Bangalore: Twenty-two years after the gene for an eye disorder, Leber Congenital Amaurosis (LCA), was discovered from a Bangalore family, it has become the first gene to facilitate a replacement surgery for inherited blindness.
LCA, a retinal disorder that causes vision loss, often from birth, affects one in 10,000 children.
On Thursday, eyecare hospital Narayana Nethralaya in Bangalore said it has tied up with James Bainbridge and other ophthalmology geneticists to offer gene therapy in India, first in LCA and later in other forms of Retinitis Pigmentosa, a group of progressive retinal diseases.
Bainbridge had led a team at the University College London and Moorfields Eye Hospital in a trial gene therapy surgery on LCA in 2007. He also leads one of the three teams globally working in this area and has been running a clinical trial for two years. “We have proved the effectiveness of using the gene RPE65 and are now looking for long-term safety of this therapy,” he said. The trial is nearing completion.
Bainbridge’s team inserted the gene in a type of virus called adeno-associated virus and injected them below the retina of people suffering from LCA due to a mutation in RPE65. Encouraged by the results and lack of any adverse effects so far, Bainbridge and others say the technique could be used for correcting other inherited eye disorders.
10% of blindness is due to gene abnormalities and 60% is found in children.
Though the first gene therapy was tested in the US in 1990 on a four-year-old girl for a genetic disorder that left her defenceless against infections, the technique is far from becoming practical, as it has faced scientific roadblocks as well as a few deaths in clinical trials.
Bainbridge and G. Kumaramanickavel, who co-discovered the gene with Michael J. Denton, say the eye is the only organ so far that has shown good results in gene therapy. “That’s because eye being a small organ, a small amount of genes are required for the therapy and the cellular populations of the eye are more stable than other organs,” Bainbridge said.
While Bainbridge’s clinical trial winds up, Narayana Nethralaya will begin genetic screening of patients in India, looking for those with RPE65 mutations. Alongside, the hospital will screen patients for night blindness where some 70 genes are at play and each person could have a different set of mutations in these genes.
“Not all the genes are known yet and not all the cellular mechanisms leading to the retinal degeneration have been disentangled,” said Denton, who is currently at the University of Otago in New Zealand. “However, huge progresses have emerged with gene therapy developed by innovative laboratories.”