The BBC's Christine McGourty: "This is a complicated proceedure"

Scientists have found that immunisation can prevent deposits associated with the disease from forming in the brains of mice - and human trials of the same technique could begin as early as next year.

At autopsy, the brains of Alzheimer's sufferers contain characteristic plaques, or deposits, of a substance called beta amyloid, alongside tangles of knotted nerves.

John Groom of Elan Corporation: "A very exciting and encouraging finding"

Now, writing in Nature magazine, scientists have shown that these can be prevented from forming in mice by immunising the animals with injections of that same beta-Amyloid protein.

Dr Dale Schenk and his team at US company Elan Pharmaceuticals also found that the technique worked in older mice, where plaques had already started to develop in their brains

Humans and mice

"It surprised us beyond belief," he says. "We saw that we had completely blocked the progression of the disease in those animals that had been vaccinated.

The mouse disease is not exactly like the human illness

"And, in fact, it actually looks like it might have improved somewhat from where they started."

Whether this is a possible treatment for Alzheimer's disease in humans, remains to be seen. The existing mouse models for Alzheimer's disease only partially mimic the human disease.

While it is true that the amyloid protein accumulates in their brains, the mice do not display all the behavioural, histological and electrophysiological defects associated with the disease in humans.

What is more, it is not entirely clear whether the deposits are the cause of neuronal dysfunction and death, or are merely a consequence of the disease.