A Unique Treatment
They say you don't fight fire with fire. However, researchers from Johns Hopkins Medicine in Maryland have found that sometimes a virus may be the best weapon against a disease. Their study has been published in The Lancet
The researchers were looking for ways to treat a particular type of age-related macular degeneration (AMD) known as a wet AMD. It's a rare and more severe form of the disease, affecting just 10 percent of all AMD patients, and it causes new blood vessels to grow under the retina, which then leak blood and fluid into the eye, leading to vision problems.
The researchers knew they could halt and even reverse the condition by suppressing an overactive protein called vascular endothelial growth factor (VEGF). Other researchers had been able to do it with monthly eye injections, but this team was hoping to do it with just one injection.
The best way they found to do this was by using a common cold-like virus called AAV2 as a carrier of gene that activates the production of a different protein, sFLT01, to counter VEGF.
In a preliminary trial involving 19 men and women 50 years old and above, the researchers injected the patients with a form of AAV2 that was genetically engineered to penetrate retinal cells and deposit the gene. "After the virus deposited the gene, the cells began secreting sFLT01 which bound to VEGF and prevented it from stimulating leakage and growth of abnormal blood vessels," explained a Johns Hopkins press release.
Promising but Still Limited
The clinical trial showed promising results, with the condition of four of the patients improving dramatically after just one viral injection. Two others saw some reduction in the fluid build up, and the treatment didn't produce any side effects in any patients. "Even at the highest dose, the treatment was quite safe. We found there were almost no adverse reactions in our patients," said researcher Peter Campochiaro.
Of the patients that didn't respond, the researchers discovered that five naturally produced antibodies that would attack the AAV2 virus, rendering it unable to complete its gene depositing mission. They think these antibodies could be prevalent throughout the population, making it difficult to determine how effecting the treatment would actually be.
Nevertheless, this research is a step in the right direction, especially with AMD expected to affect almost 5.44 million people in the U.S. by 2050. "This preliminary study is a small but promising step towards a new approach that will not only reduce doctor visits and the anxiety and discomfort associated with repeated injections in the eye, but may improve long-term outcomes," Campochiaro said.