Host-mediated zinc sequestration during Acinetobacter baumannii infection

描述（由申请方提供）：鲍曼不动杆菌是一种重要的院内病原体，可引起一系列疾病，包括呼吸道和泌尿道感染、脑膜炎、心内膜炎、伤口感染和菌血症。事实上，A.鲍曼不动杆菌现在是世界上某些地区所有重症监护室感染的20%的原因，其中肺炎是最常见的表现。探讨了A.鲍曼不动杆菌是由这种微生物迅速获得对几乎所有抗生素的耐药性而引起的。的 确定治疗干预的新靶点对我们保护公共卫生免受这种新出现的传染病威胁的能力至关重要。治疗发展的一个有希望的潜在领域涉及靶向细菌获得营养金属。这一策略是基于这样一个事实，即所有细菌病原体都需要营养金属才能在其宿主中定植。尽管脊椎动物体内细菌病原体在生长期间需要多种金属，但铁螯合被认为是宿主在对感染的先天免疫应答期间主动螯合的主要营养素。在本申请中，我们提供了先天免疫因子钙卫蛋白通过螯合营养锌（Zn）来防御肺炎不动杆菌的证据。以钙卫蛋白为探针，我们鉴定了A.与钙卫蛋白竞争锌，并由锌依赖性调节因子转录控制的鲍曼不动杆菌。钙卫蛋白在炎症部位大量存在，是一种已知的促炎分子，是晚期糖基化终末产物受体（AGEs）的配体。尽管其明确的参与，钙卫蛋白介导的金属螯合和结合防御感染的贡献还没有得到彻底的评估。基于本申请中描述的初步数据，我们假设钙卫蛋白介导的锌螯合和锌结合是宿主-病原体相互作用期间的关键因素。为了验证这一中心假设，我们提出了一系列实验，旨在了解钙卫蛋白介导的锌螯合和锌结合在A.鲍氏肺炎。在这些研究中，我们将（i）确定钙卫蛋白的结构特征，使其能够螯合过渡金属，如锌和结合钙，（ii）阐明钙卫蛋白和钙对A的影响。鲍曼不动杆菌的发病机制，以及（iii）确定CP介导的锌螯合作用对鲍曼不动杆菌生理的影响。鲍曼不动杆菌。这些结果将为A.鲍曼不动杆菌在脊椎动物宿主中获得营养，并为基于钙卫蛋白支架的肽治疗剂的产生奠定了基础，所述钙卫蛋白支架通过营养金属螯合抑制微生物生长。

DESCRIPTION (provided by applicant): Acinetobacter baumannii is an important nosocomial pathogen that causes a range of diseases, including respiratory and urinary tract infections, meningitis, endocarditis, wound infections, and bacteremia. In fact, A. baumannii is now responsible for up to 20% of all intensive care unit infections in some regions of the world with pneumonia being the most common presentation. The clinical significance of A. baumannii has been propelled by this organism's rapid acquisition of resistance to virtually all antibiotics. The identification of novel targets for therapeutic intervention is critical to our ability to protect he public health from this emerging infectious threat. One promising potential area of therapeutic development involves targeting bacterial access to nutrient metal. This strategy is based on the fact that all bacterial pathogens require nutrient metal in order to colonize their hosts. Despite the fact that a variety of metals are required by bacterial pathogens during growth within vertebrates, iron sequestration is considered to be the primary nutrient that is actively sequestered by the host during the innate immune response to infection. In the present application, we provide evidence that the innate immune factor calprotectin defends against Acinetobacter pneumonia by chelating nutrient zinc (Zn). Using calprotectin as a probe, we have identified a transport system in A. baumannii that competes with calprotectin for Zn and is transcriptionally controlled by a Zn-dependent regulator. Calprotectin is abundant at sites of inflammation and is a known pro- inflammatory molecule that is a ligand for the receptor for advanced glycation end products (RAGE). Despite its clear involvement, the contributions of calprotectin-mediated metal sequestration and RAGE binding to defense against infection have not been thoroughly evaluated. Based on preliminary data described in this application, we hypothesize that calprotectin-mediated Zn sequestration and RAGE binding are critical factors during the host-pathogen interaction. To test this central hypothesis, we propose a series of experiments aimed at understanding the mechanism and pathophysiological consequence of calprotectin-mediated Zn sequestration and RAGE binding during A. baumannii pneumonia. In these studies, we will (i) identify the structural features of calprotectin that enable it to chelae transition metals such as Zn and to bind RAGE, (ii) elucidate the impact of calprotectin and RAGE on A. baumannii pathogenesis, and (iii) determine the impact of CP-mediated Zn chelation on the physiology of A. baumannii. These results will provide fundamental insight into how A. baumannii acquires nutrients in the vertebrate host, and lay the foundation for the creation of peptide therapeutics based on a calprotectin scaffold that inhibit microbial growth through nutrient metal chelation.