Avipox virus-vectored Japanese encephalitis virus vaccines: use as vaccine candidates in combination with purified subunit immunogens.

An avipox virus, canarypox (ALVAC), which is naturally host-range restricted, was used to construct recombinants encoding the Japanese encephalitis virus (JEV) prM, E and NS1 genes (vCP107) and prM and E genes (vCP140). Mice immunized with these recombinant viruses produced JEV neutralizing antibodies and were protected from lethal JEV challenge. Protection was also observed in mice immunized with a subunit vaccine candidate, consisting of extracellular particles (EPs; RNA-free subviral membrane vesicles containing prM/M and E proteins) derived from HeLa cell cultures infected with a JEV-vaccinia recombinant. Mice primed with vCP107 and boosted with EPs had higher antibody levels than mice immunized twice with EPs alone, although the levels were comparable to that obtained in mice immunized twice with the recombinant virus. Mice immunized with a mixture of recombinant virus (vCP107) plus EPs had neutralizing antibody titres higher than mice immunized with the recombinant virus or EPs alone.