The brain damage that characterizes Alzheimer's disease may start out in a form similar to that of infectious diseases, according to a new study.
The underlying mechanism of Alzheimer's is very similar to prion diseases like mad cow and its human form, Creutzfeld-Jakob disease.
It involves a normal protein that becomes misshapen and is able to spread by transforming good proteins into bad ones.
The bad proteins accumulate in the brain and form plaque deposits that are believed to kill neuron cells.
For the current study, researchers injected the brain tissue of an Alzheimer's patient into mice and compared the results to those from injected tissue of a control without the disease.
None of the mice injected with the control showed symptoms of Alzheimer's, while all of those injected with Alzheimer's brain extracts developed plaques and other brain changes associated with the disease.
Researchers said the findings open the possibility that sporadic Alzheimer's cases may arise from infectious processes. According to the Alzheimer's Association, of the estimated 5.4 million cases of Alzheimer's in the United States, 90 percent are sporadic.
"We took a normal mouse model that spontaneously does not develop any brain damage and injected a small amount of Alzheimer's human brain tissue into the animal's brain," said Claudio Soto, professor of neurology at The University of Texas Medical School at Houston.
"The mouse developed Alzheimer's over time and it spread to other portions of the brain. We are currently working on whether disease transmission can happen in real life under more natural routes of exposure."
The study was published in the journal Molecular Psychiatry.