Toll-like receptor 2-mediated dendritic cell activation by a Porphyromonas gingivalis synthetic lipopeptide

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Abstract
A PG1828 gene-encoded triacylated lipoprotein was previously isolated from aPorphyromonas gingivalislipopolysaccharide preparation as a Toll-like receptor (TLR) 2 agonist and its lipopeptide derivatives were synthesized based on the chemical structure. In the present study, granulocyte–macrophage colony stimulating factor-differentiated bone marrow-derived dendritic cells (BMDDCs) were stimulated separately with theP. gingivalissynthetic lipopeptideN-palmitoyl-S-[2-pentadecanoyloxy, 3-palmitoyloxy-(2R)-propyl]-l-Cys-Asn-Ser-Gln-Ala-Lys (PGTP2-RL) and its glyceryl stereoisomer (PGTP2-SL). Only PGTP2-RL activated BMDDCs from wild-type mice to secrete tumour necrosis factor-α, interleukin (IL)-6, IL-10 and IL-12p40, whilst PGTP2-RL-induced cytokine production was eliminated in TLR2 knockout (−/−) BMDDCs. BMDDCs from wild-type mice but not TLR2−/−mice responded to PGTP2-RL as well as Pam3CSK4by increasing the expression of maturation markers, including CD80 (B7-1), CD86 (B7-2), CD40, CD275 (B7RP-1/inducible T-cell co-stimulatory ligand) and major histocompatibility complex class II. Taken together, these results indicate that the fatty acid residue at the glycerol position in theP. gingivalislipopeptide plays a pivotal role in TLR2-mediated dendritic cell activation.