Scientists have found two chimpanzees infected with a virus very similar to the human AIDS virus, providing the most valuable clue yet in the search for the mysterious origin of the deadly disease, it was reported Wednesday.
French researchers said they detected a virus resembling the human immunodeficiency virus or HIV in two wild, baby chimpanzees captured in Gabon, an African nation that straddles the equator.HIV, also known as HIV-1, is the major cause of acquired immune deficiency syndrome worldwide. Before the latest work, no close viral relative to HIV-1 had been found in animals.
Since the AIDS epidemic first surfaced in 1981, scientists have been puzzled by the origin of the deadly AIDS viruses. The new virus may prove to be a "missing link" between AIDS-like primate viruses and those that infect humans, a U.S. researcher said.
HIV-2, another AIDS-causing virus discovered several years after HIV-1, is related to HIV-1, but afflicts far fewer people. Evidence seems to indicate HIV-2, which is most prevalent among West Africans, probably crossed over into humans from West African monkeys frequently infected with a simian immunodeficiency virus or SIV. SIV is very similar to HIV-2 but is only a distant cousin of HIV-1.
Scientists gauge the similarity between viruses by determining how closely the viruses' genetic makeup resemble one another.
The virus found in the Gabon chimps, which researchers suggest naming chimpanzee immunodeficiency virus or CIV, is more closely related to HIV-1 than HIV-2 but varies too much to simply be considered a strain of HIV-1, Simon Wain-Hobson of the Pasteur Institute and his colleagues reported in the journal Nature.
Although the findings "provide no final solution to the mystery" of where HIV-1 came from, they offer "the most significant clues to date" in piecing together the scientific puzzle, U.S. researcher Ronald Derosiers wrote in an editorial accompanying the study.
The newly discovered chimpanzee virus may prove to be a "missing link" between the SIV-HIV-2 viral clan and HIV-1, said Derosiers of the New England Regional Primate Research Center in Southborough, Mass.
But Derosiers emphasized many questions still remain.
The findings do not solve the controversy over whether HIV-1 entered humans relatively recently from animals like chimps, or whether HIV-1 has long infected humans at low rates and the epidemic that emerged in the 1980s stemmed from modern behaviors like intravenous drug use and international travel.
"I wouldn't venture which is most likely at this point," Derosiers said.