Hepatitis Delta Virus

John M Taylor, Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA

Published online: November 2010

DOI: 10.1002/9780470015902.a0001029.pub3

Several viruses are important causes of acute and chronic infections of the human liver. Hepatitis delta virus (HDV) is a most unusual agent that is found only in association with Hepatitis B virus (HBV). HBV is a helper virus for HDV and provides the envelope proteins needed for the assembly of new HDV particles. Otherwise the replication of the HDV RNA (ribonucleic acid) genome is independent of HBV. HDV encodes only one protein, the delta antigen, a small basic RNA-binding protein, which is essential for genome replication. In the animal world, HDV is unique to infections of humans. However, HDV shows some intriguing similarities to plant viroids, which have RNA genomes even smaller than HDV, and encode no known proteins and have no helper viruses.

Key Concepts:

  • HDV uses HBV as a helper virus to achieve assembly of new virus particles.
  • HDV has a small single-stranded circular RNA genome.
  • During genome replication there arises the antigenome, an exact complement of the genome.
  • The HDV genome and antigenome are transcribed by redirection of a host RNA polymerase that normally acts on DNA templates.
  • Antigenomic HDV RNA sequences encode one small basic protein that is essential for genome replication
  • Site-specific RNA-editing on antigenomic RNA leads to the translation of a large delta antigen species, one that supports assembly via HBV envelope proteins.
  • The HDV RNA genome and its mode of replication show intriguing similarities to the plant viroid RNAs.

Keywords: hepatitis; delta; virus; interferon; ribozyme; RNA editing; transcription

Figure 1. The three RNAs detected during the replication of HDV. (a) The first is the 1679-nt single-stranded circular RNA found within virions, and thus defined as the genome. (b) The second is an exact complement of the genome, defined as the antigenome, and together with the genome it is found in the nuclei of infected cells. (c) A third RNA, the least abundant, cytoplasmic, approximately 800 nt in length, 5¢-capped and 3¢-polyadenylated, is the mRNA for the translation of the delta protein. Note that both the genome and antigenome are drawn as having an unbranched rod-like structure, involving extensive intramolecular base pairing. Also, each contains a domain that will act as a self-cleaving ribozyme. Adapted from Taylor (2005), with permission from Wiley-Blackwell.
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 References
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 Further Reading
    book Casey JL (2006) "Hepatitis delta virus". In: Current Topics in Microbiology and Immunology, vol. 207. Berlin, Germany: Springer.
    book Handa H and Yamaguchi Y (2006) Hepatitis Delta Virus, Landes Bioscience. Georgetown, TX: Landes Bioscience and Springer Science+Business Media, Inc.

Related Sub-Topics:

Virus Diseases | Viruses Infecting Humans | RNA Viruses
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Article Title: Hepatitis Delta Virus
 
How to Cite close
Taylor, John M(Nov 2010) Hepatitis Delta Virus. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001029.pub3]