Preparation and Immunogenicity of a Pichia pastoris-derived Hepatitis B Vaccine Containing PreS1, PreS2 and S Epitopes

Abstract:

The preparation process and immunogenicity of a novel hepatitis B vaccine containing preS1, preS2 and S epitopes were investigated in this study. APichia pastoris stain GS115-SS1S2 harbouring two chimeric HBsAg gene constructs, SS1 and SS2 was cultivated by high-density fermentation. 300～600mg/L of the expression level was achieved through 48～72h methanol induction. SS1S2 antigen was extracted and purified by silica adsorption, HIC and SEC to 99% purity from the harvested cells. 82mg purified antigen could be achieved from one liter of fermentation culture. The immunogenicity of the purified antigen was evaluated in NIH mice. Three groups of female NIH mice, 14～16g in weight, were injected once intraperitoneally with 2.5, 0.625, 0.156μg of each of the two vaccines: SS1S2 or a commercially available S vaccine. Part of the mice were bled in 30 days after injection to compare the ED₅₀ of the two vaccines. For the SS1S2 vaccine, the ED₅₀ is 0.46, 0.29 and 0.84μg respectively for the preS1, preS2 and S antigens. For the S vaccine, the ED₅₀ is 0.99μg for the S antigen. Another part of the mice were bleed in 7 or 14 days to detect preS1, preS2 and S antibodies. Higher ratios of mice were seroconverted for preS1 and preS2 antibodies as compared to the S antibody in these two time points. These results suggest that the SS1S2 vaccine may be more immunogenic than the conventional S vaccines.