6 April 2011
Herpes linked to Alzheimer's disease
by George Atkinson
HSV1 (herpes) infections appear to contribute to the cognitive decline associated with Alzheimer's disease, say researchers at Brown University.
"Herpes infects mucous membranes, such as the lip or eye, and generates viral particles," said lead researcher Elaine Bearer. "These viral particles burst out of the cells of the mucous membrane and enter sensory nerve cells where they travel inside the nerve toward the brain. We now can see this cellular transportation system and watch how the newly formed virus engages cellular APP [amyloid precursor protein, the major component of senile plaques found in the brains of Alzheimer's disease patients] on its journey out of the cell."
The scientists used live imaging to watch the HSV1 particles emerge from infected cells and then bud into cellular membranes containing amyloid precursor protein.
This "dance" between viral particles and cellular APP results in changes in cellular architecture and the distribution of APP. Results from this study indicate that most intracellular HSV1 particles undergo frequent, dynamic interplay with APP, which facilitates viral transport while interfering with normal APP transport and distribution. This dynamic interaction reveals a mechanism by which HSV1 infection leads to Alzheimer's disease.
Symptoms of primary HSV1 infection include painful blisters of the mouth, lips or eyes. After infection, HSV1 persists in nerve cells by becoming latent. Upon re-awakening, new viral particles are made in the neuron and then travel back out its pathways to re-infect the mucous membrane.
"Clinicians have seen a link between HSV1 infection and Alzheimer's disease in patients, so we wanted to investigate what might be going on in the body that would account for this," notes co-researcher Shi-Bin Cheng. "What we were able to see in the lab strongly suggests a causal link between HSV1 and Alzheimer's Disease."
"It's no longer a matter of determining whether HSV1 is involved in cognitive decline, but rather how significant this involvement is," Bearer asserts. "We'll need to investigate anti-viral drugs used for acute herpes treatment to determine their ability to slow or prevent cognitive decline."
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Source: Brown University