This article from NYTimes.com
has been sent to you by snkeita@aol.com.
On creuse un petit peu encore dans la recherche de l'origine du virus du sida(HIV).Et pour le moment on reste "encore" en Afrique,...des homme qui ont mange des singes(chimpanzees)qui avaient devores d'autres singes.
Salaha Keita.
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Researchers Have New Theory on Origin of AIDS Virus
June 13, 2003
By DONALD G. McNEIL Jr.
Four years after arguing that humans probably got the AIDS
virus from butchering chimpanzees for food, the same
researchers say they have traced the origin back one step
further: to the monkeys that the chimpanzees ate.
They believe the simian precursor to the AIDS virus was
created in chimps that ate two kinds of monkeys with
different but related viruses, red-capped mangabeys and
spot-nosed guenons.
They made the deduction by sequencing the genes of the
simian immunodeficiency viruses in chimpanzees and 30
monkey species and then compiling "family trees" to see
which were most closely related.
The study, done jointly by researchers at the University of
Nottingham, the University of Alabama at Birmingham, Duke
University, Tulane University and the University of
Montpellier in France, appears today in the journal
Science.
The conclusion is important, said Dr. Beatrice Hahn, a
University of Alabama at Birmingham virologist and one of
the authors, "because it shows that chimpanzees acquired
their virus exactly the same way humans did, by hunting
bushmeat." Neither chimps nor monkeys get sick from it.
Unlike the other great apes, chimpanzees are formidable
hunters. Troops of males often work together; some chase
monkeys through forest canopies while others wait in nearby
trees to swat their prey off branches, and yet others
follow on the ground, leaping on fallen monkeys and
battering them to death.
Hunting males tear their catches limb from limb and eat
them on the spot, share the carcasses or trade them to
females for sex, so blood-to-blood contact from "open cuts
or chomping on bones" is easy to imagine, one researcher
said.
The prevailing theory about the origin of H.I.V. is that
somewhere in central Africa, probably between 1910 and
1950, a chimpanzee hunter picked up its virus by cutting
himself while butchering a carcass. The simian virus then
mutated into H.I.V. and spread among humans, mostly through
sex.
However, "a lot of people just don't buy this and say it
was polio vaccine or dirty needles or tattooing or crazy
tribal practices," Dr. Hahn said. "This shows the flaw in
their argument."
Experts not connected with the study said they found it
plausible. Dr. Ronald Desrosiers, a professor of genetics
at Harvard Medical School, said it "looks like it makes
sense" and demonstrates how easily diseases transfer
between species.
Another expert, Edward Hooper, argued in a 1999 book,
<object.title class="Movie" idsrc="nyt_ttl"
value="108090">"The River"</object.title> (Little, Brown),
that a chimpanzee virus passed into humans when an
experimental oral polio vaccine was grown in a medium
containing chimpanzee cells and used in parts of the former
Belgian Congo in 1957 to 1960. He called the study
"reasonably plausible, though based on limited data."
"I have no problem with the idea that chimps got it by
eating other monkeys," he said.
Scientists believe two monkey viruses were involved because
the virus from guenons (Cercopithecus nictitans) was
closest in the part of the genome that contains the code
for the virus's protein envelope, while the virus from the
mangabey (Cercocebus torquatus) was closest in a different
segment.
There is no way to know when the two viruses merged inside
one chimpanzee. "It could have been hundreds of years ago
or tens of thousands of years ago," Dr. Hahn said.
Chimp virus has been found in two subspecies found in
central Africa known as troglodytes and schweinfurthii, but
not yet in the westernmost subspecies, known as verus, nor
in a related species found south of the Congo River, the
hairier bonobo or pygmy chimpanzee.
The virus's failure to spread to all chimpanzees before
they diversified into subspecies suggests that it is
relatively new, researchers said. Subspecies have been
separated for eons by large rivers like the Congo and the
Ubangi, since chimps cannot cross water.
A related study of the virus in wild chimpanzees by many of
the same authors, scheduled to appear in the Journal of
Virology next month, shows that it is much less common than
in monkeys and the rate varies from region to region and
troop to troop. None of the chimps studied in Uganda's
Kibale National Park were infected. An estimated 13 percent
of those in Tanzania's Gombe National Park were.
By contrast, 50 to 90 percent of most adult monkeys are
infected with their versions, said Dr. Paul M. Sharp, a
professor of genetics at the University of Nottingham.
Because wild chimpanzees, which grow nearly six feet tall,
can easily kill humans, getting blood samples is dangerous,
so researchers watch chimps closely enough to be able to
test their feces and urine.
It is still unclear exactly how chimpanzees infect each
other and why the disease isn't more rampant among them,
since they have many sexual partners and fight frequently,
often biting each other, which in rare human cases has
passed the virus.
Nursing is surely one route, Dr. Hahn said, because some
chimps captured in infancy are infected.
http://www.nytimes.com/2003/06/13/science/13CHIM.html?ex=1056919713&ei=1&en=bd758ddd17dc7877
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