B-glucan immunostilulation against columnaris in a white sturgeon (Acipenser transmontanus) model

Flavobacterium columnare represent one of the most important bacterial pathogens of cultured sturgeon. However, at present there are no commercially available vaccines to prevent infection and treatment options are limited. β-glucans have been shown to be potent immunostimulants that can provide fish protection against infectious disease. In this study, the effects of dietary β-glucan supplementation on disease susceptibility were examined by exposing 0.3% β-glucan-fed white sturgeon (Acipenser transmontanus) to Flavobacterium columnare in laboratory-controlled challenges. Morbidity and mortality were monitored for 15 days post-challenge (dpc). Additionally, transcript levels for pro-inflammatory cytokines, regulatory cytokines and acute phase proteins (APP) were investigated in the spleen and gills at different time points post-challenge. No evidence of protection was observed in β-glucan-fed fish challenged with the bacteria. Moreover, significantly greater mortalities were observed in β-glucan-fed fish challenged with F. columnare (p<0.05), likely associated with acute inflammatory response as haptoglobin and serotransferrin transcripts in the gills were significantly higher in fish within this group at 1 dpc. Transcript levels for all tested cytokines and APP in the spleen were similar amongst treatment groups. The results from this study suggest that β-glucan supplementation at the concentration and rate investigated provides no-benefit to white sturgeon against F. columnare.