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

Background: Six serotypes of Porphyromonas gingivalis have recently been de scribed. We sought to test the hypothesis that serotype specific carbohydra tes from these strains are important antigens that elicit potent: immune re sponses. Methods: Serum concentrations of IgG reactive with P gingivalis serotypes K 1-K6 were determined for 28 adult (AP) and 28 generalized early-onset (G-EO P) periodontitis patients previously determined to be seropositive for a br oken cell preparation of P. gingivalis. To confirm relationships suggested for KI, K2, and K6 in the analysis of initial data, the study population wa s 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 mu g/ml with many subjects seropositive to more than one serotype. Concentrations for the sub set of patients who was seropositive were high (mean responses ranged from 20 to 105 mu g/ml for the 6 serotypes). Significant correlations between se ropositivity to serotypes K1 and K5 as well as between K5 and K6 were found . Conclusions: We examined the relationship of diagnosis, race, gender, smoki ng, probing depth, attachment loss, and antibody reaction with the P gingiv alis serotypes by analysis of variance. Initial findings suggested potentia l relationships between diagnosis, smoking, race, gender, and antibody reac tive with serotypes K1, K2, and K6. A significant relationship did exist be tween smoking and decreased antibody reactive with Pi gingivalis serotype K 2. No other relationships were substantiated. We also examined the Ige subc lass distribution and found that responses were almost exclusively IgG2. Th ese 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.