Epitope mapping of heat shock protein 60 (GroEL) from Porphyromonas gingivalis

Porphyromonas gingivalis, a putative pathogen in human periodontal disease, possesses a 60-kDa heat shock protein (hsp60. GroEL). The GroEL homologs a re known to be key molecules in auto-immune reactions because of the sequen ce similarity with human hsp60. In this study, B-cell epitopes on P. gingiv alis GroEL (PgGroEL) were analyzed by both Western immunoblotting with trun cated PgGroEL and by the multi-pin synthetic peptide approach. To examine a uto-antibody production in periodontitis patients, Western immunoblotting w ith human gingival fibroblasts was performed. Deletion mutants were constru cted from the cloned PgGroEL gene (P. gingivalis groEL), and four C-termina l truncated PgGroEL and one N-terminal truncated PgGroEL were prepared from the deletants. Sera from periodontitis patients reacted with all truncated PgGroEL used in this study. The results suggest that the B-cell epitopes w ere overlaid throughout PgGroEL. To determine the detailed locations of the B-cell epitope, 84 decapeptides covering the entire PgGroEL were synthesiz ed and the serum IgG response to the peptides was examined. Epitope mapping using the synthetic peptides confirmed that the B-cell epitopes were overl aid throughout the length of PgGroEL and revealed that highly conserved pep tides between PgGroEL and human hsp60 were recognized by the serum antibodi es. Immuno-reactivity against human gingival fibroblasts was examined with sera from 30 periodontitis patients and 10 periodontally healthy subjects. IgG antibody against the 65-kDa antigen in human gingival fibroblasts (same molecular mass as human hsp60) was detected in two patients. Although IgG production against human hsp60 may be rare case in periodontitis patients, the results of epitope mapping demonstrated the potential of PgGroEL to cau se the cross-reactions with human hsp60. (C) 2000 Federation of European Mi crobiological Societies. Published by Elsevier Science B.V. All rights rese rved.