Discover Top Posts Tagged with #green monkey

History of HIV/AIDS

Left to right: the African green monkey, source of SIV; the sooty mangabey, source of HIV-2; and the chimpanzee, source of HIV-1

AIDS is caused by a human immunodeficiency virus (HIV), which originated in non-human primates in Central and West Africa. While various sub-groups of the virus acquired human infectivity at different times, the present pandemic had its origins in the emergence of one specific strain – HIV-1 subgroup M – in Léopoldville in the Belgian Congo (now Kinshasa in the Democratic Republic of the Congo) in the 1920s.[1]

There are two types of HIV: HIV-1 and HIV-2. HIV-1 is more virulent, more easily transmitted, and it is the cause of the vast majority of HIV infections globally.[2] The pandemic strain of HIV-1 is closely related to a virus found in chimpanzees of the subspecies Pan troglodytes troglodytes, which live in the forests of the Central African nations of Cameroon, Equatorial Guinea, Gabon, the Republic of the Congo, and the Central African Republic. HIV-2 is less transmissible and is largely confined to West Africa, along with its closest relative, a virus of the sooty mangabey (Cercocebus atys atys), an Old World monkey inhabiting southern Senegal, Guinea-Bissau, Guinea, Sierra Leone, Liberia, and western Ivory Coast.[2][3]

Transmission from non-humans to humans

Left to right: the African green monkey, source of SIV; the sooty mangabey, source of HIV-2; and the chimpanzee, source of HIV-1

Research in this area is conducted using molecular phylogenetics, comparing viral genomic sequences to determine relatedness.

HIV-1 from chimpanzees and gorillas to humans

Scientists generally accept that the known strains (or groups) of HIV-1 are most closely related to the simian immunodeficiency viruses (SIVs) endemic in wild ape populations of West Central African forests.[4][5] In particular, each of the known HIV-1 strains is either closely related to the SIV that infects the chimpanzee subspecies Pan troglodytes troglodytes (SIVcpz) or closely related to the SIV that infects western lowland gorillas, called SIVgor.[6][7][8][9][10][11] The pandemic HIV-1 strain (group M or Main) and a rare strain found only in a few Cameroonian people (group N) are clearly derived from SIVcpz strains endemic in Pan troglodytes troglodytes chimpanzee populations living in Cameroon.[6] Another very rare HIV-1 strain (group P) is clearly derived from SIVgor strains of Cameroon.[9] Finally, the primate ancestor of HIV-1 group O, a strain infecting 100,000 people mostly from Cameroon but also from neighbouring countries, was confirmed in 2006 to be SIVgor.[8] The pandemic HIV-1 group M is most closely related to the SIVcpz collected from the southeastern rain forests of Cameroon (modern East Province) near the Sangha River.[6] Thus, this region is presumably where the virus was first transmitted from chimpanzees to humans. However, reviews of the epidemiological evidence of early HIV-1 infection in stored blood samples, and of old cases of AIDS in Central Africa, have led many scientists to believe that HIV-1 group M early human centre was probably not in Cameroon, but rather further south in the Democratic Republic of the Congo (then the Belgian Congo), more probably in its capital city, Kinshasa (formerly Léopoldville).[6][12][13]

Using HIV-1 sequences preserved in human biological samples along with estimates of viral mutation rates, scientists calculate that the jump from chimpanzee to human probably happened during the late 19th or early 20th century, a time of rapid urbanisation and colonisation in equatorial Africa. Exactly when the zoonosis occurred is not known. Some molecular dating studies suggest that HIV-1 group M had its most recent common ancestor (MRCA) (that is, started to spread in the human population) in the early 20th century, probably between 1915 and 1941.[14][15][16] A study published in 2008, analyzing viral sequences recovered from a biopsy made in Kinshasa, in 1960, along with previously known sequences, suggested a common ancestor between 1873 and 1933 (with central estimates varying between 1902 and 1921).[17] Genetic recombination had earlier been thought to "seriously confound" such phylogenetic analysis, but later "work has suggested that recombination is not likely to systematically bias [results]", although recombination is "expected to increase variance".[17] The results of a 2008 phylogenetics study support the later work and indicate that HIV evolves "fairly reliably".[17][18] Further research was hindered due to the primates being critically endangered. Sample analyses resulted in little data due to the rarity of experimental material. The researchers, however, were able to hypothesize a phylogeny from the gathered data. They were also able to use the molecular clock of a specific strain of HIV to determine the initial date of transmission, which is estimated to be around 1915–1931.[19]

HIV-2 from sooty mangabeys to humans

#green monkey

Trending Tags

Recently Viewed Tags

#green monkey