Alaa A El-Kholy, Hussien M Ghaly and Ahmed M Daoud.
Veterinary Sera and Vaccines Researches Institute (VSVRI), ARC, Abbassia, Cairo, Egypt.
Two groups of calves were vaccinated with a double recombinant baculovirus expression product of a previously developed construct (rec-NE0), expressing the nucleoprotein (N) and the envelope glycoprotein (E0) of the NADL strain of bovine viral diarrhea virus (BVDV). The baculovirus expression product, in rec-NE0 vaccine, were immunogenic in calves as viral neutralizing antibody (VN-Ab) titers of 2 to 8 were detectable following booster vaccination. Vaccinated and non-vaccinated calves were challenge exposed with either the homologous BVDV1-NADL or the local heterologous BVDV2-Iman strains. Vaccine-induced immunity conferred partial protection against homologous viral challenge exposure, focused in reducing severity and duration of clinical signs of disease, compared to non-vaccinated calves. However, neither systemic spread nor shedding of the challenge virus could be prevented by vaccination. The rec-NE0 vaccine could not cross-protect calves against heterologous virus challenge exposure. Findings of this study suggest that N and E0 regions of the BVDV genome comprise important antigenic epitopes. Furthermore, they share a role in protective immunity against BVDV infection. Immunogenicity of N and E0 along with the existing antigenic diversity among viruses should be considered in future development of recombinant vaccines for pestivirus control.