Previous attempts had disappointing results. It caused the disease, and the patient's own body reacted against the virus by producing antibodies. A more recent experiment used a virus that usually causes no symptoms. In an effort to avoid the side effects caused in previous experiments, researchers removed almost all of the virus's original genes. It's harder for the immune system of the body to find it and react to it.
Researchers monitor the treatment with a flexible scope.
Eventually, they expect gene therapy could be applied with simple aerosol inhalers. But hopes for gene therapy are tempered by caution. We have to work out these strategies that make this work. I believe that ultimately we will. Practical gene therapy is still years away, researchers say.