Metaproteomics of Saliva Identifies Human Protein Markers Specific for Individuals With Periodontitis and Dental Caries Compared to Orally Healthy Controls

PeerJ. 2016 Sep 14;4:e2433. doi: 10.7717/peerj.2433. eCollection 2016.


Background: The composition of the salivary microbiota has been reported to differentiate between patients with periodontitis, dental caries and orally healthy individuals. To identify characteristics of diseased and healthy saliva we thus wanted to compare saliva metaproteomes from patients with periodontitis and dental caries to healthy individuals.

Methods: Stimulated saliva samples were collected from 10 patients with periodontitis, 10 patients with dental caries and 10 orally healthy individuals. The proteins in the saliva samples were subjected to denaturing buffer and digested enzymatically with LysC and trypsin. The resulting peptide mixtures were cleaned up by solid-phase extraction and separated online with 2 h gradients by nano-scale C18 reversed-phase chromatography connected to a mass spectrometer through an electrospray source. The eluting peptides were analyzed on a tandem mass spectrometer operated in data-dependent acquisition mode.

Results: We identified a total of 35,664 unique peptides from 4,161 different proteins, of which 1,946 and 2,090 were of bacterial and human origin, respectively. The human protein profiles displayed significant overexpression of the complement system and inflammatory markers in periodontitis and dental caries compared to healthy controls. Bacterial proteome profiles and functional annotation were very similar in health and disease.

Conclusions: Overexpression of proteins related to the complement system and inflammation seems to correlate with oral disease status. Similar bacterial proteomes in healthy and diseased individuals suggests that the salivary microbiota predominantly thrives in a planktonic state expressing no disease-associated characteristics of metabolic activity.

Keywords: Bacteria; Dental caries; Immune response; Metaproteomics; Periodontitis; Proteins; Saliva.

Grant support

This work was in part funded by the University of Copenhagen (KU2016 programme). Work at Novo Nordisk Foundation Center for Protein Research (CPR) is funded in part by a donation from the Novo Nordisk Foundation (Grant number NNF14CC0001). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.