Simian immunodeficiency virus
Encyclopedia
Simian immunodeficiency virus (SIV), also known as African Green Monkey
virus and also as Monkey AIDS is a retrovirus
able to infect at least 33 species of African primates. 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.
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.
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 rhesus macaque
, the animal will develop simian AIDS (SAIDS). 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 human HIV infection turns into AIDS.
suffering from simian AIDS (SAIDS). 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).
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.
Beatrice Hahn of the University of Alabama at Birmingham
recently led a team of researchers to find 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.
The ICTVdB code of SIV is 61.0.6.5.003.
In 2010, researchers reported that SIV had infected monkeys in Bioko
for at least 32,000 years. Previously it was thought that SIV infection in monkeys had happened over the past few hundred years. Scientists estimated that it would take a similar amount of time before humans adapted naturally to HIV infection in the way monkeys in Africa have adapted to SIV and not suffer any harm from the infection.
Green Monkey
The green monkey , also known as the Callithrix monkey, is an Old World monkey with golden-green fur and pale hands and feet. The tip of the tail is golden yellow as are the backs of the thighs and cheek whiskers. It does not have a distinguishing band of fur on the brow, like other Chlorocebus...
virus and also as Monkey AIDS is a retrovirus
Retrovirus
A retrovirus is an RNA virus that is duplicated in a host cell using the reverse transcriptase enzyme to produce DNA from its RNA genome. The DNA is then incorporated into the host's genome by an integrase enzyme. The virus thereafter replicates as part of the host cell's DNA...
able to infect at least 33 species of African primates. Based on analysis of strains found in four species of monkeys
Old World monkey
The Old World monkeys or Cercopithecidae are a group of primates, falling in the superfamily Cercopithecoidea in the clade Catarrhini. The Old World monkeys are native to Africa and Asia today, inhabiting a range of environments from tropical rain forest to savanna, shrubland and mountainous...
from Bioko Island
Bioko
Bioko is an island 32 km off the west coast of Africa, specifically Cameroon, in the Gulf of Guinea. It is the northernmost part of Equatorial Guinea with a population of 124,000 and an area of . It is volcanic with its highest peak the Pico Basile at .-Geography:Bioko has a total area of...
, 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.
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
Bushmeat
Bushmeat initially referred to the hunting of wild animals in West and Central Africa and is a calque from the French viande de brousse. Today the term is commonly used for meat of terrestrial wild animals, killed for subsistence or commercial purposes throughout the humid tropics of the Americas,...
in Africa.
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 rhesus macaque
Rhesus Macaque
The Rhesus macaque , also called the Rhesus monkey, is one of the best-known species of Old World monkeys. It is listed as Least Concern in the IUCN Red List of Threatened Species in view of its wide distribution, presumed large population, and its tolerance of a broad range of habitats...
, the animal will develop simian AIDS (SAIDS). 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 human HIV infection turns into AIDS.
History
Immunodeficiency resembling human AIDS was reported in captive monkeys in the United States beginning in 1983. SIV was isolated in 1985 from some of these animals, captive rhesus macaquesRhesus Macaque
The Rhesus macaque , also called the Rhesus monkey, is one of the best-known species of Old World monkeys. It is listed as Least Concern in the IUCN Red List of Threatened Species in view of its wide distribution, presumed large population, and its tolerance of a broad range of habitats...
suffering from simian AIDS (SAIDS). 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 TRIM5αTRIM5-alpha
Tripartite motif-containing protein 5 also known as RING finger protein 88 is a protein that in humans is encoded by the TRIM5 gene. The alpha isoform of this protein, TRIM5α, is a retrovirus restriction factor, which mediates species-specific, early block to retrovirus infection.TRIM5α is composed...
in humans and non-human primate species. This intracellular protein recognizes the capsid
Capsid
A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic...
of various retroviruses and blocks their reproduction. Other proteins such as APOBEC3G
APOBEC3G
APOBEC3G is a human enzyme encoded by the APOBEC3G gene that belongs to the APOBEC superfamily of proteins. This family of proteins has been suggested to play an important role in innate anti-viral immunity...
/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 research purposes.Beatrice Hahn of the University of Alabama at Birmingham
University of Alabama at Birmingham
The University of Alabama at Birmingham is a public university in Birmingham in the U.S. state of Alabama. Developing from an extension center established in 1936, the institution became an autonomous institution in 1969 and is today one of three institutions in the University of Alabama System...
recently led a team of researchers to find 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.
The ICTVdB code of SIV is 61.0.6.5.003.
In 2010, researchers reported that SIV had infected monkeys in Bioko
Bioko
Bioko is an island 32 km off the west coast of Africa, specifically Cameroon, in the Gulf of Guinea. It is the northernmost part of Equatorial Guinea with a population of 124,000 and an area of . It is volcanic with its highest peak the Pico Basile at .-Geography:Bioko has a total area of...
for at least 32,000 years. Previously it was thought that SIV infection in monkeys had happened over the past few hundred years. Scientists estimated that it would take a similar amount of time before humans adapted naturally to HIV infection in the way monkeys in Africa have adapted to SIV and not suffer any harm from the infection.
See also
- Origin of AIDS
- OPV AIDS hypothesisOPV AIDS hypothesisThe oral polio vaccine AIDS hypothesis argues that the AIDS pandemic originated from live polio vaccines prepared in chimpanzee tissue cultures and then administered to up to one million Africans between 1957 and 1960 in experimental mass vaccination campaigns.Data from molecular biology and...
- eu-FEDS
- List of monkey viruses (and human transmissions)
External links
- Description of SIV, including links to subspecies and sequence data, from the International Committee on Taxonomy of VirusesInternational Committee on Taxonomy of VirusesThe International Committee on Taxonomy of Viruses is a committee which authorizes and organizes the taxonomic classification of viruses. They have developed a universal taxonomic scheme for viruses and aim to describe all the viruses of living organisms. Members of the committee are considered to...
- 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