HIV-AIDS did not come from oral polio
vaccine contaminated with chimpanzee
virus, reports a research team led by a
University of Arizona evolutionary biologist.
Belief that polio vaccine can spread AIDS has hampered the World Health Organization's efforts to stamp out polio. In Nigeria, several states recently banned use of the vaccine. Nigeria now has the highest number of polio cases in the world.
Although scientists agree that HIV comes from a chimpanzee simian immunodeficiency virus (SIV) that infected humans, when and how SIV jumped the species barrier has not been definitively determined.
The researchers found and sequenced genetic material from a new strain of SIV present in wild chimpanzees in the Kisangani region of the Democratic Republic of Congo (DRC).
The new SIV is not the one from which HIV-1, the virus responsible for the human AIDS pandemic, originated. The research shows that the new SIV resides on a different part of the SIV family tree.
One theory about the origin of HIV-AIDS alleges that tissues from chimps from the vicinity of Kisangani were used in preparing oral polio vaccine, thus letting the vaccine be contaminated by SIV.
"We found a new simian immunodeficiency virus, SIVcpzDRC1," said Michael Worobey, an assistant professor of ecology and evolutionary biology at the University of Arizona in Tucson. "It's a new variant of SIV, and it's not closely related to HIV-1." Finding the new strain of SIV in chimpanzees near Kisangani shows that HIV-1 did not originate from polio vaccines that were tested in that area in the 1950s.
The team's research article will be published in the April 22 issue of the journal Nature.
Worobey's coauthors are Beatrice H. Hahn, George M. Shaw, Mario L. Santiago, and Brandon F. Keele of the University of Alabama in Birmingham, Jean-Bosco N. Ndjango, Bernard L. Labama and Benoît D. Dhed'a of the University of Kisangani in the Democratic Republic of Congo, Jeffrey B. Joy of Simon Fraser University in Burnaby, British Columbia, and Andrew Rambaut of the University of Oxford and Paul M. Sharp of the University of Nottingham in England.
The research was funded in part by the Wellcome Trust, St. John's College Oxford, the Rhodes Trust, the Royal Society, the National Institutes of Health and the Howard Hughes Medical Institute.
Previous studies have linked all variants of HIV to the chimpanzee subspecies native to the countries to the west of the Democratic Republic of Congo (DRC).
However, genetic diversity of the pandemic strain of HIV, known as HIV-1 group M, is highest in the DRC.
So the DRC is an important place to look for clues about the origins of AIDS and specifically to test the oral polio vaccine/AIDS theory.
"I wanted not just to test the OPV/AIDS theory, but also to collect fundamental data from a crucial area," Worobey said.
Easier said than done.
Although recent technological advances have made it possible to test feces for RNA, the genetic material of SIV and HIV, one still has to collect the specimens.
Despite civil war in the region, Worobey traveled to the Democratic Republic of Congo in 2000 and in 2003 to collect fresh samples from wild chimps in the Kisangani area.
"The fresher, the better," he said. "Basically you want to pick it up the same morning they let it go."
He worked with a team of hunters that track the chimps at night using their calls. The team carefully stored small samples of feces in little screw-capped vials filled with a preservative.