Serum and gingival fluid antibodies as adjuncts in the diagnosis of Actinobacillus actinomycetemcomitans-associated periodontal disease.

Serum antibody titers to Actinobacillus actinomycetemcomitans were measured in 200 subjects by an enzyme-lined immunosorbent assay (ELISA) using whole microorganisms as antigen. Comparisons were made between titers found in periodontally normal subjects and titers in subjects with localized juvenile periodontitis (LJP), postlocalized juvenile periodontitis, generalized juvenile periodontitis or adult periodontitis. It was found that titers to all three serotypes of A. actinomycetemcomitans were elevated in LJP patients' sera, while serum antibody levels in other diseased groups were not significantly elevated to any of the serotypes. Patient sera were also examined for serum antibody to oral Haemophili previously shown to cross-react with A. actinomycetemcomitans. Similar antibody titers were found in both normal subjects and in patients with various forms of periodontal disease to Haemophilus aphrophilus, H. influenzae and H. parainfluenzae. The A. actinomycetemcomitans antibodies which were elevated in LJP patients could not be correlated with antibody titers to cross-reacting Haemophili, suggesting that these antibodies are A. actinomycetemcomitans-specific. Serum antibody responses in six of the LJP patients were assessed to autologous strains of A. actinomycetemcomitans. Each patient was found to be infected with only a single serotype of A. actinomycetemcomitans, and specific antibodies to the infecting serotype were found in the patients' sera. In families, the LJP patients had significantly elevated IgG, IgA and IgM serum antibody titers to A. actinomycetemcomitans, while the IgG and IgA antibody titers in periodontally normal siblings were at levels comparable to those found in normal subjects. However, IgM serum antibodies were elevated in the periodontally normal siblings of LJP patients suggesting that the formation of IgM antibodies to A. actinomycetemcomitans may precede the clinical appearance of localized juvenile periodontitis. Gingival crevicular fluid and serum antibody levels to A. actinomycetemcomitans were compared in LJP patients. Comparable titers of IgG, IgA and IgM antibodies were found in serum and gingival fluid in most subjects; however, gingival fluid samples sometimes showed higher titers than serum, likely resulting from local antibody synthesis. The value of serum antibody determinations to A. actinomycetemcomitans in the diagnosis of Actinobacillus-associated periodontitis was also assessed. The predictive value of a positive test (significantly elevated anti-A. actinomycetemcomitans IgG) was 86%, while the specificity was 89%.(ABSTRACT TRUNCATED AT 400 WORDS)