Abstract:

Objective To compare the immunogenicity between the genetically engineered recombinant antigen and the traditional vaccine against hepatitis A virus(HAV) and study the ability of expressing different antigens by the same vector and the interaction among the different antigens. Methods Plasmid pBV220-EAAg342 and pBV220-AEAg342 constructed previously which code for HAV vp1 aa24-171 and hepatitis E virus(HEV) ORF2 aa431-615 genes were amplified and identified, then transformed into E.coliBL21 and induced to express the target protein. The expressed proteins were purified by DEAE-Sepharose and CM-Sepharose, identified by SDS-PAGE and Western blotting. KM mice were immunized with the purified recombinant antigen and the traditional HAV inactivated vaccine and the attenuated live vaccine by subcutaneous route and the specific antibody level was determined by ELISA. Results The molecular mass of the expressed recombinant antigen was about 36 000; the expressed product was about 25% in total bacterial proteins. The recombinant EAAg342 could assemble into virus-like particles(VLP) of 10~20 nm radiuses. It indicated that the fusion protein could have specific reaction with HAV and HEV positive sera by Western blotting. The geometric mean titers(GMT) of antiHEV IgG antibody induced by both different recombinant antigens were high. However the levels of anti-HAV IgG antibody induced by the two recombinant antigens were lower than the one induced by the traditional HAV vaccines. Conclusion The recombinant antigen of the hepatitis A and hepatitis E viruses could be expressed in high yield by procaryotic expression system. The two different fusion proteins both have good antigenicity and immunogenicity respectively. The data provided experimental confirmation for development of bivalent vaccine and serologically diagnostic kit for HAV and HEV.

Key words: hepatitis A virus(HAV), hepatitis E virus(HEV), recombinant antigen, procaryotic expression, immunogenicity