Strain-specific Immunity to Plasmodium vivax malaria

描述(由申请人提供)： 间日疟因其广泛的全球分布、耐药菌株的日益流行以及最重要的是感染间日疟会导致严重的临床症状而造成疟疾发病率的巨大负担。间日疟原虫占非洲感染的12.4%，占亚洲和美洲感染的70%-90%。现在报告的PV病例比现役或返回士兵的任何其他疟疾物种都要多。由于对光伏的耐药性增加、致死性病例和光伏的再利用行为，开发光伏疫苗是军事传染病研究计划的主要优先事项。间日疟原虫Duffy结合蛋白II区(PvDBPII)是目前领先的PV候选疫苗之一。这种蛋白在寄生虫的细胞表面表达，并与宿主红细胞的Duffy抗原(FY)结合，促进红细胞的入侵。其他人类疟疾，如恶性疟原虫，有几个不同的Duffy结合蛋白样基因，有助于使用替代受体来进行裂殖子入侵，然而PvDBPII和Duffy抗原对PV入侵红细胞的几乎排他性依赖是一个关键弱点，使PV DBP配体成为疫苗开发的理想靶标。将PvDBPII用作疫苗仍然存在重大挑战，包括其高度多态、免疫原性较弱以及缺乏对产生最强阻断或保护反应的特定分子部分的了解。这项建议建立在我们当前项目的观察结果基础上。首先，我们已经确定了流行区中获得上述高滴度功能性抗体的一部分人，这些抗体可以阻断与多种PvDBPII变体的结合。将功能性人类抗体映射到PvDBPII的特定区域可能有助于识别跨毒株的疫苗。其次，在不同动物中产生的阻断PvDBPII与FY结合的多克隆和单克隆抗体优先识别PvDBPII的一个相对保守的亚域，这可能有助于疫苗的开发。第三，我们已经证明了Fy(Fyb？Fya，Asp42Gly)的主要多态与PvDBPII的结合减少和人类临床PV风险的降低有关。我们发现，与Fyb红细胞相比，针对PvDBPII的自然获得性和人工诱导的抗体都能更有效地阻断其与Fya的结合，表明宿主Fy基因可能是重要的疫苗效力。目的1.鉴定PvDBPII上跨株中和抗体识别的表位。目的2.建立PvDBPII跨株阻断/侵袭抑制抗体的疫苗制备方法。目的3.比较Duffy Fya和Fyb表型在体外和体内PvDBPII功能免疫应答中的作用。

DESCRIPTION (provided by applicant): Plasmodium vivax malaria contributes to a large burden of malaria morbidity owing to its widespread global distribution, the increasing prevalence of drug-resistant strains and most importantly, infections with Pv cause severe clinical syndromes. Plasmodium vivax accounts for 12.4% of infections acquired in Africa and 70-90% of infections acquired in Asia and the Americas. More cases of Pv are now reported than any other malaria species for active duty or returning soldiers. Because of increasing drug resistance to Pv, lethal cases and replapsing behavior of Pv, development of Pv vaccine is a major priority of the Military Infectious Disease Research Program. One the leading Pv vaccine candidates is P. vivax Duffy binding protein region II (PvDBPII). This protein is expressed at the parasite's cellular surface and binds the host red cell's Duffy antigen (Fy) that facilitates erythrocyte invasion. Other human malaria such as P. falciparum, have several different Duffy Binding Protein-like genes that facilitate the use o alternative receptors for merozoite invasion, however the almost exclusive dependence of PvDBPII and Duffy antigen for Pv invasion of erythrocytes a critical weakness and makes the Pv DBP ligand an ideal target for vaccine development. Substantial challenges remain for use PvDBPII as a vaccine, including its high degree of polymorphism, its weak immunogenicity and a lack of understanding as regards to the specific portion of the molecule engendering the strongest blocking or protective responses. This proposal builds on observations from our current project. First, we have identified a subset of individuals in endemic areas who acquire high titers of functional antibodies described above that block binding to multiple PvDBPII variants. Mapping of the functional human Abs to specific regions of PvDBPII may help to identify a strain-transcending vaccine. Second, polyclonal and monoclonal antibodies generated in different animals that block binding of PvDBPII to Fy preferentially recognize a relatively conserved sub-domain of PvDBPII that could facilitate development of a vaccine. Third, we have shown that the major polymorphism in Fy (Fyb¿Fya, Asp42Gly) is associated with both diminished binding of PvDBPII and a reduced risk of clinical Pv in humans. We found that both naturally acquired and artificially induced Abs directed to PvDBPII more effectively blocked its binding to Fya as compared to Fyb erythrocytes, indicating host Fy genotype may be important vaccine efficacy. Aim 1. To identify epitopes on PvDBPII recognized by strain-transcending neutralizing antibodies. Aim 2. To develop vaccine approaches to elicit strain-transcending blocking/invasion inhibitory antibodies to PvDBPII. Aim 3. To determine the role of the Duffy Fya as compared to Fyb phenotype in functional immune responses to PvDBPII in vitro and in vivo.