Novel BPI3Vc-vectored chimeric BVDV antigens elicit broadly neutralizing antibodies in cattle

Bovine Viral Diarrhea Virus (BVDV) is a key contributor to the development of Bovine Respiratory Disease complex, which can cause respiratory disease, congenital defects, severe diarrhea, immunosuppression, abortion, or birth of persistently infected calves. Current commercial vaccines are formulated using strains from BVDV-1a and BVDV-2a, conferring protection against some, but not all, homologous species and low neutralization titers against heterologous and emergent species. This study aimed to develop a live vaccine capable of inducing broad protection against diverse BVDV strains. A contemporary live-attenuated BPI3Vc-vectored BVDV prototype vaccine was developed. Novel chimeric BVDV E2-NS2-5^1-2 antigens, designed based on the consensus of all BVDV-1a, -1b, -2a, -2b, and -2c protein sequences, were used to generate recombinant BPI3Vc_mutantE2-NS2-5^1-2 viruses. The recombinant viruses expressed all the ~5kb encoded transgenes, replicated efficiently, remained genetically stable over nine passages in vitro, and displayed the E2 ectodomain on the surface of infected cells. Intranasal immunization of calves with a cocktail of these recombinant viruses, designated rBPI3Vc_mutBVDV, elicited strong serum antibodies against BVDV-1 and -2 viruses compared to a commercial vaccine. Notably, vaccination elicited stronger IgG responses against BVDV-1b CA0401186a and TGAC, with significantly higher virus-neutralizing titers than the commercial vaccine (CA0401186a: p=0.0031; TGAC: p=0.0002). Immunized calves also elicited significantly higher VN titers against BVDV-2a strains 296NC (p=0.0006), 890 (p=0.0020), 296C (p=0.0464), A125 (p=0.0018), and 1373 (p=0.0025). Upon challenge with BVDV-1b CA0401186a, the rBPI3Vc_mutBVDV vaccinees exhibited a steady weight gain, less decrease in lymphocyte counts, lower viremia, and fewer gross lesions. This data supports use of the live-attenuated BPI3Vc-vector for development of contemporary broadly protective BVDV vaccines that can easily be upgraded for improved disease management and cattle productivity.