A 27 amino acid coding region of JE virus E protein expressed in E. coli as fusion protein with glutathione-S-transferase elicit neutralizing antibody in mice.

We have recently shown that neutralizing epitope(s) exist near the C-terminal of JE virus E-protein by expressing the coding gene cDNA fragments as fusion proteins with protein A. Among four cDNA fragments, the fragment (B3) carrying the coding sequence of amino acid number 373-399 of E protein elicited the highest neutralizing (N) antibody titer (1:75). To exclude the possible influence of protein A contained in the expressed gene products on the mouse immune response, we expressed (B3) using pGEX-3X expression vector as fusion with glutathione-S transferase (GST). The mice immunized with recombinant GST-B3 fusion protein induced an immune response (mean average ELISA: 3364; N: 1:75) almost similar to that by recombinant protein A-B3 fusion protein (mean average ELISA: 3476; N: 1:75). While hemagglutination-inhibition (HI) antibodies were not induced by this fusion protein. These results indicate that 27 amino acid sequence on the E protein (373-399) was sufficient to induce neutralizing antibodies without association with protein A moiety.