Maturation of human humoral immunity through repeat malaria challenges

通过重复疟疾挑战使人体体液免疫成熟

• 批准号: 10720245
• 负责人: Alison Elizabeth Roth
• 金额: $ 80.12万
• 依托单位: HENRY M. JACKSON FDN FOR THE ADV MIL/MED
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-05-24 至 2028-04-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10720245
• 关键词: Accounting; Address; Adult; Affinity; Animals; Antibodies; Antibody Formation; Antibody Repertoire; Antibody-mediated protection; Antigens; Appearance; Area; B-Lymphocytes; Biological Assay; Bite; Blood; CD19 gene; Cell Separation; Cells; Cessation of life; Child; Clinical; Clinical Trials; Clonal Expansion; Collaborations; Communicable Diseases; Country; Culicidae; Data; Detection; Development; Disease; Environment; Erythrocytes; Exposure to; Fever; Future; Generations; Genetic Polymorphism; Goals; Growth; Hepatocyte; Human; Humoral Immunities; Immune response; Immunity; Immunoglobulins; Immunophenotyping; In Vitro; Individual; Infection; Invaded; Legal patent; Liver; Malaria; Memory; Memory B-Lymphocyte; Micro Array Data; Modeling; Monitor; Natural Immunity; Parasite Control; Parasitemia; Parasites; Pattern; Peptides; Peripheral Blood Mononuclear Cell; Persons; Plasma; Plasma Cells; Plasmablast; Plasmodium; Plasmodium falciparum; Population; Predisposition; Production; Proliferating; Recombinants; Role; Sequence Analysis; Sorting; Sporozoites; Time; Vaccines; Virulent; Virus Diseases; Work; acquired immunity; cofactor; cytokine; design; in vitro Assay; malaria infection; multiplex assay; reduce symptoms; response; single cell sequencing; single-cell RNA sequencing; vaccine development; volunteer

Malaria continues to be among the world’s most virulent infectious diseases accounting for the death of ~0.4 million people a year. Unlike many viral infections, children usually have repeated clinical episodes, but by adulthood, the majority of individuals living in endemic areas are protected against disease, not parasite carriage. The reasons for this gradual response to the parasite are not well established. Eventually antibodies are produced in adults that reduce parasitemia and fever when passively transferred to children with malaria, indicating a role for antibody-mediated immunity. However, it has been difficult to study this slow development of immunity to natural infection in the field, since there is no way to control for parasite strain or exposure timing. Animal studies, while allowing controlled inoculations of specific parasite strains, are complicated to apply to human infections due to differences across host and parasite species. To address these limitations, we carried out a clinical trial to systematically evaluate the immune response of malaria-naïve volunteers to an initial exposure to uninfected mosquitoes, followed 2 months later with Plasmodium falciparum (Pf)-infected mosquito bites and then 2-3 subsequent challenges each with the mosquitoes infected with the same strain of Pf. The use of the controlled human malaria infection (CHMI) model allowed control of the timing of parasite exposure and therefore the early response to sequential infections could be directly monitored. As observed with children in malaria endemic countries, the initially naïve volunteers continued to be susceptible through the multiple infectious challenges, but the time to a positive blood smear, termed patency, increased significantly overtime. Symptoms decreased significantly by the 3rd and 4th challenges indicating the beginning of clinical immunity and preliminary data indicates plasma from the two subjects with the longest patency delay reduced liver cell invasion consistent with the development of pre-erythrocytic immunity. This unique, well- controlled infection model allows us to carefully follow the production of antibody-secreting plasma cells and parasite-specific memory B cells from before parasite exposure through 3 to 4 challenges with mosquitoes infected with the same strain of P. falciparum. Our preliminary analysis of the antibody repertoire of circulating plasma cells demonstrates marked clonal expansion followed by population collapse and the appearance of distinct clones. We hypothesize that B cells stimulated by the parasite proliferate and differentiate preferentially into plasma cells, not memory cells. Such a model could explain the lack of a sustained memory response to infection and subsequent delay in the acquisition of immunity. The specific aims are 1) Characterize parasite- specific memory B cell production through repeat challenges. 2) Evaluate parasite-specific memory B cells isolated after each CHMI to parasite stimulation in vitro. 3) Assess the Pf liver and blood stage growth inhibition through repeated CHMI. Together the results will advance our understanding of the memory response to Plasmodium, which is critical for the development of protective immunity.

疟疾仍然是世界上最致命的传染病之一，约导致 0.4 人死亡 每年 100 万人。与许多病毒感染不同，儿童通常会出现反复的临床发作，但通过 成年后，大多数生活在流行地区的人都可以免受疾病的侵害，而不是寄生虫的侵害 运输。对寄生虫产生这种逐渐反应的原因尚不清楚。最终产生抗体 成人体内产生，当被动转移给患有疟疾的儿童时，可以减少寄生虫血症和发烧， 表明抗体介导的免疫的作用。然而，研究这种缓慢的发展却很困难。 由于无法控制寄生虫菌株或暴露，因此对野外自然感染的免疫力 定时。动物研究虽然允许对特定寄生虫菌株进行受控接种，但其实施起来很复杂 由于宿主和寄生虫物种之间的差异，适用于人类感染。为了解决这些限制， 我们进行了一项临床试验，系统地评估从未患过疟疾的志愿者对疟疾的免疫反应。 最初接触未感染的蚊子，两个月后接触感染恶性疟原虫 (Pf) 的蚊子 蚊子叮咬，然后用感染相同毒株的蚊子进行 2-3 次后续挑战 Pf。使用受控人类疟疾感染（CHMI）模型可以控制寄生虫的时间 因此可以直接监测暴露情况以及对连续感染的早期反应。据观察 对于疟疾流行国家的儿童来说，最初天真的志愿者仍然容易受到影响 多重感染挑战，但血涂片呈阳性的时间（称为通畅）增加了 明显加班。第 3 次和第 4 次挑战后症状明显减轻，表明开始 临床免疫和初步数据表明血浆来自具有最长通畅延迟的两名受试者 肝细胞侵袭减少与红细胞前免疫的发展一致。这种独特的、良好的 受控感染模型使我们能够仔细跟踪分泌抗体的浆细胞的产生和 在接触寄生虫之前通过 3 到 4 次蚊子挑战获得的寄生虫特异性记忆 B 细胞 感染同一种恶性疟原虫。我们对循环抗体库的初步分析 浆细胞表现出明显的克隆扩张，随后群体崩溃并出现 不同的克隆。我们假设寄生虫刺激的 B 细胞优先增殖和分化 进入浆细胞，而不是记忆细胞。这样的模型可以解释缺乏持续的记忆反应 感染以及随后获得免疫力的延迟。具体目标是 1) 表征寄生虫- 通过重复挑战产生特定的记忆 B 细胞。 2) 评估寄生虫特异性记忆 B 细胞 每次 CHMI 后进行体外寄生虫刺激。 3) 评估Pf肝脏和血液阶段生长抑制 通过反复CHMI。这些结果将共同促进我们对记忆反应的理解 疟原虫，对于保护性免疫力的发展至关重要。