The hot wax. A cache of ancient tissue samples from Kinshasa - stored in paraffin - including one from 1960 that was infected by HIV.
Dirk Teuwen
The second oldest specimen ever discovered HIV has postponed the date of the virus is passed from chimpanzees to humans more than 2 decades, according a new study. The study helps to clarify further how the AIDS epidemic began, and it reinforces the growing evidence that HIV does not spread easily to what cities have emerged in Central Africa.
The sample derived from a lymph node biopsy taken in 1960 from a 28 year-old woman in what is now Kinshasa, Democratic Republic of Congo. Researchers led by evolutionary biologist Michael Worobey of the University of Arizona, Tucson, blocks analyzed tissues from 27 patients between 1958 and 1960 as the University of Kinshasa had kept with some patient records. As noted Worobey, these patients had biopsies taken because they had mysterious ailments, including abnormalities of the lymph nodes, which are common in people with HIV. "You really could ask for a better cohort look for people who had HIV in Kinshasa," he said.
As the researchers describe in tomorrow's issue of Nature they isolated about 5% of the HIV genome lymph woman. A comparison with the oldest sample of HIV, also from Kinshasa and dates to 1959, found that they differed by about 12% in an overlap area. This led Worobey and his colleagues estimate that the two viruses had a common ancestor around 108, which means that HIV that triggered the current epidemic of AIDS rose from chimpanzees to humans before. The previous estimates dating the common ancestor about 1931.
Worobey and co-authors link the spread of HIV to the growth of Kinshasa and other cities in central Africa. They document that no city in the region had more than 10,000 inhabitants until 1910, supporting the longstanding theory that HIV needed this critical mass of people in urban areas to implement. "The virus is really struggling to ignite an epidemic" until authorized cities fast transmission, notes Worobey. He says this emphasizes that concerted prevention efforts today can stop local epidemics foothold.
Worobey, whose previous detailed studies on the spread of HIV from Africa to the United States and Europe, still hundreds of samples to analyze and is looking for more samples old. "People have not really tried to find these old samples," he said.
Beatrice Hahn, whose group at the University of Alabama, Birmingham, deduced previous estimates using modern samples HIV, applauds the hard work. "This was done just the way you want to do," said Hahn, who notes that a second lab has independently confirmed the sequence, which never happened with the sample 1959. "This looks to lean backwards to do it the right way."
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