Spontaneous and Induced Mutagenesis in Western Equine Encephalomyelitis Virus in Chick Embryo Cells with Different Repair Activity

Evidence was obtained indicating differences in the survival rate of Western equine encephalomyelitis virus after exposure to ultraviolet radiation and methyl methanesulfonate in commercial and leukosisfree chick embryo cells that differed in repair activity. The levels of spontaneous mutagenesis (on the basis of the yield of small plaque variants of the encephalomyelitis virus) did not essentially change when the virus was passaged in leukosis-free chick embryo cells, whereas an increase in the number of small plaque variants was observed in the cells of commercial chick embryos. A 10-fold increase in the number of induced virus variants was observed in commercial chick embryo cells in experiments with methyl methanesulfonate as compared with the control, whereas the induction of virus variants was not noted in leukosis-free cells.