Bacterial acyl homoserine lactones as immune modulators and drug targets

描述（由申请人提供）：本研究提案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，然后评估基于群体淬灭的抗毒力策略，以对抗选定的新兴病原体，如鲍曼不动杆菌、鼠疫耶尔森菌、鼻疽伯克霍尔德菌和类鼻疽伯克霍尔德菌。这些革兰氏阴性菌（A. baumannii）为A类（Y. pestis）和B（B.类鼻疽和B. malei）选定病原体，因为它们极有可能用于生物恐怖主义或生物战事件。虽然不像其他A类和B类病原体那样潜在致命，但它们仍然构成重大的发病威胁，如果通过气雾剂递送，将具有高传染性潜力。目前，FDA批准的针对此类细菌感染的疗法数量仅限于两种或三种抗生素，并且所有抗生素都只有暴露后适应症。此外，通过引入已知的耐药因子，基于抗生素的治疗很容易变得无效。因此，开发替代性抗感染策略以保护免受这些病原体的侵害具有重要意义。另一方面，A.鲍曼不动杆菌正在成为医院感染中常见的多药耐药性病原体，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。 这些研究中选择的所有病原体都显示出利用细菌细胞间通讯，也称为“群体感应”。最近，我们和其他人已经表明，细菌QS系统是一个有吸引力的预防和治疗干预的目标。QS信号是基于小的可扩散分子的交换，如N-酰基高丝氨酸内酯（阿勒），实际上是由A.鲍曼不动杆菌B. baumannii，B.鼻疽B. mallei，B. pseudomallei和Y.鼠疫与经典的病原体相关分子模式（PAMP），如细菌脂多糖（LPS）和肽聚糖类似，AHLs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分子对巨噬细胞产生有效的细胞毒性，这表明AHL在破坏宿主先天免疫中具有额外的作用。申请人进行的研究提供了进一步的证据，证明AHL直接激活哺乳动物细胞（包括白细胞）中的信号传导事件，并且这些事件通过不同于经典PAMP识别受体（PRR）途径（例如经典Toll样受体（TLR）和Nod样受体（NLR）途径）的机制发生。因此，除了它们在细菌通讯中的作用外，阿勒自身诱导物本身可能是抗感染免疫治疗的新的有吸引力的靶点。在这项提案中，化学，分子生物学，免疫学和遗传学方法的强大组合将被利用，为抗自身诱导物预防和治疗策略的产生，开发和评估提供坚实的合理基础。 公共卫生相关性：选择用于我们研究的细菌是已经变得高度抗生素耐药性的新出现的病原体，因此在临床环境中存在问题，或者是潜在的生物恐怖主义和生物战剂。它们已被证明利用细菌细胞间的通讯，也称为“群体感应”来控制它们的毒力。这些细菌用于其通信的分子代表了抗感染治疗的有吸引力的目标，因为清除小化合物将使细菌无害。此外，这些分子还破坏宿主免疫系统，从而使微生物能够首先建立感染。我们建议开发用于破坏细菌群体感应的抗体，从而开发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.