Berlin – The Epstein-Barr virus (EBV) could play a key role in the development of multiple sclerosis (MS). An infection with the widespread pathogen increases the risk of the autoimmune disease by a factor of about 32, according to American researchers in a recent study in the journal Science. “This work is the last piece of the puzzle,” said the head of the MS outpatient clinic at the Berlin Charité, Klemens Ruprecht. “The results practically leave no doubt as to a causal relationship.”
A connection between the virus and MS has been suspected for decades. In the so far incurable chronic inflammatory disease, which affects around 252,000 people in Germany, the immune system in the central nervous system destroys the protective myelin sheaths that surround the nerve fibers. This leads, among other things, to sensory disturbances, visual impairments and movement problems up to paralysis. MS is so different in its course, symptoms and therapeutic success from patient to patient that it is known as the “disease with a thousand faces”. About eight out of ten patients develop MS between the ages of 20 and 40.
The team led by Harvard University epidemiologist Alberto Ascherio examined the role of EBV in the development of MS on the basis of data from more than ten million military employees who were routinely screened for HIV every year.
US researchers: Pathogen is not just an accompanying phenomenon
955 participants were diagnosed with MS while serving in the military. In the stored blood samples from these patients, the researchers looked for antibodies against EBV in order to determine which pathogens the patients had been in contact with before the onset of the disease.
First, the researchers examined the last blood sample taken before the onset of the disease in 801 of the MS patients. All but one patient had antibodies to EBV, meaning they had previously been infected with EBV. The mean time between infection and diagnosis was 7.5 years.
The researchers were also able to show that in the people who were originally EBV-negative, no biomarkers for MS were initially detectable, but that these were then detectable in blood samples after the EBV infection before the onset of MS symptoms. This strongly suggests that the pathogen is a cause of the disease – and not just an accompanying phenomenon.
Other factors such as genetic susceptibility are also important
MS is to be seen as a rare late complication of an EBV infection, said the Charité expert Ruprecht. The current study says nothing about the mechanism. More than 90 percent of people will be infected with EBV, a herpes virus, but only a few will develop MS subsequently. “So other factors such as genetic susceptibility are also important for the development of the disease,” writes Ascherio’s team. An EBV infection is necessary, but not enough on its own to cause the disease.
The scientists emphasize that in order to protect against MS, one must target the EBV directly, for example through vaccinations. However, a vaccine is not yet in sight. Ruprecht added that it would take decades anyway before it would finally be clear whether such a vaccine would actually provide protection against MS.