Lack of detectable circulating interferon in mice protected against vaccinia virus by induction and elicitation with bacterial systems

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.

Specific and nonspecific cell-mediated resistance to influenza virus in mice

We found that influenza virus had the capacity to replicate in the peritoneal macrophages of normal mice, as revealed by the development of hemadsorption and the appearance intracellularly of S and V antigens. Cell-mediated resistance was studied in mice infected with influenza virus or a bacterial sytem of induction-elicitation. In the homologous system, mice were injected intraperitoneally or exposed by aerosol to a sublethal dose of an egg-adapted swine strain of influenza virus. In the heterologous system, they were infected repeatedly with Staphylococcus aureus and elicited by subcutaneous or aerosol administration of staphylococcal antigens. The peritoneal macrophages from mice specifically or nonspecifically immunized were significantly more resistant than those from normal mice. Also longer survival to in vivo challenge by the mouse-adapted virus, as compared with normal mice, was indicated in bacterially stimulated mice.

Protection of mice against vaccinia virus by bacterial infection and sustained stimulation with specific bacterial antigens

In these experiments, mice which have a strong delayed-type hypersensitivity to mycobacteria were found, when elicited with old tuberculin, to be more resistant to intravenous vaccinia virus challenge than controls. This was manifest as protection from killing when large amounts of virus were injected, or as significantly less tail swelling and damage as well as lower titers of infectious virus when a lesser inoculum was used. Preliminary experiments indicate that animals sensitized with Staphylococcus aureus and elicited with phage lysate of staphylococcus are also more resistant to vaccinia infection.