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Role of cryptic receptors (cryptitopes) in bacterial adhesion to oral surfaces
R J Gibbons1, D I Hay, W C Childs
1Forsyth Dental Center, Boston, MA 02115.
Abstract:
Progress in characterizing the receptors that promote bacterial attachment to teeth and oral epithelial cells has suggested that hidden molecular segments may frequently be involved. Such cryptic receptors, referred to as 'cryptitopes', may become exposed by several mechanisms. Hidden segments of salivary acidic proline-rich proteins evidently become exposed when the molecules undergo a conformational change as they adsorb to apatitic mineral. Adhesins of Actinomyces viscosus and certain other prominent dental plaque bacteria are able to bind to these cryptitopes, and this enables these organisms to bind to proline-rich proteins on apatitic surfaces while avoiding interactions with these proteins in solution. Cryptitopes may also become exposed as a result of enzymatic action. Thus, several bacteria, including Fusobacterium nucleatum, Eikenella corrodens, A. viscosus, A. naeslundii and Bacteroides intermedius, have adhesins that bind to galactosyl receptors which become exposed after treatment with neuraminidase. Similarly, the adhesion of some Gram-negative bacteria, such as Bact. gingivalis, is enhanced when tissue surfaces are treated with certain proteases, or lysosomal enzymes derived from human polymorphonuclear leucocytes. It seems likely that elevated levels of enzymes present in gingival fluid as sequelae of poor oral hygiene and gingivitis may generate cryptitopes for potentially periodontopathic bacteria, and thereby contribute to modulation of the gingival flora.
Insights
Hidden molecular segments, or cryptitopes, on oral surfaces facilitate bacterial attachment. These cryptitopes are exposed by protein conformational changes or enzymatic action, influencing dental plaque formation and potentially periodontopathic bacteria.
Area of Science:
- Oral microbiology
- Molecular biology
- Biochemistry
Background:
- Bacterial attachment to oral surfaces is crucial for dental plaque formation.
- Receptor-ligand interactions mediate bacterial adhesion.
- Previously unrecognized molecular structures may play a role in this process.
Purpose of the Study:
- To investigate the role of hidden molecular segments (cryptitopes) in bacterial attachment to oral surfaces.
- To identify mechanisms of cryptitope exposure.
- To understand how cryptitopes influence the composition of the gingival flora.
Main Methods:
- Characterization of salivary proteins and bacterial adhesins.
- Analysis of protein conformational changes upon adsorption to mineral surfaces.
- Enzymatic treatment of oral surfaces to expose receptors.
- Bacterial adhesion assays.
Main Results:
- Salivary acidic proline-rich proteins expose cryptic receptors upon adsorption to apatitic surfaces.
- Certain dental plaque bacteria bind to these exposed cryptitopes.
- Enzymatic cleavage (neuraminidase, proteases) exposes receptors for bacterial adhesion.
- Elevated gingival fluid enzymes may generate cryptitopes, influencing gingival flora.
Conclusions:
- Cryptitopes are important in mediating bacterial attachment to oral surfaces.
- Conformational changes and enzymatic activity are key mechanisms for cryptitope exposure.
- The generation of cryptitopes in gingival fluid may contribute to periodontopathic bacterial colonization and disease progression.