FIG. 5.

Preincubation with soluble 2D7-2SK peptide reduces the fusion inhibition activity of MAb 2D7. 2D7 antibody (at 10 μg/ml) was incubated for 1 h at 37°C with 100-fold molar excess of different peptides before addition to CCR5-expressing PM1 cells for an additional hour at 37°C. Effector 12E1 cells expressing BaL envelope were added, and syncytia were scored after 3 h. The number of syncytia (598/well) observed between effector/target cells in absence of 2D7 antibody is represented as 100%. Fusion inhibition was compared with that of a control culture without IgG additives (PBS). Data shown are representative of four independent experiments. Standard deviations did not exceed 10% of the means for all groups. The 2D7-2SK peptide itself did not demonstrate any inhibitory activity in the fusion assay (not shown).