Hepatitis B causes
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Hepatitis B |
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Hepatitis B causes On the Web |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
Overview
The hepatitis B virus is an hepadnavirus with a DNA genome. The viral particle consists of an outer lipid envelope and an 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.
Taxonomy
Viruses; Retro-transcribing viruses; Hepadnaviridae; Orthohepadnavirus
Biology
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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).
Hepatocytes infected in vivo by hepadnaviruses produce an excess of noninfectious viral lipoprotein particles.
Structure
Hepatitis B virus (HBV) is a member of the Hepadnavirus family.[3]
The viral particle (virion) consists of an outer lipid envelope and an icosahedral nucleocapsid core composed of protein. The nucleocapsid encloses the viral DNA and a DNA polymerase, that has reverse transcriptase activity.[4]
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.[5]
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.[6]
Tropism
Hepatitis B virus shows tropism for hepatocytes.[6]
Natural Reservoir
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.[7]
References
- ↑ "http://www.who.int/en/". External link in
|title=(help) - ↑ "http://commons.wikimedia.org/wiki/File:HBV_Genome.svg". External link in
|title=(help) - ↑ Zuckerman AJ (1996). "Hepatitis Viruses". In Baron S; et al. Baron's Medical Microbiology (4th ed.). University of Texas Medical Branch. ISBN 0-9631172-1-1.
- ↑ Locarnini S (2004). "Molecular virology of hepatitis B virus". Seminars in Liver Disease. 24 Suppl 1: 3–10. doi:10.1055/s-2004-828672. PMID 15192795. Retrieved 2012-02-08.
- ↑ Howard CR (1986). "The biology of hepadnaviruses". The Journal of General Virology. 67 ( Pt 7): 1215–35. PMID 3014045. Retrieved 2012-02-08. Unknown parameter
|month=ignored (help) - ↑ 6.0 6.1 "Hepatitis B" (PDF).
- ↑ "Hepatitis B".
