Effects of neonatal microbial exposure on anti-polysaccharide B cell development

描述（由申请人提供）：革兰氏阴性肠道感染和革兰氏阳性微生物，包括肺炎链球菌，A群（GAS）和B群（GBS）链球菌，是严重细菌感染的主要原因，并导致全球新生儿死亡。在人和小鼠中，早期B细胞产生针对这些和类似生物体的抗体对于防止感染及其血液传播至关重要。然而，适应性免疫系统在生命早期受到损害，人类婴儿对多糖（PS）的保护性抗体反应需要两年以上的时间才能形成。我们的长期目标是对新生儿对与婴儿健康明确相关的多种生物体的免疫反应进行仔细的对照研究。我们的直接目标是使用小鼠模型来研究新生儿免疫系统与细菌成分的相互作用，从而产生持久的保护。我们的方法背后的基本原理是，对控制新生儿机体可塑性的机制的理解将导致新的治疗或疫苗接种选择，以治疗和预防这些生物体的感染。由于小鼠模型为无法在人类身上进行的实验提供了独特的机会，我们预计这一知识将有助于了解人类婴儿对感染的反应，有助于开发更有效的疫苗策略，并有助于了解疫苗干扰的可能后果。这些目标将通过三个目标来实现：1)确定影响B细胞克隆库建立的因素，以表达由肺炎链球菌、化脓性链球菌（GAS）、无乳链球菌（GBS）和阴沟链球菌表达的多糖；2)确定暴露于这些生物体引起的新兴B细胞的表型、亚群分布和功能变化。3)分离和确定从新生免疫的成年小鼠中提取的单克隆抗体的特性，这些单克隆抗体对这些生物体的感染提供最佳的保护。通过选择研究这个多成员小组，我们将开发独特的模型，我们可以在其中研究B细胞克隆竞争和其他相互作用在发育过程中。我们还开发了一组全面的抗独特型抗体和标记抗原，使我们能够准确地定量B细胞克隆频率，并通过流式细胞术追踪单一抗原结合B细胞在疫苗接种或感染我们的模型生物后的发展。此外，我们还构建了带有杂交瘤VH基因的免疫球蛋白转基因小鼠，以响应这些生物表达的PS。我们的研究结果有望对理解免疫B细胞记忆的发育及其在整个生命中的持久性产生影响。未来可能会引入更多的儿童疫苗，这使得我们必须更好地了解多种疫苗、新生儿慢性感染和合并感染对进一步接种疫苗或感染后的免疫反应可能产生的疫苗干扰。

DESCRIPTION (provided by applicant): Gram-negative enteric infections and Gram-positive organisms, including Streptococcus pneumoniae, Group A (GAS) and Group B (GBS) streptococci are leading causes of serious bacterial infections and contribute to neonatal deaths worldwide. In man and mouse the early B cell production of antibodies to these and similar organisms are essential for protection from infection and their blood-borne dissemination. However the adaptive immune system is compromised in early life and human infant protective antibody responses to polysaccharide (PS) take more than two years to develop. Our long range goal is to conduct carefully controlled studies of the neonatal immune response to multiple organisms of clear relevance to infant health. Our immediate goal is to use mouse models to study the interactions of the neonatal immune system with bacterial components that lead to long-lasting protection. The rationale behind our approach is that an understanding of the mechanisms controlling the plasticity of the neonatal repertoire will lead to new therapeutic or vaccination options for the treatment and prevention of infection by these organisms. Because mouse models provide unique opportunities for experimentation that cannot be performed in humans, we anticipate that this knowledge will help understand human infant responses to infection, aid in the development of more effective vaccine strategies, and help understand possible consequences of vaccine interference. These goals will be pursued by three aims: 1) to identify factors affecting the establishment of the B cell clonal repertoire to polysaccharides expressed by S. pneumoniae, S. pyogenes (GAS), S. agalactiae (GBS) and E. cloacae: 2) to identify phenotypic, subset distribution, and functional changes elicited in emerging B cells by exposure to these organisms: and 3) to isolate and determine the characteristics of mAbs derived from neonatally immunized adult mice that provide optimal protection to infection with these organisms. By choosing to study this multi-member panel, we will develop unique models in which we can study B cell clonal competition and other interactions during development. We have also developed a comprehensive panel of anti-idiotype antibodies and labeled antigens which permit us to accurately quantitate B cell clonal frequencies and trace by flow cytometry the development of single antigen-binding B cells in response to vaccination or after infection with our model organisms. In addition, we have constructed immunoglobulin transgenic mice with VH genes from hybridomas responding to the PS expressed by these organisms. Our findings are expected to have impact on the understanding of immune B cell memory development and its persistence throughout life. The likely future introduction of even more childhood vaccines makes it imperative that we better understand vaccine interference that may result from the effects of multiple vaccines, neonatal chronic infections, and co-infection on subsequent immune responses to further vaccination or infection. PUBLIC HEALTH RELEVANCE: Gram-negative enteric infections and Gram-positive organisms, including Streptococcus pneumoniae, Group A (GAS) and Group B (GBS) streptococci are leading causes of serious neonatal bacterial infections. The proposed research is relevant to public health because an understanding of the mechanisms controlling the plasticity of the neonatal repertoire will lead to new therapeutic or vaccination options for the treatment and prevention of infection by these organisms.