Evidence implies the herpes virus may be a cause of the disease, suggesting that effective and safe antiviral drugs may be able to treat the disease, perhaps even develop vaccinations against it. Herpes simplex virus type 1 is implicated in the disease, and that it infects most people in infancy then remains dormant in the peripheral nervous system, occasionally stress can activate the virus.
It was discovered in 1991 many elderly people have HSV1 is present in the brain, and was shown that it confers a strong risk of AD when present in the brain of those who carry APOE4 genes in 1997.
HSV1 can become active in the brain, repeatedly which could lead to cumulative damage. APOE4 carriers who have HSV1 in the brain have a 12 times greater chance of developing Alzheimer’s disease.
HSV1 infection of cell cultures has been found to causes beta amyloid and abnormal tau proteins to accumulate which is a characteristic of AD.
HSV1 is believed to be a contributing factor for the disease, entering elderly brains as immune systems decline to establish a latent infection from which it becomes reactivated by events such as stress, a reduced immune system, and brain inflammation induced by infection by other microbes. Reactivation leads to viral damage in infected cells and viral induced inflammation; repeated activation is suggested to cause cumulative damage leading to AD in those with the APOE4 gene; as presumably carrier of this gene the disease develops in the brain because of greater HSV1 induced formation of toxic products, or less repair of damage.
Studies suggests antiviral agents might be used for treating AD, main antiviral agents prevent new viruses from forming helping to limit viral damage. Acyclovir, an Anti-herpes drug, has been found to block HSV1DNA replication, and decreases levels of beta amyloid and tau caused by HSV1 infection of cell cultures in earlier studies.
Studies only show an association between HSV1 and AD, they do not prove the herpes virus to be an actual cause; to prove that a microbe is actual cause of a disease it must be shown that an occurrence of the disease is reduced by targeting the microbe with specific anti-microbial agents or by specific vaccination against the microbe.
Use of specific anti-herpes agents in a large scale population study in Taiwan has been demonstrated to have been successful in prevention of AD, hopefully information from other countries can yield similar results.
