Human B Cell Response to Malaria Vaccination

人类 B 细胞对疟疾疫苗的反应

• 批准号: 7196730
• 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/7196730
• 关键词: Africa; B lymphocyte; Plasmodium falciparum; United States; antigen presentation; biotechnology; cellular immunity; clinical trial phase I; flow cytometry; human subject; human therapy evaluation; immune response; immunologic memory; malaria; malaria vaccines; plasma cells; vaccine development; vaccine evaluation

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 in African adults enrolled in a parallel study in Mali. 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 study are in progress and cells are being analyzed from volunteers in two U.S. trials. 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. We propose to characterize the peripheral blood cells of children and adults in areas in Africa where malaria is endemic. The analyses will be carried out longitudinally 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种非常可取的公共卫生工具。为了实现这一目标，必须详细了解对当前候选疫苗的免疫反应的性质，以及生活在疟疾流行的非洲地区的个人的免疫状况。在本报告所述期间，该项目是皮尔斯博士和路易斯·米勒博士及其疟疾疫苗发展股同事之间的合作努力。细胞水平的免疫反应是在美国参加恶性疟原虫候选疫苗AMA-1明矾临床试验的个人以及在马里参加一项平行研究的非洲成年人中评估的。为了评估这些个体的免疫状态，利用了关于离散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的新的和新兴的信息来鉴定这些淋巴细胞亚群。疟疾的B细胞抗体反应被认为是控制寄生虫感染的核心，因此我们最初的研究集中在美国和非洲参加第一阶段疫苗临床试验的个体的外周血液中B细胞的特征。外周血细胞用流式细胞仪分析B细胞标志物CD19、CD27和CD38。用荧光标记的AMA-1鉴定抗原特异性B细胞。此外，ELISPOT和Memory B细胞通过对TLR9配体CpG的体外反应来鉴定分泌抗原特异性抗体的浆细胞。在接种前以及初次免疫和二次免疫(初次免疫后28天或56天)后的第3、7和14天对细胞进行分析。到目前为止所获得的结果表明，CD19+B细胞的百分比不会因接种疫苗而改变。而CD27+、CD38+和CD19-的浆细胞数在第一次免疫后7~14天和第二次免疫后3天呈上升趋势。接种疫苗的效果还反映在第一次和第二次免疫后3至7天记忆B细胞(被定义为CD27+细胞)数量的增加。初步结果表明，初次免疫后外周血中抗原特异性记忆B细胞数量增加，二次免疫后未见明显变化。对参加类似研究的非洲人的B细胞的平行分析正在进行中，在美国的两项试验中，志愿者的细胞正在进行分析。这些结果令人鼓舞，表明可以检测到接种疫苗后相关B细胞亚群的离散变化。这些变化最终可能为监测疫苗的效力和指导未来的疫苗战略提供重要的新参数。 目前，对非洲长期感染疟疾的目标人群，即儿童，在细胞水平上的免疫状况知之甚少。对慢性感染者外周血中免疫细胞的详细分析，并将其特征与未免疫和接种疫苗的个体进行比较，应该会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反应潜力的重要新信息。我们建议对疟疾流行的非洲地区的儿童和成人的外周血细胞进行表征。这些分析将在纵向上将个人的寄生虫血症水平和免疫细胞图谱联系起来。最后，将启动研究，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，而且只在疟疾流行地区的个人中短暂存在。将制定一项临床方案，将最近从西非移民到美国的感染疟疾的人纳入其中。这些人将接受抗疟疾药物治疗，并接种脊髓灰质炎疫苗，记忆B细胞和浆细胞对脊髓灰质炎和一组疟疾抗原的反应将随着时间的推移而变化。这项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。