Summary auto-generated
This study describes a novel genetic engineering strategy to create mosaic hepatitis B virus (HBV) core particles capable of displaying larger foreign protein segments. Researchers used a stop codon-mediated readthrough mechanism in Escherichia coli to achieve simultaneous synthesis of truncated HBV core antigen (HBcAg∆) and fusion proteins containing hantavirus nucleocapsid protein sequences. By inserting a linker with a translational stop codon between HBcAg∆ and the foreign protein gene, they exploited suppressor tRNA in specially engineered bacterial strains to allow controlled readthrough translation. The resulting mosaic particles, containing both unmodified core proteins and fusion proteins, self-assembled into structures ~33-36 nm in diameter that retained immunological properties of both HBV and hantavirus antigens. Electron microscopy and immunological assays confirmed surface exposure of the foreign determinants. This strategy overcomes previous size limitations (typically ~90 amino acids) that restricted foreign sequence insertion into core particles, potentially enabling construction of multivalent vaccines presenting multiple epitopes on a single carrier platform.
Key findings
- A stop codon readthrough mechanism allows co-expression of truncated HBV core antigen and fusion proteins containing foreign sequences in suppressor bacterial strains.
- Mosaic particles self-assemble from mixtures of unmodified core proteins and fusion proteins, maintaining the particle structure and size (~33-36 nm diameter).
- The strategy enables insertion of larger foreign protein segments (≥114 amino acids of hantavirus nucleocapsid protein) while preserving particle formation and antigenicity.
- Both HBV and hantavirus antigenic determinants are displayed on the particle surface, as demonstrated by immunoelectron microscopy and ELISA.
- This approach overcomes previous limitations on foreign sequence insertion capacity, facilitating development of multivalent vaccines with multiple epitopes.
This summary was generated automatically from the article PDF and is not part of the original publication. Refer to the PDF for the authoritative text.
Abstract
Because of its particular immunological properties, the core protein of hepatitis B virus (HBcAg) has become one of the favoured 'virus-like particles' for use as a carrier of foreign epitopes. A new strategy to construct core particles presenting extended foreign protein segments was established based on the introduction of a linker containing a translational stop codon between sequences encoding a C-terminally truncated HBcAg (HBcAg delta) and a foreign protein sequence. Expression in an Escherichia coli suppressor strain allowed the simultaneous synthesis of both HBcAg delta and a read-through fusion protein containing a part of the hantavirus nucleocapsid protein. After purification, the presence of core-like mosaic particles with HBc and hantavirus antigenicity was demonstrated by electron microscopy and immunological tests. This strategy of partial stop codon suppression should improve the use of HBcAg as a carrier of foreign epitopes by allowing insertion of long foreign sequences into particle-forming proteins. The resulting mosaic particles should be of general interest for further vaccine developments.