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May 4, 2009 (Seattle) -- Infection with Epstein-Barr virus appears to raise the risk of developing multiple sclerosis (MS), Boston researchers report.
The findings offer the strongest evidence to date implicating the virus as a trigger for the chronic progressive autoimmune disorder of the brain and spinal cord that affects more than 350,000 Americans, says Lily Jung, MD, medical director of the neurology clinic at the Swedish Neurology Institute in Seattle. Jung was not involved in the study.
Almost everyone is infected with Epstein-Barr virus (EBV) by the time they reach adulthood. Infection early in childhood typically does not cause severe illness, although infection that occurs in adolescence often leads to mononucleosis.
Researchers have searched for decades for a viral or bacterial agent that may trigger MS in people who are genetically susceptible. Epidemiology professor Alberto Ascherio, MD, DrPH, and colleagues at the Harvard School of Public Health in Boston have published several studies suggesting that the Epstein-Barr virus may be that agent.
The new study shows "that people who are not infected with Epstein-Barr virus do not get MS," Ascherio tells WebMD. "All 100% of people who got MS in our study were infected with Epstein-Barr virus," he says.
The findings were presented at the annual meeting of the American Academy of Neurology.
For the study, the researchers were granted access to more than 7 million blood specimens stored in the Department of Defense Serum Repository. The U.S. military maintains service members' medical records in electronic databases.
The researchers identified 305 service members who were diagnosed with MS plus had up to three blood samples taken prior to diagnosis.?Researchers compared these blood specimens with samples from 610 people who did not develop MS but were similar in age, race, sex, and other characteristics to those who did.
The initial blood sample tested negative for EBV-fighting antibodies in 10 (3.2%) of people who developed MS and 32 (5.3%) of people who didn't. Measuring antibodies, which are proteins produced by the body to fight specific infections, is one way to determine the intensity of infection.
Importantly, all 10 of the people who developed MS went on to test positive for Epstein-Barr virus antibodies before the onset of neurological symptoms, Ascherio says. They tested EBV-positive an average of four years before symptoms of the disorder first appeared.
In contrast, only 30% of the people who didn't develop MS later tested positive for Epstein-Barr virus.
Further analysis showed about a 50-fold increased risk of MS among people with the highest levels of EBV antibodies, compared with those with the lowest levels.
Ascherio says that Epstein-Barr virus most likely works in concert with environmental factors to trigger MS in people who are genetically vulnerable to the disease. "We think one of those factors may be vitamin D deficiency," he says.