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-mtransferase (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.