A Novel Bicistronic Adenovirus Vaccine Elicits Superior and Comprehensive Protection Against BVDV

Bovine viral diarrhea virus (BVDV) is a major pathogen inflicting substantial economic losses on the global cattle industry. To develop a more effective vaccine, we constructed two novel bicistronic recombinant adenoviruses, rAdV-I E0+I E2 and rAdV-I E2+II E2, and systematically evaluated their immunogenicity and protective efficacy in BALB/c mice. Both vaccine candidates, particularly rAdV-I E2+II E2, provoked a robust and rapid neutralizing antibody response that was significantly superior to a commercial inactivated vaccine. They also elicited a potent Th1-skewed cellular immune response, as indicated by significantly higher IFN-γ secretion, and a balanced profile of BVDV-specific IgG and its subclasses. Upon BVDV challenge, immunization with both recombinant vaccines, especially rAdV-I E2+II E2, resulted in a comprehensive reduction in viral loads across all tested tissues (blood, spleen, lungs, kidneys, and small intestine), demonstrating broader protection than the inactivated vaccine. Concordantly, histopathological analysis confirmed that vaccination preserved the normal architecture of the duodenum and spleen, preventing the significant pathological damage observed in the rAdV-empty negative control group. Our findings demonstrate that these adenovirus-vectored vaccines, particularly rAdV-I E2+II E2, induce a multifaceted and protective immune response, highlighting their promise as superior candidates against BVDV.