Using microbially-experienced mice to study the innate immune response in sepsis

脓毒症是一种威胁生命的器官功能障碍，由宿主对感染的反应失调引起。早些时候 脓毒症阶段的标志是由促炎细胞因子(即IL-1β、IL-6、干扰素γ、 和肿瘤坏死因子)。在人类身上进行假设驱动的研究的困难证明有必要在临床上- 相关的实验性脓毒症模型。研究多因素方差的模型有很多 败血症的病理生理学，在败血症研究中使用的主要哺乳动物生物是小鼠(Mus 肌肉)。虽然关于发生的错综复杂的变化的知识有了巨大的扩展 在脓毒症事件后的免疫系统内，到目前为止发表的几乎所有临床前脓毒症研究 依赖于在无特定病原体(SPF)条件下饲养的小鼠的使用。环境病原体 暴露是人类基础生物学和实验室小鼠生物学之间的一个重要区别，这必须是 在使用小鼠评估免疫系统健康状况时考虑。人类对这两种环境都有天然的接触 从出生起每天都有共生和致病的微生物，成年人类的免疫系统一直 根据所经历的每一次感染和疫苗接种进行培训和塑造。而实验室小鼠的SPF外壳有 有助于提高实验的重复性，同时也进一步疏远了小鼠 作为人类的模型，很大程度上是因为SPF小鼠在有限的微生物暴露下生活。 这一建议利用了一种新的小鼠模型，该模型模拟了人类生物学的一个关键方面-暴露于 多个持续和已解决的感染训练免疫系统对新病原体做出强有力的反应。 我们的中心假设认为，败血症患者的急性反应和死亡率加剧 (COH)小鼠源于腹膜常驻MF的过度活动和器官功能障碍/损害增加 源于中性粒细胞反应升高-很大程度上是因为这些细胞的容量增加 吞噬细胞通过增加模式识别受体的表达来识别感染。我们还假设 通过共生的微生物暴露增加了肠道微生物群的“致病性”，这也有助于 免疫系统增加的反应。在目标1中，我们将定义TLR4信令的重要性 在脓毒症期间，腹膜内常驻MF在调节急性免疫反应的大小方面具有重要作用。 目标2中的实验将确定中性粒细胞在导致器官功能障碍/损害和 败血症CoH小鼠的死亡率。最后，目标3中的研究将确定肠道微生物群如何变化为 重症监护中脓毒症患者的部分常规治疗，包括广谱抗生素和 肠内营养中断会导致微生物区系功能障碍，从而增加晚期脓毒症死亡率。什么时候 综合考虑本提案中的概念、初步数据和拟议的研究，本项目将 展示使用CoH小鼠更好地询问脓毒症的免疫学分支的力量。

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Early stages of sepsis are marked by hyperinflammation driven by proinflammatory cytokines (i.e., IL-1β, IL-6, IFNγ, and TNF). The difficulty in performing hypothesis-driven research in humans justifies the need for a clinically- relevant, experimental sepsis model. A number of models are commonly used to study the multifactorial pathophysiology of sepsis, and the dominant mammalian organism used in sepsis research is the mouse (Mus musculus). While there has been a vast expansion in knowledge regarding the intricate changes that occur within the immune system following a septic event, virtually all preclinical sepsis research published to date has relied on the use of mice housed under specific pathogen-free (SPF) conditions. Environmental pathogen exposure is one important difference between basic human and laboratory mouse biology that must be considered when using mice to evaluate immune system fitness. Humans are naturally exposed to both commensal and pathogenic microbes daily from birth, and the immune system of adult humans has been trained and shaped by each infection and vaccination experienced. While SPF housing of laboratory mice has been instrumental in increasing experimental reproducibility, it has simultaneously further distanced the mouse as a model from humans largely because SPF mice live their lives with limited microbial exposure. This proposal leverages a novel mouse model that mimics a critical aspect of human biology – exposure to multiple ongoing and resolved infections trains the immune system for robust responses to new pathogens. Our central hypothesis holds that the exacerbated acute response and mortality seen in septic cohoused (CoH) mice stems from hyperactivity by peritoneal resident Mf and increased organ dysfunction/damage stemming from elevated neutrophil responses – largely because of an augmented capacity of these phagocytes to recognize infection via increased pattern recognition receptor expression. We also posit microbial exposure via cohousing increases the ‘pathogenicity’ of the gut microbiome, which also contributes to the increased response by the immune system. In Aim 1, we will define the importance of TLR4 signaling within peritoneal resident Mf in regulating the magnitude of the acute immune response during sepsis. Experiments in Aim 2 will define the role played by neutrophils leading to the organ dysfunction/damage and mortality in septic CoH mice. Finally, studies in Aim 3 will determine how changes in the gut microbiome as part of the routine treatments for sepsis patients in critical care, including broad-spectrum antibiotics and interruption of enteral nutrition, lead to the dysfunction of microbiota that increases late sepsis mortality. When the concepts, preliminary data, and proposed studies in this proposal are considered in sum, this project will showcase the power of using CoH mice to better interrogate the immunological ramifications of sepsis.