Gene therapy for Alzheimer's disease?

Gene therapy could help treat Alzheimer's disease (AD) by reducing the build-up of a harmful protein in the brain, according to a new US study. Researchers at the Salk Institute, the University of San Diego, California and the University of Kentucky have managed to lower the levels of beta-amyloid, one of the disease-causing proteins, by up to 50 per cent in the brains of mice with AD symptoms.

Alzheimer's disease is the most common cause of dementia, affecting one in 20 people over 65. The symptoms are caused by the gradual death of certain brain cells, especially those in the areas involved in memory. Unusual structures called plaques form in the brains of AD patients, which are accumulations of an altered form of the brain protein beta-amyloid. The gene therapy researchers used a gene that makes neprilysin, a protein responsible for controlling levels of beta-amyloid in the brain.

They injected a virus carrying the neprilysin gene into the brains of mice bred to have AD-type plaques, and found that after a month, the plaques on the treated side of the brain were 50 per cent smaller than those on the untreated side. 'What's significant about this is that neprilysin isn't a drug, but a molecule that controls levels of beta-amyloid naturally' said team leader Fred Gage.

The scientists, who published their results in the Journal of Neuroscience, say that the next step is to find out if the changes in the brain lead to improvements in the disease symptoms. However, study author Inder M Verma stressed it would be 'a few years from now' before the researchers could consider applying the procedure in humans.