Abstract
Newcastle disease (ND) and infectious bursal disease (IBD) are both one of the most economically important infectious diseases, which cause high infection rate and mortality of chickens and restrict the development of the poultry industry. Currently, vaccination is the most effective method to prevent ND and IBD. In this study, the biological adjuvant bivalent vaccine (rClone30-VP2L-chGM-CSF) was developed for preventing ND and IBD. Furthermore, the immune and protective effects of rClone30-VP2L-chGM-CSF were evaluated in specific-pathogen-free chickens. The experimental results indicated that chickens immunized with rClone30-VP2L-chGM-CSF vaccine significantly improved anti-IBDV and anti-NDV antibody titer; the level of CD4(+) T, CD8(+) T, B(+), MHC-II(+), and monocyte/macrophagocyte+ cells; the concentrations of IL-1β, IL-4, IL-17, IFN-α, IFN-β, and IFN-γ; and the splenocyte proliferation rate. Anti-NDV antibody titer reached the theoretical protection value of 4log2 at 7 days after immunization in chickens of rClone30-VP2L-chGM-CSF group; however, which at 14 days after immunization in chickens of rClone30-VP2L and rClone30. These results showed that chickens immunized with rClone30-VP2L-chGM-CSF stimulated stronger immune response than those with the rClone30-VP2L and rClone30. Chickens were challenged with virulent IBDV BC6/85, which were protected in the rClone30-VP2L-chGM-CSF group. Furthermore, IBDV RNA was not measured, and there appeared to be little apoptosis in the bursa of Fabricius in the rClone30-VP2L-chGM-CSF group. Therefore, rClone30-VP2L-chGM-CSF is a promising vaccine candidate against infectious bursal disease virus (IBDV) and newcastle disease virus (NDV), and it provides an idea for developing other poultry vaccines.