Enhancement and Suppression of Murine Sarcoma Virus Induced Tumors by Polyriboinosinic Polyribocytidylic Acid

This paper reports the effects of polyriboinosinic·polyribocytidylic acid (rI·rC) on the Moloney strain of murine sarcoma virus (MSV) in BALB/c and AL/N mice. Complete suppression of tumor induction in BALB/c mice was produced by a highly toxic regimen, using terminal virus dilutions. Furthermore, tumors occurred in BALB/c mice after the cessation of multiple injections of rI·rC. These findings suggest that the tumor suppressive action of rI·rC is more likely mediated by its toxic or chemotherapeutic effects than by a direct antiviral action. Pre treatment with a single sub toxic dose of rI·rC, or simultaneous administration of rI·rC and MSV, resulted in enhancement of tumor induction in AL/N mice at all virus dilutions tested. The enhancement was a specific action of rI·rC as it could be reversed by prior immunization with double-stranded RNA. These studies suggest that the relationship between host, drug, and virus is dependent on multiple factors and is more complex than previously thought.