Fig. 7.

The effect of the P939L substitution mutation in the MHV/A59 spike protein on cell fusion and virus growth. (A). DBT cells were infected with recombinant viruses expressing mutated or wild type spike protein, and fixed at 5.5, 7 and 9 h.p.i. Nuclei in the cells were stained with DAPI and the cell fusion score for each virus was determined by counting the number of nuclei in syncytial giant cells per field. Six arbitrary fields were examined for each sample and the mean values plotted. Error bars indicate the standard deviation of three independent experiments. (B) Representative images of DBT cells infected with the recombinant viruses after incubation of 5.5, 7 and 9 h at 37 °C.