Zoomer | March 26th, 2009
Aging is the biggest risk factor for Alzheimer’s disease, but as researchers in England suspect, the virus that causes cold sores may also play a role
By Jayne Macaulay
The older you get, the more frightening Alzheimer’s disease (AD) seems. About half a million Canadians are currently living with the brain disease, which gradually strips away their ability to think and remember. One in 10 of them is under the age of 60.
Dr. Jack Diamond, scientific director for the Alzheimer Society of Canada, says, “Your body has a whole lot of defence mechanisms … but as you get older, those mechanisms are not so e cient,” he says. And when risk factors overwhelm the body’s ability to deal with them, you face the possibility of Alzheimer’s.
On its own, each risk factor offers a relatively small percentage increase in someone’s chances of developing the disease, he notes. Risk factors include high blood pressure, high blood cholesterol, diabetes, obesity, depression, concussion and genetics (having a parent or siblings with AD). The brains of people with Alzheimer’s characteristically have higher-than- normal amounts of a protein called beta amyloid, which eventually clumps in plaques. Another protein, tau, found within normal brain cells, is altered in Alzheimer’s and forms tangles thought to be toxic to the cells.
Now, there’s news for those of us who don’t fall into the typical risk factor categories. Researchers at the University of Manchester in England believe the herpes simplex virus 1 (HSV1), which causes cold sores, may play a role in the formation of amyloid plaques. In their investigation, they found HSV1 DNA in plaques in elderly brains. Those with AD had more plaques with a greater concentration of viral DNA than the normal brains.
Dr. Ruth Itzhaki, head of the research team, says once the body is infected, the virus stays in the peripheral nervous system (PNS). There, and in the brain, it’s reactivated by stress, immunosuppression and brain inflammation caused by systemic infection, her group reported in the Journal of Pathology. “Reactivated in the PNS, it causes cold sores in some but not everybody,” Itzhaki says. “We think it similarly causes damage in the brain.” In people with a particular genetic marker (the type 4 allele of the APOE gene), it causes greater harm, and susceptibility to AD. She notes: “We have no evidence of any direct linkage between cold sores and the disease of Alzheimer’s.”
In their paper, the team proposed clinical trials of antiviral agents to treat the disease and development of a vaccine to prevent it. Funding for this further study is a problem, however. “It’s regarded as a rather heretical idea,” Itzhaki says, “the way the idea a bacterium could be involved in stomach ulcers was recently regarded.”
Diamond thinks we need to know how much risk of developing Alzheimer’s HSV1 confers. “It may be less important than looking after your blood pressure, cholesterol and stress,” he says. “You can help yourself not get Alzheimer’s by doing moderate exercise — going up and down stairs, mental exercise, eating the right diet.”
He also says the body has its own antioxidant system to handle free oxygen radicals, but it’s overwhelmed in some diseases, such as Alzheimer’s. There may be a case for taking antioxidants such as vitamins C and D and folic acid (check with your physician).
Drugs aimed at treating, not just slowing, Alzheimer’s are nearing the end of clinical trials. Diamond estimates some may be available in three to five years. It will take longer to fi nd a way to cure patients, not just halt their disease. Research is ongoing to help re-establish brain circuitry, so they can reclaim memories, the essence of their lives. To learn more, go to www.alzheimer.ca.