Great Ape Reservoirs of Human Malaria

描述（由申请人提供）：R 03申请的先前资助使我们能够开发允许从粪便DNA扩增疟原虫序列的新方法。通过对来自中非50多个野外地点的猿类样本进行筛查，我们发现恶性疟原虫起源于大猩猩，而不是黑猩猩、倭黑猩猩或古人类。我们还发现，黑猩猩和大猩猩体内至少有9种疟原虫，包括与间日疟原虫、卵形疟原虫和三日疟原虫几乎相同的寄生虫。鉴于这种疟原虫的数量巨大，而且大猩猩恶性疟原虫已经将该物种传播给人类一次，因此出现了一个问题，即是否正在发生猿类疟原虫寄生虫的额外交叉感染。这对公共卫生至关重要，不是因为预计这种传播会导致目前的疟疾发病率和死亡率，而是因为如果恶性疟原虫传播率降低，就会产生新的生态位，这将表明猿类疟原虫有可能在人类中定居。在本申请中，我们将研究野生猿类是否是人类疟疾的复发来源。我们将继续对野生猿类进行疟原虫感染的筛查，并对生活在这些猿类附近的人类进行测试，以寻找跨物种感染的证据。我们的假设是，猿类寄生虫具有感染人类的潜力，但由于恶性疟原虫的优势，未能建立持续感染。确定猿类疟原虫跨物种感染的类型、地点和频率对于衡量未来根除恶性疟原虫运动的成功与否至关重要。1.确定野生猿类中间日疟原虫和其他非Laverania种的流行率。我们将确定野生猿中非Laverania寄生虫的患病率，宿主特异性和分布，并确定黑猩猩和/或大猩猩是否代表西非中部人类间日疟原虫的宿主。2.确定野生黑猩猩或大猩猩是否是人类感染的复发源。我们将使用超深（454）测序来筛选与野生猿类生活在一起的人类，以寻找人畜共患疟原虫感染的证据。这种方法将识别Laverania和非Laverania寄生虫，即使它们以非常低的频率感染人类，并在多物种感染的背景下。3.确定猿类疟原虫感染的自然史。我们将前瞻性地跟踪疟原虫感染的避难所猿，以检查其临床状态，验证我们的非侵入性检测方法，并获得血液样本用于猿疟原虫分离和全基因组测序研究。4.确定区分人类恶性疟原虫与相关猿类物种的生物学特性。我们将表达猿疟原虫红细胞结合配体，并测试它们与人红细胞结合的能力，以研究疟原虫宿主特异性的分子基础，并评估哪些猿疟原虫物种有能力引起人类的血液期感染。

DESCRIPTION (provided by applicant): Previous funding by an R03 application allowed us to develop novel methods that permit the amplification of Plasmodium sequences from fecal DNA. Screening ape samples from over 50 field sites throughout central Africa, we found that P. falciparum is of gorilla origin, and not of chimpanzee, bonobo or ancient human origin. We also found that chimpanzees and gorillas harbor at least nine Plasmodium species, including parasites that are near identical to P. vivax, P. ovale and P. malariae. Given the magnitude of this Plasmodium reservoir and the fact that gorilla P. falciparum has crossed the species to humans already once, the question arises whether additional cross-infections of ape Plasmodium parasites are occurring. This is of critical public health importance, not because such transmissions would be expected to contribute to current malaria morbidity and mortality, but because they would give an indication of the potential of ape malaria parasites to colonize humans should a reduction of P. falciparum transmission rates generate a new ecological niche. In this application, we will examine whether wild apes serve as a recurrent source of human malaria. We will continue to screen wild ape populations for Plasmodium infections, and test humans who live in close proximity to these apes for evidence of cross-species infection. Our hypothesis is that ape parasites have the potential to infect humans but fail to establish persistent infections because of the predominance of P. falciparum. Determining the types, locations and frequencies of ape Plasmodium cross-species infections will be critical to gauge the success of future P. falciparum eradication campaigns. 1. To determine the prevalence of P. vivax and other non-Laverania species in wild apes. We will determine the prevalence, host specificities and distribution of non-Laverania parasites in wild apes, and determine whether chimpanzees and/or gorillas represent a reservoir for human P. vivax in west central Africa. 2. To determine whether wild chimpanzees or gorillas serve as recurrent sources of human infection. We will use ultradeep (454) sequencing to screen humans who live in close proximity to wild apes for evidence of zoonotic Plasmodium infections. This approach will identify Laverania and non-Laverania parasites even if they infect humans at very low frequencies and in the context of multispecies infections. 3. To determine the natural history of ape Plasmodium infections. We will prospectively follow Plasmodium infected sanctuary apes to examine their clinical status, validate our non-invasive detection methods, and obtain blood samples for ape Plasmodium isolation and whole genome sequencing studies. 4. To determine the biological properties that distinguish human P. falciparum from related ape species. We will express ape Plasmodium erythrocyte binding ligands and test their ability to bind to human erythrocytes in order to investigate the molecular basis of Plasmodium host specificity and to assess which ape Plasmodium species have the capacity to cause a blood stage infection in humans.