Mechanisms and Therapeutic Modulation of T Cell Autoimmune Responses in Sjogren's Syndrome

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Project Summary Sjӧgren’s syndrome (SjS) is an autoimmune disease affecting the oral and systemic health of 4 million Americans. Characterized by chronic inflammation and dysfunction of exocrine glands, SS causes dry mouth, dry eyes and various systemic health problems, with no cure or effective biological therapy available. The objective of this R01 project is to elucidate the negative impact of IL-7 and Th1 cytokines on Treg function in SjS disease, and to test if enhancing TCF1 and Tim-3 in Tregs can improve and enhance their suppressor function, resistance to IL-7/Th1 cytokines, and the ability to ameliorate SjS. Tregs in SjS-prone non-obese diabetic mice are functionally impaired. Pro-inflammatory cytokines, including Th1 cytokines IFNγ and IL-12, can impair the function and stability of Tregs to promote autoimmune inflammation. Our preliminary studies yielded important evidence for the formation of our central hypothesis that IL-7 and Th1 cytokines contribute to aberrant Treg function in SjS conditions, in part by downregulation of TCF1 and Tim-3, and that enhancing the expression/activity of TCF1 and Tim-3 may improve and boost the immunosuppressive function, stability and SjS-attenuating ability of these Tregs. In Aim 1, we will determine if forced expression of TCF1 in Tregs with lentiviral gene expression vectors can improve/enhance their immunosuppressive function, stability under inflammatory conditions, and ability to ameliorate SjS. In vitro Treg functional assays and in vivo Treg transfer to SjS mouse model will be employed. In Aim 2, we will determine if enhancing Tim-3 activity or expression in Tregs can improve and boost their immune-regulatory and SjS-attenuating function. We will enhance Tim-3 activation or expression using several approaches, including in vivo injection of Tim-3 ligand, in vitro stimulation of Tregs with Tim-3 ligand, and force-expressing Tim-3 in Tregs using lentiviral vectors. We will test if enhancing Tim-3 expression/activation can improve/boost the immunosuppressive function of normal and SjS-affected mouse and human Tregs. In Aim 3, we will comprehensively define the transcriptomic changes in mouse and human Tregs associated with SjS and induced by IL-7 and Th1 cytokines with high throughput NGS RNA- sequencing, which will identify new molecular players and pathways underlying the defective Treg function in SjS and induced by IL-7 and Th1 cytokines. Completion of this project will address a critical knowledge gap and advance both basic understanding and translational modulation of Treg function and stability, which could lead to development of Treg-based strategies for ameliorating SjS and various other autoimmune diseases in future.