Alzheimer's Vaccine May Be Close to Fruition

Scientists from the Oklahoma Medical Research Foundation (OMRF; Oklahoma City, USA) immunized laboratory mice engineered with Alzheimer's with a protein believed to play a major role in the disease-causing process. The mice that received the vaccination demonstrated a significant reduction in the accumulation of protein plaques, which when present in the brain for long periods of time, are thought to cause the cell death, memory loss, and neurologic dysfunction characteristic of AD. The immunized mice also showed better cognitive performance than control mice that had not received the vaccine.

"These results are extremely exciting,” said Jordan Tang, Ph.D., head of the Protein Studies Research Program at OMRF and lead investigator of the study. "They certainly show that this vaccination approach warrants additional investigation as a therapy for Alzheimer's disease.”

The new study was published in November 2007 issue of The Journal of the Federation of American Societies for Experimental Biology. Dr. Tang and his colleagues at OMRF previously had identified the cutting enzyme (known as memapsin 2) that creates the protein fragments believed to be the culprit behind Alzheimer's. In the current study, researchers used mice that had been genetically engineered to develop symptoms of Alzheimer's, and then immunized the animals with memapsin 2.

"What we saw is that the mice immunized with memapsin 2 developed 35% fewer plaques than their non-vaccinated counterparts,” said Dr. Tang. "Those immunized mice also performed better than control mice in tests designed to assess their cognitive function.”

Dr. Tang's work with memapsin 2 also has led to the creation of an experimental drug to treat AD. That drug, which works by inhibiting the cutting enzyme, began human clinical trials in the summer of 2007. Dr. Tang stressed that the vaccine approach should be viewed as a supplement to--instead of substitute for--the experimental inhibitor and other treatments currently in development for the illness.

"Alzheimer's is a complicated, multi-faceted disease,” stated Dr. Tang. "As with illnesses like cancer and heart disease, Alzheimer's demands that we develop many different approaches to combat it. We cannot rely on a ‘one-size-fits-all' strategy, because what works in one patient will not necessarily work in another.”

A vaccination approach--getting the immune system to break down the plaques--has been considered a promising way to fight the disease, but its success has been limited. OMRF president Stephen Prescott, M.D., is hopeful that Dr. Tang's research will avoid the hurdles that beset earlier efforts at devising a vaccine. "This vaccination stimulates the immune system more gently than previous Alzheimer's vaccines, so we are optimistic about its prospects going forward,” he said. "Once again, Dr. Tang has found an innovative way to make inroads against a devastating and poorly understood disease.”

The next step, according to Dr. Tang, will be to progress the work to the point that it can be evaluated in humans. "There currently is no effective treatment for Alzheimer's disease, so we must explore every possible option to find a way to stop it,” he said.

AD is a neurologic disorder characterized by slow, progressive memory loss due to the gradual death of brain cells.


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Oklahoma Medical Research Foundation