COMMON wisdom has it that cold sores are troublesome but harmless. However, the herpes simplex virus type 1 (HSV1), which causes cold sores has been found in the brains of people who had Alzheimer's dementia, leading some researchers to speculate that this common virus may cause the brain disease. But the virus has also been found in the brains of people who did not have Alzheimer's Disease. This raises the question of whether there is a difference between people who have the cold sore virus and develop Alzheimer's and those who do not.
In the Lancet, Prof Ruth ltzhaki and her colleagues at the University of Manchester Institute of Science and Technology (UMIST), reported that individuals who inherit a certain form of protein called apolipoprotein E epsilon-4 and who have the cold sore virus appeared to have a much higher risk of developing Alzheimer's than those who had the virus in the brains, but did not inherit this protein. If so, what are the implications?
Usually, HSVI infects the skin, causing a cold sore, and then works its way into the nerves of the face where it remains for the rest of a person's life. The virus usually remains dormant but can reactivate from time to time, causing repeated cold sores at the original site of infection. It is thought the same sort of intermittent reactivation may also occur in people with HSV1 in their brains. If so, the type of apolipoprotein a person has may perhaps determine how much damage occurs during these episodes of HSVI reactivation or how well the brain recovers afterwards, either increasing or decreasing the risk or developing Alzheimer's. If the theory proves correct, it may be possible to prevent Alzheimer's by treating people with cold sores with anti viral or anti inflammatory drugs that reduce the damage incurred by reactivation. Another approach would be to develop vaccines against HSVI.