FIG. 3.

HIV-1 Env (484-496) variant peptides with substitutions at position 490 antagonize the recognition of wild-type Env (484-496) as measured in a proliferation assay. Autologous B-LCL were prepulsed with 0.5 μg of the index HXBc2 Env (484-496) peptide per ml for 2 h to stimulate the CD4⁺ Th- cell lines to the levels indicated by the horizontal broken lines. Prepulsed B-LCL were then pulsed for an additional 2 h with the indicated concentrations of the index peptide, the Env (484-496) variant peptides, or the nonstimulatory, Mamu-DR*W201-binding Env (172-191) peptide p15. Results are expressed as [³H]thymidine incorporation in counts per minute. In the absence of peptides, the background proliferation of both Th- cell lines was less than 400 cpm.