Pathogenic strategies of the swine pathogen Streptococcus suis

猪病原体猪链球菌的致病策略

• 批准号: RGPIN-2015-04146
• 负责人: Grenier, Daniel
• 金额: $ 3.28万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=689061
• 关键词: Pathogenic; strategies; swine; pathogen; Streptococcus

Streptococcus suis (serotype 2) is a swine pathogen responsible for important economic losses in the swine industry worldwide. Major infections caused by this pathogen include arthritis, septicemia, meningitis and endocarditis. The research program of my laboratory focusses on the identification and characterization of pathogenic strategies developed by S. suis. More specifically, the research proposed for the next five years relies on two specific hypotheses: 1) The cell surface protease SspA of S. suis plays several key roles in the infectious process; and 2) Membrane vesicles secreted by S. suis possess a wide array of pathological functions and represent a new virulence mechanism. The studies related to each hypothesis are outlined below are a logical continuation of the work performed during my past NSERC research funding. ***In the first part of my research program, I propose to investigate the mechanisms by which the SspA protease may contribute to S. suis infections. We will first determine the parameters and growth conditions (biofilm growth, co-culture with host cells, presence of serum or sub-minimal inhibitory concentrations of antibiotics, etc) upregulating the expression of sspA gene. Then, using an SspA-deficient mutant as well as the purified recombinant protease, we will investigate the effects of S. suis SspA on i) inactivation of the innate immune components (antimicrobial peptide, epithelial cell barrier integrity), and ii) amplification of the inflammatory response through shedding of active TNF-alpha and generation of bradykinin from high-molecular-weight kininogens.***In the second part of my research program, I propose to characterize membrane vesicles produced by S. suis and to identify their pathological functions. We will first study the modulation of S. suis vesicle production by various environmental conditions. Then, we will investigate the role of vesicles in toxin delivery by characterizing their composition using a proteomic approach. Given that preliminary data revealed that vesicles possess a high DNase activity, we will evaluate their ability to allow S. suis to escape from neutrophil extracellular traps. Lastly, the inflammatory potential of S. suis membrane vesicles will be tested by investigating their ability to i) activate the nuclear factor-kB signaling pathway, and ii) induce the secretion of inflammatory mediators by a co-culture model of microvascular endothelial cells and macrophages.***Significance: The proposed studies have two complementary objectives: (i) to increase our basic knowledge of the pathogenic strategies used by S. suis to counteract the host defense system and amplify the destructive inflammatory response, and (ii) to use this knowledge to identify new vaccine molecule candidates and to design drugs targeting bacterial virulence factors in view to more efficiently control S. suis infections.

猪链球菌(血清型2)是造成世界养猪业重大经济损失的主要病原菌。这种病原体引起的主要感染包括关节炎、败血症、脑膜炎和心内膜炎。我的实验室的研究计划集中在鉴定和表征猪链球菌开发的致病策略。更具体地说，未来五年的研究依赖于两个具体的假设：1)猪链球菌细胞表面蛋白水解酶SSPA在感染过程中发挥几个关键作用；2)猪链球菌分泌的膜泡具有广泛的病理功能，代表了一种新的毒力机制。与每个假设相关的研究概述如下，这是我在过去的NSERC研究资助期间所做工作的合乎逻辑的延续。*在我的研究计划的第一部分，我建议调查SSPA蛋白酶可能导致猪链球菌感染的机制。我们将首先确定上调SSPA基因表达的参数和生长条件(生物膜生长、与宿主细胞的共同培养、血清或抗生素的亚最低抑菌浓度等)。然后，我们将利用SSPA缺失突变体和纯化的重组蛋白酶，研究猪链球菌SSPA对天然免疫成分(抗菌肽、上皮细胞屏障完整性)的灭活，以及通过脱落活性的肿瘤坏死因子-α和从高分子激肽原产生缓激肽而放大炎症反应的作用。*在我的研究计划的第二部分，我建议对猪链球菌产生的膜小泡进行表征，并鉴定其病理功能。我们将首先研究不同环境条件对猪链球菌囊泡生产的调节作用。然后，我们将通过使用蛋白质组学方法表征小泡的组成，来研究小泡在毒素传递中的作用。鉴于初步数据显示小泡具有很高的DNA酶活性，我们将评估它们允许猪链球菌逃离中性粒细胞外陷阱的能力。最后，将通过调查猪链球菌膜泡的致炎潜能来测试它们的能力：i)激活核因子-kB信号通路，以及ii)通过微血管内皮细胞和巨噬细胞的共培养模型诱导炎症介质的分泌。*意义：拟议的研究有两个相辅相成的目标：(I)增加我们对猪链球菌用来对抗宿主防御系统和放大破坏性炎症反应的致病策略的基本知识，以及(Ii)利用这些知识来寻找新的疫苗候选分子和设计针对细菌毒力因子的药物，以期更有效地控制猪链球菌感染。