Sobotta Katharina, Hillarius Kirstin, Mager Marvin, Kerner Katharina, Heydel Carsten, Menge Christian
Friedrich-Loeffler-Institut (FLI), Institute of Molecular Pathogenesis, Jena, Germany.
Institute for Hygiene and Infectious Diseases of Animals, Justus-Liebig-University (JLU), Giessen, Germany.
Infect Immun. 2016 May 24;84(6):1722-1734. doi: 10.1128/IAI.01208-15. Print 2016 Jun.
Although domestic ruminants have long been recognized as the main source of human Q fever, little is known about the lifestyle that the obligate intracellular Gram-negative bacterium Coxiella burnetii adopts in its animal host. Because macrophages are considered natural target cells of the pathogen, we established primary bovine monocyte-derived macrophages (MDM) as an in vitro infection model to study reservoir host-pathogen interactions at the cellular level. In addition, bovine alveolar macrophages were included to take cell type peculiarities at a host entry site into account. Cell cultures were inoculated with the virulent strain Nine Mile I (NMI; phase I) or the avirulent strain Nine Mile II (NMII; phase II). Macrophages from both sources internalized NMI and NMII. MDM were particularly permissive for NMI internalization, but NMI and NMII replicated with similar kinetics in these cells. MDM responded to inoculation with a general upregulation of Th1-related cytokines such as interleukin-1β (IL-1β), IL-12, and tumor necrosis factor alpha (TNF-α) early on (3 h postinfection). However, inflammatory responses rapidly declined when C. burnetii replication started. C. burnetii infection inhibited translation and release of IL-1β and vastly failed to stimulate increased expression of activation markers, such as CD40, CD80, CD86, and major histocompatibility complex (MHC) molecules. Such capability of limiting proinflammatory responses may help Coxiella to protect itself from clearance by the host immune system. The findings provide the first detailed insight into C. burnetii-macrophage interactions in ruminants and may serve as a basis for assessing the virulence and the host adaptation of C. burnetii strains.
尽管家畜长期以来一直被认为是人类Q热的主要来源，但对于专性细胞内革兰氏阴性菌伯纳特柯克斯体在其动物宿主中的生活方式却知之甚少。由于巨噬细胞被认为是该病原体的天然靶细胞，我们建立了原代牛单核细胞衍生巨噬细胞（MDM）作为体外感染模型，以在细胞水平上研究储存宿主与病原体之间的相互作用。此外，还纳入了牛肺泡巨噬细胞，以考虑宿主进入部位的细胞类型特性。细胞培养物接种了强毒株九英里I（NMI；I期）或无毒株九英里II（NMII；II期）。来自这两种来源的巨噬细胞都内化了NMI和NMII。MDM对NMI内化特别敏感，但NMI和NMII在这些细胞中的复制动力学相似。MDM在感染早期（感染后3小时）对接种的反应是Th1相关细胞因子如白细胞介素-1β（IL-1β）、IL-12和肿瘤坏死因子α（TNF-α）普遍上调。然而，当伯纳特柯克斯体开始复制时，炎症反应迅速下降。伯纳特柯克斯体感染抑制了IL-1β的翻译和释放，并且极大地未能刺激激活标志物如CD40、CD80、CD86和主要组织相容性复合体（MHC）分子表达的增加。这种限制促炎反应的能力可能有助于柯克斯体保护自己免受宿主免疫系统的清除。这些发现首次详细揭示了反刍动物中伯纳特柯克斯体与巨噬细胞的相互作用，并可能作为评估伯纳特柯克斯体菌株毒力和宿主适应性的基础。
