Many macaques carry a protein that helps to defend against viruses like HIV. Credit: Punchstock

An important antiviral protein, which targets the family of viruses that includes HIV, seems to have evolved twice in nonhuman primates, researchers have found, with one of the versions evolving somewhere between 5 million and 10 million years ago. The results suggest that these viruses played an important role in primate evolution.

New World owl monkeys (Aotus) were previously known to have a protein, called TRIMCyp, that fends off HIV-1 and other members of the lentivirus family. Recently, five research groups have independently reported finding a similar protein in several species of Old World primate1,2,3,4,5. There are sufficient differences between the proteins of New World and Old World monkeys to make researchers think they evolved independently.

This really emphasizes how important retroviruses are to the evolution of nonhuman primates. Nathan Wolfe

In Old World monkeys, TRIMCyp has so far been found in pigtailed macaques (Macaca nemestrina), long-tailed macaques (M. fascicularis) and some rhesus macaques (M. mulatta). These macaques diverged from a common ancestor about 5 million years ago, so it is likely that the protein is at least that old.

In the most recent study, published in PLoS Pathogens, Welkin Johnson of Harvard Medical School reports that the protein is absent from a related Old World primate, the sooty mangabey (Cercocebus atys). This primate split from the macaque lineage about 10 million years ago1.

“The implication is that there were primate lentiviral epidemics five to ten million years ago,” Johnson says.

Criss cross

Primate retroviruses have demonstrated their ability to enter into the human population and cause pandemics on many occassions. Some researchers estimate that HIV-1 has crossed from chimpanzees into humans six or more times.

The age of the primate lentivirus family has been debated, with some believing it is only a few thousand years old, says Michael Emerman, who studies viral evolution at the Fred Hutchinson Cancer Research Center in Seattle, Washington. The new findings support the hypothesis that the epidemics have been plaguing primates for millions of years, he says.

The convergent evolution of TRIMCyp demonstrates the importance of retroviral defences during primate evolution, says Nathan Wolfe, an infectious disease researcher at the University of California, Los Angeles. “When you see evidence of convergent evolution in nature, it’s generally the sign of a pretty powerful selective force,” he says. “This really emphasizes how important retroviruses are to the evolution of nonhuman primates.”