February 7, 2013
HIV's origin may date from five to 12 million years ago, according to newly published research done by the University of Washington and the Fred Hutchinson Cancer Research Center, both in Seattle.
HIV-1, which infects 34 million people worldwide, started reaching humans in the early 20th century following multiple transmissions of a chimpanzee virus, known as SIVcpz. HIV-2, a less-virulent and less-transmissible strain of the virus, reached humans after transmission of a sooty mangabey virus, known as SIVsm. Both HIV and SIV are lentiviruses, which are a subfamily (or genus) under retroviruses.
Today, more than 40 non-human primate species in Africa are infected with species-specific strains of SIV. However, SIV infections generally do not lead to AIDS-like disease in non-human primates, leading researchers to believe that SIV and its non-human primate hosts have co-evolved to an apathogenic state. Logically, this co-evolution would have happened over a long period of time, which would make SIV a very old virus. The question is: How far back does this relationship go? How old is SIV itself?
Past research estimated that SIV was at least 32,000 to 75,000 years old, but some experts suspected this was too recent.
In hopes of getting a more accurate estimate of how long primates and lentiviruses may have coexisted, Michael Emerman, Ph.D., a virologist at Fred Hutchinson Cancer Research Center, and Alex Compton, a graduate student in the Emerman Lab, examined the interaction between host and virus on a molecular level and traced back the dynamics of this relationship. They found that APOBEC3G, an immunity factor in the hosts, has evolved alongside Vif (viral infectivity factor), the viral protein that targets APOBEC3G.
The researchers determined that this co-evolution dates back at least five to six million years -- and possibly even 12 million years.
The interest in this subject is more than academic: Understanding how the APOBEC3G in non-human primates evolved to defend against Vif could help us better defend against HIV.
"It is possible that approaches could be used to develop therapies based on how the genes from other primates can act against HIV," Emerman told TheBodyPRO.com, noting the recent Stanford study that genetically engineered HIV-resistant cells by adding rhesus antiviral genes.
"Another approach is to find small molecule drugs that would modify the potency or specificity of the human antiviral genes so that they work better against HIV," he added.
Warren Tong is the research editor for TheBody.com and TheBodyPRO.com.
Follow Warren on Twitter: @WarrenAtTheBody.
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