Innate Immune Response Following Bacterial Translocation in Early Life

项目摘要 新生儿败血症是新生儿因血液感染而死亡的主要原因。 由多种细菌病原体引起。尽管卫生习惯有所增加，但洛杉矶的发病率 在过去的40年里，由于共生物种导致的病例增加，出现了矛盾的增长 从正常的皮肤和肠道菌群中分离出来。有趣的是，在洛杉矶的很大一部分地区，病原体可以 在发病前被发现是新生儿肠道微生物群落的居民，但目前尚不清楚是如何 细菌病原体从肠道转移以及新生儿免疫系统最初如何对肠道作出反应 始发病原体易位。在我的初步研究中，我已经证明了肠道细菌可以 通过形成杯状细胞相关抗原通道(GAP)的杯状细胞移位上皮，并要求 CX3CR1单核巨噬细胞(MNPs)进入循环。细菌前一天的移位 母乳中母体提供的蛋白质抑制了LIFE 10的活性。1的异步性杂交(ACF) 出生一天的幼崽出生前10天产下一窝幼崽的结果是DOL1-1之间的细菌易位 10美元。共生细菌和引起临床败血症的病原菌都可以移位和获得 ACF小鼠的全身生理通路。然而，只有被灌胃了致病性大肠杆菌的小鼠死亡。 致病性大肠杆菌易位后的败血症样疾病，尽管在以下情况下细菌负荷相似 与感染共生大肠杆菌的ACF小鼠相比。感染致病性大肠杆菌的ACF小鼠，发展为炎症性 CX3CR1+MNPs产生的全身性IL6增加， 提示了一种通过粘液对易位共生体和病原体做出差异反应的机制 免疫系统。人们认为新生儿的反应是一种不成熟和无知，缺乏 由于免疫抑制状态，在免疫系统完全恢复之前，能够正确对抗细菌病原体的能力 成熟了。然而，我的初步数据显示，复杂的先天免疫系统能够感知不同的 细菌的差异，并感知潜在的致病威胁。我的假设是基于最近的临床发现 新生儿特有的细胞因子特征，包括血清IL-6的升高，是这种反应是由 肠道中遇到移位细菌的MNP细胞。这个项目将利用动物 模型、脓毒症病原体和各种基于流式细胞术的分析来探索先天免疫 肠道移位后对败血症病原体的反应。在完成这项工作后 项目中，我将了解病原体易位后的先天免疫反应，定义动力学 了解CX3CR1 MNPs如何促进细菌的系统性传播，以及这些过程如何可能 与共生易位后的反应不同。此外，这项工作将允许 开发针对新生儿败血症病例的干预措施和预防性治疗方法 了解新生儿对肠源性细菌病原体反应的独特方面。

Project Summary Neonatal sepsis is a leading cause of death in newly born babies resulting from a bloodstream infection caused by a variety of bacterial pathogens. Despite increased hygiene practices, LOS incidence has paradoxically increased in the past forty years due to an increase in cases resulting from commensal species from the of the normal skin and intestinal flora. Intriguingly, in a substantial portion of LOS, the pathogen can be found as a resident of the neonatal gut microbial community prior to disease, yet it remains unclear how bacterial pathogens translocate from the intestine and how the neonatal immune system initially reacts to gut originating pathogen translocation. In my preliminary studies, I have shown gut residing bacteria can translocate the epithelium via goblet cells forming goblet cell associated antigen passages (GAPs) and require CX3CR1 mononuclear phagocytes (MNPs) to gain access to the circulation. Bacterial translocation prior to day of life 10 is inhibited by maternally supplied proteins in breastmilk. Asynchronous cross-fostering (ACF) of 1 day old pups to dams having delivered a litter 10 days prior results in bacterial translocation between DOL1- DOL10. Both commensal bacteria and pathogenic clinical sepsis-causing isolates could translocate and gain systemic access physiologically In ACF mice. However, only mice gavaged with pathogenic E.coli succumbed to a sepsis-like disease following translocation of pathogenic E.coli, despite similar bacteria burden when compared to ACF mice with commensal E. coli. ACF mice with pathogenic E.coli, developed an inflammatory signature in the intestinal lamina propria and had increased systemic IL6, produced by CX3CR1+ MNPs, suggesting a mechanism to differentially respond to translocation commensals and pathogens by the mucsoal immune system. It has been assumed the neonatal response is one of immaturity and ignorance that lacks the ability to properly fight bacterial pathogens due to a state of immunosuppression until the immune system fully matures. However, my preliminary data indicates a sophisticated innate immune system able to sense distinct bacterial differences and perceive potential pathogenic threats. My hypothesis based on recent clinical findings of a cytokine signature unique to neonates including increased serum IL-6 is that this response is initiated by the MNP cells within the intestine that encounter the translocating bacteria. This project will utilize animal models, sepsis pathogens, and a variety of flow cytometry-based assays to explore the innate immune response to sepsis pathogens following translocation from the intestine. Following the completion of this project, I will understand the innate immune response following pathogen translocation, defining the dynamics of how CX3CR1 MNPs may contribute to systemic dissemination of bacteria, and how these processes may differ from the response following commensal translocation. Additionally, this work will allow for the development of interventions and preventative therapeutics specific for neonatal sepsis cases, by understanding the unique aspects of the neonatal response to gut originating bacterial pathogens.