Epstein-Barr Virus Closely Tied to MS
Study adds evidence, but no smoking gun
TUESDAY, March 25, 2003 (HealthDayNews) -- A new study strengthens the case for a link between infection with the Epstein-Barr virus and multiple sclerosis, researchers say.
The case is not yet proven, says Dr. Alberto Ascherio, an associate professor of epidemiology at the Harvard School of Public Health who has worked to establish that link over the past few years. Ascherio is the lead author of a paper on the study in the March 26 issue of the Journal of the American Medical Association.
"We cannot say definitely, but this paper combined with the previous evidence does provide support for a causal relationship," Ascherio says.
Epstein-Barr virus, a member of the herpesvirus family, is ubiquitous. Experts say up to 95 percent of Americans are infected with it by age 40. It has been linked to a number of other diseases, most prominently mononucleosis, and also several cancers, such as lymphomas.
Ascherio speculates that the multiple sclerosis (MS)-virus link is due to an underlying genetic predisposition. In some individuals, he says, the virus somehow triggers an attack by the immune system on myelin, the protective covering of nerve fibers, causing problems ranging from numbness and tingling to paralysis.
The newly published study is by far the largest ever done, drawing on blood samples taken from more than 3 million U.S. military personnel between 1988 and 2000.
Lynn I. Levin and colleagues at the Army Physical Disability Agency looked at antibodies to the Epstein-Barr virus in 83 persons granted disability because of MS and in persons without the disease, matched for age, sex, ethnicity and date of blood sample collection. Epstein-Barr antibodies were consistently higher in those with MS, they report. The risk of developing MS was 34 times higher among those with the highest levels of antibodies to Epstein-Barr, the report says.
They also found a long time lag -- an average of four years -- between collection of the samples and development of MS.
Epstein-Barr joins the list of infectious agents that might be related to MS, says Timothy J. Coetzee, director of research training programs for the National Multiple Sclerosis Society. The list now includes HHV6, another herpesvirus, and chlamydia, a bacterium. The measles virus was once a suspect but has been cleared, Coetzee says.
"A causal relationship has yet to be established between any infectious agent and multiple sclerosis," he says. "With all of these infectious agents, there is no smoking gun."
Research should be pressed Coetzee says, because identification of an agent that causes the disease would mean that "you could start thinking rationally about devising some treatment. If it is a viral agent, you could think about antivirals. If it is a bacterium, you could think about antibiotics."
Such a treatment is a distant prospect now, he says.