Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system that attacks the myelin sheaths protecting neurons in the brain and spinal cord. Until now, there has been no definitive cure to it.
A new study led by Harvard T.H. Chan School of Public Health researchers suggests that MS is likely caused by infection with the Epstein-Barr virus (EBV). EBV is a herpes virus that can cause infectious mononucleosis and establish a latent, lifelong host infection.
Setting up a causal connection between the virus and disease is quite difficult because EBV infects around 95% of adults, whereas MS is rare. The beginning of MS symptoms occurs roughly ten years after EBV disease.
To determine the association between MS and EBV, scientists conducted a study among more than 10 million young adults on active duty in the US military. Nine hundred fifty-five participants among them were diagnosed with MS during their service period.
Scientists biennially collected and analyzed serum samples. They then determined the soldier’s EBV status at the time of the 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 was 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.
Alberto Ascherio, professor of epidemiology and nutrition at Harvard Chan School and senior author of the study, said, “The hypothesis that EBV causes our group and others have investigated MS for several years, but this is the first study providing compelling evidence of causality.”
“The delay between EBV infection and the onset of MS may be partially due to the disease’s symptoms being undetected during the earliest stages and partially due to 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 prevent or treat EBV infection effectively, but an EBV vaccine or targeting the virus with EBV-specific antiviral drugs could ultimately prevent or cure MS.”
- Kjetil Bjornevik et al. Longitudinal analysis reveals high prevalence of Epstein-Barr virus-associated with multiple sclerosis. DOI: 10.1126/science.abj8222