Chemistry and Biology of Celiac Sprue

描述(申请人提供)：乳糜泻是一种遗传性消化疾病，饮食中摄入来自小麦、黑麦和大麦等来源的面筋会引起炎症反应，导致小肠绒毛结构破坏。尽管其发病率很高(&gt；1：200)和严重的临床表现，但这种自身免疫性疾病的分子基础尚不清楚。对于乳糜泻患者来说，没有治疗的选择，这种疾病的唯一“治疗”就是终生坚持严格的无面筋饮食。我们的长期目标是了解Celiac Sprue的生化基础，并将这些见解转化为药理学试剂，使患者能够安全地将这些原本有营养且极其常见的食物重新纳入他们的饮食中。 最近，从面筋蛋白的初级序列中发现了几个富含Pro和Gin的表位，这些表位只能被来自腹水患者的肠源性T细胞识别，而不能被对照识别。其中最有效的表位有三个显著的特性。首先，它们对胃、胰腺和肠道刷状边界酶的蛋白质分解具有异常的抵抗力。其次，它们是组织转谷氨酰胺酶(TG2)的高亲和力底物，TG2是与这种自身免疫性疾病相关的主要自身抗原。第三，TG2催化反应的去酰胺化产物是人类白细胞抗原-DQ2的高亲和力配体，人类白细胞抗原-DQ2是一种II类主要组织相容性复合体，存在于90%的腹水患者中。对于腹腔炎的发病机制，已经出现了一个工作模型。根据该模型，当饮食面筋被炎性(CD4+)T辅助细胞以TG2和DQ2依赖的方式识别时，主要诱导肠道绒毛损伤。在某种程度上，这是一个有效的模型，可以通过以下两种方式开发一种替代无面筋饮食的治疗方法：(I)在腹腔饮食中添加能够水解蛋白水解性免疫原性面筋表位的外源Pro-内肽酶，或(Ii)局部抑制小肠组织中的TG2，或(Iii)抑制人类白细胞抗原-DQ2介导的面筋向疾病特异性T细胞的呈递。 我们建议进行生化研究，以了解饮食面筋在腹腔病人的小肠中触发免疫毒性反应的机制。提出了以下具体目标：1)鉴定与生理相关的免疫原性面筋多肽；2)利用Pro内肽酶对抗面筋蛋白毒性效应的可行性；以及3)阐明组织转谷氨酰胺酶在面筋蛋白炎症反应中的作用。除了揭示导致面筋诱导的肠病的复杂级联反应中最早的分子事件外，这些研究还将为开发治疗乳糜泻的方法提供基本基础。

DESCRIPTION (provided by applicant): Celiac Sprue is a hereditary digestive disease in which dietary exposure to gluten from sources such as wheat, rye and barley induces an inflammatory response, leading to destruction of the villous structure of the small intestine. Despite its high prevalence (>1:200) and serious clinical manifestations, the molecular basis of this autoimmune disorder is unclear. There is no therapeutic option available to Celiac Sprue patients, and the only "treatment" of this disease is lifelong adherence to a strict gluten-flee diet. Our long-term goals are to understand the biochemical basis of Celiac Sprue, and to translate these insights into pharmacological agents that could allow patients to safely re-incorporate these otherwise nutritious and extremely common foodgrains into their diet. Recently, several Pro- and Gin-rich epitopes have been identified from primary sequences of gluten proteins that are exclusively recognized by gut-derived T cells from Celiac patients but not controls. The most potent of these epitopes have three remarkable properties. First, they are unusually resistant to proteolysis by gastric, pancreatic and intestinal brush border enzymes. Second, they are high-affinity substrates of tissue transglutaminase (TG2), the predominant auto-antigen associated with this autoimmune disorder. Third, the deamidated products of the TG2 catalyzed reaction are high-affinity ligands for HLA-DQ2, a class II major histocompatibility complex present in >90% of Celiac Sprue patients. A working model has emerged for the pathogenesis of Celiac Sprue. According to this model, intestinal villous damage is primarily induced when dietary gluten is recognized by inflammatory (CD4+) T-helper cells in a TG2-dependent and DQ2-dependent manner. To the extent this is a valid model, it may be possible to develop a therapeutic alternative to a gluten-free diet by either (i) supplementing the Celiac diet with an exogenous prolyl endopeptidase capable of hydrolyzing proteolytically resistant immunogenic gluten epitopes, or (ii) local inhibition of TG2 in small intestinal tissue, or (iii) inhibiting HLA-DQ2 mediated presentation of gluten to disease-specific T cells. We propose to conduct biochemical studies to understand the mechanisms by which dietary gluten triggers an immunotoxic response in the small intestine of a Celiac patient. The following Specific Aims are proposed: 1) Identification of physiologically relevant immunogenic gluten peptides; 2) Fundamental studies on the feasibility of using prolyl endopeptidases to counter the toxic effects of gluten; and 3) Elucidating the role of tissue transglutaminase in the inflammatory response to gluten. In addition to shedding light on the earliest molecular events in the complex cascade that leads to gluten-induced enteropathy, these studies will provide a fundamental basis for developing a therapeutic approach to Celiac Sprue.