Plasmid DNA launches live-attenuated Japanese encephalitis virus and elicits virus-neutralizing antibodies in BALB/c mice

We describe novel plasmid DNA that encodes the full-length Japanese encephalitis virus (JEV) genomic cDNA and launches live-attenuated JEV vaccine in vitro and in vivo. The synthetic cDNA based on the sequence of JEV SA14-14-2 live-attenuated virus was placed under transcriptional control of the cytomegalovirus major immediate-early promoter. The stability and yields of the plasmid in E. coli were optimized by inserting three synthetic introns that disrupted JEV cDNA in the structural and nonstructural genes. Transfection of Vero cells with the resulting plasmid resulted in the replication of JEV vaccine virus with intron sequences removed from viral RNA. Furthermore, a single-dose vaccination of BALB/c mice with 0.5 − 5μg of plasmid resulted in successful seroconversion and elicitation of JEV virus-neutralizing serum antibodies. The results demonstrate the possibility of using DNA vaccination to launch live-attenuated JEV vaccine and support further development of DNA-launched live-attenuated vaccine for prevention of JEV infections. •Novel iDNA plasmid was developed to improve vaccination against JEV flavivirus.•The iDNA platform combines advantages of DNA immunization and live attenuated vaccine.•Only 10ng of JEV iDNA plasmid initiated replication of live JEV vaccine virus in vitro.•BALB/c mice vaccinated with a single dose of JEV iDNA plasmid have seroconverted.•Virus-specific neutralizing response was elicited in vaccinated mice.