Defining mechanisms underlying Listeria monocytogenes cardiac infections

描述（由申请人提供）：单核增生李斯特菌（Lm）是一种革兰氏阳性，食源性兼性细胞内细菌病原体，感染人类并在细菌跨肠屏障易位后引起疾病。虽然健康人通常表现出轻微的疾病，如肠胃炎，但免疫功能受损的个体以及老年患者往往患有更严重的疾病，包括脑膜脑炎和败血症。侵袭性Lm感染的一个重要但文献记载较少的后遗症涉及心脏；据估计，这种类型的感染发生在侵袭性疾病患者中至少%至10%。最近公布的数据表明，Lm菌株的重要亚群具有靶向和侵入心脏细胞的能力；这是一项具有重要临床意义的新发现。本提案中概述的实验将验证这样的假设，即心脏侵入性Lm菌株已经发展出新的机制和/或表达新的或改变的细菌因子，使它们能够在心脏组织中复制。这些研究将为Lm感染引起的心肌炎的发病机制和成熟提供详细的了解，并将阐明导致特定宿主组织趋向性的细菌因素。目的1将在动物感染模型中解释Lm心侵性菌株的病理。使用体内生物发光成像技术监测小鼠的细菌感染，以确定心脏感染的进展以及细菌在其他身体部位定植的可能性。实验还将包括靶组织的组织学检查，以表征宿主免疫细胞浸润的部位，以及使用免疫自旋捕获技术来明确识别由于对Lm感染的炎症反应而发生的细胞损伤。目的2将侧重于与侵袭性心脏感染相关的细菌因素的功能表征。遗传和细胞方法将被用来确定相对于其他入侵增强心脏入侵的Lm因素

DESCRIPTION (provided by applicant): Listeria monocytogenes (Lm) is a gram-positive, food-borne facultative intracellular bacterial pathogen that infects humans and causes disease following bacterial translocation across the intestinal barrier. While healthy individuals usually exhibit mild forms of disease such as gastroenteritis, individuals who are immune-compromised as well as elderly patients often suffer more severe forms of illness that include meningoencephalitis and septicemia. A significant but much less well-documented sequelae of invasive Lm infections involve the heart; this type of infection is estimated to occur in at least % to 10% of those with invasive disease. Recently published data indicates that significant subpopulations of Lm strains have the capacity to target and invade cardiac cells; this is a new finding with important clinical implications. Experiments outlined within this proposal will test te hypothesize that cardioinvasive Lm strains have developed novel mechanisms and/or express novel or altered bacterial factors that enable them to replicate within cardiac tissues. These studies will provide a detailed understanding of the pathogenesis and maturation of myocarditis resulting from Lm infection, and will clarify bacterial factors that contribute to specific host tisue tropisms. Aim 1 will decipher the pathology of Lm cardioinvasive strains in animal infection models. Bacterial infections will be monitored in mice using in vivo bioluminescence imagining to determine the progression of cardiac infection as well as the potential for bacterial colonization at other body sites. Experiments will also include the histological examination of target tissues to characterize sites of host immune cell infiltration as well as the use of immuno-spin capture technology to definitively identify cellular damage that occurs as a result of the hos inflammatory response to Lm infection. Aim 2 will focus on the functional characterization of bacterial factors associated with invasive cardiac infections. Genetic and cellular approaches will be used to identify Lm factors that enhance cardiac invasion relative to the invasion of other cell types. The ultimate goal of these studies will be to establish and functionally characterize a cardiac model of infection for Lm and to determine the bacterial factors that contribute to the enhanced ability of selected Lm strains to invade and destroy cardiac tissue. This information will be useful for the early identification of Lm outbreak strains that pose increased risk for patient heart infections. Finally, the experiments outlined in this proposal will provide important insight into the mechanisms that establish bacterial tropism for specific host tissues and in addition will identify in vivo cellular targets of oxidative damage resulting from host inflammator responses to infection.