Hepatitis C virus attachment mediated by apolipoprotein E binding to cell surface heparan sulfate

Area of Science:

• Virology
• Cell Biology
• Biochemistry

Background:

• Viruses utilize envelope proteins for cell attachment, initiating infection.
• Hepatitis C virus (HCV) infection involves complex interactions with host cell receptors.

Purpose of the Study:

• To investigate the role of cellular apolipoprotein E (apoE) in Hepatitis C virus (HCV) attachment to host cells.
• To elucidate the mechanism by which apoE mediates HCV attachment.

Main Methods:

• Utilized apoE-specific monoclonal antibodies to block HCV attachment.
• Employed small interfering RNA (siRNA) to knock down known HCV receptor/coreceptor molecules.
• Investigated the effect of heparinase treatment on HCV attachment.
• Performed site-directed mutagenesis on apoE to assess the role of its receptor-binding region.
• Conducted in vitro heparin pulldown assays to evaluate apoE's heparin-binding activity.
• Tested a synthetic peptide derived from the apoE receptor-binding region for inhibitory effects.

Main Results:

• An apoE-specific antibody blocked HCV attachment to hepatoma cells and primary human hepatocytes.
• Knockdown of known HCV receptors (CD81, claudin-1, LDLr, occludin, SR-BI) did not affect attachment but inhibited infection.
• Heparan sulfate removal from cell surfaces blocked HCV attachment.
• Mutations in apoE's receptor-binding region reduced apoE-mediated HCV infection and heparin-binding activity.
• A synthetic peptide from the apoE receptor-binding region inhibited HCV attachment.

Conclusions:

• Hepatitis C virus (HCV) utilizes cellular apolipoprotein E (apoE) for attachment to host cells.
• ApoE mediates HCV attachment through specific interactions with cell surface heparan sulfate.
• This interaction is a critical, early step in the HCV infection process, preceding entry mediated by other receptors.