Recombinant protein comprising multi-neutralizing epitopes induced high titer of antibodies against influenza A virus.

In previous studies, we suggested that epitope-vaccine might be a new strategy against virus infection. Based on this hypothesis, we designed and expressed a recombinant immunogen (multi-epitope-peptide) comprising repeats of three neutralizing-epitopes (neutralizing epitopes: aa92-105, 127-133 and 183-195) of hemagglutininin (HA) of influenza virus (H3N2) in E. coli. After vaccination, the recombinant multi-epitope protein could induce a high level of antibodies with predefined multi-epitope-specificity in mice and rabbits. The epitope-specific antibodies in sera were tested using three different epitope-peptides (synthetic peptides) in ELISA assay, and the serum dilutions from 1 : 6400 to 1 : 25600 were confirmed. In western blot analysis, both the antiserum and the antibodies purified by synthetic epitope-peptide coupled sepharose columns could recognize natural HA from influenza virus particles (strain A/Wuhan/359/95 H3N2). In hemagglutination inhibition (HI) tests, these three antisera at the dilutions from 1 : 20 to 1 : 80 showed inhibitory activity. Interestingly, antisera and purified antibodies induced by the epitope-vaccine could partially inhibit plaque-formation of influenza virus (strain A/Wuhan/359/95) on MDCK cell monolayers. These results suggest that the recombinant multi-epitope vaccine can simultaneously induce multi-antiviral activities against influenza virus, which may provide a new way to develop effective vaccines against influenza virus.