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| __NOTOC__
| | #REDIRECT[[Hepatitis B virus]] |
| {{Hepatitis B}}
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| {{CMG}}; {{AE}} {{JS}}
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| ==Overview==
| | [[Category:Emergency mdicine]] |
| The [[hepatitis B virus]] is an [[hepadnavirus]] with a DNA [[genome]]. The viral particle consists of an outer [[lipid]] envelope and an [[icosahedron|icosahedral]] [[nucleocapsid]] core composed of [[protein]]. The nucleocapsid encloses the viral DNA and a DNA [[polymerase]] that has [[reverse transcriptase]] activity. It shows [[tropism]] for [[hepatocytes]] and humans are its only [[natural reservoir]].
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| ==Taxonomy==
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| [[Viruses]]; Retro-transcribing viruses; [[Hepadnaviridae]]; Orthohepadnavirus
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| ==Biology==
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| {| style="float: right;"
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| | [[File:Hepatitis B virus.png|200px|thumb|none|Hepatitis B virions <SMALL>Courtesy: ''[http://www.who.int/en/ World Health Organization]''<ref>{{Cite web | title = http://www.who.int/en/ | url = http://www.who.int/en/}}</ref></SMALL>]]
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| | [[File:HBV Genome.png|200px|thumb|none|The genome organisation of HBV. The genes overlap. <SMALL>Courtesy: ''[Wikimedia Commons]''<ref>{{Cite web | title = http://commons.wikimedia.org/wiki/File:HBV_Genome.svg | url = http://commons.wikimedia.org/wiki/File:HBV_Genome.svg}}</ref></SMALL>]]
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| The [[hepatitis B virus]], an [[hepadnavirus]], is a 42 nm partially double stranded [[DNA]] virus, composed of a 27 nm nucleocapsid core (HBcAg), surrounded by an outer [[lipoprotein]] coat (also called envelope) containing the surface antigen ([[HBsAg]]).
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| [[Hepatocytes]] infected in vivo by [[hepadnaviruses]] produce an excess of noninfectious viral [[lipoprotein]] particles.
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| ==Structure==
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| [[Hepatitis B virus]] ([[HBV]]) is a member of the [[Hepadnaviridae|Hepadnavirus family]].<ref name=Baron>{{Cite book |author=Zuckerman AJ |chapter=Hepatitis Viruses |title=Baron's Medical Microbiology |editor=Baron S, ''et al'' |edition=4th |publisher=University of Texas Medical Branch |year=1996|url=http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.section.3738|isbn=0-9631172-1-1 }}</ref>
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| The viral particle ([[virion]]) consists of an outer [[lipid]] envelope and an [[icosahedron|icosahedral]] [[nucleocapsid]] core composed of [[protein]]. The nucleocapsid encloses the viral DNA and a DNA [[polymerase]], that has [[reverse transcriptase]] activity.<ref name="pmid15192795">{{cite journal |author=Locarnini S |title=Molecular virology of hepatitis B virus |journal=[[Seminars in Liver Disease]] |volume=24 Suppl 1 |issue= |pages=3–10 |year=2004 |pmid=15192795 |doi=10.1055/s-2004-828672 |url=http://www.thieme-connect.com/DOI/DOI?10.1055/s-2004-828672 |accessdate=2012-02-08}}</ref>
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| The outer envelope contains embedded proteins that are involved in viral binding of, and entry into, susceptible cells. The [[virus]] is one of the smallest enveloped animal viruses, with a [[virion]] diameter of 42nm, but pleomorphic forms exist, including filamentous and spherical bodies lacking a core. These particles are not infectious and are composed of the lipid and protein that form part of the surface of the virion, which is called the surface antigen ([[HBsAg]]), and is produced in excess during the life cycle of the virus.<ref name="pmid3014045">{{cite journal |author=Howard CR |title=The biology of hepadnaviruses |journal=[[The Journal of General Virology]] |volume=67 ( Pt 7) |issue= |pages=1215–35 |year=1986 |month=July |pmid=3014045 |doi= |url=http://vir.sgmjournals.org/cgi/pmidlookup?view=long&pmid=3014045 |accessdate=2012-02-08}}</ref>
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| The [[protein]] of the [[virion]] coat is termed "surface antigen" or [[HBsAg]]. It is sometimes extended as a tubular tail on one side of the virus particle. The surface antigen is generally produced in vast excess, and is found in the blood of infected individuals in the form of filamentous and spherical particles. Filamentous particles are identical to the virion "tails" - they vary in length and have a mean diameter of about 22nm. They sometimes display regular, non-helical transverse striations.<ref name=WHO>{{cite web | title = Hepatitis B | url = http://www.who.int/csr/disease/hepatitis/HepatitisB_whocdscsrlyo2002_2.pdf }}</ref>
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| ==Tropism==
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| [[Hepatitis B virus]] shows [[tropism]] for [[hepatocytes]].<ref name=WHO>{{cite web | title = Hepatitis B | url = http://www.who.int/csr/disease/hepatitis/HepatitisB_whocdscsrlyo2002_2.pdf }}</ref>
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| ==Natural Reservoir==
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| The [[natural reservoir]] for [[hepatitis B virus]] is man. Closely related [[hepadnaviruses]] have been found in woodchucks and ducks, but they are not [[infectious]] for humans.<ref name=WHO1>{{cite web | title = Hepatitis B | url = http://www.who.int/csr/disease/hepatitis/whocdscsrlyo20022/en/index3.html }}</ref>
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| == References ==
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| {{Reflist|2}}
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| {{STD/STI}}
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| [[Category:Hepatitis|B]]
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| [[Category:Viruses]]
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| [[Category:Infectious disease]] | | [[Category:Infectious disease]] |
| | [[Category:Hepatology]] |
| [[Category:Gastroenterology]] | | [[Category:Gastroenterology]] |
| [[Category:Mature chapter]]
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| [[Category:Disease]]
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| {{WH}}
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| {{WS}}
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