FIG. 2.

Kinetics of cell-cell fusion induced by the WT and ΔCT. (A) Fusion between 293T cells transiently expressing JRFL WT (filled triangles) or ΔCT (open triangles) and target 3T3.CD4.CCR5 cells was monitored by the flow cytometry assay as described in the legend to Fig. 1. Open squares are the background signal, as observed with mock-transfected 293T cells. (B) The kinetics of fusion induced by HXB2 WT (filled symbols) or ΔCT (open symbols) transiently expressed in 293T and HeLaT4⁺ cells were measured by fluorescence microscopy. Fusion was induced by coculturing the cells either directly at 37°C (triangles) or after preincubation at 23°C for 2.5 h (circles).