Impacts of HBsAg P24 conjugating extent on the antigenicity of the recombinant yeast expressed HBsAg
Objective To identify the impact of the HBsAg P24 unit conjugating extent on the antigeni- city of the recombinant yeast expressed HBsAg. Methods Three lots of purified HBsAg derived from recombinant yeast were treated with or without thiocyanate to prepare non-transformed, semi-transformed and transformed HBsAg, the P24 unit is theoretically loose-conjugated, semi-tight-conjugated and tight-conjugated. The tight-conjugation of polypeptide P24 unit for HBsAg was detected by HPLC. The BALB/c mice NK activities and HBsAg specific spleen lymphocytes proliferation immunized with the loose-conjugated and tight-conjugated HBsAg were tested. Results The average tight-conjugated P24 percentages of the three lots loose-conjugated, semi-tight-conjugated and tight-conjugated HBsAg are 23.00%-32.00%, 38.43%-50.98% and 39.65%-52.76%, respectively. The extent of tight-conjugated P24 semi-transformed HBsAg is similar to transformed ones. The NK activities induced by tight-conjugated HBsAg were higher than that induced by loose-conjugated antigen, the HBsAg specific spleen lymphocytes proliferation induced by loose-conjugated antigen was higher than that of tight-conjugated antigen in 4 weeks. All loose-conjugated, semi-tight-conjugated and tight-conjugated HBsAg effectively induced humoral immunoresponse. Although all vaccines showed effective immunogenicity, the semi-tight-conjugate vaccines are significantly more effective than that of loose-conjugated (P0.05). Both the median effective dose (ED_ 50 ) and in vitro relative potencies (RP) of the loose-conjugated and the semi-tight-conjugated trial hepatitis B vaccines meet the requirement of the recombinant yeast derived hepatitis B vaccine. Conclusion Various P24 unit conjugated degree HBsAg maintains antigenicity. The tight-conjugated HBsAg could induce stronger NK activities than loosed HBsAg. The semi-transform treatment may improve the immunogenicity of HBsAg.