Great Ape Reservoirs of Human Malaria

 描述（由申请人提供）： 在已知感染人类的五种疟原虫中，恶性疟原虫和间日疟原虫在全世界引起的疟疾病例最多，因此构成了最大的公共卫生挑战。进行全面的实地研究，我们发现这两种人类病原体都起源于非洲猿（1-7）。我们发现，黑猩猩和大猩猩体内至少有6种与恶性疟原虫（包括Laverania亚属）密切相关的疟原虫，以及与人类间日疟原虫几乎相同的寄生虫（1-7）。猿源序列的系统发育分析表明，恶性疟原虫是在大猩猩寄生虫的单一宿主转换后进化的（1，6），而间日疟原虫则是从感染黑猩猩和大猩猩的疟原虫物种中出现的（3）。虽然人类病原体的起源现在已经得到了很好的确定，但对导致它们出现的进化和机械过程一无所知;然而，这些信息对于了解猿类寄生虫如何跨越物种障碍以及此类事件是否可能再次发生至关重要。在此重新提交申请，我们建议解决这些问题，通过在全基因组水平上表征人类寄生虫的猿前体，并确定传播这些猿寄生虫的按蚊载体的物种和宿主偏好。我们的假设是，对猿类疟原虫寄生虫的比较和种群基因组研究，加上对其传播蚊子载体的分析，将对恶性疟原虫和间日疟原虫的生物学产生新的见解，并揭示猿类寄生虫在人类身上定居的过程。一个主要的障碍是，由于其宿主的濒危物种地位，猿类疟原虫样本几乎不可能获得。在过去的资助期间，我们通过开发一种选择性全基因组扩增（SWGA）技术解决了这个问题，该技术可以从未经处理的猿血液和粪便样本以及受感染的蚊子中产生足够数量的寄生虫基因组用于下一代测序。利用这种新技术，我们已经测序了几个接近全长的猿疟原虫基因组，这揭示了一个水平的基因转移的前体恶性疟原虫（RH 5位点）和一个新的网织红细胞结合蛋白基因（RBP-3）在猿间日疟原虫。我们将使用粪便和血液样本以及受感染的蚊子对六种类人猿Laverania物种（Aim #1）以及黑猩猩和大猩猩间日疟原虫寄生虫（Aim #2）的其他成员的基因组进行测序。比较基因组分析将确定基因座是独特的猿与人类疟原虫物种以及基因已受到积极的选择。这些遗传学研究将得到传播猿疟原虫寄生虫的按蚊媒介的实地和实验室研究（目标3）以及宿主-寄生虫相互作用的假设驱动机制研究（目标4）的补充。这些目标的实现将大大推进我们对导致恶性疟原虫和间日疟原虫出现的途径的理解，并为未来人畜共患病风险的根除工作提供信息。

 DESCRIPTION (provided by applicant): Of the five Plasmodium species known to infect humans, P. falciparum and P. vivax cause the most malaria cases worldwide, and thus pose the greatest public health challenge. Conducting comprehensive field studies, we discovered that both of these human pathogens have their origins in African apes (1-7). We found that chimpanzees and gorillas harbor at least six Plasmodium species that are closely related to P. falciparum (comprising the Laverania subgenus) as well as parasites that are nearly identical to human P. vivax (1-7). Phylogenetic analysis of ape-derived sequences showed that P. falciparum evolved following a single host switch of a gorilla parasite (1, 6), while P. vivax emerged from within a Plasmodium species that infects both chimpanzees and gorillas (3). Although the origins of the human pathogens are now well established, nothing is known about the evolutionary and mechanistic processes that led to their emergence; yet, such information is critical to understand how ape parasites crossed the species barrier and whether such events are likely to occur again. In this resubmission application, we propose to address these questions by characterizing the ape precursors of the human parasites at the whole genome level and by determining the species and host preferences of the Anopheles vectors that transmit these ape parasites. Our hypothesis is that comparative and population genomic studies of ape Plasmodium parasites, coupled with analyses of their transmitting mosquito vectors, will yield new insight into the biology of P. falciparum and P. vivax and reveal the processes that allowed ape parasites to colonize humans. One major obstacle has been that ape Plasmodium samples are virtually impossible to obtain due to the endangered species status of their hosts. In the past grant period, we have solved this problem by developing a selective whole genome amplification (SWGA) technique that generates -- from unprocessed ape blood and fecal samples as well as infected mosquitoes -- sufficient numbers of parasite genomes for nextgen sequencing. Using this novel technology, we have already sequenced several near full-length ape Plasmodium genomes, which revealed a horizontal gene transfer in the precursor of P. falciparum (RH5 locus) and a new reticulocyte binding protein gene (RBP-3) in ape P. vivax. We will use fecal and blood samples and infected mosquitoes to sequence the genomes of additional members of each of the six ape Laverania species (Aim #1) as well as chimpanzee and gorilla P. vivax parasites (Aim #2). Comparative genomic analyses will identify loci that are unique to ape versus human Plasmodium species as well as genes that have been subject to positive selection. These genetic studies will be complemented by field and laboratory studies of the Anopheles vectors that transmit ape Plasmodium parasites (Aim #3), as well as hypothesis driven mechanistic studies of host-parasite interactions (Aim #4). Execution of these aims will substantially advance our understanding of the pathways that led to the emergence of P. falciparum and P. vivax, and inform eradication efforts of future zoonotic risk.