Cryo-electron microscopy and three-dimensional reconstructions of hepatitis C virus particles

Area of Science:

• Virology
• Structural Biology
• Biophysics

Background:

• Hepatitis C virus (HCV) structural details remain elusive due to challenges in producing sufficient infectious virions for analysis.
• Lack of robust tissue culture systems hinders in-depth three-dimensional (3D) structural studies of HCV.

Purpose of the Study:

• To elucidate the 3D structure of HCV particles.
• To understand the assembly and maturation mechanisms of HCV.

Main Methods:

• Utilized negative-stain and cryo-electron microscopy (cryoEM) for structural analysis.
• Employed recombinantly expressed HCV-like particles (HCV-LPs) for 3D reconstructions.
• Investigated antibody binding to E1 glycoprotein to map epitope exposure.

Main Results:

• HCV virions and HCV-LPs exhibit uniform size and similar morphologic, biophysical, and antigenic features.
• 3D reconstruction revealed a multilayered HCV-LP architecture with a 'fishbone' outer layer.
• Identified E1 and E2 proteins forming a tetramer, analogous to flavivirus E homodimers, with exposed epitopes.

Conclusions:

• The first 3D structural analysis of HCV particles offers critical insights into viral assembly and maturation.
• The structural findings suggest a potential functional and morphological similarity between HCV E1/E2 proteins and flavivirus E glycoproteins.
• This study overcomes previous limitations by providing a detailed structural model of HCV.