Genome-wide association studies (GWAS) have identified immune pathways linked to the pathogenesis of systemic lupus erythematosus (SLE). However, despite these insights, our understanding of how individual genetic variants promote autoimmunity remains poor. Loss-of-function mutations in genes of the phagocytic NADPH oxidase complex (NOX2), including NCF1 and NCF2, have been linked with the pathogenesis of SLE and other humoral autoimmune diseases. The current model for how reduced NOX2 activity promotes lupus development focuses on defects in the clearance of apoptotic material by phagocytic myeloid lineages. While myeloid defects likely contribute to disease risk, we hypothesize that a parallel B cell-intrinsic mechanism underlies the profound increase risk of SLE in human carriers of NCF1 and NCF2 variants. In addition to the production of pathogenic autoantibodies, recent studies have demonstrated that B cells can promote lupus pathogenesis by initiating immune tolerance breaks and facilitating the generation of spontaneous germinal centers (GC). The activation of autoreactive B cells in SLE requires B cell-intrinsic expression of the endosomal toll-like receptors TLR7 and TLR9, and our published and preliminary data show that reduced NOX2 activity results in dysregulated endosomal TLR signaling by impacting non-canonical autophagy pathways. Based on these data, we hypothesize that a B cell-specific reduction in NOX2 activity will result in enhanced TLR- dependent GC formation and the development of humoral autoimmunity. We will test this idea via parallel in vivo and in vitro mechanistic studies.
In Aim 1, we will test whether B cell-intrinsic deletion NOX2 component genes results in enhanced TLR-dependent GC responses using a well-characterized model of viral infection.
In Aim 2, we will study whether reduced NOX2 activity promotes autoantibody production and humoral autoimmunity in murine SLE. Finally, in Aim 3, we will use biochemical and cell imaging approaches to test whether NAPDH oxidase activity impacts B cell TLR signaling and non-canonical autophagy pathways using both murine genetic models and gene-edited human B cells. Together, these studies promise to advance our understanding of lupus pathogenesis and may inform the design of future targeted therapies for human SLE.
Systemic lupus erythematosus (SLE) is a chronic, multi-system disease in which the immune system damages the body's own organs and tissues. This project aims to uncover the mechanisms whereby human genetic variants conferring increased lupus risk impact B cell function and the production of pathogenic antibodies against self (termed autoantibodies). The long-term goal of these studies is to guide the development of new targeted therapies for the treatment of SLE.
