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 该R01应用的目的是发现自然获得保护的目标，以防止严重 恶性疟原虫疟疾并将其发展为新型血液疫苗候选者。 〜100 目前正在调查的疟疾疫苗候选物中，超过60％的候选人仅基于四个寄生虫 抗原和最先进的疫苗RTS，S，仅生成适度的保护1，2。 在先前的研究中，我们制定了一种高度创新的整个蛋白质组差异筛选策略 鉴定由抗性个体表达的抗体识别的寄生虫抗原的子集 但不是易感性的人。使用此策略，我们发现了Schizont Egress Antigen-1（PFSEA-1），一个 244-kDa寄生虫抗原，是抗体的靶标，在Schizont阶段捕获寄生虫，并且是 在n = 785个两个年龄的孩子的队列中，与严重的疟疾疾病的明显保护有关。 这是第一次表明，特异性阻断出口的抗体可以预防严重的疟疾 在人类中（科学4）。 在平行研究中，我们还确定了PFGARP，这是一种先前未识别的疫苗候选者 在感染RBC的RBC膜的外叶表面。高度不变的抗体 PFGARP的羧基末端（PFGARP-A，AA 411-673）在体外抑制寄生虫的生长99％ 通过杀死滋养体阶段寄生虫来对照（p <0.001）。许多机械测定表明 抗PfGARP与感染RBC表面的结合会诱导寄生虫编程的细胞死亡，因为 通过杂音核形态，胱天蛋白酶激活，线粒体去极化，DNA证明 碎裂和细胞内钙的释放。此外，非人类灵长类动物的疫苗接种 PFGARP作为脂质封装的mRNA配制了PFGARP，可显着保护恶性疟原虫挑战 与对照组相比（自然5）。 这些初步结果是基于使用耐药性和易感的血清的差异筛选 仅基于寄生虫血症的抗药性定义的个体。以前的工作证明了 只有一两个事件，儿童就会对严重疟疾产生抵抗，这种保护与 仅控制寄生虫血症6的反应。在当前的提案中，我们将将这一观察结果利用为 鉴定寄生虫抗原，这些抗原是抗体反应的靶标，在此期间获得和表达 严重疟疾发作的疗养阶段，并预防将来的严重疟疾发作。 我们将：1）在我们的肯尼亚西部全体学区域的现场进行案例对照研究至 识别患有严重疟疾和匹配对照的婴儿和儿童。 2）执行整个蛋白质组差异 使用该病例对照研究中的血清筛选，3）降低了以下疫苗研究的选定候选者 使用一套测定法（生长抑制作用，人类免疫性ePIDEPIDEMIologic研究和鼠疫苗试验）。