FIG. 5.

Cell-cell fusion mediated by mutant EnvAs. Cell-cell fusion assays were performed as described previously (11), except that modified vaccinia virus Ankara-infected PG950 cells were incubated overnight in medium containing rifampin (100 μg/ml), and the cell-cell fusion medium contained both rifampin (100 μg/ml) and AraC (150 μg/ml). It should be noted that at no time did the pH of any of these media dip below pH 7.2. The data from triplicate samples from a representative experiment were averaged. Samples are labeled as in the legend to Fig. 1. Wild-type, wild-type EnvA.