Molecular cloning and functional characterization of duck DDX41

DEAD (Asp-Glu-Ala-Asp) box polypeptide 41 (DDX41), a receptor belonging to DExD/H-box helicase family, acts as an intracellular DNA sensor and induces type I IFN production in mammals and fish. However, the function of avian DDX41 in innate immune response is still unknown. In this study, the full-length duck DDX41 (duDDX41) cDNA sequence was cloned for the first time and encoded a putative protein of 618 amino acid residues which showed the high sequence similarity with both zebra finch and chicken DDX41s. The duDDX41 mRNA was widely distributed in all tested tissues, especially the cerebrum, cerebellum, and liver. Overexpression of duDDX41 triggered the activation of transcription factors IRF1 and NF-κB, as well as IFN-β expression in DEFs. The DEADc domain of duDDX41 played an extremely vital role in duck type I IFN signaling pathway. Knockdown of duDDX41 by siRNA silencing dramatically decreased IFN-β expression stimulated by poly(dA:dT) or duck enteritis virus (DEV). In addition, the replication of DEV was significantly inhibited in duDDX41-expressed DEFs and was enhanced in DDX41 knockdown DEFs. These results suggest that DDX41 is an important cytosolic DNA sensor and plays a crucial role in duck antiviral innate immune response.