Essential Role of T cells in the postexposure prophylaxis of rabies in mice.

Athymic nude mice injected intramuscularly with a street stain of rabies virus were not protected against rabies by postexposure administration of beta-propiolactone-inactivated rabies vaccine. In contrast, their normal littermates were completely protected from death by the same vaccination regimens. Nude mice did not produce IgG antibody as a result of the vaccine during the test period of 15 days, whereas normal littermates produced IgG antibody from day 5 after vaccination. However, passive immunization with antirabies hyperimmune mouse ascites showed that antibody was completely ineffective in protecting either nude mice or their normal littermates against rabies when given later than 2 days after infection. No significant difference in the induction of circulating interferon by the vaccination was noted in these mice. Passive transfer of immune spleen cells to nude mice immediately after infection resulted in 30 to 37.5% protection of the mice. Passively transferred spleen cells did not produce detectable amounts of neutralizing antibody in the recipient mice except on day 2 after the transfer, when a low level of antibody was detected. These observations demonstrate the essential role of T cells in the postexposure prophylaxis of rabies in mice. The mechanisms of the failure of postexposure vaccination in nude mice are discussed.