Circulating U13 Small Nucleolar RNA as a Potential Biomarker in Huntington's Disease: A Pilot Study.

Plasma small RNAs have been recently explored as biomarkers in Huntington's disease (HD). We performed an exploratory study on nine HD patients, eight healthy subjects (HS), and five psychiatric patients (PP; to control for iatrogenic confounder effects) through an Affymetrix-Gene-Chip-miRNA-Array. We validated the results in an independent population of 23 HD, 15 pre-HD, 24 PP, 28 Alzheimer's disease (AD) patients (to control the disease-specificity) and 22 HS through real-time PCR. The microarray results showed higher levels of U13 small nucleolar RNA (SNORD13) in HD patients than controls (fold change 1.54, p = 0.003 HD vs. HS, and 1.44, p = 0.0026 HD vs. PP). In the validation population, a significant increase emerged with respect to both pre-HD and the control groups (p < 0.0001). SNORD13 correlated with the status of the mutant huntingtin carrier (r = 0.73; p < 0.001) and the disease duration (r = 0.59; p = 0.003). The receiver operating characteristic (ROC) curve analysis showed the high accuracy of SNORD13 in discriminating HD patients from other groups (AUC = 0.963). An interactome and pathway analysis on SNORD13 revealed enrichments for factors relevant to HD pathogenesis. We report the unprecedented finding of a potential disease-specific role of SNORD13 in HD. It seems to peripherally report a 'tipping point' in the pathogenic cascade at the neuronal level.

Altered intestinal permeability in patients with relapsing-remitting multiple sclerosis: A pilot study.

BACKGROUND: Alterations of intestinal permeability (IP) may contribute to the pathophysiology of immune-mediated diseases. OBJECTIVE: We investigated the possible association between IP changes and multiple sclerosis (MS). METHODS: We studied 22 patients with relapsing-remitting multiple sclerosis (RRMS) and 18 age- and sex-matched healthy donors (HDs), including five twin pairs (one concordant, and four discordant for disease). Measurement of lactulose (L) and mannitol (M; two non-metabolized sugars) levels in urine samples, after an oral load, allowed to quantify gut dysfunction. RESULTS: The proportion of participants with increased IP was significantly higher in patients than in HDs (16/22 (73%) versus 5/18 (28%); p = 0.001). Accordingly, the L/M urinary ratio showed significantly higher values in patients than in controls ( p = 0.0284). Urinary mannitol concentration was significantly lower in patients than in controls ( p = 0.022), suggesting a deficit of absorption from intestinal lumen. Such changes did not appear related to patients' clinical-radiological features. CONCLUSION: The relatively high proportion of IP changes in RR-MS patients seems to confirm our work hypothesis and warrants more work to confirm the result on a larger sample, and to understand the implications for related immunological disturbances and intestinal microbiota alterations. Our finding may also have relevance for oral treatments, recently introduced in clinical practice.

IFN-ß therapy modulates B-cell and monocyte crosstalk via TLR7 in multiple sclerosis patients.

The implication of B lymphocytes in the immunopathology of multiple sclerosis (MS) is increasingly recognized. Here we investigated the response of B cells to IFN-ß, a first-line therapy for relapsing-remitting MS patients, upon stimulation with TLR. IFN-ß restored the frequency of TLR7-induced IgM and IgG-secreting cells in MS patients to the levels found in healthy donors, showing a specific deficiency in the TLR7 pathway. However, no difference was observed in the TLR9 response. Furthermore, in MS-derived PBMCs, TLR7-mediated production of IL-6 and the ex vivo expression of B-cell-activating factor of the TNF family, two crucial cytokines for B-cell differentiation and survival, were induced by IFN-ß. Depletion of monocytes, which are key producers of both IL-6 and B-cell-activating factor of the TNF family, showed that TLR7-mediated B-cell differentiation into Ig-secreting cells is strongly dependent on the cross-talk between B cells and monocytes. Accordingly, impaired expression of TLR7 mRNA was observed in PBMCs and monocytes isolated from MS-affected individuals as compared with those from healthy donors, which was rescued by IFN-ß therapy. Collectively, our data unveil a novel TLR7-regulated mechanism in in vivo IFN-ß-stimulated whole leukocytes that could be exploited to define new TLR7-based strategies for the treatment of MS.

Increased CD8+ T cell responses to apoptotic T cell-associated antigens in multiple sclerosis.

BACKGROUND: Here, we evaluated the hypothesis that CD8+ T cell responses to caspase-cleaved antigens derived from effector T cells undergoing apoptosis, may contribute to multiple sclerosis (MS) immunopathology. METHODS: The percentage of autoreactive CD8+ T effector cells specific for various apoptotic T cell-associated self-epitopes (apoptotic epitopes) were detected in the peripheral blood and cerebrospinal fluid (CSF) by both enzyme-linked immunospot and dextramers of class I molecules complexed with relevant apoptotic epitopes. Moreover, the capacity of dextramer+ CD8+ T cells to produce interferon (IFN)-γ and/or interleukin (IL)-17 in response to the relevant apoptotic epitopes was evaluated by the intracellular cytokine staining. Cross-presentation assay of apoptotic T cells by dendritic cells was also evaluated ex vivo. RESULTS: We found that polyfunctional (IFN-γ and/or IL-17 producing) autoreactive CD8+ T cells specific for apoptotic epitopes were represented in MS patients with frequencies significantly higher than in healthy donors. These autoreactive CD8+ T cells with a strong potential to produce IFN-γ or IL-17 in response to the relevant apoptotic epitopes were significantly accumulated in the CSF from the same patients. In addition, the frequencies of these autoreactive CD8+ T cells correlated with the disease disability. Cross-presentation assay revealed that caspase-cleaved cellular proteins are required to activate apoptotic epitope-specific CD8+ T cells ex vivo. CONCLUSION: Taken together, these data indicate that apoptotic epitope-specific CD8+ T cells with strong inflammatory potential are recruited at the level of the inflammatory site, where they may be involved in MS immunopathology through the production of high levels of inflammatory cytokines.

Methylation-dependent PAD2 upregulation in multiple sclerosis peripheral blood.

BACKGROUND: Peptidylarginine deiminase 2 (PAD2) and peptidylarginine deiminase 4 (PAD4) are two members of PAD family which are over-expressed in the multiple sclerosis (MS) brain. Through its enzymatic activity PAD2 converts myelin basic protein (MBP) arginines into citrullines - an event that may favour autoimmunity - while peptidylarginine deiminase 4 (PAD4) is involved in chromatin remodelling. OBJECTIVES: Our aim was to verify whether an altered epigenetic control of PAD2, as already shown in the MS brain, can be observed in peripheral blood mononuclear cells (PBMCs) of patients with MS since some of these cells also synthesize MBP. METHODS: The expression of most suitable reference genes and of PAD2 and PAD4 was assessed by qPCR. Analysis of DNA methylation was performed by bisulfite method. RESULTS: The comparison of PAD2 expression level in PBMCs from patients with MS vs. healthy donors showed that, as well as in the white matter of MS patients, the enzyme is significantly upregulated in affected subjects. Methylation pattern analysis of a CpG island located in the PAD2 promoter showed that over-expression is associated with promoter demethylation. CONCLUSION: Defective regulation of PAD2 in the periphery, without the immunological shelter of the blood-brain barrier, may contribute to the development of the autoimmune responses in MS.

CD161(high)CD8+T cells bear pathogenetic potential in multiple sclerosis.

To identify differentially expressed genes in multiple sclerosis, microarrays were used in a stringent experimental setting-leukapheresis from disease-discordant monozygotic twins and gene expression profiling in CD4(+) and CD8(+) T-cell subsets. Disease-related differences emerged only in the CD8(+) T-cell subset. The five differentially expressed genes identified included killer cell lectin-like receptor subfamily B, member 1, also known as natural killer receptor protein 1a/CD161, presented by the International Multiple Sclerosis Genetics Consortium as one of the non-MHC candidate loci. Flow cytometric analysis on peripheral blood of healthy donors and patients with multiple sclerosis and rheumatoid arthritis confirmed an upregulation of CD161 at the protein level, showing also a significant excess of CD161(high)CD8(+) T cells in multiple sclerosis. This subset prevalently included chemokine (C-C motif) receptor 6(+), cytokine-producing, effector-memory T cells with proinflammatory profiles. It also included all circulating interleukin-17(+)CD8(+) T cells. In the CD161(high)CD8(+) subset, interleukin-12 facilitated proliferation and interferon-γ production, with CD161 acting as a co-stimulatory receptor. CD161(+)CD8(+)CD3(+) T cells producing interferon-γ were part of intralesional immune infiltrates and ectopic B cell follicles in autopsy multiple sclerosis brains. Variations of CD161 expression on CD8(+) T cells identify a subset of lymphocytes with proinflammatory characteristics that have not been previously reported in multiple sclerosis and are likely to contribute to disease immunopathology.

A nurse-led, telephone-based patient support program for improving adherence in patients with relapsing-remitting multiple sclerosis using interferon beta-1a: Lessons from a consumer-based survey on adveva® PSP.

Background: Evidence suggests that organizational models that provide care interventions including patient support programs may increase patient adherence to multiple sclerosis (MS) therapies by providing tailored symptom management, informational support, psychological and/or social support, lifestyle changes, emotional adjustment, health education, and tailored coaching, thus improving patients' overall quality of life across the disease course. Objective: The main objective of this study was to describe MS patients' self-reported experience of a nurse-led, telephone-based PSP and to explore its potential role in improving disease and therapy management skills. Methods: Survey data were analyzed from a subset of patients relapsing-remitting MS (RRMS) using interferon beta-1a already registered in the adveva® PSP from three Italian multiple sclerosis centers with a consolidated experience in RRMS disease, treatment management, and PSP programs. Results: In total, 244 patient data at baseline were analyzed, of which 115 had a follow-up of at least 6 months. Results from this study provide an early view into the role of this PSP in improving the patients reported overall experience regarding disease management and injectable therapy, thus potentially ameliorating treatment adherence and decreasing health care cost. Moreover, study findings confirm the role of providing a patient-focused support by addressing non-medication-related topics in the PSP consultations. Indeed, patients involved in the adveva® PSP program reported a better psychological status in the follow up as demonstrated by an increased optimism regarding their future, tolerance of disease uncertainty, and their perceived ability to benefit from external help and social support (informal caregivers). Conclusions: As such, it is reasonable to conclude that the involvement in the adveva® PSP and the PSP's assistance in guiding patients on proper treatment self-management techniques is of great value to patients as it might contribute to improving engagement in their health care journey in terms of perceived self-care skills, emotional coping toward the future and the unpredictability of the disease course and their general attitudes toward the injection itself, involving pain tolerance.

Proinflammatory mucosal-associated invariant CD8+ T cells react to gut flora yeasts and infiltrate multiple sclerosis brain.

The composition of the intestinal microbiota plays a critical role in shaping the immune system. Modern lifestyle, the inappropriate use of antibiotics, and exposure to pollution have significantly affected the composition of commensal microorganisms. The intestinal microbiota has been shown to sustain inappropriate autoimmune responses at distant sites in animal models of disease, and may also have a role in immune-mediated central nervous system (CNS) diseases such as multiple sclerosis (MS). We studied the composition of the gut mycobiota in fecal samples from 27 persons with MS (pwMS) and in 18 healthy donors (HD), including 5 pairs of homozygous twins discordant for MS. We found a tendency towards higher fungal abundance and richness in the MS group, and we observed that MS twins showed a higher rate of food-associated strains, such as Saccharomyces cerevisiae. We then found that in pwMS, a distinct population of cells with antibacterial and antifungal activity is expanded during the remitting phase and markedly decreases during clinically and/or radiologically active disease. These cells, named MAIT (mucosal-associated invariant T cells) lymphocytes, were significantly more activated in pwMS compared to HD in response to S. cerevisiae and Candida albicans strains isolated from fecal samples. This activation was also mediated by fungal-induced IL-23 secretion by innate immune cells. Finally, immunofluorescent stainings of MS post-mortem brain tissues from persons with the secondary progressive form of the disease showed that MAIT cells cross the blood-brain barrier (BBB) and produce pro-inflammatory cytokines in the brain. These results were in agreement with the hypothesis that dysbiosis of the gut microbiota might determine the inappropriate response of a subset of pathogenic mucosal T cells and favor the development of systemic inflammatory and autoimmune diseases.

Circulating hsa-miR-323b-3p in Huntington's Disease: A Pilot Study.

The momentum of gene therapy in Huntington's disease (HD) deserves biomarkers from easily accessible fluid. We planned a study to verify whether plasma miRNome may provide useful peripheral "reporter(s)" for the management of HD patients. We performed an exploratory microarray study of whole non-coding RNA profiles in plasma from nine patients with HD and 13 matched controls [eight healthy subjects (HS) and five psychiatric patients (PP) to minimize possible iatrogenic impact on the profile of non-coding RNAs]. We found an HD-specific signature: downregulation of hsa-miR-98 (fold change, -1.5, p = 0.0338 HD vs. HS, and fold change, 1.5, p = 0.0045 HD vs. PP) and upregulation of hsa-miR-323b-3p (fold change, 1.5, p = 0.0007 HD vs. HS, and fold change, 1.5, p = 0.0111 HD vs. PP). To validate this result in an independent cohort, we quantify by digital droplet PCR (ddPCR) the presence of the two microRNA in the plasma of 33 HD patients and 49 matched controls (25 HS and 24 PP patients). We were able to confirm that hsa-miR-323b-3p was upregulated in HD and premanifest HD vs. HS and PP: the median values (first-third quartile) were 4.1 (0.9-10.53) and 5.8 (1.9-10.70) vs. 0.69 (0.3-2.75) and 1.4 (0.78-2.70), respectively, p < 0.05. No significant difference was found for hsa-miR-98. To evaluate the biological plausibility of the hsa-miR-323b-3p as a component of the disease pathophysiology, we performed a bioinformatic analysis based on its targetome and the huntingtin (HTT) interactome. We found a statistically significant overconnectivity between the targetome of hsa-miR-323b-3p and the HTT interactome (p = 1.48e-08). Furthermore, there was a significant transcription regulation of the HTT interactome by the miR-323b-3p targetome (p = 0.02). The availability of handy, reproducible, and minimally invasive biomarkers coming from peripheral miRNome may be valuable to characterize the illness progression, to indicate new therapeutic targets, and to monitor the effect of disease-modifying treatments. Our data deserve further studies with larger sample size and longitudinal design.

miRNAs as Candidate Biomarker for the Accurate Detection of Atypical Endometrial Hyperplasia/Endometrial Intraepithelial Neoplasia.

Endometrial cancer is the most common gynecologic malignancy in developed countries. Estrogen-dependent tumors (type I, endometrioid) account for 80% of cases and non-estrogen-dependent (type II, non-endometrioid) account for the rest. Endometrial cancer type I is generally thought to develop via precursor lesions along with the increasing accumulation of molecular genetic alterations. Endometrial hyperplasia with atypia/Endometrial Intraepithelial Neoplasia is the least common type of hyperplasia but it is the type most likely to progress to type I cancer, whereas endometrial hyperplasia without atypia rarely progresses to carcinoma. MicroRNAs are a class of small, non-coding, single-stranded RNAs that negatively regulate gene expression mainly binding to 3'-untranslated region of target mRNAs. In the current study, we identified a microRNAs signature (miR-205, miR-146a, miR-1260b) able to discriminate between atypical and typical endometrial hyperplasia in two independent cohorts of patients. The identification of molecular markers that can distinguish between these two distinct pathological conditions is considered to be highly useful for the clinical management of patients because hyperplasia with an atypical change is associated with a higher risk of developing cancer. We show that the combination of miR-205, -146a, and -1260b has the best predictive power in discriminating these two conditions (>90%). With the aim to find a biological role for these three microRNAs, we focused our attention on a common putative target involved in endometrial carcinogenesis: the oncosuppressor gene SMAD4. We showed that miRs-146a,-205, and-1260b directly target SMAD4 and their enforced expression induced proliferation and migration of Endometrioid Cancer derived cell lines, Hec1a cells. These data suggest that microRNAs-mediated impairment of the TGF-ß pathway, due to inhibition of its effector molecule SMAD4, is a relevant molecular alteration in endometrial carcinoma development. Our findings show a potential diagnostic role of this microRNAs signature for the accurate diagnosis of Endometrial hyperplasia with atypia/Endometrial Intraepithelial Neoplasia and improve the understanding of their pivotal role in SMAD4 regulation.

Analysis of coding and non-coding transcriptome of peripheral B cells reveals an altered interferon response factor (IRF)-1 pathway in multiple sclerosis patients.

Several evidences emphasize B-cell pathogenic roles in multiple sclerosis (MS). We performed transcriptome analyses on peripheral B cells from therapy-free patients and age/sex-matched controls. Down-regulation of two transcripts (interferon response factor 1-IRF1, and C-X-C motif chemokine 10-CXCL10), belonging to the same pathway, was validated by RT-PCR in 26 patients and 21 controls. IRF1 and CXCL10 transcripts share potential seeding sequences for hsa-miR-424, that resulted up-regulated in MS patients. We confirmed this interaction and its functional effect by transfection experiments. Consistent findings indicate down-regulation of IRF1/CXCL10 axis, that may plausibly contribute to a pro-survival status of B cells in MS.

Gene expression profiles reveal homeostatic dynamics during interferon-beta therapy in multiple sclerosis.

Understanding the mechanisms that sustain the effects of disease modifying drugs in multiple sclerosis (MS) may help refine current therapies and improve our knowledge of disease pathogenesis. By using cDNA microarrays, we investigated gene expression in the peripheral blood mononuclear cells (PBMC) of 7 MS patients, at baseline (T0) as well as after 1 (T1) and 3 months (T3) of interferon beta-1a (IFN-beta-1a; Rebif 44 microg) therapy. Gene expression changes involved genes of both immunological and non-immunological significance. We validated IL-10 up-regulation, which is in accordance with previous reports, and other novel changes that underscore the capacity of IFN-beta to impair antigen presentation and migration of inflammatory elements into the central nervous system (up-regulation of filamin B and down-regulation of IL-16 and rab7). Overall, gene expression changes became less pronounced after 3 months of therapy, suggesting a homeostatic response to IFN-beta. This may be of use for the design of new treatment schedules.

Serum chemical elements and oxidative status in Alzheimer's disease, Parkinson disease and multiple sclerosis.

The role of some chemical elements in neurodegeneration was suggested by various authors. To obtain a profile of chemical elements and oxidative status in complex neurological diseases, an unbiased "omics" approach, i.e., quantification of 26 elements and oxidative stress parameters (serum oxidative status (SOS) and serum anti-oxidant capacity (SAC)), combined with multivariate statistical procedures (forward discriminant analysis, FDA) to analyse the vast amount of data, was applied to four groups of subjects (53 patients with Alzheimer's disease (AD), 71 with Parkinson disease (PD), 60 with multiple sclerosis (MS) and 124 healthy individuals). Descriptive statistics revealed numerous differences between each disease and healthy status. A concordant imbalance (reduction in Fe, Zn and SAC, and increase in SOS) was shared by AD, PD and MS. The FDA yielded three significant discriminant functions based on age, SOS, Ca, Fe, Si, Sn, V, Zn and Zr, and identified disease-specific profiles of element imbalances, thus showing the appropriateness of the "omics" approach. It may help assess the contribution of chemical elements and oxidative stress to disease causation and may provide complex predictors of disease evolution or treatment response.

EBNA2 binds to genomic intervals associated with multiple sclerosis and overlaps with vitamin D receptor occupancy.

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.

IFN-ß Therapy Regulates TLR7-Mediated Response in Plasmacytoid Dendritic Cells of Multiple Sclerosis Patients Influencing an Anti-Inflammatory Status.

Plasmacytoid dendritic cells (pDCs) display altered immune-phenotype in multiple sclerosis (MS) patients and are found actively recruited in postmortem MS brain lesions, implying that their immune regulation may represent an important aspect of MS pathogenesis. Because of the reported Toll-like receptor 7 (TLR7) implication in autoimmunity, in this study we characterized how IFN-ß therapy impacts on pDC activation to TLR7 triggering in MS patients, aspect only poorly investigated so far. In vivo IFN-ß administration regulates pDC functions in TLR7-treated peripheral blood mononuclear cell (PBMC) cultures differently from what is observed in isolated cells, suggesting that IFN-ß may activate inhibitory mechanisms in MS peripheral blood involved in turning off pDC response to dampen the ongoing inflammation. Indeed, IL-10, a key regulatory cytokine found increased upon TLR7 stimulation in in vivo IFN-ß-exposed PBMCs, directly reduced pDC-mediated IFN-α production. IFN-ß therapy also shaped T-cell responses by decreasing TLR7-induced pDC maturation and inducing T-cell inhibitory molecules. Accordingly, raised pDC-induced IL-27 and decreased IL-23 expression, together with high IL-10 level, contribute to inhibit Th17 cell differentiation. Our study uncovered a role for IFN-ß in the regulation of TLR7-mediated pDC responses in MS toward an anti-inflammatory phenotype opening new opportunities to better understand mechanisms of action of this drug in controlling MS immunopathogenesis.

Epstein-Barr virus genetic variants are associated with 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.

A mechanistic, stochastic model helps understand multiple sclerosis course and pathogenesis.

Heritable and nonheritable factors play a role in multiple sclerosis, but their effect size appears too small, explaining relatively little about disease etiology. Assuming that the factors that trigger the onset of the disease are, to some extent, also those that generate its remissions and relapses, we attempted to model the erratic behaviour of the disease course as observed on a dataset containing the time series of relapses and remissions of 70 patients free of disease-modifying therapies. We show that relapses and remissions follow exponential decaying distributions, excluding periodic recurrences and confirming that relapses manifest randomly in time. It is found that a mechanistic model with a random forcing describes in a satisfactory manner the occurrence of relapses and remissions, and the differences in the length of time spent in each one of the two states. This model may describe how interactions between "soft" etiologic factors occasionally reach the disease threshold thanks to comparably small external random perturbations. The model offers a new context to rethink key problems such as "missing heritability" and "hidden environmental structure" in the etiology of complex traits.

A "candidate-interactome" aggregate analysis of genome-wide association data in multiple sclerosis.

Though difficult, the study of gene-environment interactions in multifactorial diseases is crucial for interpreting the relevance of non-heritable factors and prevents from overlooking genetic associations with small but measurable effects. We propose a "candidate interactome" (i.e. a group of genes whose products are known to physically interact with environmental factors that may be relevant for disease pathogenesis) analysis of genome-wide association data in multiple sclerosis. We looked for statistical enrichment of associations among interactomes that, at the current state of knowledge, may be representative of gene-environment interactions of potential, uncertain or unlikely relevance for multiple sclerosis pathogenesis: Epstein-Barr virus, human immunodeficiency virus, hepatitis B virus, hepatitis C virus, cytomegalovirus, HHV8-Kaposi sarcoma, H1N1-influenza, JC virus, human innate immunity interactome for type I interferon, autoimmune regulator, vitamin D receptor, aryl hydrocarbon receptor and a panel of proteins targeted by 70 innate immune-modulating viral open reading frames from 30 viral species. Interactomes were either obtained from the literature or were manually curated. The P values of all single nucleotide polymorphism mapping to a given interactome were obtained from the last genome-wide association study of the International Multiple Sclerosis Genetics Consortium & the Wellcome Trust Case Control Consortium, 2. The interaction between genotype and Epstein Barr virus emerges as relevant for multiple sclerosis etiology. However, in line with recent data on the coexistence of common and unique strategies used by viruses to perturb the human molecular system, also other viruses have a similar potential, though probably less relevant in epidemiological terms.