Duffy antigen presentation and its correlation to parasite invasion

描述(由申请人提供)：据估计，全世界有32亿人面临疟疾的风险，而疫苗开发工作尚未取得成功。间日疟原虫和诺氏疟原虫共造成7000万至8000万人感染疟疾，是有效疟疾疫苗的关键目标物种。此外，间日疟原虫感染会导致以前没有接触过这种寄生虫的患者出现虚弱症状。驻扎在阿富汗和伊拉克等间日疟流行地区的美国武装部队对这种疾病的这一特征特别感兴趣。密切相关的诺氏疟原虫是一种新出现的病原体，占东南亚一些地区所有疟疾感染的20%。据观察，只有在红细胞表面表达达菲血型抗原的人才会感染血液期诺氏疟原虫或间日疟原虫。目前的几种疫苗策略集中在阻断Duffy抗原和寄生虫Duffy结合蛋白(DBP)的相互作用上。虽然这一策略很有希望，但人们对Duffy受体的表达以及这种疫苗策略是否有效知之甚少。以前的研究表明，Duffy抗原的表达可能在Duffy阳性人群中有所不同。在这个建议中，我们将解决以下问题：a)Duffy阳性个体的表型(Fya+/Fya+，Fya+/Fyb+，Fyb+，Fyb+)在Duffy受体的分布或与DBP的结合亲和力方面是否存在差异，b)供体性别是否影响DBP的结合，c)红细胞表面拓扑是否影响DBP结合，以及d)更大的DBP结合亲和力是否会导致寄生虫感染水平的增加？为了解决这些问题，我们将鉴定红细胞表面Duffy受体的表达水平和位置，确定重组DBP变异体的结合亲和力，并使用高通量流式细胞术测量寄生虫的侵袭效率。我们将在三个样本分组中研究这些参数：表达Fya、Fyb或Fya/Fyb Duffy受体的男性，Fya或Fyb纯合子阳性的男性和女性，以确定供者的性别是否影响Duffy受体的分布，以及：来自血红蛋白或红细胞表面蛋白变异的患者的样本。我们相信，这些研究将产生有关寄生虫入侵的重要信息，这些信息将指导疫苗的开发和实施。相关性(见说明)：这项研究的相关性在于，它有助于了解疟疾寄生虫是如何入侵红细胞的，以及人类是如何改变以避免这种感染的。基于这些知识，我们可以设计出一种针对5种疟疾中的2种的有效疫苗。我们设计的疫苗将于2011年开始在巴布亚新几内亚进行测试。

DESCRIPTION (provided by applicant): An estimated 3.2 billion people in the world are at risk for malaria while vaccine development efforts have yet to be successful. The malaria species Plasmodium vivax and Plasmodium knowlesi together account for 70-80 million human malaria infections and represent the key target species for an effective malaria vaccine. Additionally, P. vivax infection causes debilitating symptoms in patients who have previously been unexposed to the parasite. This characteristic of the disease is of particular interest to the U.S. Armed Forces who are stationed in P. vivax endemic areas such as Afghanistan and Iraq. The closely related species P. knowlesi, a newly emerging pathogen, accounts for up to 20% of all malaria infections in some regions of Southeast Asia. It has been observed that only people that express the Duffy blood group antigen on the surface of their erythrocytes become infected with blood-stage P. knowlesi or P. vivax. Several current vaccine strategies are focused on interruption of the interaction of the Duffy antigen and the parasite Duffy binding protein (DBP). While this strategy is promising, little is known about the expression of the Duffy receptor and whether such a vaccine strategy would be effective. Previous studies have suggested that Duffy antigen expression may vary across Duffy positive populations. In this proposal we will address the following questions: a) do phenotypes of Duffy positive individuals (Fya+/Fya+, Fya+/Fyb+, and Fyb+,Fyb+) differ in the distribution of Duffy receptors or binding affinity to DBP, b) does the sex of the donor influence the binding of DBP, c) does erythrocyte surface topology influence DBP binding, and d) does greater DBP binding affinity lead to increased levels of parasite infections? To address these questions we will identify the level and location of Duffy receptor expression on the surface of erythrocytes, determine binding affinity of recombinant DBP variants, and measure parasite invasion efficiency using high throughput flow cytometry. We will study these parameters across three sample groupings; males expressing Fya, Fyb, or Fya/Fyb Duffy receptors, males and females homozygous positive for Fya or Fyb to identify if the sex of the donor effects Duffy receptor distribution, and: samples from patients with hemoglobin or erythrocyte surface proteins variants. We believe that these studies will yield important information about parasites invasion which will guide vaccine development and implementation. RELEVANCE (See instructions): The relevance of this study is that it helps understand how malaria parasites invade red blood cells and how humans have changed to avoid this infection. Based on this knowledge we can design an effective vaccine against 2 of the 5 types of malaria. The vaccine we design will be tested in Papua New Guinea starting in 2011.