Translational utility of experimental autoimmune encephalomyelitis: recent developments.

Multiple sclerosis (MS) is a complex autoimmune condition with firmly established genetic and environmental components. Genome-wide association studies (GWAS) have revealed a large number of genetic polymorphisms in the vicinity of, and within, genes that associate to disease. However, the significance of these single-nucleotide polymorphisms in disease and possible mechanisms of action remain, with a few exceptions, to be established. While the animal model for MS, experimental autoimmune encephalomyelitis (EAE), has been instrumental in understanding immunity in general and mechanisms of MS disease in particular, much of the translational information gathered from the model in terms of treatment development (glatiramer acetate and natalizumab) has been extensively summarized. In this review, we would thus like to cover the work done in EAE from a GWAS perspective, highlighting the research that has addressed the role of different GWAS genes and their pathways in EAE pathogenesis. Understanding the contribution of these pathways to disease might allow for the stratification of disease subphenotypes in patients and in turn open the possibility for new and individualized treatment approaches in the future.

IL-22RA2 associates with multiple sclerosis and macrophage effector mechanisms in experimental neuroinflammation.

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease of the CNS. Recent advances in whole-genome screening tools have enabled discovery of several MS risk genes, the majority of which have known immune-related functions. However, disease heterogeneity and low tissue accessibility hinder functional studies of established MS risk genes. For this reason, the MS model experimental autoimmune encephalomyelitis (EAE) is often used to study neuroinflammatory disease mechanisms. In this study, we performed high-resolution linkage analysis in a rat advanced intercross line to identify an EAE-regulating quantitative trait locus, Eae29, on rat chromosome 1. Eae29 alleles from the resistant strain both conferred milder EAE and lower production of proinflammatory molecules in macrophages, as demonstrated by the congenic line, DA.PVG-Eae29 (Dc1P). The soluble IL-22R α2 gene (Il-22ra2) lies within the Eae29 locus, and its expression was reduced in Dc1P, both in activated macrophages and splenocytes from immunized rats. Moreover, a single nucleotide polymorphism located at the end of IL-22RA2 associated with MS risk in a combined Swedish and Norwegian cohort comprising 5019 subjects, displaying an odds ratio of 1.26 (p = 8.0 × 10(-4)). IL-22 and its receptors have been implicated in chronic inflammation, suggesting that IL-22RA2 regulates a central immune pathway. Through a combined approach including genetic and immunological investigation in an animal model and large-scale association studies of MS patients, we establish IL-22RA2 as an MS risk gene.

Fine-mapping resolves Eae23 into two QTLs and implicates ZEB1 as a candidate gene regulating experimental neuroinflammation in rat.

BACKGROUND: To elucidate mechanisms involved in multiple sclerosis (MS), we studied genetic regulation of experimental autoimmune encephalomyelitis (EAE) in rats, assuming a conservation of pathogenic pathways. In this study, we focused on Eae23, originally identified to regulate EAE in a (LEW.1AV1xPVG.1AV1)F2 cross. Our aim was to determine whether one or more genes within the 67 Mb region regulate EAE and to define candidate risk genes. METHODOLOGY/PRINCIPAL FINDINGS: We used high resolution quantitative trait loci (QTL) analysis in the 10th generation (G10) of an advanced intercross line (AIL) to resolve Eae23 into two QTLs that independently regulate EAE, namely Eae23a and Eae23b. We established a congenic strain to validate the effect of this region on disease. PVG alleles in Eae23 resulted in significant protection from EAE and attenuated CNS inflammation/demyelination. Disease amelioration was accompanied with increased levels of Foxp3(+) cells in the CNS of the congenic strain compared to DA. We then focused on candidate gene investigation in Eae23b, a 9 Mb region linked to all clinical phenotypes. Affymetrix exon arrays were used to study expression of the genes in Eae23b in the parental strains, where none showed differential expression. However, we found lower expression of exon 4 of ZEB1, which is specific for splice-variant Zfhep1. ZEB1 is an interleukin 2 (IL2) repressor involved in T cell development. The splice-specific variance prompted us to next analyze the expression of ZEB1 and its two splice variants, Zfhep1 and Zfhep2, in both lymph node and spleen. We demonstrated that ZEB1 splice-variants are differentially expressed; severity of EAE and higher IL2 levels were associated with down-regulation of Zfhep1 and up-regulation of Zfhep2. CONCLUSIONS/SIGNIFICANCE: We speculate that the balance between splice-variants of ZEB1 could influence the regulation of EAE. Further functional studies of ZEB1 and the splice-variants may unravel novel pathways contributing to MS pathogenesis and inflammation in general.