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| Author(s): |
Irlan de Almeida Freires
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba |
| Defense date: | 2017-04-05 |
| Examining board members: |
Pedro Luiz Rosalen;
Maria Regina Lorenzetti Simionato;
Luciana Kfouri Siriani;
Ana Paula de Souza;
Janaina de Cassia Orlandi Sardi
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| Advisor: | Pedro Luiz Rosalen |
| Abstract | |
One of the major etiological pathogens of dental caries, Streptococcus mutans, utilizes a sophisticated repertoire of survival and virulence mechanisms, thereby potentially causing oral and extra-oral diseases. The ability of S. mutans to interact with tissue extracellular matrix components, such as collagen, enables colonization of different host tissues. Previously, we demonstrated that the 120-kDa surface collagen-binding protein Cnm promotes stringent adhesion of S. mutans to root dentin ex vivo and increases coronal caries in vivo. Nevertheless, the impact of Cnm on root caries development, where collagen is abundant, remains unknown. In Chapter I, we used a desalivated rat model under a highly cariogenic challenge to investigate whether Cnm contributes to root caries development. Rats infected with the cnm-knockout strain OMZ175?cnm showed lower levels of slight dentinal smooth-surface caries when compared to the wild type OMZ175 and complemented strain OMZ175?cnm::pcnm (P<0.05) after 5 weeks. Nevertheless, no significant differences were observed for root caries development. Surprisingly, rats infected with OMZ175 or OMZ175?cnm::pcnm showed increased root surface exposure (up to ~18.5% higher, P<0.05) than those infected with OMZ175?cnm or UA159 (naturally defective for Cnm). In summary, this chapter describes the contribution of Cnm to caries development, particularly in early stages of lesion severity, and highlights its potential impact on periodontal diseases and alveolar bone destruction. Cnm has also been reported to play an important and underestimated role in the onset of cardiovascular diseases. Yet, the mechanisms employed by Cnm+ oral pathogen to colonize and persist in human heart tissues are still poorly understood. In Chapter II, we used a heterologous expression system in Lactococcus lactis NZ9800 to investigate the role of Cnm in intracellular invasion, adhesion to cardiac tissues ex vivo and development of infective endocarditis (IE) in vivo. Similar to S. mutans, expression of Cnm in L. lactis enabled robust binding to collagen and laminin, invasion of human coronary artery endothelial cells and increased virulence in Galleria mellonella larvae (P<0.05). Using an ex vivo human heart tissue colonization model, we showed that Cnm+ strains of either S. mutans or L. lactis outcompete their Cnm- counterparts by 10-100 fold for tissue colonization (P<0.001). Finally, a rabbit IE assay showed that the L. lactis Cnm+ strain was recovered from heart tissues at significantly higher frequencies (~70%, p=0.0001) than the L. lactis Cnm- strain. In summary, this chapter describes that Cnm is enough to confer virulence to an otherwise non-pathogenic organism and confirms the usefulness of the L. lactis heterologous system for further characterization of bacterial virulence factors. Collectively, our results provide evidence that binding to extracellular matrix components mediated by Cnm is an important virulence attribute of S. mutans to cause oral and systemic diseases (AU) | |
| FAPESP's process: | 13/25080-7 - Prevalence of strains of Streptococcus mutans expressing Cnm in children and adults, and the role of this glycoprotein in the pathogen-host interactions |
| Grantee: | Irlan de Almeida Freires |
| Support Opportunities: | Scholarships in Brazil - Doctorate |