Characterization of vacuole escape in Shigella infection

福氏志贺菌是人类细菌性痢疾的病原体。在低谷- 在收入国家，恶劣的卫生条件每年造成约2.7亿志贺氏菌病病例， 其中至少有25万人死亡。在高收入国家，志贺氏菌病通常与 前往高风险地区(拉丁美洲、亚洲和非洲)。该病的特点是严重出血。 腹泻和结肠粘膜的严重破坏。福氏志贺氏菌通过粪便-口腔途径传播 传染性极强，发病率在90%以上，感染量低至100-1000个细菌 每个人，正如人类志愿者研究所确定的那样。福氏志贺氏菌是一种侵入细胞内的病原体 人类结肠中的上皮细胞。细菌通过注射细菌效应蛋白来触发它们自己的进入。 通过它们的3型分泌系统(T3SS)，导致细菌摄取到初级细胞空泡中。这个 病原体迅速从初级液泡中逃逸，进入细胞质隔间。在细胞质中， 细菌招募肌动蛋白细胞骨架的成分，并在细菌极处进行肌动蛋白聚合，推动 病原体遍布整个细胞。当可移动的细菌到达细胞与细胞的接触时，它们形成膜突起， 投射到相邻的单元格。形成的突起的溶解导致双层膜的形成 邻近细胞中的空泡(DMV)，病原体从这些空泡中逃逸，从而实现细胞间的传播。这个 这一传播过程在福氏志贺氏菌致病机制中的重要性已初步通过 在非人类灵长类动物或人类志愿者中进行的研究，最近由我们小组在 细菌性痢疾的幼兔模型。虽然基于肌动蛋白的运动现在已经被很好地理解了，但 支持细胞间传播的机制尚不清楚。我们的小组以前已经证明了 细菌传播中的T3SS。此外，我们最近发现T3SS效应蛋白IcsB是一种 细胞间传播过程中DMV逃逸的关键决定因素。在这里，我们建议探索IcsB如何做出贡献 上皮细胞中DMV逃逸(Aim1)及IcsB介导的DMV逃逸在鼠疫发病机制中的作用 Vivo(AIM2)。

The intracellular pathogen Shigella flexneri is the causative agent of bacillary dysentery in humans. In low- income countries, poor sanitation is responsible for approximately 270 million cases of shigellosis annually, with at least 250,000 of these resulting in death. In high-income countries, shigellosis is typically associated with travel to high-risk regions (Latin America, Asia and Africa). The disease is characterized by severe bloody diarrhea and dramatic destruction of the colonic mucosa. S. flexneri is transmitted via the fecal-oral route and is extremely contagious, with a rate of attack above 90% with an infectious dose as low as 100-1000 bacteria per individual, as determined in human volunteer studies. S. flexneri is an intracellular pathogen that invades epithelial cells in the human colon. The bacteria trigger their own entry by injecting bacterial effector proteins through their type 3 secretion system (T3SS), leading to bacterial uptake into primary cellular vacuoles. The pathogen promptly escapes from primary vacuoles to gain access to the cytosolic compartment. In the cytosol, bacteria recruit components of the actin cytoskeleton and actin polymerization at the bacterial pole propel the pathogen throughout the cell. As motile bacteria reach cell-cell contacts, they form membrane protrusions that project into adjacent cells. The resolution of the formed protrusions leads to formation of double-membrane vacuoles (DMVs) in adjacent cells, from which the pathogens escape, thereby achieving cell-to-cell spread. The importance of this dissemination process in S. flexneri pathogenesis has been initially established through studies conducted in non-human primates or in human volunteers and recently demonstrated by our group in an infant rabbit model of bacillary dysentery. Although actin-based motility is now fairly well understood, the mechanisms supporting cell-to-cell spread are unclear. Our group has previously shown the importance of the T3SS in bacterial dissemination. Moreover, we have recently identified the T3SS effector protein IcsB as a critical determinant of DMV escape during cell-to-cell spread. Here we propose to explore how IcsB contribute to DMV escape in epithelial cells (Aim1) and how IcsB-mediated DMV escape contributes to pathogenesis in vivo (Aim2).