Great Ape Reservoirs of Human Malaria

描述(由申请人提供)：之前由R03申请提供的资金使我们能够开发新的方法，允许从粪便DNA中扩增疟原虫序列。通过对中非50多个野外地点的猿类样本进行筛选，我们发现恶性疟原虫起源于大猩猩，而不是黑猩猩、矮黑猩猩或古人类。我们还发现，黑猩猩和大猩猩至少有九种疟原虫，其中包括与间日疟原虫、卵形疟原虫和疟疾原虫几乎相同的寄生虫。考虑到这个疟原虫储存库的规模，以及大猩猩恶性疟原虫已经通过该物种传播给人类一次的事实，问题是，是否正在发生更多的猿类疟原虫交叉感染。这对公共卫生具有至关重要的意义，不是因为这种传播预计会导致目前的疟疾发病率和死亡率，而是因为它们将表明，如果恶性疟原虫传播率的降低产生新的生态位，猿类疟疾寄生虫可能会殖民人类。在这项应用中，我们将研究野生类人猿是否作为人类疟疾的经常性来源。我们将继续对野生类人猿种群进行疟原虫感染的筛查，并对与这些类人猿密切接触的人类进行测试，以寻找跨物种感染的证据。我们的假设是，猿类寄生虫有可能感染人类，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、位置和频率将是衡量未来根除恶性疟原虫运动成功与否的关键。1.确定间日疟原虫和其他非间日疟原虫在野生类人猿中的流行情况。我们将确定野生类人猿中非拉维拉虫寄生虫的流行率、宿主特异性和分布，并确定黑猩猩和/或大猩猩是否为中非西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为人类反复感染源。我们将使用超深(454)测序来筛选生活在野生类人猿附近的人类，以寻找人畜共患疟原虫感染的证据。这种方法将识别拉维拉尼亚寄生虫和非拉维拉尼亚寄生虫，即使它们感染人类的频率很低，并在多物种感染的背景下也是如此。3.确定猿类疟原虫感染的自然历史。我们将前瞻性地跟踪感染疟原虫的避难所猿类，检查它们的临床状态，验证我们的非侵入性检测方法，并获取血样用于猿类疟原虫分离和全基因组测序研究。4.确定人恶性疟原虫与近缘类人猿的生物学特性。我们将表达人疟原虫红细胞结合配体，并检测其与人红细胞结合的能力，以探讨疟原虫宿主特异性的分子基础，并评估哪些人疟原虫物种具有引起人类血液期感染的能力。

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.