Highly Conserved Surface Proteins of Oral Spirochetes as Adhesins and Potent Inducers of Proinflammatory and Osteoclastogenic Factors

Abstract

Oral spirochetes include enormously heterogeneous Treponema species, and some have been implicated in the etiology of periodontitis. In this study, we characterized highly conserved surface proteins in four representative oral spirochetes (Treponema denticola, T. lecithinolyticum, T. maltophilum, and T. socranskii subsp. socranskii) that are homologs of T. pallidum Tp92, with opsonophagocytic potential and protective capacity against syphilis. Tp92 homologs of oral spirochetes had predicted signal peptides (20 to 31 amino acids) and molecular masses of 88 to 92 kDa for mature proteins. They showed amino acid sequence identities of 37.9 to 49.3% and similarities of 54.5 to 66.9% to Tp92. The sequence identities and similarities of Tp92 homologs of oral treponemes to one another were 41.6 to 71.6% and 59.9 to 85.6%, respectively. The tp92 gene homologs were successfully expressed in Escherichia coli, and the recombinant proteins were capable of binding to KB cells, an epithelial cell line, and inhibited the binding of the whole bacteria to the cells. Antiserum (the immunoglobulin G fraction) raised against a recombinant form of the T. denticola Tp92 homolog cross-reacted with homologs from three other species of treponemes. The Tp92 homologs stimulated various factors involved in inflammation and osteoclastogenesis, like interleukin-1␤ (IL-1␤), tumor necrosis factor alpha, IL-6, prostaglandin E 2 , and matrix metalloproteinase 9, in host cells like monocytes and fibroblasts. Our results demonstrate that Tp92 homologs of oral spirochetes are highly conserved and may play an important role in cell attachment, inflammation, and tissue destruction. The coexistence of various Treponema species in a single periodontal pocket and, therefore, the accumulation of multiple Tp92 homologs may amplify the pathological effect in periodontitis.Numerous studies examining epidemiology and virulence factors have revealed strong evidence for the implication of oral spirochetes in the etiology of periodontitis, and the presence of spirochetes in the subgingival plaque is associated with an increased severity of periodontitis (16,38,48). Oral spirochetes include at least 50 phylotypes (12) and account for 20 to

Treponema denticolaSuppresses Expression of Human β-Defensin-3 in Gingival Epithelial Cells through Inhibition of the Toll-Like Receptor 2 Axis

“…A breach in the epithelial barrier would facilitate the invasion of plaque bacteria, including T. denticola, thus contributing to the pathogenesis of periodontitis. Studies using sonicates or purified components of T. denticola, such as lipooligosaccharide, peptidoglycan, or a surface protein, have reported the induction of an inflammatory response in murine macrophages, human macrophage-like cells, and fibroblasts (4,5,15,26,27). However, our results suggest that live bacteria may suppress or paralyze the inflammatory responses of these cells.…”

Surface Immunolabeling and Consensus Computational Framework To Identify Candidate Rare Outer Membrane Proteins ofTreponema pallidum

“…␤-Barrels have also been identified in the OMs of mitochondria and chloroplasts, eukaryotic organelles originating, respectively, from alphaproteobacterial and cyanobacterial endosymbiotic precursors (62,130). Perhaps most important has been the discovery of the conserved assembly machinery that chaperones newly exported OMP precursors into the OMs of virtually all diderms, including Borrelia burgdorferi (77) and oral treponemes (65), as well as mitochondria and chloroplasts (67,111). Indeed, the presence in T. pallidum of a protein, TP0326, that appears to possess the characteristic BamA bipartite structure (i.e., N-terminal POTRA domains and a C-terminal ␤-barrel [ Fig.…”

Virulence Factors of the Oral Spirochete Treponema denticola

“…Homologs of Tp92 have been identified in T. maltophilum, T. lecithinolyticum, T. socranskii, and T. denticola. Antisera raised to recombinant T. denticola Td92 have been used to show surface exposure of Td92 and inhibition of T. denticola binding to KB epithelial cells (Jun et al, 2008). All oral treponeme Tp92 homologs induced production of various cytokines, cyclooxygenase-2 (COX-2), and prostaglandin E 2 from THP-1 cells and periodontal ligament cells, indicating a pro-inflammatory response.…”