Enhancement of murine sarcoma virus (Moloney) infection and tumorigenesis in vivo by coinfection with Rauscher leukemia virus.

Dual infection of mice with murine sarcoma virus (Moloney) [MSV(M)] and Rauscher leukemia virus (RLV) resulted in an enhanced MSV(M) infection, reflected by increased mortality with tumor. Significant increases in tumor incidence, induced by low concentrations of MSV(M) when inoculated into RLV-infected mice, demonstrated that RLV enhanced MSV(M) oncogenicity. Temporal studies indicated that RLV-mediated enhancement of MSV(M) infection appeared to be independent of the time of RLV challenge. Inoculation with RLV, as early as 5 days prior to or as late as 6 days after MSV(M) infection, resulted in significant increases in incidence of tumor deaths over MSV(M) controls. The level of enhancement of MSV(M) infection produced in mice coinfected with MSV(M) and RLV was maintained over 4 cell-free passages in normal adult mice by MSV(M) originally extracted from tumors induced in dually infected animals. The possible mechanisms by which RLV enhanced MSV(M) infection and oncogenicity are discussed.