Bacterial acyl homoserine lactones as immune modulators and drug targets

描述(由申请人提供)：这项研究计划的首要目标是调查细菌群体感应因子在微生物发病中的作用，然后评估基于群体猝灭对选定的新兴病原体，如鲍曼不动杆菌、鼠疫耶尔森菌、马来伯克霍尔德氏菌和假鼻疽伯克霍尔德氏菌的抗毒力策略。这些革兰氏阴性细菌(鲍曼不动杆菌除外)是A类(鼠疫杆菌)和B类(假单胞菌和马利氏杆菌)的精选病原体，指定它们是因为它们极有可能用于生物恐怖主义或生物武器事件。虽然不像其他A类和B类病原体那样具有潜在的致命性，但它们仍然构成重大的发病威胁，如果通过气雾剂传播，将具有很高的传染性潜力。目前，FDA批准的针对此类细菌感染的治疗方法仅限于两到三种抗生素，而且都只有暴露后的适应症。此外，以抗生素为基础的治疗很容易因引入已知的耐药性因素而无效。因此，开发替代的抗感染策略来保护这些病原体具有重要的意义。另一方面，鲍曼不动杆菌正在成为医院感染中一种常见的多重耐药病原体，并日益威胁到在伊拉克和阿富汗战场上导致美国士兵伤口感染的威胁。所有为这些研究选择的病原体都已被证明利用细菌细胞间的通信，也称为“群体感应”。最近，我们和其他人已经表明，细菌QS系统是预防和治疗干预的一个有吸引力的靶点。QS信号是基于可扩散的小分子的交换，如N-酰基高丝氨酸内酯(AHL)，事实上鲍曼不动杆菌、马来杆菌、假鼻疽杆菌和鼠疫杆菌都使用这种物质。类似于经典的病原体相关分子模式(PAMPs)，如细菌脂多糖(LPS)和肽聚糖，AHLS只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作用，这表明AHL在摧毁宿主天然免疫方面具有额外的作用。申请人进行的研究提供了进一步的证据，证明AHL直接激活包括白细胞在内的哺乳动物细胞中的信号事件，并且这些信号事件通过不同于经典的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，除了在细菌交流中发挥作用外，AHL自身诱导剂本身也可能成为抗感染免疫治疗的新靶点。在这项建议中，化学、分子生物学、免疫学和遗传学的强大组合将被利用，为抗自身诱导剂预防和治疗策略的产生、开发和评估提供坚实的合理基础。 与公共卫生相关：我们研究的细菌要么是新出现的病原体，这些病原体已经变得高度抗药性，因此在临床环境中存在问题，要么是潜在的生物恐怖主义和BioWare制剂。它们已被证明利用细菌细胞间的通信，也称为“群体感应”来控制它们的毒力。这些细菌用于交流的分子是抗感染治疗的一个有吸引力的目标，因为清除这些小化合物将使细菌无害。此外，这些分子还会颠覆宿主免疫系统，从而使微生物能够首先确定自己的感染情况。我们建议开发用于干扰细菌群体感应的抗体，从而开发一种对抗细菌感染的新策略。

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.