Human
interferon regulatory factor 7 (IRF7) plays an important role in the innate
antiviral immune response. To date, the characteristics and functions of waterfowl IRF7 have not been clarified. This study reports the
cDNA sequence, tissue distribution, and
antiviral function of duck IRF7. The duck IRF7 gene has a 1536-bp open read frame (ORF) and encodes a 511-amino
acid polypeptide. IRF7 is highly expressed in the blood and pancreas of 5-day-old ducklings and in the small intestine, large intestine and liver of 60-day-old adult ducks. Indirect immunofluorescence assay (IFA) showed that over-expressed duck IRF7 was located in both the cytoplasm and nucleus of transfected duck embryo fibroblasts (DEFs), which was also observed in
poly(I:C)-stimulated or duck Tembusu virus (DTMUV)-infected DEFs. Titres and copies of DTMUV were significantly reduced in DEFs overexpressing IRF7. Moreover, overexpression of duck IRF7 significantly induced IFNα/β, but not IFNγ,
mRNA expression, and transcription of downstream
interferon-stimulated genes (ISGs), such as MX, OASL and
IL-6, which were significantly induced by
poly(I:C) co-stimulation, was enhanced. Additionally, duck IRF7 overexpression can significantly activate the IFNβ promoter in DEFs. Collectively, duck IRF7 plays an important role in host anti-DTMUV immune regulation, which depends on
type I interferons and associated signal transduction pathway(s).