Genetic engineering has achieved unique resultsin such an important branch of medicine as ophthalmology. The use of modified genes made it possible to slow down and reverse the development of the disease leading to blindness at a young age of 20 to 30 years. Previously, Leber's hereditary optic neuropathy (LHON), caused by mutations in retinal cells and causing irreversible degeneration of the optic nerve, led to near-total blindness and was cured in less than 20% of cases.
It is noteworthy that LHON patients whose doctorswere able to maintain vision, remained visually impaired with a visual acuity index of 20/200 (the largest letter on the standard vision diagram). LHON affects one person in 30 thousand, therefore, the technique proposed by scientists from the University of Cambridge, the University of Pittsburgh and the Paris Institute of Vision, will help save eyesight in thousands of people around the world. The gene therapy technique undergoing the third phase of clinical trials has successfully cured 37 patients suffering from LHON.
However, in the course of research andclinical trials have revealed another surprising property of the human vision system. The mutated genes were injected into one eye, but significant visual improvements were noted in both eyes in 78% of the patients tested. This fact supports the hypothesis that the improvement in vision in untreated eyes could be caused by the transfer of viral vector DNA from the injected eye.
The new LHON treatment method is based onusing a modified rAAV2 / 2-ND4 DNA fragment capable of replacing the MT-ND4 gene fragment mutated during the disease. The viral vector is introduced by injection into the vitreous humor at the back of the eye.
To confirm the theory of DNA transferintroduced by injection into one eye to the other, an additional test was carried out on macaques with organs of vision similar to those of humans. Three months after injecting rAAV2 / 2-ND4 into one eye of the animals, various parts of the eye and brain were analyzed. As a result, DNA from the viral vector was found in the anterior segment, retina, and optic nerve of the untreated eye. Thus, the unexpected improvement in vision seen in untreated eyes could reflect the interocular diffusion of rAAV2 / 2-ND4.
According to scientists, gene therapy providesthe optimal solution for the treatment of many hereditary diseases caused by gene changes. In the future, other mitochondrial diseases can be treated with the same technology.