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4500万例病例和30万例死亡，其中大多数发生在儿童中。尽管疫苗覆盖率很高，但自20世纪90年代以来，几个发达国家的发病率一直在增加，这显然是由于青少年和年轻成人在儿童时期接种疫苗而不是感染，特别是那些接种了非细胞疫苗的人的免疫力下降。了解疫苗成分在发病机制和免疫中的作用对改进疫苗的开发至关重要。百日咳的病原体是百日咳杆菌和副百日咳杆菌。这些严格意义上的人类特异性病原体与支气管脓毒杆菌有极其密切的关系，后者的宿主范围很广，几乎包括所有哺乳动物。我们一直在采取比较的方法，包括这三个博德特拉亚种，研究毒力基因调控和特异性毒力因子在发病机制中的作用。使用分枝杆菌使我们能够在自然细菌-宿主相互作用的背景下在实验室中研究呼吸道感染，并且使用表达异源毒力因子的嵌合分枝杆菌和百日咳分枝杆菌菌株使我们能够证明几种毒力因子，包括丝状血凝素（FHA），在这些亚种之间具有功能可互换。FHA是一种大的表面相关和分泌蛋白，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，并且它允许博德特拉菌抑制其宿主的炎症反应。FHA也是双伴侣分泌（TPS）途径家族的典型成员之一。我们之前的研究表明，细菌表面的FHA拓扑结构与假设的相反，并导致了TPS新模型的发展。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功能的洞察力，反之亦然。我们建议通过实验来确定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，我们的研究结果还可能确定控制炎症的新途径。我们还将确定FHA前体FhaB的c端如何控制FHA从细菌表面的成熟和释放。我们的研究结果将提供对TPS机制的深入了解，并可能为蛋白质如何在细胞表面折叠提供新的范例。

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.