Gao L Y, Stone B J, Brieland J K, Abu Kwaik Y
Department of Microbiology and Immunology, University of Kentucky Chandler Medical Center, Lexington, KY, 40536-0084, USA.
Microb Pathog. 1998 Dec;25(6):291-306. doi: 10.1006/mpat.1998.0237.
Alveolar epithelial cells, which constitute the majority of the alveolar surface, may represent a potential niche for intracellular replication of Legionella pneumophila that has been largely overlooked. We examined the phenotypes of a bank of 121 macrophage-defective mutants of L. pneumophila (designated as pmi and mil) for their cytopathogenicity to and intracellular survival and replication within human alveolar epithelial cells. Our data showed that 91 of 121 mutants that were defective (modest-severe) in macrophages exhibited wild type-like phenotypes in human type I alveolar epithelial cells. In contrast, the other 30 mutants were defective in both macrophages and alveolar epithelial cells. Transmission electron microscopy of the intracellular infection by three mutants showed that the defect in intracellular replication in macrophages and epithelial cells was associated with a defect in recruitment of the RER around the phagosome. Differences in attachment to macrophages and epithelial cells were also exhibited by some of the mutants. Pulmonary infection studies of A/J mice showed that a mutant defective in macrophages but not in alveolar epithelial cells replicated like the wild type strain in the lungs of A/J mice. In contrast, a mutant defective in both macrophages and alveolar epithelial cells failed to replicate and was killed. We conclude that certain distinct genetic loci of L. pneumophila are uniquely required for intracellular survival and replication within phagocytic but not epithelial cells, which may be important in vivo.
构成肺泡表面大部分的肺泡上皮细胞，可能是嗜肺军团菌细胞内复制的一个潜在微环境，但这在很大程度上被忽视了。我们检测了一组121个嗜肺军团菌巨噬细胞缺陷突变体（命名为pmi和mil）对人肺泡上皮细胞的细胞致病性以及在细胞内的存活和复制情况。我们的数据显示，121个在巨噬细胞中存在缺陷（中度-重度）的突变体中，有91个在人I型肺泡上皮细胞中表现出野生型样的表型。相反，另外30个突变体在巨噬细胞和肺泡上皮细胞中均存在缺陷。对三个突变体进行细胞内感染的透射电子显微镜观察显示，巨噬细胞和上皮细胞中细胞内复制的缺陷与吞噬体周围粗面内质网募集的缺陷有关。一些突变体在与巨噬细胞和上皮细胞的附着方面也存在差异。对A/J小鼠进行的肺部感染研究表明，一个在巨噬细胞中存在缺陷但在肺泡上皮细胞中无缺陷的突变体，在A/J小鼠肺部的复制情况与野生型菌株相似。相反，一个在巨噬细胞和肺泡上皮细胞中均存在缺陷的突变体无法复制并被清除。我们得出结论，嗜肺军团菌的某些特定基因位点是其在吞噬细胞而非上皮细胞内生存和复制所独特需要的，这在体内可能很重要。
