A. phagocytophilum and NF-kB signaling

描述(申请人提供)：人类粒细胞无形体病(HGA)是由嗜中性粒细胞胞内专性细菌--吞噬无浆菌引起的硬虱传播疾病。吞噬嗜血杆菌破坏宿主粒细胞功能，使抗菌功能失活，激活促炎反应。“激活-失活”的中性粒细胞促进新宿主细胞的招募和组织损伤，但无法产生有效的抗菌反应。我们证明了细菌通过上调趋化因子基因来招募新的宿主细胞的优势，类似地，任何炎症的上调都可以使细菌受益。炎症反应是通过核因子-β信号转导的，吞噬弧菌显著上调核因子-βB信号，吞噬弧菌的生存可能依赖于对这一途径的颠覆。我们推测，吞噬弧菌感染的中性粒细胞中的核因子-βB信号上调：1)对病原体的生存至关重要，并依赖于活动性感染，2)导致中性粒细胞功能被颠覆，使病原体受益，但不利于细胞/组织损伤。因此，我们建议： 1.揭示核因子-βB信号在促进嗜中性粒细胞吞噬杆菌生长和/或改变中性粒细胞功能中的作用，从而使细菌得以生存和繁殖。抑制吞噬细胞繁殖的抑制途径和沉默基因将识别关键的高优先级靶标基因、蛋白质、途径和/或细菌靶向的功能。 2.明确嗜中性粒细胞与吞噬细胞相关的宿主细胞颠覆引起的中性粒细胞/粒细胞致炎功能的改变，并允许中性粒细胞介导的组织损伤。这些数据将把吞噬细胞性金黄色葡萄球菌改变的特定途径与促炎中性粒细胞功能改变联系起来，以确定它们在发病机制和疾病中的作用。这最终将有助于寻找移位到宿主体内的细菌效应器，这些细菌效应器介导中性粒细胞功能变化，掩盖组织损伤、炎症和疾病。 我们的长期目标是了解专性细胞内细菌利用宿主细胞生存的机制。短期目标是确定吞噬细胞性弧菌效应物的可能宿主靶点，以增强炎症反应和病原体生存。这些研究将为深入研究HGA的发病机制提供重要线索，并将提供有关中性粒细胞在某些炎症和感染状态下的功能的广泛信息。与公共卫生相关：人类粒细胞无形体病是一种新出现的、由壁虱传播的感染，可以是轻微的或致命的。研究表明，这种细菌必须生活在血细胞内，通过改变宿主血细胞使其有利于细菌生存而导致感染，部分原因是通过增加炎症信号。这项应用建议详细检查增加炎症的蛋白质、基因和途径，以及这是否真的促进了病原体的生存。这可能会带来关于这种生物体和其他生物体如何发生疾病的新信息，也许还会带来关于如何对抗这种感染或改变其他疾病的宿主细胞功能的新信息。

DESCRIPTION (provided by applicant): Human granulocytic anaplasmosis (HGA) is tick-borne disease caused by Anaplasma phagocytophilum, an obligate intracellular bacterium of neutrophils. A. phagocytophilum subverts host granulocyte functions, deactivating antimicrobial function and activating proinflammatory response. The "activated-deactivated" neutrophil promotes recruitment of new host cells and tissue injury, but is unable to generate effective antimicrobial responses. We demonstrated a bacterial advantage to new host cell recruitment with chemokine gene upregulation and, analogously, any up-modulation of inflammation could benefit the bacterium. Inflammatory response is mediated through NF-?B signaling, which is significantly upregulated with A. phagocytophilum, whose survival likely depends on subversion of this pathway. We hypothesize that upregulated NF-?B signaling in A. phagocytophilum-infected neutrophils: 1) is critical for pathogen survival and dependent upon active infection, and 2) leads to subverted neutrophil functions that benefit the pathogen but belie cell/tissue injury. Thus, we propose: 1. To show a role for NF-?B signaling in A. phagocytophilum growth enhancement and/or altered neutrophil function that permit bacterial survival and propagation. Inhibited pathways and silenced genes that suppress A. phagocytophilum propagation will identify critical high priority targets genes, proteins, pathways and/or functions targeted by the bacterium. 2. To discern the altered neutrophil/granulocyte proinflammatory functions that result from A. phagocytophilum-associated subversion of host cells and permit neutrophil-mediated tissue injury. These data will link specific A. phagocytophilum-altered pathways with proinflammatory neutrophil function alterations to determine their role in pathogenesis and disease. This will eventually facilitate the search for bacterial effectors translocated into the host that mediate neutrophil function changes and belie tissue injury, inflammation and disease. Our long-term goals are to understand the mechanisms by which obligate intracellular bacteria exploit host cells for survival. The short-term objective is to identify likely host targets of A. phagocytophilum effectors that enhance inflammatory response and pathogen survival. Such studies will yield important clues about the HGA pathogenesis to advance in-depth investigation and will provide broad information about neutrophil function in some inflammatory and infectious states. PUBLIC HEALTH RELEVANCE: Human granulocytic anaplasmosis is an emerging tick-borne infection that can be mild or fatal. Research indicates that the bacterium, which must live inside of a blood cell, causes the infection by changing its host blood cell to favor bacterial survival, in part by increasing inflammation signals. This application proposes to examine in detail the proteins, genes, and pathways by which inflammation is increased, and whether this truly promotes survival of the pathogen. This could lead to new information on how disease occurs with this organism and others, and perhaps new information about ways to combat this infection or to change host cell function in other diseases.