pBV220 vector

Hepatitis B core antigen (HBcAg) can self-assemble into virus-like particles (VLPs) when expressed in Escherichia coli. In this study, the researchers optimized the differences of the expression plasmid pBV220, including the ribosome binding site (RBS), spacer, promoter and origin of replication (ori), as well as hbc gene dosage, to enhance HBcAg transcription and translation in E. coli. The optimized construct with custom RBS6, 6 nt spacer, T7 promoter, and pUCori significantly increased the levels of HBc36GFP fusion protein up to 3.4-fold compared to the control. Thereafter, the hbc36gfp gene was replaced with different copies of the hbc gene and the effect of gene dosage on HBcAg expression was tested. The HBcAg-VLP yield obtained using the engineered strain with three copies of hbc was 842.1 ± 46.8 μg/mL, which was 2.2-fold higher than the control strain. Therefore, this study provides a simple and effective strategy to improve HBcAg expression in E. coli . Since HBcAg-VLPs are promising vectors for presenting exogenous antigenic epitopes, in vitro expression systems capable of producing high levels of HBcAg-VLPs can serve as promising tools for the development of novel HBV vaccines and drugs.

Figure 1. Reconstruction strategy of primary plasmid pBV220. (Zhang, Yi, et al. 2022)