Hybrid Peptides as Autoantigens for Diabetogenic CD4 T Cells

 描述(由申请人提供)：研究自身反应性T细胞的抗原配体一直是T1D的一个高度优先的研究目标，因为识别多肽靶标将 从而更好地了解这种自身免疫性疾病是如何发展起来的，以及它可能如何受到监管。长期以来，胰岛素一直被认为是1型糖尿病(T1D)最重要的β细胞自身抗原，但我们最近发现，另外两种分泌颗粒蛋白--嗜铬粒蛋白A(ChgA)和胰岛淀粉样多肽(IAPP)--也是自身反应性CD4T细胞抗原肽的来源。该项目第一个五年计划的目标是 主要集中在一组致病的CD4T细胞克隆的抗原鉴定，翻译后修饰(PTM)是否参与了多肽的抗原性，以及抗原肽是否可以用于诱导抗原特异性耐受的策略。我们在所有这些目标方面都取得了重大进展，但我们最值得注意的发现是在胰岛β细胞中发现了一种新的PTM，并导致胰岛素片段与其他分泌颗粒蛋白裂解产物序列之间形成杂交肽。其中两个混合胰岛素肽(HIP)已被证明对我们小组的不同T细胞克隆亚群具有高度抗原性，其中一个是ChgA反应的，另一个是IAPP反应的。我们在这个项目的第二个五年期间的假设是，自身反应性CD4T细胞的目标配体是HIPs。我们的目标将是(1)确定HIP反应性CD4T细胞在NOD小鼠发病机制与疾病预防中的作用；(2)确定人类胰岛β细胞中存在杂交肽；以及(3)检测和表征人类T1D患者和对照组的HIP反应性T细胞。这些研究的长期翻译意义在于，新试剂的潜力在于可以特异性地检测自身反应性T细胞作为人类自身免疫性糖尿病的生物标记物和/或作为诱导抗原特异性耐受的多肽。

 DESCRIPTION (provided by applicant): Investigating the antigenic ligands for autoreactive T cells has been a high priority research goal for T1D because identification of peptide targets will lead to a better understanding of how this autoimmune disease develops and how it might be regulated. Insulin has long been considered to be the most important beta cell autoantigen in type 1 diabetes (T1D), but we recently discovered that two other secretory granule proteins, chromogranin A (ChgA) and islet amyloid polypeptide (IAPP), are also the source of antigenic peptides for autoreactive CD4 T cells. The goals of the first five-year period of this project were focused on identification of antigens for a panel of pathogenic CD4 T cell clones, whether post-translational modification (PTM) was involved in peptide antigenicity, and whether antigenic peptides could be used in strategies to induce antigen-specific tolerance. Our progress with all of these objectives has been significant, but our most notable discovery has been the identification of a novel PTM occurring in islet β-cells and leading to the formation of hybrid peptides between fragments of insulin and sequences from other secretory granule protein cleavage products. Two of these hybrid insulin peptides (HIPs) have been demonstrated to be highly antigenic for different subsets of T cell clones from our panel, those that are ChgA-reactive and another set that is IAPP-reactive. Our hypothesis in the second five-year period of this project is that the target ligands for autoreactive CD4 T cells are HIPs. Our aims will be to (1) define the role of HIP-reactive CD4 T cells in pathogenesis versus prevention of disease in NOD mice; (2) establish the presence of hybrid peptides in human islet beta cells; and (3) detect and characterize HIP-reactive T cells in human T1D patients and controls. The long-term translational significance of these studies lies in the potential for new reagents that could specifically detect autoreactive T cells as biomarkers of autoimmune diabetes in humans and/or serve as peptides for induction of antigen-specific tolerance.