Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system of unknown etiology. We tested the hypothesis that MS is caused by Epstein-Barr virus (EBV) in a cohort comprising more than 10 million young adults on active duty in the US military, 955 of whom were diagnosed with MS during their period of service. Risk of MS increased 32-fold after infection with EBV but was not increased after infection with other viruses, including the similarly transmitted cytomegalovirus. Serum levels of neurofilament light chain, a biomarker of neuroaxonal degeneration, increased only after EBV seroconversion. These findings cannot be explained by any known risk factor for MS and suggest EBV as the leading cause of MS.

Elucidating the risk of Parkinson's disease: High expression of the α-synuclein gene ( SNCA ) is a risk factor for Parkinson's disease (PD), but certain drugs may mitigate this risk. Mittal et al. ran a small-molecule screen to identify compounds that regulate levels of SNCA expression and found that several β2-adrenoreceptor (β2AR) agonists reduced them (see the Perspective by Snyder). These compounds modulated epigenetic marks at the SNCA gene, effectively suppressing SNCA transcription. The authors looked at the pharmaceutical history of more than 4 million Norwegians over an 11-year period and found a reduced risk of PD among those that were taking one of the β2AR agonists for other medical problems. Science , this issue p. 891 ; see also p. 869

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease whose etiology is unknown. While most patients experience their first clinical symptoms of the disease around age 30 years,¹ the underlying pathophysiologic processes often occur long before these symptoms become apparent. The existence of this prodromal phase is revealed by the fact that at the time of the first demyelinating event, patients often present with evidence of central nervous system lesions in different stages of evolution,² indicating the past occurrence of subclinical demyelinating events. Further, one-third of individuals with incidental white-matter lesions consistent with MS but with no other clinical signs of the disease (radiologically isolated syndrome) go on to develop neurologic symptoms consistent with MS within 5 years,³ suggesting that the initial lesions were manifestations of MS. The unrecognized demyelinating events that precede the clinical disease onset could be asymptomatic or could cause symptoms too vague to suggest MS as a possible cause. The later occurrence is consistent with the observations in electronic databases that patients with MS more frequently sought medical care in the 5 years before the first demyelinating event compared with control individuals⁴ and more often reported a number of clinical symptoms and disturbances to their general practitioner up to 10 years before their MS diagnosis than control individuals.⁵

Objective: To investigate whether serum neurofilament light chain (NF-L) and chitinase 3-like 1 (CHI3L1) predict disease activity in relapsing-remitting MS (RRMS). Methods: A cohort of 85 patients with RRMS were followed for 2 years (6 months without disease-modifying treatment and 18 months with interferon-beta 1a [IFNB-1a]). Expanded Disability Status Scale was scored at baseline and every 6 months thereafter. MRI was performed at baseline and monthly for 9 months and then at months 12 and 24. Serum samples were collected at baseline and months 3, 6, 12, and 24. We analyzed the serum levels of NF-L using a single-molecule array assay and CHI3L1 by ELISA and estimated the association with clinical and MRI disease activity using mixed-effects models. Results: NF-L levels were significantly higher in patients with new T1 gadolinium-enhancing lesions (37.3 pg/mL, interquartile range [IQR] 25.9–52.4) and new T2 lesions (37.3 pg/mL, IQR 25.1–48.5) compared with those without (28.0 pg/mL, IQR 21.9–36.4, β = 1.258, p < 0.001 and 27.7 pg/mL, IQR 21.8–35.1, β = 1.251, p < 0.001, respectively). NF-L levels were associated with the presence of T1 gadolinium-enhanced lesions up to 2 months before (p < 0.001) and 1 month after (p = 0.009) the time of biomarker measurement. NF-L levels fell after initiation of IFNB-1a treatment (p < 0.001). Changes in CHI3L1 were not associated with clinical or MRI disease activity or interferon-beta 1a treatment. Conclusion: Serum NF-L could be a promising biomarker for subclinical MRI activity and treatment response in RRMS. In clinically stable patients, serum NF-L may offer an alternative to MRI monitoring for subclinical disease activity. ClinicalTrials.gov identifier: NCT00360906.