Figure 1.

Defective SFV recombinants were constructed by substitution of the sequence of the SFV structural proteins with those of the Escherichia coli β-galactosidase gene (lacZ) or those of the env gene from either HIV-1_LAI or HIV-1_BX08. Stocks of recombinant viruses were obtained by cotransfection of the hybrid constructs with a helper SFV mutant bearing a mutation in the virus spike gene, which is incapable of encapsidation (33). The amino acid sequence of the V3 loops of HIV-1_BX08 and HIV-1_LAI are indicated in the Inset.