A type-C virus in human rhabdomyosarcoma cells after inoculation into NIH Swiss mice treated with antithymocyte serum

A type-C RNA virus has been isolated that replicates readily in human and other primate cells. It was obtained from a human rhabdomyosarcoma cell (RD) that had been serially transplanted in immunosuppressed NIH Swiss mice, a strain of mouse from which infectious type-C virus has not been isolated. Various other human tumor cells, similarly transplanted, remained free of overt type-C virus expression. The virus growing in the RD cells, AT-124, has a group-specific antigen and an RNA-dependent DNA polymerase immunologically related to murine type-C viruses, but a host range similar to that of the RD-114 virus. The new isolate is either a previously undescribed, endogenous type-C virus from NIH Swiss mice or a recombinant with both mouse and human type-C genetic information.