Exposure to some viruses may affect the odds of developing pediatric multiple sclerosis, a new research study has found.
In a paper published in the journal Neurology, OMRF scientist Judith James, M.D., Ph.D., and University of California, San Francisco, scientist Emmanuelle Waubant, M.D., Ph.D., in partnership with the Pediatric MS Network, found that some common viruses could increase or decrease the risk of pediatric MS.
MS is a chronic, often disabling disease that attacks the central nervous system. Symptoms may be mild, such as numbness in the limbs, or severe, such as paralysis or loss of vision. Although multiple sclerosis occurs most commonly in adults, estimates suggest that 8,000 to 10,000 children in the U.S. have the disease.
The origins of MS are unknown, but the disease is believed to be caused by a combination of factors. “A patient can have all the predisposing genetic factors necessary to develop MS and never develop the symptoms, perhaps because she never encounters the right environmental risk factors at the wrong time,” said James, who holds the Lou C. Kerr Chair in Biomedical Research at OMRF.
The researchers suspected that exposure to common childhood viruses might be one of those environmental risk factors. Examining biological samples taken from children with MS who volunteered for the study, the researchers found that three common childhood viruses had a potential impact on MS—but each in a different way.
“Cytomegalovirus, or CMV, is a common herpes virus that affects almost half of the population by 40 years of age,” James said. “We found that children who had been exposed to CMV had lower rates of MS than children who had not been exposed to the virus.”
On the other hand, children exposed to Epstein-Barr virus, which causes mononucleosis, were more likely to develop MS than those who had not. In the U.S., about half of all five-year-olds and more than 90 percent of adults have had the infection.
The effects of a third virus, herpes simplex virus 1, were dependent upon the patients’ underlying genetics, said James. Those with high risk factors in certain genes that control immune system responses were more likely than the general population to develop pediatric MS if exposed to the virus.
James cautioned that parents should not read too much into these results, as no single environmental factor will determine whether a child develops—or doesn’t develop—MS.
“We’re not saying that people should go out of their way to try and get their children exposed to select viruses,” James said. “Similarly, if your child contracts certain viruses, it’s no cause for alarm.”
At OMRF, James will continue to study how common viruses affect a person’s chances of developing MS and other autoimmune diseases such as lupus and rheumatoid arthritis. “As we uncover more links between genetic risk and environmental factors,” she said, “we hope to learn ways to train the immune system to lessen the chances of developing these diseases.”
Funding for the research was provided by grants from the National Institutes of Health and the National Multiple Sclerosis Society.