The role of Salmonella protease PgtE in evading host immune responses

项目摘要 细菌感染仍然是全球发病率和死亡率的主要原因，也是一个严重的健康问题。 由于抗生素耐药性的增加和疫苗的有限。非伤寒沙门氏菌(NTS)血清型，如 肠沙门氏菌伤寒沙门氏菌(STM)是引起炎症性腹泻的主要原因 健康的个体，引起感染，通常局限于肠道。在免疫功能受损的人群中 无论是个人、儿童还是老年人，STM都可能导致一种潜在的致命性菌血症，需要抗生素治疗。 在防止细菌从胃肠道传播到肠道的固有宿主防御中起关键作用 血流是抗菌肽、补体系统蛋白和吞噬细胞，包括 巨噬细胞和中性粒细胞。STM致病菌株能颠覆吞噬酶小体存活 在巨噬细胞内，自噬系统成为杀死细胞内的关键步骤 扫描隧道显微镜。PgtE是一种STM外膜蛋白酶，此前已被描述为可切割十几种哺乳动物 体外的蛋白质底物，包括补体蛋白C3，但这些活性只在 外膜有缺陷的无毒突变菌株。近年来，一个新出现的分支 侵袭性STM是撒哈拉以南非洲菌血症流行的原因，有几项研究表明 提示PgtE的表达增加是一种重要的毒力机制，尽管机制 仍然不为人知。我们的初步研究表明，PgtE在感染过程中发挥着重要作用 最初的粘膜定植，并处于全身期的毒力STM。我们的中心假设是，在 STM已经被吞噬，STM利用PgtE保护被破坏的外膜免受抗菌剂的伤害 多肽、补体和自噬杀死，从而促进其在宿主中的生存。在目标1中，我将确定 PgtE在STM吞噬后逃避IL-22介导的肠上皮防御中的作用 管腔。在目标2中，我将确定PgtE如何颠覆补体成分C3信号和巨噬细胞 自噬杀戮。这项工作将为病原体如何利用蛋白酶逃避免疫提供一个框架。 具有潜在的新治疗靶点的系统。

Project Summary Bacterial infections remain a leading cause of morbidity and mortality worldwide and a critical health issue due to increasing antibiotic resistance and limited vaccines. Non-typhoidal Salmonella (NTS) serovars such as Salmonella enterica serovar Typhimurium (STm) are a leading cause of inflammatory diarrhea in otherwise healthy individuals, causing infections that are usually localized to the gut. Among immunocompromised individuals, children, and elderly, STm can cause a potentially lethal bacteremia that requires antibiotic treatment. Pivotal to innate host defense in preventing the spread of bacteria from the gastrointestinal tract to the bloodstream are antimicrobial peptides, complement system proteins, and phagocytic cells including macrophages and neutrophils. Pathogenic strains of STm can subvert the phagolysosome to survive intracellularly in macrophages, whereupon the autophagy system emerges as a critical step for killing intracellular STm. PgtE, a STm outer membrane protease, has been previously described to cleave over a dozen mammalian protein substrates in vitro, including complement protein C3, but these activities have only been observed with avirulent mutant strains possessing a defective outer membrane. In recent years, a newly emergent clade of invasive STm has been responsible for an epidemic of bacteremia in sub-Saharan Africa, with several studies suggesting an increased expression of PgtE as an important virulence mechanism although the mechanism remains unknown. Our preliminary studies suggest that PgtE plays an important role during infection in both the initial mucosal colonization and in the systemic phase with a virulent STm. Our central hypothesis is that after STm has been phagocytosed, STm utilizes PgtE to protect the disrupted outer membrane from antimicrobial peptides, complement, and autophagy killing, thereby promoting its survival in the host. In Aim 1, I will determine the role of PgtE in enabling STm to evade IL-22-mediated gut epithelial defenses after STm is phagocytosed in the lumen. In Aim 2, I will determine how PgtE subverts complement component C3 signaling and macrophage autophagic killing. This work will provide a framework on how pathogens utilize proteases to evade the immune system with potential novel therapeutic targets.