Evaluating the Immunological Properties of Recombinant Hepatitis B Surface Antigen Using a Multitiered In Vivo and In Vitro Approach.

The immunological properties of recombinant hepatitis B surface antigen (rHBsAg), prepared using yeast (Saccharomyces cerevisiae [SC]) and Chinese hamster ovary (CHO) cells, were evaluated through in vitro and in vivo assays to support the efficacy of recombinant hepatitis B vaccines. In vitro, antigenicity was assessed by measuring the affinity of rHBsAg to anti-HB antibodies using surface plasmon resonance. In vivo, mice were intraperitoneally injected with 3 µg of simulated vaccines containing anti-HB antibodies absorbed onto aluminum hydroxide adjuvant. Humoral responses were evaluated by measuring serum anti-HB antibody titers and seroconversion rates on days 7, 14, 21, and 28. Cellular immune responses were assessed based on cytokine (Interferon-γ-IFN-γ) and (Tumor Necrosis Factor-α- TNF-α) production from splenic lymphocytes on day 28 postimmunization. A recombinant Huh-7-HBsAg cell line, developed to analyze cellular immune responses, was established through cytotoxicity and apoptosis assays. In vitro, the equilibrium dissociation constant (KD) of rHBsAg from CHO cells was significantly lower than that from yeast cells, indicating stronger antibody affinity. In vivo, rHBsAg-CHO induced faster and higher antibody titers compared with rHBsAg-SC. Cellular responses showed higher levels of TNF-α and IFN-γ for rHBsAg-CHO. In addition, the rHBsAg-CHO group exhibited higher late apoptosis rates in target cells. The rates induced in the rHBsAg-CHO and rHBsAg-SC groups were 25.0% and 19.2%, respectively. In conclusion, this study demonstrates that the immunological properties of rHBsAg vary based on the expression systems and provides nonclinical data supporting the evaluation of vaccine efficacy.