Great Ape Reservoirs of Human Malaria

 描述(由申请人提供)： 在已知的感染人类的五种疟原虫中，恶性疟原虫和间日疟原虫是世界上导致疟疾病例最多的两种，因此构成了最大的公共卫生挑战。通过全面的实地研究，我们发现这两种人类病原体都起源于非洲猿类(1-7)。我们发现，黑猩猩和大猩猩至少有六种与恶性疟原虫(包括间日疟原虫亚属)关系密切的疟原虫，以及与人类间日疟原虫(1-7)几乎相同的寄生虫。对类人猿衍生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交换后进化的(1，6)，而间日疟原虫则是从同时感染黑猩猩和大猩猩的一种疟原虫物种内进化而来的(3)。尽管人类病原体的起源现在已经确定，但人们对导致它们出现的进化和机制过程一无所知；然而，这些信息对于理解类人猿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。在这个重新提交的申请中，我们建议通过在整个基因组水平上表征人类寄生虫的猿类前体，并通过确定传播这些猿类寄生虫的按蚊媒介的种类和宿主偏好来解决这些问题。我们的假设是，对猿类疟原虫的比较基因组和种群基因组研究，加上对它们传播蚊子媒介的分析，将对恶性疟原虫和间日疟原虫的生物学产生新的见解，并揭示允许猿类寄生虫在人类上定居的过程。一个主要的障碍是，由于宿主的濒危物种地位，几乎不可能获得猿类疟原虫样本。在过去的赠款期间，我们通过开发选择性全基因组扩增(SWGA)技术解决了这个问题，该技术从未经处理的猿血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。利用这一新技术，我们已经对几个接近全长的猿类疟原虫基因组进行了测序，揭示了恶性疟原虫前体(RH5位点)和一个新的网织红细胞结合蛋白基因(RBP-3)在间日疟原虫中的水平转移。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(目标1)以及黑猩猩和大猩猩间日疟原虫(目标2)的每一个额外成员的基因组进行排序。比较基因组分析将确定类人猿和人类疟原虫物种所特有的基因座，以及经过正向选择的基因。这些遗传学研究将得到传播猿类疟原虫寄生虫的按蚊媒介的现场和实验室研究(目标3)以及宿主-寄生虫相互作用的假说驱动的机制研究(目标4)的补充。执行这些目标将极大地促进我们对导致恶性疟原虫和间日疟原虫出现的途径的了解，并为未来的人畜共患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.