Gamma Interferon (IFN-γ) Receptor Null-Mutant Mice Are More Susceptible to Herpes Simplex Virus Type 1 Infection than IFN-γ Ligand Null-Mutant Mice

Abstract

ABSTRACT Mouse strains with null mutations in the gamma interferon gene ( Ifng ) or the gamma interferon receptor gene ( Ifngr ) have been engineered. The use of these strains as animal models of viral and bacterial infections has enhanced our understanding of the role of gamma interferon (IFN-γ) in the host immune response. However, direct comparisons between Ifng −/− (GKO) and Ifngr −/− (RGKO) mice have been problematic because previously available strains of these mice have had different genetic backgrounds (i.e., C57BL/6 and BALB/c for GKO mice and 129/Sv//Ev for RGKO mice). To enable direct comparison of herpes simplex virus type 1 (HSV-1) infections in GKO and RGKO mice, we introduced the IFN-γ null mutation into the 129/Sv//Ev background. We report that, after HSV-1 inoculation, mortality was significantly greater in RGKO mice than in GKO mice (38 versus 23%, P = 0.0001). Similarly, the mortality from vaccinia virus challenge was significantly greater in RGKO mice than in GKO mice. With differences in genetic background excluded as a confounding issue, these results are consistent with the existence of an alternative ligand(s) for the IFN-γ receptor that is also capable of mediating protection against viral challenge.