The roles of Anaplasma phagocytophilum surface proteins in cellular invasion

描述（由申请方提供）：嗜吞噬细胞无形体是一种专性细胞内细菌和立克次体病原体，可侵入中性粒细胞和内皮细胞，引起新发和潜在致死性感染，即人粒细胞无形体病（HGA）。A.嗜吞噬细胞菌将其宿主嗜中性粒细胞转化为特洛伊木马，促进病原体复制和传播。该细菌下调中性粒细胞的抗菌反应，增加对机会性感染的易感性。封锁A。嗜吞噬细胞菌感染 中性粒细胞的增加将阻止与病原体传播和机会性感染风险增加相关的HGA阶段。A.嗜吞噬细胞菌感染心脏和肝脏的微血管内皮细胞。内皮细胞也被认为是A.嗜吞噬细胞菌在接种后通过蜱喂食感染。感染的内皮细胞能够将细菌转移到中性粒细胞。废除A.嗜吞噬细胞菌对内皮细胞的侵袭可能会阻止主要器官的感染和感染的初始建立。本项目的总体目标是在功能上表征A。嗜吞噬细胞菌释放出促进感染的膜蛋白。我们鉴定出外膜蛋白A（OmpA）和Asp 14（14-kDa Ap表面蛋白）是前两个A.嗜吞噬细胞的蛋白质是骨髓和内皮细胞的入侵的关键。靶向OmpA和Asp 14几乎消除了A.嗜吞噬细胞菌感染宿主细胞。在目标1中，我们将鉴定介导A的OmpA和Asp 14结构域。嗜吞噬细胞摄取，并确定任一蛋白是否足以入侵。在目标2中，我们将鉴定OmpA和Asp 14的宿主细胞受体。在目标3中，我们将使用新型转基因A.可以诱导表达针对ompA或Asp 14的反义RNA以敲低OmpA或Asp 14表达的嗜吞噬细胞菌生物。这项研究将提供一个强大的理解A。嗜吞噬细胞菌的细胞入侵，并确定任何无形体科病原体的前两个入侵素受体对。由于OmpA和Asp 14在几种立克次体病原体中是保守的，我们的工作将为针对导致HGA和其他衰弱性疾病的细菌子集的疫苗开发提供方向。最后，我们的工作将产生一个有价值的工具，用于评估专性细胞内细菌的基因功能。

DESCRIPTION (provided by applicant): Anaplasma phagocytophilum is an obligate intracellular bacterium and rickettsial pathogen that invades neutrophils and endothelial cells to cause the emerging and potentially fatal infection, human granulocytic anaplasmosis (HGA). A. phagocytophilum converts its host neutrophil into a Trojan horse that facilitates pathogen replication and dissemination. The bacterium down-regulates the neutrophil antimicrobial response, raising susceptibility to opportunistic infections. Blocking A. phagocytophilum infection of neutrophils would prevent the stage of HGA associated with pathogen dissemination and increased risk of opportunistic infections. A. phagocytophilum infects microvascular endothelial cells of heart and liver. Endothelial cells are also implicated as the initial cell type that A. phagocytophilum infects following inoculation via tick feeding. Infected endothelial cells are capable of transferring the bacterium to neutrophils. Abrogating A. phagocytophilum invasion of endothelial cells would potentially prevent infection of major organs and initial establishment of infection. The overall goal of this project is to functionally characterize A. phagocytophilum oute membrane proteins that facilitate infection. We identified outer membrane protein A (OmpA) and Asp14 (14-kDa Ap surface protein) as the first two A. phagocytophilum proteins that are critical for invasion of myeloid and endothelial cells. Targeting OmpA and Asp14 nearly abolishes A. phagocytophilum infection of host cells. In Aim 1, we will identify the OmpA and Asp14 domains that mediate A. phagocytophilum uptake and determine if either protein is sufficient for invasion. In Aim 2, we will identify the host cell receptors of OmpA and Asp14. In Aim 3, we will directly assess the relevance of OmpA and Asp14 to infectivity using novel transgenic A. phagocytophilum organisms that can be induced to express antisense RNA against ompA or asp14 to knock down OmpA or Asp14 expression. This research will provide a robust understanding of A. phagocytophilum cellular invasion and identify the first two invasin-receptor pairs for any Anaplasmataceae pathogen. As OmpA and Asp14 are conserved among several rickettsial pathogens, our work will provide direction for vaccine development against a subset of bacteria that causes HGA and other debilitating diseases. Lastly, our work will yield a valuable tool for assessing gene function in obligate intracellular bacteria.