Innate Immunity and Bacterial Quorum Sensing

描述（由申请人提供）：群体感应是一种细胞间通信系统，允许细菌种群的成员根据细胞密度协调其行为。群体感应的介质是小的，可扩散的信息素或在足够细菌密度下信号基因表达程序的自诱导剂。利用这种交流方式调节宿主定植和毒力的细菌病原体名单正在扩大，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物通过“群体猝灭”抑制致病菌的交流来促进先天免疫。在初步数据中，我们发现吞噬细胞衍生的活性氧和活性氮中间体（ROI和RNI）靶向医学上重要的人类病原体金黄色葡萄球菌的毒力诱导肽，作为宿主的先天防御机制。此外，血液和上皮细胞中切割这些自诱导剂中存在的内酯键的酶可以抑制群体感应依赖的毒力。为了验证这一假设，我们将追求以下具体目标：1)确定吞噬细胞来源的ROI和RNI对宿主防御金黄色葡萄球菌和表皮葡萄球菌群体感应充足和缺乏菌株感染的贡献，以及ROI和RNI在功能上灭活这些病原体分泌的毒力信息素的能力；2)利用质谱法确定ROI和rni介导的这些毒力信息素的体外修饰及其在体内的生物学意义；3)确定非吞噬细胞先天效应物是否抑制群体感应依赖性毒力。这些将包括对氧氧化酶家族（硫内酯酶）和上皮细胞表达的Nox/Duox酶（氧化酶和过氧化物酶）。了解这些先天效应对群体猝灭的贡献以及病原体如何避免它可以增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.