Role of the amino-terminal region of Porphyromonas gingivalis fimbriae in adherence to epithelial cells.

Porphyromonas gingivalis fimbriae elicit many responses in eukaryotic cells, including mitogenicity, cytokine production, epithelial cell invasion, and cellular immune response. Specific domains of the major fimbrial protein (FimA) have been shown to be important in triggering some of these functions. The goal of the present study was to identify the domain(s) of P. gingivalis FimA responsible for specific interaction with human mucosal epithelial cells. Fimbriated P. gingivalis strains have been shown to bind to buccal epithelial cells, whereas nonfimbriated strains bind at low levels or not at all. This and other studies provide evidence that FimA mediates the adherence of P. gingivalis to oral epithelial cells. To determine the specific region(s) of P. gingivalis FimA involved in epithelial cell binding, specific antipeptide antibodies were used to inhibit the binding of iodinated purified fimbriae as well as the binding of P. gingivalis cells to epithelial cells. Antibodies directed against peptides 49 to 68 (VVMANTAGAMELVGKTLAEVK) and 69 to 90 (ALTTELTAENQEAAGLIMTAEP) were found to highly inhibit both the binding of fimbriae and the binding of P. gingivalis cells to epithelial cells. The antibody against FimA peptides 69 to 90 also reacted with P. gingivalis fimbriae in immunogold labeling and immunoblot analysis, thereby indicating that this peptide domain is exposed on the surface of fimbriae. Our results suggest that the amino-terminal domain corresponding to amino acid residues 49 to 90 of the fimbrillin protein is a major epithelial cell binding domain of P. gingivalis fimbriae.