Cold sores linked to Alzheimer’s Disease
Like millions of others, you might have experienced an annoying cold sore from time to time. After a week it went away. No harm done, right? Maybe not. Scientists discovered a gene known to be a major risk factor for Alzheimer's disease puts out the welcome mat for the virus that causes cold sores, allowing the virus to be more active in the brain compared to other forms of the gene. The findings, published online in the journal Neurobiology of Aging, add some scientific heft to the idea, long suspected by some scientists, that herpes somehow plays a role in bringing about Alzheimer's disease.
The research links a form of the ApoE gene known as ApoE-4, which after advanced age, is the leading known risk factor for getting Alzheimer's disease, with the form of herpes -- herpes simplex 1 or HSV -- that infects more than 80 percent of Americans and causes cold sores around the mouth. The findings from a group at the University of Rochester Medical Center showed that the particular form of the gene that puts people at risk also creates a fertile environment for herpes in the brain, allowing the virus to be more active than other forms of the ApoE gene permit.
The lead researcher of the study found that people with the ApoE-4 version of the gene who are infected with herpes are more likely to get Alzheimer's disease than people infected with herpes who have a different form of the ApoE gene, or than people who have the ApoE-4 gene but who don't have herpes.
Other scientists have found that a herpes infection is active more often -- causing the tell-tale cold sores around the mouth -- in the 25 percent of people who have a copy of the ApoE-4 gene. In other words, people who are frequently troubled by cold sores are more likely to have the gene that makes them more vulnerable to Alzheimer's disease. However, people with the ApoE-2 gene have a much smaller risk of developing Alzheimer’s since this gene helps clear toxic amyloid beta plaque from the brain as well as keeping brain cells safe from the virus.
The research team is exploring different ways that herpes might affect the development of Alzheimer's disease. One possibility is that the body's immune response against herpes somehow damages the brain, and that such damage is worse in people with the ApoE-4 copy of the gene. Earlier this year Federoff's team published a study that showed inflammation is the earliest change that could be detected in a brain affected by Alzheimer's disease, before any of the hallmark plaques or tangles and certainly long before any behavioral changes are seen. Such inflammation often is a byproduct when the immune system fights an infection.
SOURCE: Science Daily