The strain of the virus responsible for almost all cases of AIDS appeared in the 1930s, say scientists who have used a "clock molecular "to date the origin of HIV. The discovery, published in the June 9 issue of Science , casts doubt on the idea that the controversial vaccine against the AIDS pandemic contaminated polio sown in the late 1950s
the origin of AIDS is much clearer today than it was in the early 1980s, when the new disease blindsided the scientific establishment. Virologists have identified the chimpanzee virus that likely led to HIV, while epidemiologists searched in old and forgotten samples of medical records to identify early cases. Yet traces of direct evidence stops with HIV positive blood sample drawn in 1959 in what is now the Democratic Republic of Congo. How and when the chimpanzee virus entered the human remains uncertain.
To look further into the murky past of HIV, theoretical biologist Bette Korber of Los Alamos National Laboratory in New Mexico and his colleagues used a statistical model to the clock of the evolution of the gene of HIV of the envelope, which encodes a protein spines protrude from the surface of the virus. With the help of a supercomputer, the Korber group compared 159 gene sequences from the virus in the so-called Group M, which causes most cases of AIDS worldwide. Assuming that the differences between genes accumulate at a constant rate, the researchers calculated that the common ancestor of all virus group M occurred between 1915 and 1941 - most likely in 1931. They believe that the virus had already jumped to humans at present; invasion later, he would have several viral strains entrants before spreading from person to person. - A highly unlikely scenario called Korber
The study impresses other scientists in the field. "It is the best by a long way analysis has been done in this area," says molecular evolutionist Paul Sharp of Nottingham University in the UK If confirmed, early date would crush the hypothesis. - recently described in a book called river (Science, November 12, 1999, p 1305.) - That the AIDS pandemic was triggered by an oral vaccine against polio contaminated inadvertently by the chimpanzee virus.
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