The researchers hope that the gene therapy may one day prevent a hereditary form of childhood blindness after they had achieved a promising study on chickens with the same condition. They explained that the research, which delayed the onset of blindness in chickens, might one day protect children from becoming blind due to an inherited disease called Leber congenital amaurosis (LCA).
Susan Semple-Rowland at the University of Florida in Gainesville, Florida, US, who led the study, explained that the chickens with the disease are normally born blind. And she further explained that six out of seven chickens that had undergone the gene therapy technique while still in the egg hatched out with sight.
She and her colleagues focused their study on mutations in the GUCY2D gene, which is responsible for LCA1 the most common type of LCA, accounting for up to 20% of cases of blindness. They explained that in people who carry two faulty GUCY2D genes, the cells at the back of the eye are unable to respond properly to light, and therefore cannot send proper visual signals to the brain. They also said that the individuals who suffer from this disorder typically become blind in infancy.
The scientists explained that they used a virus containing a normal copy of the defective photoreceptor gene and injected it through an eggshell into the developing chicken embryo. Rowland said that after the first treated chick had hatched, it began to peck at little dots on a piece of paper. The scientists have however noted that the procedure had slowed the degeneration of the chicks' photoreceptors, but it did not completely halt it.
'The visual capabilities of the treated animals far exceeded our expectations', said Rowland, about their study that is set to appear today in the online journal Public Library of Science-Medicine. She speculated that this therapy if adapted to humans might work any time till the age of 5 yrs, but she also did mention that she was not advocating in-utero treatment.
Gene therapy in general remains controversial, and the adverse effects in humans remain relatively uncertain. There is still a doubt for example that the modified virus used to restore vision in chickens may cause an adverse reaction in people.