Genetic evidence confirmed that the HIV-1 virus originated in wild chimpanzees.

    LOS ANGELES, May 25 (Xinhua) -- Genetic evidence from chimpanzee feces from the forest floors of Cameroon has confirmed that the HIV-1 virus, the cause of human AIDS, originated in wild chimpanzee populations, scientists reported on Thursday.

    In a study published in the May 25 issue of the online edition of the journal Science, scientists from the U.S., Cameroon and Europe said they had found the ancestry of HIV by tracing genetic fragments in fecal samples of wild-living chimpanzees in west central Africa.

    Together with earlier studies, these findings provided for the first time a clear picture of the origin of HIV-1 and the seeds of the AIDS pandemic, according to the research team led by Beatrice Hahn at the University of Alabama.

    Scientists have long suspected that a virus most closely related to HIV-1, a simian immunodeficiency virus (SIV), could be an ancestor of HIV-1. But the SIV had only been found in captive chimpanzees before, shaking the hypothesis that the SIV could have evolved into HIV-1 in the wild.

    In this new study, the researchers said they had detected SIV antibodies and nucleic acids in hundreds of fecal samples from wild-living chimpanzees that belong to subspecies Pan troglodytes troglodytes (P. t. troglodytes).

    According to the team, the SIV infection rates in some chimpanzee communities in southern Cameroon have reached 29 percent to 35 percent. The genetic similarity between SIV in chimpanzees and HIV in humans are "striking," the researchers said.

    That means, SIV, which has infected wild chimps for years, could have evolved into HIV after it came into contact with humans.

    "By sequence analysis of endemic SIVcpz strains, we could trace the origins of pandemic and nonpandemic HIV-1 to distinct, geographically isolated chimpanzee communities," the researchers wrote in the Science paper.

    "These findings establish P. t. troglodytes as the natural reservoir of HIV-1," they concluded.

    The researchers further indicated that one SIV strain, which infects red-capped mangabeys, may have jumped to chimpanzees in west-central Africa by cross-species transmission quite early.

    Now it has many strains, and some may further evolve in the vast areas of west central Africa into new viruses that will cause pandemics in humans just like HIV, the scientists warned.

    "Given the extensive genetic diversity and phylogeographic clustering of SIVcpz now recognized ... it is quite possible that still other SIVcpz lineages exist that could pose risks for human infection and prove problematic for HIV diagnostics and vaccines, "they wrote in the paper. Enditem