Molecular cloning and functional analysis of the duck TIR domain-containing adaptor inducing IFN-β (TRIF) gene

• This is the first report on the identification of a duck TRIF gene.
• The relative transcript level of duTRIF gene was upregulated in DEFs after different stimulation.
• Overexpression of duTRIF activated IFN-β promoter and NF-κB response promoter.
• The IFN induction function of duTRIF, in DEFs, was impaired when Ala517 is mutated to Pro or His.

Toll-like receptors (TLRs) trigger the innate immune response by responding to specific components of microorganisms. The TIR domain-containing adaptor inducing IFN-β (TRIF) plays an essential role in mammalian TLR-mediated signaling. The role of TRIF in ducks (duTRIF) remains poorly understood. In this study, we cloned and characterized the full-length coding sequence of duTRIF from duck embryo fibroblasts (DEFs). In healthy ducks, duTRIF transcripts were broadly expressed in different tissues, with higher expression levels in the spleen and liver. Using quantitative real-time PCR (qRT-PCR), we demonstrated the upregulation of duTRIF in DEFs infected with AIV or DTMUV, and DEFs treated with Poly I:C or LPS. Overexpression of duTRIF was able to induce the NF-κB and IFN-β expression. Furthermore, the IFN induction function of duTRIF was impaired when Ala517 was mutated to Pro or His. Taken together, these results suggested that duTRIF regulated duck innate immune responses.