DIFFERENTIATION BETWEEN HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 (HIV-1) AND HIV-2 ISOLATES BY NONRADIOISOTOPIC REVERSE TRANSCRIPTASE-TYPING ASSAY

We tested whether human immunodeficiency virus type 1 (HIV-1) could be differentiated from HIV-2 by a reverse transcriptase (RT)-typing assa y that measured the reduction of enzyme activity owing to specific ant ibody. RT-inhibiting antibody was examined for HIV type specificity by a new nonradioisotopic RT assay. Antibodies from four rabbits immuniz ed with recombinant HTV-1 RT and from 23 HTV-1-seropositive individual s all specifically inhibited the enzyme activities of two HTV-1 strain s (LAV-1 and GH-3), three zidovudine-resistant HIV-1 mutants, and a re combinant HIV-1 RT. However, none of these antisera affected the activ ities of six HIV-2 strains (GH-1, GH-2, GH-4, GH-5, GH-6, LAV-2(ROD)), Rous-associated virus type 2, and DNA polymerase I from Escherichia c oli. In contrast, HIV-2 antibody from a rabbit immunized with disrupte d GH-1 virions blocked the enzyme activities of the six HIV-2 strains but not those of the three HTV-1 strains, Rous-associated virus type 2 , or DNA polymerase I. These results indicate that the antigenic domai ns of HIV-1 and HIV-2 RTs recognized by their inhibiting antibodies ar e distinct from each other and are highly conserved. Clinical HIV isol ates from 18 HIV-1-seropositive individuals and 3 HIV-2-seropositive G hanaian individuals were identified as HIV-1 and HIV-2, respectively, by the nonradioisotopic RT-typing assay.