Petzke Mary M, Brooks Andrew, Krupna Michelle A, Mordue Dana, Schwartz Ira
Department of Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA.
J Immunol. 2009 Oct 15;183(8):5279-92. doi: 10.4049/jimmunol.0901390. Epub 2009 Sep 30.
Borrelia burgdorferi is the spirochetal agent of Lyme disease, a multisystemic disorder characterized by inflammation. Using global transcriptional profiling, we characterized the response of human PBMCs exposed to B. burgdorferi in an ex vivo coculture system. The expression profiles induced by B. burgdorferi were marked by the intense up-regulation of IFN-responsive transcripts and transcripts involved in the JAK/STAT signaling pathway. Transcript levels of IFN-alpha, IFN-beta, and IRF7, and protein concentrations of IFN-alpha, were significantly elevated relative to those in unstimulated PBMCs. The induction of IFN-alpha was completely dependent upon phagocytosis of B. burgdorferi. Addition of a soluble type I IFN receptor, B18R, did not abolish the induction of IFN-inducible genes, indicating that B. burgdorferi directly elicits enhanced expression of these genes independently of type I IFN feedback signaling. Inhibitors of either TLR7 or TLR9 significantly reduced B. burgdorferi-stimulated IFN-alpha protein expression and transcription of IFN-induced genes. Simultaneous inhibition of both TLR7 and TLR9 completely abrogated IFN-alpha induction. The IFN-alpha-producing populations in PBMCs were identified as plasmacytoid dendritic and CD14(+)CD11c(+) cells. These results reveal a TLR7/9-dependent signaling pathway used by human PBMCs to initiate a type I IFN response to the extracellular bacterium B. burgdorferi.
伯氏疏螺旋体是莱姆病的螺旋体病原体，莱姆病是一种以炎症为特征的多系统疾病。我们利用全基因组转录谱分析，在体外共培养系统中对暴露于伯氏疏螺旋体的人外周血单核细胞（PBMCs）的反应进行了表征。伯氏疏螺旋体诱导的表达谱以IFN反应性转录本和参与JAK/STAT信号通路的转录本的强烈上调为特征。与未刺激的PBMCs相比，IFN-α、IFN-β和IRF7的转录水平以及IFN-α的蛋白浓度显著升高。IFN-α的诱导完全依赖于伯氏疏螺旋体的吞噬作用。添加可溶性I型IFN受体B18R并没有消除IFN诱导基因的诱导，这表明伯氏疏螺旋体直接引发这些基因的增强表达，而不依赖于I型IFN反馈信号。TLR7或TLR9的抑制剂显著降低了伯氏疏螺旋体刺激的IFN-α蛋白表达和IFN诱导基因的转录。同时抑制TLR7和TLR9完全消除了IFN-α的诱导。PBMCs中产生IFN-α的细胞群体被鉴定为浆细胞样树突状细胞和CD14(+)CD11c(+)细胞。这些结果揭示了人PBMCs用于启动对细胞外细菌伯氏疏螺旋体的I型IFN反应的TLR7/9依赖性信号通路。
