Bacterial acyl homoserine lactones as immune modulators and drug targets

描述（由申请人提供）：本研究计划的总体目标是研究细菌群体感应因子在微生物发病机制中的作用，然后评估基于群体猝灭的抗毒策略，以对抗选定的新兴病原体，如鲍曼不动杆菌、鼠疫耶尔森氏菌、马氏伯克氏菌和假马利氏伯克氏菌。这些革兰氏阴性菌（鲍曼假芽胞杆菌除外）是A类（鼠疫杆菌）和B类（假芽胞杆菌和马氏芽胞杆菌）选定病原体，因为它们极有可能被用于生物恐怖主义事件或生物战。虽然不像其他A类和B类病原体那样致命，但它们仍然构成重大的发病率威胁，如果通过气溶胶传播，将具有很高的传染性潜力。目前，FDA批准的治疗此类细菌感染的药物数量仅限于两到三种抗生素，而且都只有暴露后适应症。此外，以抗生素为基础的治疗很容易因引入已知的耐药因素而失效。因此，开发替代的抗感染策略对这些病原体的保护具有高度的重要性和意义。另一方面，鲍曼不动杆菌正在成为医院感染中常见的多药耐药病原体，并且在伊拉克和阿富汗战场上的美国士兵中引起伤口感染的威胁越来越大。为这些研究选择的所有病原体都显示利用细菌细胞间的通讯，也称为“群体感应”。最近，我们和其他人已经表明，细菌QS系统代表了预防和治疗干预的一个有吸引力的目标。QS信号是基于可扩散小分子的交换，如n -酰基同丝氨酸内酯（AHL），事实上鲍曼芽胞杆菌、马雷芽胞杆菌、假马莱芽胞杆菌和鼠疫杆菌都使用这种小分子。与经典的病原体相关分子模式（PAMPs）类似，如细菌脂多糖（LPS）和肽聚糖，ahl仅由微生物病原体产生，而不是由哺乳动物宿主产生。最近的研究表明，基于ahl的QS分子对巨噬细胞具有强大的细胞毒性，这表明ahl在破坏宿主先天免疫方面发挥了额外的作用。申请人进行的研究提供了进一步的证据，证明ahl直接激活哺乳动物细胞（包括白细胞）中的信号事件，并且这些事件通过不同于经典PAMP识别受体（PRR）途径的机制发生，例如典型的toll样受体（TLR）和nod样受体（NLR）途径。因此，除了在细菌通讯中的作用外，AHL自身诱导剂本身可能是抗感染免疫治疗的新靶点。本研究将结合化学、分子生物学、免疫学和遗传学等多种方法，为抗自身诱导剂预防和治疗策略的产生、发展和评估提供坚实的理论基础。

DESCRIPTION (provided by applicant): The overarching goal of this research proposal is to investigate the role of bacterial quorum sensing factors in microbial pathogenesis and to then evaluate an anti-virulence strategy based on quorum quenching against selected emerging pathogens, such Acinetobacter baumannii, Yersinia pestis, Burkholderia mallei, and Burkholderia pseudomallei. These Gram-negative bacteria (with the exception of A. baumannii) are category A (Y. pestis) and B (B. pseudomallei and B. mallei) select pathogens, designated so as they are highly likely to be used in incidents of bioterrorism or biowarfare. While not potentially as lethal as other category A and B pathogens, they still pose significant morbidity threats and if delivered by aerosol would have high infectivity potentials. Currently, the number of FDA approved therapies against such bacterial infections is limited to two or three antibiotics and all only have post exposure indications. Additionally, the antibiotic-based therapy could easily be rendered ineffective by introduction of known resistance factors. Therefore, it is of high importance and significance to develop alternative anti-infective strategies for protection against these pathogens. On the other hand, A. baumannii is emerging as a common multi-drug resistance pathogen in nosocomial infections as well as an increasing threat of causing wound infections seen in U.S. soldiers on the battlefields in Iraq and Afghanistan. All pathogens selected for these studies have been shown to utilize bacterial cell-to- cell communication, also called "quorum sensing". Recently, we and others have shown that bacterial QS systems represent an attractive target for prophylactic and therapeutic intervention. QS signaling is based on the exchange of small diffusible molecules, such as N-acyl homoserine lactones (AHL), which are in fact used by A. baumannii, B. mallei, B. pseudomallei and Y. pestis. Similar to classical pathogen-associated molecular patterns (PAMPs), such as bacterial lipopolysaccharide (LPS), and peptidoglycan, AHLs are only produced by microbial pathogens, but not by the mammalian host. Recent research has revealed that the AHL-based QS molecules exert potent cytotoxicity against macrophages, suggesting an additional role for AHLs in dismantling host innate immunity. Studies conducted by the applicants have provided further evidence that AHLs directly activate signaling events in mammalian cells, including leucocytes, and that these occur through mechanisms distinct from the classical PAMP recognition receptor (PRR) pathways, such as the canonical Toll-like receptor (TLR) and Nod-like receptor (NLR) pathways. Therefore, besides their role in bacterial communication, AHL autoinducers themselves might represent new attractive targets for anti-infective immunotherapy. In this proposal, a powerful combination of chemistry, molecular biology, immunology, and genetic approaches will be harnessed to provide a solid rational basis for the generation, development, and evaluation of anti-autoinducer prophylactic and therapeutic strategies. PUBLIC HEALTH RELEVANCE: The bacteria selected for our studies are either new emerging pathogens that have become highly antibiotic resistant, and thus, problematic in clinical settings or are potential bioterrorism and bioware agents. They have been shown to utilize bacterial cell-to-cell communication, also called "quorum sensing" to control their virulence. The molecules that these bacteria use for their communication represent an attractive target for anti-infective therapy as the scavenging of the small compounds would render the bacteria harmless. In addition, these molecules also subvert the host immune system, thus, enabling the microbes to establish their infection in the first place. We propose to develop antibodies for the disruption of bacterial quorum sensing and thus, to develop a new strategy in fighting bacterial infections.