While an Alzheimer's vaccine can successfully treat predominant pathology, that is clearing beta-amyloid plaques from the brain, it has little effect in restoring lost learning and memory abilities, reveals a University of California (Irvine) study.
The study suggests that the treatment for beta-amyloid plaques after significant plaque growth only has limited clinical benefit, while a combination of vaccination with therapies also targeting related neuron damage and cognitive decline may offer the best treatment opportunity for people with this neuro-degenerative disease.
"We've found that reducing plaques is only part of the puzzle to treat Alzheimer disease. Vaccines such as this one are a good first step for effective Alzheimer's treatment, but complimentary treatments must be developed to address the complexity of the disease," said study leader, UC Irvine neuro-biologist Elizabeth Head.
For two-years, researchers studied the effect of a vaccine in aging canines.
The vaccine contains the beta-amyloid 1-42 protein and stimulates the immune system to produce antibodies against this same protein that is in the brain plaques.
Dogs are used for such studies because beta-amyloid plaques grow naturally in their brains and they exhibit cognitive declines similar to those seen in humans.
The researchers observed little difference in the behavioural test results between immunized and non- immunized dogs. Later, brain autopsies showed that although plaques had been cleared from multiple brain regions, including the entorhinal cortex, a region of the brain involved with learning and memory and primarily affected by Alzheimer's, damaged neurons remained.
According to Head, this discovery not only helps explain this little difference but it implies that after clearing beta-amyloid plaques from the brain, the next step is to repair these neurons. And this approach will be critical for treating and reversing the effects of the Alzheimer's disease and thus researchers are now developing approaches to repair these damaged neurons and hope to test them clinically.
The results of this study appear in the recent issue of the Journal of Neuroscience.