An attenuated strain of the facultative intracellular bacterium Francisella tularensis can escape the phagosome of monocytic cells
An attenuated strain of the facultative intracellular bacterium Francisella tularensis can escape the phagosome of monocytic cells
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DOI：
10.1128/iai.71.10.5940-5950.2003
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发表时间：
2003-10-01
影响因子：
3.1
通讯作者：
Sjöstedt, A
中科院分区：
文献类型：
--
作者：
Golovliov, I;Baranov, V;Sjöstedt, A
兼性细胞内细菌土拉弗朗西斯菌是一种剧毒且具有传染性的生物，人们对其细胞内生存机制知之甚少。我们研究了人源疫苗株F.在粘附的小鼠腹膜细胞中、在小鼠巨噬细胞样细胞系J774A.1中和在人巨噬细胞系THP-1中。感染的J774A.1细胞的共聚焦显微镜检查表明，在感染的第一个小时内，细菌与晚期内体-溶酶体糖蛋白LAMP-1共定位，但在3小时内，这种共定位从约60%显著下降至30%。透射电子显微镜显示，>90%的细菌在感染2小时后没有被吞噬体膜包围，并且一些细菌处于仅部分被界膜包围的空泡中。用所有三种宿主细胞类型获得了类似的发现。免疫电子显微镜用F.土拉热菌LVS特异性多克隆兔抗血清显示，该抗血清在培养液中生长的细菌中染色出厚的、均匀分布的囊状物质。相反，胞内F.土拉热LVS细胞仅用该抗血清少量染色。相反，大多数的免疫反应性物质是弥漫性定位在吞噬体或与吞噬体膜。结果表明，F.土拉菌LVS能够通过可能涉及吞噬体膜降解的机制从巨噬细胞的吞噬体中逃逸。
The facultative intracellular bacterium Francisella tularensis is a highly virulent and contagious organism, and little is known about its intracellular survival mechanisms. We studied the intracellular localization of the attenuated human vaccine strain, F. tularensis LVS, in adherent mouse peritoneal cells, in mouse macrophage-like cell line J774A.1, and in human macrophage cell line THP-1. Confocal microscopy of infected J774A.1 cells indicated that during the first hour of infection the bacteria colocalized with the late endosomal-lysosomal glycoprotein LAMP-1, but within 3 h this colocalization decreased significantly from approximately 60% to 30%. Transmission electron microscopy revealed that >90% of bacteria were not enclosed by a phagosomal membrane after 2 h of infection, and some bacteria were in vacuoles that were only partially surrounded by a limiting membrane. Similar findings were obtained with all three host cell types. Immunoelectron microscopy performed with an F. tularensis LVS-specific polyclonal rabbit antiserum showed that the antiserum stained a thick, evenly distributed capsule-like material in bacteria grown in broth. In contrast, intracellular F. tularensis LVS cells were only marginally stained with this antiserum. Instead, most of the immunoreactive material was diffusely localized in the phagosomes or was associated with the phagosomal membrane. Our findings indicate that F. tularensis LVS is able to escape from the phagosomes of macrophages via a mechanism that may involve degradation of the phagosomal membrane.