Structure-Based Design of Hepatitis C Virus E2 Glycoprotein Improves Serum Binding and Cross-Neutralization

Area of Science:

• Virology
• Immunology
• Vaccine Development

Background:

• Hepatitis C virus (HCV) infection affects approximately 1% of the global population, with no current vaccine available.
• HCV's high variability and immune escape mechanisms necessitate a vaccine that induces broadly neutralizing antibodies (bNAbs) targeting conserved epitopes.
• The HCV E2 envelope glycoprotein is a key target for vaccine design due to its role in viral entry and antibody recognition.

Purpose of the Study:

• To design novel immunogens based on the HCV E2 glycoprotein structure to elicit broadly neutralizing antibodies (bNAbs).
• To engineer specific antigenic sites on E2 to stabilize conformation, mask immunodominant regions, and enhance the induction of protective immune responses.
• To evaluate the immunogenicity and neutralization capacity of designed E2 immunogens *in vitro* and *in vivo*.

Main Methods:

• Structure-based design of HCV E2 envelope glycoprotein, including point mutations and redesigns of immunogenic regions.
• Experimental characterization of designed immunogens for binding to human monoclonal antibodies (HMAbs) and the CD81 coreceptor.
• Assessment of immunogenicity in mice and evaluation of polyclonal immune serum binding to HCV pseudoparticles and neutralization of resistant viral isolates.

Main Results:

• Designed E2 immunogens demonstrated altered antigenic profiles and preserved key epitope structures.
• One E2 design, tested with and without the hypervariable region 1, showed improved polyclonal immune serum binding to HCV pseudoparticles.
• This optimized E2 design led to enhanced neutralization of antibody-resistant HCV isolates, demonstrating improved cross-neutralization.

Conclusions:

• Structure-based antigen optimization of HCV envelope glycoproteins is a viable strategy for developing effective HCV vaccines.
• Rational engineering of E2 antigenicity can overcome challenges posed by HCV variability and immune escape.
• These findings provide a proof of concept for developing a next-generation HCV vaccine targeting conserved epitopes through rational design.