PREVOTELLA-INTERMEDIA FIMBRIAE MEDIATE HEMAGGLUTINATION

Our earlier studies demonstrated that clinical strains of Prevotella i ntermedia, isolated from human periodontal pockets, possess various ty pes of fimbria (surface appendages) as determined ultrastructurally. ? These bacteria have the ability to agglutinate selected mammalian eryt hrocytes. Hemagglutinating activity exhibited by these cells may be at tributable to these surface structures. Strain 17, which posseses fimb riae of 8 nm in diameter and readily agglutinates human, monkey, sheep , rabbit, and mouse erythrocytes was selected to determine whether the se fimbriae possessed the hemagglutinating activity. Fimbriae were mec hanically sheared, concentrated by ammonium sulfate precipitation, sol ubilized in 10 mM Tris-HCl buffer containing 0.5% deoxycholate and par tly purified by ultracentrifugation in a 10-50% linear sucrose gradien t. Isolated fimbriae banded at a density of 1.10-1.15 g/ml, appeared f airly uniform ultrastructurally, and possessed hemagglutinating activi ty. The hemagglutinating activity of P. intermedia whole cells and iso lated fimbriae was reduced by treatment with proteases and eliminated by treatment with heat at 80 degrees C for 10 min. The optimal pH for the hemagglutination was 7.0. In the process of hemagglutination, P. i ntermedia whole cells and isolated fimbriae bound to rabbit erythrocyt es as observed by: (a) decrease in the hemagglutinating activity of ba cterial whole cells and isolated fimbriae after incubation with rabbit erythrocytes, (b) increase in hemagglutinating activity of the red ce lls used for absorption and (c) the presence of P. intermedia whole ce lls and fimbriae on red cells after absorption as revealed by immunoel ectron microscopy. Both the immune immunoglobulin G of the rabbit poly clonal antifimbriae antibody and the immune immunoglobulin G and its F ab fragments of the murine monoclonal anti-fimbriae antibody were effe ctive inhibitors of hemagglutination mediated by isolated fimbriae. Im munogold labeling showed that the monoclonal antibody bound specifical ly to P, intermedia fimbriae. These results collectively suggest that the hemagglutination exhibited by P. intermedia may be attributable to the fimbriae or the fimbrial-associated components.