Identification of a prostate antigen recognized by endogenous regulatory T cells

描述（由申请人提供）：调节性T细胞（T细胞）在调节对外来、自身和肿瘤相关抗原的免疫应答中的关键作用已经引发了对开发用于治疗自身免疫和癌症的T细胞操作策略的相当大的兴趣.尽管在这一领域取得了重大进展，但在知识方面仍然存在重大差距。虽然大量的证据是一致的假设，胸腺衍生的胸腺识别自身抗原，这些自身抗原的身份和性质仍然未知。这种缺口的持续存在仍然是一个重要的问题，因为Treg生物学的许多方面高度依赖于抗原识别，包括发育、外周稳态、解剖分布、激活状态和抑制功能。因此，缺乏关于Treg抗原的身份和性质的知识限制了该领域的进展，并限制了选择性扩增或耗尽抗原特异性Treg用于治疗自身免疫和癌症的能力。长期目标是了解Foxp 3 + T细胞在维持免疫耐受和调节癌症进展中的发展、抗原特异性和功能。本提案的目的/具体目的是鉴定被称为MJ 23 Tcls的前列腺特异性Tcls内源性群体识别的抗原。中心假设是MJ 23 TcR识别来自胸腺中自身免疫调节因子（Aire）依赖性转录物编码的蛋白质的前列腺相关自身肽。该假设基于申请人实验室先前发表的数据。为了实现这一目标，将利用三种互补的方法：1）筛选胸腺中由Aire依赖性前列腺特异性转录物编码的候选蛋白; 2）筛选由前列腺衍生的cDNA表达文库编码的抗原; 3）从分离自原发性前列腺组织的分级提取物中对抗原进行生化鉴定。该提议通过使用创新的模型系统而成为可能，该模型系统提供了在不同解剖部位（前列腺肿瘤）富集的抗原的可再现来源和用于鉴定该抗原的T细胞探针。拟议的工作意义重大 因为抗原的鉴定将弥补知识上的关键空白，并开辟目前不可能的新的研究领域。这些领域包括：1）在器官特异性耐受性、炎症和癌症的背景下使用肽- MHC多聚体试剂分析内源性抗原特异性TCLs; 2）通过施用外源性抗原扩增前列腺特异性TCLs治疗自身免疫的临床前研究; 3）研究，其中的功能，贩运，MJ 23 T细胞的生物学和稳态可以通过抗原的调节性转基因过表达或条件性缺失来分析; 4）MJ 23 T细胞的生物物理学阐明， MJ 23 TCR与抗原配体结合的亲和力和动力学，以及三元复合物的晶体结构的测定。

DESCRIPTION (provided by applicant): The critical role of regulatory T cells (Tregs) in the regulation of immune responses to foreign, self, and tumor- associated antigens has sparked considerable interest in the development of strategies for the manipulation of Tregs for the treatment of autoimmunity and cancer. Despite substantial progress in the field, a critical gap in knowledge remains. Although substantial evidence is consistent with the hypothesis that thymic-derived Tregs recognize self antigens, the identity and nature of these self antigens remain unknown. Continued existence of this gap remains an important problem because many aspects of Treg biology are highly dependent on antigen recognition, including development, peripheral homeostasis, anatomical distribution, activation status, and suppressive function. Thus, the lack of knowledge regarding the identity and nature of Treg antigens has restricted progress in the field and limited the ability to selectively expand or deplete antigen-specific Tregs for the treatment of autoimmunity and cancer. The long-term goal is to understand the development, antigen specificity, and function of Foxp3+ Tregs in the maintenance of immune tolerance and the modulation of cancer progression. The objective / specific aim of this proposal is to identify the antigen recognized by an endogenous population of prostate-specific Tregs, termed MJ23 Tregs. The central hypothesis is that MJ23 Tregs recognize a prostate-associated self peptide derived from a protein encoded by Autoimmune regulator (Aire)-dependent transcripts in the thymus. This hypothesis is based on previously published data from the applicant's laboratory. To achieve the objective, three complementary approaches will be utilized: 1) screening of candidate proteins encoded by Aire-dependent, prostate-specific transcripts in the thymus; 2) screening of antigens encoded by a prostate-derived cDNA expression library; 3) biochemical identification of the antigen from fractionated extracts isolate from primary prostate tissue. The proposal is made possible by use of an innovative model system that provides both a reproducible source of antigen enriched at a distinct anatomical site (prostate tumors) and a T cell probe for identifying this antigen. The proposed work is significant because identification of the antigen will bridge critical gaps in knowledge and open new areas of investigation that are not currently possible. These areas include: 1) analysis of endogenous, antigen-specific Tregs using peptide- MHC multimer reagents in the context of organ-specific tolerance, inflammation, and cancer; 2) pre-clinical research for the treatment of autoimmunity by expansion of prostate-specific Tregs via administration of exogenous antigen; 3) studies in which the function, trafficking, and homeostasis of MJ23 Tregs can be analyzed via regulated transgenic overexpression or conditional deletion of the antigen; 4) biophysical elucidation of the affinity and kinetics of MJ23 TCR binding to the antigenic ligand, and determination of the crystal structure of the ternary complex.