According to researchers in Japan they have developed a DNA vaccine that reduces the symptoms of Alzheimer’s disease in mice without causing side-effects.

Alzheimer’s disease, the most common cause of dementia, is believed to result from overproduction of small proteins that form “plaques” that clutter the brain.

Dr. Yoshio Okura, of Tokyo Metropolitan Institute for Neuroscience, and colleagues say the vaccine reduced the deposition of plaque in mice aged seven and 18 months by between 15.5 per cent and 38.5 per cent respectively compared with untreated mice.

Another vaccine against Alzheimer’s had to be halted halfway through a clinical trial in 2003 because 18 of the 298 patients developed severe swelling in their brains.

This new vaccine did not trigger such side-effects even after prolonged treatment, and the team believes it is “highly effective and safe” and promising for use on patients.

The researchers say the DNA vaccine given by intramuscular injection, which stimulates the production of anti-amyloid-beta antibodies may also be cheap to produce.

Experts say the results mean that vaccine may be able to be tested on humans in the future and supports the theory that a vaccine is the best hope for fighting the devastating disease.

The researchers say that the vaccine cut the beta-amyloid levels by 40 percent after six months.

They believe nonviral beta-amyloid DNA vaccines are highly effective and safe in reducing the beta-amyloid burden in model mice and are a promising vaccine therapy against Alzheimer’s disease in humans.

The research is published in the current issue of the Proceedings of the National Academy of Sciences.