FIG. 5.

In vitro growth properties of PrV mutants. (A) For determination of plaque sizes, infected RK13 cells were incubated for 48 h under semisolid medium. The average diameters of 30 plaques and standard deviations were calculated. (B) For determination of growth kinetics, RK13 cells were infected at a MOI of 2 and scraped into the medium after 3, 6, 9, 12, 24, 48, and 72 h at 37°C. The cells were lysed by freezing and thawing, and progeny virus titers were determined by plaque assays. The mean results of two experiments are shown.