Enhanced resistance against encephalomyocarditis virus infection in mice, induced by a nonviable Mycobacterium tuberculosis oil-droplet vaccine.

Female C57B1/10 mice injected intravenously (i.v.) with nonviable Mycobacterium tuberculosis Jamaica cells associated with oil-droplet emulsions (WCV) were highly resistant to the i.v. injection of encephalomyocarditis virus (EMCV). Resistance to infection (87% survival) was detected from 1 week to at least 12 weeks after injection of WCV. Mice vaccinated i.v. also were resistant to intraperitoneal, subcutaneous, or intramuscular virus challenge, but were not resistant to intracranial challenge. Mice vaccinated intraperitoneally also were resistant to virus infection, whereas WCV administered intramuscularly or subcutaneously did not protect mice from virus injected by any route. Less than 50% of WCV mice that survived virus challenge possessed serum anti-EMCV-neutralizing antibody (less than 1:10), and none had detectable (less than 1:10) serum interferon. Interferon was not detected in sera of WCV mice from 4 to 144 h after i.v. injection of EMCV. Studies concerning the effects of WCV on EMCV infection suggest that mice may be protected by mechanisms that inhibit early viral replication and spread of virus to the central nervous system.