NEW YORK (Reuters Health) - One year after receiving a new vaccine against Alzheimer's disease as part of an experiment halted due to the vaccine's side effects, some patients showed an improvement in their symptoms of the memory-robbing disease, according to study results released Wednesday.

These findings suggest that, in the future, a vaccine against Alzheimer's disease may one day help stop the disease in its tracks, study author Dr. Roger N. Nitsch of the University of Zurich told Reuters Health.

"This is the first step towards a cure (for) Alzheimer's disease," he said.

Nitsch cautioned, however, that many hurdles must be overcome before any vaccine against Alzheimer's will be available to patients.

The current study, reported in the journal Neuron, included only 30 patients, and with such a small number, it is difficult to say whether any vaccine will benefit Alzheimer's patients overall.

In an accompanying editorial, Bengt Winblad of Huddinge University Hospital in Stockholm, Sweden, and Kenneth I. Blum, deputy editor of Neuron, agree "the results should be regarded as preliminary."

Winblad and Blum write that the original experiment involving the vaccine featured in the current study was halted because six percent of vaccinated patients developed brain inflammation.

"Thus, while there are hopes that it can be mitigated or eliminated, this potentially fatal side effect remains an overriding concern," they note.

Alzheimer's disease is characterized by brain-clogging plaques made up of a protein called beta-amyloid.

Nitsch told Reuters Health that the vaccine his team used consists of synthetic beta-amyloid proteins. Injecting patients with the vaccine causes their bodies to generate antibodies that target those beta-amyloid proteins, he said.

In addition, if a small fraction of the antibodies infiltrate the brain, Nitsch said, they might bind to the beta-amyloid plaques, perhaps slowing Alzheimer's progression.

The current study findings suggest that this process could very well occur.

Among the 30 patients, 24 of whom received the vaccine, 20 appeared to have developed antibodies against the beta-amyloid proteins, the authors note. Furthermore, those who carried beta-amyloid antibodies showed less mental decline one year after vaccination than patients who did not have antibodies against beta-amyloid.

Differences between the two groups were seen in many different areas of mental functioning, including attention, memory, language and the ability to carry out day-to-day activities.

A similar slowing of the progression of Alzheimer's was seen in two of the three patients who developed brain inflammation as a result of the vaccine, Nitsch and his colleagues report.

Whether these improvements last more than one year after being vaccinated is not clear, Nitsch said. "We are currently evaluating the second year," he noted. "Long-term follow up is one of our major objectives for the future."

Nitsch added that the vaccine is currently unavailable to patients, due to the side effects reported in the previous experiment.

SOURCE: Neuron 2003;38:547-554.

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