IRF5 risk variants contribute to pre-symptomatic SLE by enhancing the levels of circulating NET antigens

Abstract

Abstract SLE is a complex multifactorial autoimmune disease characterized by high levels of autoantibodies that impact many organs. Neutrophil extracellular traps (NETs) are a potential source of antigen leading to the production of autoantibodies, as antibodies against NET components are detected in SLE patients. Higher level of NETs and decreased clearance of NETs are associated with SLE and other autoimmune diseases. Neutrophils play an key role in pediatric lupus and NETs from pediatric lupus patients activate plasmacytoid dendritic cells (pDCs) to produce high levels of IFN-α. Polymorphisms within and around the IRF5 gene associate with risk of developing SLE. We previously reported that healthy donor neutrophils from IRF5 homozygous risk carriers underwent increased spontaneous NETosis, as compared to non-risk donors, that resulted in increased IFN-α production, plasma cell differentiation and autoantibody production. Whether the observed increase in neutrophil-mediated ETosis is a systemic signature of IRF5-driven pre-symptomatic SLE is not known, nor is it known whether these IRF5 risk carriers have defects in NET clearance. We thus developed and optimized new assays to detect small quantities of NET remnants in plasma samples using a combined MPO-CitH3 antibody cocktail followed by detection of DNA by ELISA. Further, we designed a novel immunofluorescence technique to visualize and quantify plasma NETs in healthy donor risk and non-risk carriers, as compared to pediatric and adult SLE patients. In addition, plasma DNase 1 and DNase 1L3 levels were measured. This study will report on the mechanisms by which circulating NETs are increased in pediatric and adult SLE, as well as the contribution of IRF5 genetic risk to NET clearance. Supported by Lupus Research Alliance Department of Defense CDMRP LRP W81XWH-18-1-0674