Human B Cell Responses to Malaria Vaccination and Infect

人类 B 细胞对疟疾疫苗和感染的反应

• 批准号: 7313435
• 负责人: susan pierce
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7313435
• 关键词: Human; Cell; Responses; Malaria; Vaccination

A vaccine to combat malaria is a highly desirable public health tool to reduce morbidity and mortality in African children. In order to achieve this goal it will be important to gain a detailed understanding of both the nature of the immune response to the current vaccine candidates as well as the immunological status of individuals living in areas in African where malaria is endemic. Over the reporting period this project represented a collaborative effort between Dr. Pierce and Dr. Louis Miller and his colleagues in the Malaria Vaccine Development Unit (MVDU). The immune response at the cellular level was evaluated in individuals in the U.S. enrolled in two clinical trials of the Plasmodium falciparum vaccine candidate, AMA-1 on alum, and one trial of AMA-1 on alum plus the TLR-9 ligand CpG, and in African adults enrolled in parallel studies in Mali. In addition, a study was initiated in Mali to determine the effect of malaria infection on the generation and maintenance of memory B cells. To evaluate the immune status of these individuals, advantage was taken of new and emerging information concerning the function of discrete subsets of lymphocytes in immune responses and the availability of serological reagents to identify these. The B cell antibody response to malaria is believed to be central to the control of parasite infections and thus our initial studies focused on a characterization of B cells in the peripheral blood of individuals enrolled in phase 1 vaccine clinical trials in the U.S. and in Africa. Peripheral blood cells were analyzed by flow cytometry for the B cell markers CD19, CD27, and CD38. Fluorescently labeled AMA-1 was used to identify antigen-specific B cells. In addition, antigen-specific antibody secreting plasma cells were identified by ELISPOT and memory B cells by their response in vitro to the TLR 9 ligand CpG. Cells were analyzed prior to vaccination and at days 3, 7 and 14 following the primary immunization and the secondary immunization (given either 28 or 56 days after the primary). The results acquired thus far showed that the percentage of CD19+ B cells did not change in response to vaccination. However, the number of plasma cells defined as CD27+ and CD38+ and either CD19+ on CD19-, showed an increase between 7 and 14 days after the first vaccination and 3 days after the second vaccination. The effect of vaccination was also mirrored in an increase in the number of memory B cells, defined as CD27+ cells, 3 to 7 days after both the primary and secondary immunization. Preliminary results indicate that the number of antigen-specific memory B cells increased in the periphery after the primary but not after the secondary immunization. Parallel analyses of the B cells in Africans enrolled in a similar Phase I study of AMA-1 or alum showed similar overall B cell response to vaccination. However, memory B cells appeared in the peripheral blood early, at three days post primary vaccination suggesting that individuals living in endemic areas are already immune to AMA-1. Similar analyses are in progress to analyze the memory B cell response to a vaccine containing AMA-1 on alum and CpG in a Phase I trial in the U.S. A similar analyses is planned for both AMA-1 on alum plus CpG Phase I trial in Mali. These results are encouraging indicating that discrete changes in relevant B cell subpopulations can be detected in response to vaccination. These changes may ultimately provide important new parameters to monitor the efficacy of vaccines and guide future vaccine strategies. At present, there is little known about the immunological status at the cellular level of the target population for the vaccine, namely children, in Africa chronically infected with malaria. A detailed analysis of the immune cells in the peripheral blood of chronically infected individuals and a comparison of their profiles with that of nonimmune and vaccinated individuals should provide important new information concerning the repercussion of malaria infection on the immune system and the impact of those effects on the potential to respond to current vaccine candidates. In collaboration with scientists at the MRTC in Mali, we initiated in May 2006, a study to characterize the peripheral blood cells of children and adults in areas in Africa where malaria is endemic. The analyses is a longitudinal study correlating the levels of parasitemia and the immune cell profile in individuals. Lastly, studies will be initiated to determine the effect of malaria infection on both the generation and maintenance of immunological memory. Several anecdotal observations suggest that immunological memory is difficult to establish and only short-lived in individuals living in malaria endemic regions. A clinical protocol will be developed to enroll recent immigrants to the U.S. from West Africa who have malaria infections. These individuals will be treated with anti-malaria drugs and vaccinated for polio and the memory B cell and plasma cells response to polio and to a panel of malaria antigens will be followed with time. The results of this study will hopefully provide new information concerning the generation and maintenance of immunological memory during and following malaria infections.

防治疟疾的疫苗是降低非洲儿童发病率和死亡率的一个非常可取的公共卫生工具。为了实现这一目标，重要的是要详细了解对目前候选疫苗的免疫反应的性质以及生活在非洲疟疾流行地区的个人的免疫状况。在本报告所述期间，该项目是Pierce博士和Louis米勒博士及其疟疾疫苗开发股同事之间的合作努力。在美国参加两项恶性疟原虫候选疫苗AMA-1明矾临床试验和一项AMA-1明矾加TLR-9配体CpG试验的个体中，以及在马里参加平行研究的非洲成年人中，评估了细胞水平的免疫应答。此外，在马里开展了一项研究，以确定疟疾感染对记忆B细胞生成和维持的影响。为了评估这些人的免疫状态，利用了新的和新兴的信息，关于离散的淋巴细胞亚群在免疫反应中的功能和血清学试剂的可用性，以确定这些。对疟疾的B细胞抗体应答被认为是控制寄生虫感染的核心，因此我们的初步研究集中于在美国和非洲参加1期疫苗临床试验的个体的外周血中的B细胞的表征。通过流式细胞术分析外周血细胞的B细胞标志物CD 19、CD 27和CD 38。免疫标记的AMA-1用于鉴定抗原特异性B细胞。此外，通过ELISPOT鉴定分泌抗原特异性抗体的浆细胞，并通过它们对TLR 9配体CpG的体外应答鉴定记忆B细胞。在接种前以及初次免疫和二次免疫（初次免疫后28或56天给予）后第3、7和14天分析细胞。迄今为止获得的结果表明，CD 19 + B细胞的百分比在疫苗接种后没有变化。然而，定义为CD 27+和CD 38+以及CD 19 +/CD 19-的浆细胞数量在首次接种后7 - 14天和第二次接种后3天显示增加。初次和二次免疫后3 - 7天，记忆B细胞（定义为CD 27+细胞）数量增加也反映了疫苗接种的效果。初步结果表明，抗原特异性记忆B细胞的数量在初次免疫后而不是在二次免疫后在外周中增加。对参加AMA-1或明矾的类似I期研究的非洲人的B细胞进行的平行分析显示，对疫苗接种的总体B细胞反应相似。然而，记忆B细胞早期出现在外周血中，在初次接种后三天，表明生活在流行地区的个体已经对AMA-1免疫。类似的分析正在进行中，以在美国的I期试验中分析记忆B细胞对含有AMA-1的明矾和CpG的疫苗的应答。计划在马里对AMA-1的明矾加CpG的I期试验进行类似的分析。这些结果是令人鼓舞的，表明可以检测到相关B细胞亚群对疫苗接种的反应的离散变化。这些变化可能最终提供重要的新参数，以监测疫苗的有效性，并指导未来的疫苗战略。 目前，对疫苗目标人群，即非洲慢性疟疾感染儿童的细胞免疫状况知之甚少。详细分析慢性感染者外周血中的免疫细胞，并将其与非免疫和接种疫苗者的免疫细胞进行比较，应提供有关疟疾感染对免疫系统的影响以及这些影响对当前候选疫苗的潜在反应的重要新信息。2006年5月，我们与马里MRTC的科学家合作，启动了一项研究，以确定非洲疟疾流行地区儿童和成人外周血细胞的特征。该分析是一项纵向研究，将寄生虫血症水平与个体中的免疫细胞谱相关联。最后，将开展研究，以确定疟疾感染对免疫记忆的产生和维持的影响。一些轶事观察表明，免疫记忆很难建立，只有短暂的个人生活在疟疾流行地区。将制定一项临床方案，招募最近从西非到美国的疟疾感染者。这些人将接受抗疟疾药物治疗，接种小儿麻痹症疫苗，并将随着时间的推移跟踪记忆B细胞和浆细胞对小儿麻痹症和一组疟疾抗原的反应。本研究的结果有望为疟疾感染期间和之后免疫记忆的产生和维持提供新的信息。