A Recombinant Novirhabdovirus Presenting at the Surface the E Glycoprotein from West Nile Virus (WNV) Is Immunogenic and Provides Partial Protection against Lethal WNV Challenge in BALB/c Mice

West Nile Virus (WNV) is a zoonotic mosquito-transmitted flavivirus that can infect and cause disease in mammals including humans. Our study aimed at developing a WNV vectored vaccine based on a fish Novirhabdovirus, the Viral Hemorrhagic Septicemia virus (VHSV). VHSV replicates at temperatures lower than 20°C and is naturally inactivated at higher temperatures. A reverse genetics system has recently been developed in our laboratory for VHSV allowing the addition of genes in the viral genome and the recovery of the respective recombinant viruses (rVHSV). In this study, we have generated rVHSV vectors bearing the complete WNV envelope gene (E(WNV)) (rVHSV-E(WNV)) or fragments encoding E subdomains (either domain III alone or domain III fused to domain II) (rVHSV-DIII(WNV) and rVHSV-DII-DIII(WNV), respectively) in the VHSV genome between the N and P cistrons. With the objective to enhance the targeting of the E(WNV) protein or E(WNV)-derived domains to the surface of VHSV virions, Novirhadovirus G-derived signal peptide and transmembrane domain (SP(G) and TM(G)) were fused to E(WNV) at its amino and carboxy termini, respectively. By Western-blot analysis, electron microscopy observations or inoculation experiments in mice, we demonstrated that both the E(WNV) and the DIII(WNV) could be expressed at the viral surface of rVHSV upon addition of SP(G). Every constructs expressing E(WNV) fused to SP(G) protected 40 to 50% of BALB/cJ mice against WNV lethal challenge and specifically rVHSV-SP(G)E(WNV) induced a neutralizing antibody response that correlated with protection. Surprisingly, rVHSV expressing E(WNV)-derived domain III or II and III were unable to protect mice against WNV challenge, although these domains were highly incorporated in the virion and expressed at the viral surface. In this study we demonstrated that a heterologous glycoprotein and non membrane-anchored protein, can be efficiently expressed at the surface of rVHSV making this approach attractive to develop new vaccines against various pathogens.