Cold sores linked to Alzheimer's disease

ALBUQUERQUE, April 7 (UPI) -- The herpes simplex virus type 1, which causes cold sores on the lips and mouth, has been linked to dementia, U.S. researchers suggest.

Principal investigator Dr. Elaine Bearer of the University of New Mexico with colleagues at Brown University, and House Ear Institute, says the herpes simplex virus type 1 infections grow inside cells and persist in a latent form inside nerve cells. Re-activation and growth of this infection contribute to cognitive decline associated with Alzheimer's disease, Bearer says.

"Herpes infects mucous membranes, such as the lip or eye, and generates viral particles," Bearer says in a statement. "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."

The researchers tagged the herpes virus inside cells with a green fluorescent protein and watched the herpes particles emerge from infected cells. These newly produced viral particles exit the cell nucleus and then bud into cellular membranes containing amyloid precursor protein -- the major component of senile plaques found in the brains of Alzheimer's disease patients.

The findings, published in the journal PLoS ONE, indicate that most intracellular herpes particles undergo frequent, dynamic interplay with amyloid precursor proteins, which facilitates viral transport.

This dynamic interaction reveals a mechanism by which herpes simplex virus type 1 infection leads to Alzheimer's disease, which strongly suggests a causal link between herpes and Alzheimer's disease, the researchers say.