Description of Multicopy Recombinant Hepatitis B Surface Antigen: From Expression to Immune Analysis.

Hepatitis B virus (HBV) remains a significant global health challenge. Although antiviral treatments have improved, vaccines containing the Hepatitis B surface antigen (HBsAg) are still the most effective prevention method. Since 1998, HBV vaccines have been part of Turkiye's mandatory childhood vaccination program, with all vaccines currently imported. This study primarily aims to optimize recombinant HBsAg production in Pichia pastoris and evaluate its immunological comparability to the commercial HBV vaccine, thereby assessing its potential as a locally produced vaccine candidate. To achieve this, an eight-copy tandem construct of the HBsAg gene was created on the pPICZαA plasmid through an in vitro multimerization, and the production process of recombinant HBsAg was optimized. The presence of HBsAg in the supernatants following induction was confirmed, and the antigen was purified using various physical and biochemical methods. The highest yield of recombinant HBsAg was achieved with the eight-copy construct, following induction with 1% methanol and harvesting at 120 h, which was identified as the most productive time point. The antigenic properties of the produced HBsAg were compared with those of the commercially available vaccine, Engerix B™. Immunological testing using serum from anti-HBsAg positive individuals and immunized animals demonstrated that the recombinant rHBsAg exhibited similar antigenic characteristics to the commercial vaccine. The findings of this study indicate that the recombinant HBsAg exhibits immunological properties comparable to the imported vaccine and suggest that it may be a potential candidate for future vaccine development.