Regulation and function of B cells during malaria infection- Resubmission

 描述(申请人提供)：原生动物寄生虫疟原虫是疟疾的病原体，疟疾仍然是当今世界最突出的公共卫生挑战之一。疟原虫特异的抗体反应对于预防人类和小鼠随后的再次感染很重要。然而，虽然小鼠在一次感染后得到保护，但人类的保护性免疫发展缓慢，因为需要反复感染才能产生保护性抗体。我们的长期目标是确定在感染疟原虫后小鼠如何产生和维持保护性抗体反应，以便我们能够利用这些信息来了解为什么抗体介导的免疫在人类中发展缓慢。疟原虫特异性记忆B细胞是在小鼠和人类感染后产生的；然而，令人惊讶的是，关于它们的特异性、表型、来源和对疟疾抗原的亲和力的信息很少。我们的初步研究表明，在疟原虫感染后，记忆B细胞池中存在多层异质性，我们假设记忆B细胞池中的这种异质性有助于继发感染的功能多样性。我们建议(目标1)描述约氏疟原虫17x感染小鼠后记忆B细胞的异质性群体，并确定其来源。然后，我们将(目标2)确定继发感染后不同亚群的记忆B细胞的功能。此外，我们的初步研究已经确定了两类记忆T细胞，它们表达与滤泡辅助T细胞相关的标记。我们建议(目标3)确定这些记忆T细胞群体是否能够分化为支持继发感染时产生抗体的功能性滤泡辅助T细胞，以及它们是否需要在攻击后进行保护。为了实现这些目标，我们开发了创新的工具，利用表达鸡蛋清溶菌酶(HEL)的寄生虫，在细胞水平上跟踪寄生虫特异的B细胞反应。利用HEL特异的转基因B细胞和一种新的基于磁珠的浓缩技术，我们可以监测和跟踪表达HEL的寄生虫感染后抗原特异的B细胞的命运。这些创新的工具和方法将为理解针对疟原虫的保护性免疫是如何产生、维持和在二次免疫反应中发挥作用提供宝贵的见解，并将确定这一过程中涉及的关键成分。

 DESCRIPTION (provided by applicant): The protozoan parasite Plasmodium is the causative agent of malaria, which remains one of the most prominent public health challenges in the world today. Plasmodium-specific antibody responses are important for protecting against subsequent reinfections in humans and mice. However, while mice are protected after a single infection, protective immunity is slow to develop in humans due to the requirement of repeated infections for the generation of protective antibodies. Our long-term goal is to determine how protective antibody responses are generated and maintained in mice after Plasmodium infection, so that we can utilize this information to understand why antibody-mediated immunity is slow to develop in humans. Plasmodium-specific memory B cells are generated after infection in mice and humans; however, surprisingly little information is available regarding their specificity, phenotype, origin and affinity for malarial antigens. Our preliminary studies indicate that there are layers of heterogeneity within the memory B cell pool after Plasmodium infection and we hypothesize that this heterogeneity in the memory B cell pool contributes to functional diversity in a secondary infection. We propose to (Aim 1) characterize heterogeneous populations of memory B cells after P. yoelii 17X infection in mice and determine their origin. We will then (Aim 2) determine the function of distinct subsets of memory B cells after secondary infection. Additionally, our preliminary studies have identified two populations of memory T cells that express markers associated with follicular helper T cells. We propose to (Aim 3) determine if these populations of memory T cells are capable of differentiating into functional follicular helpe T cells that can support Ab production in a secondary infection and whether they are required for protection after challenge. To accomplish these goals we have developed innovative tools to track parasite- specific B cell responses at the cellular level utilizing parasites engineered to express hen egg-white lysozyme (HEL). Using HEL-specific transgenic B cells and a novel magnetic-bead based enrichment technique we can monitor and track the fate of antigen-specific B cells after infection with HEL expressing parasites. These innovative tools and approaches will provide valuable insight into understanding how protective immunity against Plasmodium is generated, is maintained, and functions in a secondary immune response and will identify key components involved in this process.