FIG 5.

In vitro fusion activity of gH mutants. RK13 cells were cotransfected with expression plasmids for EGFP, gD, gL, wild-type (WT) or mutated gH, and wild-type gB (A) or C-terminally truncated gB-008 (B). Assays without gH served as negative controls. One day after transfection, the relative fusion activity was determined by multiplication of the mean syncytium area by the number of syncytia in 10 fields of view. Fusion activities in assay mixtures containing wild-type gH were set as 100%. Shown are the mean relative values and corresponding standard deviations from four independent experiments. Results significantly differing from those obtained with WT gH are marked (*, P ≤ 0.05; **, P ≤ 0.01, ***, P ≤ 0.001; ****, P ≤ 0.0001). NS, not significant.