The Subgingival Plaque Microbiome, Systemic Antibodies against Bacteria and Citrullinated Proteins following Periodontal Therapy

Periodontitis (PD) shows an association with rheumatoid arthritis (RA) and systemic inflammation. Periodontal pathogens, namely Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, are proposed to be capable of inducing citrullination of peptides in the gingiva, inducing the formation of anti-citrullinated protein antibodies (ACPAs) within susceptible hosts. Here, we sought to investigate whether periodontal treatment influenced systemic inflammation and antibody titres to P. gingivalis, A. actinomycetemcomitans, Prevotella intermedia and ACPA in 42 systemically health patients with periodontal disease. Subgingival plaque and serum samples were collected from study participants before (baseline) and 90 days after treatment to analyse the abundance of specific bacteria and evaluate anti-bacterial antibodies, C-reactive protein (CRP), tumour necrosis factor α (TNF-α), interleukin 6 (IL-6) and ACPA in serum. Following treatment, all patients showed reduced periodontal inflammation. Despite observing a weak positive correlation between CRP and IL-6 with periodontal inflammation at baseline, we observed no significant reductions in any indicators of systemic inflammation 90 days after treatment. In contrast, anti-P. gingivalis IgG significantly reduced post-treatment (p < 0.001, Wilcoxon signed rank test), although no changes were observed for other antibody titres. Patients who had detectable P. gingivalis in subgingival plaques had significantly higher anti-P. gingivalis IgG and ACPA titres, suggesting a potential association between P. gingivalis colonisation and systemic antibody titres.