EXPRESSION OF A HUMAN CYTOMEGALOVIRUS GP58 ANTIGENIC DOMAIN FUSED TO THE HEPATITIS-B VIRUS NUCLEOCAPSID PROTEIN

Hepatitis B virus core antigen (HBcAg) has been used as a carrier for expression and presentation of a variety of heterologous viral epitope s in particulate form. The aim of this study was to produce hybrid ant igens comprising HBcAg and an immunogenic epitope of human cytomegalov irus (HCMV). A direct comparison was made of amino and carboxyl termin al fusions in order to investigate the influence of position of the fo reign epitope on hybrid core particle formation, antigenicity and immu nogenicity. HCMV DNA encoding a neutralising epitope of the surface gl ycoprotein gp58 was either inserted at the amino terminus or fused to the truncated carboxyl terminus of HBcAg and expressed in Escherichia coli. The carboxyl terminal fusion (HBc(3-144)-HCMV) was expressed at high levels and assembled into core like particles resembling native H BcAg. Protein with a similar fusion at the amino terminus (HCMV-HBc(1- 183)) could not be purified or characterised immunologically, although it formed core like particles. HBc(3-144)-HCMV displayed HBc antigeni city but HCMV antigenicity could not be detected by radioimmunoassay o r western blotting using anti-HCMV monoclonal antibody 7-17 or an anti -HCMV human polyclonal antiserum. Following immunisation of rabbits wi th HBc(3-144)-HCMV, a high titre of anti-HBc specific antibody was pro duced along with lower titres of HCMV/gp58 specific antibody.