Role of Interferon in the Protective Effect of the Double-Stranded Polyribonucleotide Against Murine Tumors Induced by Moloney Sarcoma Virus<xref ref-type="fn" rid="FN1">2</xref>

Tumor growth in NMRI mice infected neonatally with the Moloney strain of murine sarcoma virus (M-MSV) was effectively inhibited by the synthetic double-stranded polyribonucleotide (poly rl:rC). This protective effect was obtained with repeated doses of poly rl:rC injected on alternate days from 1 day to 11 days after virus inoculation, as well as with a single dose of poly rl:rC injected 12 hours before virus inoculation. The antitumor effect of a single injection of poly rl:rC 12 hours before virus challenge could be duplicated by exogenous interferon administered in amounts closely mimicking the interferon blood levels obtained endogenously with poly rl:rC. This indicates that the whole antitumor effect of a single dose of poly rl:rC, injected 12 hours before M-MSV infection, is due to interferon production.