Multiple sclerosis (MS) is likely caused by infection with the Epstein-Barr virus (EBV), according to a new Harvard University study.
“The hypothesis that EBV causes MS has been investigated by our group and others for several years, but this is the first study providing compelling evidence of causality,” said senior author Professor Alberto Ascherio. “This is a big step because it suggests that most MS cases could be prevented by stopping EBV infection, and that targeting EBV could lead to the discovery of a cure for MS.” The findings were published in Science.
Currently incurable, MS is a chronic inflammatory disease of the central nervous system that attacks the myelin sheaths protecting neurons in the brain and spinal cord. One of the top suspects for its cause is EBV, a herpes virus that can cause infectious mononucleosis and establishes a latent, lifelong infection of the host. Establishing a causal relationship between the virus and the disease has been hard because EBV infects approximately 95% of adults, MS is relatively rare, and the onset of MS symptoms begins about ten years after EBV infection. To determine the connection between EBV and MS, the researchers conducted a study among over 10 million US military personnel, identifying 955 who were diagnosed with MS during their period of service.
The team analysed serum samples taken twice a year by the military and determined the soldiers’ EBV status at time of first sample and the relationship between EBV infection and MS onset during the period of active duty. In this cohort, the risk of MS increased 32-fold after infection with EBV but remained unchanged after infection with other viruses. Serum levels of neurofilament light chain, a biomarker of the nerve degeneration typical in MS, increased only after EBV infection. The findings cannot be explained by any known risk factor for MS and suggest EBV as the leading cause of MS.
The delay between EBV infection and the onset of MS may be partly a result of the disease’s symptoms being undetected early on and partly the evolving relationship between EBV and the host’s immune system, which is repeatedly stimulated whenever latent virus reactivates.
“Currently there is no way to effectively prevent or treat EBV infection, but an EBV vaccine or targeting the virus with EBV-specific antiviral drugs could ultimately prevent or cure MS,” Prof Ascherio said.
Source: Harvard University