Hypervariable region 1 and N-linked glycans of hepatitis C regulate virion neutralization by modulating envelope...

Area of Science:

• Virology
• Immunology
• Structural Biology

Background:

• Hepatitis C virus (HCV) causes millions of new infections yearly, necessitating a vaccine.
• HCV's E2 glycoprotein, with its hypervariable region 1 (HVR1) and N-linked glycans, presents a major hurdle for vaccine development by evading neutralizing antibodies (NAbs).

Purpose of the Study:

• To investigate the roles of E2 glycans and HVR1 in HCV neutralization sensitivity and viral entry.
• To elucidate the structural dynamics of the HCV envelope and their impact on immune evasion.

Main Methods:

• Analyzing the effects of individual E2 glycan removal on neutralization across different HCV genotypes (1a, 2a, 3a).
• Conducting temperature-dependent neutralization assays to assess viral envelope conformations.
• Correlating neutralization sensitivity with scavenger receptor BI (SR-BI) dependency during viral entry.

Main Results:

• Glycan-mediated effects on neutralization were dependent on HVR1, suggesting indirect epitope protection rather than direct shielding.
• Both HVR1 and certain glycans stabilize a closed, neutralization-resistant viral envelope conformation.
• HVR1 removal destabilized this conformation, increasing sensitivity to neutralization.
• Neutralization sensitivity strongly correlated with SR-BI dependency for viral entry.

Conclusions:

• HVR1 and glycans dynamically regulate HCV neutralization by modulating the equilibrium between open and closed envelope conformations.
• This conformational regulation is linked to SR-BI dependency, indicating a role for SR-BI in viral entry transitions.
• Understanding these structural dynamics is critical for developing effective HCV vaccines and may offer insights into other viral immune evasion strategies.