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讯系统，允许细菌群体的成员根据细胞密度协调其行为。群体感应的介质是小的、可扩散的信息素或自诱导物，其在足够的细菌密度下发出基因表达程序的信号。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列表正在扩大，包括一些最常见的人类病原体。我们假设，几种哺乳动物效应子通过“群体淬灭”抑制致病细菌的通讯，从而促进先天免疫。“在初步数据中，我们表明吞噬细胞衍生的活性氧和氮中间体（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，血液和上皮细胞中的酶，裂解这些自身诱导物中存在的内酯键，可以抑制群体感应依赖性毒力。为了验证这一假设，我们将追求以下具体目标：1）确定吞噬细胞衍生的ROI和RNI对宿主防御群体感应充足和缺乏的S菌株感染的贡献。金黄色葡萄球菌和表皮细胞和ROI和RNI功能性地抑制这些病原体分泌的毒力信息素的能力; 2）通过体外质谱测定这些毒力信息素的ROI和RNI介导的修饰及其在体内的生物学意义;和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。这些将包括对氧磷酶家族（硫内酯酶）和上皮细胞表达的Nox/Duox酶（氧化酶和过氧化物酶）。了解这些先天效应子对群体淬灭的贡献以及病原体如何避免它可以增强靶向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.