Monday, February 1, 1999 Published at 13:57 GMT
Aids origin 'discovered'
Chimps do not get sick from the virus
The origin of the main HIV virus that causes Aids in humans has been discovered by an international team of scientists.
Infected chimps do not develop Aids and it may now be possible to learn why. This would greatly help efforts to prevent and treat the disease in humans.
The team said that genetic tests show the main human virus, HIV-1, is closely related to a virus that infects chimps but does not make them sick.
Dr Beatrice Hahn of the University of Alabama and colleagues made the discovery when analysing frozen blood and tissue samples from a lab chimp named Marilyn which died in 1985. The genetic tests were not available at that time.
"She had never been used in Aids research and had not received human blood products after 1969," said Dr Hahn.
In the early days of Aids research, dozens of chimps were deliberately infected with the HIV virus to see if they developed the disease. To the surprise of scientists, they did not, despite sharing 98% of their genetic material with humans.
"This is an important finding with significant potential," said Dr Anthony Fauci of the US National Institute of Allergies and Infectious Diseases (NIAID), which helped fund the study.
"This may allow us to study infected chimpanzees in the wild to find out why these animals don't get sick. This information that may help us better protect humans from developing Aids."
It is not yet known whether the chimps do not develop Aids because of their genetic differences with humans or because their immune systems deal better with the virus. The answer will determine whether studying the chimps could lead to better treatments or better vaccines for Aids.
The sub-species population is estimated at 80,000 but the annual number killed is thought to be thousands, putting these chimps on the "brink of extinction".
There is evidence that HIV may have transferred to humans throughout history, but only became an epidemic in the 20th century. The reasons for this are increased sexual promiscuity, civil unrest and movement of people to cities, according to Dr Hahn.
Last year, researchers said they had found the first known case of Aids - in a Bantu man who died in 1959 in the Belgian Congo, now the Democratic Republic of Congo and the home of the sub-species of chimps.