Comparison of the plaque morphologies of MODV-WNV(prM-E) and the parental viruses in Vero cells. Confluent monolayers of Vero cells in six-well plates were inoculated with MODV-WNV(prM-E), MODV or WNV. Cells were fixed and plaques were visualized by staining with crystal violet at 3, 5 and 7 days p.i. Images were transferred into Microsoft Photoshop and plaque diameters were measured. The chimeric virus had been passaged one in BHK-21 cells and twice in Vero cells prior to this experiment.