Way Sing Sing, Thompson Lucas J, Lopes Jared E, Hajjar Adeline M, Kollmann Tobias R, Freitag Nancy E, Wilson Christopher B
Department of Pediatrics, University of Washington School of Medicine, 1959 NE Pacific Street, Box 357650, H564, Seattle, WA 98195, USA.
Cell Microbiol. 2004 Mar;6(3):235-42. doi: 10.1046/j.1462-5822.2004.00360.x.
Flagellin is the structural component of flagella produced by many pathogenic bacteria and is a potent proinflammatory molecule that mediates these effects through Toll-like receptor (TLR) 5. In Listeria monocytogenes (LM), flagellin expression is regulated by temperature and has been described as being shut off at 37 degrees C. In this study, we demonstrate that TLR5-mediated cell activation and flagellin expression is maintained at 37 degrees C in some laboratory-adapted strains and in approximately 20% of LM clinical isolates. To determine the role of flagellin in LM infection, a targeted mutation in the structural gene for flagellin (flaA) was generated in a parental LM strain that expressed flagellin under all conditions examined. In vitro studies demonstrated that this deltaflaA mutant was (i). non-motile; (ii). not able to activate TLR5-transfected HeLa cells; and (iii). induced tumour necrosis factor (TNF)-alpha production in approximately 50% fewer CD11b+ cells in splenocytes from normal mice compared with the parental strain. However, there was no significant alteration in virulence of the deltaflaA mutant after either intravenous or oral murine infection. Similarly, there was no difference in the generation of LM-specific CD8 or CD4 T cells after intravenous or oral infection. These data indicate that flagellin is not essential for LM pathogenesis or for the induction of LM-specific adaptive immune responses in normal mice.
鞭毛蛋白是许多致病细菌产生的鞭毛的结构成分，是一种强效促炎分子，通过Toll样受体（TLR）5介导这些效应。在单核细胞增生李斯特菌（LM）中，鞭毛蛋白的表达受温度调节，据描述在37℃时会关闭。在本研究中，我们证明在一些实验室适应菌株和大约20%的LM临床分离株中，TLR5介导的细胞活化和鞭毛蛋白表达在37℃时得以维持。为了确定鞭毛蛋白在LM感染中的作用，我们在一个在所有检测条件下都表达鞭毛蛋白的亲代LM菌株中，对鞭毛蛋白（flaA）的结构基因进行了靶向突变。体外研究表明，这个ΔflaA突变体：（i）无运动能力；（ii）不能激活转染了TLR5的HeLa细胞；（iii）与亲代菌株相比，在正常小鼠脾细胞中诱导肿瘤坏死因子（TNF）-α产生的CD11b+细胞减少了约50%。然而，在静脉内或口服小鼠感染后，ΔflaA突变体的毒力没有显著变化。同样，在静脉内或口服感染后，产生LM特异性CD8或CD4 T细胞方面也没有差异。这些数据表明，鞭毛蛋白对于正常小鼠的LM发病机制或诱导LM特异性适应性免疫反应并非必不可少。
