Differentiation between human immunodeficiency virus type 1 (HIV-1) and HIV-2 isolates by nonradioisotopic reverse transcriptase-typing assay

Abstract

We tested whether human immunodeficiency virus type 1 (HIV-1) could be differentiated from HIV-2 by a reverse transcriptase (RT)-typing assay that measured the reduction of enzyme activity owing to specific antibody. RT-inhibiting antibody was examined for HIV type specificity by a new nonradioisotopic RT assay. Antibodies from four rabbits immunized with recombinant HIV-1 RT and from 23 HIV-1-seropositive individuals all specifically inhibited the enzyme activities of two HIV-1 strains (LAV-1 and GH-3), three zidovudine-resistant HIV-1 mutants, and a recombinant HIV-1 RT. However, none of these antisera affected the activities of six HIV-2 strains (GH-1, GH-2, GH-4, GH-5, GH-6, LAV-2ROD), Rous-associated virus type 2, and DNA polymerase I from Escherichia coli. In contrast, HIV-2 antibody from a rabbit immunized with disrupted GH-1 virions blocked the enzyme activities of the six HIV-2 strains but not those of the three HIV-1 strains, Rous-associated virus type 2, or DNA polymerase I. These results indicate that the antigenic domains of HIV-1 and HIV-2 RTs recognized by their inhibiting antibodies are distinct from each other and are highly conserved. Clinical HIV isolates from 18 HIV-1-seropositive individuals and 3 HIV-2-seropositive Ghanaian individuals were identified as HIV-1 and HIV-2, respectively, by the nonradioisotopic RT-typing assay.

Measurement of levels of human immunodeficiency virus type 1 reverse transcriptase (RT) and RT activity-blocking antibody in human serum by a new standardized colorimetric assay

“…In the latter case, RT-Ab which blocks the catalytic capacity of RT (RTb-Ab) is measured. These RTb-Abs have been determined in small sample collections by several groups (1,3,15,24,26). Initially, RTb-Ab was determined by rather laborious, insensitive techniques that required large amounts of RT for activity determination.…”

“…Since high concentrations of serum tend to interfere with RT assays, these earlier studies required the purification of the immunoglobulin G fraction of each serum sample tested (3). Recent work has produced a new generation of highly sensitive and specific methods for the evaluation of RTb-Ab in minute, unpurified serum samples (21,22,26). The ability of an assay to detect RTb-Ab inherently depends on the amount of RT used.…”