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T1 D的高优先级研究目标，因为肽靶点的鉴定将 从而更好地了解这种自身免疫性疾病是如何发展的，以及它是如何被调节的。胰岛素一直被认为是1型糖尿病（T1 D）中最重要的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CD 4 T细胞抗原肽的来源。该项目第一个五年期的目标是 重点是鉴定一组致病性CD 4 T细胞克隆的抗原，翻译后修饰（PTM）是否参与肽抗原性，以及抗原肽是否可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的进展都是显著的，但我们最值得注意的发现是鉴定了一种新的PTM，该PTM发生在胰岛β细胞中，并导致胰岛素片段与来自其他分泌颗粒蛋白裂解产物的序列之间形成杂合肽。这些杂合胰岛素肽（HIP）中的两种已被证明对来自我们的小组的T细胞克隆的不同子集具有高度抗原性，这些子集是ChgA反应性的，另一组是IAPP反应性的。我们在第二个五年期的假设是，自身反应性CD 4 T细胞的靶配体是HIP。我们的目标是（1）确定HIP反应性CD 4 T细胞在NOD小鼠发病机制与预防疾病中的作用;（2）确定人胰岛β细胞中杂合肽的存在;（3）检测和表征人T1 D患者和对照中的HIP反应性T细胞。这些研究的长期转化意义在于新试剂的潜力，这些新试剂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志物和/或作为诱导抗原特异性耐受的肽。

 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.