In vitro studies of a co-carcinogenic effect of vaccinia and herpes group viruses

The results of studies of a co-carcinogenic effect of two human infectious viruses in tissue culture are reported here. Viable vaccinia virus actively replicating in the cells of primary BALB/c tissue culture and in a number of continuous murine cell lines has been shown to induce in them expression of major structural p30 protein of murine retroviruses. Vaccinia virus has been also shown to cause biochemical transformation of murine cells. Evidence for the capacity of herpes simplex virus type 2 to induce malignant transformation of BALB/3T3 murine cell line has been obtained and confirmed by transplantation to mice. Transformed cell clones did not contain complete infectious herpes simplex virus but were resistant to superinfection with this virus. N-tropic endogenous murine retrovirus of C type with buoyant density in the saccharose density gradient of 1.18 g/cm3 and a reverse transcriptase activity was expressed in the transformed cells. In the virion structure six proteins typical of these viruses with the prevalence of p30 have been demonstrated. Competitive radioimmunoassay revealed a very high level of virus production: p30 level reached 7500 ng p30 R-MuLV per mg of viral protein. Specificity of this results was shown in control experiments.