Expression and immunogenic analysis of recombinant polypeptides derived from capsid protein VP1 for developing subunit vaccine material against hepatitis A virus

Three recombinant polypeptides, VP1-His, VP1-3N-His, and 3D2-His, were produced by Escherichia coli expression system. Recombinant VP1-His, VP1-3N-His, and 3D2-His were expressed as bands with molecular weights of 32, 38, and 30 kDa, respectively. These were purified by affinity chromatography using Ni-NTA Fast-flow resin and/or ion-exchange chromatography using DEAE-Sepharose Fast-flow resin. Intraperitoneal immunizations of recombinant polypeptides successfully elicited the productions of VP1-His, VP1-3N-His, and 3D2-His specific IgG antibodies (IgG subclass distribution of IgG1 > IgG2a > IgG2b > IgG3) in sera and induced the secretions of cytokines IFN-γ and IL-6 in spleen cells. Sera from recombinant VP1-His-, VP1-3N-His-, and 3D2-His-immunized mice neutralized the propagation of HAV. The highest neutralizing activity was shown in sera from recombinant VP1-3N-His-immunized mice. These results suggest that recombinant VP1-3N-His can be a useful source for developing hepatitis A virus (HAV) subunit vaccine candidates.