Editing Simian immunodeficiency virus

{{Short description|Species of retrovirus}}
{{Virusbox
| name = Simian immunodeficiency virus
| image = SIV virion in 3D.jpg
| image_caption = SIV virion model obtained with cryo-electron microscopy scanning
| parent = Lentivirus
| species = Lentivirus simimdef
}}

'''Simian immunodeficiency virus''' ('''SIV''') is a species of [[retrovirus]] that cause persistent infections in at least 45 species of non-human [[primate]]s.<ref name="Peeters_2001">{{Cite journal | vauthors = Peeters M, Courgnaud V, Abela B | title=Genetic Diversity of Lentiviruses in Non-Human Primates| journal =AIDS Reviews| volume =3| pages =3–10| year =2001| url =https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers19-09/010055042.pdf| access-date =2020-07-11}}</ref><ref name = "Peeters">{{Cite book | vauthors = Peeters M, Courgnaud V | veditors = Kuiken C, Foley B, Freed E, Hahn B, Korber B, Marx PA, McCutchan FE, Mellors JW, Wolinsky S | title = Overview of Primate Lentiviruses and their Evolution in Non-human Primates in Africa | url = http://hcv.lanl.gov/content/sequence/HIV/COMPENDIUM/2002/partI/Peeters.pdf | series = HIV sequence compendium | year = 2002 | pages = 2–23 | place = Los Alamos, NM | publisher = Theoretical Biology and Biophysics Group, Los Alamos National Laboratory | access-date = 2010-09-19 }}</ref> Based on analysis of strains found in four species of [[Old World monkey|monkeys]] from [[Bioko|Bioko Island]], which was isolated from the mainland by [[Sea level#Change|rising sea levels]] about 11,000 years ago, it has been concluded that SIV has been present in monkeys and apes for at least 32,000 years, and probably much longer.<ref name=millennia>{{Cite news |author=McNeil Donald G. Jr |title=Precursor to H.I.V. Was in Monkeys for Millennia |url=https://www.nytimes.com/2010/09/17/health/17aids.html?_r=1&src=me&ref=general |work=[[New York Times]] |date=September 16, 2010 |access-date=2010-09-17 }}</ref><ref>{{cite journal | vauthors = Worobey M, Telfer P, Souquière S, Hunter M, Coleman CA, Metzger MJ, Reed P, Makuwa M, Hearn G, Honarvar S, Roques P, Apetrei C, Kazanji M, Marx PA | display-authors = 6 | title = Island biogeography reveals the deep history of SIV | journal = Science | volume = 329 | issue = 5998 | pages = 1487 | date = September 2010 | pmid = 20847261 | doi = 10.1126/science.1193550 | s2cid = 37803712 | bibcode = 2010Sci...329.1487W }}.</ref>

Virus [[Strain (biology)|strain]]s from three of these primate species, SIVsmm in [[sooty mangabey]]s, SIVgor in [[gorilla]]s and SIVcpz in [[Common chimpanzee|chimpanzees]], are believed to have [[zoonosis|crossed the species barrier]] into humans, resulting in [[HIV-2]] and [[HIV-1]] respectively, the two [[HIV]] viruses. The most likely route of transmission of HIV-1 to humans involves contact with the blood of chimps and gorillas that are often hunted for [[bushmeat]] in Africa. Four subtypes of HIV-1 (M, N, O, and P) likely arose through four separate transmissions of SIV to humans, and the resulting HIV-1 group M strain most commonly infects people worldwide.<ref>{{cite journal | vauthors = Sharp PM, Hahn BH | title = The evolution of HIV-1 and the origin of AIDS | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 365 | issue = 1552 | pages = 2487–2494 | date = August 2010 | pmid = 20643738 | pmc = 2935100 | doi = 10.1098/rstb.2010.0031 }}</ref><ref>{{cite journal | vauthors = Peeters M, D'Arc M, Delaporte E | title = Origin and diversity of human retroviruses | journal = AIDS Reviews | volume = 16 | issue = 1 | pages = 23–34 | date = 2014 | pmid = 24584106 | pmc = 4289907 }}</ref> Therefore, it is theorized that SIV may have previously crossed the species barrier into human hosts multiple times throughout history, but it was not until recently, after the advent of [[History of transport|modern transportation]] and [[commuter|global commuterism]], that it finally took hold, spreading beyond localized decimations of a few individuals or single small tribal populations.

Unlike HIV-1 and HIV-2 infections in humans, SIV infections in their natural simian non-human hosts appear in many cases to be non-pathogenic due to evolutionary adaptation of the hosts to the virus. Extensive studies in sooty mangabeys have established that SIVsmm infection does not cause any disease in these primates, despite high levels of circulating virus. Regulation of the activity of the [[CCR5]] coreceptor is one of the natural strategies to avoid disease in some natural host species of SIV.<ref>{{Cite journal |vauthors = Jasinska AJ, Pandrea I, Apetrei C |date=2022-01-27 |title=CCR5 as a Coreceptor for Human Immunodeficiency Virus and Simian Immunodeficiency Viruses: A Prototypic Love-Hate Affair |journal=Frontiers in Immunology |volume=13 |pages=835994 |doi=10.3389/fimmu.2022.835994 |pmid=35154162 |issn=1664-3224 |pmc= 8829453 |doi-access=free}}</ref>

Research on SIVcpz in chimpanzees suggests that infected chimpanzees experience an AIDS-like illness similar to HIV-1 infected humans. The later stages of SIVcpz infection in chimpanzees develop into an illness with characteristics that strongly resemble end-stage AIDS in humans.<ref>{{cite journal|vauthors=Peeters M, Delaporte E|date=June 2012|title=Simian retroviruses in African apes|journal=Clin Microbiol Infect|volume=18|issue=6|pages=514–520|doi= 10.1111/j.1469-0691.2012.03843.x|pmc=|pmid=22515409|url=https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(14)64143-4/fulltext}}</ref>

==Taxonomy==
The simian (monkey-hosted) immunodeficiency viruses are a species of retrovirus in the Primate group of genus ''[[Lentivirus]]'' along with the human viruses [[HIV-1]] and [[HIV-2]] that cause AIDS, and a few other viruses that infect other primates.  Related viruses in other groups in the genus infect other mammals like sheep and goats, horses, cattle, cats, and a few others. The genus is one of six genera in subfamily ''[[Orthoretrovirinae]]'', which together with subfamily ''[[Spumaretrovirinae]]'' form the family ''[[Retroviridae]]'' of all RNA retroviruses (RNA viruses which use a DNA intermediate).<ref>{{cite web |title=Taxon Details {{!}} ICTV |url=https://ictv.global/taxonomy/taxondetails?taxnode_id=202105034 |website=ictv.global}}</ref>

The [[ICTVdB]] code of SIV is 61.0.6.5.003.<ref>[https://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/61065003.htm ICTV database entry: 61.0.6.5.003]</ref> Although HIV-1 and HIV-2 cladistically fall into SIV,<ref name=pmid22229120/> ICTV considers them distinct species from ordinary, non-human-infecting SIV.

===Strains===
{{Cladogram|width=220|style="float:right;"
|caption=Phylogenetic relations between simian immunodeficiency viruses (SIVs)<ref name=pmid22229120>{{cite journal | vauthors = Sharp PM, Hahn BH | title = Origins of HIV and the AIDS pandemic | journal = Cold Spring Harbor Perspectives in Medicine | volume = 1 | issue = 1 | pages = a006841 | date = September 2011 | pmid = 22229120 | pmc = 3234451 | doi = 10.1101/cshperspect.a006841 }}</ref><ref>{{cite journal | vauthors = Ahuka-Mundeke S, Ayouba A, Mbala-Kingebeni P, Liegeois F, Esteban A, Lunguya-Metila O, Demba D, Bilulu G, Mbenzo-Abokome V, Inogwabini BI, Muyembe-Tamfum JJ, Delaporte E, Peeters M | display-authors = 6 | title = Novel multiplexed HIV/simian immunodeficiency virus antibody detection assay | journal = Emerging Infectious Diseases | volume = 17 | issue = 12 | pages = 2277–2286 | date = December 2011 | pmid = 22172157 | pmc = 3311211 | doi = 10.3201/eid1712.110783 }}</ref><ref>{{cite book | vauthors = Pancino G, Silvestri G, Fowke KR |title=Models of Protection Against HIV/SIV: Avoiding AIDS in Humans and Monkeys|date=2012|publisher=Elsevier|isbn=978-0-12-387715-4|page=6}}</ref><ref>{{cite journal | vauthors = Peeters M, Courgnaud V, Abela B, Auzel P, Pourrut X, Bibollet-Ruche F, Loul S, Liegeois F, Butel C, Koulagna D, Mpoudi-Ngole E, Shaw GM, Hahn BH, Delaporte E | display-authors = 6 | title = Risk to human health from a plethora of simian immunodeficiency viruses in primate bushmeat | journal = Emerging Infectious Diseases | volume = 8 | issue = 5 | pages = 451–457 | date = May 2002 | pmid = 11996677 | pmc = 2732488 | doi = 10.3201/eid0805.010522 }}</ref><ref>{{cite journal | vauthors = Lauck M, Switzer WM, Sibley SD, Hyeroba D, Tumukunde A, Weny G, Taylor B, Shankar A, Ting N, Chapman CA, Friedrich TC, Goldberg TL, O'Connor DH | display-authors = 6 | title = Discovery and full genome characterization of two highly divergent simian immunodeficiency viruses infecting black-and-white colobus monkeys (Colobus guereza) in Kibale National Park, Uganda | journal = Retrovirology | volume = 10 | pages = 107 | date = October 2013 | pmid = 24139306 | pmc = 4016034 | doi = 10.1186/1742-4690-10-107 | doi-access = free }}</ref>
|clades=
{{clade|style=font-size:85%;line-height:85%
|1={{clade
   |1={{clade
            |label1=grp i
            |1={{clade
               |label1=
               |1={{clade
                  |label1=
                  |1={{clade
                     |label1=
                     |1={{clade
                        |label1=
                        |1=<u>HIV-1</u>
                        |label2=
                        |2=cpzPtt
                        }}
                     |label2=
                     |2=gor
                     }}
                  |label2=
                  |2=cpzPts
                  }}
               |label2=
               |2={{clade
                  |label1=
                  |1={{clade
                     |label1=
                     |1=drl
                     |label2=
                     |2=mnd2
                     }}
                  |label2=
                  |2={{clade
                     |label1=
                     |1=rcm
                     |label2=
                     |2=agi
                     }}
                  }}
               }}

            |label2=grp ii
            |2={{clade
               |label1=
               |1={{clade
                  |label1=
                  |1={{clade
                     |label1=
                     |1=<u>HIV-2</u>
                     |label2=
                     |2=mac
                  }}
                  |label2=
                  |2=mne
                  |label3=
                  |3=stm
                  }}
               |label2=
               |2=smm
               }}
      }}

            |label2=grp iii/agm
            |2={{clade
               |label1=
               |1={{clade
                  |label1=
                  |1={{clade
                     |label1=
                     |1=gri
                     |label2=
                     |2=ver
                     }}
                  |label2=
                  |2=tan
                  }}
               |label2=
               |2=sab
               }}

      |label3=grp iv
      |3={{clade
         |1={{clade
            |label1=
            |1={{clade
               |label1=
               |1={{clade
                  |label1=
                  |1=lho
                  |label2=
                  |2=sun
                  }}
               |label2=
               |2=prg
               }}
            |label2=
            |2=mnd1
            }}
         |label2=
         |2={{clade
            |label1=
            |1={{clade
               |label1=
               |1=wrc
               |label2=
               |2=olc
               }}
            |label2=
            |2={{clade
               |label1=
               |1=trc
               |label2=
               |2=krc
               }}
            }}
         }}

   }}

   |label2=grp v
   |2={{clade
         |label1=
         |1={{clade
            |label1=
            |1={{clade
               |label1=
               |1={{clade
                  |label1=
                  |1={{clade
                     |label1=
                     |1={{clade
                        |label1=
                        |1=gsn
                        |label2=
                        |2={{clade
                           |1=mus2

                           |label2=(grp vi)
                           |2={{clade
                              |label1=
                              |1={{clade
                                 |label1=
                                 |1={{clade
                                    |label1=
                                    |1=col
                                    |label2=
                                    |2=kcol1
                                    }}
                                 |label2=
                                 |2=kcol2
                                 }}
                                 |2=blc
                              }}

                           }}
                        }}
                     |label2=
                     |2=mon
                     |label3=
                     |3=mus1
                     }}
                  |2=reg
                  }}
               |label2=
               |2={{clade
                  |label1=
                  |1=tal
                     |label2=
                     |2={{clade
                     |label1=
                     |1=asc
                     |label2=
                     |2=bkm
                     }}
                  }}
               }}
            |label2=
            |2={{clade
               |label1=
               |1=deb
               |2=blu|state2=dashed
               |label3=
               |3={{clade
                  |label1=
                  |1={{clade
                     |label1=
                     |1=den
                     |label2=
                     |2=syk
                     }}
                  |label2=
                  |2=wol
                  }}
               }}
            }}
         }}
      }}
   }}
While human immunodeficiency virus has a limited number of subtypes, SIV is now known to infect a few dozen species of non-human primates, and distinct strains are often associated with each species, or with a set of closely related species.  The thus far categorized ~40 strains are divided into five distinct groups and one subgroup:<ref name=pmid22229120/>
* i) HIV-1, SIVcpz ([[Common chimpanzee|chimpanzee]]), SIVgor ([[gorilla]]), SIVrcm ([[red-capped mangabey]]), SIVagi ([[agile mangabey]]), SIVmnd 2 ([[mandrill]]), SIVdrl ([[drill monkey]])
* ii) HIV-2, SIVsmm ([[sooty mangabey]]), SIVmac ([[rhesus macaque]]), SIVmne ([[pig-tailed macaque]]), SIVstm ([[stump-tailed macaque]])
* iii) SIVagm[generic] ([[African green monkeys]]): SIVsab, SIVver, SIVgri ([[grivet monkey]]), SIVtan ([[tantalus monkey]])
* iv) SIVmnd 1 ([[mandrill]]), SIVlho ([[L'hoest's monkey]]), SIVsun ([[sun-tailed monkey]]), SIVprg ([[Preuss's guenon]]), SIVwrc ([[western red colobus]]), SIVolc ([[olive colobus]]), SIVkrc ([[Kibale red colobus]]), SIVtrc ([[Tshuapa red colobus]])
* v) SIVsyk ([[Sykes' monkey]]), SIVdeb ([[De Brazza's monkey]]), SIVden ([[Dent's mona monkey]]), SIVwol ([[Wolf's mona monkey]]), SIVgsn/SIVmon/SIVmus 1/SIVmus 2 clade, SIVtal ([[northern talapoin]]), SIVasc ([[red-tailed guenon]]), SIVbkm ([[black mangabey]]), SIVreg[formerly SIVery] ([[red-eared guenon]]), SIVblu (blue monkey)
** vi) SIVcol ([[colobus guereza]]), SIVkcol 1 ([[black-and-white colobus]]), SIVkcol 2, SIVblc (formerly SIVbcm) ([[black colobus]]),

In addition to the subgroups defined for extent SIVs, two endogenous SIVs are found in prosimian lemurs. These paleo-SIVs form a basal branch relative to extant SIVs.<ref name=pmid19300488>{{cite journal |last1=Gilbert |first1=C |last2=Maxfield |first2=DG |last3=Goodman |first3=SM |last4=Feschotte |first4=C |title=Parallel germline infiltration of a lentivirus in two Malagasy lemurs. |journal=PLOS Genetics |date=March 2009 |volume=5 |issue=3 |pages=e1000425 |doi=10.1371/journal.pgen.1000425 |pmid=19300488 |pmc=2651035 |doi-access=free}}</ref>

==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>

==Virology==
===Structure and genome===
The SIV virion is a spherical to pleomorphic glycoprotein envelope 110-120&nbsp;nm across enclosing a 110x50nm truncated cone or wedge-shaped (occasionally rod) capsid containing a [[dimer (chemistry)|dimer]]ic pair of [[positive-sense single-stranded RNA virus|positive-sense single-stranded RNA]] genomes.{{citation needed|date=November 2022}}

====Genome====
* coding regions

====Proteome====
{{Further|Structure and genome of HIV#Genome organization}}
* genes: ''env'', ''gag'', ''pol'', ''tat'', ''rev'', ''nef'', ''vpr'', ''vif'', ''vpu/vpx''
* Structural proteins (envelope): SU, TM(gag): MA, CA, NC
* Enzymes: RT, PR, IN
* Gene regulators: Tat, Rev
* Accessory proteins: Nef, Vpr, Vpx, Vif

===Tropism===
Differences in species specificity of SIV and related retroviruses may be partly explained by variants of the protein [[TRIM5-alpha|TRIM5α]] in humans and non-human primate species. This intracellular protein recognizes the [[capsid]] of various retroviruses and blocks their reproduction. Other proteins, such as [[APOBEC3G]]/[[APOBEC3F|3F]], which exerts antiretroviral immune activity, may also be important in restricting cross-species transmission.<ref>{{cite journal | vauthors = Heeney JL, Dalgleish AG, Weiss RA | title = Origins of HIV and the evolution of resistance to AIDS | journal = Science | volume = 313 | issue = 5786 | pages = 462–466 | date = July 2006 | pmid = 16873637 | doi = 10.1126/science.1123016 | s2cid = 27673160 | bibcode = 2006Sci...313..462H }}</ref>

===Replication===
* Attachment
* Penetration
* Uncoating
* Replication
** reverse transcription
  +ssRNA → -ssDNA → dsDNA → +ssRNA (viral genome)
                          → +ssmRNA → viral protein
:*integration
:*latency
:*cleavage
:*protein synthesis
:*Assembly
* Budding
* Maturation

===Quasispecies===
The speed and transcription inaccuracies of RNA viruses give rise to antigenically distinct varieties in a single host animal.  These ''[[viral quasispecies|quasispecies]]'' do not necessarily give rise to population-wide new organisms.  The rate of proliferation of quasispecies has significant implication for host immune control, and therefore virulence of the organism.{{citation needed|date=November 2022}}

==Pathogenesis==
[[File:Mapping SHIV infection in the body, 2018 - Wellcome Photography Prize 2019 (bottom right, cropped).jpg|thumb|About 100,000 cells from [[rhesus macaque]]s, grouped by similarity. Red cells are from monkeys infected with simian-human immunodeficiency virus, while blue cells are from uninfected ones.]]
SIV pathogenesis encompasses both pathogenic and non-pathogenic SIV infections. SIV infection of non-human primates (NHPs) invariably results in persistent infection, but rarely acute disease. Pathogenic infection is typified by Rhesus macaques infected with SIV strains derived from sooty mangabeys. Disease progression to AIDS occurs within a period of months to years, depending upon the SIV strain used. Non-pathogenic infection is typified by African NHPs naturally infected with SIV. These animals rarely progress to AIDS despite maintaining viral loads that are equivalent to SIV viral loads in pathogenic infections. It is postulated that AIDS-like disease in African NHPs represents horizontal transmission of the virus from one or more homologous species in the recent evolutionary past, before equilibrium of co-adaptation has occurred.{{citation needed|date=November 2022}}

== SIV/HIV infection similarities and differences ==
The similarities of the two types of virus infections:<ref>{{Cite journal |last1=Pandrea |first1=Ivona |last2=Sodora |first2=Donald L. |last3=Silvestri |first3=Guido |last4=Apetrei |first4=Cristian |date=September 2008 |title=Into the Wild: Simian Immunodeficiency Virus (SIV) Infection in Natural Hosts |journal=Trends in Immunology |volume=29 |issue=9 |pages=419–428 |doi=10.1016/j.it.2008.05.004 |issn=1471-4906 |pmc=2840226 |pmid=18676179}}</ref>
* high level of virus replication during primary infection (0–180 days)
* high level of CD4+ T-cell loss (0–180 days)
* restricted role of humoral immune response

The differences (what happens in nonhuman primates):
* lower level of CCR5+ T-cells
* stable level of viral replication (180 days-years)
* restoration of CD4+ T-cells
* early cytokine production (0–10 days after infection)
* normal level of immune activation
* high level of functional immune cells
* establishment of anti-inflammatory milieu

==Epidemiology==
{| {{Table}}
! strain !! lineage !! host  !! binomial !! disease
|-
! HIV-1
| SIVcpz
| humans
| H. sapiens
| [[AIDS]]
|-
! HIV-2
| SIVsmm
| humans
| H. sapiens
| [[AIDS]]
|-
! SIVcpz
| SIVrcm/SIVgsn
| Chimpanzee
| P. Troglodytes
| SAIDS
|-
! SIVgor
| SIVcpz
| Gorilla
| G. gorilla
| ( - )
|-
! SIVsmm
|
| Sooty mangabey
|
| ( - )
|}

[[Beatrice Hahn]] of the [[University of Pennsylvania]] and a team of researchers in 2009 found that chimpanzees do die from simian AIDS in the wild and that the AIDS outbreak in Africa has contributed to the decline of chimpanzee populations. Testing wild chimpanzees, researchers detected organ and tissue damage similar to late-stage human AIDS. The infected chimpanzees had a 10 to 16 times greater risk of dying than uninfected ones; infected females were less likely to give birth, could pass the virus to their infants, and had a higher infant mortality rate than uninfected females.<ref>[https://www.nytimes.com/2009/07/23/science/23chimp.html?ref=science Chimpanzees Do Die From Simian AIDS, Study Finds by Lawrence K. Altman] Chimpanzees Do Die from Simian AIDS, Study Finds</ref><ref>{{cite journal | vauthors = Keele BF, Jones JH, Terio KA, Estes JD, Rudicell RS, Wilson ML, Li Y, Learn GH, Beasley TM, Schumacher-Stankey J, Wroblewski E, Mosser A, Raphael J, Kamenya S, Lonsdorf EV, Travis DA, Mlengeya T, Kinsel MJ, Else JG, Silvestri G, Goodall J, Sharp PM, Shaw GM, Pusey AE, Hahn BH | display-authors = 6 | title = Increased mortality and AIDS-like immunopathology in wild chimpanzees infected with SIVcpz | journal = Nature | volume = 460 | issue = 7254 | pages = 515–519 | date = July 2009 | pmid = 19626114 | pmc = 2872475 | doi = 10.1038/nature08200 | bibcode = 2009Natur.460..515K }}</ref> [[Bonobo]]s appear to avoid simian immunodeficiency virus (SIV) and its effects, though it is not known why.<ref name="Sharp_2005" />

African green monkeys (also called vervets, genus Chlorocebus) in African populations are heavily infected with SIVagm,<ref name=":0">{{cite journal | vauthors = Ma D, Jasinska A, Kristoff J, Grobler JP, Turner T, Jung Y, Schmitt C, Raehtz K, Feyertag F, Martinez Sosa N, Wijewardana V, Burke DS, Robertson DL, Tracy R, Pandrea I, Freimer N, Apetrei C | display-authors = 6 | title = SIVagm infection in wild African green monkeys from South Africa: epidemiology, natural history, and evolutionary considerations | journal = PLOS Pathogens | volume = 9 | issue = 1 | pages = e1003011 | date = January 2013 | pmid = 23349627 | pmc = 3547836 | doi = 10.1371/journal.ppat.1003011 | doi-access = free }}</ref><ref name=":1">{{cite journal | vauthors = Ma D, Jasinska AJ, Feyertag F, Wijewardana V, Kristoff J, He T, Raehtz K, Schmitt CA, Jung Y, Cramer JD, Dione M, Antonio M, Tracy R, Turner T, Robertson DL, Pandrea I, Freimer N, Apetrei C | display-authors = 6 | title = Factors associated with siman immunodeficiency virus transmission in a natural African nonhuman primate host in the wild | journal = Journal of Virology | volume = 88 | issue = 10 | pages = 5687–5705 | date = May 2014 | pmid = 24623416 | pmc = 4019088 | doi = 10.1128/JVI.03606-13 }}</ref> while the virus is absent in the founder isolate vervet populations in the Caribbean.<ref>{{cite journal | vauthors = Kapusinszky B, Mulvaney U, Jasinska AJ, Deng X, Freimer N, Delwart E | title = Local Virus Extinctions following a Host Population Bottleneck | journal = Journal of Virology | volume = 89 | issue = 16 | pages = 8152–8161 | date = August 2015 | pmid = 26018153 | pmc = 4524239 | doi = 10.1128/jvi.00671-15 | doi-access = free }}</ref> The prevalence of SIV infection in African populations ranges 78-90% in adult females and 36-57% in adult males, while SIV infection is rare in immature individuals.<ref name=":1" /><ref name=":0" /> SIV infected vervets in the wild do not develop chronic immune activation or microbial translocation (assessed by sCD14 as a surrogate biomarker). During natural SIV infection, the gut microbiome showed a significant increase in microbial diversity, a decrease in Proteobacteria/Succinivibrio and an increase of Veillonella, a decrease in genes involved in pathways of microbial invasion, and partial reversibility of acute infection-related shifts in microbial abundance.<ref>{{cite journal | vauthors = Jasinska AJ, Dong TS, Lagishetty V, Katzka W, Jacobs JP, Schmitt CA, Cramer JD, Ma D, Coetzer WG, Grobler JP, Turner TR, Freimer N, Pandrea I, Apetrei C | display-authors = 6 | title = Shifts in microbial diversity, composition, and functionality in the gut and genital microbiome during a natural SIV infection in vervet monkeys | journal = Microbiome | volume = 8 | issue = 1 | pages = 154 | date = November 2020 | pmid = 33158452 | pmc = 7648414 | doi = 10.1186/s40168-020-00928-4 | doi-access = free }}</ref> The pattern of natural selection in the monkey genome in genes involved in HIV responses and those regulated in response to experimental SIV infection in monkeys, but not macaques, suggests a natural adaptation to SIV in Chlorocebus monkeys in Africa.<ref>{{cite journal | vauthors = Svardal H, Jasinska AJ, Apetrei C, Coppola G, Huang Y, Schmitt CA, Jacquelin B, Ramensky V, Müller-Trutwin M, Antonio M, Weinstock G, Grobler JP, Dewar K, Wilson RK, Turner TR, Warren WC, Freimer NB, Nordborg M | display-authors = 6 | title = Ancient hybridization and strong adaptation to viruses across African vervet monkey populations | journal = Nature Genetics | volume = 49 | issue = 12 | pages = 1705–1713 | date = December 2017 | pmid = 29083404 | pmc = 5709169 | doi = 10.1038/ng.3980 }}</ref>

==Vaccine research==
In 2012, researchers reported that initial infection of [[rhesus macaque|rhesus monkeys]] by neutralization-resistant SIV strains<ref>"Neutralization-resistant" refers to strains which are not able to be neutralized by the native immune response due to compensating mutation; see [[Antigenic variation#HIV-1|HIV-1 related information]].</ref> could be partially prevented through use of an anti-SIV<sub>SME543</sub> vaccine obligately including [[Env (gene)|Env]] protein antigens.<ref>{{cite journal | vauthors = Barouch DH, Liu J, Li H, Maxfield LF, Abbink P, Lynch DM, Iampietro MJ, SanMiguel A, Seaman MS, Ferrari G, Forthal DN, Ourmanov I, Hirsch VM, Carville A, Mansfield KG, Stablein D, Pau MG, Schuitemaker H, Sadoff JC, Billings EA, Rao M, Robb ML, Kim JH, Marovich MA, Goudsmit J, Michael NL | display-authors = 6 | title = Vaccine protection against acquisition of neutralization-resistant SIV challenges in rhesus monkeys | journal = Nature | volume = 482 | issue = 7383 | pages = 89–93 | date = January 2012 | pmid = 22217938 | pmc = 3271177 | doi = 10.1038/nature10766 | bibcode = 2012Natur.482...89B}}
* {{cite magazine |author=Simeon Bennett |date=January 4, 2012 |title=J&J AIDS Vaccine Helps Protect Monkeys From Virus in Study |magazine=Bloomberg |url=https://www.bloomberg.com/news/2012-01-04/j-j-aids-vaccine-protects-monkeys-in-study-as-human-trials-begin.html |url-access=subscription}}</ref>

In 2013, a study by a group of authors reported on successful testing of a vaccine containing SIV protein-expressing rhesus cytomegalovirus vector. Approximately 50% of vaccinated rhesus macaques manifested durable, aviraemic control of infection with the highly pathogenic strain SIVmac239.<ref>{{cite journal | vauthors = Hansen SG, Piatak M, Ventura AB, Hughes CM, Gilbride RM, Ford JC, Oswald K, Shoemaker R, Li Y, Lewis MS, Gilliam AN, Xu G, Whizin N, Burwitz BJ, Planer SL, Turner JM, Legasse AW, Axthelm MK, Nelson JA, Früh K, Sacha JB, Estes JD, Keele BF, Edlefsen PT, Lifson JD, Picker LJ | display-authors = 6 | title = Immune clearance of highly pathogenic SIV infection | journal = Nature | volume = 502 | issue = 7469 | pages = 100–104 | date = October 2013 | pmid = 24025770 | pmc = 3849456 | doi = 10.1038/nature12519 | bibcode = 2013Natur.502..100H }}</ref>

== See also ==
* [[HIV]], the human version of SIV which causes AIDS
* [[Positive-sense single-stranded RNA virus]], a classification which includes SIV
* [[Zoonosis]] and [[History of HIV/AIDS#Transmission from non-humans to humans|Origin of AIDS]], transmission from other primates to humans
* [[List of zoonotic primate viruses]]
* Other simian exogenous retroviruses: [[simian-T-lymphotropic virus]], [[simian retrovirus]] type D, [[gibbon ape leukemia virus]], [[simian foamy virus]], [[simian sarcoma virus]]
* Related viruses also cause disease in other mammals: [[Visna/maedi virus|sheep]], [[Caprine arthritis encephalitis virus|goats]], [[Feline immunodeficiency virus|cats]], [[Bovine immunodeficiency virus|cattle]], [[Equine infectious anemia virus|horses]]
* [[SV40]] is another virus that came from simians and into human populations in the mid twentieth century.

== References ==
{{Reflist|30em}}

== Further reading ==
* [http://news.bbc.co.uk/1/hi/health/5012268.stm "HIV origin 'found in wild chimps'"] BBC News article
* Peeters ''et al.'': [https://wwwnc.cdc.gov/eid/article/8/5/01-0522_article "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.

== External links ==
{{Commons category|Simian immunodeficiency virus}}
* [https://web.archive.org/web/20050517095244/http://phene.cpmc.columbia.edu/RothamstedMirror/ICTVdB/61065003.htm Description of SIV], including links to subspecies and sequence data, from the [[International Committee on Taxonomy of Viruses]]

{{Retroviruses}}
{{Taxonbar|from=Q1890246}}
{{Authority control}}

{{DEFAULTSORT:Simian Immunodeficiency Virus}}
[[Category:Lentiviruses]]
[[Category:Primate diseases]]
[[Category:Animal viral diseases]]
[[Category:Simians]]