Selection of immunodominant fragments from envelope gene for vaccine against Japanese encephalitis virus in DNA priming-protein boosting protocols

Fragmentation of E gene of JEV into smaller fragments, none of the fragments either in plasmids form or in recombinant protein form can induce optimal protection against the virus infection. It is only when DNA priming-protein boosting strategies are used then the N-terminal EA and the C-terminal EB showed full protection against JEV as those induced by commercial vaccine, provided both fragments are preceded in the N-terminal by a signal peptide M15 derived from C-terminal of prM gene in JEV genome. When the subfragments of EA: EA1 and EA2 and EB: EB1 and EB2 are tested, only EA1 subfragment can replace EA in protein boosting to induce optimal protection against JEV, EA2, EB1, EB2 in plasmid or protein forms are not. Therefore, along the E gene (978-2330 bp) N-terminal, EA1 (978-1580 bp) and C-terminal EB (1851-2330 bp) are the most effective in inducing immunity against JEV but not the middle fragment EA2 (1518-1877 bp) (see Fig. 1 for orientation of EA1, EA2 and EB in E gene). Under the notion that molecular complexity determines the outcome of immune response of the host, EB being shorter, simpler in molecular structure and can be easily expressed in soluble form in E. coli (as opposed to insoluble EA1), EB probably will be the choice as a candidate vaccine to protect the host against JEV infection.