April 10, 2006 -- Young adults with high levels of antibodies to Epstein-Barr virus appear to be at increased risk for developing multiple sclerosis later in life, new research suggests.
The findings add to the evidence implicating the common virus as a possible trigger for multiple sclerosis, a neurological disease of the central nervous system (brain, spinal cord, and optic nerves), which affects some 400,000 Americans.
Almost everyone is exposed to Epstein-Barr virus (EBV) by the time they reach adulthood. Infection early in childhood is common and usually does not cause severe illness, but infection that occurs in adolescence often leads to mononucleosis.
Researchers have searched for decades for a viral or bacterial agent that may trigger multiple sclerosis in people who are genetically susceptible. Epidemiology professor Alberto Ascherio, MD, and colleagues from the Harvard School of Public Health in Boston have published several studies suggesting that Epstein-Barr virus may be that agent.
"Collectively, the results of this and the previous studies provide compelling evidence that infection with EBV is a risk factor in the development of MS," Ascherio says.
'An Important Step'
For their latest study, the researchers were granted access to 100,000 blood specimens collected between 1965 and 1974 from members of the health plan Kaiser Permanente Northern California. The health plan also maintained its members' medical records in electronic databases.
A search of these records revealed that 42 people who provided blood specimens three and four decades prior to the study developed multiple sclerosis. Researchers compared these blood samples with samples from people who did not develop MS but had similar characteristics to those who did.
The samples from people who developed MS tended to have much higher levels of EBV-fighting antibodies. Measuring antibodies, which are proteins produced by the body to fight specific infections, is one way to determine the intensity of infection.
Most of the samples showed evidence of Epstein-Barr virus infection, but the analysis showed that a fourfold increase in antibodies was associated with a doubling of MS risk.
The findings were published today in an online edition of the June Archives of Neurology.
"MS is a disease that requires multiple steps, and it appears that infection with EBV is an important step," Ascherio tells WebMD.
Multiple Viral Triggers
But an MS expert who spoke to WebMD says he remains skeptical that Epstein-Barr virus is the single, infectious culprit responsible for the disease.
"There are probably a dozen or more infectious agents that have been proposed as causative in MS, and for each one there is some evidence to argue the case," says John Richert, MD, who is head of research and clinical programs for the National Multiple Sclerosis Society. "But no one has been able to come up with the definitive proof that their particular agent is the one."
Richert says it is widely accepted that environmental factors, specifically infections, trigger MS in people who are genetically vulnerable to the disease. But he adds that it is more likely that multiple triggers come into play.
"When we finally understand everything about MS, it may not be a single virus or other infectious agent that is the trigger," he says. "It may well be that different agents act as triggers in different people."
He notes that people with MS tend to generate higher immune responses to many different viruses, including those that cause mumps, German measles, and herpes. All of these viruses have been studied as potential causative agents for MS.
It is not clear from the study if the people who developed multiple sclerosis decades after their blood samples were taken also had elevated immune responses to these viruses.
Ascherio says he believes Epstein-Barr virus is a uniquely important viral trigger for MS. He points to the mounting evidence linking EBV to other autoimmune diseases, including lupus.
"I am not saying that other viruses might not be involved, but no other virus has displayed such a strong and persistent association with MS," he says. 'I think this certainly makes the case for stepping up efforts to develop an effective vaccine against this virus."