Editing Simian immunodeficiency virus (section)

==History==
Immunodeficiency resembling human AIDS was reported in captive monkeys in the United States beginning in 1983.<ref name=pmid6221343>{{cite journal | vauthors = Letvin NL, Eaton KA, Aldrich WR, Sehgal PK, Blake BJ, Schlossman SF, King NW, Hunt RD | display-authors = 6 | title = Acquired immunodeficiency syndrome in a colony of macaque monkeys | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 80 | issue = 9 | pages = 2718–2722 | date = May 1983 | pmid = 6221343 | pmc = 393899 | doi = 10.1073/pnas.80.9.2718 | doi-access = free | bibcode = 1983PNAS...80.2718L }}</ref><ref name=pmid3159089/><ref name=pmid6316791>{{cite journal | vauthors = King NW, Hunt RD, Letvin NL | title = Histopathologic changes in macaques with an acquired immunodeficiency syndrome (AIDS) | journal = The American Journal of Pathology | volume = 113 | issue = 3 | pages = 382–388 | date = December 1983 | pmid = 6316791 | pmc = 1916356 }}</ref> SIV was isolated in 1985 from some of these animals, captive [[rhesus macaque]]s suffering from simian AIDS (SAIDS).<ref name=pmid3159089>{{cite journal | vauthors = Daniel MD, Letvin NL, King NW, Kannagi M, Sehgal PK, Hunt RD, Kanki PJ, Essex M, Desrosiers RC | display-authors = 6 | title = Isolation of T-cell tropic HTLV-III-like retrovirus from macaques | journal = Science | volume = 228 | issue = 4704 | pages = 1201–1204 | date = June 1985 | pmid = 3159089 | doi = 10.1126/science.3159089 | bibcode = 1985Sci...228.1201D }}</ref> The discovery of SIV was made shortly after HIV-1 had been isolated as the cause of AIDS and led to the discovery of HIV-2 strains in West Africa. 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 SIVsmm strain found in sooty mangabeys, whereas HIV-1, the predominant virus found in humans, is derived from SIV strains infecting chimpanzees (SIVcpz).{{citation needed|date=December 2016}}

It is not believed that chimpanzees are the original hosts of an independent lineage of SIV, but rather that SIVcpz is a relatively recent acquisition resulting from a recombination of SIVgsn ([[greater spot-nosed monkey]]s) and SIVrcm ([[red-capped mangabey]]s) within the host chimpanzee.  It is known that chimpanzees hunt and consume these monkeys for food.<ref name="Sharp_2005">{{cite journal | vauthors = Sharp PM, Shaw GM, Hahn BH | title = Simian immunodeficiency virus infection of chimpanzees | journal = Journal of Virology | volume = 79 | issue = 7 | pages = 3891–3902 | date = April 2005 | pmid = 15767392 | pmc = 1061584 | doi = 10.1128/JVI.79.7.3891-3902.2005 }}</ref> In 2010, researchers reported that SIV had infected monkeys in [[Bioko]] for at least 32,000 years.  Based on [[molecular clock]] analyses of sequences, it was previously thought by many that SIV infection in monkeys had happened over the past few hundred years.<ref name=millennia /> Scientists estimated that it would take a similar amount of time before humans would adapt naturally to HIV infection in the way monkeys in Africa have adapted to SIV and not suffer any harm from the infection.<ref name="cbc20100917">{{Cite web|url=https://www.cbc.ca/news/science/hiv-precursor-in-monkeys-ancient-study-1.870840 |title=HIV precursor in monkeys ancient: study |date=17 September 2010 |publisher=CBC News |access-date=17 September 2010 |url-status=live |archive-url=https://web.archive.org/web/20130325062955/http://www.cbc.ca/news/health/story/2010/09/16/hiv-monkeys-siv-age.html |archive-date=March 25, 2013 }}</ref>

In 2008, discovery of an endogenous lentivirus in a prosimian (proto-monkey) primate, the gray mouse lemur native to Madagascar, pushed the origin of SIV-like lentivirus infections in primates back to at least 14 Ma, the last time there was intermingling of mammals between the island of Madagascar and the African mainland, if the infection is attributed to horizontal transmission between homologous hosts. If the virus was coevolved with the host, rather than acquired, that potentially pushes the date of the endogenous event back to approx. 85 Ma, the split between the [[strepsirrhini|lemur-like]] and [[haplorhini|monkey-like]] primate lineages.  That date barely antedates the emergence of the primates 87.7 Ma.<ref>{{cite journal |last1=Gifford |first1=RJ |last2=Katzourakis |first2=A |last3=Tristem |first3=M |last4=Pybus |first4=OG |last5=Winters |first5=M |last6=Shafer |first6=RW |title=A transitional endogenous lentivirus from the genome of a basal primate and implications for lentivirus evolution. |journal=Proceedings of the National Academy of Sciences of the United States of America |date=23 December 2008 |volume=105 |issue=51 |pages=20362–7 |doi=10.1073/pnas.0807873105 |pmid=19075221 |pmc=2603253 |doi-access=free }}</ref>