Molecular and Genetic Basis of Francisella Pathogenesis

图拉氏弗朗西斯杆菌是一种高度传染性的革兰氏阴性球菌，它能引起 人畜共患病图拉热症是一种A类药物。图拉氏丝虫存活并在体内复制 巨噬细胞，一种与毒力相关的表型，但对其了解甚少 其发病的分子基础。这个项目的长期目标是了解F. 图拉氏菌能破坏宿主的防御。这一目标将从根本上与这一目标相结合 计划项目，这是为了了解不同的细胞内病原体 结核分枝杆菌、单核细胞增多性李斯特菌和组织胞浆菌操纵 宿主的先天反应。我们假设巨噬细胞的比较分析 对这四种细胞内病原体的转录反应将是一种非常有效的手段 剖析和理解我们的微阵列实验结果。 我们推测图拉氏杆菌产生的基因产物可以改变人口贩运，或许 使最初的细菌噬菌体酸化，从而使细菌逃逸到 细胞质，在那里它可以生存和复制。这项提议的目标是使用分子 用遗传学方法揭示图拉氏杆菌细胞内生存所需的分子 和增长。在一种平行的方法中，DNA微阵列将被用来表征 巨噬细胞对图拉氏杆菌的反应，并验证我们的假设，即这种病原体将诱导 宿主基因表达的胞浆途径类似于单核细胞增多性李斯特氏菌。我们的具体目标是：1)鉴定在巨噬细胞内表达的图拉氏丝虫基因，并构建 巨噬细胞复制缺陷突变体；2)分析细胞内复制和 图拉氏丝虫的运输；以及3)巨噬细胞对F. 图拉尔人。这些研究将确定宿主细胞中由F. 图拉氏菌和其他与生物防御相关的关键细胞内病原体。

Francisella tularensis is a highly infectious gram-negative coccobacillus that causes the zoonosis tularemia and is a Category A agent. F. tularensis survives and replicates within macrophages, a phenotype that correlates with virulence, yet little is understood about the molecular basis of its pathogenesis. The long-term goal of this project is to understand how F. tularensis subverts host defenses. This aim will fundamentally interface with the goal of this Program Project, which is to understand how diverse intracellular pathogens such as Mycobacterium tuberculosis, Listeria monocytogenes and Histoplasma capsulatum manipulate host innate responses. We hypothesize that a comparative analysis of the macrophage transcriptional responses to these four intracellular pathogens will be a very powerful means of dissecting and understanding the results of our microarray experiments. We hypothesize that F. tularensis produces gene products that alter the trafficking and perhaps acidification of the initial bacterial phagosome, thereby allowing bacteria to escape into the cytoplasm where it can survive and replicate. The objective of this proposal is to use molecular genetic approaches to uncover F. tularensis molecules that are required for intracellular survival and growth. In a parallel approach, DNA microarrays will be used to characterize the macrophage response to F. tularensis and to test our hypothesis that this pathogen will induce a cytosolic pathway of host gene expression similar to L. monocytogenes. Our specific aims are to 1) identify F. tularensis genes that are expressed inside of macrophages and construct mutants defective in macrophage replication; 2) analyze the intracellular replication and trafficking of F. tularensis; and 3) characterize the macrophage transcriptional response to F. tularensis. These studies will identify regulatory circuits in host cells that are manipulated by F. tularensis and other key intracellular pathogens relevant to biodefense.