Adjuvant effects of interleukin-18 in DNA vaccination against infectious bursal disease virus in chickens

► A DNA vaccine pCAGVP243 carrying VP243 gene of vvIBDV was evaluated in chickens. ► Plasmid pCAGVP243-IL-18 encoding both VP243 and chicken IL-18 was also constructed. ► Plasmid pCAGVP243-IL-18 induced higher levels of IBDV antibody than pCAGVP243. ► Plasmid pCAGVP243-IL-18 induced higher levels of IL-4 and IFN-γ than pCAGVP243. ► Plasmid pCAGVP243-IL-18 provided complete protection against vvIBDV challenge.