Therapy of murine rabies after exposure: efficacy of polyriboinosinic-polyribocytidylic acid alone and in combination with three rabies vaccines.

A murine model simulating human street rabies virus infection was used to evaluate the efficacy of polyriboinosinic-polyribocytidylic acid (poly I-poly C), three rabies vaccines, and combinations of these modes of therapy administered after exposure. One or two doses of 100 mug of poly I-poly C, injected into the same intramuscular site as the challenge virus, significantly reduced the mortality rate when therapy was initiated 3 hr after challenge; however, the same quantity of poly I-poly C injected into the opposite leg did not reduce the mortality rate. The muscle injected with poly I-poly C invariably contained four to eight times more interferon than a similar noninjected muscle from the same animal. Mice treated 3 hr after challenge with each of the three vaccines produced significant levels of antibody but were not protected, whereas treatment with combinations of poly I-poly C and vaccine resulted in significant protection. These results suggest that the combination of induction of local interferon and an immune response contributes to the protection of mice after exposure to street rabies virus infection.