URBANA Human immunodeficiency virus (HIV) may have affected humans for much longer than is currently believed. Alfred Roca, an assistant professor in the College of Agricultural, Consumer and Environmental Sciences at the University of Illinois, thinks that the genomes of an isolated West African human population provide important clues about how the disease has evolved.
HIV is thought to have originated from chimpanzees in central Africa that were infected with simian immunodeficiency virus (SIV), a retrovirus. "If you look at the diversity present across SIV in chimpanzees, it suggests that they have had it for tens of thousands of years," Roca said.
HIV-1 Type M, which accounts for 90 percent of human infections, is believed to have crossed the species barrier into human populations between 1884 and 1924. Roca said that it may have crossed much earlier and many times, selecting for genetic resistance in isolated rural populations while remaining undetected.
"Some of the scientific literature suggests that the persistence of HIV in humans required population densities typical of the larger cities that appeared in West Central Africa during the colonial era," he said.
Perhaps an even more important factor is that, before modern medicine and vaccinations, infectious diseases such as smallpox killed large numbers of people. People with compromised immune systems may have succumbed first, preventing the immunodeficiency virus from spreading.
If HIV crossed the species barrier many times, it is possible that selection favored protective genetic variants in the affected populations. Roca and his co-investigators looked for evidence of this selection in the Biaka genomes.
The Biaka are a human community that inhabits forests in the range of the chimpanzee subspecies believed to be the source of the current HIV pandemic. The researchers compared Biaka genomes with the genomes of four other African populations wh
|Contact: Susan Jongeneel|
University of Illinois College of Agricultural, Consumer and Environmental Sciences