Researchers Trace Origin of HIV to Chimps That Ate Monkeys Infected With Two Strains of Similar Simian Virus
Simian immunodeficiency virus, the simian precursor to HIV, was created in chimpanzees when the primates killed and ate two types of monkeys -- red-capped mangabeys and greater spot-nosed guenons -- each infected with a different but similar simian virus, according to a study published in today's issue of the journal Science, the New York Times reports. Researchers from the University of Nottingham in England, the University of Alabama at Birmingham, Duke University, Tulane University and the University of Montpelier in France sequenced the genes of 30 monkey species and compiled "family trees" in order to determine which strains of SIV were most closely related to the strain found in chimpanzees, the primate from which humans are believed to have first contracted the HIV-like virus. The genetic code from one segment of the greater spot-nosed guenons' strain of SIV was most closely related to the same code in chimp SIV, while the virus from the mangabey was most closely related to chimp SIV in another genetic segment (McNeil, New York Times, 6/13). Based on the findings, the researchers predict that the chimpanzees acquired these viruses in much the same way that humans are thought to have acquired it -- through cuts acquired while killing the monkeys for food. According to the researchers, the chimpanzee would have to have been simultaneously infected with both viruses in order for the two strains of the monkey SIV to mix -- a situation likely to happen only through predation (Brown, Washington Post, 6/13).
While it is thought that SIV crossed over to humans sometime between 1910 and 1950, there is no way of knowing when the monkey viruses infected and recombined in chimps, according to the researchers. "It could be hundreds of years ago or tens of thousands of years ago," Dr. Beatrice Hahn, one of the study's authors said. The researchers hypothesize that because the virus is found in chimp subspecies in central Africa but not in the west African subspecies, it failed to spread to all chimp groups before the species diversified, suggesting that the virus is "relatively new," according to the Times (New York Times, 6/13). The geographic location of the chimp subspecies infected with SIV also gives credence to the researchers' overall theory, because the SIV-infected chimps occupy the same regions of Africa occupied by both the mangabeys and the guenons (Washington Post, 6/13).
Monkeys and chimps both represent a "reservoir of SIV viruses" that could, in theory, be spread to humans, possibly forming new types of immunodeficiency disease, Frederic Bibollet-Ruche, one of the study's authors said, according to the AP/Los Angeles Times. "[I]t is not such a good idea to hunt and eat monkeys. There is a risk for humans to come into contact" with new forms of HIV-like viruses, Bibollet-Ruche said (AP/Los Angeles Times, 6/13). Despite evidence that butchering and eating "bush meat," including chimpanzees and other non-human primates, started the HIV/AIDS epidemic, the practice is still widespread in some parts of Africa, according to the Philadelphia Inquirer. The researchers also note that the study shows the ease with which viruses can transfer to other species under natural circumstances, an issue that has gained increased attention recently in light of recent epidemics that originated in other species, including hantavirus, monkeypox and severe acute respiratory syndrome, or SARS. "Humans are now invading areas in large numbers where they hadn't gone before, and are likely to get in contact with animal populations," Roger Pomerantz, chief of the Division of Infectious Diseases at the Thomas Jefferson University Hospital in Philadelphia, said. Such increased contact with other species and the increased migration and interaction among populations have created "ripe" conditions for the spread of diseases, according to the Philadelphia Inquirer (Flam, Philadelphia Inquirer).