泛在隐孢子虫宿主适应性遗传基础研究

Cryptosporidium ubiquitum can infect various animals and humans, which is one of the zoonotic Cryptosporidium species. That C. ubiquitum having extensive host-adaptation is one of the characterizations for zoonotic transmission, and studing the molecular genetic basis is an important measure to reveal the zoonotic transmission mechanism. Currently, C. ubiquitum has been detected from various animals in several areas in China; especially in sheep, it reached to 90.2% of ratio among the infected Cryptosporidium species. Thus, in the present study, based on the multilocus sequence typing C. ubiquitum isolates collected in this research group, and considered to the MLST subtypes and different geographical areas, two to three represent C. ubiquitum isolates will be selected and be sequenced the genome by 454 sequencing technique. Then, the obtained genome in this study and the available genome data deposited in CryptoDB will be aligned, by which, we can find the genetic genes associated with the host-adaptation for C. ubiquitum. The data should lay foundations for better studying the host-adaptation genetic mechanism and the invasion mechanism of C. ubiquitum.

泛在隐孢子虫（Cryptosporidium ubiquitum）可感染多种动物和人类，是人兽共患种类之一。该种广泛的宿主适应性是其人兽共患传播的生物学特征之一，研究宿主适应性分子遗传基础是揭示人兽共患传播机制的重要手段。目前，泛在隐孢子虫已发现于我国数个地区的多种动物；尤其是绵羊，该虫占感染虫种比例达90.2%。鉴于此，本项目拟在多位点序列分型（Multilocus sequence typing, MLST）课题组分离鉴定的泛在隐孢子虫分离株基础上，基于MLST亚型和地理区域选择2-3个代表性虫株使用454技术进行全基因组测序。通过对获得的泛在隐孢子虫基因组以及CryptoDB中已有的隐孢子虫基因组进行比对分析，寻找与宿主适应性相关的遗传基因位点。研究结果为深入研究泛在隐孢子虫宿主适应性遗传机制和侵入机制等奠定基础。

隐孢子虫感染280多种动物，导致生产性能下降或死亡，是人体第二大致腹泻病原，该病发生导致840万伤残调整生命年（DALYs）。泛在隐孢子虫可感染多种动物和人类，是重要的人兽共患种类之一。本项目在开展流行病学研究基础上，重点阐明泛在隐孢子虫亚型特征等分子遗传特征。. 首先开展了大量动物源隐孢子虫流行病学研究，采集河南和吉林地区鹿样品662份，河南和重庆山羊样品1265份，宁夏奶牛样品1580份、某隐孢子虫病暴发奶牛场252份，新疆牧马样品262份，隐孢子虫感染率分别为6.8%，4.81%，1.61%，21%，2.7%。基于18S rRNA基因的PCR-RFLP分析和DNA序列分析鉴定共获得羊源泛在隐孢子虫阳性分离株24个，鹿源泛在隐孢子虫阳性分离株3个。这些调查结果进一步验证了羊是我国泛在隐孢子虫重要的储藏宿主。. 筛选已报道的隐孢子虫微卫星、小卫星和SNP多态性位点15个对泛在隐孢子虫分离株进行MLST分型，仅gp60基因获得成功扩增，79个不同动物源泛在隐孢子虫分离株均属于人兽共患亚型XIIa subtype 2。结果提示泛在隐孢子虫和微小隐孢子虫以及人隐孢子虫存在较大的遗传差异性，反映了宿主适应性差异。结合课题组先前的研究结果，提示gp60基因很可能为隐孢子虫宿主适应性基因之一，需要进一步实验进行验证。本项研究结果为深入研究泛在隐孢子虫宿主适应性遗传机制和侵入机制等奠定了良好基础。