Dietary yeast beta 1,3/1,6 glucan supplemented to adult Labrador Retrievers alters peripheral blood immune cell responses to vaccination challenge without affecting protective immunity

Abstract

Yeast-derived 1,3/1,6 beta-glucans may alter host immunity to produce robust and quickly resolved responses that align with companion animal health goals. In adult dogs, immunomodulation by yeast 1,3/1,6 beta-glucans in extruded kibble diet have not been well-documented. The study objective was to evaluate systemic immune responses in dogs fed kibble diets with two yeast 1,3/1,6 beta-glucans doses before and after vaccine challenge. Twenty-four adult Labrador Retrievers were assigned to 3 dietary treatments consisting of a basal diet (control) supplemented with 0.012 or 0.023% (0.5 or 1X, respectively) yeast 1,3/1,6 beta-glucan with equal sex representation within each treatment (8 dogs/diet). Animals were fed experimental diets for a 29d acclimation period, after which baseline blood samples were collected before administration of a combination canine distemper virus, parvovirus, and adenovirus-2 vaccine. Blood samples were collected weekly for 21d following vaccination with whole blood for CBC analysis, serum for titer and cytokine assays, and peripheral blood mononuclear cells (PBMC) isolated for flow cytometric immune cell profiling. Data were analyzed using the MIXED procedure with diet and timepoint fixed effects. Serum titer was analyzed by Kruskal-Wallis test (SAS 9.4; P≤0.05). Prior to vaccination, beta-glucan diets did not affect serum cytokines, antibody titer, or immune cell populations. In the first 7 days post-vaccination (dpv), PBMC CD21 low B cells increased in 36.5-58.1% in all groups but the magnitude of change was lesser in the 0.5X beta-glucan diet resulting in 25.6% lower CD21 low populations compared to control-fed dogs (P=0.007). By 21dpv, B cell populations recovered to baseline levels in dogs fed 1X beta-glucan, but CD21 high cells remained elevated 50.5% in dogs fed 0.5X beta-glucan diets compared to baseline (P<0.0001). While no differences in serum titer or cytokines were observed, feeding both beta-glucan diets maintained stable blood monocytes whereas a 53.0% decrease between baseline and 14dpv was observed in control-fed dogs (P=0.01). Collectively, these outcomes suggest that a 1X dose of 1,3/1,6 yeast beta-glucan in extruded kibble diets altered monocytes associated with trained immunity, did not reduce PBMC CD21 low B cell responsiveness, and simultaneously contributed to B cell population resolution by 21dpv in adult dogs. Additional research to assess the functionality of these changes is needed.

Evaluation of a yeast β-glucan blend in a pet food application to determine its impact on stool quality, apparent nutrient digestibility, and intestinal health when fed to dogs

“…The primary purpose of this study was to evaluate the impact of this specific yeast b-glucan on the immune response in dogs challenged with vaccine (Fries-Craft et al, 2023). The current work was intended to explore the potential side effects from yeast b-glucan on extrusion processing, stool quality, diet digestibility, or intestinal health in dogs.…”