Madagascar P. vivax Invasion of Duffy-negative Red Cells

描述（由申请人提供）：今天，至少有26亿人生活在间日疟原虫传播的风险地区;每年有1.06 - 3.13亿例间日疟原虫疟疾病例。虽然Duffy血型阴性（Duffy（-））被认为赋予了对间日疟的抵抗力，但我们最近的研究结果表明，间日疟已经获得了感染马达加斯加Duffy（-）人红细胞并导致疾病的能力。我们对学龄儿童的调查显示，在8.8%的无症状Duffy（-）儿童中，间日疟原虫PCR阳性。我们还在体内药物疗效调查期间报告接受治疗的Duffy（-）人群中观察到4.9%的单一感染间日疟原虫临床疾病;血涂片诊断证实了间日疟原虫。有趣的是，使用6个非连锁微卫星标记进行的初步人群研究表明，Duffy（-）感染是由多种间日疟原虫菌株引起的。虽然我们的研究结果表明，间日疟原虫在马达加斯加的入侵可以独立于红细胞的达菲血型抗原发生，但我们不知道入侵是否依赖于或独立于寄生虫的“所谓的”达菲结合蛋白（PvDBP），寄生虫配体被认为是入侵人类红细胞所必需的。通过对PvDBP基因座进行DNA测序，我们已经确定了一个等位基因在达菲（-）感染中过度表达。此外，最近的全基因组测序显示，马达加斯加间日疟原虫菌株（马达加斯加以外没有间日疟原虫菌株）携带PvDBP重复。总的来说，我们的研究结果表明，马达加斯加的间日疟原虫正在发展新的红细胞感染机制。为了开始了解间日疟原虫如何获得感染达菲（-）红细胞的能力，我们建议研究寄生虫种群的种群遗传特征，同时对马达加斯加的间日疟原虫菌株进行深入的细胞和分子生物学分析。从这些研究中得到的数据将使我们能够解决以下具体目标。目的1 -确定间日疟原虫菌株与达菲（-）人对间日疟原虫血液期感染和临床疟疾的易感性之间的关联。目的2 -评估间日疟原虫红细胞结合配体与人红细胞之间影响裂殖子附着和人红细胞侵入的相互作用。目的3 -测试马达加斯加间日疟原虫菌株在体外对达菲（-）和达菲（+）红细胞的替代侵入途径。我们的研究将确定达菲（+）和达菲（-）人对间日疟原虫病的不同易感性。Planne体外研究将提供关于新的间日疟原虫红细胞侵袭机制的见解，特别强调Duffy非依赖性侵袭。最后，我们将确定间日疟原虫与达菲（+）和达菲（-）红细胞的结合和侵入所涉及的分子变异是否表明马达加斯加间日疟原虫菌株传播到其他种群的能力。

DESCRIPTION (provided by applicant): Today at least 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 (Duffy (-)) has been considered to confer resistance to vivax malaria, our recent findings show that P. vivax has gained the capacity to infect erythrocytes and cause disease in Duffy (-) people in Madagascar. Our surveys of school-aged children revealed P. vivax PCR-positivity in 8.8% of asymptomatic Duffy (-) children. We also observed mono-infection P. vivax clinical disease in 4.9% of Duffy (-) people who reported for treatment during in vivo drug efficacy surveys; blood smear diagnosis confirmed P. vivax. Interestingly, preliminary population studies using 6 unlinked microsatellite markers suggested that Duffy (-) infections were caused by multiple P. vivax strains. While our results indicate that P. vivax invasion in Madagascar can occur independent of the erythrocyte's Duffy blood group antigen, we do not know if invasion is dependent or independent of the parasite's 'so-called' Duffy binding protein (PvDBP), the parasite ligand considered essential for invasion of human red blood cells. By DNA sequencing the PvDBP locus we have identified one allele to be over-represented in Duffy (-) infections. Additionally, recent whole genome sequencing has revealed that Malagasy P. vivax strains (and no P. vivax strains outside Madagascar) carry a PvDBP duplication. Overall, our findings suggest that P. vivax in Madagascar is evolving new erythrocyte infection mechanisms. To begin understanding how P. vivax has gained capacity to infect Duffy(-) erythrocytes we propose to study population genetic features of the parasite population while performing in-depth cell and molecular biological analysis of P. vivax strains of Madagascar. Resulting data from these studies will allow us to address the following Specific Aims. Aim 1 - Determine associations between P. vivax strains and susceptibility of Duffy (-) people to P. vivax blood-stage infection and clinical malaria. Aim 2 - Assess interactions between P. vivax erythrocyte binding ligands and human erythrocytes that influence merozoite attachment and human red cell invasion. Aim 3 - Test alternative invasion pathways of Malagasy P. vivax strains in vitro for Duffy (-) and Duffy (+) erythrocytes. Our studies will determine differential susceptibility of Duffy (+) and Duffy (-) people to P. vivax disease. Planne in vitro studies will provide insight regarding new P. vivax erythrocyte invasion mechanisms, with special emphasis on Duffy-independent invasion. Finally, we will determine whether molecular variations involved in P. vivax binding to, and invasion of Duffy (+) and Duffy (-) erythrocytes indicates capacity of Madagascar P. vivax strains to spread into other populations.