FIG. 3.

Increased potency of fusion inhibition mediated by gp41 peptides when added to E/T cells at 31.5°C. Serial dilutions of T20 and T21 (A) or IQN17 (B) were added to E/T cells that were either incubated at 37°C (▪) or preincubated with the inhibitors for 60 min at 31.5°C and then transferred to 37°C (♦). Syncytia were scored 3 to 4 h after transfer to 37°C. The data are plotted as percent inhibition of syncytia in control cultures (medium control) as a function of the inhibitor dose. Three wells per group were set up in all experiments, and the standard deviations did not exceed 15% of the means. The ID₅₀ values calculated from the curves were as follows: T20, 37°C (65 ng/ml), 31.5°C (5 ng/ml); T21, 37°C (540 ng/ml), 31.5°C (65 ng/ml); IQN17 (89.6 Env), 37°C (400 nM), 31.5°C (50 nM); and IQN17 (IIIB Env), 37°C (120 nM), 31.5°C (28 nM).