Adjuvant activity of chicken interleukin-12 co-administered with infectious bursal disease virus recombinant VP2 antigen in chickens

A recombinant fowlpox virus (rFPV/VP2) expressing infectious bursal diseases virus (IBDV) VP2 gene has been constructed. After purification and identification of rFPV/VP2, the adjuvant activity of the recombinant chicken IL-12 (rchIL-12), synthesized by our previous construct of rFPV/chIL-12, in rFPV/VP2-expressed rVP2 antigen was assessed in one-week-old specific-pathogen free chickens. The results indicated that rchIL-12 alone or rchIL-12 plus mineral oil (MO) co-administered with rVP2 antigen significantly enhanced the production of serum neutralization (SN) antibody against IBDV, compared to those with MO alone. The SN titers in groups receiving rVP2 antigen with MO alone were more inconsistent after vaccination. On the other hand, rchIL-12 significantly stimulated IFN-γ production in serum and in splenocyte cultured supernatant, suggesting that rchIL-12 alone or plus MO significantly induced a cell-mediated immune response. Finally, bursal lesion protection from very virulent IBDV (vvIBDV) challenge in chickens receiving rVP2 antigen with rchIL-12 alone or plus MO was much more effective than that with MO alone at two weeks after boosting. Taken together, rchIL-12 alone augmented in vivo the induction of a primary and also a secondary SN antibody production and a cell-mediated immunity against IBDV rVP2 antigen, which conferred the enhancement of bursal lesion protective efficacy from vvIBDV challenge. These data indicated that a potential for chIL-12 as immunoadjuvant for chicken vaccine development such as IBDV rVP2 antigen.