Characterization of serum antibody to Actinobacillus actinomycetemcomitans GroEL-like protein in periodontitis patients and healthy subjects.

Recent evidence suggests that molecular mimicry between bacterial and human heat shock protein 60 (hsp60) is involved in various conditions of autoimmune and infectious diseases. Many periodontopathic bacteria have been reported to express GroEL-like protein that is homologous to human hsp60. In this study, the presence of antibodies to the hsp60 of Actinobacillus actinomycetemcomitans in the sera of periodontitis patients and periodontally healthy control subjects was evaluated by enzyme-linked immunosorbent assay using a recombinant A. actinomycetemcomitans GroEL as an antigen. Furthermore, their cross-reactivity with Escherichia coli GroEL and Mycobacterium bovis BCG hsp65 was examined. The mean values of antibody were 0.624 (range 0.088-1.113) and 0.728 (range 0.217-1.296) in control subjects and periodontitis patients, respectively. The antibody levels to A. actinomycetemcomitans after absorption with E. coli GroEL and M. bovis BCG clearly decreased in both control subjects and periodontitis patients. The remaining antibody levels to A. actinomycetemcomitans GroEL after absorption with M. bovis BCG hsp65 were higher than those with E. coli GroEL, indicating higher cross-reactivity with E. coli GroEL. These results suggest that not only periodontitis patients but also periodontally healthy subjects may be infected with A. actinomycetemcomitans but that the part of the antibody could be derived from the cross-reactivity with E. coli GroEL. Any relationship of the antibody to the disease, however, remains to be determined.