Whole genome sequencing of Malagasy Duffy-independent P. vivax

描述（由申请人提供）：今天有26亿人生活在间日疟原虫传播风险地区；每年有1.06 - 3.13亿间日疟疾病例。虽然达菲阴性血型被认为赋予了间日疟疾的抗性，但我们最近的研究结果表明，间日疟原虫已经获得了感染红细胞并在马达加斯加的达菲阴性（Duffy(-)）人群中引起疾病的能力，这表明间日疟原虫已经获得了新的红细胞感染机制。在对学龄儿童的调查中，8.8%的无症状Duffy（-）儿童（42/476）为间日疟原虫pcr阳性。此外，在评估马达加斯加卫生部推荐用于治疗疟疾疾病的药物的体内疗效的调查中，我们确定了9名Duffy（-）人患有单感染间日疟原虫疟疾（183名参与者中的4.9%）。我们通过显微镜验证了这一不寻常的发现，为间日疟原虫的血液阶段发育提供了第一个证据，包括通过蚊子传播继续寄生虫生命周期所必需的性阶段配子体。最后，对来自马达加斯加研究参与者（n=43，其中许多人经历过临床间日疟原虫疟疾）的红细胞进行流式细胞分析显示，Duffy（-）基因型和表型100%一致，表明在基因典型Duffy（-）个体中，Duffy抗原没有在红细胞表面隐式表达。为了开始理解间日疟原虫是如何获得感染Duffy（-）红细胞的能力，我们建议分析从Duffy（+）和Duffy（-）马达加斯加人的血液样本中提取的几种间日疟原虫分离株的基因组序列，所得数据将使我们能够解决以下具体目标。目的1：确定同一株间日疟原虫是否导致了马达加斯加Duffy（-）和Duffy（+）个体的感染，并重建马达加斯加间日疟原虫的种群历史。目的2：鉴定马达加斯加间日疟原虫基因组近期阳性选择下的基因。我们通过全基因组测序对多个马达加斯加间日疟原虫分离株的遗传多样性进行了研究，这将使我们能够确定寄生虫种群是如何分裂的，或者是否分裂了，以响应Duffy阴性反应所施加的重要障碍。通过鉴定最近阳性选择下的位点，我们的研究具有很强的潜力来鉴定新的寄生虫入侵配体，这些配体有助于达菲非依赖性红细胞入侵。

DESCRIPTION (provided by applicant): Today 2.6 billion people live in areas of risk for Plasmodium vivax transmission; 106 - 313 million cases of vivax malaria annually. While Duffy blood group negativity has been considered to confer resistance to vivax malaria, our recent findings indicate that P. vivax has gained the capacity to infect erythrocytes and cause disease in Duffy-negative (Duffy(-)) people in Madagascar and suggests that P. vivax has acquire new erythrocyte infection mechanisms. In surveys of school-aged children 8.8% of asymptomatic Duffy(-) children (42/476) were P. vivax PCR-positive. Additionally, during surveys to assess in vivo efficacy of drugs recommended by the Madagascar Ministry of Health to treat malarial illness, we identified nine Duffy(-) people who had mono-infection P. vivax malaria (4.9% of 183 participants). We validated this unusual finding by microscopy to provide the first evidence for blood- stage development of P. vivax, including sexual-stage gametocytes necessary to continue the parasite lifecycle through mosquito transmission. Finally, flow cytometric analysis of erythrocytes from Malagasy study participants (n=43; many of whom experienced clinical P. vivax malaria) showed that Duffy(-) genotype and phenotype were 100% concordant, to indicate that the Duffy antigen was not cryptically expressed on the erythrocyte surface in genotypically Duffy(-) individuals. To begin understanding how P. vivax has gained capacity to infect Duffy(-) erythrocytes we propose to analyze the genome sequence of several P. vivax isolates extracted from blood samples of Duffy(+) and Duffy(-) Malagasy individuals, and the resulting data will allow us to address the following Specific Aims. Aim 1: Determine whether the same strains of P. vivax are responsible for infections of Duffy(-) and Duffy(+) individuals in Madagascar and reconstruct the population history of Malagasy P. vivax. Aim 2: Identify genes under recent positive selection in Malagasy P. vivax genomes. Our study of genetic diversity among multiple Malagasy P. vivax isolates by whole genome sequencing will allow us to determine how, or if the parasite population has partitioned in response to the important barrier imposed by Duffy negativity. By identifying loci under recent positive selection, our studies have strong potential to identify new parasite invasion ligands contributing to Duffy-independent erythrocyte invasion. PUBLIC HEALTH RELEVANCE:- Today 2.6 billion people live in areas of risk for Plasmodium vivax (Pv) transmission; 106 - 313 million cases of vivax malaria annually. Duffy blood group negativity has been considered to confer resistance to vivax malaria, however, our recent findings indicate that Pv has gained the capacity to infect erythrocytes and cause disease in Duffy-negative people in Madagascar, suggests that Pv has acquire new erythrocyte infection mechanisms. Through whole genome sequence analysis we will reveal differences between Pv strains infecting Duffy-negative vs. Duffy-positive people that will help identify genes evolving to expand the erythrocyte invasion capacity of Pv.