Porphvronzonas gingivalis is a predominant periodontal pathogen, whose fimbriae are considered to be a major virulence factor. especially for bacterial adherence and invasion of host cells. In the present study, we investigated the influence of fimbriae on the interactions between alpha v beta 3 and alpha 5 beta 1-integrins and their ligand extracellular matrix (ECM) proteins (vitronectin and fibronectin), using human alpha v beta 3- and alpha 5 beta 1-1-integrin-overexpressing CHO cell lines (CHO alpha v beta 3 and CHO alpha 5 beta 1, respectively). P. gingivalis was found to have significantly greater binding to CHO alpha v beta 3 and CHO alpha 5 beta 1 than to control cells, whereas a fimbria-deficient mutant showed negligible binding to any of the tested cell lines. CHO alpha v beta 3 and CHO alpha 5 beta 1 cells attached to the polystyrene culture dishes in the presence of their ligand ECM proteins, while fimbriae markedly inhibited those attachments in a dose-dependent manner, with the highest dose of fimbriae achieving complete inhibition. In addition, the binding of vitronectin and fibronectin to CHO alpha v beta 3 and CHO alpha 5 beta 1 was inhibited by P. gingivalis cells. These results Suggest that P. gingivalis fimbriae compete with ECM proteins for alpha v beta 3- and alpha 5 beta 1-integrins, and inhibit integrin/ECM protein-related cellular functions. (c) 2005 Elsevier SAS. All rights reserved.