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BC Researchers Track Evolutionary History of Ancient Retrovirus

A team of Boston College researchers led by Professor of Biology Welkin Johnson has mapped the history of one of the world’s ancient, long-lost viruses following a breakthrough in genetic research.

The ancient retrovirus, ERV-Fc, affected at least 28 ancestors of modern mammals as long as 30 million years ago, with its hosts ranging from mice to dolphins to humans themselves.

Retroviruses—which are abundant today, including HIV and T-cell Leukemia—insert foreign sequences of DNA into their host’s genome that can be passed down generationally. ERV-Fc thrived in its time, infecting a great number of hosts and transferring species; but the virus has since gone extinct, leaving us with only the historical imprints.

In a recent press release, Professor Johnson describes these imprints as “viral fossils,” which are the genetic sequences that remain in the mammalian genome. “In the same way that bones can be used to reconstruct human evolution, these sequences can be used to reconstruct when and where these viruses existed and what species they infected,” explained Johnson.

Professor Johnson’s team set out to reconstruct the virus’s evolutionary history by finding sufficient ERV-Fc loci through extensive examinations of mammalian genome databases. The team then translated the DNA sequences of these loci into protein sequences, which in turn could finally provide insight into the history and evolution of ERV-Fc. It was systematic, technical research.

The team found that ERV-Fc jumped from host to host and traversed every continent except Antarctica and Australia. But in order to survive its diverse host mammals, ERV-Fc had to adapt its genetic makeup frequently.

The retrovirus likely employed a process called genetic recombination, where it exchanged segments of DNA with a number of other viruses, including other variations of the ERV-Fc itself, to provide many necessary adaptations.

William Diehl, who conducted the study with Johnson and was the lead author of the team’s research paper published by eLife, believes the next step in studying viral evolution is applying it to the future—using the information to predict long-term consequences of current viruses. “For example, we could potentially assess the impact of HIV on human health 30 million years from now. The method will allow us to better understand when and why new viruses emerge, and how long-term contact with them impacts the evolution of host organisms.”

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