WASHINGTON -- Pursuing the hunt for the origin of AIDS, researchers have found an HIV-like virus in a single chimpanzee in the wild for the first time -- and in a different part of Africa than they'd suspected.
This particular type of chimp in Tanzania could not be the source for human AIDS, because the viral strain the researchers found is too genetically different.
But now that they've proved virus testing can be successful in the jungle without disturbing the endangered species, the Alabama scientists are beginning the next key step: tracking different chimps in an even more remote part of Africa, where the virus is thought to have jumped from animals to man.
Scientists have long known nonhuman primates carry their own version of the AIDS virus. But so far, it has been found only in captive chimpanzees. No one knows how prevalent or geographically or genetically diverse the virus is in chimps in the wild.
"Study in the wild is a very difficult thing. You can't just walk in there and ask them for a blood sample," noted Dr. Beatrice Hahn of the University of Alabama at Birmingham, explaining why this first study didn't start with the prime suspects.
Her study appears in Friday's edition of the journal Science.
The report is important because it proves Hahn's team developed "a very good way to, without invading or disturbing ecologically, study the evolution of the virus in this species," said Dr. Anthony Fauci, the National Institutes of Health's leading AIDS expert. "It's part of the big picture of really tracking down the origin."
"To find this virus for the first time in the wild opens a window of opportunity," added Hahn's co-author, George Shaw of the Howard Hughes Medical Institute.
Many scientists believe HIV, the virus that causes AIDS, probably originates from SIVcpz, a strain of simian immunodeficiency virus, found in a subspecies of chimpanzee from west-central Africa.
Hoping to bolster that theory, Hahn's research team developed a highly sensitive test to check urine and fecal samples for antibodies against SIV, and learned to cull SIV genetic material from fecal samples.
They enlisted help from primatologists, including Jane Goodall, who have extensively monitored chimp colonies in Tanzania, Uganda and the Ivory Coast. The primatologists can identify these chimps by sight, meaning Hahn would know exactly which animal had SIV if any samples proved positive.
Of 58 animals tested, only one had SIVcpz, a healthy 23-year-old male in the Goodall colony in Tanzania. That's farther east than tests on captive chimps had led scientists to believe the virus extended.
But this animal's strain was so genetically different that it rules out east African chimps as HIV's source, Hahn concluded.
Captive animals that harbor the most HIV-like virus are a subspecies from countries farther west, Gabon and Cameroon. There, primatologists haven't done colony studies like Goodall's -- it's hard to catch even a glimpse of the animals. So now, biologists are surveying wild chimp populations by counting fecal samples that they will share with Hahn for SIV testing. Finding the virus in those animals would bolster the AIDS origin theory.
Still, the Tanzanian find itself is important, because the animal's viral strain clearly isn't very virulent -- none of his sexual partners is infected, Hahn said. By studying why, maybe "we can get some clues that will help us combat HIV better in humans," she said.
Brainerd Dispatch ©2013. All Rights Reserved.