Morphological characterization and fusion properties of triglyceride-rich lipoproteins obtained from cells transduced with hepatitis C virus glycoproteins

J Biol Chem. 2010 Aug 13;285(33):25802-11. doi: 10.1074/jbc.M110.131664. Epub 2010 Jun 15.

Abstract

The density of hepatitis C virus (HCV) particles circulating in the blood of chronically infected patients and of cell-culture produced HCV is heterogeneous. Specific infectivity and fusion of low density particles are higher than those of high density particles. We recently characterized hybrid particles produced by Caco-2 colon or Huh-7.5 liver cells transduced with HCV E1 and E2 envelope glycoproteins. Caco-2-derived particles, called empty lipo-viral particles (eLVP), are composed of triglyceride-rich lipoproteins positive for apolipoproteins B (i.e. apoB100 and apoB48) and contain HCV E1 and E2. Here we aimed at characterizing the morphology and in vitro fusion properties of eLVP using electron microscopy and fluorescence spectroscopy. They displayed the aspect of beta-lipoproteins, and immunogold labeling confirmed the presence of apoB and HCV E1 and E2 at their surface. These particles are able to fuse with lipid bilayers (liposomes) in a fusion process leading to the coalescence of internal contents of triglyceride-rich lipoproteins particles and liposomes. Fusion was pH-dependent and could be inhibited by either Z-fFG, a peptide known to inhibit viral fusion, or by monoclonal antibodies directed against HCV E2 or the apolipoprotein moiety of the hybrid particle. Interestingly, particles derived from Huh-7.5 cells failed to display equivalent efficient fusion. Optimal fusion activity is, thus, observed when HCV envelope proteins are associated to apoB-positive hybrid particles. Our results, therefore, point to a crucial role of the E1 and E2 proteins in HCV fusion with a subtle interplay with the apolipoprotein part of eLVP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Caco-2 Cells
  • Cell Line, Tumor
  • Cryoelectron Microscopy
  • Hepacivirus / genetics*
  • Humans
  • Lipoproteins / metabolism*
  • Lipoproteins / ultrastructure
  • Microscopy, Electron
  • Transduction, Genetic
  • Triglycerides / metabolism*
  • Viral Fusion Proteins / genetics
  • Viral Fusion Proteins / metabolism*
  • Virion / metabolism
  • Virion / ultrastructure

Substances

  • Lipoproteins
  • Triglycerides
  • Viral Fusion Proteins
  • lipoprotein triglyceride