Porcine Adenovirus-Based Viral Vectors for Swine Vaccines: A Scoping Review and Future Perspectives

Porcine adenoviruses (PAdVs) are promising but still underdeveloped viral-vector platforms for swine vaccine development. Compared with human adenovirus-based vectors, PAdV vectors may offer potential advantages in host association, veterinary relevance, and mucosal delivery while avoiding direct reliance on common human adenovirus backbones. This review summarizes current knowledge on PAdV biology, vector engineering, vaccine applications, immune responses, translational challenges, and future priorities. Early studies showed that recombinant PAdV vectors can express heterologous antigens from important swine pathogens, including classical swine fever virus, pseudorabies virus, and transmissible gastroenteritis virus. The strongest direct proof-of-concept evidence comes from recombinant PAdV expressing classical swine fever virus E2/gp55, which induced neutralizing antibodies and protection in pigs. Comparative adenovirus-vectored swine vaccine studies support the broader feasibility of adenoviral antigen delivery for porcine reproductive and respiratory syndrome, porcine epidemic diarrhea, swine influenza, and African swine fever, but these data should not be interpreted as direct validation of PAdV for these diseases. Major gaps remain in anti-PAdV immunity, genetic stability, biosafety, shedding, target-animal safety, DIVA compatibility, manufacturing, and regulatory readiness. Recent advances in PAdV-5 reverse genetics provide new opportunities for modern vector design.