β-1,3/1,6-Glucan-supplemented diets antagonize immune inhibitory effects of hypoxia and enhance the immune response to a model vaccine

• Published in: Fish & shellfish immunology Vol. 59; pp. 36 - 45
• Main Authors: Rodríguez, Felipe E., Valenzuela, Beatriz, Farías, Ana, Sandino, Ana María, Imarai, Mónica
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.12.2016
• Subjects: Adaptative immune response; Adjuvants, Immunologic - administration & dosage; Anaerobiosis - immunology; Animal Feed - analysis; Animals; Astaxanthin; Atlantic salmon; Bacterial Vaccines - immunology; Cytokine; Cytokines - genetics; Cytokines - metabolism; Diet - veterinary; Dietary Supplements; Fish Proteins - genetics; Fish Proteins - metabolism; Gene expression; Gene Expression Regulation - immunology; Glucans; Hypoxia; Immunity; Immunity, Innate - immunology; Immunostimulants; Innate immune response; Random Allocation; Salmo salar; Salmo salar - genetics; Salmo salar - immunology; Salmo salar - metabolism; Salmonidae; Supplemented diets; Vaccine; Vaccines, Combined - immunology; Viral Vaccines - immunology; β-1,3/1,6-Glucan; Supplemented diets; Adaptative immune response; Astaxanthin; Cytokine; Immunostimulants; Hypoxia; Atlantic salmon; Vaccine; Gene expression; Immunity; Innate immune response; β-1,3/1,6-Glucan
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2016.10.020

The diets of farmed salmon are usually supplemented with immunostimulants to improve health status. Because β-glucan is one of the most common immunostimulants used in diets, here we examined the effect of two β-1,3/1,6-glucan-supplemented diets on the expression of immune response genes of Atlantic salmon. The relative abundances of IFN-α1, Mx, IFN-γ, IL-12, TGF-β1, IL-10, and CD4 transcripts were evaluated in head kidney by qRT-PCR. We assessed the effects of the diets under normoxia and acute hypoxia, as salmon are especially sensitive to changes in the concentration of dissolved oxygen, which can also affect immunity. These effects were also tested on vaccinated fish, as we expected that β-1,3/1,6-glucan-supplemented diets would enhance the adaptive immune response to the vaccine. We found that administration of the Bg diet (containing β-1,3/1,6-glucan) under normoxia had no effects on the expression of the analyzed genes in the kidney of the diet-fed fish, but under hypoxia/re-oxygenation (90 min of acute hypoxia), the βg diet affected the expression of the antiviral genes, IFN-α1 and Mx, preventing their decrease caused by hypoxia. The Bax diet, which in addition to β-1,3/1,6-glucan, contained astaxanthin, increased IL-12 and IFN-γ in kidneys. With fish exposed to hypoxia/reoxygenation, the diet prevented the decrease of IFN-α1 and Mx levels observed after hypoxia. When fish were vaccinated, only the levels of IL-12 and CD4 transcripts increased, but interestingly if fish were also fed the Bax diet, the vaccination induced a significant increase in all the analyzed transcripts. Finally, when vaccinated fish were exposed to hypoxia, the effect of the Bax diet was greatly reduced for all genes tested and moreover, inducible effects completely disappeared for IL-12, IFN-α, and Mx. Altogether, these results showed that the tested β-1,3/1,6-glucan diets increased the levels of transcripts of key genes involved in innate and adaptive immune response of salmon, potentiating the response to a model vaccine and also antagonizing the effects of hypoxia. •IFN-α1, Mx, IFN-γ, IL-12, TGF-β1, IL-10, and CD4 gene expression was examined in β-glucan-fed salmon.•Dietary β-1,3/1,6-glucan prevents down-regulation of IFN-α1 and Mx caused by hypoxia.•Diet containing β-1,3/1,6-glucan and astaxanthin induced IL-12 and IFN-γ expression in salmon.•β-1,3/1,6-Glucan diets improved immune response to a model vaccine used on salmon.