Winter Sebastian E, Winter Maria G, Atluri Vidya, Poon Victor, Romão Everton L, Tsolis Renée M, Bäumler Andreas J
Department of Medical Microbiology and Immunology, School of Medicine, University of California, Davis, Davis, California, USA
Department of Medical Microbiology and Immunology, School of Medicine, University of California, Davis, Davis, California, USA.
Infect Immun. 2015 Apr;83(4):1546-55. doi: 10.1128/IAI.02803-14. Epub 2015 Feb 2.
To discern virulent from innocuous microbes, the innate immune system senses events associated with bacterial access to immunoprivileged sites such as the host cell cytosol. One such pathway is triggered by the cytosolic delivery of flagellin, the major subunit of the flagellum, by bacterial secretion systems. This leads to inflammasome activation and subsequent proinflammatory cell death (pyroptosis) of the infected phagocyte. In this study, we demonstrate that the causative agent of typhoid fever, Salmonella enterica serovar Typhi, can partially subvert this critical innate immune recognition event. The transcriptional regulator TviA, which is absent from Salmonella serovars associated with human gastroenteritis, repressed the expression of flagellin during infection of human macrophage-like (THP-1) cells. This mechanism allowed S. Typhi to dampen inflammasome activation, leading to reduced interleukin-1β (IL-1β) secretion and diminished cell death. Likewise, the introduction of the tviA gene in nontyphoidal Salmonella enterica serovar Typhimurium reduced flagellin-induced pyroptosis. These data suggest that gene regulation of virulence factors enables S. Typhi to evade innate immune recognition by concealing a pathogen-induced process from being sensed by the inflammasome.
为了区分有毒微生物和无害微生物,先天免疫系统会感知与细菌进入免疫特权部位(如宿主细胞胞质溶胶)相关的事件。其中一条途径是由细菌分泌系统将鞭毛的主要亚基鞭毛蛋白递送至胞质溶胶所触发的。这会导致炎性小体激活以及受感染吞噬细胞随后发生促炎性细胞死亡(细胞焦亡)。在本研究中,我们证明伤寒热的病原体伤寒沙门氏菌血清型伤寒杆菌能够部分颠覆这一关键的先天免疫识别事件。与人类肠胃炎相关的沙门氏菌血清型中不存在的转录调节因子TviA,在人类巨噬细胞样(THP-1)细胞感染期间抑制了鞭毛蛋白的表达。这种机制使伤寒杆菌能够抑制炎性小体激活,导致白细胞介素-1β(IL-1β)分泌减少和细胞死亡减轻。同样,在非伤寒性肠炎沙门氏菌血清型鼠伤寒杆菌中引入tviA基因可减少鞭毛蛋白诱导的细胞焦亡。这些数据表明,毒力因子的基因调控使伤寒杆菌能够通过将病原体诱导的过程隐藏起来不被炎性小体感知,从而逃避先天免疫识别。