 and SIV fusion in the presence of active amphotericin B. HIV-2 and SIV replicate in CD4+ cat and CD4+ mink cells, but not in the CD4+ rabbit, rat, or mouse cells. These latter cell lines poorly express a transfected DNA molecular clone of HIV-2 DNA. CD4+ rat cells are sensitive to entry by HIV-2 (HTLV-1) pseudotypes and also to HIV-2 if amphotericin B is present. Early reverse transcription then occurs without subsequent viral gene expression, but the fusion-sensitive CD4+ rabbit cells are not permissive for HIV-2 reverse transcription. Our observations demonstrate (i) that the cat and mink cell lines express everything required except human CD4 for entry and replication by several HIV-2 and SIV strains and (ii) that distinct postpenetration blocks to viral replication are evident in rabbit and rodent cell lines.