Hepadnavirus infection requires interaction between the viral pre-S domain and a specific hepatocellular receptor.
To better define the molecules involved in the initial interaction between hepadnaviruses and hepatocytes, we performed binding and infectivity studies with the duck hepatitis B virus (DHBV) and cultured primary duck hepatocytes. In competition experiments with naturally occurring subviral particles containing DHBV surface proteins, these DNA-free particles were found to interfere with viral infectivity if used at sufficiently high concentrations. In direct binding saturation experiments with radiolabelled subviral particles, a biphasic titration curve containing a saturable component was obtained. Quantitative evaluation of both the binding and the infectivity data indicates that the duck hepatocyte presents about 10(4) high-affinity binding sites for viral and subviral particles. Binding to these productive sites may be preceded by reversible virus attachment to a large number of less specific, nonsaturable primary binding sites. To identify which of the viral envelope proteins is responsible for hepatocyte-specific attachment, subviral particles containing only one of the two DHBV surface proteins were produced in Saccharomyces cerevisiae. In infectivity competition experiments, only particles containing the large pre-S/S protein were found to markedly reduce the efficiency of DHBV infection, while particles containing the small S protein had only a minor effect. Similarly, physical binding of radiolabelled serum-derived subviral particles to primary duck hepatocytes was inhibited well only by the yeast-derived pre-S/S particles. Together, these results strongly support the notion that hepadnaviral infection is initiated by specific attachment of the pre-S domain of the large DHBV envelope protein to a limited number of hepatocellular binding sites.
Klingmüller
U
U
Zentrum für Molekulare Biologie Heidelberg, Universität Heidelberg, Germany.
Schaller
H
H
D000818:Animals; D001667:Binding, Competitive; D002478:Cells, Cultured; D004372:Ducks; D018347:Hepadnaviridae Infections / Q000378:metabolism*; D006514:Hepatitis B Surface Antigens / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D015611:Hepatitis B Virus, Duck / Q000378:metabolism* / Q000472:pathogenicity; D008099:Liver / Q000166:cytology / Q000378:metabolism* / Q000382:microbiology; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D011991:Receptors, Virus / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D014774:Virulence
D006514:Hepatitis B Surface Antigens; D011498:Protein Precursors; D011991:Receptors, Virus; D011994:Recombinant Proteins