British doctors delivered a working gene to one of the eyes of children with hereditary retinal dystrophy and significantly improved their vision. Before treatment, the patients could only distinguish light, but 3.5 years after therapy, they could already perform simple visual tasks. An article describing the work was published in The Lancet.
Hereditary retinal dystrophies lead to blindness in children from birth. There are 26 known genes, a defect in which can cause vision impairment. To date, treatment exists only for RPE65-associated dystrophy: an adenoviral vector is delivered to the eye, which contains DNA with a working gene of the RPE65 enzyme, which "turns on" the light-sensitive cells of the eye.
The AIPL1 gene codes for a protein needed for phototransduction. It is expressed in rods and cones during embryonic development. In children with a defect in AIPL1, the rods and cones do not work properly and gradually die off, so they are born virtually blind and can usually only detect light.
The researchers, led by James W B Bainbridge of King's College London, selected four children (aged 1–2.8 years) from 42 people with a defect in the AIPL1 gene who had relatively intact areas of the fovea, a region of the retina that contains a large number of photoreceptors, making gene therapy more likely to be successful.
The scientists created a vector based on the adeno-associated virus encoding the AIPL1 sequence. The drug was delivered to one of the patients' eyes using a subretinal injection. To evaluate the effect of the therapy, the children were given simple tasks - putting pencils in a cup or picking up objects from the floor.
Three and a half years after treatment, the children's vision in the eye that had been treated had improved significantly, and they were able to perform simple visual tests. By the time of the examination, vision in the untreated eye had been completely lost.
Scientists hope to make the treatment available to more patients in the future, given the impressive results and lack of serious side effects.
In addition to hereditary retinopathies, gene therapy is also used to treat hereditary lesions of the ganglion cells of the retina and optic nerve—Leber's optic neuropathy.
