Gender and the Sex Hormone Estradiol Affect Multiple Sclerosis Risk Gene Expression in Epstein-Barr Virus-Infected B Cells.

Multiple Sclerosis (MS) is a complex immune-mediated disease of the central nervous system. Treatment is based on immunomodulation, including specifically targeting B cells. B cells are the main host for the Epstein-Barr Virus (EBV), which has been described as necessary for MS development. Over 200 genetic loci have been identified as increasing susceptibility to MS. Many MS risk genes have altered expression in EBV infected B cells, dependent on the risk genotype, and are themselves regulated by the EBV transcription factor EBNA2. Females are 2-3 times more likely to develop MS than males. We investigated if MS risk loci might mediate the gender imbalance in MS. From a large public dataset, we identified gender-specific associations with EBV traits, and MS risk SNP/gene pairs with gender differences in their associations with gene expression. Some of these genes also showed gender differences in correlation of gene expression level with Estrogen Receptor 2. To test if estrogens may drive these gender specific differences, we cultured EBV infected B cells (lymphoblastoid cell lines, LCLs), in medium depleted of serum to remove the effects of sex hormones as well as the estrogenic effect of phenol red, and then supplemented with estrogen (100 nM estradiol). Estradiol treatment altered MS risk gene expression, LCL proliferation rate, EBV DNA copy number and EBNA2 expression in a sex-dependent manner. Together, these data indicate that there are estrogen-mediated gender-specific differences in MS risk gene expression and EBV functions. This may in turn contribute to gender differences in host response to EBV and to MS susceptibility.

Expression of CYP24A1 and other multiple sclerosis risk genes in peripheral blood indicates response to vitamin D in homeostatic and inflammatory conditions.

Although genetic and epidemiological evidence indicates vitamin D insufficiency contributes to multiple sclerosis (MS), and serum levels of vitamin D increase on treatment with cholecalciferol, recent metanalyses indicate that this vitamin D form does not ameliorate disease. Genetic variation in genes regulating vitamin D, and regulated by vitamin D, affect MS risk. We evaluated if the expression of vitamin D responsive MS risk genes could be used to assess vitamin D response in immune cells. Peripheral blood mononuclear cells (PBMCs) were isolated from healthy controls and people with MS treated with dimethyl fumarate. We assayed changes in expression of vitamin D responsive MS risk (VDRMS) genes in response to treatment with 25 hydroxy vitamin D in the presence or absence of inflammatory stimuli. Expression of CYP24A1 and other VDRMS genes was significantly altered in PBMCs treated with vitamin D in the homeostatic and inflammatory models. Gene expression in MS samples had similar responses to controls, but lower initial expression of the risk genes. Vitamin D treatment abrogated these differences. Expression of CYP24A1 and other MS risk genes in blood immune cells indicate vitamin D response and could enable assessment of immunological response to vitamin D in clinical trials and on therapy.

The Interaction of Human and Epstein-Barr Virus miRNAs with Multiple Sclerosis Risk Loci.

Although the causes of Multiple Sclerosis (MS) still remain largely unknown, multiple lines of evidence suggest that Epstein-Barr virus (EBV) infection may contribute to the development of MS. Here, we aimed to identify the potential contribution of EBV-encoded and host cellular miRNAs to MS pathogenesis. We identified differentially expressed host miRNAs in EBV infected B cells (LCLs) and putative host/EBV miRNA interactions with MS risk loci. We estimated the genotype effect of MS risk loci on the identified putative miRNA:mRNA interactions in silico. We found that the protective allele of MS risk SNP rs4808760 reduces the expression of hsa-mir-3188-3p. In addition, our analysis suggests that hsa-let-7b-5p may interact with ZC3HAV1 differently in LCLs compared to B cells. In vitro assays indicated that the protective allele of MS risk SNP rs10271373 increases ZC3HAV1 expression in LCLs, but not in B cells. The higher expression for the protective allele in LCLs is consistent with increased IFN response via ZC3HAV1 and so decreased immune evasion by EBV. Taken together, this provides evidence that EBV infection dysregulates the B cell miRNA machinery, including MS risk miRNAs, which may contribute to MS pathogenesis via interaction with MS risk genes either directly or indirectly.

Age-dependent VDR peak DNA methylation as a mechanism for latitude-dependent multiple sclerosis risk.

BACKGROUND: The mechanisms linking UV radiation and vitamin D exposure to the risk of acquiring the latitude and critical period-dependent autoimmune disease, multiple sclerosis, is unclear. We examined the effect of vitamin D on DNA methylation and DNA methylation at vitamin D receptor binding sites in adult and paediatric myeloid cells. This was accomplished through differentiating CD34+ haematopoietic progenitors into CD14+ mononuclear phagocytes, in the presence and absence of calcitriol. RESULTS: Few DNA methylation changes occurred in cells treated with calcitriol. However, several VDR-binding sites demonstrated increased DNA methylation in cells of adult origin when compared to cells of paediatric origin. This phenomenon was not observed at other transcription factor binding sites. Genes associated with these sites were enriched for intracellular signalling and cell activation pathways involved in myeloid cell differentiation and adaptive immune system regulation. CONCLUSION: These results suggest vitamin D exposure at critical periods during development may contribute to latitude-related differences in autoimmune disease incidence.

Vitamin D and its Effects on DNA Methylation in Development, Aging, and Disease.

DNA methylation is increasingly being recognized as a mechanism through which environmental exposures confer disease risk. Several studies have examined the association between vitamin D and changes in DNA methylation in areas as diverse as human and animal development, genomic stability, chronic disease risk, and malignancy. In many cases, they have demonstrated clear associations between vitamin D and DNA methylation in candidate disease pathways. Despite this, a clear understanding of the mechanisms by which these factors interact is unclear. This paper reviews the current understanding of the effects of vitamin D on DNA methylation. In light of current knowledge in the field, the potential mechanisms mediating vitamin D effects on DNA methylation are discussed, as are the limiting factors and future avenues for research into this exciting area.

Regulation of the methylome in differentiation from adult stem cells may underpin vitamin D risk in MS.

Multiple lines of evidence indicate Multiple Sclerosis (MS) is affected by vitamin D. This effect may be mediated by methylation in immune cell progenitors. We aimed to determine (1) if haematopoietic stem cell methylation constrains methylation in daughter cells and is variable between individuals, and (2) the interaction of methylation with the vitamin D receptor binding sites. We interrogated genomic methylation levels from matching purified CD34+ haematopoietic stem cells and progeny CD14+ monocytes and CD56+ NK cells from 11 individuals using modified reduced representation bisulfite sequencing. Differential methylation of Vitamin D Receptor binding sites and MS risk genes was assessed from this and using pyrosequencing for the vitamin D regulated MS risk gene ZMIZ1. Although DNA methylation states at CpG islands and other sites are almost entirely recapitulated between progenitor and progeny immune cells, significant variation was detected at some regions between cell subsets and individuals; including around the MS risk genes HLA DRB1 and the vitamin D repressor NCOR2. Methylation of the vitamin D responsive MS risk gene ZMIZ1 was associated with risk SNP and disease. We conclude that DNA methylation settings in adult haematopoietic stem cells may contribute to individual variation in vitamin D responses in immune cells.

The interaction of Multiple Sclerosis risk loci with Epstein-Barr virus phenotypes implicates the virus in pathogenesis.

Translating the findings of genome wide association studies (GWAS) to new therapies requires identification of the relevant immunological contexts to interrogate for genetic effects. In one of the largest GWAS, more than 200 risk loci have been identified for Multiple Sclerosis (MS) susceptibility. Infection with Epstein-Barr virus (EBV) appears to be necessary for the development of Multiple Sclerosis (MS). Many MS risk loci are associated with altered gene expression in EBV infected B cells (LCLs). We have interrogated this immunological context to identify interaction between MS risk loci and EBV DNA copy number, intrinsic growth rate and EBV encoded miRNA expression. The EBV DNA copy number was associated with significantly more risk alleles for MS than for other diseases or traits. EBV miRNAs BART4-3p and BART3-5p were highly associated with EBV DNA copy number and MS risk loci. The poliovirus receptor (PVR) risk SNP was associated with EBV DNA copy number, PVR and miRNA expression. Targeting EBV miRNAs BART4-3p and BART3-5p, and the gene PVR, may provide therapeutic benefit in MS. This study also indicates how immunological context and risk loci interactions can be exploited to validate and develop novel therapeutic approaches.

Transcribed B lymphocyte genes and multiple sclerosis risk genes are underrepresented in Epstein-Barr Virus hypomethylated regions.

Epstein-Barr Virus (EBV) infection appears to be necessary for the development of Multiple Sclerosis (MS), although the specific mechanisms are unknown. More than 200 single-nucleotide polymorphisms (SNPs) are known to be associated with the risk of developing MS. About a quarter of these are also highly associated with proximal gene expression in B cells infected with EBV (lymphoblastoid cell lines-LCLs). The DNA of LCLs is hypomethylated compared with both uninfected and activated B cells. Since methylation can affect gene expression, and so cell differentiation and immune evasion, we hypothesised that EBV-driven hypomethylation may affect the interaction between EBV infection and MS. We interrogated an existing dataset comprising three individuals with whole-genome bisulfite sequencing data from EBV transformed B cells and CD40L-activated B cells. DNA methylation surrounding MS risk SNPs associated with gene expression in LCLs (LCLeQTL) was less likely to be hypomethylated than randomly selected chromosomal regions. Differential methylation was independent of genomic features such as promoter regions, but genes preferentially expressed in EBV-infected B cells, including the LCLeQTL genes, were underrepresented in the hypomethylated regions. Our data does not indicate MS genetic risk is affected by EBV hypomethylation.

Evidence from genome wide association studies implicates reduced control of Epstein-Barr virus infection in multiple sclerosis susceptibility.

BACKGROUND: Genome wide association studies have identified > 200 susceptibility loci accounting for much of the heritability of multiple sclerosis (MS). Epstein-Barr virus (EBV), a memory B cell tropic virus, has been identified as necessary but not sufficient for development of MS. The molecular and immunological basis for this has not been established. Infected B cell proliferation is driven by signalling through the EBV produced cell surface protein LMP1, a homologue of the MS risk gene CD40. METHODS: We have investigated transcriptomes of B cells and EBV-infected B cells at Latency III (LCLs) and identified MS risk genes with altered expression on infection and with expression levels associated with the MS risk genotype (LCLeQTLs). The association of LCLeQTL genomic burden with EBV phenotypes in vitro and in vivo was examined. The risk genotype effect on LCL proliferation with CD40 stimulation was assessed. RESULTS: These LCLeQTL MS risk SNP:gene pairs (47 identified) were over-represented in genes dysregulated between B and LCLs (p < 1.53 × 10-4), and as target loci of the EBV transcription factor EBNA2 (p < 3.17 × 10-16). Overall genetic burden of LCLeQTLs was associated with some EBV phenotypes but not others. Stimulation of the CD40 pathway by CD40L reduced LCL proliferation (p < 0.001), dependent on CD40 and TRAF3 MS risk genotypes. Both CD40 and TRAF3 risk SNPs are in binding sites for the EBV transcription factor EBNA2, with expression of each correlated with EBNA2 expression dependent on genotype. CONCLUSIONS: These data indicate targeting EBV may be of therapeutic benefit in MS.

Short-term changes in frequencies of circulating leukocytes associated with narrowband UVB phototherapy in people with clinically isolated syndrome.

Clinically isolated syndrome (CIS) is the earliest clinical episode in multiple sclerosis (MS). Low environmental exposure to UV radiation is implicated in risk of developing MS, and therefore, narrowband UVB phototherapy might delay progression to MS in people with CIS. Twenty individuals with CIS were recruited, and half were randomised to receive 24 sessions of narrowband UVB phototherapy over a period of 8 weeks. Here, the effects of narrowband UVB phototherapy on the frequencies of circulating immune cells and immunoglobulin levels after phototherapy are reported. Peripheral blood samples for all participants were collected at baseline, and 1, 2, 3, 6 and 12 months after enrolment. An extensive panel of leukocyte populations, including subsets of T cells, B cells, monocytes, dendritic cells, and natural killer cells were examined in phototherapy-treated and control participants, and immunoglobulin levels measured in serum. There were significant short-term increases in the frequency of naïve B cells, intermediate monocytes, and fraction III FoxP3+ T regulatory cells, and decreases in switched memory B cells and classical monocytes in phototherapy-treated individuals. Since B cells are increasingly targeted by MS therapies, the effects of narrowband UVB phototherapy in people with MS should be investigated further.

The latitude-dependent autoimmune disease risk genes ZMIZ1 and IRF8 regulate mononuclear phagocytic cell differentiation in response to vitamin D.

Epidemiological, molecular and genetic studies have indicated that high serum vitamin D levels are associated with lower risk of several autoimmune diseases. The vitamin D receptor (VDR) binding sites in monocytes and dendritic cells (DCs) are more common in risk genes for diseases with latitude dependence than in risk genes for other diseases. The transcription factor genes Zinc finger MIZ domain-containing protein 1 (ZMIZ1) and interferon regulatory factor 8 (IRF8)-risk genes for many of these diseases-have VDR binding peaks co-incident with the risk single nucleotide polymorphisms (SNPs). We show these genes are responsive to vitamin D: ZMIZ1 expression increased and IRF8 expression decreased, and this response was affected by genotype in different cell subsets. The IL10/IL12 ratio in tolerogenic DCs increased with vitamin D. These data indicate that vitamin D regulation of ZMIZ1 and IRF8 in DCs and monocytes contribute to latitude-dependent autoimmune disease risk.

Tryptophan and arginine catabolic enzymes and regulatory cytokines in clinically isolated syndrome and multiple sclerosis.

OBJECTIVES: Clinically isolated syndrome (CIS) is the earliest clinical episode in multiple sclerosis (MS). A study of circulating cells from patients with CIS may help us understand the transition to, and processes associated with, the development of MS. METHODS: As immune cell activity can be determined by flux through metabolic pathways, the mRNA expression of l-tryptophan- and l-arginine-catabolising enzymes, indoleamine 2,3-dioxygenase (IDO) 1 and IDO2 and arginase (ARG) 1 and ARG2, respectively, was compared between peripheral blood mononuclear cells (PBMCs) from healthy controls, and patients with CIS and definite MS. As one measure of cell function, cytokine mRNA levels were analysed directly ex vivo and in cells after culture for 4 h in the absence of regulatory factors in autologous serum. RESULTS: When measured directly ex vivo, the expression of IDO and ARG was greater in cells from patients with CIS and MS than cells from healthy controls. Although not linked to IDO and ARG expression, PBMCs from the CIS patients were characterised by low IL-10 and TGFB mRNA levels and not by greater expression of proinflammatory cytokines. When the cells were cultured for 4 h without autologous serum, pro- and anti-inflammatory cytokine mRNA levels positively correlated with IDO1 expression, and TGFB mRNA levels correlated with ARG1 expression. CONCLUSION: Higher IDO and ARG expression in CIS and MS provides one sustained homeostatic mechanism to control MS-associated inflammation. However, potent extrinsic mediators in serum may regulate immune cell function in CIS and associations between IDO, ARG and cytokine expression.

Higher Serum Immunoglobulin G3 Levels May Predict the Development of Multiple Sclerosis in Individuals With Clinically Isolated Syndrome.

Clinically isolated syndrome (CIS) is a first episode of neurological symptoms that may precede a diagnosis of multiple sclerosis (MS). Therefore, studying individuals with CIS may lead to breakthroughs in understanding the development and pathogenesis of MS. In this study, serum levels of immunoglobulin (Ig)G, IgA, IgM, and IgG1-4 were measured in 20 people with CIS and compared with those in 10 healthy controls (HC) and 8 people with MS. Serum Ig levels in individuals with CIS were compared with (a) the time to their conversion from CIS to MS, (b) serum levels of antibodies to Epstein-Barr virus, (c) frequencies of T regulatory (Treg), T follicular regulatory (Tfr), and B cell subsets, and (d) Treg/Tfr expression of Helios. Serum IgG, IgM, and IgG2 levels were significantly lower in people with CIS than HC, and IgG, IgM, and IgG1 levels were significantly lower in people with CIS than MS. After adjusting for age, sex, and serum 25(OH) vitamin D3 [25(OH)D] levels, CIS was associated with lower serum levels of IgG and IgG2 compared with HC (p = 0.001 and p < 0.001, respectively). People with MS had lower IgG2 levels (p < 0.001) and IgG2 proportions (%IgG; p = 0.007) compared with HC. After adjusting for age, sex, and 25(OH)D, these outcomes remained, in addition to lower serum IgA levels (p = 0.01) and increased IgG3 levels (p = 0.053) in people with MS compared with HC. Furthermore, serum from people with MS had increased proportions of IgG1 and IgG3 (p = 0.03 and p = 0.02, respectively), decreased proportions of IgG2 (p = 0.007), and greater ratios of "upstream" to "downstream" IgG subclasses (p = 0.001) compared with HC. Serum IgG3 proportions (%IgG) from people with CIS correlated with the frequency of plasmablasts in peripheral blood (p = 0.02). Expression of Helios by Treg and Tfr cell subsets from individuals with CIS correlated with levels of serum IgG2 and IgG4. IgG3 levels and proportions of IgG3 (%IgG) in serum at CIS diagnosis were inversely correlated with the time until conversion to MS (p = 0.018 and p < 0.001, respectively), suggesting they may be useful prognostic markers of individuals with CIS who rapidly convert to MS.

A randomised, controlled clinical trial of narrowband UVB phototherapy for clinically isolated syndrome: The PhoCIS study.

BACKGROUND: The natural history of multiple sclerosis (MS) typically presents with the clinically isolated syndrome (CIS), an episode of neurological symptoms caused by central nervous system inflammation or demyelination that does not fulfil the diagnostic criteria for MS. OBJECTIVE: As preclinical studies have suggested that exposure to ultraviolet radiation (UVR) could regulate the development of MS, the Phototherapy for CIS (PhoCIS trial) was established to examine the effects of narrowband UVB phototherapy on patients with CIS, and their conversion to MS. METHODS: Of the 20 participants, half received 24 sessions of narrowband UVB exposure over eight weeks; participants in both arms were followed for 12 months. All participants were supplemented to 25-hydroxyvitamin D3 levels of >80 nmol/l. RESULTS: By 12 months, 100% of those in the no phototherapy arm and 70% in the phototherapy arm had converted to MS, although this difference was not statistically significant. CONCLUSION: This study provides a basis for further studies to determine if there are any benefits of the therapeutic effects of narrowband UVB radiation on MS progression.

Association of Regulatory T-Cell Expansion With Progression of Amyotrophic Lateral Sclerosis: A Study of Humans and a Transgenic Mouse Model.

Importance: Neuroinflammation appears to be a key modulator of disease progression in amyotrophic lateral sclerosis (ALS) and thereby a promising therapeutic target. The CD4+Foxp3+ regulatory T-cells (Tregs) infiltrating into the central nervous system suppress neuroinflammation and promote the activation of neuroprotective microglia in mouse models of ALS. To our knowledge, the therapeutic association of host Treg expansion with ALS progression has not been studied in vivo. Objective: To assess the role of Tregs in regulating the pathophysiology of ALS in humans and the therapeutic outcome of increasing Treg activity in a mouse model of the disease. Design, Setting, and Participants: This prospective multicenter human and animal study was performed in hospitals, outpatient clinics, and research institutes. Clinical and function assessment, as well as immunological studies, were undertaken in 33 patients with sporadic ALS, and results were compared with 38 healthy control participants who were consecutively recruited from the multidisciplinary ALS clinic at Westmead Hospital between February 1, 2013, and December 31, 2014. All data analysis on patients with ALS was undertaken between January 2015 and December 2016. Subsequently, we implemented a novel approach to amplify the endogenous Treg population using peripheral injections of interleukin 2/interleukin 2 monoclonal antibody complexes (IL-2c) in transgenic mice that expressed mutant superoxide dismutase 1 (SOD1), a gene associated with motor neuron degeneration. Main Outcomes and Measures: In patients with ALS, Treg levels were determined and then correlated with disease progression. Circulating T-cell populations, motor neuron size, glial cell activation, and T-cell and microglial gene expression in spinal cords were determined in SOD1G93A mice, as well as the association of Treg amplification with disease onset and survival time in mice. Results: The cohort of patients with ALS included 24 male patients and 9 female patients (mean [SD] age at assessment, 58.9 [10.9] years). There was an inverse correlation between total Treg levels (including the effector CD45RO+ subset) and rate of disease progression (R = -0.40, P = .002). Expansion of the effector Treg population in the SOD1G93A mice was associated with a significant slowing of disease progression, which was accompanied by an increase in survival time (IL-2c-treated mice: mean [SD], 160.6 [10.8] days; control mice: mean [SD], 144.9 [10.6] days; P = .003). Importantly, Treg expansion was associated with preserved motor neuron soma size and marked suppression of astrocytic and microglial immunoreactivity in the spinal cords of SOD1G93A mice, as well as elevated neurotrophic factor gene expression in spinal cord and peripheral nerves. Conclusions and Relevance: These findings establish a neuroprotective effect of Tregs, possibly mediated by suppression of toxic neuroinflammation in the central nervous system. Strategies aimed at enhancing the Treg population and neuroprotective activity from the periphery may prove therapeutically useful for patients with ALS.

GPR65 inhibits experimental autoimmune encephalomyelitis through CD4+ T cell independent mechanisms that include effects on iNKT cells.

The G protein-coupled receptor 65 (GPR65) gene has been genetically associated with several autoimmune diseases, including multiple sclerosis (MS). GPR65 is predominantly expressed in lymphoid organs and is activated by extracellular protons. In this study, we tested whether GPR65 plays a functional role in demyelinating autoimmune disease. Using a murine model of MS, experimental autoimmune encephalomyelitis (EAE), we found that Gpr65-deficient mice develop exacerbated disease. CD4+ helper T cells are key drivers of EAE pathogenesis, however, Gpr65 deficiency in these cells did not contribute to the observed exacerbated disease. Instead, Gpr65 expression levels were found to be highest on invariant natural killer T (iNKT) cells. EAE severity in Gpr65-deficient mice was normalized in the absence of iNKT cells (CD1d-deficient mice), suggesting that GPR65 signals in iNKT cells are important for suppressing autoimmune disease. These findings provide functional support for the genetic association of GPR65 with MS and demonstrate GPR65 signals suppress autoimmune activity in EAE.

Altered regulatory T-cell fractions and Helios expression in clinically isolated syndrome: clues to the development of multiple sclerosis.

Development of multiple sclerosis (MS) is frequently preceded by an acute or subacute neurological disturbance referred to as clinically isolated syndrome (CIS). The specific immunological disturbances present in CIS remain underexamined. This study analysed peripheral blood mononuclear cells from n=18 treatment-naive individuals with recently diagnosed CIS (<120 days) for disturbances in the phenotype of T regulatory (Treg), follicular T regulatory (Tfr), T helper (Th), follicular T helper (Tfh) and B cells. Relative to healthy controls (n=19), CIS was associated with lower proportions of suppressive CD45RA+FoxP3lo Treg and Tfr cells and greater proportions of non-suppressive CD45RA-FoxP3lo and Th17-like Treg and Tfr. Lower Helios expression (maen fluorescent intensity) was measured across all Treg and Tfr fractions in the CIS group, suggesting less potent regulatory function. Greater frequencies of activated, efficient B-cell helper Tfh subsets and a trend for a higher proportion of IgD-CD27- B cells was also detected in the CIS group, characteristics that were positively correlated with Treg and Tfr Helios expression. These results indicate that Treg and Tfr impairment is an early feature in MS.

Evolving Identification of Blood Cells Associated with Clinically Isolated Syndrome: Importance of Time since Clinical Presentation and Diagnostic MRI.

It is not clear how the profile of immune cells in peripheral blood differs between patients with clinically isolated syndrome (CIS) and healthy controls (HC). This study aimed to identify a CIS peripheral blood signature that may provide clues for potential immunomodulatory approaches early in disease. Peripheral blood mononuclear cells (PBMCs) were collected from 18 people with CIS, 19 HC and 13 individuals with other demyelinating conditions (ODC) including multiple sclerosis (MS). Individuals with CIS separated into two groups, namely those with early (≤14 days post-diagnostic magnetic resonance imaging (MRI); n = 6) and late (≥27 days; n = 12) blood sampling. Transitional B cells were increased in the blood of CIS patients independently of when blood was taken. However, there were two time-dependent effects found in the late CIS group relative to HC, including decreased CD56bright NK cells, which correlated significantly with time since MRI, and increased CD141+ myeloid dendritic cell (mDC2) frequencies. Higher CD1c+ B cells and lower non-classical monocyte frequencies were characteristic of more recent demyelinating disease activity (ODC and early CIS). Analysing cell populations by time since symptoms (subjective) and diagnostic MRI (objective) may contribute to understanding CIS.

The Multiple Sclerosis (MS) Genetic Risk Factors Indicate both Acquired and Innate Immune Cell Subsets Contribute to MS Pathogenesis and Identify Novel Therapeutic Opportunities.

Multiple sclerosis (MS) is known to be a partially heritable autoimmune disease. The risk of developing MS increases from typically 1 in 1,000 in the normal population to 1 in 4 or so for identical twins where one twin is affected. Much of this heritability is now explained and is due almost entirely to genes affecting the immune response. The largest and first identified genetic risk factor is an allele from the MHC class II HLA-DRB1 gene, HLA-DRB1*15:01, which increases risk about threefold. The HLA-DRB1 gene is expressed in antigen-presenting cells, and its protein functions in presenting particular types of antigen to CD4 T cells. This discovery supported the development of the first successful immunomodulatory therapies: glatiramer acetate, which mimics the antigen presentation process, and interferon beta, which targets CD4 T cell activation. Over 200 genetic risk variants, all single nucleotide polymorphisms (SNPs), have now been described. The SNPs are located within, or close to, genes expressed predominantly in acquired and innate immune cell subsets, indicating that both contribute to MS pathogenesis. The risk alleles indicate variation in the regulation of gene expression, rather than protein variation, underpins genetic susceptibility. In this review, we discuss how the expression and function of the risk genes, as well as the effect on these of the risk SNPs, indicate specific acquired immune cell processes that are the target of current successful therapies, and also point to novel therapeutic approaches.

IFN-λ3, not IFN-λ4, likely mediates IFNL3-IFNL4 haplotype-dependent hepatic inflammation and fibrosis.

Genetic variation in the IFNL3-IFNL4 (interferon-λ3-interferon-λ4) region is associated with hepatic inflammation and fibrosis. Whether IFN-λ3 or IFN-λ4 protein drives this association is not known. We demonstrate that hepatic inflammation, fibrosis stage, fibrosis progression rate, hepatic infiltration of immune cells, IFN-λ3 expression, and serum sCD163 levels (a marker of activated macrophages) are greater in individuals with the IFNL3-IFNL4 risk haplotype that does not produce IFN-λ4, but produces IFN-λ3. No difference in these features was observed according to genotype at rs117648444, which encodes a substitution at position 70 of the IFN-λ4 protein and reduces IFN-λ4 activity, or between patients encoding functionally defective IFN-λ4 (IFN-λ4-Ser70) and those encoding fully active IFN-λ4-Pro70. The two proposed functional variants (rs368234815 and rs4803217) were not superior to the discovery SNP rs12979860 with respect to liver inflammation or fibrosis phenotype. IFN-λ3 rather than IFN-λ4 likely mediates IFNL3-IFNL4 haplotype-dependent hepatic inflammation and fibrosis.