Dendritic cell directed T cell negative regulation for treating autoimmunity

描述（由申请人提供）：共刺激途径被认为是T细胞激活和分化的必要条件。在遇到抗原的T细胞上操纵这些信号是诱导抗原特异性耐受性以预防和抑制自身免疫的最具吸引力的方法。在活化的T细胞上显著上调的共抑制剂/抑制受体（负调节因子），是近年来作为治疗靶点受到关注的分子。抗原特异性耐受的诱导依赖于TCR和一个或多个这些抑制受体的同时作用。有趣的是，我们的研究表明，这种T细胞耐受性主要与抗原特异性调节性T细胞（Tregs）的诱导和/或扩增有关。抗原特异性Tregs可以抑制效应T细胞反应，并提供长期持续的自身免疫保护。我们的假设是，抑制受体和TCR在抗原特异性T细胞上的主导作用，通过树突状细胞（dc）来稳定地过表达负调节配体，将诱导有效的持久抗原特异性T细胞耐受。到目前为止，我们的研究已经证明，通过DC定向方法将抗原特异性的抑制受体结合到T细胞上，可以在体外和体内诱导抗原特异性T细胞反应的显著抑制和低增殖T细胞的产生，这些T细胞具有产生大量抑制细胞因子的能力，如IL-10和TGF-21。因此，我们采用外源稳定过表达T细胞抑制受体CTLA-4、PD-1和BTLA特异性配体B7.1wa、PD-L1和hvemm - crd1的方法来产生耐受性APCs。这些dc可以将抗原呈递给T细胞，同时以增强的强度与T细胞的抑制受体结合。这些耐受性dc可以诱导抗原特异性T细胞和促炎细胞因子反应的深度抑制，但增强抗炎细胞因子反应。该系统利用了DC的特殊抗原呈递特性以及工程DC主要与活化T细胞上的抑制受体结合的能力。这种过表达dc的负调节配体也可以作为研究抗原呈递过程中T细胞抑制受体增强结合效应的有力工具。本研究的目的是：1)了解过表达T细胞抑制受体配体的dc诱导和维持抗原特异性T细胞低反应性和耐受性的潜力；2)了解增强T细胞抑制受体连接诱导信号传导的机制以及对效应T细胞功能和分化的相关影响。3)利用T细胞介导的自身免疫性疾病模型表征负调节因子过表达dc的治疗潜力。公共卫生相关性：本项目将利用树突状细胞（dc）的专业抗原提呈特性和T细胞抑制受体（负调节因子）的强大抑制信号相结合，实现调节T细胞功能和诱导抗原特异性T细胞低反应性和耐受性的目标。这将通过外源性过表达具有T细胞抑制受体特异性配体（CTLA-4， PD-1和BTLA）的dc来实现，并将感兴趣的抗原(s)装载在它们上，通过在抗原呈递过程中传递抑制信号来积极抑制T细胞。通过产生适应性低反应性和调节性T细胞诱导抗原特异性T细胞耐受将是治疗自身免疫和移植物排斥反应的最有效方法，我们相信，我们提出的方法将是实现这一目标的最有效方法之一。此外，这种方法将是研究抗原呈递过程中T细胞抑制受体增强结合效应的有效方法之一。我们的研究将对治疗自身免疫的方法产生巨大的影响，同时避免机会性感染的风险，并消除终身使用一般免疫抑制剂治疗的需要。

DESCRIPTION (provided by applicant): Costimulatory pathways are considered essential for T cell activation and differentiation. Manipulating these signals on antigen encountered T cells is a most attractive approach for inducing antigen specific tolerance to prevent and suppress autoimmunity. Co-inhibitors/repressor-receptors (negative regulators) that are upregulated significantly on activated T cells, and have been the molecules of attention as targets for therapy in last several years. Induction of antigen specific tolerance depends on concurrent engagement of the TCR and one or more of these repressor-receptors. Interestingly, our studies have shown that this T cell tolerance is mostly associated with an induction and/or expansion of antigen specific regulatory T cells (Tregs). Antigen specific Tregs can suppress effector T cell response and provide long-term sustained protection from autoimmunity. Our hypothesis is that dominant engagement of repressor-receptors along with TCR on antigen specific T cells using dendritic cells (DCs) engineered to stably overexpress negative regulatory ligands will induce effective long-lasting antigen specific T cell tolerance. Our studies have so far demonstrated that antigen specific engagement of repressor-receptors on T cells by DC directed approaches could induce significant suppression of antigen specific T cell response and generation of hypo- proliferative T cells with the ability to produce large amounts of suppressor cytokines such as IL-10 and TGF-21 both in vitro and in vivo. Therefore, the approach of stable exogenous over-expression of ligands, B7.1wa, PD-L1, and HVEM-CRD1 that are specific for T cell repressor-receptors, CTLA-4, PD-1 and BTLA is adopted for generating tolerogenic APCs. These DCs can present antigen to T cells and simultaneously engage their repressor-receptors with an enhanced strength. These tolerogenic DCs could induce profound suppression of antigen specific T cell and pro-inflammatory cytokine responses, but enhanced anti- inflammatory cytokine responses. The exceptional antigen presenting properties of DCs combined with the engineered DC's ability to predominantly engage repressor-receptors on activated T cells are exploited in this system. This negative regulatory ligand over-expressing DCs can also be a powerful tool to study the effect of enhanced engagement of T cell repressor-receptors during the antigen presentation. This study will be aimed at 1) understanding the potential of DCs that are over-expressing ligands for T cell repressor- receptors to induce and maintain antigen specific T cell hypo-responsiveness and tolerance, 2) understanding the mechanism of enhanced T cell repressor-receptor ligation induced signaling and the associated effects on effector T cell function and differentiation, and 3) characterizing the therapeutic potential of negative regulator over-expressing DCs using a T cell mediated autoimmune disease model. Public Health Relevance: This project will exploit the professional antigen presenting properties of dendritic cells (DCs) and the powerful inhibitory signals of T cell repressor-receptors (negative regulators) combined to achieve the goal of modulating T cell function and inducing antigen specific T cell hypo-responsiveness and tolerance. This will be achieved by exogenously over-expressing DCs with ligands specific for T cell repressor-receptors (CTLA-4, PD-1 and BTLA) and loading them with the antigen(s) of interest for actively suppressing T cells though delivering inhibitory signals during antigen presentation. Inducing antigen specific T cell tolerance by generating adaptive hypo-responsive and regulatory T cells will be the most effective way of treating autoimmunity and graft rejection and, we believe that, our proposed approach will be one of the most efficient ways of achieving that goal. Moreover, this approach would be one of the efficient ways to study the effect of enhanced engagement of T cell repressor-receptors during antigen presentation. Our study will have an immense impact on approaches to treat autoimmunity without risking opportunistic infections as well as by eliminating the need for a life-long treatment using general immunosuppressive agents.