Identification of immunoreactive epitopes of the Porphyromonas gingivalis heat shock protein in periodontitis and atherosclerosis

Background and Objective: Heat shock protein 60 (HSP60) of Porphyromonas gingivalis, a major periodontal pathogen, might be a trigger molecule linking infectious periodontitis and autoimmune atherosclerosis. The aim of this study was to identify the peptide specificity of anti-P. gingivalis HSP60 monoclonal antibodies and their cross-reactivity with bacterial and human HSPs. Their specific immunoreactivity to periodontal or atherosclerotic lesions was also investigated. Methods: Twenty patients with chronic periodontitis and 20 atherosclerosis patients who had undergone surgical intervention for atheromatous plaques with evidence of ongoing periodontal disease, were selected. Synthetic peptide 19 ((TLVVNRLRGSLKICAVKAPG)-specific T-cell lines were established from inflamed gingiva and atheromatous plaque and the phenotypes and cytokine profiles were characterized. Results: Thirty per cent of periodontitis patients and 100% of atherosclerosis patients reacted positively to cross-reactive peptide 19 from both P. gingivalis and human HSP60. The peptide 19-specific T-cell lines demonstrated the phenotype characteristic of helper T cells (CD4+) but did not express CD25 or FOXP3. The interleukin-10 levels were elevated significantly in the peptide 19 T-cell line. Conclusion: Synthetic peptide 19 of P. gingivalis HSP60 is an immunoreactive epitope in the periodontitis-atherosclerosis axis.