Inhibition of Salmonella intracelullar replication by interferon-stimulated genes

干扰素刺激基因抑制沙门氏菌胞内复制

• 批准号: 2060460
• 金额: --
• 依托单位: King's College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2060460
• 关键词: Inhibition; Salmonella; intracelullar; replication; interferon

Salmonella enterica serovar Typhimurium is a leading cause of food- and water-borne gastroenteritis worldwide(1). Infections are usually self-limiting but can pose a significant threat to infants and the immunocompromised, with non-typhoidal Salmonella causing approximately 155,000 deaths globally each year(2, 3). Once consumed it is phagocytosed by M cells and dendritic cells and can invade non-phagocytic cells including epithelial cells(4, 5). After breaching the epithelial barrier it multiplies within epithelial cells and macrophages, and bacteria can invade other cells from the basolateral side(6). The ability to invade non-phagocytic cells requires the type three secretion system (T3SS) encoded on Salmonella pathogenicity island 1 (Spi1). Effectors cooperate to promote the completion of a membrane-bound macropinosome, also known as the Salmonella containing vacuole (SCV)(6-8). Within a few hours, nutrient depletion and a decrease in pH lead to the upregulation of expression of another T3SS, Spi2, which confers the ability of S. Typhimurium to survive within the SCV(9-13). Effector proteins of both T3SSs are known to interfere with host signalling and recent work by the Odendall lab has shown that expression of effectors of T3SSs encoded by another enteric pathogen, Shigella, blocks IFN signalling. Host recognition of Gram-negative Salmonella occurs via pattern recognition receptors (PRRs). Ligation of PRRs activates a primarily pro-inflammatory response and promotes clearance of the pathogen. Interferons (IFNs) are a group of archetypically antiviral cytokines(14). They consist of three families and signal in an autocrine and paracrine manner through their respective receptors, which activate JAK/STAT signalling cascades to express a partly-overlapping set of hundreds of genes, known collectively as interferon-stimulated genes (ISGs). ISGs include JAK, STAT1/2, and PRRs, whose upregulation sensitises cells to enhance further antimicrobial responses. ISGs interfere with all stages of the viral life cycle and have been demonstrated to influence bacterial infections. However the effect of IFNs on bacterial infections is complex, with IFNs sometimes being beneficial to the bacteria(15-18). As they are activated as a group, the roles of individual ISGs are not well understood, particularly during bacterial infections. Large-scale screens have been performed to investigate the role of over 380 ISGs in a panel of viral infections(19-21), but screens of this scale have not been carried out for bacterial infections.During the rotation project, IFN- treatment resulted in a significant decrease in invasion, and initial data suggests that intracellular replication was also inhibited, however a high level of variation between biological repeats means this will require further investigation. The pre-treatment with IFN appeared to be required for the restriction of intracellular replication and invasion as samples that were treated only at the time of infection did not exhibit a significant reduction in either. This may indicate that the effects of IFN- are mediated by ISGs, which require time to be expressed at appropriate levels. The data collected have provided several interesting lines of enquiry for the proposed PhD project.This project aims to characterise the interaction between interferons and Salmonella enterica infections. The research will be carried out as follows:1. Investigate whether Spi1 and Spi2 effector proteins affect IFN signalling pathways in epithelial cells.2. Delineate the specific steps of IFN-b-mediated inhibition of invasion and intracellular replication.3. Identify specific ISGs that affect S. Typhimurium infections of epithelial cells.

肠沙门氏菌鼠伤寒血清型是全世界食源性和水源性胃肠炎的主要原因(1)。感染通常具有自限性，但可能对婴儿和免疫功能低下者构成重大威胁，非伤寒沙门氏菌每年在全球造成约 155,000 人死亡(2, 3)。一旦消耗，它就会被 M 细胞和树突状细胞吞噬，并可侵入包括上皮细胞在内的非吞噬细胞(4, 5)。突破上皮屏障后，它会在上皮细胞和巨噬细胞内繁殖，并且细菌可以从基底外侧侵入其他细胞(6)。侵入非吞噬细胞的能力需要沙门氏菌致病性岛 1 (Spi1) 上编码的三型分泌系统 (T3SS)。效应器协同促进膜结合巨胞质体的完成，也称为含有沙门氏菌的液泡 (SCV)(6-8)。几个小时内，营养耗尽和 pH 值降低导致另一种 T3SS Spi2 的表达上调，从而赋予鼠伤寒沙门氏菌在 SCV 中生存的能力(9-13)。众所周知，两种 T3SS 的效应蛋白都会干扰宿主信号传导，Odendall 实验室最近的工作表明，另一种肠道病原体志贺氏菌编码的 T3SS 效应蛋白的表达会阻断 IFN 信号传导。革兰氏阴性沙门氏菌的宿主识别通过模式识别受体（PRR）进行。 PRR 的连接主要激活促炎反应并促进病原体的清除。干扰素 (IFN) 是一组典型的抗病毒细胞因子 (14)。它们由三个家族组成，通过各自的受体以自分泌和旁分泌的方式发出信号，激活 JAK/STAT 信号级联，表达一组部分重叠的数百个基因，统称为干扰素刺激基因 (ISG)。 ISG 包括 JAK、STAT1/2 和 PRR，它们的上调使细胞变得敏感，从而进一步增强抗菌反应。 ISG 会干扰病毒生命周期的所有阶段，并已被证明可以影响细菌感染。然而，干扰素对细菌感染的影响很复杂，干扰素有时对细菌有益(15-18)。由于它们作为一个群体被激活，单个 ISG 的作用尚不清楚，特别是在细菌感染期间。已经进行了大规模筛选来研究超过 380 个 ISG 在一组病毒感染中的作用 (19-21)，但尚未对细菌感染进行这种规模的筛选。在轮换项目期间，IFN-治疗导致侵袭显着减少，初步数据表明细胞内复制也受到抑制，但是生物重复之间的高水平变异意味着这需要进一步研究 调查。 IFN 预处理似乎是限制细胞内复制和侵袭所必需的，因为仅在感染时处理的样品并未表现出其中任何一个的显着减少。这可能表明 IFN-的作用是由 ISG 介导的，ISG 需要时间才能以适当的水平表达。收集的数据为拟议的博士项目提供了几个有趣的探究线索。该项目旨在表征干扰素和肠道沙门氏菌感染之间的相互作用。研究工作如下： 1．探讨Spi1和Spi2效应蛋白是否影响上皮细胞中的IFN信号通路。2．简述IFN-b介导的抑制侵袭和细胞内复制的具体步骤。 3．确定影响上皮细胞鼠伤寒沙门氏菌感染的特定 ISG。