cause for concern? A new study suggests that the adeno-associated virus (above) can damage chromosomes in gene therapy.
The treatment of patients with gene therapies requires a safe vehicle to transport useful genes and adeno-associated virus (AAV) is widely considered one of the safest. But a new study shows that at least some human cancer cells treated with the virus develop abnormal chromosomes, raising concerns about the safety of long-term gene therapy AAV-based.
Some researchers thought was safer AAV for gene therapy than other so-called viral vectors, because AAV infection is common and causes no known adverse effects. AAV-based therapies gathering also adopted several safety tests. Yet it was unclear exactly how the virus supply and activates genes in human cells. Scientists wondered how DNA AAV jumped into the cell's chromosomes and if it's damaged by doing so.
To find out, geneticist David Russell of the University of Washington, Seattle, and colleagues studied the impact of AAV on genes in a culture cell line cancer. The researchers used a strain AAV adapted to output chromosomes when the cells are treated with a certain drug, bearing parts near the chromosome with it. Then analyzing the DNA sequences of these pieces of chromosomes, the team was able to reconstruct how AAV had altered the cell's chromosomes when inserting itself.
As reported in the February issue of Nature Genetics cell chromosomes had small parts missing or added where the virus itself had inserted. In a cell line of two different chromosomes had abnormally merged. Despite this connection, it is not known if the type of cells studied - a cancer cell line commonly used by researchers - somehow AAV allowed to cause additional damage. More tests on other types of cells is necessary, Russell said, to determine whether patients treated with AAV are at greater risk of chromosomal disturbance, which can lead to cancer.
The study raises a warning flag. "We'll have to monitor these patients" named in safety testing, says therapist Malcolm Brenner gene from Baylor College of Medicine in Houston, adding the results suggest that AAV vectors are probably not safer than other viral vectors currently used. However, Brenner adds, it is far too early to consider dropping AAV, as other evidence suggests it is safe.
Related Sites
Context gene therapy of the US Department of Energy
questions and answers on gene therapy of the National cancer Institute
animated gene therapy primer
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