Uninhibited growth and metastases of herpes simplex virus-transformed cells in virus-sensitized hosts

Four established tumour lines of hamster cells transformed by herpes simplex virus (HSV) but not shedding the virus were examined for continued expression of virus-associated antigens. Hamster or rabbits, appropriately immunized to the tumour cells, produced virus-neutralizing antibody. The serum titres were invariably low, suggesting that only small quantities of virion antigen were present in the cells. Hamster sensitized to HSV and resistant to virulent virus challenge did not reject low numbers of tumour cells, nor was the incidence of lung metastases significantly reduced. Virus-sensitized lymph-node cells, readily cytotoxic for HSV-infected hamster embryo fibroblasts, did not lyse any of three transformed lines tested in an 18-h 51chromium release test. Animals that had their tumour excised demonstrated no or only modest resistance to tumour rechallenge. Thus, virus-specific transplantation rejection antigen could not be detected in the HSV tumour lines although low levels of virus structural antigens were present.