IL-36γ regulates neutrophil infiltration and limits neuroinvasion in genital HSV-2 pathogenesis

Abstract

Abstract Herpes simplex virus 2 is a neurotropic virus that causes a persistent, life-long infection that increases risk for other sexually transmitted infections. The vaginal epithelium is the first line of defense against HSV-2 and secretes immune mediators, including the pro-inflammatory cytokine IL-36γ, to coordinate the immune response. Previously, we showed that IL-36γ treatment promoted polymorphonuclear cell infiltration to the vaginal cavity and protected against lethal HSV-2 challenge. Herein, we extended these findings using flow cytometry to profile the cellular infiltrate. IL-36γ significantly (p < 0.0001) induced transient neutrophil infiltration, but did not impact monocyte or macrophage recruitment. Using IL-36γ−/− mice in a lethal HSV-2 challenge model, we show that neutrophils were significantly (p < 0.0001) depleted at 1- and 2-days post infection, and that mature neutrophil recruitment was impaired. In addition, IL-36γ−/− mice develop genital disease more rapidly (p < 0.0001), have significantly (p < 0.0001) reduced survival time, and display an increased incidence (p < 0.0001) of neurologic disease compared to wild type mice. IL-36γ−/− mice exhibited a significant (p < 0.05) delay in clearance of the virus from the vaginal epithelium, and analysis of virus spread to the spinal cord, bladder, and colon demonstrated that HSV-2 spread significantly (p < 0.05) more quickly in IL-36γ−/− mice. Further, we detected productive HSV-2 infection in the brainstem of IL-36γ−/− mice significantly (p < 0.0001) more frequently than in wild type mice. Ultimately, we demonstrate that IL-36γ is a key regulator of neutrophil recruitment in the vaginal microenvironment and may function to limit HSV-2 neuroinvasion.