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Genetic adaptation to SIV protects Vervet monkeys from immunodeficiency

Wild vervet monkeys (genus Chlorocebus) are frequently infected by the Simian Immunodeficiency Virus (SIV), a close relative of HIV. However, they do not progress to AIDS. A scientific study published today in the journal Nature Genetics suggests that vervets have long co-evolved with SIV and acquired genetic adaptations that protect them from immunodeficiency.


The international research team led by Dr. Magnus Nordborg, scientific director of the Gregor Mendel Institute of the Austrian Academy of Sciences in Vienna, and his former postdoc Dr. Hannes Svardal, sequenced DNA from 163 vervet monkeys from nine African countries and three Caribbean islands, where vervet monkeys were introduced in the colonial era, making this the geographically most extensive study of genetic diversity in a non-human primate.

The study entitled “Ancient Hybridization and Strong Adaptation to Viruses Across African Vervet Monkey Populations” first clarified the genetic relationships between vervet monkey species across Africa and then showed that evolutionary processes that gave rise to the different species were complex, involving periods of separation and secondary contact. According to Dr. Nordborg “This analysis reinforces many of our evolving hypotheses on species formation that have arisen from our work in plants – speciation is a complex process involving periods of genetic isolation followed by exchange of genetic material.”

The authors further examined the relationships of the vervet species with the genome sequences of the SIV strains that infect them, and found evidence that –  despite contact between species – SIV strains did not readily jump between hosts. Thus, the different vervet species had several hundred thousand years to co-evolve with their specific SIV strains. Svardal and colleagues therefore looked for genetic signatures of this co-evolution in the vervet genome. They indeed found strong signals of natural selection in genes related to viral processes and those known to interact with HIV in humans. “Interestingly, we mainly found evidence for selection in genes that regulate the transcription of viruses, but not in genes that could provide resistance to infection. For example, one of the strongest selection signals is for a gene that regulates the transcription of a different family of viruses, which are harmless in healthy people but cause disease in AIDS patients.", said Dr. Svardal, lead author of the study. The authors take these results to suggest that, rather than preventing SIV infection, vervets have evolved to live with the virus while avoiding the degradation of their immune system. Dr. Nordborg says "There still is a long way to go, but we hope that our research will help the development of antiviral therapies for HIV."



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