Comparativeimmunogenicity of bivalent ND-IBD vaccine and their impact on NDV replication

Newcastle disease (ND) and infectious bursal disease (IBD) are economically significant infectious diseases. This study developed two bivalent vaccines, rClone30+VP2 neutralizing epitope antigen (VP2L)and rClone30-VP2L,to prevent ND and IBD. Results demonstrated that the rClone30-VP2L vaccine significantly increasedthe anti-Newcastle disease virus (NDV) antibody levels, achieving a protective titer of 4log2 by day 7 post-immunization, whereas the rClone30+VP2L and rClone30 groups reached this level by day 14. Chickens immunized with rClone30+VP2L exhibited elevated levelsof CD4+ T cells, CD8+ T cells, B cells, MHC-II+ cells, and cytokines (IFN-α, IFN-β, IFN-γ, IL-1β, and IL-4) at 3-7 days post-immunization, while the rClone30-VP2L group showed similar enhancements at 7-21 days.These results suggestthat rClone30+VP2L enhances early immune responses, potentially affecting NDV replication and reducing vaccine efficacy in later stages. Real-time PCR, Western Blot, and IFA confirmed higher NDV content in the rClone30-VP2L and rClone30 groups. Thus, rClone30-VP2L demonstrates superior immunogenicity compared to rClone30+VP2L, offering a promising candidate for ND and IBD prevention and insights for developing vaccines against other viral infections.