Discovery of a simian immunodeficiency virus infection in wild gorillas

In 2005, 40.3 million people in the world, including 25.8 million in Sub-Saharan Africa, were living with HIV. The question of the origin of HIV-1, responsible for the AIDS pandemic, has been stimulating the scientific community for many years.

Some months ago, the team of Martine Peeters, director of research at IRD, and Eric Delaporte, director of the mixed research unit UMR 145 jointly involving the IRD and the University of Montpellier 1, showed the chimpanzee subspecies living in the Congo Basin to be the reservoir of HIV-1 virus group M, the source of the world pandemic and that of another, very rare variant, HIV-1 group N. However, the reservoir of the third HIV-1 group, group O which infects humans, remained unidentified up to now.

This team announces, in an article in the journal Nature, the discovery of a simian immunodeficiency virus (SIV) infection in wild gorillas. Samples of faeces collected from different communities of gorillas found in the remotest areas of the Cameroon tropical forest were found to contain antibodies against this virus, called SIVgor. The genetic characteristics of the virus were present again in three gorillas living more than 400 km apart. Phylogenetic analysis of SIVgor showed it to be related to HIV-1 group O found in humans, essentially in Cameroon and in neighbouring countries.

This discovery of an HIV-1 related virus in wild gorillas does not, however, call into question the fact that chimpanzees are the primary reservoir of SIV/HIV viruses that crop up again in gorillas and in humans. As Martine Peeters of the IRD says, "the viruses of groups M and N are, very clearly, the consequence of inter-species transmission from chimpanzee to humans, whereas the origin of HIV-1 group O is less apparent. It cannot be excluded that chimpanzees infected by HIV-1 group O might have contaminated humans and the gorilla independently, or that the gorilla, having been contaminated by the chimpanzee, might have contaminated humans".

This work thus opens up a Pandora's box on the questions and speculations concerning the ability of these viruses to cross over from one species to another. The main challenges facing these teams for future work will be determination of the prevalence, the geographical distribution and biology of SIV infections in these great apes, not forgetting the question of how the gorillas were contaminated. This last point remains a mystery,considered as rare.