Development and immunological evaluation of a multi-antigen recombinant adenovirus vaccine candidate against PRRSV and PCV2.

In this study, a recombinant adenovirus vaccine candidate constructed and evaluated to addressed the widespread clinical problem of co-infections of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) and Porcine Circovirus Type 2 (PCV2). Epidemiological analysis revealed a PRRSV-positive rate of 40.8%, with prevalent strains belonging to Lineage 1 and Lineage 8. Analysis of key amino acid sites in the GP5 protein indicated the presence of highly virulent strain characteristics and widespread wild-type strain variation. Based on these findings and previous studies, we selected multiple PRRSV proteins (GP2-GP5, M, N) from multiple strains and the validated PCV2 Cap protein fused with dominant T/B cell epitopes, and successfully constructed four recombinant adenoviruses using a 2A peptide-linked strategy. These constructs stably expressed the target antigens in HEK293 cells and demonstrated good passage stability. Animal experiments showed that piglets immunized with the recombinant adenoviruses developed high levels of PRRSV- and PCV2-specific antibodies and neutralizing antibodies, and exhibited lymphocyte proliferation and secretion of cytokines including IFN-γ, IL-2, and IL-4, indicating the vaccine simultaneously elicited both humoral and cellular immune responses. Following PRRSV challenge, immunized groups, particularly the multi-antigen combined immunization group, demonstrated significant clinical protection. This study provides a promising vaccine candidate and a theoretical foundation for the coordinated control of PRRSV and PCV2.