Pyroptotic Macrophages Traps Against Shigella Infection

志贺氏菌属是主要的肠道病原体，引起急性腹泻和细菌性痢疾，在世界范围内导致严重的死亡和发病率。然而，目前还没有获得许可的疫苗来预防志贺氏菌病。志贺氏菌的毒力需要一个T3SS和至少30个分泌的效应器，这些效应器通常在功能上是多余的，但需要入侵宿主细胞，维持复制生态位，最大限度地减少警报信号，并促进定植。我们先前通过Caspase-1炎性小体在巨噬细胞中检测到福氏志贺氏菌T3SS活性，从而导致下垂。在最近的小鼠志贺氏菌病模型中，炎症小体的作用仅集中在肠道上皮细胞(IECS)。然而，人们普遍认为志贺氏菌最初感染巨噬细胞，并利用嗜热细胞死亡的优势退出细胞，随后感染IECS。另一方面，巨噬细胞松弛症已知会产生气孔诱导的陷阱(PITS)，捕获并中和细胞内的细菌病原体。由于巨噬细胞下垂被认为在志贺氏菌感染过程中起着二分性的作用，我们建议研究巨噬细胞炎症体与福氏志贺菌之间的相互作用。我们提出了两个具体目标：在Aim1中，我们将研究坑中的嗜热巨噬细胞如何捕获细胞内细菌。在目标2中，我们将在体内和体外确定嗜热巨噬细胞和嗜热性巨噬细胞在福氏志贺氏菌感染过程中的作用。我们希望通过研究巨噬细胞嗜热抑制志贺氏菌感染的作用，对更好地了解志贺氏菌感染过程中的免疫和疾病病理机制具有重要意义，从而为开发更安全、更有效的新型疫苗奠定基础。

Shigella spp. are major enteric pathogens, causing acute diarrhea and bacillary dysentery leading to severe mortality and morbidity worldwide. Yet, there is no licensed vaccine to prevent shigellosis. Shigella virulence requires a T3SS and at least 30 secreted effectors that are often functionally redundant, yet required to invade host cells, maintain a replicative niche, minimize alarm signals, and promote colonization. We previously showed that S. flexneri T3SS activity is detected in macrophages by Caspase-1 inflammasomes, resulting in pyroptosis. In the recent mouse shigellosis model, the role of the inflammasome is only focused on gut intestinal epithelial cells (IECs). However, it is generally believed that Shigella initially infect macrophages and takes advantage of pyroptotic cell death to exit the cells and subsequently infect IECs. On the other hand, macrophage pyroptosis is known to generate pore-induced traps (PITs), trapping, and neutralizing intracellular bacterial pathogens. Since macrophages pyroptosis is considered to play dichotomous roles during Shigella infection, we propose to investigate the interaction between macrophages' inflammasomes and S. flexneri. We propose two specific Aims: In Aim1, we will investigate how pyroptotic macrophages from PITs trap intracellular bacteria. In Aim 2. We will define the role of pyroptotic macrophages and PITs during S. flexneri infection in vitro and in vivo. We hope that examining the role of macrophages pyroptosis against S. flexneri infection, will be highly significant and relevant for better understanding immunity and disease pathologies during Shigella infection and thereby providing the basis for developing novel safer, and more effective vaccines.