Virus specificity of the antiviral state induced by IFN gamma correlates with resistance to MHV 3 infection

A comparative study was carried out to investigate the correlation between the antiviral effect induced in macrophages by IFN gamma and the resistance of A/J and BALB/c mice to an experimental infection of MHV 3, MHV 4, and MHVA 59. Both mouse strains were resistant to intraperitoneal infection with MHV 4 or MHVA 59 and only the A/J mice showed resistance to MHV 3, the BALB/c mice being fully susceptible to this virus infection. Comparable growth kinetics, for all three viruses, were observed in both mouse strains, except for the MHV 3 growth in BALB/c mice, where the virus titre increased to a peak on day 2, remaining high until day 4 when the mice died of acute hepatitis. The IFN gamma titres in the peritoneum of mice preceded and correlated with the virus growth, higher titres being found in MHV 3 infected BALB/c mice. The highest titre was always observed 24 to 48 h after infection. Among viral strains grown in cultured macrophages, higher titres were always observed in cultures infected with MHVA 59, followed by MHV 3 and the lowest those infected with MHV 4. The macrophage activation by IFN gamma-induced a partial restriction of virus growth only in MHV 3 infected A/J mouse macrophages. A virus specificity of the IFN gamma-induced antiviral state was shown to be in direct correlation with the resistance of mice to MHV 3 infection.