Immunostimulatory effect of DDX41 of olive flounder (Paralichthys olivaceus)

Abstract

The cellular DEAD-box helicase DDX41, which functions as an initial sensor for cytoplasmic DNA, is involved in the activation of type I interferon (IFN-1) immune response in olive flounder. A plasmid encoding DDX41 (pEF-D) was introduced into flounder cells in vitro and in vivo. Immune responses induced by DDX41 were evaluated by relative quantification value (Delta Delta Ct) method of RT-qPCR using specific IFN-related gene primers. Results in in vitro, transcript levels of IFN-1, IRF-3, ISG-15 and IL-1 beta were significantly higher in pEF-D- than pEF-A-transfected cells, with 15-, 4-, 10- and 32-fold changes, respectively. In vivo, elevated expression of these genes was observed in the kidney of pEF-D group on days 1 and 3 post-treatment. The viral challenge test revealed higher survival rate in fish treated with pEF-D (67.5%) than controls, PBS- and pEF-A-treated fish (45%). Conclusively DDX41 elicits a robust IFN-mediated immune response, validating its adjuvant property.