Role of Rapid IFNg Secretion by CD*+ T cells in Clearance of Food Borne Listeria

描述（由申请人提供）：单核细胞增生李斯特菌（Lm）是一种重要的研究病原体，因为：1）它会引起重大公共卫生问题的危及生命的食源性感染，2）它是一种遗传上易处理的生物体，具有独特的细胞内生活方式，用作理解哺乳动物细胞细胞生物学的工具，3）全身（i. v.）绦虫病是一种高度可重复的感染，免疫学家经常使用它来研究细胞介导的免疫反应。由于缺乏一个小动物模型，密切模仿人类疾病，我们仍然知道很少Lm的口服传播，或者为什么先天易感性发展严重的胃肠炎，败血症，脑膜脑炎个体之间的差异。为了解决这一知识缺口，我们最近开发了一种新的口腔粘膜炎模型，使用喂食Lm污染食物的小鼠。这种自然喂养模型揭示了Lm在易感小鼠（BALB）与抗性小鼠（B6）中定殖肠道和全身传播的能力的明显差异。因此，我们现在可以第一次研究在胃中消化过程中存活的肠道适应性Lm如何能够定殖肠粘膜，并在无法快速清除肠道感染的易感小鼠中作为持续接种外周组织的病灶。由于绝大多数因腹泻住院的患者在某种程度上被认为是免疫受损的，因此长期以来一直认为保护性免疫应答对于将感染限制在耐药个体的轻度胃肠炎至关重要。我们的中心假设预测，这样的先天免疫机制之一是由记忆表型CD 8 + T细胞的子集快速分泌IFN？。我们假设T细胞衍生的IFN？可以快速启动B6小鼠的清除机制，并且BALB小鼠中CD 8 + T细胞活化的延迟允许Lm以指数方式复制并扩散到全身组织。本申请有三个具体目的：（1）鉴定结肠中支持Lm生长的细胞类型，从而作为保护性先天免疫应答的靶点;（2）鉴定摄取Lm后快速分泌IFN？的CD 8 + T细胞的特定亚群，并显示这种T细胞衍生的IFN？可以快速限制结肠中Lm的细胞内生长;（3）鉴定IFN？- 依赖性先天免疫机制，其促进Lm从肠道传播后在外周组织中的快速清除。本申请中的关键策略将是使用独特的过继转移系统，其中将来自应答小鼠的T细胞注射到MHC匹配的非应答小鼠中。这种强大的方法将使我们能够特异性地分离由CD 8 + T细胞快速产生的IFN的功能，同时保持所有其他先天免疫机制的完整性。拟议研究的预期成果是：[1]对食源性Lm的致病生活方式的重要新见解，[2]更好地理解决定宿主对细胞内细菌病原体的抗性/易感性的先天免疫机制。

DESCRIPTION (provided by applicant): Listeria monocytogenes (Lm) is important an important pathogen to study because: 1) it causes life threatening food borne infections of significant public health concern, 2) it is a genetically tractable organism with a unique intracellular lifestyle used as a tool for understanding the cell biology of mammalian cells, and 3 systemic (i.v.) listeriosis is a highly reproducible infection frequently used by immunologists to study cell- mediated immune responses. Due to the lack of a small animal model that closely mimics human disease, we still know very little about oral transmission of Lm, or why the innate susceptibility to developing severe gastroenteritis, sepsis, and meningoencephalitis varies among individuals. To address this knowledge gap, we recently developed a new model of oral listeriosis using mice fed Lm-contaminated food. This natural feeding model revealed clear differences in the ability of Lm to colonize the gut and spread systemically in susceptible (BALB) vs. resistant (B6) mice. Thus, for the first time, we can now study how gut-adapted Lm that survive digestive processes in the stomach are able to colonize the intestinal mucosa and serve as a nidus for continual seeding of peripheral tissues in susceptible mice unable to quickly clear the gut infection. Since the vast majority of patients hospitalized with listeriosis can be considered immune compromised in some way, it has long been thought that protective immune responses were critical for limiting the infection to a mild gastroenteritis in resistant individuas. Our central hypothesis predicts that one such innate immune mechanism is the rapid secretion of IFN¿ by a subset of memory phenotype CD8+ T cells. We postulate that T cell-derived IFN¿ can rapidly initiate clearance mechanisms in B6 mice and that the delay in activation of CD8+ T cells in BALB mice allows Lm to replicate exponentially and spread to systemic tissues. This application has three specific aims: (1) to identify the cell types in the colon that support Lm growth and thus, serve as the targets of protective innate immune responses; (2) to identify the specific subsets of CD8+ T cells that rapidly secrete IFN¿ after ingestion of Lm and show that this T cell-derived IFN¿ can rapidly limit the intracellular growth of Lm in the colon; (3) to idenify IFN¿-dependent innate immune mechanisms that promote rapid clearance of Lm in peripheral tissues after dissemination from the gut. A key strategy in this application will be the use of a unique adoptive transfer system wherein T cells from a responsive mouse are injected into a MHC-matched non-responsive mouse. This powerful approach will allow us to specifically isolate the function of IFN¿ rapidly produced by CD8+ T cells while leaving all other innate immune mechanisms intact. The expected outcomes of the proposed studies are: [1] significant new insights into the pathogenic life style of food borne Lm, and [2] a better understanding of the innate immune mechanisms that determine host resistance/susceptibility to intracellular bacterial pathogens.