Patch may prevent dementia

The idea of an Alzheimer's vaccine, which had run into serious roadblocks, may have a new lease on life in the form of a skin patch.

In their study involving mice, US researchers found that a "transdermal" vaccine (placed on the skin) was safe and effective in clearing away brain plaques that are hallmarks of Alzheimer's disease.

The findings are reported in this week's issue of the Proceedings of the National Academy of Science.

The Alzheimer's vaccine works by stimulating the immune system to recognise and act against beta-amyloid, the protein that accumulates in the brains of Alzheimer's patients and which many experts feel is the root cause of memory and other cognitive problems.

Tragic end to previous trial
A previous clinical trial of an Alzheimer's vaccine ended in tragedy when a small percentage of study participants developed a dangerous autoimmune response (brain inflammation) and died.

That trial was suspended indefinitely, although the remaining participants have been followed and have been shown to have produced immune system antibodies in response to the vaccine.

A subset of patients from the study have remained stable since the start of that trial four years ago. One of them recently participated in a marathon.

Small number did benefit
"This is telling you that there are at least a small number of patients who appear to have benefited from immunotherapy," said study co-author Dave Morgan, director of the Alzheimer's Research Laboratory at the University of South Florida in Tampa. "This makes it very encouraging to try to develop a safer form of immunotherapy in the event that this could be widely applied to Alzheimer's patients in a way that wouldn't result in brain inflammation."

Generally, the body reacts to a vaccine in one of two ways, called "Th1" and "Th2." The Th1 response is more likely to produce an autoimmune reaction, such as was seen in the earlier Alzheimer's vaccine trial.

Th2 is less likely to produce such a reaction. "One of the advantages of giving the vaccine in the skin is that it biases the response toward the Th2 type of immune reaction," Morgan explained. "That is predicted to have less likelihood of producing the problems observed in the [earlier] trial."

Treated mice seemed healthy
In this study, transdermal immunisation did not seem to trigger any autoimmune problems in mice specially bred to develop Alzheimer's disease.

For an older population of patients, especially, a skin patch would also have several advantages over vaccines that are either injected or given orally.

"It probably would have a much higher rate of compliance amongst an older population," Morgan said.

Morgan and his team plan to keep testing the transdermal vaccine in animals to see if it can halt memory loss. Should these trials prove successful, it could be time to test a skin patch or topical cream in Alzheimer's patients, he said.

Not any time soon
One expert cautioned that an Alzheimer's vaccine isn't imminent, however.

"This is pretty preliminary, basic science sort of stuff," said William Thies, vice president of medical and scientific relations at the Alzheimer's Association. "There's a lot of development between where they are with this paper and where you actually have something on the pharmacy shelf that is there to treat your Alzheimer's. And we do need to keep in mind that we're looking at mice."

Thies also pointed out that many different approaches in the area of Alzheimer's vaccines are being explored right now. – (HealthDayNews)

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Alzheimer's Centre

January 2007