The asialoglycoprotein receptor mediates hepatic binding and uptake of natural hepatitis B virus particles derived from viraemic carriers

Abstract

As a putative mechanism of hepatitis B virus (HBV) uptake into hepatocytes the interaction between HBV and the hepatic, human-derived asialoglycoprotein receptor (ASGPR) was investigated. Sera from patients with different variations of hepatitis B surface antigen-(HBsAg) positive chronic hepatitis, HBV particles isolated from HBV carriers with high-titre viraemia and commercial HBsAg served as sources of HBV. ASGPR was affinity-purified from human liver. HBV that had bound to isolated ASGPR was either detected by radioimmunoassay using solid-phase bound ASGPR or enzyme immunoassay with biotin-ASGPR bound to immobilized HBV. Furthermore, binding and uptake of purified, 125I-labelled HBV particles into human hepatoma cell lines (HepG2 and HuH7), which constitutively express functional ASGPR molecules, were compared to that of ASGPR-negative COS cells. As a result HBV was found to bind to purified human ASGPR in two different assays. Circulating virus particles from sera with high titre viraemia showed the highest attachment activity to ASGPR. HBV binding to purified ASGPR was saturable and inhibitable by an excess of D-galactose-bearing ligands, by EDTA and anti-receptor immunoglobulin. Lysis of particles by adding detergent abolished immunodetectable HBV binding to purified ASGPR. Commercial HBsAg did not adhere to solid phase-immobilized ASGPR. Monoclonal anti-preS1 antibody (MA18/7) but not anti-preS2 antibody (Q19/10) inhibited virus attachment. Purified and radiolabelled HBV particles showed binding to HepG2 and HuH7 cells but to much lesser degree to COS cells. Cellular binding of HBV was significantly inhibited by blocking of ASGPR function. Both ASGPR ligands and rabbit anti-ASGPR immunoglobulin but not non-immune rabbit serum inhibited uptake of radiolabelled HBV particles into HepG2 cells or HuH7 cells, respectively. This study suggests that HBV virions may enter human hepatocytes via ASGPR molecules by attachment of viral preS1-related envelope binding sites to this receptor.