鱼类IgT对肠道条件性致病菌的作用机制研究

鱼类肠道内栖息着大量的微生物，包括多种条件性致病菌。肠黏膜相关淋巴组织在应对维持黏膜微生物稳态中发挥重要作用，其中免疫球蛋白（Ig）是关键的效应分子之一。然而目前对于鱼类Ig在抑制条件致病菌中的功能和作用机制还不清楚。前期我们发现虹鳟IgT能结合大量黏膜表面的条件致病菌，当IgT-B细胞耗竭后，处于稳态的细菌会发生紊乱，向组织内部移位，暗示IgT在发挥着重要的免疫排斥功能。本项目拟在此基础之上，从鱼类肠黏膜角度出发，构建虹鳟IgT-B细胞的耗竭模型，采用流式细胞术分选和宏基因组测序等技术分析虹鳟IgT包被的肠道条件致病菌的变化；通过感染实验，阐明IgT对肠道条件致病菌的免疫反应规律；通过体外凝集实验、黏附实验和体内感染实验等，系统揭示虹鳟IgT结合肠道致病菌的作用机制。本项目是申请人博士阶段所做研究的延续和深化，旨在解析鱼类Ig对肠道细菌的作用机制，对鱼类黏膜疾病防控具有重要的理论意义。

Fish intestine is colonized by a vast array of intestinal microbes including many pathogenic microbial taxa. The gut-associated lymphoid tissues has developed the function in maintaining microbiome homeostasis. Fish immunoglobulin (Ig) is one of the major effector molecules, however, by far little is known about the in-depth interaction between fish Ig and intestinal microbes. Our previous study indicated IgT is the main Ig type that target many pathobions at mucosal surface in rainbow trout. IgT-depleted fish induced a profound dysbiosis, leading to a reversal of microbial translocation into mucosal tissue. These results suggested the prevailing role of IgT in immune exclusion against the mucosal bacteria. On this basis, from the perspective of fish gut mucosa, this project intends to identify the type of pathogenic microbe and the changes after IgT-depletion using the technology of flow cytometry and identification of bacteria, and strategy. Thereafter, Trout IgT immune response will be analyzed after the pathobiont infection. Finally, this project will clarify the mechanism of IgT in immune exclusion against intestinal pathobions through bacterial agglutination and adhesion test in vitro, and also infected experiment designed in IgT-depleted trout. The present project will be the continuation and extension of my preliminary study, which will illuminate the mechanism of IgT in immune exclusion and maintaining intestinal homeostasis. It is of great significance for the control of fish diseases.