Bacteria expressed hepatitis E virus capsid proteins maintain virion-like epitopes

Area of Science:

• Virology
• Immunology
• Vaccine Development

Background:

• The hepatitis E virus (HEV) ORF2 protein is the sole capsid protein.
• Previous studies defined domains for dimer formation (148 aa) and virus-like particle (VLP) assembly (239 aa).
• A neutralizing monoclonal antibody, mAb 8C11, recognizes epitopes on the HEV capsid.

Purpose of the Study:

• To characterize the self-assembled VLPs formed by the p239 protein.
• To evaluate the binding of mAb 8C11 to recombinant p239 VLPs and authentic HEV virions.
• To establish recombinant VLPs as a surrogate marker for HEV vaccine efficacy.

Main Methods:

• High-performance size-exclusion chromatography for VLP characterization.
• Binding assays using monoclonal antibody 8C11 against recombinant p239 VLPs and HEV virions.
• Titration curves to quantify HEV genome copies captured by mAb 8C11.

Main Results:

• Purified and refolded p239 proteins successfully formed VLPs.
• mAb 8C11 demonstrated binding to dimeric E2, p239 VLPs, and captured authentic HEV virions.
• mAb 8C11 binding served as a surrogate marker for virion-like epitopes and vaccine-induced neutralizing antibodies.

Conclusions:

• Escherichia coli-expressed pORF2 proteins, particularly p239, retain virion-like epitopes on their VLP surface.
• p239 VLPs exhibit epitopes recognized by neutralizing antibodies, validating their use in vaccine development.
• The findings support the efficacy of p239-based vaccines, such as Hecolin®, against HEV infection.