The Role of the HBV Envelope Proteins in the HDV Replication Cycle

Laboratoire de Virologie Mol├ęculaire, Institut National de la Transfusion Sanguine,

6 Rue Alexandre Cabanel, 75739 Paris, France

[email protected]

1 Introduction 114

1.1 The Virion Structure 114

1.2 The Helper HBV 118

2 The Interaction Between the HDV RNP

and the HBV Envelope Proteins 120

3 The S-HBsAg Protein and the Assembly of HDV Particles 121

4 The L-HBsAg Protein and the Infectivity of the HDV Particles 124

5 The Effect of HDV Infection on the HBV Life Cycle 125

6 Conclusion 126

References 127

Abstract The hepatitis delta virus (HDV) is a subviral agent that utilizes the envelope proteins of the hepatitis B virus (HBV) for propagation. When introduced into permissive cells, the HDV RNA genome replicates and associates with multiple copies of the HDV-encoded proteins to assemble a ribonucleoprotein (RNP) complex. The mechanism necessary to export the RNP from the cell is provided by the HBV envelope proteins, which have the capacity to assemble lipoprotein vesicles that bud into the lumen of a pre-Golgi compartment before being secreted. In addition to allowing the release of the HDV RNP, the HBV envelope proteins also provide a means for its targeting to an uninfected cell, thereby ensuring the spread of HDV. This chapter covers the molecular aspects of the HBV envelope protein functions in the HDV replication cycle, in particular the activity of the small envelope protein in RNP export and the function of the large envelope protein at viral entry.

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