Introduction: Mosquito-borne viruses continue to cause outbreaks of disease in Asia, Africa, Europe, the Americas and Australia, where an estimated 2 billion people are at risk of infection. Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that is the leading cause of viral encephalitis in Southeast Asia and is responsible for an estimated 70,000 cases per year. This year, an unprecedented outbreak of JEV occurred in Australia, affecting humans, pigs and horses, with transmission and cases detected in most states of the country. In this study, we assessed the ability of novel, recombinant viruses to act as diagnostic and vaccine antigens for the Australian outbreak strain of JEV.
Methods: A chimeric flavivirus displaying the virion surface proteins of the Australian outbreak strain of JEV (Genotype 4) and containing the backbone genome of the insect-specific Binjari virus (BinJV), was constructed using the circular polymerase extension reaction method (CPER), recovered in a mosquito cell line and designated BinJ/JEV. The ability of the recombinant virus to serve as a diagnostic antigen was assessed in a range of diagnostic assays. The immunogenicity of the chimeric virus was also assessed by immunising mice.
Results: We showed that the BinJ/JEV virus grew to high titres in insect cells while remaining replication defective in vertebrate cells. Furthermore, we showed that the chimeric virus particles were antigenically indistinguishable from the parental wild-type JEV and behaved similarly in a range of diagnostic assays, including ELISA, IFA and neutralisation tests. Mice immunised with purified BinJ/JEV virions also generated an immune response to JEV after a single vaccination.
Conclusion: The chimeric BinJ/JEV described here represents a promising recombinant platform for developing a safe an effective vaccine and diagnostic assays for JEV, with scope for efficient large-scale production without the requirement for PC3 biocontainment.