Plaque assays were conducted using a L2 fibroblast cell line as previously described (32) with minor modifications for visualization and quantification of plaques. L2 fibroblasts were seeded at 1.2 × 106 per 35-mm-diameter dish and infected at an MOI of 0.5 to obtain approximately 30 PFU per dish. At 4 to 6 days postinfection, cells were stained with 0.3% crystal violet for 10 min and washed twice with deionized water. Stained wells were imaged and areas of plaque formation were measured on Fiji image analysis software (68).