A combination of three-dimensional MRI and translocator protein PET demonstrated enlarged and inflamed choroid plexuses in patients with multiple sclerosis (MS), representing a potential imaging ma... Background Choroid plexuses (CPs) have been suggested as a key gateway for inflammation in experimental autoimmune encephalitis, but in vivo evidence of their involvement in multiple sclerosis (MS)...

Objective: To determine the prognostic value of persisting neuroinflammation in multiple sclerosis (MS) lesions, we developed a 18 kDa‐translocator‐protein‐positron emission tomography (PET) ‐based classification of each lesion according to innate immune cell content and localization. We assessed the respective predictive value of lesion phenotype and diffuse inflammation on atrophy and disability progression over 2 years.Methods: Thirty‐six people with MS (disease duration 9 ± 6 years; 12 with relapsing–remitting, 13 with secondary‐progressive, and 11 with primary‐progressive) and 19 healthy controls (HCs) underwent a dynamic [¹⁸F]‐DPA‐714‐PET. At baseline and after 2 years, the patients also underwent a magnetic resonance imaging (MRI) and neurological examination. Based on a threshold of significant inflammation defined by a comparison of [¹⁸F]‐DPA‐714 binding between patients with MS and HCs, white matter lesions were classified as homogeneously active (active center), rim‐active (inactive center and active periphery), or nonactive. Longitudinal cortical atrophy was measured using Jacobian integration.Results: Patients with MS had higher innate inflammation in normal‐appearing white matter (NAWM) and cortex than HCs (respective standardized effect size = 1.15, 0.89, p = 0.003 and < 0.001). Out of 1,335 non‐gadolinium‐enhancing lesions, 53% were classified as homogeneously‐active (median = 17 per patient with MS), 6% rim‐active (median = 1 per patient with MS), and 41% non‐active (median = 14 per patient with MS). The number of homogenously‐active lesions was the strongest predictor of longitudinal changes, associating with cortical atrophy (β = 0.49, p = 0.023) and Expanded Disability Status Scale (EDSS) changes (β = 0.35, p = 0.023) over 2 years. NAWM and cortical binding were not associated to volumetric and clinical changes.Interpretation: The [¹⁸F]‐DPA‐714‐PET revealed that an unexpectedly high proportion of MS lesions have a smoldering component, which predicts atrophy and clinical progression. This suggests that following the acute phase, most lesions develop a chronic inflammatory component, promoting neurodegeneration and clinical progression. ANN NEUROL 2023;94:366–383

Background: Most twin studies of multiple sclerosis (MS) are inconclusive regarding the impact of genes and environment on disease susceptibility. In particular, high uncertainty exists about whether shared environmental factors are aetiologically relevant. Objective: To disentangle, with a reasonable degree of confidence, the relative contributions of heritability and of shared and unique environmental components of MS susceptibility. Methods: We performed a meta-analysis of previous twin studies. After a MEDLINE search, we selected eight twin studies in France, UK, Canada, Denmark, North America, Italy, Finland and Sweden. We conducted a biometric multi-group analysis under the liability-threshold model, by taking account of the study-specific ascertainment strategies and the population-specific prevalence rates of MS. Results: The meta-analytic estimates of tetrachoric correlations were 0.71 (95% confidence interval (CI): 0.67–0.74) in monozygotic pairs and 0.46 (95% CI: 0.41–0.50) in dizygotic pairs. The biometric multi-group model provided meta-analytic estimates of 0.50 (95% CI: 0.39–0.61) for heritability, 0.21 (95% CI: 0.11–0.30) for shared environmental component and 0.29 (95% CI: 0.26–0.33) for unique environmental component. Conclusion: Our results support the continuing efforts to identify unknown genetic factors that fill the gap of ‘missing heritability’; moreover, a ‘missing environmentality’ deserves future investigations into the role of non-heritable components that act as both shared and individual-specific exposures.

Epstein-Barr virus (EBV) is a non-heritable factor that associates with multiple sclerosis (MS). However its causal relationship with the disease is still unclear. The virus establishes a complex co-existence with the host that includes regulatory influences on gene expression. Hence, if EBV contributes to the pathogenesis of MS it may do so by interacting with disease predisposing genes. To verify this hypothesis we evaluated EBV nuclear antigen 2 (EBNA2, a protein that recent works by our and other groups have implicated in disease development) binding inside MS associated genomic intervals. We found that EBNA2 binding occurs within MS susceptibility sites more than expected by chance (factor of observed vs expected overlap [O/E] = 5.392-fold, p < 2.0e-05). This remains significant after controlling for multiple genomic confounders. We then asked whether this observation is significant per se or should also be viewed in the context of other disease relevant gene-environment interactions, such as those attributable to vitamin D. We therefore verified the overlap between EBNA2 genomic occupancy and vitamin D receptor (VDR) binding sites. EBNA2 shows a striking overlap with VDR binding sites (O/E = 96.16-fold, p < 2.0e-05), even after controlling for the chromatin accessibility state of shared regions (p <0.001). Furthermore, MS susceptibility regions are preferentially targeted by both EBNA2 and VDR than by EBNA2 alone (enrichment difference = 1.722-fold, p = 0.0267). Taken together, these findings demonstrate that EBV participates in the gene-environment interactions that predispose to MS.

In multiple sclerosis, spontaneous remyelination is generally incomplete and heterogenous across patients. A high heterogeneity in remyelination may also exist across lesions within the same individual, suggesting the presence of local factors interfering with myelin regeneration. In this study we explored in-vivo the regional distribution of myelin repair and investigated its relationship with neurodegeneration. We first took advantage of the myelin binding property of the amyloid radiotracer [¹¹C]PiB to conduct a longitudinal [¹¹C]PiB positron emission tomography study in an original cohort of 19 participants with a relapsing-remitting form of multiple sclerosis, followed-up over a period of 1-4 months. We then replicated our results on an independent cohort of 40 people with multiple sclerosis followed-up over one year with magnetization transfer imaging, an MRI metrics sensitive to myelin content. For each imaging method, voxel-wise maps of myelin content changes were generated according to modality-specific thresholds. We demonstrated a selective failure of remyelination in periventricular white matter lesions of people with multiple sclerosis in both cohorts. In both the original and the replication cohort, we estimated that the probability of demyelinated voxels to remyelinate over the follow-up increased significantly as a function of the distance from ventricular cerebro-spinal fluid. Enlarged choroid plexus, a recently discovered biomarker linked to neuroinflammation, was found to be associated with the periventricular failure of remyelination in the two cohorts (r=-0.79, p = 0.0018; r=-0.40, p = 0.045 respectively), suggesting a role of the brain-cerebrospinal fluid barrier in affecting myelin repair in surrounding tissues. In both cohorts, the failure of remyelination in periventricular white matter lesions was associated with lower thalamic volume (r = 0.86, p < 0.0001; r = 0.33; p = 0.069 respectively) an imaging marker of neurodegeneration. Interestingly, we also showed an association between the periventricular failure of remyelination and regional cortical atrophy that was mediated by the number of cortex-derived tracts passing through periventricular white matter lesions, especially in patients at the relapsing-remitting stage. Our findings demonstrate that lesion proximity to ventricles is associated with a failure of myelin repair and support the hypothesis that a selective periventricular remyelination failure in combination with the large number of tracts connecting periventricular lesions with cortical areas is a key mechanism contributing to cortical damage in multiple sclerosis.

Objective: We analyzed the Epstein-Barr nuclear antigen 2 (EBNA2) gene, which contains the most variable region of the viral genome, in persons with multiple sclerosis (MS) and control subjects to verify whether virus genetic variants are involved in disease development. Methods: A seminested PCR approach and Sanger sequencing were used to analyze EBNA2 in 53 patients and 38 matched healthy donors (HDs). High-throughput sequencing by Illumina MiSeq was also applied in a subgroup of donors (17 patients and 17 HDs). Patients underwent gadolinium-enhanced MRI and human leucocyte antigen typing. Results: MS risk significantly correlated with an excess of 1.2 allele (odds ratio [OR] = 5.13; 95% confidence interval [CI] 1.84–14.32; p = 0.016) and underrepresentation of 1.3B allele (OR = 0.23; 95% CI 0.08–0.51; p = 0.0006). We identified new genetic variants, mostly 1.2 allele- and MS-associated (especially amino acid variation at position 245; OR = 9.4; 95% CI 1.19–78.72; p = 0.0123). In all cases, the consensus sequence from deep sequencing confirmed Sanger sequencing (including the cosegregation of newly identified variants with known EBNA2 alleles) and showed that the extent of genotype intraindividual variability was higher than expected: rare EBNA2 variants were detected in all HDs and patients with MS (range 1–17 and 3–19, respectively). EBNA2 variants did not seem to correlate with human leucocyte antigen typing or clinical/MRI features. Conclusions: Our study unveils a strong association between Epstein-Barr virus genomic variants and MS, reinforcing the idea that Epstein-Barr virus contributes to disease development.