Fig. 3.

Altered recognition of the drug-modified ECLs by MVC-Res Env. Luciferase reporter viruses pseudotyped with MVC-Sens Env (A) or with MVC-Res Env (B and C) were used to infect U87-CD4 cells expressing equivalent levels of WT CCR5 or CCR5 with alternative mutations in the ECL1, ECL2, or ECL3 region, as described in Materials and Methods, in the absence (A and B) or presence (C) of MVC. The CCR5-expressing cell populations were generated and characterized with regard to their CCR5 expression levels as described previously (66). The level of virus entry into cells expressing a particular CCR5 mutant was expressed as a percentage of entry into cells expressing WT CCR5. The data shown are means and standard errors from a compilation of 3 independent experiments. Double asterisks indicate that the increase in dependence on a particular residue over that of MVC-Res Env in the absence of the drug is significant (P, <0.05 by an unpaired t test).