Two of the four known groups of human AIDS viruses originated in western lowland gorillas in Cameroon, according to a new study.
An international team of scientists from the Perelman School of Medicine at the University of Pennsylvania, the University of Montpellier, the University of Edinburgh, and colleagues conducted a comprehensive survey of simian immunodeficiency virus (SIV) infection in African gorillas.
HIV-1, the virus that causes AIDS, has jumped species to infect humans on at least four separate occasions, generating four HIV-1 lineages - groups M, N, O, and P.
Previous research from this team found that groups M and N originated in geographically distinct chimpanzee communities in southern Cameroon, but the origins of groups O and P remained uncertain.
The four cross-species transmissions have had very different outcomes in humans. Group M gave rise to the AIDS pandemic, infecting more than 40 million people worldwide by spreading across Africa and throughout the rest of the world.
Groups N and P, at the other extreme, have only been found in a few individuals from Cameroon.
However, group O, although not as widespread and prevalent as group M, has infected about 100,000 people in west central Africa.
The team screened fecal samples from western lowland gorillas, eastern lowland gorillas, and mountain gorillas in Cameroon, Gabon, the Democratic Republic of Congo, and Uganda for evidence of SIVgor infection.
They identified four field sites in southern Cameroon where western lowland gorillas harbour SIVgor.
"Viral sequencing revealed a high degree of genetic diversity among the different gorilla samples," said Beatrice Hahn, a professor of Medicine and Microbiology at Penn.
"Two of the gorilla virus lineages were particularly closely related to HIV-1 groups O and P. This told us that these two groups originated in western lowland gorillas," Hahn said.
"Understanding emerging disease origins is critical to gauge future human infection risks," said Martine Peeters from Montpellier.
"From this study and others that our team has conducted in the past it has become clear that both chimpanzees and gorillas harbour viruses that are capable of crossing the species barrier to humans and have the potential to cause major disease outbreaks," Peeters said.
The study is published in the Proceedings of the National Academy of Sciences.
