According to a study led by Harvard T.H. Chan School of Public Health researchers, infection with Epstein-Barr virus may be a leading cause of multiple sclerosis.
Multiple sclerosis (MS) is a progressive, chronic inflammatory condition that affects the central nervous system. The current aetiology of MS is unknown. Researchers currently know that the demyelination in the brain and spinal cord is an immune-mediate process which is possibly triggered by a viral infection. The top candidate for infection is Epstein-Barr virus (EBV).
EBV is a human herpesvirus that after infection persists in B lymphocytes in a latent form. Proving causality between EBV and MS has been difficult. This is because EBV infects roughly 95% of adults, MS is a relatively rare condition and the onset of MS symptoms typically begins 10 years after EBV infection.
Testing the hypothesis
In a recent study, published in Science, researchers tested the hypothesis that MS is caused by EBV. The cohort studied comprised of over 10 million young adults on active duty in the US military. In total, 955 of these individuals were diagnosed with MS during their period of service.
The team analysed serum samples taken before the date of MS onset and determined the soldiers’ EBV status at the time of the first sample. They also established the relationship between EBV infection and MS onset during the period of active service.
In this cohort, the team found that the risk of MS increased 32-fold after infection with EBV but was unchanged after infection with other viruses, such as cytomegaloviruses. They also discovered that serum levels of a biomarker of neuroaxonal degeneration, neurofilament light chain, increased only after EBV infection.
The authors noted that these findings cannot be explained by any known risk factors for MS and thus suggest that EBV is a leading cause of MS. It is suspected that the delay between EBV infection and MS onset may be partially due to symptoms being undetected during the earliest stages and due to the evolving relationship between EBV and the host’s immune system.
While there are no effective prevention or treatment strategies for EBV infection, the development of an EBV vaccine or targeted antiviral drug in the future may ultimately help prevent or cure MS.
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