Childhood herpes may be trigger for dementia

ALZHEIMER’S disease may be triggered in the brain by a herpes virus which strikes in childhood.

Experts say scientists have found the most compelling evidence to date that viruses could cause the brain condition.

It raises hopes that antiviral medicines could one day protect against dementia.

After studying the brains of almost 1,000 people after death, researchers found herpes levels were up to twice as high in those with Alzheimer’s disease.

The strains of herpes found are not those which cause cold sores or sexually transmitted diseases, but instead infect many children, causing a mild rash before lying dormant.

Professor Ben Readhead, lead author of the study from Arizona State University, said: ‘We didn’t go looking for viruses, but viruses sort of screamed out at us.’

Researchers state that virus strains, HHV-6A and HHV-7, may trigger the build-up of a damaging protein called beta-amyloid in the brain, which is thought to rob people of their memories.

If the virus lies dormant in the brain for decades, only to be

‘Viruses screamed out at us’

reactivated in older age, the study suggests beta-amyloid could be triggered to engulf the virus so it cannot get into healthy cells. This could lead to Alzheimer’s disease or make it worse.

If correct, this would mark a dramatic departure from conventional wisdom, which has blamed Alzheimer’s on faulty genes or a combination of bad luck and the ageing process.

However, experts are still divided. Dr James Picket, head of research at Alzheimer’s Society, said: ‘The evidence in this study is the strongest we’ve seen but still doesn’t show the virus causes Alzheimer’s.’

Critics of the virus theory suggest that the virus may get into the brain because Alzheimer’s disease weakens the blood-brain barrier.

But Ruth Itzhaki, professor emeritus of molecular neurobiology at the University of Manchester, said: ‘It looks like a combination of [viruses] and a known genetic susceptibility to Alzheimer’s may be more likely to develop Alzheimer’s, and that some other herpes-type viruses may also play a part.’

‘We now need more research to establish whether these viruses are causally linked to Alzheimer’s, and whether using that information we might be able to develop treatments.’

The study is published in the journal Neuron.