Host-Pathogen Interactions in the Mammalian Airway

描述(申请人提供)：哺乳动物气管衬里的上皮细胞是宿主抵御空气传播的微生物病原体的关键部位，释放出大量的抗微生物因子。这些防御系统的缺陷可能会导致反复的呼吸道感染。这些防御机制之一是诱导产生β-防御素，这是一类在哺乳动物上皮细胞中高度丰富的同源抗菌肽。编码β-防御素的基因在呼吸道上皮细胞中高水平表达，并由细菌产物和炎症介质诱导。初步和已发表的数据支持这样的假设，即一些致病菌株可以通过抑制β-防御素基因的表达来逃避呼吸道的天然免疫系统，这反过来又可以削弱呼吸道的抗菌防御。特定的细菌毒力因子允许逃避宿主第一道防线以定植于呼吸道的机制尚未确定。阐明这些机制将有助于制定治疗呼吸道感染的策略。我们研究的长期目标是更好地了解呼吸道内动态的宿主防御系统。在这项建议中，我们重点研究呼吸道病原体支气管败血波氏杆菌与其呼吸道上皮中的靶细胞之间的相互作用。败血杆菌与动物的呼吸道感染有关，与百日咳杆菌密切相关，百日咳杆菌是人类百日咳的病原体。我们假设，呼吸道上皮细胞对细菌的反应是通过特定受体识别分子模式，导致核因子-kappaB的激活和β-防御素基因的表达，以防止定植。支气管败血杆菌的致病株可以通过干扰天然免疫反应的III型分泌因子来干扰抗菌肽基因的上调，从而防止抗菌肽产量的增加。为了验证这些假设，提出了以下目标：1.确定支气管败血杆菌与呼吸道上皮细胞的相互作用以及由此产生的先天免疫反应的诱导。2.明确了强毒力支气管败血杆菌抑制天然免疫诱导的机制。这些研究的目的是确定呼吸道上皮细胞如何通过启动宿主防御反应来响应这种模型病原体。第二个目标将利用蛋白质组学来确定导致这一作用的细菌因素，以及该因素与防御反应相互作用的全面特征，以确定细菌如何规避这一反应。这些信息将作为开发设计用于呼吸道的新疗法的基础。这将包括调节内源性抗菌肽表达的策略，以防止严重的细菌感染。

DESCRIPTION (provided by applicant): Epithelial cells lining the mammalian trachea form a crucial site in the host defense against airborne microbial pathogens, releasing numerous antimicrobial factors. Deficiencies in these defenses may result in recurrent airway infections. One of these defense mechanisms is the inducible production of beta-defensins, a class of homologous antibiotic peptides highly abundant in mammalian epithelial cells. The genes encoding beta-defensins are expressed at high levels in the respiratory epithelium, and are induced by bacterial products and inflammatory mediators. Preliminary and published data support the hypothesis that some pathogenic strains of bacteria can evade the innate immune system in the airway by inhibiting beta-defensin gene expression, which can in turn diminish the antimicrobial defense of the airway. The mechanisms by which the specific bacterial virulence factors allow evasion of the first lines of host defense to colonize the airway are not yet defined. Elucidation of these mechanisms will aid in the development of therapeutic strategies for airway infections. The long-range goal of our research is to better understand the dynamic host defense systems in the airway. In this proposal we focus on the interactions of the airway pathogen, Bordetella bronchiseptica with its target cells in the respiratory epithelium. B. bronchiseptica is associated with respiratory infections in animals, and is closely related to B. pertussis, the causative agent of whooping cough in humans. We hypothesize that airway epithelial cells respond to bacteria by recognition of molecular patterns by specific receptors, resulting in the activation of NF-kappaB and induction of beta-defensin gene expression in order to prevent colonization. Pathogenic strains of B. bronchiseptica can prevent the increased production of antimicrobial peptides by interfering with the upregulation of the antimicrobial peptide genes through a type III secretion factor which interferes with the innate immune response. To test these hypotheses, the following aims are proposed: 1. Define the interaction of B. bronchiseptica with airway epithelial cells and the resultant induction of an innate immune response. 2. Define the mechanism of inhibition of innate immune induction by virulent B. bronchiseptica. The objective of these studies is to define how the airway epithelium responds to this model pathogen by the initiation of a host defense response. The second aim will determine how the bacterium circumvents this response utilizing proteomics to identify the bacterial factor responsible for this action, as well as a comprehensive characterization of the interaction of this factor and the defense response. The information will serve as a foundation for the development of novel therapies designed to work in the respiratory tract. This would include strategies to modulate the endogenous antimicrobial peptide expression to prevent serious bacterial infections.