Generation and Efficacy of Two Chimeric Viruses Derived from GPE − Vaccine Strain as Classical Swine Fever Vaccine Candidates.

A previous study proved that vGPE⁻ mainly maintains the properties of classical swine fever (CSF) virus, which is comparable to the GPE⁻ vaccine seed and is a potentially valuable backbone for developing a CSF marker vaccine. Chimeric viruses were constructed based on an infectious cDNA clone derived from the live attenuated GPE⁻ vaccine strain as novel CSF vaccine candidates that potentially meet the concept of differentiating infected from vaccinated animals (DIVA) by substituting the glycoprotein E^rns of the GPE⁻ vaccine strain with the corresponding region of non-CSF pestiviruses, either pronghorn antelope pestivirus (PAPeV) or Phocoena pestivirus (PhoPeV). High viral growth and genetic stability after serial passages of the chimeric viruses, namely vGPE⁻/PAPeV E^rns and vGPE⁻/PhoPeV E^rns, were confirmed in vitro. In vivo investigation revealed that two chimeric viruses had comparable immunogenicity and safety profiles to the vGPE⁻ vaccine strain. Vaccination at a dose of 10^4.0 TCID₅₀ with either vGPE⁻/PAPeV E^rns or vGPE⁻/PhoPeV E^rns conferred complete protection for pigs against the CSF virus challenge in the early stage of immunization. In conclusion, the characteristics of vGPE⁻/PAPeV E^rns and vGPE⁻/PhoPeV E^rns affirmed their properties, as the vGPE⁻ vaccine strain, positioning them as ideal candidates for future development of a CSF marker vaccine. [ABSTRACT FROM AUTHOR]