Francisella tularensis LPS induces the production of cytokines in human monocytes and signals via Toll-like receptor 4 with much lower potency than E. coli LPS

• Published in: International immunology 2006-05, Vol.18 (5), p.785-795
• Main Authors: Dueñas, Ana I, Aceves, Mónica, Orduña, Antonio, Díaz, Ramón, Sánchez Crespo, Mariano, García-Rodríguez, Carmen
• Format: Article
• Language: English
• Subjects: Chemokine CCL2 - biosynthesis; Chemokine CCL2 - genetics; Chemokine CCL2 - immunology; Chemokine CCL4; Cytokines - biosynthesis; Cytokines - genetics; Cytokines - immunology; Data Interpretation, Statistical; Escherichia coli; Escherichia coli - genetics; Escherichia coli - immunology; Francisella tularensis; Francisella tularensis - immunology; Gene Expression - drug effects; Humans; Interleukin-8 - biosynthesis; Interleukin-8 - genetics; Interleukin-8 - immunology; Lipopolysaccharides - immunology; Lipopolysaccharides - pharmacology; Macrophage Inflammatory Proteins - biosynthesis; Macrophage Inflammatory Proteins - genetics; Macrophage Inflammatory Proteins - immunology; Mitogen-Activated Protein Kinase 3 - metabolism; Monocytes - drug effects; Monocytes - immunology; NF-kappa B - genetics; RNA, Messenger - biosynthesis; RNA, Messenger - genetics; Toll-Like Receptor 2 - immunology; Toll-Like Receptor 2 - metabolism; Toll-Like Receptor 4 - immunology; Toll-Like Receptor 4 - metabolism
• ISSN: 0953-8178; 1460-2377
• DOI: 10.1093/intimm/dxl015

Francisella tularensis is a virulent Gram-negative intracellular pathogen. To address the signaling routes involved in the response of host cells to LPS from F. tularensis live vaccine strain (LVS), experiments were performed in transiently transfected 293 cells. Induction of kappaB-driven transcriptional activity by 2.5 mug ml(-1) F. tularensis LPS isolated by phenol-water and ether-water extraction, was observed in cells transfected with Toll-like receptor (TLR) 4 and MD-2, although CD14 was required for optimal induction. Conversely, TLR2, TLR2/TLR1 or TLR2/TLR6 transfected cells did not show kappaB-driven transcriptional activity in the presence of F. tularensis LPS. In human monocytic cells, F. tularensis LPS activated extracellular signal-regulated kinases and the production of pro-inflammatory proteins. Concentrations of 5-10 mug ml(-1) F. tularensis LPS elicited a similar pattern of mRNA and protein induction than 0.1 mug ml(-1) E. coli LPS, including the expression of CXC chemokines (IL-8, Gro and IFN-gamma-inducible protein-10); CC chemokines (monocyte chemoattractant protein-1 and -2, macrophage-derived chemoattractant, macrophage inflammatory protein-1alpha and -1beta and RANTES (regulated upon activation, normal T cell expressed and secreted) and pro-inflammatory cytokines (IL-6 and tumor necrosis factor alpha). Altogether, these data indicate that LPS from F. tularensis LVS signals via TLR4 at higher concentrations than those required for E. coli LPS, which may explain the inflammatory reaction and the low endotoxic response associated to vaccination with LVS in humans.