A novel wild-derived MHC-linked locus regulates host immunity to gammaherpesvirus infection

Inefficient host control of infection by gammaherpesviruses is a risk factor for lymphoproliferative disease, autoimmunity, and cancer, yet naturally occurring genetic determinants of viral control remain poorly defined. Previously, we discovered that wild-derived PWD/PhJ (PWD) mice exhibit markedly improved control of murine gammaherpesvirus 68 (MHV-68) replication compared with C57BL/6J (B6) mice. This elite control of viral replication was linked to muted T cell responses, but partially dependent on NK cells. Here, we used genetic approaches to identify host determinants controlling MHV-68 resistance in PWD mice. Analysis of B6PWDF1 and B6PWDF2 populations suggested the existence of a major locus in the PWD genome contributing to MHV-68 resistance. Using B6.ChrPWD chromosome substitution (consomic) mice, we mapped a major resistance locus to Chr 17 and refined the required interval to 27.6-49.4 Mb, including the MHC locus. While B6.Chr17PWD mice recapitulated muted T cell responses observed in PWD mice, they controlled viral burden independent of NK cells and without reduced frequencies of infected germinal center B cells, indicating that resistance of PWD mice comprises multiple genetically and mechanistically distinct pathways. While the NK cell receptor complex on PWD chromosome 6 did not provide protection, genotype-phenotype analysis of the B6PWDF2 cohort revealed additional non-Chr 17-linked loci contributing to viral control. Together, our results identify a novel MHC-linked locus regulating gammaherpesvirus burden with minimal cytotoxic T cell expansion, demonstrating that effective host control of gammaherpesviruses can be achieved by diverse immune mechanisms.