湖北钉螺Toll样受体的鉴定及其在天然免疫中功能的研究

Oncomelania hupensis is the unique intermediate host of Schistosoma japonicum, which causes the most severe parasitic disease in China. Without the development of S. japonicum larval inside the snail host, the parasite can not infect human and the other definitive hosts. But to date, the defense mechanism of O. hupensis against S. japonicum is still unknown, which make the understanding of parasite-host interaction more difficult, and of the disease control finally. As the same as the other molluscs, the main defense system of Oncomelania against pathogens is the innate immunity, with the deficiency of complex adaptive immunity. Toll like receptors were proved to be key factors to recognize pathogens during molluscs immunity. But there is still no any information about TLR of gastropod, including Oncomelania. In our previous study, through transcriptome analysis, Eight complete TLRs cDNAs of Oncomelania, 17 partial cDNAs of TLR and several moleculars related with TLR signaling pathway were identified. Which suggested that there exist TLR signaling pathway in O. hupensis. In this study, we will identify all of family members of TLRs in O. hupensis, find out the TLR which can recognize the S. japonicum specifically, and explain the function of this TLR during defense against S. japonicum infection. This will not only start the TLR research of snails, which will be very helpful to understand the innate immunity of molluscs deeply, but also explore the defense immunity of O. hupensis against S. japonicum, which will help us to understand the parasite-host relationship deeply, and finally provide us a new way to schistosomiasis control through blocking the transmission route.

日本血吸虫所致血吸虫病是我国流行最严重的寄生虫病，湖北钉螺是其唯一的中间宿主。日本血吸虫只有成功入侵钉螺、并发育为尾蚴，才能感染人。然而，有关钉螺对血吸虫感染的免疫防御机制仍一无所知。软体动物缺乏复杂的适应性免疫，天然免疫是其抵抗病原体的主要屏障。Toll样受体(TLR)是开启天然免疫的关键分子，但钉螺等腹足纲动物的TLR研究仍为空白。申请人在前期工作中，从钉螺转录组中鉴定出8种TLRs，17个TLR cDNA片段和多个TLR信号通路下游分子，提示钉螺体内存在TLR信号通路。本项目在此基础上，利用生物信息学和分子生物学技术，鉴定钉螺TLRs家族成员；研究特异性识别血吸虫感染的TLR在对血吸虫免疫防御中的功能。本项目的完成，将开启淡水螺类TLRs的研究，对认识软体动物的天然免疫具重要意义；通过探讨钉螺的免疫防御机制，有助于深入理解钉螺与血吸虫的相互关系，为最终控制血吸虫病提供科学依据。

日本血吸虫所致血吸虫病是我国流行最严重的寄生虫病，湖北钉螺是其唯一的中间宿主。日本血吸虫只有成功入侵钉螺、并发育为尾蚴，才能感染人。然而，有关钉螺对血吸虫感染的免疫防御机制仍一无所知。软体动物缺乏复杂的适应性免疫，天然免疫是其抵抗病原体的主要屏障。Toll样受体(TLR)是开启天然免疫的关键分子，但钉螺等腹足纲动物的TLR研究仍为空白。申请人利用前期研究工作中的钉螺转录组数据，结合RACE-PCR, BALST 比对，保守区域检测，开放阅读框，信号肽，跨膜区和SMART等多种生物信息学软件，和后期全长PCR验证，共鉴定了16个湖北钉螺TLR家族成员，并对其序列进行分析和进化地位的探讨。结果表明，OhTLR在结构上具有一定的保守性，但呈现多样性的特点，而且多数与腹足纲的其他软体动物存在一定的遗传距离。通过对TLR的组织特异性表达和血吸虫感染后的动态表达变化的研究发现，湖北钉螺TLR可以迅速识别血吸虫的感染，并且在感染早期呈现高表达，同时可通过其下游分子开启TLR信号通路，这种下游分子的变化相对于TLR的动态变化，可维持更长时间。上述研究表明，湖北钉螺固有免疫中存在TLR及其信号通路，且在血吸虫感染早期发挥了免疫防御的作用；并确认了血淋巴细胞为湖北钉螺固有免疫中的主要效应细胞。该项目开启了湖北钉螺抗血吸虫感染的固有免疫的分子机制研究，对认识软体动物的天然免疫具重要意义；并有助于深入理解钉螺与血吸虫的相互关系，为最终控制血吸虫病提供科学依据。