Defining conserved epitopes on polymorphic malaria antigens

定义多态性疟疾抗原上的保守表位

• 批准号: 10557235
• 负责人: Evelien Margaretha Bunnik
• 金额: $ 54.37万
• 依托单位: UNIVERSITY OF TEXAS HLTH SCIENCE CENTER
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-02-19 至 2026-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10557235
• 关键词: Adult; Affinity; Antibodies; Antibody Response; Antibody-mediated protection; Antigens; B cell differentiation; B-Cell Antigen Receptor; B-Cell Development; Binding; Biological Assay; Blood; Cell Lineage; Cessation of life; Characteristics; Child; Clinical; Complex Mixtures; Data; Disease; Epitope Mapping; Epitopes; Erythrocytes; Failure; Freezing; Genes; Genetic Polymorphism; Genetic Variation; Immune; Immune response; Immunity; Immunoglobulin Class Switching; Immunoglobulin G; Immunoglobulin M; Immunoglobulin Somatic Hypermutation; Immunologics; Immunology; In Vitro; Individual; Infection; Invaded; Knowledge; Learning; Life Cycle Stages; Malaria; Malaria Vaccines; Maps; Mass Spectrum Analysis; Memory; Memory B-Lymphocyte; Molecular; Monoclonal Antibodies; Morbidity - disease rate; Mutagenesis; Nature; Parasites; Parasitology; Passive Immunization; Peripheral Blood Mononuclear Cell; Persons; Plasma Cells; Plasmodium falciparum; Positioning Attribute; Predisposition; Proteomics; Reverse engineering; Serology; Serum; Sporozoite vaccine; Sporozoites; Structure; Testing; Transcend; Uganda; Vaccination; Vaccine Design; Vaccines; Variant; X-Ray Crystallography; acquired immunity; cohort; design; experience; experimental study; falls; fighting; insight; malaria transmission; mortality; next generation; novel; prevent; response; structural biology; tool; vaccine candidate; vaccine development; vaccine trial

PROJECT SUMMARY Malaria is still responsible for an estimated 429,000 deaths and 212 million infections per year, the large majority among young children. Individuals living in endemic regions gradually develop an immune response that protects against symptomatic disease. Naturally acquired immunity targets the blood stage of the parasite’s life cycle and is largely dependent on antibody reactivity. Elicitation of a similar immune response by vaccination in young, non-immune children would dramatically reduce malaria morbidity and mortality. Various parasite antigens have been associated with protection against clinical disease. Most of these antigens are expressed in the merozoite stage and are involved in invasion of the red blood cell. However, vaccine trials based on these blood-stage antigens have thus far been unsuccessful. One factor contributing to the failure of blood stage vaccines is the extensive genetic diversity between different parasite strains that has resulted in strain-specific, but not strain- transcending, antibody responses. Studies of naturally acquired immunity suggest that protected individuals harbor antibodies against conserved epitopes. The identification of such conserved epitopes could serve as a blueprint for structure-based design of a malaria blood stage vaccine. We hypothesize that immunity against malaria is dependent on high affinity IgGs with cross-strain reactivity against merozoite antigens and that these antibodies can be used to define conserved epitopes on merozoite vaccine candidates. To test this hypothesis, we will compare the molecular and functional characteristics of antibodies directed against merozoite antigens among immune adults, semi-immune children and non-immune children living in Tororo, Uganda, a region with extremely high malaria transmission intensity, and use the most potent and broadly reactive antibodies for epitope mapping. In Specific Aim 1, we will isolate merozoite antigen-specific memory B cells from these individuals, test the ability of these antibodies to inhibit various malaria parasite strains in vitro, and map the epitopes of cross-strain reactive antibodies to define conserved epitopes on merozoite antigens. In Specific Aim 2, we will deep-sequence the memory B cell receptor repertoire to uncover the impact of life-long malaria exposure on the humoral immune response, analyze the repertoire of anti-merozoite serum antibodies and determine the cross-strain inhibitory activity and epitopes of dominant serum antibody clonotypes. Collectively, the results from these experiments will provide detailed information about the types of antibodies that a blood-stage vaccine should ideally elicit and will enable the design of novel immunogens to elicit strain- transcending antibodies against the malaria blood stage. In addition, it will provide insight into the overlap and differences between the memory B cell and serological compartments, and the selective mechanisms that drive B cell differentiation into plasma cells and memory B cells.

项目概要 据估计，疟疾每年仍导致 429,000 人死亡和 2.12 亿人感染，其中绝大多数 在幼儿中。生活在流行地区的个体逐渐形成免疫反应，以保护 对抗症状性疾病。自然获得的免疫力针对寄生虫生命周期的血液阶段， 很大程度上取决于抗体反应性。通过疫苗接种在年轻人中引发类似的免疫反应 没有免疫力的儿童将大大降低疟疾发病率和死亡率。各种寄生虫抗原具有 与预防临床疾病有关。这些抗原大部分在裂殖子中表达 阶段并参与红细胞的侵袭。然而，基于这些血液阶段的疫苗试验 迄今为止，抗原尚未成功。导致血期疫苗失败的因素之一是 不同寄生虫品系之间广泛的遗传多样性导致了品系特异性，但不是品系- 超越，抗体反应。对自然获得性免疫力的研究表明，受保护的个体 含有针对保守表位的抗体。此类保守表位的鉴定可以作为 疟疾血期疫苗基于结构的设计蓝图。我们假设对 疟疾依赖于具有针对裂殖子抗原的交叉菌株反应性的高亲和力 IgG， 这些抗体可用于定义裂殖子候选疫苗上的保守表位。测试 根据这个假设，我们将比较针对的抗体的分子和功能特征 生活在托罗罗的免疫成人、半免疫儿童和非免疫儿童中的裂殖子抗原， 乌干达是疟疾传播强度极高的地区，使用最有效、最广泛的 用于表位作图的反应性抗体。在具体目标 1 中，我们将分离裂殖子抗原特异性记忆 B 来自这些个体的细胞，测试这些抗体在体外抑制各种疟疾寄生虫菌株的能力， 并绘制交叉菌株反应性抗体的表位图​​，以定义裂殖子抗原上的保守表位。在 具体目标 2，我们将对记忆 B 细胞受体库进行深度测序，以揭示终生的影响 疟疾暴露对体液免疫反应的影响，分析抗裂殖子血清抗体库 并确定主要血清抗体克隆型的交叉菌株抑制活性和表位。 总的来说，这些实验的结果将提供有关抗体类型的详细信息 血液阶段疫苗应该理想地引发并能够设计新型免疫原来引发菌株- 超越抗疟疾血液阶段的抗体。此外，它将提供对重叠和 记忆 B 细胞和血清学区室之间的差异，以及驱动的选择机制 B细胞分化为浆细胞和记忆B细胞。