Expression and Immunogenic Analysis of Recombinant Capsid Protein VP1 for Developing Subunit Vaccine Against Hepatitis A Virus

Hepatitis A virus (HAV) causing an acute viral hepatitis disease in human belongs to a picornavirus with a positive single-stranded RNA genome coding a single polyprotein that subsequently processed into structural and nonstructural proteins. Capasid protein VP1 is an immunodominant structural protein among the HAV capsid proteins. Synthetic peptides derived from N-terminal region of VP1 showed high antigenic activities. D2 peptide including C-terminal 31 amino acid residues of VP1 and 2A has been proved to induce virus-neutralizing antibody responses. To develop subunit vaccine against HAV, several peptides including full length VP1, N-terminal VP1 (VP1-N) and D2 were produced by Escherichia coli expression system. Recombinant VP1 was expressed as a band with molecular weight of 32 kDa. Molecular weights of recombinant VP1-N and D2 were 37 and 30 kDa, respectively. Recombinant VP1, VP1-N and D2 were purified by affinity chromatography using Ni-NTA resin and/or ion-exchange chromatography using DEAE-sepharose resin. Intraperitoneal immunizations of recombinant VP1, VP1-N and D2 successfully elicited the productions of VP1, VP1-N and D2 specific IgG in sera and induced the secretions of cytokines IFN-γ and IL-6 in spleen cells. Sera of recombinant VP1, VP1-N and D2-immunized mice contained the neutralizing activity to inhibit the propagation of HAV. The highest neutralizing activity was shown in sera of recombinant VP1-N-immunized mice. These results suggest that recombinant VP1-N can be the most useful source for HAV subunit vaccine development. This work was supported by a grant from the Next-Generation BioGreen 21 Program (PJ009553), Rural Development Administration, Republic of Korea.