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Prevotella intermedia fimbriae mediate hemagglutination
K P Leung1, H Fukushima, W E Nesbitt
1Periodontal Disease Research Center and Department of Oral Biology, College of Dentistry, University of Florida, Gainesville 32610, USA.
Abstract:
Our earlier studies demonstrated that clinical strains of Prevotella intermedia, isolated from human periodontal pockets, possess various types of fimbria (surface appendages) as determined ultrastructurally. These bacteria have the ability to agglutinate selected mammalian erythrocytes. Hemagglutinating activity exhibited by these cells may be attributable to these surface structures. Strain 17, which possess fimbriae of 8 nm in diameter and readily agglutinates human, monkey, sheep, rabbit, and mouse erythrocytes was selected to determine whether these fimbriae possessed the hemagglutinating activity. Fimbriae were mechanically sheared, concentrated by ammonium sulfate precipitation, solubilized in 10 mM Tris-HCl buffer containing 0.5% deoxycholate and partly purified by ultracentrifugation in a 10-50% linear sucrose gradient. Isolated fimbriae banded at a density of 1.20-1.15 g/ml, appeared fairly uniform ultrastructurally, and possessed hemagglutinating activity. The hemagglutinating activity of P. intermedia whole cells and isolated 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. intermedia whole cells and isolated fimbriae bound to rabbit erythrocytes as observed by: (a) decrease in the hemagglutinating activity of bacterial whole cells and isolated fimbriae after incubation with rabbit erythrocytes, (b) increase in hemagglutinating activity of the red cells used for absorption, and (c) the presence of P. intermedia whole cells and fimbriae on red cells after absorption as revealed by immunoelectron microscopy. Both the immune immunoglobulin G of the rabbit polyclonal anti-fimbriae antibody and the immune immunoglobulin G and its Fab fragments of the murine monoclonal anti-fimbriae antibody were effective inhibitors of hemagglutination mediated by isolated fimbriae. Immunogold labeling showed that the monoclonal antibody bound specifically 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.
Insights
Prevotella intermedia fimbriae, hair-like surface structures, cause hemagglutination by binding to red blood cells. These fimbriae are responsible for the bacteria's ability to clump various mammalian erythrocytes.
Area of Science:
- Microbiology
- Bacteriology
- Immunology
Background:
- Clinical Prevotella intermedia strains possess fimbriae (surface appendages).
- These bacteria exhibit hemagglutinating activity, potentially due to surface structures.
Purpose of the Study:
- To investigate if the fimbriae of Prevotella intermedia are responsible for its hemagglutinating activity.
Main Methods:
- Mechanical shearing and purification of fimbriae from Prevotella intermedia.
- Assessing hemagglutinating activity of whole cells and isolated fimbriae.
- Enzyme, heat, and pH treatments to characterize activity.
- Antibody inhibition assays and immunoelectron microscopy.
Main Results:
- Isolated Prevotella intermedia fimbriae exhibited hemagglutinating activity.
- Activity was sensitive to proteases and heat, with optimal pH at 7.0.
- Fimbriae were shown to bind to rabbit erythrocytes, and antibodies inhibited this interaction.
Conclusions:
- The hemagglutination exhibited by Prevotella intermedia is attributable to its fimbriae.
- Fimbriae play a role in the interaction between Prevotella intermedia and erythrocytes.