Defining mechanisms of Casp1/11-independent death triggered by clinical Salmonella Enteritidis

项目摘要 鼠伤寒沙门氏菌感染巨噬细胞后， 死亡被称为pyroptosis消除沙门氏菌的复制生态位，并促进炎症反应， IL-1细胞因子的释放。虽然STm SPI-1活性触发快速的Casp 1依赖性细胞凋亡，但它仍然可以 在不存在Casp 1的情况下诱导Caspase-8（Casp-8）依赖性细胞死亡。然而，在没有SPI-1的情况下， STm介导的侵袭和早期细胞凋亡，在巨噬细胞内建立了复制区室， 触发晚期Casp 1/11依赖性细胞死亡。有趣的是，我们的初步研究首次表明， 与先前研究的STm菌株相比，临床S.肠道血清型分离株，包括S. 肠杆菌（SE），获自宾夕法尼亚大学兽医分离株的菌株库，和DT 104， 最近出现的STm菌株负责亚热带地区的侵袭性非伤寒沙门氏菌（iNTS）疾病， 撒哈拉非洲，触发Casp 1/11非依赖性细胞死亡，这表明先天免疫反应的临床 肠道沙门氏菌与常用的实验室菌株诱导的沙门氏菌显著不同。SE是领先的 沙门氏菌病的原因在美国，但我们目前缺乏机械知识，它如何相互作用， 先天免疫系统该提案的中心目标是确定宿主和沙门氏菌因素 负责晚期Casp 1/11非依赖性死亡，这可能有助于侵袭性疾病的发病机制 由iNTS分离株引起。我们发现，Casp 8是负责Casp 1/11非依赖性细胞死亡触发 通过SE感染，并且这种细胞死亡需要功能性SPI-2 T3 SS。总之，我们的研究激发了 假设沙门氏菌肠道血清型具有独特的毒力因子， 在没有Casp 1的情况下细胞死亡。我们将在本提案中以两个目标来检验这一假设，这两个目标将：（1）定义 诱导响应SE的Casp 8依赖性细胞死亡所需的宿主信号传导组分，和（2） 机械地定义诱导这种SPI-2和Casp 8依赖性细胞所需的SE特异性细菌因子 死亡定义这些因子将为研究较少的病毒的毒力和宿主相互作用提供新的见解。 沙门氏菌血清型是导致美国和欧洲大部分沙门氏菌感染的原因。

Project Summary Macrophages infected by Salmonella enterica serovar Typhimurium (STm) undergo a lytic inflammatory cell death known as pyroptosis to eliminate Salmonella’s replicative niche and promote inflammatory responses via release of IL-1 cytokines. While STm SPI-1 activity triggers a rapid Casp1-dependent pyroptosis, it can still induce Caspase-8 (Casp-8)-dependent cell death in the absence of Casp1. However, in the absence of SPI-1- mediated invasion and early pyroptosis, STm establishes a replicative compartment within macrophages and triggers a late Casp1/11-dependent cell death. Intriguingly, our preliminary studies show for the first time that in contrast to STm strains that have previously been studied, clinical S. enterica serovar isolates, including S. Enteritidis (SE), obtained from a strain bank of veterinary isolates at the University of Pennsylvania, and DT104, the recently-emerged STm strain responsible for invasive non-Typhoidal Salmonella (iNTS) disease in sub- Saharan Africa, trigger Casp1/11-independent cell death, suggesting that the innate immune response to clinical Salmonella enterica differs significantly from that induced by commonly used laboratory strains. SE is a leading cause of Salmonellosis in the United States, yet we currently lack mechanistic knowledge of how it interacts with the innate immune system. The central goal of this proposal is to define the host and Salmonella factors responsible for late Casp1/11-independent death, which may contribute to the pathogenesis of invasive disease caused by iNTS isolates. We find that Casp8 is responsible for the Casp1/11-independent cell death triggered by SE infection, and that this cell death requires a functional SPI-2 T3SS. Together, our studies provoke the hypothesis that Salmonella serovar Enteritidis possesses unique virulence factors that trigger Casp8-mediated cell death in the absence of Casp1. We will test this hypothesis in this proposal in two Aims that will (1) Define the host signaling components required to induce Casp8-dependent cell death in response to SE, and (2) Mechanistically define the SE-specific bacterial factors required to induce this SPI-2- and Casp8-dependent cell death. Defining such factors will provide new insight into the virulence and host interactions of less well-studied Salmonella serovars that are responsible for a large proportion of Salmonella infections in the US and Europe.