旋毛虫有效抗原成分诱导宿主肠道区域性Treg细胞在炎症性肠病中的作用及其机制

Helminth and helminth derived molecules could contribute to the precaution and improvement in the progression of autoimmune disease, however, the mechanism need to be further determined. Inflammatory bowel disease(IBD) is caused by that the intestinal mucosal immune system executes overreaction which results in tissue lesion. Our previous study indicated that excretory/secretory antigens of Trichinella spiralis (TsES) and paramyosin of Trichinella spiralis (TsPmy) could induce the production of Treg, and facilitate anesis in ulcerative colitis (UC) simulated by dextran sulphate sodium (DSS). Therefore, we propose the hypothesisthat helminth therapy may inhibit the occurrence and development of IBD through inducing immune homeostasis by the proliferation of Treg in gastrointestinal tract. Here we design to investigate the roles of the gastrointestinal tract-specialized regional Tregs induced by TsES and TsPmy during the UC progression, as well as the plasticity and distribution of these Tregs in gut, the relation between these Tregs and intestinal bacteria, and how these Tregs could be recruited to the site attacked by colonic inflammation. We intend to clarify the mechanisms that these Tregs inhibit the occurrence and development of UC. It is expected to greatly add to the theoretical foundation in the interaction between gastrointestinal tract-specialized regional immunologic features and traditional mucosal immune system. Meanwhile, it will further illustrate the molecular mechanism of helminth therapy and provide experimental basis for the development of helminth derived molecules work as immunosuppressor used in target therapy of IBD and other autoimmune diseases.

蠕虫及蠕虫源性分子可对多种自身免疫性疾病具有预防和改善作用，但其作用机制尚不清楚。炎症性肠病(IBD)是因患者肠黏膜免疫系统反应过度而导致组织损害。前期研究表明，旋毛虫排泄分泌抗原（TsES）及副肌球蛋白（TsPmy）能够诱导Treg的产生，并能够缓解葡聚糖硫酸钠（DSS）诱导的溃疡性结肠炎（UC）。由此，我们提出科学假设：“蠕虫疗法”可通过诱导肠道区域性Treg细胞的产生建立免疫稳态，从而抑制IBD的发生发展。本研究通过观察TsES和TsPmy诱导的肠道区域性Treg细胞在抑制UC过程中的作用，明确该群肠道区域性Treg细胞的功能，进而阐明该群Treg细胞之于UC的作用机制。本课题将为肠道区域免疫特性结合传统的黏膜免疫系统发挥免疫作用提供新的理论依据，同时将进一步完善 “蠕虫疗法”的分子机制，为开发虫源分子抗原作为免疫抑制药物发挥靶向治疗IBD以及其他免疫性疾病提供实验依据。

蠕虫及蠕虫源性分子可对多种自身免疫性疾病具有预防和改善作用，但其作用机制尚不清楚。炎症性肠病(IBD)是因患者肠黏膜免疫系统反应过度而导致组织损害。前期研究表明，旋毛虫成虫排泄分泌抗原（TsAES）及副肌球蛋白（TsPmy）能够诱导Treg的产生，并能够缓解葡聚糖硫酸钠（DSS）诱导的溃疡性结肠炎。本课题利用DSS诱导的急性结肠炎模型与幼稚性T细胞诱导的慢性结肠炎模型，发现TsAES和TsPmy诱导的结肠区域性Treg可缓解结肠炎进展。TsAES具有TGF-β样活性，体内外均可诱导小鼠结肠固有层外周Treg（pTreg）数量增多，其机制是TsAES通过活化DC细胞促使CD4+ T细胞分化为Treg。尾静脉回输TsAES诱导的pTreg可明显减缓急性结肠炎的发展。TsPmy可通过增加结肠固有层tTreg的丰度而非pTreg，上调结肠微环境IL-10和TGF-β的水平来降低疾病评分指数，减轻结肠病理损伤、减少炎性细胞浸润，下调结肠促炎细胞因子的水平。在结肠炎进程中，TsPmy增强结肠固有层Treg的稳定性与抑制功能。一方面，TsPmy上调了结肠固有层Treg中GATA3的表达以及Th17中Foxp3的表达，同时下调了结肠固有层Treg中IL-17A的分泌水平，避免Treg向Th17的炎性转化。本研究发现TsPmy在结肠固有层诱导的Th2型免疫反应可能促进了GATA3+ Treg向炎症结肠累积。另一方面，TsPmy在炎性环境中维持结肠固有层效应性Treg（CD62loCD44hi eTregs）的分化，同时上调Treg中抑制性共刺激分子CTLA4与TIGIT的表达。应用流式细胞术与结肠原位免疫荧光法，发现TsPmy增强结肠固有层Treg中结肠特异性归巢受体GPR15的表达。过继转移实验证实TsPmy增强Treg归巢至结肠的能力，且增加GPR15+ Treg再一次归巢至结肠的数量。因此，TsPmy可能通过上调结肠特异性归巢受体GPR15的表达，促进胸腺来源的tTreg归巢至结肠，以增强结肠Treg的稳定性与抑制功能，进而减缓小鼠结肠炎。本课题以结肠区域性Treg为切入点，首次系统性阐释了蠕虫单一分子蛋白诱导的结肠区域性Treg在炎性环境中维持肠道粘膜免疫稳态的机制，为蠕虫源性蛋白靶向肠道区域性Treg减缓IBD提供了理论基础和实验依据。