活性氧在长角血蜱肠道共生菌抑制田鼠巴贝虫传播中的机制研究

Gut microbiota affect the transmission capacity of arthropod vectors to various pathogens. Improving reactive oxygen species (ROS) is an important molecular mechanism for gut microbiota to control pathogenic infection in vector hosts. In previous studies, we have found that disturbance of gut microbiota by antibiotic treatment increased the susceptibility of Haemaphysalis longicornis ticks to Babesia microti. However, the potential molecular mechanisms have not been studied yet.. Based on the results of transcriptome sequencing, we have conducted a pilot study and found that antibiotic treatment could down-regulate the expression of ROS-related genes in the gut of engorged H. longicornis nymphs after feeding on mice infected with B. microti. Therefore, we hypothesize that gut microbiota induce ROS to control B. microti infection in H. longicornis ticks. In the present study, we will conduct antibiotic treatment experiments to screen differentially expressed ROS and immune-related genes. After that, we will use RNA inference to test the function of the target genes on regulating ROS level and vector capability of B. microti. Through these methods, we will illuminate the molecular mechanisms that gut microbiota up-regulate ROS level in H. longicornis ticks, that ROS inhibit transmission capacity of B. microti by ticks, and that gut microbiome induce ROS to protect ticks against B. microti infection. Our study will provide theoretical foundations for applying gut microbiota-based strategies in the control of tick-borne diseases.

肠道共生菌影响媒介节肢动物传播病原体的效能，提高活性氧是肠道共生菌介导媒介宿主抗病原体感染的重要分子机制。申请人既往研究发现，抗生素处理干扰肠道共生菌增加长角血蜱对田鼠巴贝虫的传播效能，但分子机制尚不明确。. 本研究在前期转录组测序基础上，结合链霉素处理可下调长角血蜱肠道活性氧相关基因表达量的预实验结果，提出肠道共生菌通过调节活性氧影响长角血蜱传播田鼠巴贝虫的效能的研究假说。申请人拟开展蜱媒抗生素处理实验，筛选肠道中差异表达的活性氧及免疫相关基因，并通过RNA干扰验证靶基因在调节活性氧水平和影响蜱媒对田鼠巴贝虫的传播效能等方面的作用，从分子层面阐明肠道共生菌如何调节长角血蜱活性氧含量、活性氧水平如何影响长角血蜱传播田鼠巴贝虫的效能、活性氧是否在蜱媒肠道共生菌抗田鼠巴贝虫感染中发挥中介作用等科学问题，进而验证假说，为将基于肠道共生菌的生物防制技术应用于蜱传疾病防控提供理论依据。

媒介节肢动物肠道共生菌在调控媒介宿主免疫、抵御病原体感染方面发挥重要作用，调节媒介节肢动物活性氧是共生菌介导媒介宿主抗病原体感染作用的重要分子机制。但蜱媒共生菌是否能通过调控蜱媒氧化还原稳态影响蜱媒对田鼠巴贝虫的传播有待研究。本项目通过开展蜱媒抗生素处理实验，筛选共生菌受干扰所致的氧化还原相关差异表达基因，并通过RNA干扰验证靶基因在调节活性氧水平和影响蜱媒对田鼠巴贝虫的传播效能等方面的作用，旨在探讨共生菌对蜱媒氧化应激的调控作用、活性氧对蜱媒田鼠巴贝虫传播效能的影响及共生菌是否通过调控氧化还原稳态影响蜱媒对田鼠巴贝虫的传播等问题；同时，对影响长角血蜱分布概率的自然因素及自然界中动物宿主和媒介中巴贝虫感染率进行了分析。研究结果表明：抗生素处理干扰蜱媒共生菌影响氧化还原相关基因表达水平，并影响长角血蜱对外源性活性氧刺激的存活率，说明蜱媒共生菌参与长角血蜱的氧化应激反应；RNA干扰实验表明，Nox基因表达下调影响蜱媒若蜱-成蜱阶段经期传播田鼠巴贝虫，说明蜱媒体内的氧化还原稳态可影响田鼠巴贝虫在蜱媒体内的发育繁殖；同时，共生菌不影响蜱媒对田鼠巴贝虫的获取过程，但可调控田鼠巴贝虫在若蜱体内的消长，而此调控过程可到受外源性还原剂的影响，说明共生菌可能通过调节氧化还原平衡影响蜱媒对田鼠巴贝虫的传播效能；温度、降水、海拔等因素对长角血蜱在自然界中的分布概率有较大影响，除硬蜱属蜱种外，长角血蜱、嗜群血蜱、网纹革蜱、血红扇头蜱、图兰扇头蜱等均可作为田鼠巴贝虫的传播媒介。