Source of AIDS virus definitely African chimps, say scientists
TWENTY-FIVE years after the first AIDS cases were confirmed, the origin of the virus that causes the disease has finally been traced to wild chimpanzees living in the forests of south-east Cameroon.
Scientists researching the evolutionary history of the deadly virus discovered that the chimp version, SIVcpz, which is found among animals living south of the Sanaga River, bore a striking similarity to HIV-1, the strain which caused a pandemic of AIDS among humans.
It is thought that someone in rural Cameroon was bitten by a chimp or was cut while butchering one, and became infected with the ape virus before passing it to someone else.
The Sanaga River has long been a commercial waterway for transporting the likes of hardwood and ivory to more urban areas, and, eventually, an infected person made it to Kinshasa, in the nearby Congo, where what is now known to be the first recorded case of the virus in humans appeared.
Professor Paul Sharp, an evolutionary geneticist at Nottingham University, who worked on the project with colleagues from the United States and France, said: "We are interested in how the virus has evolved. In many ways, we think this is the last piece in the puzzle as to where the virus came from.
"One reason for being interested in chimps is they don't get sick and, obviously, they are very closely related to us."
He said it was thought that the animals simply lived with the presence of the virus in their immune cells - it is only when the body tries to attack them that AIDS occurs.
Prof Sharp said: "The virus infects the cells of the immune system. If you destroy the cells that contain this virus, you destroy your own cells - AIDS is caused by a lack of immune cells.
"If you could somehow ignore them, leave them alone, you wouldn't get AIDS, and eventually the virus might destroy the cell itself. As long as the virus isn't too busy, it's not a problem."
Writing in today's edition of the journal Science, researchers said that up to 35 per cent of chimps in some communities had been infected with SIV, but in others there was no sign of the disease at all.
Despite the close genetic similarity between chimps and humans, SIV does not cause an AIDS-like illness. It is hoped further study will reveal why - and whether this might help to treat people with HIV.
It is thought HIV-1 originated about 75 years ago. However, the first human known to be infected with the virus was a man from Kinshasa, who had his blood stored in 1959 as part of a medical study, decades before scientists knew HIV even existed.
Dr Beatrice Hahn, of Alabama University in the US, who is also a member of the research team, said: "How many different transmission events occurred between that initial hunter and this virus making it to Kinshasa, I don't know.
"It could have been one, it could have been ten, it could have been 100. Eventually, it ended up in an urban area, and that's where it really got going."
She said the researchers, who collected some 1,300 samples of chimp faeces for genetic testing, were convinced that the strain of SIV found in south-eastern Cameroon was the origin of HIV.
source
TWENTY-FIVE years after the first AIDS cases were confirmed, the origin of the virus that causes the disease has finally been traced to wild chimpanzees living in the forests of south-east Cameroon.
Scientists researching the evolutionary history of the deadly virus discovered that the chimp version, SIVcpz, which is found among animals living south of the Sanaga River, bore a striking similarity to HIV-1, the strain which caused a pandemic of AIDS among humans.
It is thought that someone in rural Cameroon was bitten by a chimp or was cut while butchering one, and became infected with the ape virus before passing it to someone else.
The Sanaga River has long been a commercial waterway for transporting the likes of hardwood and ivory to more urban areas, and, eventually, an infected person made it to Kinshasa, in the nearby Congo, where what is now known to be the first recorded case of the virus in humans appeared.
Professor Paul Sharp, an evolutionary geneticist at Nottingham University, who worked on the project with colleagues from the United States and France, said: "We are interested in how the virus has evolved. In many ways, we think this is the last piece in the puzzle as to where the virus came from.
"One reason for being interested in chimps is they don't get sick and, obviously, they are very closely related to us."
He said it was thought that the animals simply lived with the presence of the virus in their immune cells - it is only when the body tries to attack them that AIDS occurs.
Prof Sharp said: "The virus infects the cells of the immune system. If you destroy the cells that contain this virus, you destroy your own cells - AIDS is caused by a lack of immune cells.
"If you could somehow ignore them, leave them alone, you wouldn't get AIDS, and eventually the virus might destroy the cell itself. As long as the virus isn't too busy, it's not a problem."
Writing in today's edition of the journal Science, researchers said that up to 35 per cent of chimps in some communities had been infected with SIV, but in others there was no sign of the disease at all.
Despite the close genetic similarity between chimps and humans, SIV does not cause an AIDS-like illness. It is hoped further study will reveal why - and whether this might help to treat people with HIV.
It is thought HIV-1 originated about 75 years ago. However, the first human known to be infected with the virus was a man from Kinshasa, who had his blood stored in 1959 as part of a medical study, decades before scientists knew HIV even existed.
Dr Beatrice Hahn, of Alabama University in the US, who is also a member of the research team, said: "How many different transmission events occurred between that initial hunter and this virus making it to Kinshasa, I don't know.
"It could have been one, it could have been ten, it could have been 100. Eventually, it ended up in an urban area, and that's where it really got going."
She said the researchers, who collected some 1,300 samples of chimp faeces for genetic testing, were convinced that the strain of SIV found in south-eastern Cameroon was the origin of HIV.
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