FIG 3.
Relative infectivity of HIV-1NL4-3 and its mutant viruses. (A) Entry efficiency of pseudoviruses. The wild-type HIV-1NL4-3 and mutant pseudoviruses were normalized to a fixed amount by p24 antigen, and viral infectivity was tested in TZM-bl cells using a single-cycle infection assay. The luciferase activity was measured and corrected for background. (B) HIV-1 Env-mediated cell-cell fusion determined by a dual split-protein assay (DSP). For both entry and fusion data, the luciferase activity of wild-type HIV-1NL4-3 (WT) was treated as 100% and the relative activities of other mutant viruses were calculated accordingly. Data were derived from the results of three (entry) or two (fusion) independent experiments and are expressed as means and standard deviations.