A chimeric vaccine derived from Australian genotype IV Japanese encephalitis virus protects mice from lethal challenge.

In 2022, a genotype IV (GIV) strain of Japanese encephalitis virus (JEV) caused an unprecedented and widespread outbreak of disease in pigs and humans in Australia. As no veterinary vaccines against JEV are approved in Australia and all current approved human and veterinary vaccines are derived from genotype (G) III JEV strains, we used the recently described insect-specific Binjari virus (BinJV) chimeric flavivirus vaccine technology to produce a JEV GIV vaccine candidate. Herein we describe the production of a chimeric virus displaying the structural prM and E proteins of a JEV GIV isolate obtained from a stillborn piglet (JEV) in the genomic backbone of BinJV (BinJ/JEVprME). BinJ/JEVprME was shown to be antigenically indistinguishable from the JEV parental virus by K analysis and a panel of JEV-reactive monoclonal antibodies in ELISA. BinJ/JEVprME replicated efficiently in C6/36 cells, reaching titres of >10 infectious units/mL - an important attribute for vaccine manufacture. As expected, BinJ/JEVprME failed to replicate in a variety of vertebrate cells lines. When used to immunise mice, the vaccine induced a potent virus neutralising response against JEV and to GII and GIII JEV strains. The BinJ/JEVprME vaccine provided complete protection against lethal challenge with JEV, whilst also providing partial protection against viraemia and disease for the related Murray Valley encephalitis virus. Our results demonstrate that BinJ/JEVprME is a promising vaccine candidate against JEV.