New hope for Alzheimer’s vaccine

The search for a vaccine is back on track Keystone

Two years after an experimental Alzheimer’s vaccine was suspended over safety fears, Swiss researchers say they are still optimistic about the prospects for immunisation.

Human trials of a modified version of the vaccine are expected to begin later this year.

The trial of the original vaccine on 298 patients worldwide was abandoned in 2002 after 18 patients developed brain inflammation.

The vaccine had been very successful in animal tests and a later Swiss study showed that it could help slow the progress of Alzheimer’s disease.

“Solutions are now being explored to try to separate the positive clinical effects we observed from the side effects,” Roger Nitsch, director of the division of psychiatry research at Zurich university medical school, told swissinfo.

Promising approach

The vaccine is designed to prime the body’s own immune system against accumulations of twisted protein, called beta amyloid, in the brain.

These unwanted clumps known as plaques are characteristic of Alzheimer’s disease and are thought to cause brain damage and dementia.

Trials of the vaccine, manufactured by Elan Pharmaceuticals in the United States, were halted in March 2002 after 18 patients developed meningoencephalitis.

It now seems that, in addition to inducing the desired antibody response, the vaccination triggered other immune system cells called T cells.

The patients who suffered brain inflammation appear to have been those with very high T cell response.

“One patient we observed had no antibodies at all and still suffered from the side effects,” said Nitsch

“This makes us believe that the antibodies themselves do not directly lead to the side effect. The hope for the future is to try to induce a good antibody response and at the same time prevent a cytotoxic T cell response.”

Promising results

Nitsch is cautiously optimistic about the future.

When the trial came to a halt, his team studied 30 of the patients including three with encephalitis.

They found 20 had generated antibodies against beta amyloid and seen a slowdown in the development of their condition, including two who had developed the encephalitis.

Two routes are now being explored. A tweaked version of the vaccine, which stimulates antibody production without overactivating the errant T cells, is heading for clinical trials in the next nine months.

Another approach – injecting specific doses of antibodies rather than stimulating the body to produce its own antibodies – is also set for clinical trials before the end of the year.

“The ultimate vision would be to identify individuals at risk for Alzheimer’s disease and then treat them with preventive treatments,” said Nitsch.

He added that if the immune approach was successful, it could be applied to a wide range of neurogenerative diseases involving abnormally folded proteins in the brain. These include Parkinson’s, Huntington’s and prion disease.

swissinfo, Vincent Landon

In brief

A tweaked version of an encouraging Alzheimer’s vaccine is expected to begin human trials later this year.

The vaccine targets the beta amyloid proteins which form plaques in the brain of a patient with Alzheimer’s.

An international team of researchers tested the original vaccine on 298 Alzheimer’s patients.

They began to produce antibodies designed to attack beta amyloid.

But the study was halted in March 2002 after 18 patients developed the potentially fatal brain inflammation, meningoencephalitis.