Cold sores linked to Alzheimer's disease

People who suffer from cold sores, which are caused by infection with herpes simplex virus (HSV) type 1, may be at significantly increased risk of developing Alzheimer's disease, new research suggests.

Researchers at the University of Manchester in Britain found HSV type 1 DNA in 90% of amyloid plaques in the brains of people with Alzheimer's disease. Furthermore, 72% of the DNA was directly associated with the plaques. In comparison, in aged normal brains, which contain significantly fewer amyloid plaques, 80% of plaques contained herpes simplex virus type 1 DNA, and just 24% of the viral DNA was plaque-associated.

The same researchers had previously showed that HSV type 1 is a strong risk factor for Alzheimer's disease in people who carry the type 4 allele of the apolipoprotein E gene (APOE-4), and that beta-amyloid accumulates in HSV type 1-infected cell cultures as well as in the brains of mice. Taken together, the researchers say that their findings suggest that the virus is a “major cause of amyloid plaques and hence probably a significant etiological factor in Alzheimer's disease.”

The discovery also raises the possibility that antiviral drugs that block the action of HSV1 may stop the progression of Alzheimer's disease. Another prospect is that a HSV1 vaccine may actually offer protection against the devastating neurodegenerative disease.

Wozniak MA, Mee AP, Itzhaki RF. Herpes simplex virus type 1 DNA is located within Alzheimer's disease amyloid plaques. The Journal of Pathology. 2008;217:131-138.