FIGURE 7.

Alteration of RDD to RAE inhibits the binding and fusogenic activity of the aMPV/B F protein. A, the aMPV/B F protein RDD motif was mutated to RAE. Vero cells were transfected with either the wild-type aMPV/B F or the RAE mutant. The binding activity of the F proteins was measured in a cell-cell binding assay. A representative cell-cell binding graph was obtained from flow cytometric analysis. B, the cell-cell binding results as the mean percentage from three independent experiments. C, representative micrographs of syncytia formation mediated by the wild-type aMPV/B F protein and the mutant in Vero cells. D and E, the fusogenic activity of the wild-type aMPV/B F protein and the mutant were also measured using syncytium formation and reporter gene assays. F, the surface expression of transfected aMPV/B-F and raMPV/B-F-RAE was confirmed by biotinylation and a Western blot assay. All experiments were repeated three to five times. p < 0.05 and p < 0.005 are indicated by * and **, respectively.