Host control mechanisms against K. pneumoniae infection in the lungs

项目摘要/摘要：革兰氏阴性菌引起的急性下呼吸道感染是常见的 影响住院患者的问题，以及重症监护病房中最常见的感染 国际吧全球出现多重耐药、产碳青霉烯酶的克雷伯菌属菌株 肺炎杆菌（KP）是一种胞外革兰氏阴性菌，与显著的发病率和死亡率相关 这不成比例地影响老年患者、癌症患者、免疫功能低下者和重症患者。KP 感染也是亚洲和非洲部分地区社区获得性侵入性综合征的根源。一个关键的差距， 关于巨噬细胞，前哨免疫细胞如何在组织内战略性定位的知识 环境如肺，增强宿主对入侵病原体如KP的防御。超出 宿主巨噬细胞最初被模式识别受体（例如TLR 4）识别时，必须协调 大量由细菌外部触发的信号并执行有效的吞噬程序， 细胞因子应答和病原体消除。我们最近发现，CD 36，一种清道夫受体， 内源性DAMP如oxLDL的氧化磷脂酰胆碱或淀粉样β肽，提供宿主 通过增强LPS反应性和巨噬细胞对KP肺内感染的保护作用 是宿主存活、肺细菌负荷、肺外 传播、吞噬作用和炎性细胞因子反应。虽然CD 36功能突变是 在社区获得性侵袭性KP综合征流行的某些人群中发现， 关于在分子水平上防御该病原体的宿主控制机制知之甚少， 是前进的关键障碍广泛的长期目标是确定不同的宿主决定因素 控制K。肺炎（KP）感染。我们的主要假设是，CD 36在近端肿瘤中起关键作用。 控制巨噬细胞效应细胞因子应答和吞噬作用以增强宿主对K. 肺炎在肺部。我们的初步研究结果表明，CD 36放大巨噬细胞干扰素 通过诱导碱性亮氨酸拉链转录因子ATF样2（Batf 2）来促进细胞凋亡， 有效细胞因子应答和吞噬程序。根据这些发现，我们提出以下建议 目的是利用遗传缺陷小鼠、原代细胞和KP临床分离株，（1）通过以下途径鉴定机制： CD 36和BATF 2增强下游巨噬细胞效应细胞因子反应，（2）评估 上游分子事件，其定位CD 36以使用多药物最佳吞噬和杀死KP 来自ICU的耐药临床分离株，和（3）检查BATF 2和干扰素调节因子的作用 体内急性肺内感染期间的相互作用。成功完成目标将阐明 新的宿主控制机制，并有助于了解KP感染的长期目标， 易感宿主进行合理的靶向治疗设计。

Project Summary/Abstract: Acute lower respiratory tract infection from gram negative bacteria is a common problem affecting hospitalized patients, and the most common infection encountered in intensive care units worldwide. The global emergence of multidrug-resistant, carbapenemase-producing strains of Klebsiella pneumoniae (KP), an extracellular gram negative bacteria, is associated with significant morbidity and mortality that disproportionately affects older patients, cancer patients, the immunocompromised, and the critically ill. KP infection is also the root of community-acquired invasive syndrome in parts of Asia and Africa. A critical gap in knowledge exists in how macrophages, sentinel immune cells positioned strategically within tissue environments such as the lung, augments host defense against invading pathogen such as KP. Beyond the initial recognition by pattern recognition receptors such as TLR4, the host macrophage must coordinate a multitude of externally-triggered signals by the bacteria and execute an effective program of engulfment, cytokine response, and pathogen elimination. We recently showed that CD36, a scavenger receptor that binds endogenous DAMPs such as oxidized phosphatidylcholine of oxLDL or amyloid β peptides, provides host protection against KP intrapulmonary infection by enhancing LPS responsiveness and macrophage phagocytosis and is a critical determinant of host survival, lung bacterial burden, extrapulmonary dissemination, phagocytosis and inflammatory cytokine response. Although CD36 functional mutations are found in certain human populations where community-acquired invasive KP syndromes prevail, remarkably little is known about host control mechanisms that defend against this pathogen on a molecular level and this presents a critical barrier to progress. The broad, long term objective is to define distinct host determinants that control K. pneumoniae (KP) infection. Our major hypothesis is that the CD36 is pivotal in the proximal control of macrophage effector cytokine responses and phagocytosis to amplify host defense against K. pneumoniae in the lungs. Our preliminary findings suggest that CD36 amplifies macrophage interferon response through the induction of the basic leucine zipper transcription factor ATF-like 2 (Batf2) to promote an effective cytokine response and phagocytic program. Based upon these findings, we propose the following aims utilizing genetically deficient mice, primary cells, and KP clinical isolates to (1) identify the mechanism by which CD36 and BATF2 enhances downstream macrophage effector cytokine response, (2) evaluate the upstream molecular events that position CD36 for optimal phagocytosis and killing of KP using multi-drug resistant clinical isolates from the ICU, and (3) examine the role of BATF2 and interferon regulatory factor interactions during acute intrapulmonary infection in vivo. Successful completion of the aims will elucidate novel mechanisms of host control and aid in the long-term objective of understanding KP infection in susceptible hosts for rational, targeted therapy design.