P. falciparum vaccine: Evaluating candidacy of PfMSP3/PfMSP6 in an endemic settin

描述（由申请人提供）：疟疾作为全球三大传染病杀手之一的地位，加上最近抗药性恶性疟原虫寄生虫的快速传播，使得开发有效的恶性疟原虫疫苗成为当务之急。然而，恶性疟原虫生命周期的复杂性及其基因组的大小提供了大量潜在的疫苗候选物，使得只有当单个抗原满足特定的go/no-go标准时，它们才能沿着疟疾疫苗开发管道向下移动。本申请将这种严格的标准应用于两种杰出的血液阶段候选疫苗抗原，即密切相关的裂殖子表面蛋白PfMSP 3和PfMSP 6。该提案的长期目标是了解PfMSP 3和PfMSP 6序列在疟疾流行社区中如何随时间变化，并为两种候选抗原的所有子域生成保护数据的关键相关性。这项工作之所以成为可能，是因为我们获得了作为秘鲁亚马逊地区正在进行的纵向队列研究的一部分收集的独特样本，该研究的建立使我们能够从第一次感染恶性疟原虫开始跟踪个体，从诊断时起，通过几年的多次随访，获得血清和恶性疟原虫DNA样本。在具体目标1中，我们将建立PfMSP 3和PfMSP 6遗传多样性的时间动态，通过以下这两个基因的等位基因间和等位基因内的多样性，无论是在人口水平，传播季节之间，还是在个体水平，在同一个人的后续感染之间。特异性目标2将使用已在特异性目标1中进行基因分型的个体感染的血清，以研究特异性PfMSP 3和PfMSP 6亚结构域对功能性抗疟疾免疫发展的相对贡献。为了实现这一点，我们将跟踪针对PfMSP 3和PfMSP 6的每个亚结构域的抗体水平，并且还使用侵袭抑制和抗体依赖性细胞抑制测定来建立这些抗体在抑制恶性疟原虫寄生虫生长中的功能。由于低流行研究地点和纵向队列设计的独特组合，我们将能够通过几轮单一分离株感染来跟踪个体，并建立每种感染的基因型和对该感染的抗体反应。因此，将来自两个特定目的的基因分型和抗体数据相结合将使我们能够确定针对一个PfMSP 3或PfMSP 6等位基因产生的抗体是否对另一个具有功能性交叉保护，以及确定哪些亚结构域与保护最密切相关。其基本原理是，通过了解PfMSP 3/PfMSP 6疫苗必须操作的多样性约束以及每个子域对功能性抗疟疾免疫的相对贡献，我们将能够应用合理的去/不去标准来在疫苗开发过程中或之外统治特定子域。因此，对疟疾疫苗设计这一具有紧迫公共卫生重要性的问题的总体影响将是重大的。恶性疟原虫寄生虫每年杀死100多万人，最近抗药性寄生虫的快速传播使恶性疟原虫疫苗的开发成为紧迫的公共卫生优先事项。该提案集中于两种突出的疫苗候选抗原，恶性疟原虫裂殖子表面蛋白3和6，并将使用从秘鲁伊基托斯正在进行的独特疟疾队列研究中收集的DNA和血清样品，以确定这些抗原的不同亚结构域对功能性抗疟疾免疫力的发展的相对贡献。这些数据将直接影响疫苗设计，使我们能够在正在进行的疟疾疫苗开发过程中确定特定的子域。

DESCRIPTION (provided by applicant): The status of malaria as one of the top three global infectious disease killers, coupled with the recent rapid spread of drug-resistant Plasmodium falciparum parasites, have made the development of an effective P. falciparum vaccine an urgent priority. However the complexity of the P. falciparum life cycle and the size of its genome present a large number of potential vaccine candidates, making it critical that individual antigens are moved down the malaria vaccine development pipeline only when they meet specific go/no-go criteria. This application will apply such rigorous criteria to two outstanding blood stage candidate vaccine antigens, the closely related merozoite surface proteins PfMSP3 and PfMSP6. The long-term objectives of this proposal are to understand how PfMSP3 and PfMSP6 sequences change over time in a malaria-endemic community and to generate critical correlation of protection data for all sub-domains of both candidate antigens. This work is made possible by our access to unique samples that are collected as part of an ongoing longitudinal cohort study in the Peruvian Amazon, the set-up of which allows us to track individuals from their first P. falciparum infection, with sera and P. falciparum DNA samples available from the time of diagnosis through multiple follow-up visits over the course of several years. In Specific Aim 1 we will establish the temporal dynamics of PfMSP3 and PfMSP6 genetic diversity by following inter- and intra-allelic diversity in these two genes both at a population level, between transmission seasons, and at an individual level, between subsequent infections in the same individual. Specific Aim 2 will use sera from individual infections that have been genotyped in Specific Aim 1 to investigate the relative contribution of specific PfMSP3 and PfMSP6 sub-domains to the development of functional anti-malaria immunity. To achieve this we will both follow antibody levels against each sub-domain of PfMSP3 and PfMSP6, and also use inhibition of invasion and antibody dependent cellular inhibition assays to establish the function of these antibodies in inhibiting P. falciparum parasite growth. Because of the unique combination of a hypoendemic study site and a longitudinal cohort design we will be able to track individuals through several rounds of single isolate infections, and establish both the genotype of each infection and the antibody response to that infection. Combining genotyping and antibody data from the two specific aims will therefore allow us to establish whether antibodies generated against one PfMSP3 or PfMSP6 allele are functionally cross-protective against the other, as well as to establish which sub-domains most closely correlate with protection. The rationale is that by understanding the diversity constraints within which a PfMSP3/PfMSP6 vaccine must operate and the relative contribution of each sub-domain to functional anti-malaria immunity, we will be able to apply rational go/no-go criteria to rule specific sub-domains in or out of the vaccine development process. The overall impact on malaria vaccine design, a question of urgent public health importance, will therefore be significant. Plasmodium falciparum parasites kill more than 1 million people each year and the recent rapid spread of drug resistant parasites have made the development of a P. falciparum vaccine an urgent public health priority. This proposal focuses on two outstanding vaccine candidate antigens, P. falciparum Merozoite Surface Proteins 3 and 6, and will use DNA and sera samples collected from a unique ongoing malaria cohort study in Iquitos, Peru, to establish the relative contribution of distinct sub-domains of these antigens to the development of functional anti-malaria immunity. This data will directly impact vaccine design by allowing us to rule specific sub-domains in or out of the ongoing malaria vaccine development process.