The surface (S-) layer is a virulence factor of Bacteroides forsythus

Abstract

Bacteroides forsythus has emerged as a crucial periodontal pathogen with possible implications for systemic disease. The aim of this study was to isolate the S-layer from B. forsythus and examine its virulence potential as a part of efforts to characterize virulence factors of B. forsythus. The role of the S-layer in the haemagglutinating and adherent/invasive activities was evaluated. It was observed that the S-layer alone was able to mediate haemagglutination. In adherent and invasive studies, transmission electron microscopy clearly revealed that B. forsythus cells were able to attach to and invade KB cells, showing the formation of a microvillus-like extension around adherent and intracellular bacteria. The quantitative analysis showed that five different B. forsythus strains exhibited attachment (1?9-2?3 %) and invasion (0?4-0?7 %) capabilities. It was also observed through antibody inhibition assays that adherent/invasive activities of B. forsythus are mediated by the S-layer. Furthermore, an in vivo immunization study adopting a murine abscess model was used to prove that the S-layer is involved in the infectious process of abscess formation. While mice immunized with purified S-layer and B. forsythus whole cells did not develop any abscesses when challenged with viable B. forsythus cells, unimmunized mice developed abscesses. Collectively, the data obtained from these studies indicate that the S-layer of B. forsythus is a virulence factor.

Investigation of Subgingival Profile of Periodontopathic Bacteria Using Polymerase Chain Reaction

“…Some previous studies suggested that T. forsythia and C. rectus possessed an S-layer on the cell surface, which has been associated with virulence in periodontitis 5,16) . Monitoring of these bacteria may prove to be an important tool in periodontal therapy.…”

Tannerella forsythia invasion in oral epithelial cells requires phosphoinositide 3-kinase activation and clathrin-mediated endocytosis

“…A plausible explanation is that other bacterial components involved in invasion might also contribute to PI3K activation. Although the identity of these components is currently unknown, an earlier study has demonstrated that T. forsythia S-layer proteins also mediate attachment to and invasion of KB epithelial cells (Sabet et al, 2003). Interestingly, T. forsythia whole cells and their components have been shown to activate the pattern recognition receptor Toll-like receptor (TLR)2 (Hasebe et al, 2004;Kikkert et al, 2007;Onishi et al, 2008), and PI3K is also a downstream target of TLR2 activation.…”

“…T. forsythia has been detected intracellularly in buccal and crevicular epithelium of patients with periodontitis (Colombo et al, 2007;Rudney et al, 2005). Furthermore, T. forsythia has been shown to invade epithelial cells in vitro (Han et al, 2000;Inagaki et al, 2006;Kirschbaum et al, 2010;Sabet et al, 2003). Thus, it is likely that this bacterium exploits epithelial cell invasion to avoid host defence surveillance.…”

Immunocytochemical approach for surface layer proteins of freeze-substituted Tannerella forsythensis by energy-filtering transmission electron microscopy

“…(Higuchi et al, 2000;Moriguchi et al, 2003). Sabet et al (2003) reported that the S-layer consists of 200 and 210-kDa proteins. In their study, the bacterial cells were resuspended in 0.1 M cacodylate buffer with 1% glutaraldehyde, and post fixed with 1% OsO 4 .…”