Scientists Resurrect Millennia-Old Viruses for Use in Gene Therapy

Resurrect virus gene therapy
Scientists hope that thousand-year old viruses could be used to deliver gene therapy to treat diseases like cystic fibrosis and muscular dystrophy. Eric Zinn

Scientists have successfully reconstructed a virus thousands of years after it became extinct, a development they believe could herald a new step in treating genetic diseases such as cystic fibrosis and muscular dystrophy.

By creating an evolutionary history of adeno-associated viruses (AAVs), which infect humans and primates but do not cause disease, researchers from Harvard Medical School were able to construct Anc80, an ancestral virus which they believe to be between 2,000 and 200,000 years old.

A study published in the journal Cell Reports reports that the researchers utilized the ancient virus as a vectora harmless biological vehicle used to transfer genetic material to a target cell to safely treat liver, muscle and retina conditions in mice. Reproductive material was removed from the viruses, as gene therapy is used to target specific deficiencies and does not require the viruses to reproduce. The researchers did not encounter any toxic side-effects, though they caution that further tests will be required.

Luk Vandenberghe, director of the Grousbeck Gene Therapy Center at Harvard, says that the study could provide a first step towards the creation of fully synthetic viral vectors which could be used to treat genetic disorders. Many of the viruses currently used as vectors in the field of gene therapy are modified forms of viruses which humans have encountered before, which means that the body's immune system can attack the viruses, rendering the therapy useless.

"Historically, viruses or modified viruses have been the most effective way to do gene therapy, to transfer genes into cells, because we're banking on the innate properties of viruses," says Vandenberghe. "We actually believe our work is a first step [towards synthetic vectors] because we have generated a synthetic virus, something that is not currently present in nature."

Gene therapy, where genes are used to combat or prevent diseases caused by genetic mutations, is showing great promise for treating a range of diseases. Earlier this month, trials of a form of gene therapy for cystic fibrosis, where sufferers breathed in healthy genes through a ventilator, showed promise in stabilising and in some cases improving the damaged lungs of patients. Cystic fibrosis affects an estimated 70,000 to 100,000 people worldwide, and the life expectancy for sufferers ranges from 15 to 40 years.

A recent study by the Swiss Federal Institute of Technology and Harvard Medical School also found that gene therapy could be used to treat hereditary deafness in children, after viral vectors were successfully used to transfer healthy genes into the ears of deaf mice. Viral vectors have also been successful in clinical human trials for gene therapies to treat haemophilia, a bleeding disorder where blood fails to clot properly, with the therapies found to improve symptoms for up to four years in patients.

The simple structure of viruses, which consist of a strand of DNA or RNA surrounded by a protective protein coat, means they are ideal for infiltrating the immune system and delivering healthy genes to a target area. Vandenberghe hopes that the technique pioneered in this study will hold promise for treating many diseases using once-extinct viruses as vectors for transferring genes. "Gene therapy is an entirely novel class of drugs and theoretically, it actually has the potential of addressing almost any disease under the sun," he says.