New Evidence Found Linking Herpes And Alzheimer’s

Researchers have long suspected a connection between the herpes virus and Alzheimer’s disease. A new study provides a potential explanation that could lead to development of a vaccine to prevent the disease or new drugs to treat it, according to the researchers. The study appears in the May 16 issue of Biochemistry, a peer-reviewed publication of the American Chemical Society, the world’s largest scientific society.

Researchers at the University of California, Irvine, demonstrated that a synthetic protein that resembles the herpes simplex 1 virus (HSV-1) mimics the structure and function of a protein called beta-amyloid, a toxic agent that accumulates in the brains of Alzheimer’s patients.

Genetic sequencing revealed that two-thirds of a portion of the viral protein is identical to the beta-amyloid protein. The researchers showed that, like beta-amyloid, it could kill brain neurons, a key feature in the development of Alzheimer’s. Moreover, in laboratory experiments, the viral protein formed abnormal twisted fibers like those found in the brains of Alzheimer’s patients — the definitive hallmark of the disease.

Herpes exists in two common forms. The majority of the population acquires HSV-1, which causes cold sores, during childhood from non-sexual contacts. Herpes simplex virus 2 (HSV-2), also known as genital herpes, is transmitted by sexual contact.

“What’s unique about our finding is that it points to a way in which herpes can be acting,” says Frank M. LaFerla, Ph.D., principal investigator of the study and an assistant professor in the university’s Department of Neurobiology and Behavior. He is also associate director of the university's Institute for Brain Aging and Dementia.

Most people are exposed to HSV-1, but do not develop Alzheimer’s. LaFerla explains this apparent paradox by citing recent studies showing that people genetically disposed to Alzheimer’s are more likely to develop the disease if they are exposed to herpes.

Herpes is one of a growing number of factors believed to contribute to Alzheimer’s, a poorly understood, incurable form of dementia that primarily strikes the elderly and causes severe memory loss. In about 10 percent of cases there is a family history of the disease. President Reagan suffers from the disease, as did his mother.

Researchers believe that the majority of the cases involve multiple factors. While genetic predisposition has been well established, other potential risk factors include stress, prior head injury, and an abnormal concentration of metals in the brain, including aluminum, zinc and lead.

“I think researchers will continue to find new factors associated with Alzheimer’s disease,” predicts LaFerla.

The study was supported by the National Institute on Aging, the Alzheimer's Association, and the state of California.