Antibodies to Periodontal Bacteria Are Associated with Systemic Lupus Erythematosus and Autoantibody Positivity

Periodontitis has been suggested to play a role in the etiology of systemic lupus erythematosus (SLE). However, evidence remains limited, and the underlying mechanisms are unclear. Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans are strongly linked to periodontitis. Here, we evaluate the levels of circulating antibodies against these bacteria in patients with SLE and healthy controls and analyze their association with SLE-related autoantibodies. Serum IgG antibodies against P. gingivalis, A. actinomycetemcomitans leukotoxin A (LtxA), and two control bacteria (Capnocytophaga ochracea and Escherichia coli) were quantified in 223 patients with SLE and 301 healthy controls. Data was analyzed with ANCOVA and logistic regressions adjusting for age, sex, and smoking status. Exposure to P. gingivalis and A. actinomycetemcomitans, as estimated from antibody levels, was associated with SLE (Odds Ratios (ORs) = 3.0, p = 0.0002 and OR = 2.61, p = 0.0007, respectively). An additive interaction on SLE susceptibility was observed for exposure to P. gingivalis and smoking, with an attributable proportion due to interaction (AP) = 0.72 (95% CI = 0.41-1.02). Anti-A. actinomycetemcomitans LtxA antibodies were elevated in patients positive for anti-dsDNA antibodies (p = 0.02) and nominally increased in those positive for anti-cardiolipin antibodies (p = 0.06). Elevated levels of antibodies against P. gingivalis and A. actinomycetemcomitans in patients with SLE suggest a role for these bacteria, or periodontitis, in the immunopathogenesis of SLE. An additive interaction with smoking was observed for P. gingivalis, and A. actinomycetemcomitans exposure was associated with anti-DSNA antibody positivity, supporting a link between these bacteria and SLE.