Simian immunodeficiency virus

Simian immunodeficiency virus
Virus classification
Group: Group VI (ssRNA-RT)
Order: Unassigned
Family: Retroviridae
Subfamily: Orthoretrovirinae
Genus: Lentivirus
Species: Simian immunodeficiency virus
Diagrammatical representation of the molecular structure of HIV-1 protease complexed with the inhibitor indinavir.

Simian immunodeficiency viruses (SIVs) are retroviruses able to infect at least 45 species of African non-human primates.[1][2] Based on analysis of strains found in four species of monkeys from Bioko Island, which was isolated from the mainland by 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.[3][4]

Virus strains 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.[3]

Unlike HIV-1 and HIV-2 infections in humans, SIV infections in their natural hosts appear in many cases 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 infects an Asian or Indian rhesus macaque, the animal will develop simian AIDS (SAIDS).[5] A recent study of SIVcpz in wild living chimpanzees suggests that infected chimpanzees experience an AIDS-like illness similar to HIV-1 infected humans. The later stages of SIV infection turn into SAIDS, much as HIV infection turns into AIDS.

History

Immunodeficiency resembling human AIDS was reported in captive monkeys in the United States beginning in 1983.[6][7][8] SIV was isolated in 1985 from some of these animals, captive rhesus macaques suffering from simian AIDS (SAIDS).[7] 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).

Tropism

Differences in species specificity of SIV and related retroviruses may be partly explained by variants of the protein 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/3F may also be important in restricting cross-species transmission.

Research

SHIV, a virus combining parts of the HIV and SIV genomes, was created for various research purposes, including analyzing how different parts of the virus respond to different antimicrobial drugs and vaccines.[9]

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.[10][11]

The ICTVdB code of SIV is 61.0.6.5.003.[12]

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.[13] 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.[14]

In 2012, researchers reported that initial infection of rhesus monkeys by neutralization-resistant SIV strains[15] could be partially prevented through use of an anti-SIVSME543 vaccine obligately including Env protein antigens.[16]

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.[17]

Bonobos appear to avoid simian immunodeficiency virus (SIV) and its effects, though it is not known why.[18]

See also

References

  1. ↑ Peeters, M.; Courgnaud, V.; Abela, B. (2001). "Genetic Diversity of Lentiviruses in Non-Human Primates" (PDF). AIDS Reviews 3: 3–10. Retrieved 2010-09-19.
  2. ↑ Peeters, M.; Courgnaud, V. (2002). "Overview of Primate Lentiviruses and their Evolution in Non-human Primates in Africa" (PDF). In C. Kuiken, B. Foley, E. Freed, B. Hahn, B. Korber, P. A. Marx, F. E. McCutchan, J. W. Mellors, and S. Wolinsky. HIV sequence compendium. Los Alamos, NM: Theoretical Biology and Biophysics Group, Los Alamos National Laboratory. pp. 2–23. Retrieved 2010-09-19 Missing or empty |title= (help)
  3. 1 2 Donald G. McNeil, Jr. (September 16, 2010). "Precursor to H.I.V. Was in Monkeys for Millennia". New York Times. Retrieved 2010-09-17. In a discovery that sheds new light on the history of AIDS, scientists have found evidence that the ancestor to the virus that causes the disease has been in monkeys and apes for at least 32,000 years — not just a few hundred years, as had been previously thought. ... That means humans have presumably been exposed many times to S.I.V., the simian immunodeficiency virus, because people have been hunting monkeys for millenniums, risking infection every time they butcher one for food.
  4. ↑ Worobey, Michael; Telfer, Paul; Souquière, Sandrine; Hunter, Meredith; Coleman, Clint A.; Metzger, Michael J.; Reed, Patricia; Makuwa, Maria; Hearn, Gail (2010). "Island Biogeography Reveals the Deep History of SIV". Science 329 (5998): 1487. Bibcode:2010Sci...329.1487W. doi:10.1126/science.1193550. PMID 20847261..
  5. ↑ Kestler, H.; Kodama, T.; Ringler, D.; Marthas, M.; Pedersen, N.; Lackner, A.; Regier, D.; Sehgal, P.; Daniel, M.; King, N.; Et, A. (1990). "Induction of AIDS in rhesus monkeys by molecularly cloned simian immunodeficiency virus". Science 248 (4959): 1109–1112. doi:10.1126/science.2160735. PMID 2160735.
  6. ↑ Letvin, N.; Eaton, K.; Aldrich, W.; Sehgal, P.; Blake, B.; Schlossman, S.; King, N.; Hunt, R. (1983). "Acquired immunodeficiency syndrome in a colony of macaque monkeys". Proceedings of the National Academy of Sciences of the United States of America 80 (9): 2718–2722. Bibcode:1983PNAS...80.2718L. doi:10.1073/pnas.80.9.2718. PMC 393899. PMID 6221343.
  7. 1 2 Daniel, M. D.; Letvin, N. L.; King, N. W.; Kannagi, M.; Sehgal, P. K.; Hunt, R. D.; Kanki, P. J.; Essex, M.; Desrosiers, R. C. (1985). "Isolation of T-cell tropic HTLV-III-like retrovirus from macaques". Science 228 (4704): 1201–1204. Bibcode:1985Sci...228.1201D. doi:10.1126/science.3159089. PMID 3159089.
  8. ↑ King, N. W.; Hunt, R. D.; Letvin, N. L. (1983). "Histopathologic changes in macaques with an acquired immunodeficiency syndrome (AIDS)". The American Journal of Pathology 113 (3): 382–388. PMC 1916356. PMID 6316791.
  9. ↑ e., L.; Srinivasan, P.; m., J. (2012). "Simian-Human Immunodeficiency Viruses and Their Impact on Non-Human Primate Models for AIDS". Immunodeficiency. doi:10.5772/53556. ISBN 978-953-51-0791-0.
  10. ↑ Chimpanzees Do Die From Simian AIDS, Study Finds by Lawrence K. Altman Chimpanzees Do Die from Simian AIDS, Study Finds
  11. ↑ Jonathan L. Heeney; Angus G. Dalgleish; Robin A. Weiss (July 2006). "Origins of HIV and the evolution of resistance to AIDS" (PDF). Science 313 (5786): 462–466. Bibcode:2006Sci...313..462H. doi:10.1126/science.1123016. PMID 16873637.
  12. ↑ ICTV database entry: 61.0.6.5.003
  13. ↑ McNeil Jr, Donald (17 September 2010). "Precursor to H.I.V. Was in Monkeys for Millenniums". The New York Times. Retrieved 17 September 2010.
  14. ↑ "HIV precursor in monkeys ancient: study". CBC News. 17 September 2010. Archived from the original on March 25, 2013. Retrieved 17 September 2010.
  15. ↑ "Neutralization-resistant" refers to strains which are not able to be neutralized by the native immune response due to compensating mutation; see HIV-1 related information.
  16. ↑ Barouch, Dan H.; et al. (25 additional authors) (4 Jan 2012), "Vaccine protection against acquisition of neutralization-resistant SIV challenges in rhesus monkeys", Nature 482, advance online publication, Bibcode:2012Natur.482...89B, doi:10.1038/nature10766, retrieved 6 Jan 2012. Lay summary available from Bloomberg at "J&J AIDS Vaccine Protects Monkeys in Study as Testing in Humans Begins", published 4 Jan 2012.
  17. ↑ Hansen, Scott G.; et al. (2013). "Immune clearance of highly pathogenic SIV infection". Nature 502 (7469): 100–104. doi:10.1038/nature12519.
  18. ↑ Paul M. Sharp; George M. Shaw; Beatrice H. Hahn (April 2005). "Simian Immunodeficiency Virus Infection of Chimpanzees". Journal of Virology. pp. 3891–3902.

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