FIG. 4.
Interference by the 427,TC double mutant with viral infectivity. (A) Interference with viral infectivity mediated by heterologous T-tropic Env proteins. 293 cells were cotransfected with 7.5 μg of pHXBCATΔBgl and 5 μg each of pSVIII-LAV or pSVIII-ELI with or without 10 μg of pSVE7(427,TC). pSVIII-ELI encodes the Env of the HIV-1 ELI strain. Cell-free viruses containing 105 cpm of RT activity from each transfection were assayed for Env-mediated viral infectivity. (B) Interference with viral infectivity mediated by the Env proteins derived from primary isolates. 293 cells were cotransfected with 7.5 μg of pHXBCATΔBgl and 5 μg each of pSVIII-env expression plasmids that encoded Env proteins derived from primary isolates as indicated with or without 10 μg of pSVE7(427,TC). Viruses containing 105 cpm of RT activity from each viral supernatant were used to challenge P4-R5 MAGI indicator cells, and CAT activity was assayed.