Do Viruses Trigger Alzheimer's

For decades researchers have been studying the cause of Alzheimer's with a focus on the abnormal presence of two proteins in the brain: beta amyloid and tau. They suspect the proteins damage brain cells, eventually killing them and causing brain shrinkage

But the drugs developed to target these proteins have not worked well, so scientists have been searching for other clues. And one is getting their attention: viruses.

The HSV-one virus which is a herpes virus that causes cold sores and the Varicella Zoster virus or VZV which causes chicken pox. Both viruses dwell dormant in the nerves until they get reactivated. When VZV reappears usually later in life, it shows up as a painful condition called shingles.

Researchers in the newest study used tiny sponges and seeded them with neurons that grow and form networks of firing neurons. They found that infecting these cultured neurons with VZV did not cause abnormal accumulations of proteins seen in Alzhimer's. But, if the neurons already had dormant HSV-one which causes cold sores, the VZV infection reactivated these viruses. And that led to a big increase in both proteins linked to Alzhemier's.

One explanation is that the viruses don't impact the proteins directly but trigger an inflammation that does. A number of studies point to a link to these viruses. One shows that vaccinating against shingles reduces the chances of dementia. And over four hundred published studies now link the HSV-one virus to Alzheimer's. This offers scientists a new focus for therapies to help the growing number of Americans suffering from Alzheimer's.