Effect of changes in Env on CD4 dependence and infectivity of monocyte-derived macrophages (MDMs). (A) Recombinant viruses carrying the specified HIV-1JR-FL Env were incubated with CD4-negative, CCR5-expressing Cf2Th cells in the presence of CD4MC DMJ-II-121 or sCD4 at the indicated concentrations. The percentage of maximal infection for each virus variant is reported. Maximal (max) infection levels after DMJ-II-121 addition were 728,752 and 237,686 relative luciferase units (RLU) for viruses with the WT and L193A Envs, respectively. (B and C) Infection of MDMs by WT HIV-1JR-FL and L193 mutant viruses was measured as described in Materials and Methods. (D) Infection of MDMs by HIV-1BG505 and the HIV-1BG505 L193A viruses. (E) Infection of MDMs versus HeLa JC.53 cells, which express high levels of CD4 and CCR5 (61), by HIV-1BG505 and the HIV-1BG505 L193A viruses. Results shown are averages (A and C) or representative (B, D, and E) of those obtained in 2 to 5 independent experiments.