Resurrection Of Extinct Virus Could Open The Doors To Gene Therapy Innovations

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Researchers have recreated ancient viruses in order to stop the immune system from attacking virus vectors during gene therapy. Photo courtesy of Shutterstock

Gene therapy involves using viruses to replace missing or malfunctioning genes in order to treat some diseases, such as cancer. Experts believe this technique is at the forefront of medical treatment, but unfortunately it has one massive flaw: the immune system often destroys the viruses before they have the chance to deliver the therapy. According to a recent study, the way to get around this flaw could be by resurrecting an ancient virus.

Currently, doctors use viruses that naturally circulate the human population as vessels, or vectors, for their gene therapies. According to a press release, viruses make the perfect vessels for gene therapy because they naturally invade cells and subsequently inject their own genetic material inside, which then replicates further — normally causing infection. Taking advantage of viruses' natural inclination to infect certain organs, scientists can manipulate this process so that the viruses inject cells with missing or malfunctioning genes, rather than their own genetic material, Scientific American reported. Gene therapy has proved successful in treating conditions, such as cystic fibrosis, and restoring vision.

Viruses, such as herpes and polio, have previously been used as vectors for gene therapies. However, if a patient has already been exposed to these viruses, the treatment becomes significantly less effective. To address this problem, scientists have worked to engineer different versions of common viruses. But viruses are complex, and more often than not, these efforts alter their functionality, rendering them useless. 

A team of scientists in Massachusetts has taken an interesting approach to solving this problem. Instead of engineering a new type of viral vector, the team has resurrected extinct viruses. In order to accomplish this impressive feat, the researchers created an evolutionary timeline of the adeno-associated virus, known as AAV. Although there is still debate over whether or not viruses are considered living or not, like other living organisms, their structure has changed and evolved over time. By creating an outline of the changes that occurred in the virus over the course of its evolutionary history, the team was able to recreate nine synthetic ancestor viruses.

Results showed that when the most ancient of all these lab-engineered viruses, Anc80, was injected into mice, it was able to directly target the liver, muscles, and retina without producing any toxic side effects.

"The vectors developed and characterized in this study demonstrate unique and potent biology that justify their consideration for gene therapy applications," senior study author Luk H. Vandenberghe explained in a statement ."From this knowledge, we hope to design next-generation viruses for use as vectors in gene therapy."

In future research, the team hopes to use these ancient viruses to better understand the evolution of viruses and develop more effective gene therapy techniques.

Source: Zinn E, Pacouret S, Khaychuk V, et al. In Silico Reconstruction of the Viral Evolutionary Lineage Yields a Potent Gene Therapy Vector. Cell Reports. 2015

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