Changes of Cytokines in Saliva of Pigs with Streptococcus suis Infection Measured with a Multiplex Assay

Experimental Objective: This study evaluated potential changes in cytokines in the saliva of pigs with meningitis and Streptococcus suis (S. suis) infection, using a multiplex assay. Methods: For this purpose, levels of 13 cytokines, namely GM-CSF, IFNγ, IL-1α, IL-1β, IL-1ra, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-18, and TNF-α, were measured in porcine saliva from 29 male weaning piglets (6 to 9 weeks old) with meningitis and S. suis infection (S. suis group, n = 15) and healthy controls (healthy group, n = 14). Samples were measured using Luminex xMAP^® technology with a multiplex assay that was analytically evaluated in this study. Results: The measurement of these cytokines provided adequate values during the analytical validation conducted in this study, except for GM-CSF, TNF-α, IFNγ, and IL-8. Particularly for GM-CSF and TNF-α, many values, especially in healthy pigs, fell below the limit of quantification of the assay. In pigs with S. suis infection, 11 out of the 13 cytokines, namely GM-CSF, IFNγ, IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-10, IL-12, IL-18, and TNF-α, showed statistically (p < 0.05) higher levels compared to the healthy controls. Conclusions: These findings underscore an association between S. suis infection and alterations in selected cytokine levels in the saliva of pigs afflicted with this disease, thus highlighting the potential role of these cytokines in the immune response to infection.