细粒棘球蚴（Eg）感染所致的囊型包虫病（CE）是中国西部地区危害严重的一种人畜共患寄生虫病。Eg需要清除自身代谢和拮抗宿主免疫细胞产生的双重氧化损伤才能在宿主体内稳定寄生。针对Eg抗氧化应激系统的研究较少，研究表明硫氧还蛋白过氧化物酶(TPx)是其抵抗氧化损伤（分解过氧化氢H2O2）的关键抗氧化酶，可能对其在宿主体内的正常生长和存活十分必要。本研究拟利用毕赤酵母真核表达系统表达EgTPx蛋白，通过还原H2O2活性及保护超螺旋DNA等实验鉴定其生物学功能；使用不同浓度H2O2处理体外培养的原头蚴（PSC），通过观察PSC活性状态和EgTPx表达，确定PSC耐受H2O2的浓度及EgTPx对高氧环境的保护作用；利用RNAi 技术，通过体外（Eg体外培养体系）、体内（Eg感染小鼠模型）两方面相结合阐明EgTPx基因对细粒棘球蚴生长、存活及致病性的影响，为包虫病药物的筛选和研发提供思路和理论依据。

Cystic echinococcosis (CE) is a cosmopolitan zoonosis caused by the larval stage of the cestode Echinococcus granulosus (Eg), which is hyper-endemic in western China. Given the parasite lives in an aerobic organism which produces a large amount of reactive oxygen species (ROS) around and larval cyst can be in host for up to 46 years, the parasite must produce antioxidants against ROS for survival. However, there are very limited studies on Eg anti-oxidative stress. We identified that about 40% of sera from CE patients had specific antibodies against Eg thioredoxin peroxidase (EgTPx), suggesting the enzyme is secreted or located in the outside of the parasite. I have cloned EgTPx and showed that the enzyme has high function to convert H2O2into H2O and O2. Given the parasite has very low activities of glutathione peroxidase (GPx) and catalase, TPx must play an important role in anti-oxidant system and in turn, play an important role for parasite survival and likely is the target for drug and vaccine development. In the present study, we aim (1) to explore the functional characterisation of EgTPx using H2O2tolerance bioassay and metal-catalyzed oxidation assay; (2) to identify the tolerance limit of protoscoleces (PSC) against H2O2 (3) to interpret the relationship of TPx and growth and survival of the parasite using an in vitro model and (4) to silence the EgTPx gene using RNAi to identify the role of this gene in parasite against H2O2.