Influence of periodontal disease, Porphyromonas gingivalis and cigarette smoking on systemic anti-citrullinated peptide antibody titres

Background: Anti-citrullinated protein antibody (ACPA) responses may precede clinical onset of rheumatoid arthritis. Porphyromonas gingivalis peptidylarginine deiminase can citrullinate proteins possibly inducing autoimmunity in susceptible individuals. Aim: To determine whether periodontitis, carriage of P. gingivalis, smoking and periodontal therapy influence ACPA titres. Methods: Serum and plaque samples were collected from 39 periodontitis patients before and after non-surgical periodontal treatment, and from 36 healthy subjects. Carriage of P. gingivalis was determined by PCR of plaque DNA. ACPA was determined by anti-cyclic citrullinated peptide (CCP) enzyme-linked immunosorbent assay (ELISA). Anti-P. gingivalis titres were determined by ELISA. Results: Untreated periodontitis patients had higher anti-CCP antibody titres than healthy controls [three patients (8%) greater than manufacturer suggested assay diagnostic threshold (5 Assay Units/AU) versus none (0%); mean +/- SEM: 1.37 +/- 0.23 versus 0.40 +/- 0.10AU, p<0.0001]. Periodontitis patients who smoked demonstrated lower anti-P. gingivalis (15956 +/- 4385 versus 2512 +/- 1290Units/ml, p<0.05), but similar anti-CCP than non-smoking periodontitis patients (smokers: 1.31 +/- 0.35; non-smokers: 1.41 +/- 0.32AU). Healthy smokers demonstrated elevated anti-CCP titres (0.75 +/- 0.19AU), at levels between healthy non-smokers (0.15 +/- 0.05AU) and non-smoker periodontitis patients. Six months after periodontal treatment, there were significant reductions in anti-CCP (non-smokers p<0.05) and anti-P. gingivalis (all participants p<0.01). Conclusion: In subjects with periodontitis, P. gingivalis infection may be responsible for inducing autoimmune responses that characterize rheumatoid arthritis.