Most people get infected by the herpes simplex virus 1 (HSV1), which causes cold sores, at a young age. Herpes viruses remain for life in the neurons and immune cells, and reactivate and resurface in the form of cold sore blisters when people are stressed or ill.
In a new study published in the journal Frontiers in Aging Neuroscience on October 19, Ruth Itzhaki, from the University of Manchester in England, cited a growing number of evidence that suggest the cold sore virus may cause Alzheimer’s disease.
The virus is a different strain from the HSV2 virus that causes genital sores, but it appears to raise the risk for Alzheimer’s disease, a neurological condition that affects about 5.7 million Americans and remains incurable.
Itzhaki said that HSV1 can be found in the brain of elderly people who suffer from Alzheimer’s disease.
Itzhaki, who has spent more than 25 years investigating a potential link between herpes virus and Alzheimer’s, also said that HSV1 could account for half or more of Alzheimer’s disease cases.
Itzhaki thinks that herpes contributes to Alzheimer’s disease by migrating into the brains of elderly people once their immune system starts to naturally decline.
When the virus has infected the brain, HSV1 causes damage and inflammation in neurons whenever it is reactivated by events such as infection by other microbes, immune suppression, and stress.
The damage is particularly bad for carriers of the APOE4 gene. People with APOE4 gene and HSV1 have 12 times greater risk of developing Alzheimer’s disease.
“We suggest that repeated activation causes cumulative damage, leading eventually to Alzheimer’s disease in people with an APOE4 allele,” Itzhaki said, according to Health Day.
“Presumably, in APOE4 carriers, Alzheimer’s disease develops in the brain because of greater HSV1-induced formation of toxic products, or lesser repair of damage.”
Treating people with antiviral drugs, however, may help protect them from Alzheimer’s.
A new study carried out in Taiwan offers hope for a possible treatment for Alzheimer’s disease. The study indicates that getting rid of herpes in the body through antiviral drugs may reduce the risk for Alzheimer’s.
Itzhaki said that the antiherpes antiviral drug acyclovir prevented the DNA of HSV1 from replicating, and reduced the levels of beta amyloid and of P-tau caused by HSV1 infection.
Beta amyloid plaques and tangles of tau proteins are considered as among the hallmarks of Alzheimer’s disease.
The Taiwan study has shown that antiviral treatment caused a dramatic drop in the number of people severely infected by HSV1, who later developed dementia.