Could Herpes Simplex (Cold Sores) Play a Role in Alzheimer’s?

Herpes simplex virus (HSV1) has an interesting life.  After infecting the mucous membranes of the mouth or eye, it generates viral particles that burst out of the infected cells and enter sensory nerve cells, where they travel inside the nerve towards the brain.   Then they lie low until they feel it’s time for a new burst of activity. On re-awakening new viral particles are made in the nerve cell, and these travel back out to re-infect the mucous membrane, producing a cold sore or eye infection.  But researchers from Brown University RI, Los Angeles, and the University of New Mexico have found an additional pathway taken by the viral particles that may have implications for the causation of Alzheimer’s.  They’ve published their findings in the online Public Library of Science (PLoS ONE) March issue. 

Using quantitative immune-fluorescence, immune-gold electron microscopy, and live cell confocal imaging, the researchers followed the activity of the viral particles as they traveled the nerve cells. On exiting the nerve cell, they budded into cell membranes containing amyloid precursor protein (APP), which is the major component of the senile plaques found in Alzheimer brains.  Thus HSV1 slows the speed and distribution of APP.  This, according to the researchers, suggests a mechanism for a clinical relationship between HSV1 infection and the risk of Alzheimer’s disease. 

I don’t usually report lab results that aren’t accompanied by evidence that similar findings have been shown in man.  I’ve spent too long in my life showing how results obtained in animals (and isolated cell cultures) are often not reproducible in humans.  But this finding is quite impressive.  And there’s little doubt that HSV1 infection in humans grows from an incidence of 20% in children aged 5 to as much as 85% in seniors.  It should be possible to design a study to determine if there’s an association between the occurrence of Alzheimer’s disease and the occurrence of HSV1 manifestations.  Then we’d know more – and start treating HSV1 promptly.