A disease which robs children of the ability to walk and talk has been cured by pioneering gene therapy to correct errors in their DNA, say doctors. The study, in the journal Science, showed the three patients were now going to school. A second study published at the same time has shown a similar therapy reversing a severe genetic disease affecting the immune system.
Gene therapy researchers said it was a "really exciting" development.
Both diseases are caused by errors in the patient's genetic code - the manual for building and running their bodies.
Babies born with metachromatic leukodystrophy appear healthy, but their development starts to reverse between the ages of one and two as part of their brain is destroyed. Wiskott-Aldrich syndrome leads to a defective immune system. It makes patients more susceptible to infections, cancers and the immune system can also attack other parts of the body.
The technique, developed by a team of researchers at the San Raffaele Scientific Institute in Milan, Italy, used a genetically modified virus to correct the damaging mutations in a patient's genes.
Bone marrow stem cells are taken from the patient then the virus is used to 'infect' the cells with tiny snippets of DNA which contain the correct instructions. These are then put back into the patient.
Three children were picked for treatment from families with a history of metachromatic leukodystrophy, but before their brain function started to decline.
Prof Luigi Naldini, who leads the San Raffaele Telethon Institute for Gene Therapy, said: "Three years after the start of the clinical trial the results obtained from the first six patients are very encouraging.
"The therapy is not only safe, but also effective and able to change the clinical history of these severe diseases.
"After 15 years of effort and our successes in the laboratory, but frustration as well, it's really exciting to be able to give a concrete solution to the first patients."
Via Dr. Stefan Gruenwald