Dissemination of Orientia tsutsugamushi and Inflammatory Responses in a Murine Model of Scrub Typhus
Dissemination of Orientia tsutsugamushi and Inflammatory Responses in a Murine Model of Scrub Typhus
复制标题
DOI：
10.1371/journal.pntd.0003064
复制
发表时间：
2014-08-01
影响因子：
3.8
通讯作者：
Fleischer, Bernhard
中科院分区：
文献类型：
--
作者：
Keller, Christian A.;Hauptmann, Matthias;Fleischer, Bernhard
恙虫病是一种由恙虫病东方体 (O.) 引起的感染，其发病机制的主要方面仍不清楚。人们对它的器官和细胞向性知之甚少。本研究的目的是分析实验性斑疹伤寒小鼠模型感染人类致病菌株卡普后感染组织中细菌传播的动力学和相关炎症反应。我们使用足垫接种对近交 Balb/c 小鼠的恙虫病感染进行了全面分析，这接近于自然感染方式。通过针对多拷贝 traD 基因的新颖、高灵敏度 qPCR，我们定量监测了恙虫病卡普氏体从皮肤接种部位经区域淋巴结到内部靶器官的扩散。在肺部测量到最高的细菌负荷。使用共聚焦成像，我们还在肺部的单细胞水平上检测到恙虫病原体，并发现主要定位于巨噬细胞而不是内皮细胞。对肺和脑浸润的免疫组织化学分析揭示了具有特定定位的不同组成的病变：表达 iNOS 的巨噬细胞在浸润性实质结节中常见，但在这些器官内的血管周围病变中不常见。通过免疫组织化学对肝脏、心脏、肺和大脑中的巨噬细胞反应进行定量分析表明，肝脏中巨噬细胞活化早期开始。急性感染期间干扰素 (IFN)-γ 的血清水平升高，我们发现 IFN-γ 有助于 iNOS 依赖性细菌生长控制。我们的数据表明，一旦接种到皮肤，恙虫病就会全身扩散到大量器官，并引起器官特异性炎症模式。研究结果表明，肺在恙虫病的发病机制中发挥着重要作用。该模型将允许对宿主与病原体相互作用进行详细研究，并进一步深入了解恙虫病感染的发病机制。
Central aspects in the pathogenesis of scrub typhus, an infection caused by Orientia (O.) tsutsugamushi, have remained obscure. Its organ and cellular tropism are poorly understood. The purpose of this study was to analyze the kinetics of bacterial dissemination and associated inflammatory responses in infected tissues in an experimental scrub typhus mouse model, following infection with the human pathogenic strain Karp. We provide a thorough analysis of O. tsutsugamushi infection in inbred Balb/c mice using footpad inoculation, which is close to the natural way of infection. By a novel, highly sensitive qPCR targeting the multi copy traD genes, we quantitatively monitored the spread of O. tsutsugamushi Karp from the skin inoculation site via the regional lymph node to the internal target organs. The highest bacterial loads were measured in the lung. Using confocal imaging, we also detected O. tsutsugamushi at the single cell level in the lung and found a predominant macrophage rather than endothelial localization. Immunohistochemical analysis of infiltrates in lung and brain revealed differently composed lesions with specific localizations: iNOS-expressing macrophages were frequent in infiltrative parenchymal noduli, but uncommon in perivascular lesions within these organs. Quantitative analysis of the macrophage response by immunohistochemistry in liver, heart, lung and brain demonstrated an early onset of macrophage activation in the liver. Serum levels of interferon (IFN)-gamma were increased during the acute infection, and we showed that IFN-gamma contributed to iNOS-dependent bacterial growth control. Our data show that upon inoculation to the skin, O. tsutsugamushi spreads systemically to a large number of organs and gives rise to organ-specific inflammation patterns. The findings suggest an essential role for the lung in the pathogenesis of scrub typhus. The model will allow detailed studies on host-pathogen interaction and provide further insight into the pathogenesis of O. tsutsugamushi infection.