Porphyromonas gingivalis capsular K1 serotype IgG seropositivity is associated with moderate-to-severe depressive symptoms during the first trimester of pregnancy

Background: Periodontal disease (PD) is a common oral infection that is often exacerbated during pregnancy. Porphyromonas gingivalis (P. gingivalis), a keystone PD pathogen, promotes systemic inflammation, depressive-like behavior in animals, and can translocate to the brain and genital tract. Its capsular antigens (K1-K7) are key virulence factors. We hypothesized that seropositivity to specific P. gingivalis capsular K serotypes is associated with depressive symptoms and systemic inflammation during pregnancy. Methods: In a prospective cohort of pregnant women (N = 114), depressive symptoms were assessed in each trimester of pregnancy using the Edinburgh Postnatal Depression Rating Scale (EPDS, ≥13 denoting moderate-to-severe depression symptoms). Plasma IgG antibodies against P. gingivalis K1-K7 serotypes and proinflammatory cytokines were measured. Statistical analyses included Firth's bias-reduced logistic regression and mixed-effects linear models. Results: Approximately 25 % of participants were seropositive for at least one K serotype. IgG seropositivity to P. gingivalis K1 serotype was significantly associated with moderate-to-severe depressive symptoms during the first trimester (EPDS≥13; P = 0.035). Additionally, aggregated K seropositivity was significantly associated with elevated plasma IL-10 levels during the first trimester (P < 0.05, adjusted for multiple comparisons). Other cytokines were unrelated to P. gingivalis K seropositivity. Limitations: We did not assess clinical or radiological manifestations of PD, antibodies to non-capsular P. gingivalis antigens, or the presence of other PD pathogens. Conclusion: These results suggest the importance of integrating IgG K seropositivity (which, in addition to local oral pathogens, may also reflect their distal translocation) with clinical, bacteriological and radiological measures when studying associations between PD and affective dysregulation in pregnancy.