PROJECT SUMMARY In the United States, herpes simplex virus type 1 (HSV-1) infects more than half the adult population and is the leading cause of viral encephalitis and infectious blindness. Yet, the host factors contributing to the most severe manifestations of HSV-1 remain unclear. Inflammasomes, a recently discovered antiviral innate immune defense, and the production of two inflammasome cytokines (interleukin (IL)-1and IL-18) are critical in HSV-1 control and pathogenesis. However, how inflammasomes are regulated during HSV-1 infection is poorly understood. Recently, leucine-rich repeat kinase 2 (LRRK2) has emerged as a possible regulator of inflammasome signaling. LRRK2 has been studied extensively because specific alleles are associated with Parkinson’s disease, Crohn’s disease, cancer, and leprosy. Despite the disease associations, the precise function of LRRK2 and how it mediates disease are unknown. Evidence for a role in the immune response include that LRRK2 is highly expressed on immune cells, is upregulated in response to infection, and was recently shown to modulate the NLRC4 inflammasome in response to bacterial infection. We recently demonstrated that NLRP3 is critical in inflammasome activation by HSV-1, and our preliminary data indicate that LRRK2 enhances NLRP3 signaling. We found that the common LRRK2 mutation G2019S enhances HSV- 1 pathology in mice without altering viral replication. These results point to a novel role for LRRK2 in inflammasome signaling and HSV-1 pathogenesis. We hypothesize that LRRK2 modulates inflammasome signaling in response to HSV-1 infection and that the G2019S mutation further enhances inflammasome activation in vivo, leading to more severe eye, skin, and central nervous system (CNS) pathology after HSV-1 infection. LRRK2 has not been studied in human viral infection, and these represent the first studies to define its role in the pathogenesis of a common neurotropic human viral infection. In Aim 1, we will identify how LRRK2 associates with NLRP3, the critical inflammasome adapter in HSV-1 infection, and how mutations in LRRK2 alter inflammasome signaling in the context of HSV-1 infection. We will accomplish this by using targeted mutagenesis in a transfection model of inflammasome signaling and by studying inflammasome activation after HSV-1 infection of cell lines stably expressing LRRK2 mutants. For Aim 2, we will determine how LRRK2 alters the inflammasome response to HSV-1 using LRRK2 transgenic mice and mice with inflammasome gene disruptions. Additionally, the PI will gain critical skills and expertise necessary to study the innate immune response to HSV-1 and other herpesviruses. These learning objectives will be accomplished through formal coursework, scientific programing, and direct mentorship by experts in viral and murine immunology, herpesvirology, and biostatistics. The proposed career development plan and research aims will provide a pathway to a career as an independent investigator studying the interactions between herpesviruses and the innate immune system.

Project Narrative Herpes simplex virus type 1 (HSV-1) infects more than half the adult population of the United States and remains the most common cause of viral encephalitis and infectious blindness, yet the pathogenesis of these most severe manifestations remain unclear. We have identified leucine-rich repeat kinase 2 (LRRK2) as a novel pathogenic determinant of severe HSV-1 infection. We propose to determine how LRRK2 and the common LRRK2 mutation, G2019S, alter the innate immune response to HSV-1, expanding our understanding of severe herpesvirus pathology and finding novel therapeutic opportunities to ameliorate the most morbid outcomes caused by this ubiquitous virus.