Related Experiment Videos
Characterization of the human immunoglobulin G Fc-binding activity in Prevotella intermedia
1Groupe de Recherche en Ecologie Buccale, Faculté de Médecine Dentaire, Université Laval, Québec, Canada.
Abstract:
Many pathogenic bacteria possess cell surface receptors which can bind immunoglobulins via the Fc portion. The aim of this study was to characterize the human immunoglobulin G (IgG) Fc-binding activity of Prevotella intermedia, a suspected etiologic agent of adult chronic periodontitis. The Fc-binding activity of P. intermedia on whole cells and on extracellular vesicles was demonstrated. Incubation of P. intermedia cells in the presence of Zwittergent 3-14 allowed complete solubilization of the Fc receptor from the cell surface. This cell envelope extract was thus used to characterize the Fc-binding activity. A microtiter plate assay using alkaline phosphatase-labeled Fc fragments showed that preincubation of the cell envelope extract with human IgG, human IgG Fc fragments, or human serum completely inhibited the Fc-binding activity. Partial inhibition was obtained with human IgG F(ab')2 fragments, whereas no inhibition occurred following preincubation with human IgA, carbohydrates, and selected proteins. Preincubation of the cell envelope extract with IgG from a variety of animals demonstrated that rabbit, mouse, rat, goat, and sheep IgG did not inhibit Fc-binding activity, whereas cow, pig, and dog IgG partially inhibited Fc-binding activity. A strong inhibition comparable to that obtained with human IgG was noted with monkey IgG. The Fc receptor of P. intermedia is thus different from the six types previously reported in other nonoral bacteria. Polyacrylamide gel electrophoresis and Western blotting (immunoblotting) analysis of the cell envelope extract revealed a major band with a molecular mass of approximately 65 kDa which reacted with peroxidase-labeled human IgG Fe fragments. Transmission electron microscopy showed a uniform distribution of the Fc receptor on the bacterial surface, as revealed by gold labeling. The Fc-binding activity demonstrated in this study may act as an additional virulence factor for P. intermedia by reducing IgG reactions with the bacterial cell.
Insights
Prevotella intermedia possesses a unique Fc receptor that binds human immunoglobulin G (IgG), potentially aiding its virulence in periodontitis. This bacterial Fc-binding activity differs from previously identified types in other bacteria.
Area of Science:
- Microbiology
- Immunology
- Periodontal disease research
Background:
- Pathogenic bacteria often have cell surface receptors that bind the Fc portion of immunoglobulins.
- Prevotella intermedia is implicated in adult chronic periodontitis.
- Understanding bacterial virulence factors is crucial for developing therapeutic strategies.
Purpose of the Study:
- To characterize the human immunoglobulin G (IgG) Fc-binding activity of Prevotella intermedia.
- To investigate the potential role of this Fc-binding activity as a virulence factor.
Main Methods:
- Fc-binding activity was assessed on whole cells and extracellular vesicles of P. intermedia.
- A cell envelope extract was prepared and used in microtiter plate assays with labeled Fc fragments.
- Inhibition assays were performed using various human and animal immunoglobulins and fragments.
- Molecular mass and localization of the Fc receptor were determined using SDS-PAGE, Western blotting, and transmission electron microscopy.
Main Results:
- P. intermedia demonstrated significant Fc-binding activity, which could be solubilized from the cell surface.
- Human IgG, IgG Fc fragments, and human serum completely inhibited binding, while F(ab')2 fragments caused partial inhibition.
- IgG from cows, pigs, dogs, and monkeys showed partial to strong inhibition, unlike IgG from rabbits, mice, rats, goats, and sheep.
- A 65 kDa protein band in the cell envelope extract reacted with human IgG Fc fragments, and the receptor was uniformly distributed on the bacterial surface.
Conclusions:
- Prevotella intermedia possesses a distinct Fc receptor that binds human IgG.
- This Fc receptor differs from previously characterized types in other bacteria.
- The Fc-binding activity likely serves as a virulence factor by hindering IgG-mediated bacterial clearance.