Decoding synovial CD4+ T cell antigen specificities in Rheumatoid Arthritis

Project Summary/Abstract Rheumatoid arthritis (RA) is a prevalent autoimmune disorder characterized by chronic inflammatory processes that lead to joint destruction. Immunologically, autoreactive CD4+ T cells play a central role in disease pathology and activate B cells leading to pathologic lymphoid aggregates within the synovium and autoantibody production. Although identifying the molecular targets recognized by pathogenic CD4+ T cells is a critical first step in understanding the molecular basis of RA, we still do not know the antigenic targets for the vast majority of synovial CD4+ T cells and how such reactivities relate to autoantibody responses. We have developed a pipeline for CD4+ T cell antigen discovery in RA that relies on a new, cell-based genetic-screening technology that enables mapping of TCR specificities at genome scale. Based on our preliminary single-cell transcriptomic data, we have identified several interesting CD4+ T cell populations in synovial fluid that are clonally expanded and have begun to discover their TCR targets. This proposal is a five-year research and training plan with a scientific focus on identifying the antigenic targets of clonally expanded CD4+ T cells from RA synovium and understanding how such antigens relate to autoantibody responses. We propose in Aim 1 to map the antigenic epitopes and assess the corresponding HLA-restriction of clonally expanded synovial CD4+ TCRs by performing peptidome-wide antigen discovery screens. Aim 2 dissects T cell-B cell collaboration in the arthritic joint by interrogating antibody repertoire binding specificities and performing CD4+ T cell-B cell co-culture assays. Finally in Aim 3, we will engineer an antigen discovery platform to enable our ability to uncover synovial TCR reactivities against citrullinated-peptide antigens, a prominent post-translational modification observed in RA. This study combines cutting-edge genetic and transcriptomic technologies with mechanistic work to critically evaluate the antigen-specific landscape of RA. It will provide the candidate new training in several scientific areas to pursue translational immunology research. The candidate’s immediate career development goals are to gain experience with bioinformatic analysis, antibody profiling technologies, and human immunology assays. A specific career development plan is described by both the candidate and the mentors, Dr. Stephen Elledge, an expert in functional genomics and technology development, and Dr. Michael Brenner MD, an expert in lymphocyte biology and RA, taking advantage of the powerful resources available at Brigham and Women’s Hospital and Harvard Medical School. The candidate’s long-term career goal is to attain a tenure-track faculty position leading a diverse group of collaborative scientists dedicated to studying antigen specific immune responses in rheumatic and autoimmune diseases and their potential applications for therapy.