Chimeric classical swine fever (CSF)-Japanese encephalitis (JE) viral replicon as a non-transmissible vaccine candidate against CSF and JE infections.

A trans-complemented chimeric CSF-JE virus replicon was constructed using an infectious cDNA clone of the CSF virus (CSFV) Alfort/187 strain. The CSFV E2 gene was deleted, and a fragment containing the region encoding a truncated envelope protein (tE, amino acid 292-402, domain III) of JE virus (JEV) was inserted into the resultant plasmid, pA187delE2, to generate the recombinant cDNA clone pA187delE2/JEV-tE. Porcine kidney 15 (PK15) cells that constitutively express the CSFV E2p7 proteins were then transfected with in vitro-transcribed RNA from pA187delE2/JEV-tE. As a result, the chimeric CSF-JE virus replicon particle (VRP), rv187delE2/JEV-tE, was rescued. In a mouse model, immunization with the chimeric CSF-JE VRP induced strong production of JEV-specific antibody and conferred protection against a lethal JEV challenge. Pigs immunized with CSF-JE VRP displayed strong anti-CSFV and anti-JEV antibody responses and protection against CSFV and JEV challenge infections. Our evidence suggests that E2-complemented CSF-JE VRP not only has potential as a live-attenuated non-transmissible vaccine candidate against CSF and JE but also serves as a potential DIVA (Differentiating Infected from Vaccinated Animals) vaccine for CSF in pigs. Together, our data suggest that the non-transmissible chimeric VRP expressing foreign antigenic proteins may represent a promising strategy for bivalent DIVA vaccine design.