Molecular Dissection of Insulin Targeting in Anti-Islet Autoimmunity

描述(申请人提供)：主要组织相容性复合体(MHC)II类基因座与1型糖尿病的风险密切相关，导致糖尿病的自身免疫的组织特异性可能由MHC分子、抗原和T细胞受体(TCR)组成的三分子复合体决定。我们假设，这种三分子复合体的成分之间的相互作用，所有这些成分都在胚系中编码，决定了T细胞参与1型糖尿病发展的性质。靶向胰岛素B链9-23氨基酸多肽(胰岛素B：9-23)很可能是自发性糖尿病动物模型NOD小鼠胰岛炎症启动的重要决定因素。我们最近发现，含有胚系编码的可变区基因(Vgene)序列的TCRs，称为TRAV5D-4，通过识别胰岛素B：9-23肽，在诱导抗胰岛自身免疫中起着关键作用。因此，由胰岛素B：9-23肽和TRAV5D-4 TCRα链组成的三分子复合体在抗胰岛自身免疫中起着关键作用；然而，表达TRAV5D-4 TCR的T细胞如何参与疾病的发生和发展仍有待阐明。有证据表明，DQ8糖尿病易感的HLAII类分子是呈现胰岛素B：9-23肽的NOD I-Ag7的同源基因，并且表达TRAV13-1(人的TRAV5D-4的同源基因)TCRα链的T细胞主要存在于患有DQ8的1型糖尿病患者的胰腺中，这一建议的最终目标是验证一项概念的证据，即通过特定的生殖系编码的TVCR基因基序进行胰岛素靶标在胰岛自身免疫的发展中起关键作用。在这项研究中，我们的目标是利用NOD小鼠模型(目标1)确定TCRs，特别是那些含有TRAV5D-4的TCR如何靶向关键多肽-胰岛素B：9-23，启动胰岛炎症的分子机制，并确定表达TRAV5D-4的T细胞是否对NOD小鼠的糖尿病发展是必要的(目标2)。如果在缺乏TRAV5D-4的情况下，抗胰岛自身免疫的发展被完全抑制，那么只针对表达这种基本Trav基因的T细胞将使我们能够开发出一种副作用最小的强大的免疫疗法。最后，我们将继续假设，在由胰岛素B：9-23肽和TRAV13-1 TCRV基因基序组成的人三分子复合体中存在概念上类似的相互作用，这是导致人类1型糖尿病易感性的原因(目标3)。这一提议的发现将提供对通过胰岛素三分子内的相互作用启动胰岛自身免疫的潜在原理的更深入的理解。 最终将用于设计基于抗原的人类1型糖尿病免疫诊断和免疫治疗临床研究。

DESCRIPTION (provided by applicant): The major histocompatibility complex (MHC) class II locus is strongly associated with the risk of type 1 diabetes, and tissue specificity of the autoimmunity causing diabetes is likely to be determined by the trimolecular complex composed of an MHC molecule, an antigen, and a T cell receptor (TCR). We hypothesize that the interactions between components of this trimolecular complex, all of which are encoded in the germline, determines the nature of T cells involved in the development of type 1 diabetes. Targeting of an insulin B chain 9-23 amino acid peptide (insulin B:9-23) is highly likely to be an essential determinant in the initiation of islet inflammation in the spontaneous diabetes animal model, NOD mouse. We recently discovered that TCRs containing the germline-encoded variable gene (Vgene) sequence called "TRAV5D-4" play a critical role to induce anti-islet autoimmunity via the recognition of insulin B:9-23 peptide. Thus, the trimolecular complex consisting of the insulin B:9-23 peptide and TRAV5D-4 TCR alpha chain plays a key role in developing anti-islet autoimmunity; however, how T cells expressing TRAV5D-4 TCRs contribute to the initiation and development of the disease remains to be elucidated. Given evidence that the DQ8 diabetes- susceptible HLA class II molecule is an ortholog of NOD I-Ag7 presenting the insulin B:9-23 peptide and that T cells expressing TRAV13-1 (human ortholog of TRAV5D-4) TCR alpha chains dominantly exist in the pancreas of a type 1 diabetes patient having DQ8, the ultimate goal of this proposal is to verify a proof of concept that insulin targetig by a specific germline-encoded TCR Vgene motif plays a critical role in the development of islet autoimmunity. In this proposal, we aim to determine the molecular mechanism of how TCRs, in particular those containing TRAV5D-4, target the critical peptide, insulin B:9-23, to initiate isle inflammation using the NOD mouse model (Aim 1), and to determine whether T cells expressing TRAV5D-4 are essential for diabetes development in NOD mice (Aim 2). If the development of anti-islet autoimmunity is completely suppressed in the absence of TRAV5D-4, targeting only T cells expressing such essential TRAV genes will enable us to develop a robust immunotherapy with the minimum of side effects. Finally, we will pursue the hypothesis that there is a conceptually similar interaction in the human trimolecular complex consisted of the insulin B:9-23 peptide and TRAV13-1 TCR Vgene motif underlying susceptibility to human type 1 diabetes (Aim 3). Findings from this proposal will provide a deeper understanding of the principles underlying the initiation of islet autoimmunity via the interaction within the insulin trimolecular complex, which will ultimately to be applied to design antigen-based immunodiagnostic and immunotherapeutic clinical studies for type 1diabetes in humans.