Hepatitis δ virus attaches to human hepatocytes via human liver endonexin II, a specific HBsAg binding protein

SUMMARY. Recently we identified human liver endonexin II (EII) as a specific hepatitis B surface antigen (HBsAg) binding protein. To investigate whether EII is also able to interact with the HBsAg envelope of the hepatitis δ virus (HδV). immunoprecipitation experiments were performed. HδV particles could be co-precipitated by polyclonal rabbit anti-EII, but not by rabbit anti-glutathiontransferase (GSTφ) antibodies from an HδV-enriched fraction containing EII or GSTφ. These findings suggest that HδV particles were co-precipitated by anti-EII as a consequence of the binding between HBsAg present in the HδV envelope and EII. Furthermore, binding of HδV particles to human hepatocytes could be inhibited by incubation of the liver cells with rabbit anti-EII IgG or the HδV particles with anti-idiotypic (anti-HBsAg) antibodies, developed spontaneously in rabbits immunized with EII. These findings support the assumption that small HBsAg present in the HδV envelope is important for the attachment to the hepatocytes and that EII plays an important role in this process.