Table 2. Function of virulence genes of the red complex.
| Species | Virulence gene | Virulece function |
|---|---|---|
| T. forsythia | Exo alpha sialidase, trypsin-like proteases | Degradation of host proteins |
| PrtH protease, forsythia cell-detaching factor protein | Inducing detachment of adherent cells and interleukin-8 production in human fibroblasts | |
| Surface layer protein A | Promoting epithelial cell adherence, invasion and biofilm formation | |
| BNR Asp-box repeat protein | Bacterial adherence and invasion of epithelial cells | |
| Surface antigen BspA | Binding to fibrinogen and fibronectin and the induction of proinflammatory cytokine expression in host cells by activating Toll-like receptor 2 | |
| Methylglyoxalsynthase | Enolization of DHAP to produce methylglyoxal | |
| Novel virulence gene candidates of T. forsythia | L-asparaginase I | Inhibiting T-cell responses of host |
| Hypothetical protein | Protein of unknown function* | |
| ATP-binding protein | ABC transporters involved in nutrient or metal ion uptake may result indirectly from attachment of the bacteria to host cells | |
| Protein translocase subunit secA 1 | Secretion of factors associated with pathogenesis or stress response | |
| T. denticola | Leucine-rich repeat protein | Binding to T. forsythia |
| Dentilisin | Disrupting or modulating intercellular host signaling pathways and degradation of intercellular adhesion proteins | |
| Major outer sheath protein Msp | Mediating colonization of host tissue | |
| Lipoprotein OppA, FhbB | Epithelial cell binding and invasion, subversion of the complement cascade or tissue invasion | |
| Chemotaxis CheR, CheB | Damaging host tissue | |
| P. gingivalis | Novel dipeptidylpeptidase dpp | Abscess formation and lethality |
| Hemagglutinin HagA | Periodontal tissue/cell invasion | |
| Hemagglutinin HagB | Stimulate strong IgG and Th immune responses; induce immune protection | |
| Gingipains RgpA, RgpB, Kgp | Tissue destruction and alter cytokine/chemokine and Igs bioactivity (i.e., IL-12,TNFa, C3 and C5, IgG/A) | |
| Fimbriae FimA | Bacterial colonization, induce host IgA, IgG and Th1 immune responses | |
| Capsular polysaccharide | Stimulating immune protection in mouse oral challenge model (via IgG activity) |
Abbreviations: ABC, ATP-binding cassette; DHAP, dihydroxyacetone phosphate; IgG, immunoglobulin G; IL, interleukin; Th, T helper; TNF, tumor necrosis factor.
*Structurally this family is part of the six hairpin glycosidase superfamily, suggesting a glycosyl hydrolase, which is one of the virulence gene (Niu et al., 2013).