Identifying the targets of protective immunity to severe falciparum malaria

确定严重恶性疟疾的保护性免疫目标

• 批准号: 10893666
• 负责人: Jonathan D. Kurtis
• 金额: $ 50.01万
• 依托单位: BROWN UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-04 至 2024-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10893666
• 关键词: Age; Ambulatory Care Facilities; Antibodies; Antibody Response; Antigen Targeting; Antigens; Aotus primate; Binding; Biological Assay; Blocking Antibodies; Blood; Calcium; Case/Control Studies; Caspase; Cell Death; Cells; Cerebral Malaria; Child; Complement; Complement Activation; DNA Fragmentation; Data; Disease; Encapsulated; Enrollment; Evaluation; Falciparum Malaria; Future; Glutamic Acid; Goals; Growth; Hospitals; Human; Immune; Immune Sera; Immunity; Immunologic Epidemiology; In Vitro; Individual; Infant; Investigation; Kenya; Libraries; Lipids; Malaria; Malaria Vaccines; Measures; Membrane; Messenger RNA; Mitochondria; Modeling; Morphology; Mus; Nature; Nuclear; Orthologous Gene; Parasitemia; Parasites; Phage Display; Phagocytosis; Phase; Phase I Clinical Trials; Plasma; Plasmodium falciparum; Predisposition; Proteins; Proteome; Resistance; Resistance development; Site; Surface; Vaccination; Vaccines; Work; antibody test; candidate selection; cohort; comparison control; design; innovation; nonhuman primate; novel; novel vaccines; polyclonal antibody; response; screening; vaccine candidate; vaccine trial

ABSTRACT The goal of this R01 application is to discover the targets of naturally acquired protection against severe Plasmodium falciparum malaria and to develop them as novel blood-stage vaccine candidates. Of the ~100 malaria vaccine candidates currently under investigation, more than 60% are based on only four parasite antigens and the most advanced vaccine, RTS,S, generates only modest protection 1, 2. In previous studies, we developed a highly innovative whole proteome differential screening strategy which identifies the subset of parasite antigens that are recognized by antibodies expressed by resistant individuals but not susceptible individuals. Using this strategy, we discovered Schizont Egress Antigen-1 (PfSEA-1), a 244-kDa parasite antigen that is the target of antibodies which arrest parasites at the schizont stage and are associated with significant protection from severe malarial disease in a cohort of n=785 two yr old children. This is the first demonstration that antibodies that specifically block egress can protect against severe malaria in humans (Science 4). In parallel studies, we also identified PfGARP, a previously unrecognized vaccine candidate which localized to the exofacial surface of the RBC membrane in trophozoite infected RBC. Antibodies to the highly invariant carboxyl terminal of PfGARP (PfGARP-A, aa 411-673) inhibit parasite growth in vitro by 99% compared to controls (P < 0.001) by killing trophozoite stage parasites. Numerous mechanistic assays demonstrated that the binding of anti-PfGARP to the surface of the infected RBC induces parasite programed cell death as evidenced by pyknotic nuclear morphology, caspase activation, mitochondrial depolarization, DNA fragmentation, and release of intracellular calcium. In addition, vaccination of non-human primates with PfGARP formulated as a lipid encapsulated mRNA results in significant protection from P. falciparum challenge compared to controls (Nature 5). These preliminary results were based on differential screening using sera from resistant and susceptible individuals with the definition of resistance based solely on parasitemia. Previous work has demonstrated that children develop resistance to severe malaria after only one or two episodes, and this protection is distinct from responses that simply control parasitemia 6. In the current proposal, we will capitalize on this observation to identify parasite antigens that are targets of antibody responses which are acquired and expressed during the convalescent phase of an episode of severe malaria and protect against future episodes of severe malaria. We will: 1) conduct a case-control study at our field site in a holoendemic region of western Kenya to identify infants and children with severe malaria and matched controls. 2) perform whole proteome differential screening using sera from this case-control study, and 3) down select candidates for follow-on vaccine studies using a suite of assays (growth inhibition, human immunoepidemiologic studies, and murine vaccine trials).

抽象的 此 R01 应用程序的目标是发现自然获得的针对严重疾病的保护的目标 恶性疟原虫疟疾，并将其开发为新型血液阶段候选疫苗。约 100 个中 目前正在研究的候选疟疾疫苗，超过 60% 仅基于四种寄生虫 抗原和最先进的疫苗 RTS,S 只能产生适度的保护 1、2。 在之前的研究中，我们开发了一种高度创新的全蛋白质组差异筛选策略， 识别由抗性个体表达的抗体识别的寄生虫抗原子集 但不是易感人群。使用这种策略，我们发现了裂殖体出口抗原-1 (PfSEA-1)，一种 244-kDa 寄生虫抗原，是在裂殖体阶段阻止寄生虫的抗体的目标，并且是 在由 785 名两岁儿童组成的队列中，该药物可显着预防严重疟疾疾病。 这是首次证明专门阻止出口的抗体可以预防严重疟疾 在人类中（科学 4）。 在平行研究中，我们还发现了 PfGARP，一种以前未被识别的候选疫苗，它定位于 到滋养体感染的红细胞中红细胞膜的外表面。高度不变的抗体 与相比，PfGARP 的羧基末端（PfGARP-A，aa 411-673）在体外抑制寄生虫生长 99% 通过杀死滋养体阶段寄生虫来控制（P < 0.001）。大量的机械分析表明 抗 PfGARP 与受感染红细胞表面的结合诱导寄生虫程序性细胞死亡 通过核固缩形态、半胱天冬酶激活、线粒体去极化、DNA 来证明 碎裂和细胞内钙的释放。此外，对非人类灵长类动物进行疫苗接种 PfGARP 配制为脂质封装的 mRNA，可显着防止恶性疟原虫的攻击 与对照相比（自然 5）。 这些初步结果基于使用抗药性和易感性菌株的血清进行差异筛选 耐药性定义仅基于寄生虫血症的个体。之前的工作已经证明 儿童仅在一两次发作后就对严重疟疾产生了抵抗力，这种保护与 仅控制寄生虫血症的应对措施 6. 在当前提案中，我们将利用这一观察结果 识别作为抗体反应目标的寄生虫抗原，这些抗原是在 严重疟疾发作的恢复期并预防未来严重疟疾发作。 我们将：1）在肯尼亚西部大流行地区的现场进行病例对照研究，以 识别患有严重疟疾的婴儿和儿童以及匹配的对照。 2) 进行全蛋白质组差异 使用病例对照研究中的血清进行筛选，以及 3) 筛选后续疫苗研究的候选者 使用一套测定（生长抑制、人类免疫流行病学研究和鼠疫苗试验）。