Function and Secretion of Bordetella Filamentous Hemagglutinin

描述(由申请人提供)：百日咳(也称为百日咳)仍然是一个全球性的健康问题，估计每年有4500万病例和30万人死亡，主要发生在儿童中。尽管疫苗覆盖率很高，但自1990年代以来，几个发达国家的发病率一直在上升，这显然是由于儿童时期接种疫苗而不是感染的青少年和年轻人的免疫力减弱，特别是那些接种了无细胞疫苗的青少年。了解疫苗成分如何在发病机制和免疫中发挥作用，对于改进疫苗的开发至关重要。百日咳的病原体为百日咳杆菌和副百日咳杆菌。这些严格的人类特有病原体与支气管败血波尔德氏菌关系极其密切，它的宿主范围很广，几乎包括所有哺乳动物。我们一直在采取比较的方法，包括所有这三个波尔德氏菌亚种，以研究毒力基因调控和特定毒力因子在致病中的作用。使用支气管败血杆菌使我们能够在实验室自然细菌-宿主相互作用的背景下研究呼吸道感染，而表达异源毒力因子的支气管败血杆菌和百日咳杆菌嵌合菌株的使用使我们能够证明几种毒力因子，包括丝状血凝素(FHA)，在这些亚种之间可以功能互换。FHA是一种大的表面相关和分泌蛋白，也是百日咳疫苗的主要成分之一。我们已经证明，FHA是下呼吸道(特别是气管)定植所必需的，它允许波氏杆菌抑制宿主的炎症反应。FHA也是两个伙伴分泌(TPS)途径家族的典型成员之一。我们以前的研究表明，FHA在细菌表面的拓扑结构与假设相反，并导致了一种新的TPS模型的开发。我们的研究也证明了同时研究分泌和功能的重要性，因为分泌实验的结果揭示了对功能的洞察，反之亦然。我们建议进行实验，以确定FHA如何调节呼吸道炎症，识别FHA的宿主细胞受体，并确定FHA中对受体结合重要的特定区域和氨基酸。除了揭示FHA功能的机制外，我们的结果还可能确定总体上控制炎症的新途径。我们还将确定FHA前体FhaB的C末端如何控制FHA的成熟和从细菌表面释放。我们的结果将提供对TPS机制的洞察，并可能为蛋白质如何在细胞表面折叠设定一个新的范例。

DESCRIPTION (provided by applicant): Pertussis (also known as whooping cough) continues to be a global health problem with an estimated 45 million cases annually and 300,00 deaths, which occur mostly in children. Despite high vaccine coverage, incidence has been increasing in several developed countries since the 1990s, due apparently to waning immunity in adolescents and young adults who were vaccinated, rather than infected, as children, especially those vaccinated with acellular vaccines. Understanding how vaccine components function in pathogenesis and immunity is critical to the development of improved vaccines. The causative agents of pertussis are Bordetella pertussis and Bordetella parapertussishu. These strictly human-specific pathogens are extremely closely related to Bordetella bronchiseptica, which has a broad host range that includes nearly all mammals. We have been taking a comparative approach, including all three of these Bordetella subspecies to study the roles of virulence gene regulation and of specific virulence factors in pathogenesis. Using B. bronchiseptica allows us to study respiratory infection in the lab in the context of a natural bacterial-host interaction, and the use of chimeric B. bronchiseptica and B. pertussis strains that express heterologous virulence factors has allowed us to demonstrate that several virulence factors, including Filamentous hemagglutinin (FHA), are functionally interchangeable between these subspecies. FHA is a large surface-associated and secreted protein and one of the primary components of pertussis vaccines. We have shown that FHA is required for colonization of the lower respiratory tract (specifically the trachea) and that it allows Bordetella to suppress the inflammatory response of its hosts. FHA is also one of the prototypical members of the Two Partner Secretion (TPS) pathway family. Our previous studies showed that the topology of FHA on the bacterial surface was the opposite of what had been assumed and led to the development of a new model for TPS. Our studies also demonstrated the importance of studying secretion and function simultaneously as results from secretion experiments revealed insight into function and vice versa. We propose experiments to determine how FHA modulates inflammation in the respiratory tract, to identify host cell receptors for FHA, and to identify specific regions and amino acids within FHA that are important for receptor binding. In addition to revealing mechanisms of FHA function, our results may identify novel pathways by which inflammation is controlled in general. We will also determine how the C-terminus of the FHA precursor, FhaB, controls maturation and release of FHA from the bacterial surface. Our results will provide insight into the TPS mechanism, and may set a new paradigm for how proteins are folded on cell surfaces.