Autoimmunity associated allele of tyrosine phosphatase genePTPN22enhances anti-viral immunity

Abstract The 1858C>T allele of the tyrosine phosphatase PTPN22 is present in 5-10% of the North American population and is strongly associated with numerous autoimmune diseases. Although research has been done to define how this allele potentiates autoimmunity, the influence PTPN22 and its pro-autoimmune allele has in anti-viral immunity remains poorly defined. Here, we use single cell RNA- sequencing and functional studies to interrogate the impact of this pro- autoimmune allele on anti-viral immunity during Lymphocytic Choriomeningitis Virus clone 13 (LCMV-cl13) infection. Mice homozygous for this allele (PEP- 619WW) clear the LCMV-cl13 virus whereas wildtype (PEP-WT) mice cannot. This is associated with enhanced anti-viral CD4 T cell responses and a more immunostimulatory CD8α - cDC phenotype. Adoptive transfer studies demonstrated that PEP-619WW enhanced anti-viral CD4 T cell function through virus-specific CD4 T cell intrinsic and extrinsic mechanisms. Taken together, our data show that the pro-autoimmune allele of Ptpn22 drives a beneficial anti-viral immune response thereby preventing what is normally a chronic virus infection. Author Summary PTPN22 and its alternative allele, 1858C>T, has largely been studied in the context of autoimmunity. Through these studies, researchers defined roles for PTPN22 in regulating T lymphocyte activation, myeloid cell cytokine production, and macrophage polarization. Despite these immune pathways being critical for anti-viral immunity, little work has studied how this allele impacts virus infection. In this study, we examine gene expression and function of immune cell subsets to demonstrate how a common allelic variant of PTPN22, which strongly increases the risk of autoimmune disease, promotes successful clearance of an otherwise chronic viral infection.