A COMMON virus that produces cold sores may be one of the main causes of Alzheimer's disease, new research suggests, sparking hope that the devastating condition could be treated with existing drugs.
Scientists believe the herpes simplex virus (HSV1), which is widespread throughout the population, is linked to up to 60% of Alzheimer's cases.
The discovery, following laboratory experiments, raises the prospect of treatment for the degenerative
brain disease, which causes memory loss and language breakdown, with safe antiviral treatments currently used to treat cold sores.
The discovery was made by a team of scientists from Manchester University and has been published in the Journal Of Pathology.
They found that the herpes simplex virus has a potential role in forming plaques of beta amyloid protein that build up in the brain cells and are thought to be the main cause of Alzheimer's.
They have also found firm evidence of HSV1 infection in protein plaques in cell cultures grown in the laboratory.
Professor Ruth Itzhaki, who leads the team, is now seeking funding to test the findings further.
She said yesterday: "One thing that's exciting about our research is we already have drugs that have been used for a relatively long time against HSV1, which are cheap and well tolerated.
"If we are right there's a very good chance we could make progress quickly."
Alzheimer's affects up to 66,000 Scots.
The first symptoms are short term memory loss which can develop into mood swings, confusion and longer term memory problems.
It is expected to become more common as people live longer.
HSV1 is a cousin of the HSV2 virus that causes genital herpes. HSV1 hides in the peripheral nervous system in a latent form and periodically becomes active to cause cold sores.
Antiviral drugs such as acyclovir, sold under the brand name Zovirax, can control HSV1 during the active phase of its cycle.
Although HSV1 is very common, infecting most adults and causing cold sores in about 20% to 40% of them, the research does not suggest that everyone who carries the virus will get Alzheimer's.
Other factors including genetics will also play a role in determining the onset of the degenerative brain disease.
Itzhaki and her team believe HSV1 may enter the brain and become active as people's ageing immune systems lose the ability to keep it contained. It may then promote the build-up of beta amyloid and trigger the onset of Alzheimer's.
Itzhaki added: "We suggest that HSV1 enters the brain in the elderly as their immune systems decline and then establishes a dormant infection from which it is repeatedly activated by events such as stress, immuno-suppression and various infections."
Matthew Wozniak, a member of the research team, added that antiviral treatment would have big advantages over other Alzheimer's treatments.
He said: "Antiviral agents would inhibit the harmful consequences of HSV1 action, in other words, inhibit a likely major cause of the disease, whereas current treatments at best merely inhibit some of the symptoms."
