Antibody reactive with Porphyromonas gingivalis serotypes K1-6 in adult and generalized early-onset periodontitis

Background: Six serotypes of Porphyromonas gingivalis have recently been described. We sought to test the hypothesis that serotype specific carbohydrates from these strains are important antigens that elicit potent immune responses. Methods: Serum concentrations of IgG reactive with P. gingivalis serotypes K1-K6 were determined for 28 adult (AP) and 28 generalized early-onset (G-EOP) periodontitis patients previously determined to be seropositive for a broken cell preparation of P. gingivalis. To confirm relationships suggested for K1, K2, and K6 in the analysis of initial data, the study population was increased to 133. Results: Frequency of seropositivity for the 6 serotypes ranged from 26 to 54% of subjects. IgG concentrations ranged from 0 to 453 μg/ml with many subjects seropositive to more than one serotype. Concentrations for the subset of patients who was seropositive were high (mean responses ranged from 20 to 105 μg/ml for the 6 serotypes). Significant correlations between seropositivity to serotypes K1 and K5 as well as between K5 and K6 were found. Conclusions: We examined the relationship of diagnosis, race, gender, smoking, probing depth, attachment loss, and antibody reaction with the P. gingivalis serotypes by analysis of variance. Initial findings suggested potential relationships between diagnosis, smoking, race, gender, and antibody reactive with serotypes K1, K2, and K6. A significant relationship did exist between smoking and decreased antibody reactive with P. gingivalis serotype K2. No other relationships were substantiated. We also examined the IgG subclass distribution and found that responses were almost exclusively IgG2. These data support the concept that antibody responses to all 6 serotypes are common in both AP and G-EOP and that these K serotype carbohydrates elicit potent IgG2 responses.