IgG antibody response of localized juvenile periodontitis patients to the 29 kilodalton outer membrane protein of Actinobacillus actinomycetemcomitans.

Levels of serum IgG antibody to the 29 kilodalton outer membrane protein of A. actinomycetemcomitans Y4 in sera of periodontally healthy subjects and localized juvenile periodontitis patients were determined using an enzyme-linked immunosorbent assay (ELISA). The 29 kDa protein was isolated by solubilization of an octylglucoside-NaCl insoluble fraction by incubation at ambient temperature in 20 mM sodium phosphate, pH 7.5, containing 1% sodium dodecyl sulfate. The isolated protein migrated on SDS-polyacrylamide gels with an apparent molecular mass of 29 kDa following incubation in sample buffer at ambient temperature. However, the protein migrated with an apparent molecular mass of 34 kDa following incubation in sample buffer at 100 degrees C for 10 minutes. Geometric mean IgG antibody titers to the 29 kDa protein were significantly higher in sera from LJP subjects than in sera obtained from periodontally healthy subjects. Twenty-two of 35 LJP sera (63%) had antibody titers greater than 2 standard deviations from the mean titer of the periodontally healthy group. Among LJP subjects, elevated antibody titers to the 29 kDa protein were found primarily in subjects greater than or equal to 18 years of age, with the highest titers seen in patients 18 to 21 years of age. The results of this study indicate that the humoral response of LJP subjects to A. actinomycetemcomitans includes the production of IgG antibodies which recognize the major outer membrane proteins of this organism.