Innate Immunity and Bacterial Quorum Sensing

描述(申请人提供)：群体感应是一种细胞间的通讯系统，允许细菌群体的成员根据细胞密度协调他们的行为。群体感应的媒介是小的、可扩散的信息素或自动诱导剂，它们以足够的细菌密度向基因表达程序发出信号。使用这种通信方法来调节宿主定植和毒力的细菌病原体的名单正在扩大，其中包括一些最常见的人类病原体。我们假设，几种哺乳动物效应器通过“群体猝灭”来抑制病原细菌的交流，从而对先天免疫作出贡献。在初步数据中，我们发现吞噬细胞衍生的活性氧和氮中间产物(ROI和RNI)以医学上重要的人类病原体金黄色葡萄球菌的毒力诱导肽为靶标，作为宿主的一种天然防御机制。此外，血液和上皮细胞中裂解这些自身诱导物中存在的内酯键的酶可以抑制依赖群体感应的毒力。为了验证这一假说，我们将追求以下具体目标：1)确定吞噬细胞来源的ROI和RNI对金黄色葡萄球菌和表皮葡萄球菌群体感应充足和缺陷菌株感染宿主防御的贡献，以及ROI和RNI功能失活这些病原体分泌的毒力信息素的能力；2)通过质谱分析确定ROI和RNI介导的这些毒力信息素在体外的修饰及其在体内的生物学意义；以及3)确定非吞噬细胞天然效应物是否抑制群体感应依赖的毒力。这些酶包括对氧磷酶家族(硫代内酯酶)和上皮细胞表达的NOx/DUOX酶(氧化物酶和过氧化物酶)。了解这些天生的效应器对群体猝灭的贡献以及病原体如何避免群体猝灭，可以加强针对毒力信息素灭活的药物设计。

DESCRIPTION (provided by applicant): Quorum sensing is a cell-to-cell communication system that permits members of a bacterial population to coordinate their behavior dependent on cell density. The mediators of quorum sensing are small, diffusible pheromones or autoinducers that signal gene expression programs at a sufficient bacterial density. The list of bacterial pathogens that use this method of communication to regulate host colonization and virulence is expanding and includes some of the most common pathogens of humans. We hypothesized that several mammalian effectors contribute to innate immunity by inhibiting pathogenic bacterial communication via "quorum quenching." In preliminary data we show that phagocyte-derived reactive oxygen and nitrogen intermediates (ROI and RNI) target a virulence-inducing peptide of the medically important human pathogen Staphylococcus aureus as an innate defense mechanism of the host. In addition, enzymes in blood and epithelial cells that cleave lactone bonds that are present in these autoinducers could inhibit quorum sensing-dependent virulence. To test this hypothesis, we will pursue the following specific aims: 1) To determine the contribution of phagocyte-derived ROI and RNI to host defense against infection with quorum sensing-sufficient and -deficient strains of S. aureus and S. epidermidis and the ability of ROI and RNI to functionally inactivate the virulence pheromones secreted by these pathogens; 2) To determine the ROI- and RNI-mediated modifications of these virulence pheromones by mass spectrometry in vitro and their biologic significance in vivo; and 3) To determine if non-phagocyte innate effectors inhibit quorum sensing-dependent virulence. These will include the paraoxonase enzyme family (thiolactonases) and the epithelial cell-expressed Nox/Duox enzymes (oxidases and peroxidases). Understanding the contribution of these innate effectors to quorum quenching and how pathogens avoid it could augment drug design that targets virulence pheromones for inactivation.