Novel reverse genetics of genotype I and III Japanese encephalitis viruses assembled through transformation associated recombination in yeast: The reporter viruses expressing a green fluorescent protein for the antiviral screening assay.

Japanese encephalitis virus (JEV) belongs to a zoonotic flavivirus and is the main cause of viral encephalitis in humans throughout Asia. During the past two decades, both genotypes I (G) and III (GIII) JEVs co-existed in many Asian countries, and the prevalent strains have shifted from GIII to GI. Since all licensed JE vaccines are derived from GIII strains and no specific treatment is available, the development of novel vaccines and specific antiviral drugs against both genotypes is urgently required. To solve the unstable issue of the JEV infectious cDNA clone and establish a reliable antiviral screening assay, we established the yeast artificial chromosome (YAC)-based reverse genetics systems for GI and GIII JEV strains through transformation-associated recombination (TAR) technology in yeast. The YAC-based infectious clones of GI and GIII JEV exhibited high genetic stability both in yeast and E. coli. Using these reverse genetics systems, recombinant EGFP-reporter viruses were generated and remained stable for at least 10 passages in vitro. An image-based antiviral assay for JEV was developed with the EGFP-reporter viruses, and two drugs were identified to have a broad-spectrum inhibitory effect on GI and GIII JEV replication, which provide potential new therapeutic for the treatment of multiple genotypes JEV infection.