Antigen Specificity of Serum Antibody in A. actinomycetemcomitans-infected Periodontitis Patients

We hypothesized that serum antibody with selected antigen specificities would relate to infection and disease in the patients and, thus, describe the characteristics of potential protective antibody. This study used serum samples from 24 periodontitis patients with subgingival infection and elevated serum IgG antibody to A. actinomycetemcomitans to define the antigenic specificities of IgG, IgM, IgA, and IgGl-4 antibody to A. actinomycetemcomitans strain Y4 outer membrane antigens (OMA). Uniform IgG antibody (> 70% of the patients) was noted to antigens with Mr of 65, 38, 29, and 17 kDa. Both IgA and IgM specificities reflected those shown for IgG in each patient. IgGl and IgG2 antibody reacted with several OMA bands in each patient, while IgG3 antibodies were directed to numerous OMA bands in many patients and represented the most broad-based response. The IgG4 response patterns were limited to a few OMA bands. We noted a prominent occurrence of IgG reactions with OMA bands that were characteristic for individual patients. The frequency of responses to OMA of higher Mr (i.e., > 80 kDa) and to the 34-, 31-, and 24-kDa antigens was positively related to the total IgG antibody levels. Antibody reactive with OMA bands at 65-, 38-, 29-, 17-, 15-, and 11-kDa antigens was detected in patients with few to many teeth infected with A. actinomycetemcomitans. Furthermore, patients with a high percentage of teeth with ≥ 6 mm pockets had a decreased frequency of responses to the high-Mr antigens (i.e. > 90 kDa) as well as to the 58-kDa antigen. These findings indicate that human antibody reactivities with specific OMA bands of A. actinomycetemcomitans: (i) are positively correlated with the level of serum antibody, (ii) are associated with the number of teeth infected, and (iii) describe differences in the severity of the disease as measured by the frequency of teeth with deep pockets.