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

描述(申请人提供)：革兰氏阴性肠道感染和革兰氏阳性细菌，包括肺炎链球菌、A组(GAS)和B组(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。在人类和小鼠中，针对这些和类似生物体的早期B细胞抗体的产生对于防止感染和它们的血液传播至关重要。然而，适应性免疫系统在生命早期就受到了损害，人类婴儿对多糖(PS)的保护性抗体反应需要两年多的时间才能形成。我们的长期目标是对新生儿对多种明显与婴儿健康相关的生物的免疫反应进行仔细的受控研究。我们的近期目标是利用小鼠模型研究新生儿免疫系统与细菌成分的相互作用，从而实现持久的保护。我们的方法背后的基本原理是，了解控制新生儿发育过程的可塑性的机制将导致治疗和预防这些微生物感染的新的治疗或疫苗选择。由于小鼠模型为人类无法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。这些目标将有三个目标：1)确定影响建立肺炎链球菌、化脓性链球菌(GAS)、无乳链球菌(GBS)和阴沟肠杆菌表达的多糖的B细胞克隆库的因素：2)确定暴露于这些微生物后在新生B细胞中引起的表型、亚群分布和功能变化：3)分离和确定新生免疫成年小鼠来源的mAbs的特征，这些mAbb对这些微生物的感染提供最佳保护。通过选择研究这个多成员小组，我们将开发独特的模型，在其中我们可以研究B细胞克隆竞争和发育过程中的其他相互作用。我们还开发了一套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，并通过流式细胞仪跟踪单一抗原结合的B细胞在接种疫苗或感染我们的模式生物后的发展。此外，我们还从杂交瘤中构建了免疫球蛋白转基因小鼠，这些杂交瘤细胞对这些生物表达的PS做出反应。我们的发现有望对理解免疫B细胞记忆的发展及其在一生中的持久性产生影响。未来可能会推出更多的儿童疫苗，这使得我们必须更好地了解疫苗干扰，这可能是由于多种疫苗、新生儿慢性感染和合并感染对进一步接种疫苗或感染的后续免疫反应的影响造成的。 公共卫生相关性：革兰氏阴性肠道感染和革兰氏阳性细菌，包括肺炎链球菌、A组(GAS)和B组(GBS)链球菌是严重新生儿细菌感染的主要原因。这项拟议的研究与公共卫生有关，因为了解控制新生儿发育过程可塑性的机制将导致治疗和预防这些微生物感染的新的治疗或疫苗接种选择。

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.