Coxiella Pathogenesis Section, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA.
Infect Immun. 2010 Aug;78(8):3465-74. doi: 10.1128/IAI.00406-10. Epub 2010 Jun 1.
Coxiella burnetii infects mononuclear phagocytes, where it directs biogenesis of a vacuolar niche termed the parasitophorous vacuole (PV). Owing to its lumenal pH (approximately 5) and fusion with endolysosomal vesicles, the PV is considered phagolysosome-like. However, the degradative properties of the mature PV are unknown, and there are conflicting reports on the maturation state and growth permissiveness of PV harboring virulent phase I or avirulent phase II C. burnetii variants in human mononuclear phagocytes. Here, we employed infection of primary human monocyte-derived macrophages (HMDMs) and THP-1 cells as host cells to directly compare the PV maturation kinetics and pathogen growth in cells infected with the Nine Mile phase I variant (NMI) or phase II variant (NMII) of C. burnetii. In both cell types, phase variants replicated with similar kinetics, achieving roughly 2 to 3 log units of growth before they reached stationary phase. HMDMs infected by either phase variant secreted similar amounts of the proinflammatory cytokines interleukin-6 and tumor necrosis factor alpha. In infected THP-1 cells, equal percentages of NMI and NMII PVs decorate with the early endosomal marker Rab5, the late endosomal/lysosomal markers Rab7 and CD63, and the lysosomal marker cathepsin D at early (8 h) and late (72 h) time points postinfection (p.i.). Mature PVs (2 to 4 days p.i.) harboring NMI or NMII contained proteolytically active cathepsins and quickly degraded Escherichia coli. These data suggest that C. burnetii does not actively inhibit phagolysosome function as a survival mechanism. Instead, NMI and NMII resist degradation to replicate in indistinguishable digestive PVs that fully mature through the endolysosomal pathway.
贝氏考克斯体感染单核吞噬细胞，在那里它指导称为寄生空泡（PV）的空泡生物发生。由于其腔内腔（约 5）和与内溶酶体小泡融合，PV 被认为类似于吞噬溶酶体。然而，成熟 PV 的降解特性尚不清楚，并且在含有毒力相 I 或无毒相 II C 的单核吞噬细胞中，关于 PV 成熟状态和生长许可性的报告存在矛盾。burnetii 变体。在这里，我们采用原代人单核细胞衍生的巨噬细胞（HMDM）和 THP-1 细胞的感染作为宿主细胞，直接比较感染九英里相 I 变体（NMI）或相 II 变体（NMII）的 PV 成熟动力学和病原体生长。在两种细胞类型中，相变体以相似的动力学复制，在达到静止期之前实现大约 2 到 3 个对数单位的生长。用任相变体感染的 HMDM 分泌相似量的促炎细胞因子白细胞介素 6 和肿瘤坏死因子-α。在感染的 THP-1 细胞中，NMI 和 NMII 的 PV 以相同的百分比用早期内体标记物 Rab5、晚期内体/溶酶体标记物 Rab7 和 CD63 以及溶酶体标记物组织蛋白酶 D 进行修饰在感染后早期（8 h）和晚期（72 h）时间点。（p.i.）。含有 NMI 或 NMII 的成熟 PV（2 至 4 天 p.i.）含有具有蛋白水解活性的组织蛋白酶，并迅速降解大肠杆菌。这些数据表明，贝氏考克斯体不会主动抑制吞噬溶酶体功能作为一种生存机制。相反，NMI 和 NMII 抵抗降解，在通过内溶酶体途径完全成熟的可区分的消化 PV 中复制。
