Association between anti-Porphyromonas gingivalis or anti-α-enolase antibody and severity of periodontitis or rheumatoid arthritis (RA) disease activity in RA

BACKGROUND: Periodontitis (PD) has been reported to be associated with rheumatoid arthritis (RA). Porphyromonas gingivalis (P. gingivalis) is a gram-negative anaerobic bacterium that is recognized as one of the major pathogenic organisms in PD and is the only bacterium known to express peptidylarginine deiminase (PAD). Antibody against human α-enolase (ENO1) is one of the autoantibodies in RA. ENO1 is a highly conserved protein, and could be a candidate molecule for molecular mimicry between bacterial and human proteins. In the present study, we measured serum antibody against P. gingivalis and human ENO1 in patients with RA and investigated their association with the severity of PD or disease activity of RA. METHODS: Two hundred, forty-eight patients with RA and 85 age- and sex-matched healthy controls were evaluated by rheumatologic and periodontal examinations. The serum levels of anti-P. gingivalis and anti-ENO1 antibodies were measured by an enzyme-linked immunosorbent assay (ELISA). RESULTS: Patients with RA had significantly higher levels of anti-P. gingivalis and anti-ENO1 antibody titers than the controls (p = 0.002 and 0.0001, respectively). Anti-P. gingivalis antibody titers significantly correlated with anti-ENO1 antibody titers in RA patients (r = 0.30, p < 0.0001). There were significant correlations between anti-P. gingivalis antibody titers and the gingival index (GI), probing pocket depth (PPD), bleeding on probing (BOP) and clinical attachment level (CAL) (p = 0.038, 0.004, 0.004 and 0.002, respectively) in RA. Anti-P. gingivalis antibody titers were not correlated with disease activity score 28 (DAS28) or anti-CCP titer. However, anti-ENO1 antibody titers were significantly correlated not only with the periodontal indices, such as PPD, BOP, and CAL (p = 0.013, 0.023 and 0.017, respectively), but also RA clinical characteristics, such as DAS28, anti-CCP titer, and ESR (p = 0.009, 0.015 and 0.001, respectively). CONCLUSION: Anti-P. gingivalis and anti-ENO1 antibody titers were correlated with the severity of PD in RA. Anti-ENO1 antibody titers, but not anti-P. gingivalis antibody titers, were further associated with RA disease activity. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12891-015-0647-6) contains supplementary material, which is available to authorized users.