Alzheimer's vaccine seen as treatment, not cure

Experiments with mice suggest it may be possible to one day prevent Alzheimer's disease with a vaccine For more information: Elan Pharmaceuticals 1-800-894-7308 Alzheimer's Disease: No known cure Affects more than 18 million people worldwide Most patients are over 60 In the United States, where 4 million people currently have Alzheimer's, the number could climb to 14 million "in the next 40 or 50 years," as the population ages, according to the Alzheimer's Association Click for more information: description risk symptoms treatment prevention Choose a link above to learn more about Alzheimer's disease. Source: WebMD VIDEO CNN's Rhonda Rowland reports on an experimental vaccine, known as AN-1792, that one day may help prevent Alzheimer's disease Windows Media 28K 80K CNN's Rhonda Rowland explains, today, there are limited options for patients with Alzheimer's disease. Real 28K 80K Windows Media 28K 80K

July 8, 1999
Web posted at: 11:31 a.m. EDT (1531 GMT)

In this story: How vaccine works ... ... On mice Effectiveness on humans uncertain Research useful for other diseases? RELATED STORIES, SITES

(CNN) -- An experimental vaccine which prevents or reduces the buildup of plaque in the brains of mice could potentially be used to treat or even prevent Alzheimer's disease, researchers said Thursday.

It is uncertain whether the treatment will work in humans, but Elan Corp., the Irish pharmaceutical company that developed the vaccine, hopes to get U.S. government permission to begin testing it on people later this year.

Researchers hope to submit a human vaccine to the Food and Drug Administration for approval in five years.

"If we see anything (in humans) resembling like what we saw in our animals ... this should revolutionize Alzheimer's therapy," said Dr. Ivan Lieberburg, Elan's senior vice president of research.

Even if the vaccine works on humans, it would not be a cure, cautioned Bill Thies of the Alzheimer's Association. "In fact, this is probably most likely a preventative therapy," he said.

"People who have established Alzheimer's disease have lost significant amounts of brain cells and probably (won't regain) function of those cells with this kind of treatment," Thies told CNN.

Deposits in the brain of a sticky protein called amyloid are one of the characteristics of Alzheimer's.

The vaccine, known as AN-1792, appears to prevent the formation of these so-called plaques in mice that were genetically engineered to overproduce amyloid.

"We view the plaque ... as an invader in the brain," says Lieberburg. "We were curious to know if we would treat this as though it was any other type of invader, such as a bacteria, and thus use a vaccination approach."

In the study, published in Thursday's issue of the journal Nature, a team of researchers led by Dale Schenk at Elan Corp. tried to trick the immune system of the mice to recognize amyloid as a foreign substance that should be attacked.

The researchers injected nine 6-week-old mice with amyloid combined with substances that excite the immune system. Seventeen other mice of the same age did not get the vaccine.

When the mouse brains were dissected after 13 months, the researchers were surprised to find no or very small plaques in the vaccinated mice; the unvaccinated mice had extensive deposits.

The researchers then tried a more ambitious experiment: injecting the vaccine into year-old mice that already had plaques. An equal number of mice did not get the vaccine during the seven-month treatment.

"We saw that it completely stopped the further progression of the disease," Schenk said. "It looks like it might have actually diminished the plaques."

Amyloid deposits in the human brain are characteristic of Alzheimer's disease

Despite the vaccine's promise, there are a number of reasons the method that worked in mice may not prevent or halt Alzheimer's in humans:

• The amyloid plaques may be a symptom of the disease, rather than the cause.
  
  
• Alzheimer's patients have other changes in the brain that the mice do not fully exhibit, such as tangles of protein inside nerve cells, said Dr. Blas Frangione, head of the Alzheimer's research unit at the New York University School of Medicine.
  
  
• While detectable genetic flaws are linked to some Alzheimer's cases, most patients have no such telltale markers. "If we are going to have the maximal effect of this, we need to find out who has the disease, who is at risk, much earlier," said Dr. Zaven Khachaturian, senior medical adviser to the Alzheimer's Association.

The study raises the prospect of using immunization to treat or prevent other diseases associated with protein deposits.

"Even if (the vaccine) fails to produce a treatment, it introduces the idea of using a vaccination against protein deposits, which are associated with a variety of diseases, Khachaturian said.

Creutzfeldt-Jakob disease, the fatal human brain disorder thought to be related to mad cow disease, would be a candidate. So would Parkinson's disease and myeloma, a form of cancer that overproduces protein in bone marrow.

Medical Correspondent Rhonda Rowland and The Associated Press contributed to this report, written by Jim Morris.