Article first published online: 15 FEB 2013
Copyright © 2012 American Association for the Study of Liver Diseases
Volume 57, Issue 3, pages 985–994, March 2013
How to Cite
Sureau, C. and Salisse, J. (2013), A conformational heparan sulfate binding site essential to infectivity overlaps with the conserved hepatitis B virus A-determinant. Hepatology, 57: 985–994. doi: 10.1002/hep.26125
Potential conflict of interest: Nothing to report.
Supported by Agence Nationale de la Recherche sur le Sida et les hepatitis virales and Centre National de la Recherche Scientifique.
- Issue published online: 28 FEB 2013
- Article first published online: 15 FEB 2013
- Accepted manuscript online: 13 NOV 2012 12:00AM EST
- Manuscript Accepted: 16 OCT 2012
- Manuscript Received: 16 JUL 2012
Two determinants of infectivity have been identified in the hepatitis B virus (HBV) envelope proteins: a pre-S1 receptor-binding site and an uncharacterized determinant in the antigenic loop (AGL), which is structurally related to the antigenic a-determinant. Infection would proceed through virus attachment to cell surface heparan sulfate (HS) proteoglycans (HSPGs) before pre-S1 engages a specific receptor for uptake. Using heparin binding and in vitro infection assays with hepatitis D virus as a surrogate for HBV, we established that HS binding is mediated by the AGL. Electrostatic interaction was shown to depend upon AGL residues R122 and K141, because their substitution with alanine modified the virus net-charge and prevented binding to heparin, attachment to hepatocytes, and infection. In addition to R122 and K141, the HS binding determinant was mapped to cysteines and prolines, which also define the conformational a-determinant. The importance of AGL conformation was further demonstrated by the concomitant loss of a-determinant and heparin binding upon treatment of viral particles with membrane-impermeable reducing agent. Furthermore, envelope proteins extracted from the viral membrane with a nonionic detergent were shown to conserve the a-determinant but to lose heparin affinity/avidity. Conclusion: Our findings support a model in which attachment of HBV to HSPGs is mediated by the AGL HS binding site, including only two positively charged residues (R122 and K141) positioned precisely in a three-dimensional AGL structure that is stabilized by disulfide bonds. HBV envelope proteins would individually bind to HS with low affinity, but upon their clustering in the viral membrane, they would reach sufficient avidity for a stable interaction between virus and cell surface HSPGs. Our data provide new insight into the HBV entry pathway, including the opportunity to design antivirals directed to the AGL-HS interaction. (HEPATOLOGY 2013)