A Better Way To Deliver Gene Therapy

While gene treatment continues to be a promising area of medicine, a major drawback of this kind of therapy can spell failure for a number of patients enrolled in gene treatment clinical trials: Most people's immune systems may destroy the viral carrier that is most often used to deliver healthy genes into sick cells.

A new study explains that researchers may have found a way around this problem.

Scientists used a laboratory technique called polymerase chain reaction (PCR) to alter genetic sequences of the outer coating, or capsid, of adeno-associated virus (AAV). AAV is a normally innocuous virus that is often used to deliver healthy genes to diseased tissues.

"We were able to make random changes throughout the entire genetic sequence of the AAV capsid," said Brian Kaspar, a co-author of study and an assistant professor of pediatrics at Ohio State University.

"And by doing that we generated more than a million different variations of this capsid, including mutations that the human immune system hopefully won't recognize and therefore shouldn't react against".

The scientists describe their technique in the current issue of the journal Nature Biotechnology.

In gene treatment, physicians insert healthy genes into a person who has an unhealthy form of those genes. The hope is that these new, good genes will correct the problem. Viruses are currently the most common vehicle used to deliver genes into the body.

"Most clinical trials that test gene treatment use AAV because it is a virus that doesn't make people sick," said Kaspar, who is also an investigator with the Center for Gene Therapy at Columbus Children's Research Institute.

While AAV doesn't appear to have any adverse affect on health, scientists estimate that anywhere from 50 to 90 percent of people react to the AAV as if it were an intruder.

This has presented problems in some clinical trials where patients created antibodies that destroyed the virus, and decimating the virus also wipes out the healthy genes that it carries.



Source: Ohio State University

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