Lipopolysaccharides of Bacteroides fragilis, Chlamydia trachomatis and Pseudomonas aeruginosa signal via Toll-like receptor 2

1 Medical Microbiology, Centre for Infectious Diseases, University of Edinburgh, Teviot Place, Edinburgh EH8 9AG, UK 2 Division of Genomic Medicine, University of Sheffield Medical School, Sheffield S10 2RX, UK Correspondence Ian R. Poxton I.R.Poxton{at}ed.ac.uk Received January 15, 2004 Accepted March 17, 2004 Recognition of bacterial lipopolysaccharide (LPS) is critical in the host defence against Gram-negative infection. While enterobacterial LPS signals via Toll-like receptor 4 (TLR4), it has recently been reported that the LPS of Leptospira interrogans , Legionella pneumophila , Rhizobium species Sin-1 and at least one strain of Porphyromonas gingivalis are capable of signalling via TLR2. Using a TLR transfection assay and measurement of an NF- B-sensitive promoter region, the results show that the LPS of Bacteroides fragilis NCTC-9343, Chlamydia trachomatis LGV-1 and Pseudomonas aeruginosa PAC-611 also signal via TLR2 and it is pointed out that all TLR2-signalling LPS discovered to date demonstrate relatively weak endotoxicity in some models and structural features distinct from those LPS shown to signal via TLR4. Abbreviations: LPS, lipopolysaccharide; TLR, Toll-like receptor.