Murine cytomegalovirus downregulates ERAAP and induces an unconventional T cell response to self

Abstract

The endoplasmic reticulum aminopeptidase associated with antigen presentation (ERAAP) plays a crucial role in shaping the peptide-MHC I repertoire and maintaining immune surveillance. While murine cytomegalovirus (MCMV) has multiple strategies for manipulating the antigen processing pathway to evade immune responses, the host has also developed ways to counter viral immune evasion. In this study, we found that MCMV modulates ERAAP and induces an IFN-{gamma} producing CD8+ T cell effector response that targets uninfected ERAAP deficient cells. We also observed that ERAAP downregulation during infection led to presentation of the self-peptide FL9 on non-classical Qa-1b, thereby eliciting Qa-1b restricted QFL T cells to proliferate in the liver and spleen of infected mice. QFL T cells upregulated effector markers upon MCMV infection and were sufficient to reduce viral load after transfer to immunodeficient mice. Our study highlights the consequences of ERAAP dysfunction during viral infection and provides potential targets for antiviral therapies.