High-level expression of the Japanese encephalitis virus E protein by recombinant vaccinia virus and enhancement of its extracellular release by the NS3 gene product.

Recombinant vaccinia viruses expressing the prM and E genes of the Japanese encephalitis virus (JEV) were constructed by use of synthetic promoters. While the recombinant virus mOJ6-SL, with an optimized vaccinia late-gene promoter, produced a 20-fold elevated level of E protein, as well as an 86-kDa precursor protein in infected cells, no significant quantitative difference was detected between the extracellular or cell-surface E protein produced by mOJ6-SL and those produced by mOJ6 with the 7.5-kDa promoter. However, when the cells were infected with Dengue 2 virus before infection with mOJ6-SL, the amount of the extracellular E protein increased 16-fold. In addition, enhancement of its extracellular release was observed when cells were co-infected with mOJ6-SL and recombinant vaccinia virus expressing the NS3 gene of JEV.