Fig. 1.

Difference in syncytium formation induced by F48-F* and La-F* in the transfected BHK-21 cells. a Schematic diagram of the F proteins of the virulent strain F48E9 and avirulent strain LaSota with the cleavage motif “RRQRRL” (*). b Induction of syncytium formation by co-transfection with the F* and HN constructs in BHK-21 cells. At 36 h post-transfection, monolayers were examined for the presence of syncytia, which were photographed under the microscope. Syncytia are indicated by black arrows. c Quantitative analysis of the syncytia in (b)