Temperature-sensitive mutants of murine leukemia virus. V. Impaired leukemogenic activity in vivo

The in vivo biologic activities of a clonal isolate of the Rauscher strain of murine leukemia virus and several conditional lethal mutants with impaired replicative functions at the non-permissive temperature were investigated. The parental virus induced a rapidly developing lymphoid leukemia in a high percentage of NIH Swiss mice inoculated as newborns. Mice inoculated in parallel with temperature-sensitive mutant viruses showed no evidence of disease. The implications of these findings with regard to the requirements for type-C virus replication to permit oncogenic transformation of lymphoid cells in vivo are discussed.