Irish-based Elan Corporation made a major announcement this week about research which could quickly lead to a vaccine against Alzheimer's Disease, the progressive, degenerative brain disorder that invariably causes death. On the other hand it might lead nowhere.

Such are the complexities of the advanced medical research being put by the pharmaceutical companies into this disease, estimated by the Alzheimer Society of Ireland to affect more than 33,000 people here.

There is no doubting however the scientific importance of the research findings presented by Elan which in turn made their way as lead news item into the pages of one of the top scientific journals, Nature.

The California-based research team, acquired in 1996 when Elan purchased Athena Neurosciences, produced a vaccine used in laboratory mice that reversed one of the key effects associated with Alzheimer's, the formation of protein "plaques" in the brain. The plaques always form in the brain cells of Alzheimer's patients, building up like cholesterol in the blood vessels of patients with heart disease.

The disease has so confounded scientific attempts to understand it, however, that there is disagreement over whether these plaques actually cause the brain damage and dementia associated with Alzheimer's or are only a side effect of no importance.

The researchers do not have information yet on whether the removal of the plaques means the patient will lose their Alzheimer's symptoms. Nor can they assume that a treatment that has been shown to work well in mice will translate to humans.

Company staff are nonetheless quietly confident that they have discovered what might become a powerful treatment for the disease. "It is our contention that it is the plaque build up that causes the degeneration," said Mr Seamus Mulligan, executive vice-president of corporate development in Elan Corporation.

"We do not absolutely know for sure," stated Dr Ivan Lieberburg, senior vice-president of research at Elan Pharmaceuticals, which conducted the work. His view remains, however, that if the plaques could be removed then this could lead to a halting or even reversal of the disease in patients with Alzheimer's.

The research approach seems disarmingly simple - use a vaccine based on the plaque itself so that the body's own immune system destroys it. This in fact is exactly what the researchers did, using a small chunk of the protein, called beta-amaloid, which builds up along nerve cells in the brain.

The scientists presented two related studies in Nature. In both cases they used their vaccine on mice, which had been genetically engineered to develop at a young age the plaque build-up typical of aged human Alzheimer's patients. The mice overproduced the human form of beta-amaloid, but did not exhibit the other symptoms and changes associated with the disease in humans, so the model was not a complete match with Alzheimer's in humans.

Even so the results were quite dramatic by any standard. In the first study the vaccine was given to young mice to see whether it could prevent the plaque build-up and it succeeded very well. Untreated mice had developing plaque deposits, but the treated mice remained more or less clear.

In the second study, older mice that had already developed the characteristic plaque deposits along the nerves were given the vaccine to see whether the build-up could be cleared away. Remarkably the vaccine took effect and the mice's own immune systems broke down the deposits, leaving the nerves clear of beta-amaloid. "Collectively the results suggest that beta-amaloid immunisation may prove beneficial for both the treatment and prevention of Alzheimer's Disease," the Elan authors, lead by Dr Dale Schenk, conclude in Nature.

As with all good research, the report raises more questions than it answers. Can the work be reapplied in humans? Would it make any difference to patient symptoms if it could? Does it have side effects? Elan is preparing an Innovative New Drug (IND) application for the Food and Drug Administration in the US and will submit this before the end of this year, Mr Mulligan said. If granted, the IND licence would permit the company to begin limited trials on human patients.

The Alzheimer's Society here is happy to see such research, which holds out at least some promise for those patients and their families afflicted by this disease. "Any treatment that will enable us to halt the progression of the disease would greatly help lessen the impact of dementia not only on the health service in Ireland but also on the family and main care-giver," stated the Society's chief executive, Mr Maurice O'Connell.

Mr Mulligan also cautions, however, that even if things went well it would still take some years to clear all the administrative hurdles and get onto the market.