[Morphologic characteristics of plaques produced by the rubella virus in cultures of Vero cells].

Under defined plaquing condition, Gilschrist strain of rubella virus showed different plaque morphology and plaque size when tested in Vero cell cultures. These differences were obtained by changing the fetal bovine serum (FBS) concentration. With 2 per cent of FBS rubella virus formed clear plaques that included a number of cells which retained the stain, while with 4 per cent of FBS it formed ring-shaped plaques. These characteristics were retained even after the Gilschrist strain was passaged several times in Vero cell cultures. The cytopathic effect in Vero cell cultures proved to be useful for the titration of rubella virus, giving infective titres in the same logarithmic order than the plaque assay.