Epstein-Barr Virus Could Boost Multiple Sclerosis Risk
04.10.06, 12:00 AM ET
MONDAY, April 10 (HealthDay News) -- Exposure to the Epstein-Barr virus, which often causes mononucleosis in young adults, may double the risk of developing multiple sclerosis (MS) 15 to 20 years later, researchers report.
In the United States, as many as 96 percent of adults between 35 and 40 years of age have been infected with Epstein-Barr virus (EBV). Many children become infected with EBV, and these infections usually cause no symptoms or are indistinguishable from the other mild, brief illnesses of childhood. However, getting EBV during adolescence or young adulthood can result in infectious mononucleosis 35 percent to 50 percent of the time.
Although it remains unclear why EBV might increase the risk for multiple sclerosis, researchers suspect that the virus alters the body's immune system, making it more susceptible to MS. Their report appears in the April 10 online issue of the Archives of Neurology.
"There are previous studies showing an association between EBV and MS," said co-author Dr. Alberto Ascherio, an associate professor of nutrition and epidemiology at the Harvard School of Public Health. "What is new is that we have brought the temporal relationship back to 20 years before the onset of MS," he said.
Multiple sclerosis is thought to be an autoimmune disorder, in which the body's own immune system attacks and destroys the protective myelin sheath that surrounds nerve fibers. According to the National Multiple Sclerosis Society, over 400,000 Americans now have MS.
In their study, Ascherio and his colleagues collected data on patients who joined a health plan between 1965 and 1974 when they were just over 32 years old, on average.
Between 1995 and 1999, the researchers examined medical records and selected 42 people with MS, as well as 79 individuals matched for age and other factors, who did not have MS. Then they gathered and tested blood samples from each participant, looking for blood levels of antibodies against EBV, indicating exposure to the virus.
Of the people with MS, 36 women and six men experienced their first symptoms at an average age of 45 years -- an average 15 years after their blood was collected. These patients had significantly higher concentrations of EBV antibodies compared with those who didn't develop multiple sclerosis, the researchers found.
Patients who had four times the level of EBV antibodies were twice as likely to develop MS. These high levels of EBV antibodies were evident 15 to 20 years before the patients showed the first neurological symptoms of multiple sclerosis and remained higher afterward, Ascherio's team reported.
"This finding provides strong evidence that EBV is a strong risk factor for MS," Ascherio said.
Ascherio believes that developing an EBV vaccine could be an important step in reducing the risk of MS. "This finding makes the search for a vaccine even more important," he said. "A vaccine could dramatically reduce the risk of MS."
Ascherio also thinks that more work in understanding the relationship between EBV and multiple sclerosis could affect MS treatment. "So far, MS treatment ignores the association with EBV and is not directed to anything that has to do with the virus," he said.
One British expert agrees that vaccination against EBV may prevent multiple sclerosis in some people.
"This paper not only confirms the well-known association between EBV infection and MS, it also shows this association over a long period of time," said Dr. Abhijit Chaudhuri, a consultant neurologist at the Essex Center for Neurological Sciences at Oldchurch Hospital, Romford, Essex.
EBV is an extremely common and relatively harmless infection for many people, but it is also associated with lymphoma, nasopharyngeal cancer and chronic fatigue syndrome in some people, Chaudhuri said.
"The findings in this paper are consistent with my view that early life vaccination against EBV as a strategy to prevent MS needs consideration," Chaudhuri said. "However, one should not extrapolate this paper to conclude that MS is caused by EBV."
"It should be taken as further evidence for the role of complex changes that occur in the central nervous system after EBV infection that manifest as MS in predisposed individuals," Chaudhuri said.
For more on the Epstein-Barr virus, head to the U.S. National Institutes of Health.
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