FIG 4.

In vitro effect of the ORF63 deficiency on growth of MuHV-4. (A) Effect of ORF63 deficiency on MuHV-4 growth in vitro. BHK-21 cells were infected with WT, ORF63 STOP, and ORF63 Rev MuHV-4 strains in 6-well cluster dishes at an MOI of 0.01 PFU per cell. Supernatant and infected cells were harvested at different times after infection, and the amount of infectious virus was determined by plaque assay on BHK-21 cells. The data are averages from triplicate measurements ± SEMs and were analyzed by 2-way ANOVA and Bonferroni posttests. ***, P < 0.001. At time zero p.i., the inocula were retitrated to ensure that similar amounts of virus were put on the cells. (B) Effect of the absence of pORF63 on MuHV-4 plaque size. BHK-21 cells grown on coverslips were infected with MuHV-4 WT, ORF63 STOP, and ORF63 Rev strains and then overlaid with DMEM containing CMC as described in Materials and Methods. At successive intervals after infection, plaques were fixed and measured. Each datum point is the average ± SEM for the measurement of 20 plaques per time point. The data were analyzed by 2-way ANOVA and Bonferroni posttests. *, P < 0.05; **, P < 0.01; ***, P < 0.001.