Chemistry and Biology of Celiac Sprue

描述（由申请人提供）：乳糜泻是一种遗传性消化系统疾病，其中饮食暴露于来自小麦、黑麦和大麦等来源的麸质诱导炎症反应，导致小肠绒毛结构破坏。尽管其患病率高（>1：200）和严重的临床表现，这种自身免疫性疾病的分子基础尚不清楚。乳糜泻患者没有治疗选择，这种疾病的唯一“治疗”是终身坚持严格的麸质饮食。我们的长期目标是了解乳糜泻的生化基础，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营养丰富且非常常见的食物重新纳入他们的饮食中。 最近，已经从麸质蛋白的主要序列中鉴定了几个富含Pro和Gin的表位，这些表位仅被来自乳糜泻患者但不被对照的肠源性T细胞识别。这些表位中最有效的表位具有三个显著的特性。首先，它们对胃、胰腺和肠刷状缘酶的蛋白水解具有不同寻常的抗性。其次，它们是组织转氨酶（TG 2）的高亲和力底物，组织转氨酶是与这种自身免疫性疾病相关的主要自身抗原。第三，TG 2催化反应的脱酰胺产物是HLA-DQ 2的高亲和力配体，HLA-DQ 2是一种存在于>90%的乳糜泻患者中的II类主要组织相容性复合体。一个工作模型已经出现了乳糜泻的发病机制。根据该模型，肠绒毛损伤主要是在饮食麸质被炎性（CD 4+）T辅助细胞以TG 2依赖性和DQ 2依赖性方式识别时诱导的。在这是有效模型的程度上，可以通过以下方式开发无麸质饮食的治疗替代方案：（i）用能够水解蛋白水解抗性免疫原性麸质表位的外源脯氨酰内肽酶补充腹腔饮食，或（ii）在小肠组织中局部抑制TG 2，或（iii）抑制HLA-DQ 2介导的麸质向疾病特异性T细胞的呈递。 我们建议进行生化研究，以了解膳食麸质引发乳糜泻患者小肠免疫毒性反应的机制。提出了以下具体目的：1）鉴定生理学相关的免疫原性谷蛋白肽; 2）关于使用脯氨酰内肽酶对抗谷蛋白的毒性作用的可行性的基础研究;和3）阐明组织转氨酶在对谷蛋白的炎症反应中的作用。除了阐明导致麸质诱导性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乳糜泻的治疗方法提供基础。

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.