Search for Genetic Factors Associated with Susceptibility to Multiple Sclerosis

Mucosal Immunity and the Gut-Microbiota-Brain-Axis in Neuroimmune Disease

Recent advances in next-generation sequencing (NGS) technologies have opened the door to a wellspring of information regarding the composition of the gut microbiota. Leveraging NGS technology, early metagenomic studies revealed that several diseases, such as Alzheimer's disease, Parkinson's disease, autism, and myalgic encephalomyelitis, are characterized by alterations in the diversity of gut-associated microbes. More recently, interest has shifted toward understanding how these microbes impact their host, with a special emphasis on their interactions with the brain. Such interactions typically occur either systemically, through the production of small molecules in the gut that are released into circulation, or through signaling via the vagus nerves which directly connect the enteric nervous system to the central nervous system. Collectively, this system of communication is now commonly referred to as the gut-microbiota-brain axis. While equally important, little attention has focused on the causes of the alterations in the composition of gut microbiota. Although several factors can contribute, mucosal immunity plays a significant role in shaping the microbiota in both healthy individuals and in association with several diseases. The purpose of this review is to provide a brief overview of the components of mucosal immunity that impact the gut microbiota and then discuss how altered immunological conditions may shape the gut microbiota and consequently affect neuroimmune diseases, using a select group of common neuroimmune diseases as examples.

IL12B gene polymorphisms have sex-specific effects in relapsing-remitting multiple sclerosis

IL-12-family cytokines play a pivotal role in neuroinflammation and neurodegeneration in relapsing-remitting multiple sclerosis (RRMS). The aim of the study was to evaluate whether two polymorphisms in IL12B gene, rs17860508 and rs3212227, are associated with RRMS, and to define their function effect on serum level of IL-12p40 and IL-23 and degree of disability in RRMS cases. In total 156 Bulgarian patients with Expanded Disability Status Scale score ranging from 1.0 to 3.5 in remission of the disease and 379 controls were genotyped by polymerase chain reaction-based methods. The IL-12p40 and IL-23 serum levels were determined by enzyme-linked immunosorbent assay. We have found substantially higher IL-12p40 and IL-23 serum levels in cases than in controls (p < 0.01) in a sex-dependent manner. Women with RRMS had significantly higher IL-12р40 and IL-23 than men. Gender-stratified association analyses showed a significant impact of rs3212227 polymorphism on RRMS susceptibility in men. The carriers of rs3212227*CC-genotype (OR 3.390, 95% CI 1.007-11.545, p = 0.023) and haplotype rs17860508*2-allele/rs3212227*C-allele (OR 3.740; 95% CI 1.36-10.32, p = 0.007), showed higher risk of RRMS in men, in contrast to women. In women, both IL12B polymorphisms influencing the course, rather than genetic predisposition of RRMS. The rs17860508*22-genotype was associated with significantly lower disability (OR 0.208; 95% CI 0.055-0.725; p_c = 0.01) and lower IL-23 serum levels (p = 0.0345), while rs3212227*AA-genotype was associated with early onset of the disease (OR 2.368; 95% CI 1.007-5.608; p = 0.03). Our results suggest that sex-specific effects of IL12B polymorphisms, rs17860508 and rs3212227, on genetic predisposition and disease course of RRMS, is probably mediated by their gender-dependent functional effect on IL-12p40-containing cytokines.

Nutritional modulation of the intestinal microbiota; future opportunities for the prevention and treatment of neuroimmune and neuroinflammatory disease

The gut-brain axis refers to the bidirectional communication between the enteric nervous system and the central nervous system. Mounting evidence supports the premise that the intestinal microbiota plays a pivotal role in its function and has led to the more common and perhaps more accurate term gut-microbiota-brain axis. Numerous studies have identified associations between an altered microbiome and neuroimmune and neuroinflammatory diseases. In most cases, it is unknown if these associations are cause or effect; notwithstanding, maintaining or restoring homeostasis of the microbiota may represent future opportunities when treating or preventing these diseases. In recent years, several studies have identified the diet as a primary contributing factor in shaping the composition of the gut microbiota and, in turn, the mucosal and systemic immune systems. In this review, we will discuss the potential opportunities and challenges with respect to modifying and shaping the microbiota through diet and nutrition in order to treat or prevent neuroimmune and neuroinflammatory disease.

Genetic predisposition of IL-10 promoter polymorphisms with risk of multiple sclerosis: A meta-analysis

Interleukin-10 (IL-10) is a anti-inflammatory cytokine, which controls inflammation by inhibiting the synthesis of several cytokines produced by Th1 cells and macrophages. The association between Interleukin-10 promoter polymorphisms with the risk of multiple sclerosis (MS) remains inconclusive. In this study, a meta-analysis has been performed to assess the relationship between IL-10 gene polymorphisms rs1800896, rs1800871 and rs1800872 with the risk of MS. Nine case-control studies were selected involving 2755 participants. The association between the polymorphisms and MS was examined by the pooled odds ratios (ORs) with 95% confidence intervals (CIs) in allelic, homozygote, heterozygote, dominant and recessive genetic models. Of analyzed genetic models, the pooled ORs and CIs of each SNPs calculated based on random (I2>50) or fixed effects (I2<50) methods, which showed no significant association (p-value>0.05) of genetic predisposition with MS susceptibility across Asian and Caucasian populations. In addition, assessment based on funnel plot and Egger's linear regression test suggests no publication bias in all analyzed genetic models. Overall, our results demonstrated that rs1800896, rs1800871 and rs1800872 polymorphisms may not be the risk factor for the development of MS in both the populations.

Meta-analysis of theIL23RandIL12Bpolymorphisms in multiple sclerosis

PURPOSE

Polymorphisms in the genes encoding interleukin-23 receptor (IL23R) and the p40 subunit of IL-12/23 (IL12B) have been implicated in multiple sclerosis (MS) risk. However, results of different studies are inconsistent. Our aim was to perform a meta-analysis on this topic.

METHODS

We assessed two variants (rs10889677 and rs7517847) of IL23R and the A1188C polymorphism (rs3212227) of IL12B. Electronic databases (PubMed, Web of Science and Scopus) were searched for eligible studies published until September 2014. Odds ratio (OR) and 95% confidence interval (95% CI) were used to investigate the strength of association in dominant, recessive, homozygote and allelic comparison models.

RESULTS

Seven case-control studies with 2250 MS patients and 2320 controls were included in this meta-analysis. The pooled results showed no association of rs10889677 and rs7517847 with MS risk in any of the genetic models. Although the pooled analysis showed an association between rs3212227 and MS in all study subjects in dominant (OR = 0.81, 95% CI: 0.66-0.99, P(h) = 0.480, P(z) = 0.044) and allelic comparison (OR = 0.84, 95% CI: 0.72-0.98, P(h) = 0.967, P(z) = 0.030) models, subgroup analysis based on ethnicity did not suggest an association between rs3212227 and MS risk in Caucasians in any of the genetic models, and there was no association between rs3212227 and MS risk in an Asian group.

CONCLUSIONS

The IL23R polymorphisms rs10889677, rs7517847, and the IL12B polymorphism rs3212227 are not associated with MS risk.

Association of IL-23 and its receptor gene single-nucleotide polymorphisms with multiple sclerosis in Chinese southern population

The subunit of IL-23 (IL12B) and its receptor (IL23R) gene single-nucleotide polymorphisms (SNPs) have been shown to be associated with several autoimmune diseases such as inflammatory bowel disease, psoriasis and ankylosing spondylitis. However, the association studies between multiple sclerosis (MS) and SNPs of IL12B or IL23R gene have been reported with inconsistent results in Caucasian population. These discrepancies prompted us to investigate whether IL12B and IL23R variants are associated with susceptibility to MS in Chinese southern population. In this study, we investigated four SNPs (rs2201841, rs10889677, rs7517847 in IL23R and rs3212227 in IL12B) in 178 MS patients and 221 health controls in southern China using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. There was no difference of genotype or allele distribution of these SNPs between MS patients and controls. No association was found between gene polymorphisms and clinical characteristics in MS patients. Furthermore, haplotypes analysis showed similar distribution of haplotype frequencies in MS patients and controls. Our study showed that the IL12B and IL23R gene SNPs does not seem to be associated with MS susceptibility in Chinese southern population.

Is the IL-10 promoter polymorphism at position -592 associated with immune system-related diseases?

Immune responses are the main causes of immune system-related diseases such as hypersensitivities and autoimmunity. It has also been established that cytokines play key roles in the regulation of immune responses which have been shown to be important in the pathogenesis of the diseases. IL-10, the main anti-inflammatory cytokine, is produced by several immune cells such as T regulatory and Th2 lymphocytes, activated macrophages, B regulatory lymphocytes as well as other cell types. It plays a key role in the regulation of immune responses after microbe elimination (homeostasis) and against self-antigens to prevent hypersensitivity and autoimmune diseases, respectively. Studies showed that a single nucleotide polymorphism (SNP) at the -592 position of IL-10 is associated with its regulation of expression. This review addresses the recent information regarding the association of the polymorphism at position -592 of IL-10 with immune-related diseases including type 2 diabetes with and without nephropathy, multiple sclerosis, and asthma with an emphasize on Iranian patients.

Interleukin-21 in chronic inflammatory diseases

Interleukin-21 (IL-21), a cytokine produced by various subsets of activated CD4+ T cells, regulates multiple innate and adaptive immune responses. Indeed, IL-21 controls the proliferation and function of CD4+ and CD8+ T lymphocytes, drives the differentiation of B cells into memory cells and Ig-secreting plasma cells, enhances the activity of natural killer cells and negatively regulates the differentiation and activity of regulatory T cells. Moroever, IL-21 can stimulate nonimmune cells to synthesize various inflammatory molecules. Excessive production of IL-21 has been described in many human chronic inflammatory disorders and there is evidence that blockade of IL-21 helps attenuate detrimental responses in mouse models of immune-mediated diseases. In this article we briefly review data supporting the pathogenic role of IL-21 in immune-inflammatory pathologies and discuss the benefits and risks of IL-21 neutralization in patients with such diseases.

Modulation of the central memory and Tr1-like regulatory T cells in multiple sclerosis patients responsive to interferon-beta therapy

Background: Interferon-beta is used to reduce disease activity in multiple sclerosis, but its action is incompletely understood, individual treatment response varies among patients, and biological markers predicting clinical benefits have yet to be identified. Since it is known that multiple sclerosis patients have a deficit of the regulatory T-cell subsets, we investigated whether interferon-beta therapy induced modifications of the two main categories of regulatory T cells (Tregs), natural and IL-10-secreting inducible Tr1 subset, in patients who are biologically responsive to the therapy.

Methods: T-cell phenotype was determined by flow cytometry, while real-time PCR was used to evaluate interferon-beta bioactivity through MxA determination, and to measure the RNA for IL-10 and CD46 molecule in peripheral blood mononuclear cells stimulated with anti-CD46 and anti-CD3 monoclonal antibodies, which are known to expand a Tr1-like population.

Results: Interferon-beta induced a redistribution of natural Treg subsets with a shift of naive Tregs towards the ‘central memory-like’ Treg population that expresses the CCR7 molecule required for the in vivo suppressive activity. Furthermore, in a subgroup of treated patients, the CD46/CD3 co-stimulation, probably through the Tr1-like subset modulation, increased the production of RNA for IL-10 and CD46. The same group showed a lower median EDSS score after two years of therapy.

Conclusions: The selective increase of ‘central memory-like’ subset and the involvement of the Tr1-like population may be two of the mechanisms by which interferon-beta achieves its beneficial effects. The quantification of RNA for IL-10 and CD46 could be used to identify patients with a different response to interferon-beta therapy.

-308 G > A of TNF-α gene promoter decreases the risk of multiple sclerosis: a meta-analysis

BACKGROUND

Environmental and genetic factors are thought to be involved in the pathogenesis of multiple sclerosis (MS). Polymorphisms of tumor necrosis factor (TNF)-α -308 were implicated in MS risk in several case-control association studies. However, the studies have shown inconsistent results.

OBJECTIVES

To address the association of G/A polymorphisms of TNF-α -308 with MS risk by meta-analysis.

METHODS

Thirteen studies were included. Pooled odds ratios (ORs) together with 95% confidence intervals (CIs) were calculated.

RESULTS

A total of 1870 cases and 2769 controls were included in the meta-analysis. The pooled result indicated that -308 A allele is significantly associated with reduced risk of MS compared with -308 G allele (A vs. G, p=0.022). The same pattern of the result was also obtained in the contrasts of AA+ GA vs. GG (p=0.008) and GA vs. GG (p=0.007). For AA vs. GG or AA vs. GA + GG, no significant association was detected most likely caused by very low frequency or non-availability of homozygote genotype AA for all of the studies.

CONCLUSIONS

TNF-α -308 A allele is associated with reduced risk of MS.

Evaluating epigenetic landmarks in the brain of multiple sclerosis patients: a contribution to the current debate on disease pathogenesis

The evidence suggesting a role of epigenetics in the definition of complex trait diseases is rapidly increasing. The gender prevalence of multiple sclerosis, the low level concordance in homozygous twins and the linkage to several genetic loci, suggest an epigenetic component to the definition of this demyelinating disorder. While the immune etio-pathogenetic mechanism of disease progression has been well characterized, still relatively little is known about the initial events contributing to onset and progression of the demyelinating lesion. This article addresses the challenging question of whether loss of the mechanisms of epigenetic regulation of gene expression in the myelinating cells may contribute to the pathogenesis of multiple sclerosis, by affecting the repair process and by modulating the levels of enzymes involved in neo-epitope formation. The role of altered post-translational modifications of nucleosomal histones and DNA methylation in white matter oligodendroglial cells are presented in terms of pathogenetic concepts and the relevance to therapeutic intervention is then discussed.

Recent advances in genetic analysis of multiple sclerosis: genetic associations and therapeutic implications

Epidemiological studies have confirmed that genetic factors are a key component in the pathogenesis of multiple sclerosis (MS) and that those determining MS susceptibility have been extensively studied. Many papers have been published regarding the heritable differences useful in genetic studies; these include variations in DNA, such as single-nucleotide polymorphisms, microsatellites and insertion/deletion polymorphisms. However, to date, among other regions, HLA is the only region confirmed to possess genes that determine MS susceptibility. In this article, we review the progress during the last 5 years in the studies on the susceptibility genes and the pharmacogenetics of MS. Newer techniques and methods of analysis will hopefully result in better screening of individuals who are at highest risk and novel treatments.