Many parts of the life cycle of hepatitis B virus (HBV)
infection of hepatocytes have been unravelled, but the attachment and entry process leading to
infection is largely unknown. Using primary Tupaia hepatocyte cultures as an in vitro
infection system, we determined that HBV uses cell-surface
heparan sulfate proteoglycans as low-affinity receptor, because HBV
infection was inhibited by
heparin (IC50: 5 microg ml(-1)) or other higher-sulfated
polymers, but not by lower-sulfated
glycosaminoglycans, such as
chondroitin sulfate. Pretreatment of primary hepatocytes with
heparinase decreased viral binding and inhibited HBV
infection completely. Interestingly, after preS1-dependent viral binding at 16 degrees C to the cell surface, subsequent
infection could still be inhibited by HBV preS1-lipopeptides, but not by
heparin any more, suggesting a shift of the virus to a high-affinity receptor. In summary, we suggest following multistep attachment process: in vivo, HBV is initially trapped within the liver in the space of Dissé by
heparan sulfate proteoglycans. Thereafter, HBV binds via its preS1 attachment site and the N-terminal
myristic acid to a yet unknown, high-affinity receptor that confers uptake in a yet unknown compartment.