Two viruses from different monkey species were the original parents of HIV, according to new research. A study published in Science suggests that two monkey viruses cross-infected chimpanzees and formed the strain of the simian immunodeficiency virus (SIV) that is believed to be the precursor of HIV.

Most HIV/AIDS researchers believe that the virus that causes AIDS originated in chimpanzees and made the jump to humans in the 1930s on exposure to primate blood through hunting and preparing meat. But until now the source of the chimpanzee version was unknown.

An international team of researchers led by Paul Sharp of the University of Nottingham, United Kingdom, compared the genetic sequences of viruses and found that the chimpanzee virus is a cross between SIV strains found in two types of monkey — red-capped mangabeys and greater spot-nosed monkeys — that are eaten by chimpanzees.

The discovery has led researchers to speculate that chimps may still harbour other HIV-like viruses that could jump to humans. "It will be important to examine whether chimpanzee predation on smaller monkeys has led to additional SIV acquisitions, and possibly coinfection and recombination with [the strain of SIV that caused AIDS in humans], and whether the resulting chimpanzee-adapted SIVs are more likely to infect humans," they conclude.

Link to research paper in Science

Reference: Science 300, 1713 (2003)

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