Simian immunodeficiency virus
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Simian immunodeficiency viruses (SIV) are retroviruses that are found in over 40 African primates.
Viruses from two of these primate species, SIVsmm in Sooty Mangabeys and SIVcpz in chimpanzees, are believed to have crossed the species barrier into humans, resulting in HIV-2 and HIV-1, respectively. The most likely route of transmission of HIV-1 to humans involves contact with the blood of chimps that are often hunted for bushmeat in Africa.
Unlike HIV-1 and HIV-2 infections in humans, SIV infections in their natural hosts are widely believed to be non-pathogenic. Extensive studies in Sooty Mangabeys have established that SIVsmm infection does not cause any disease in these animals, despite high levels of circulating virus. However, if this virus is used to infect an Asian Rhesus Macaque, the animal will develop simian AIDS.
A recent study of SIVcpz in wild living chimpanzees suggest that infected chimpanzees experience an AIDS-like illness similar to HIV-1 infected humans.
SIV was first discovered in 1985, in captive Rhesus macaques suffering from SAIDS. This observation was made shortly after HIV-1 had been isolated as the cause of AIDS and led to the discovery of the HIV-2 strains in West Africa that same year. HIV-2 was more similar to the then-known SIV strains than to HIV-1, suggesting for the first time the simian origin of HIV. Further studies indicated that HIV-2 is derived from the SIVsm strain found in sooty mangabeys whereas HIV-1, the predominant virus found in humans, is derived from SIV strains infecting chimpanzees (SIVcpz).
The monkey SIV strains do not infect humans and HIV-1 does not infect monkeys. In 2004, this tropism was partly explained by different variants of the protein TRIM5α in humans and monkeys. This intracellular protein recognizes the capsid of various retroviruses and blocks their reproduction. Other proteins such as APOBEC3G/3F may be important in restricting cross-species transmission.
SHIV, a virus created for research purposes by combining parts of the HIV and SIV genomes also exists.
|author=Jonathan L. Heeney |coauthors=Angus G. Dalgleish; Robin A. Weiss |year=2006 |url=http://www.sciencemag.org/cgi/reprint/313/5786/462.pdf |title=Origins of HIV and the evolution of resistance to AIDS |journal=Science |month=July |volume=313 |issue=5786 |pages=462-466 |pmid=16873637 |doi=10.1126/science.1123016 }}</ref>
The ICTVdB code of SIV is 61.0.6.5.003. [1]
[edit] See also
[edit] References
[edit] External links
- Description of SIV, including links to subspecies and sequence data, from the International Committee on Taxonomy of Viruses
- NIH Taxonomy Browser entry for SIV, access to sequence data and published articles
- Peeters et al.: "Risk to Human Health from a Plethora of Simian Immunodeficiency Viruses in Primate Bushmeat", Emerging Infectious Diseases, Vol 8, No 5, May 2002. Contains a picture of the relationship among the various SIV/HIV strains.
- "HIV origin 'found in wild chimps'" BBC News article
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