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，加上最近耐药恶性疟原虫寄生虫的迅速传播，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候选疫苗，这使得只有在满足特定的允许/不允许标准时才将单个抗原转移到疟疾疫苗开发管道中至关重要。该应用程序将对两种杰出的血期候选疫苗抗原，密切相关的裂殖子表面蛋白PfMSP3和PfMSP6应用如此严格的标准。本提案的长期目标是了解PfMSP3和PfMSP6序列在疟疾流行社区中如何随时间变化，并生成两种候选抗原所有亚域的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首次感染恶性疟原虫开始追踪个体，从诊断时开始，通过多年的多次随访，可以获得血清和恶性疟原虫DNA样本。在Specific Aim 1中，我们将通过在种群水平、传播季节之间以及在个体水平、同一个体后续感染之间跟踪这两个基因的等位基因间和等位基因内多样性，建立PfMSP3和PfMSP6遗传多样性的时间动态。特异性Aim 2将使用在特异性Aim 1中进行基因分型的个体感染血清来研究特异性PfMSP3和PfMSP6子结构域对功能性抗疟疾免疫发展的相对贡献。为了实现这一目标，我们将跟踪PfMSP3和PfMSP6每个子结构域的抗体水平，并使用抑制入侵和抗体依赖的细胞抑制实验来确定这些抗体在抑制恶性疟原虫生长方面的功能。由于低地方性研究地点和纵向队列设计的独特结合，我们将能够通过几轮单一分离感染来跟踪个体，并建立每种感染的基因型和对该感染的抗体反应。因此，结合来自两个特定目标的基因分型和抗体数据将使我们能够确定针对一个PfMSP3或PfMSP6等位基因产生的抗体是否在功能上对另一个具有交叉保护作用，并确定哪些子结构域与保护最密切相关。其基本原理是，通过了解PfMSP3/PfMSP6疫苗必须运作的多样性限制，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允许/不允许标准，将特定子域纳入或排除在疫苗开发过程中。因此，对疟疾疫苗设计的总体影响将是重大的，这是一个具有紧急公共卫生重要性的问题。恶性疟原虫每年夺去100多万人的生命，最近耐药疟原虫的迅速传播使恶性疟原虫疫苗的开发成为一项紧迫的公共卫生重点。该提案将重点关注两种突出的疫苗候选抗原，恶性疟原虫Merozoite表面蛋白3和6，并将使用从秘鲁伊基托斯一项独特的正在进行的疟疾队列研究中收集的DNA和血清样本，以确定这些抗原的不同亚结构域对功能性抗疟疾免疫发展的相对贡献。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排除特定的子域。

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.