Lipoprotein of Porphyromonas gingivalis

Objectives: Lipopolysaccharide (LPS) preparations derived from of Porphyromonas gingivalis (Pg-LPS) are thought to require Toll-like receptor (TLR)2 rather than TLR4, a receptor of Escherichia coli LPS (Ec-LPS), for activation of immune cells. Methods: A new lipoprotein (Pg-LP) was separated from a Pg-LPS by hydrophobic interaction chromatography followed by preparative electrophoresis. Results: We identified by internal peptide sequencing as PG1828, a putative lipoprotein encoded in the P. gingivalis genome. The N-terminal structure was characterized as a triacylated lipopeptide using mass spectrometry. Furthermore, Pg-LP exhibited strong cell activation similar to E. coli LPS through a Toll-like receptor 2-dependent pathway, and in order to determine the virulence of Pg-LP toward cell activation, we generated a PG1828-deficient mutant of P. gingivalis strain and a highly purified LPS preparation (ΔPG1828-LPS). The ability of the ΔPG1828-LPS to activate NF-κB in TLR2-expressing cells was markedly attenuated, and cytokine production by human gingival fibroblasts was also decreased in response to the ΔPG1828-LPS in comparison with a LPS from wild-type strain (WT-LPS). Furthermore, the ΔPG1828-LPS preparation showed no lethal toxicity. Conclusion: These results clearly indicate that Pg-LP plays an essential role in inflammatory responses and may be a major virulence factor of P. gingivalis.