FIG 4.

Plaque morphologies of H7 mutant VACVs. BSC-1 (top rows) and BSC-H7 (bottom rows) cells in 12-well plates were infected with the indicated H7R mutant VACVs in semisolid medium for 48 h. The cells were then stained with crystal violet to reveal plaques. For each mutant, the same amount of virus was used to infect BSC-1 and BSC-H7 cells. The mutants were studied in groups in four separate experiments (A to D), each with a WT control. Thus, the plaque sizes of different mutants can be compared within groups but not between groups.