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Journal of Virology, March 1999, p. 2052-2057, Vol. 73, No. 3
Unité de Recherches
Hépatologiques U 49, Institut National de la Santé et de la
Recherche Médicale, Hôpital de Pontchaillou, 35033 Rennes Cedex, France
Received 24 July 1998/Accepted 20 November 1998
During the life cycle of hepatitis B virus (HBV), the large
envelope protein (L) plays a pivotal role. Indeed, this polypeptide is
essential for viral assembly and probably for the infection process. By
performing mutagenesis experiments, we have previously excluded a
putative involvement of the pre-S2 domain of the L protein in viral
infectivity. In the present study, we have evaluated the role of the
pre-S1 region in HBV infection. For this purpose, 21 mutants of the L
protein were created. The entire pre-S1 domain was covered by
contiguous deletions of 5 amino acids. First, after transfection into
HepG2 cells, the efficient expression of both glycosylated and
unglycosylated L mutant proteins was verified. The secretion rate of
envelope proteins was modified positively or negatively by deletions,
indicating that the pre-S1 domain contains several regulating sequences
able to influence the surface protein secretion. The ability of mutant
proteins to support the production of virions was then studied. Only
the four C-terminal deletions, covering the 17 amino acids suspected to
interact with the cytoplasmic nucleocapsids, inhibited virion release.
Finally, the presence of the modified pre-S1 domain at the external
side of all secreted virions was confirmed, and their infectivity was assayed on normal human hepatocytes in primary culture. Only a short
sequence including amino acids 78 to 87 tolerates internal deletions
without affecting viral infectivity. These results confirm the
involvement of the L protein in the infection step and demonstrate that
the sequence between amino acids 3 and 77 is involved in this process.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Infection Process of the Hepatitis B Virus Depends
on the Presence of a Defined Sequence in the Pre-S1 Domain
*
Corresponding author. Mailing address: Unité de
Recherches Hépatologiques, INSERM U49, Hôpital de
Pontchaillou, 35033 Rennes Cedex, France. Phone: (33) 02 99 54 37 37. Fax: (33) 02 99 54 01 37. E-mail:
philippe.gripon{at}rennes.inserm.fr.
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