LAUSR

ABSTRACT Application of yeast is increasing to improve welfare and promotes growth in aquaculture. The halotolerant yeast Debaryomyces hansenii is normally a non‐pathogenic yeast with probiotic properties and potential source of antioxidant enzymes as superoxide dismutase. Here, first, we characterized the sequence features of MnSOD and icCu/ZnSOD from Pacific red snapper, and second, we evaluated the potential antioxidant immune responses of the marine yeast Debaryomyces hansenii strain CBS004 in leukocytes which were then subjected to Vibrio parahaemolyticus infection. In silico analysis revealed that LpMnSOD consisted of 1186 bp, with an ORF of 678 bp encoding a 225 amino acid protein and LpicCu/ZnSOD consisted of 1090 bp in length with an ORF of 465 bp encoding a 154 amino acid protein. Multiple alignment analyzes revealed many conserved regions and active sites among its orthologs. In vitro assays using head‐kidney and spleen leukocytes immunostimulated with D. hansenii and zymosan in response to V. parahaemolyticus infection reveled that D. hansenii strain CBS004 significantly increased transcriptions of MnSOD and icCu/ZnSOD genes. Flow cytometry assay showed that D. hansenii was able to inhibit apoptosis caused by V. parahaemolyticus in the Pacific red snapper leukocytes and enhanced the phagocytic capacity in head‐kidney leukocytes. Immunological assays reveled an increased in superoxide dismutase and peroxidase activities, as well as, in nitric oxide production and reactive oxygen species production (respiratory burst) in fish stimulated with D. hansenii. Finally, our results. These results strongly support the idea that marine yeast Debaryomyces hansenii strain CBS004 can stimulate the antioxidant immune mechanism in head‐kidney and spleen leukocytes. HighlightsMn‐SOD, icCU/Zn‐SOD and catalase genes were identified and characterized in Pacific red snapper.D. hansenii stimulate antioxidant immune‐related gene expression.D. hansenii protects leucocytes against the pathological damages of V. parahaemolyticus.D. hansenii increased phagocytosis activity and cell viability of fish leucocytes.D. hansenii reduced necrotic cell death provoked by V. parahaemolyticus.Antioxidant immune parameters are enhanced by D. hansenii.