Molecular pathogenesis of Francisella Tularensis

描述(申请人提供)：致命疾病图拉热症的病原体，图拉氏方济氏菌(Ft)，是一种革兰氏阴性高度传染性的胞内细菌，被归类为A类精选生物恐怖主义制剂。巨噬细胞内的Ft复制对于疾病的表现是必不可少的。令人惊讶的是，关于这种多功能和极具毒性的病原体致病的分子和细胞方面的知识相对匮乏。我们的初步数据表明，在进入巨噬细胞后，含Ft的吞噬小体(FCP)可以避开溶酶体融合。生物体在感染后2-12小时从吞噬小体逃逸到细胞质中。我们的假设是，Ft进入巨噬细胞的特定模式允许有机体通过特定的输出细菌效应物调节其吞噬小体的生物发生，进入不与溶酶体融合的利基，并允许有机体随后逃逸到细胞质中，在那里进行复制。为了验证这一假说，我们的具体目标是：1.剖析图拉夫酵母细胞内的细胞生物学，以及在非酸化的晚期内吞噬体样阶段阻止吞噬小体生物发生的独特机制。鉴定在阻止吞噬小体生物发生和逃逸到细胞质中存在缺陷的突变体。确定参与阻止吞噬小体生物生成和逃逸到细胞质中的细菌因子。意义：A类精选生物恐怖分子Ft的发病机制是细胞内细菌病原体中研究和了解最少的之一。了解这种生物如何利用巨噬细胞进行增殖和疾病表现是我们了解图拉热症的基础。参与利用巨噬细胞的细菌效应器是潜在的治疗目标和潜在的疫苗候选。

DESCRIPTION (provided by applicant): The causative agent of the fatal disease Tularemia, Francisella tularensis (Ft), is a gram negative highly infectious intracellular bacterium, that is classified as a Category A Select Bioterrorism Agent. Intracellular replication of Ft within macrophages is essential for disease manifestation. It is rather astonishing the relative paucity of knowledge about the molecular and cellular aspects of pathogenesis of this versatile and extremely virulent pathogen. Our preliminary data indicate that upon entry into macrophages, Ft-containing phagosome (FCP) evades lysosomal fusion. The organism escapes from the phagosome into the cytoplasm by 2-12h post-infection. Our hypothesis is that specific modes of entry of Ft into macrophages allow the organism to modulate biogenesis of its phagosome, by specific exported bacterial effectors, into a niche that does not fuse to the lysosomes and allow subsequent escape of the organism into the cytoplasm, where it replicates. To test this hypothesis, our specific aims are: I. To dissect the cell biology of intracellular F. tularensis and the unique mechanisms that halt phagosome biogenesis at a non-acidified late endosome-like stage. II. To identify mutants defective in arresting phagosome biogenesis and escape into the cytoplasm. III. To characterize the bacterial factors involved in arresting phagosome biogensis and escape into the cytoplasm. Significance: Pathogenesis of the Category A Select Bioterrorism Agent Ft is one of the least studied and understood among intracellular bacterial pathogens. Understanding how this organism exploits macrophages for proliferation and disease manifestation is fundamental to our knowledge of tularemia. The bacterial effectors involved in exploiting the macrophage are potential targets for treatment as well as potential vaccine candidates.