Cloning and expression of hepatitis E virus ORF2 as a vaccine candidate

Introduction: Hepatitis E virus (HEV) is a fecal-oral transmitting virus which causes a chronic liver disease. ORF2 is an immunogen capsid protein of HEV that has been proposed to be used for Hepatitis E vaccine design. It is a 660-amino acid protein which includes an immunogenic region (residues 112-607). This protein has been expressed in complete and truncated forms, using different expression vectors such as pRSET-C, pMAL, pSG and baculovirus expression systems. Escherichia coli BL21 which is used as a host for protein expression was utilized as a host for pET26b vector in this study. We evaluated the expression of ORF2 as Hepatitis E vaccine candidate in presence of several IPTG concentrations. Methods: First, orf2 gene was sub-cloned into a pET26b vector which adds a C-terminal His-tag to the coding sequence. The procedure was confirmed by gel electrophoresis and double digestion. Subsequently, the recombinant pet26b-ORF2 was transformed into E. coli BL21 cells for protein expression and the resulted recombinant protein was analyzed by Bradford assay, SDS-PAGE and Western blotting. Results: SDS-PAGE and Western blotting confirmed the proper protein expression while there was no significant difference among the expressions of protein in presence of different IPTG concentrations. Conclusion: The expression of HEV ORF2 protein was successfully performed in E. coli BL21 and it showed that ORF2 can be expressed in presence of different concentration of IPTG with no significant difference in protein expression. The produced recombinant protein could be used in further vaccine-related studies and also its expression can be studied at several different temperatures.