Molecular analysis of intraerythrocytic parasite population dinamics and acquirement of biological diversity

在牛侵染东方滴虫的过程中，携带不同主要螺质表面蛋白（MPSP）基因的寄生虫种群轮流出现，这可能是该寄生虫的免疫逃避机制之一。因此，对寄生虫种群的分析对了解其发病机制和制定防治方法具有重要意义。本研究建立了退化凝胶电泳方法，在遗传水平上分析寄生虫亚群。利用该方法可以检测c型等位基因MPSP基因的突变。对可能感染不同伊氏菌的牛、水牛血样进行了rRNA基因靶向PCR分析，发现有4种不同的伊氏菌混合感染。进行了小孢子虫表达序列标记分析和EST在染色体上的定位，共定位了461条EST。我们进一步关注蜱、哺乳动物和伊氏杆菌相互作用的蜱唾液和唾液腺。几种蛋白质及其基因，包括水泥蛋白，蛋白酶抑制剂已被表征。可能，这些蜱虫蛋白中的一些会影响宿主的保护反应，并帮助寄生虫入侵哺乳动物宿主。

During the course of Theileria orientalis infection in cattle, parasite population bearing different major piroplasm surface protein (MPSP) genes appear by turns, which may be one of immune evasion mechanisms of the parasite. Therefore, analysis of parasite population is important in understanding pathogenesis and developing control methods.In this study, degenerated gel electrophoresis methods for the analysis of parasite subpopulations at genetic level has been developed. By using this method, mutations within MPSP gene of C-type allele could be detected. From blood samples from cattle and buffalo, which were possibly infected with different Theileria, species was analyzed by rRNA gene-targeted PCR analysis and revealed mixed infection with 4 different species. The expressed sequence tag analysis of T. parva and EST mapping on chromosomes was carried out and 461 ESTs have been mapped.We further focused on tick saliva and salivary glands where tick, mammals and Theileria interact. Several proteins and their genes including cement proteins, proteinase inhibitors have been characterized. Probably, some of these tick proteins affect host protective responses and help parasite to invade into mammalian hosts.