Comprehensive Proteomic Analysis of Dog Saliva

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Researchers from the University of Minnesota have investigated the salivary proteomics of healthy dogs using offline high pH reversed-phase liquid chromatography (LC) fractionation and nano liquid chromatography–tandem mass spectrometry (LC–MS/MS) (1).

For many decades, saliva has been considered a key analytical target when investigating the health of the oral cavity as well as the whole body. Its complex mixture of enzymes, glycoproteins, immunoglobulins, peptides, inorganic substances, white blood cells, epithelial cells, and microflora represent an analytical treasure cove with regards to interesting analytes and potential disease biomarkers.

Many methodologies exist to examine salivary proteins, however, no extensive investigation has been carried out on dogs-instead the focus had been on humans. Recently, a study focusing on a single dog was published (2); this warranted a more comprehensive characterization to provide an in-depth catalogue of the salivary proteome and endogenous peptidome of healthy dogs, the aim of which would be to search for specific changes in salivary protein composition associated with oral and systemic diseases.

Thirty-six clinically healthy dogs of various breeds and genders were selected for the study. Saliva was collected and prepared for analysis using offline high pH reversed-phase LC fractionation. Fractions were analyzed using nano-LC–MS/MS followed by bioinformatic analysis.

In total, 2491 proteins and peptides were identified with seven of the top 10 most abundant proteins having immune functions. Analysis also identified multiple proteins and peptides also present in human saliva and which are responsible for antimicrobial functions. Antimicrobial peptides (AMP), responsible for a broad spectrum of defensive action against bacteria, fungi, parasites, and viruses, were also found to be present.

Researchers noted that more in-depth studies would be required because the plethora of canine classifications was likely to cause great variation in salivary content with evidence of this appearing in the study between grouped dog breeds. Further differences were also likely to arise from factors such as age, diurnal variation, health status,and individual variation. While this study marks a good starting point, a lot more research is required to fully comprehend the proteomic and peptidomic variation in dog saliva with important next steps including a larger and more diverse dog sample as well as an evaluation of any possible influence of age, gender, breed, and individual variation. - L.B.

References

1. S.M.F. Torres et al., PLoS ONE 13(1), e0191307 (2018).
2. P. De Sousa-Pereira et al., Proteomics15(9), 1598–1607 (2015).