Molecular cloning and functional characterization of duck TYK2

Characterization of duck IκB kinase β involved in innate immunity

IκB kinase β (IKKβ), a catalytic subunit of the IKK complex, is involved in a wide array of biological processes, particularly in inflammation and innate immunity. Although extensive studies have been carried out to explore the roles of mammalian IKKβs in innate immune response, the function of IKKβ in avian innate immunity is largely unknown. Here, we cloned and characterized the duck IKKβ (duIKKβ) gene for the first time. DuIKKβ encoded 755 amino acids and displayed high sequence similarity to pseudopodoces and haliaeetus IKKβs. DuIKKβ transcripts were widely distributed in all tested tissues, especially with high expression in the thymus and bursa of Fabricius. Overexpression of duIKKβ promoted NF-κB activation and initiated the downstream cytokines expression including IFN-β, ZAP, PKR, IL-8, and CCL5 in duck embryo fibroblasts. Furthermore, knockdown of endogenous duIKKβ significantly reduced LPS-, poly(I:C)- or SeV-induced NF-κB activation. Finally, we demonstrated that duIKKβ showed antiviral activity against Duck Tembusu virus infection. Our findings provide insights into the roles of duIKKβ in avian innate immunity.

Molecular characterization and functional analysis of duck IKKα

IκB kinase α (IKKα) is a vital component of the IKK complex, which is involved in innate immune response, inflammation, cell death and proliferation. Although the functional characteristics of IKKα have been extensively studied in mammals and fish, the roles of IKKα in avian remain largely unknown. In this study, we cloned and characterized the duck IKKα (duIKKα) gene for the first time. DuIKKα encoded a protein of 757 amino acid residues and showed high sequence identities with the goose IKKα. The duIKKα was expressed in all tested tissues, and a relatively high expression of duIKKα mRNA was detected in liver and heart. Overexpression of duIKKα dramatically increased NF-κB activity and induced the expression of duck cytokines IFN-β, IL-1β, IL-6, IL-8 and RANTES in DEFs. Knockdown of duIKKα by small interfering RNA significantly decreased LPS-, poly(I:C)-, poly(dA:dT)-, duck enteritis virus (DEV)-, or duck Tembusu virus (DTMUV)-induced NF-κB activation. Moreover, duIKKα exhibited antiviral activity against DTMUV infection. These findings provide important insights into the roles of duIKKα in avian innate immunity.

Innate immune responses to duck Tembusu virus infection

The disease caused by duck Tembusu virus (DTMUV) is characterized by severe egg-drop in laying ducks. Currently, the disease has spread to most duck-raising areas in China, leading to great economic losses in the duck industry. In the recent years, DTMUV has raised some concerns, because of its expanding host range and increasing pathogenicity, as well as the potential threat to public health. Innate immunity is crucial for defending against invading pathogens in the early stages of infection. Recently, studies on the interaction between DTMUV and host innate immune response have made great progress. In the review, we provide an overview of DTMUV and summarize current advances in our understanding of the interaction between DTMUV and innate immunity, including the host innate immune responses to DTMUV infection through pattern recognition receptors (PRRs), signaling transducer molecules, interferon-stimulated genes (ISGs), and the immune evasion strategies employed by DTMUV. The aim of the review is to gain an in-depth understanding of DTMUV pathogenesis to facilitate future studies.