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Hepadnaviridae
Hepatitis B virus 01.jpg
TEM micrograph showing hepatitis B virions
Virus classification
Group: Group VII (dsDNA-RT)
Order: Unassigned
Family: Hepadnaviridae
Genera

Hepadnaviruses are a family of enveloped, double-stranded viruses which can cause liver infections in animals—including humans. Its most well-known member is the Hepatitis B virus.

There are two recognized genera:

The name of the family comes from : hepa(for HEPAtic)-DNA-virus.

Virology[edit]

Genome[edit]

Hepadnaviruses have very small genomes of partially double-stranded, partially single stranded circular DNA. The genome consists of two uneven strands of DNA. One has a negative-sense orientation, and the other, shorter, strand has a positive-sense orientation.

As it is a group 7 virus, replication involves an RNA intermediate. Three main open reading frames are encoded (ORFs) and the virus has four known genes which encode the core protein, the virus polymerase, surface antigens (preS1, preS2, and S) and the X protein. The X protein is thought to be non-structural; however, its function and significance are poorly understood.

Replication[edit]

Hepadnaviruses replicate through an RNA intermediate (which they transcribe back into cDNA using reverse transcriptase). The reverse transcriptase becomes covalently linked to a short 3- or 4-nucleotide primer.[1] Most hepadnaviruses will only replicate in specific hosts, and this makes experiments using in vitro methods very difficult.

The virus binds to specific receptors on cells and the core particle enters the cell cytoplasm. This is then translocated to the nucleus, where the partially double stranded DNA is 'repaired' by the cell to form a complete circle of DNA. It then undergoes transcription by the host cell RNA polymerase and the transcript is translated by host cell ribosomes. New virus particles are formed, which acquire lipid from the endoplasmic reticulum of the host cell, and the genome is packaged within these particles, which then bud off from the cell.

Hepadnavirus-infected cells translate the protein known as the virus surface antigen many times until there is too much protein to coat the virions formed. These proteins then aggregate to form rod shapes, and it is this antigen, known as hepatitis B surface antigen, which is released from the cell and which leads to a very strong immune response from the host.

Evolution[edit]

Based on the presence of viral genomes in bird DNA it appears that the Hepatoviruses evolved >82 million years ago.[2] Birds may be the original hosts of the Hepatovirus with mammals becoming infected after a bird -> mammal host shift.

References[edit]

  1. ^ A Novel cis-Acting Element Facilitates Minus-Strand DNA Synthesis during Reverse Transcription of the Hepatitis B Virus Genome by Myeong-Kyun Shin, Jehan Lee and Wang-Shick Ryu in Journal of Virology (2004) volume 78, pages 6252–6262.
  2. ^ Suh A, Brosius J, Schmitz J, Kriegs JO (2013) The genome of a Mesozoic paleovirus reveals the evolution of hepatitis B viruses. Nat Commun 4:1791. doi: 10.1038/ncomms2798

External links[edit]


Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Hepadnaviridae — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.
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Prezi® Presentation: hepatitis b by Maria Zuñiga

This video is a Prezi®, converted by PreziTube® Create your own video from your Prezi® at PreziTube click: http://goo.gl/h3aa0V Title: hepatitis b Author: Ma...

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Prezi® Presentation: Hepatitis B by macarena naranjo retamal

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Wed, 15 Oct 2014 12:30:00 -0700

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Tue, 05 Jul 2011 03:43:34 -0700

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AllAfrica.com
Fri, 27 Jul 2012 22:48:45 -0700

This is a DNA virus that belongs to the genus Orthohepadnavirus of the Hepadnaviridae family. There are two types of hepatitis B-acute (recently acquired) and chronic (life-long). For most people with acute hepatitis B, symptoms gradually get better ...

Meteo Web

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Sat, 14 Jun 2014 06:31:41 -0700

EPATITE B COP L'epatite B è una patologia infettiva a carico del fegato, causata da un virus appartenente alla famiglia Hepadnaviridae, l'HBV (Hepatitis B Virus, virus dell'epatite B). TRASMISSIONE: Esso può essere trasmesso per via parentale (cioè ...

El Día

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Sat, 16 Aug 2014 18:22:36 -0700

El virus pertenece a la familia Hepadnaviridae y fue descubierto en 1963 por el premio Nobel Baruch Blumberg. Provoca una infección crónica en el hígado que puede derivar en una cirrosis o en cáncer. El virus se contagia a través de contacto con la ...

24con.com

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Thu, 14 Aug 2014 06:41:15 -0700

El virus pertenece a la familia Hepadnaviridae y fue descubierto en 1963 por el premio Nobel Baruch Blumberg. Provoca una infección crónica en el hígado que puede derivar en una cirrosis o en cáncer. El virus se contagia a través de contacto con la ...
 
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Wed, 12 Feb 2014 07:40:48 -0800

12/02/2014 | Puerto G. San Martín| Se realizaron el pasado martes campañas de vacunación contra la Hepatitis B en al localidad de Puerto San Martín, y se continuará realizando durante todo el año.
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