Orally Administered Pediococcus acidilactici and Saccharomyces boulardii-Based Probiotics Alter Select Equine Immune Function Parameters

To investigate the effects of a combination of Pediococcus acidilactici and Saccharomyces boulardii, the following experiments were performed. Initially, an in vitro experiment was performed in which the culture supernatant of S. boulardii and P. acidilactici was added to the culture media of isolated peripheral blood mononuclear cells (PBMCs), and the proliferative response to cellular stimulants was assayed. After this initial experiment, an in vivo experiment was performed in which 12 horses were used and assigned to one of two groups of six horses each: placebo controls or principle-treated horses. After a period of treatment, various end points were determined to test the effects of test article on (1) proliferative responses of cultured PBMCs; (2) serum immunoglobulin (Ig) concentrations; (3) lymphocyte phenotype subsets; (4) white blood cell count; and (5) response to vaccination. Results of the in vitro testing demonstrated a substantial reduction (23%) in proliferation of stimulated PBMCs. Results of in vivo testing demonstrated enhanced proliferation on day 72 in cells stimulated with phorbol (P = .04). On study day 37, the segmented neutrophil number was reduced and IgG concentration increased (mean, 329.0 vs. 185.9 ng/mL; P = .029). Results demonstrate that the test article did have some effects on systemic immunity, specifically proliferative responses, immunoglobulin G concentrations, and neutrophil numbers. Based on the findings of this study, further evaluation of these probiotics for equine wellness or disease modulation is warranted.