An autoimmunity-associated allele of <i>PTPN22</i> enhances innate antiviral immunity to protect against acute coronavirus infection.

Abstract

Allelic variation can impact viral clearance and disease severity. Still, our understanding of the effect of the autoimmunity-associated allelic variant of <i>Ptpn22</i> (PEP-R619W) on antiviral immunity remains incomplete, as previous reports have only focused on chronic lymphocytic choriomeningitis virus infection. This research defines how the loss of <i>Ptpn22</i> (PEP-null) and PEP-R619W changes antiviral immunity during an acute coronavirus infection. We address the hypothesis that CRISPR/Cas9-generated PEP-null and PEP-R619W mice have enhanced antiviral immunity over PEP-wild-type (WT) mice during coronavirus infection. Following mouse hepatitis virus A59 infection, we interrogated pathology, cytokine production, and cellular responses in the blood, spleen, and liver of PEP-WT, PEP-null, and PEP-R619W mice. Key findings show that PEP-R619W mice have reduced viral titer and weight loss, increased survival, and more mature natural killer (NK) cells in the liver and spleen compared to PEP-WT mice. Interestingly, protection against disease in PEP-null mice was inoculation dose dependent, whereas PEP-R619W conferred immunity regardless of infection dose. Further, Rag1^-/- PEP-R619W mice had increased survival and reduced viral titer over Rag1^-/- PEP-WT mice. PEP-R619W mice also had higher concentrations of interferon-gamma (IFNγ) and enhanced IFNγ production by mature NK cells in the liver at 3 d postinfection. Finally, NK cell depletion elevated PEP-R619W viral titer to similar levels as PEP-WT mice. This study investigates the role of <i>Ptpn22</i> within NK cells and demonstrates that the <i>Ptpn22</i> allelic variant augments NK cell function and is beneficial during coronavirus infection.