Study on the protective effect of the KIR3DL1 gene in ankylosing spondylitis.

OBJECTIVE: Ankylosing spondylitis (AS) is an autoimmune disease that mainly affects the sacroiliac joints and the spine of the lower back. The disease is strongly associated with HLA-B27. Additional genes, single-nucleotide polymorphisms, and molecular components have been identified to be associated with AS, but the exact mechanism that drives disease development remains poorly understood. The killer cell immunoglobulin-like receptors (KIRs) are regulators of cytotoxicity of natural killer cells and T cell subsets and may be relevant in binding to HLA-B27 and the development of AS. We undertook this study to identify possible associations of KIR genotype with susceptibility to AS and disease characteristics including the presence of the HLA-B27 allele, disease severity, and uveitis. METHODS: We performed complete genotyping of the KIR locus in 303 Caucasian AS patients, 119 randomly selected healthy Caucasian controls, and 50 HLA-B27-positive healthy Caucasian controls by multiplex ligation-dependent probe amplification assay for detection of gene presence and copy number. RESULTS: We did not observe a significant association of any specific KIR gene or haplotype with susceptibility to AS or any other clinical manifestation. Disease severity, as measured by fulfilling the criteria for treatment with tumor necrosis factor blocking therapy, was linked to a lower number of genes for the functional variant of KIR3DL1 (P = 0.007). CONCLUSION: Our exploratory study indicates that KIR genes are not a major risk factor for susceptibility to AS. However, the data do suggest a role for KIRs in progression of the disease, whereby KIR3DL1 has a protective effect against the more severe manifestations of AS.

A genome-wide association study of rheumatoid arthritis without antibodies against citrullinated peptides.

INTRODUCTION: Rheumatoid arthritis (RA) patients can be classified based on presence or absence of anticitrullinated peptide antibodies (ACPA) in their serum. This heterogeneity among patients may reflect important biological differences underlying the disease process. To date, the majority of genetic studies have focused on the ACPA-positive group. Therefore, our goal was to analyse the genetic risk factors that contribute to ACPA-negative RA. METHODS: We performed a large-scale genome-wide association study (GWAS) in three Caucasian European cohorts comprising 1148 ACPA-negative RA patients and 6008 controls. All patients were screened using the Illumina Human Cyto-12 chip, and controls were genotyped using different genome-wide platforms. Population-independent analyses were carried out by means of logistic regression. Meta-analysis with previously published data was performed as follow-up for selected signals (reaching a total of 1922 ACPA-negative RA patients and 7087 controls). Imputation of classical HLA alleles, amino acid residues and single nucleotide polymorphisms was undertaken. RESULTS: The combined analysis of the studied cohorts resulted in identification of a peak of association in the HLA-region and several suggestive non-HLA associations. Meta-analysis with previous reports confirmed the association of the HLA region with this subset and an observed association in the CLYBL locus remained suggestive. The imputation and deep interrogation of the HLA region led to identification of a two amino acid model (HLA-B at position 9 and HLA-DRB1 at position 11) that accounted for the observed genome-wide associations in this region. CONCLUSIONS: Our study shed light on the influence of the HLA region in ACPA-negative RA and identified a suggestive risk locus for this condition.

Relevance of IL7R genotype and mRNA expression in Dutch patients with multiple sclerosis.

BACKGROUND: The interleukin 7 receptor (IL7R) has been recognized as a susceptibility gene for Multiple Sclerosis (MS). Analysis of rs6897932 (the most strongly MS-associated single nucleotide polymorphism (SNP)), showed effects of genotype on the relative expression of membrane-bound to total amount of IL7R mRNA. OBJECTIVE: We assessed the relevance of IL7R on MS phenotype (including clinical and magnetic resonance imaging (MRI) parameters) at DNA and mRNA level in Dutch patients with MS. METHODS: The genotype of rs6897932 was analyzed in 697 patients with MS and 174 healthy controls. The relevance of genotype and carriership of the C allele on MS phenotype (disease activity and severity, using clinical and MRI parameters) was assessed. In addition, relative gene expression of membrane-bound to total IL7R mRNA was analyzed with respect to disease phenotype in a subgroup of 95 patients with early relapsing MS. RESULTS: In particular, homozygosity for the risk allele is a risk factor for MS in our population (OR(CC vs CT and TT) = 1.65 (95% CI: 1.18-2.30), two-sided p = 0.004). However, no effect of genotype or the relative expression of membrane-bound IL7R (presence of exon 6-7) to total amount of IL7R mRNA (presence of exon 4-5) was found on MS phenotype. DISCUSSION: Homozygosity for the IL7R exon 6 rs6897932 C allele is associated with a higher risk for MS in our Dutch population. No effect was found of genotype or mRNA expression on disease phenotype.

Interferon regulatory factor 5 gene variants and pharmacological and clinical outcome of Interferonß therapy in multiple sclerosis.

Interferon-ß (IFNß) therapy is effective in approximately half of the patients with relapsing-remitting multiple sclerosis (RRMS). Clinical non-responders were characterized by an increased expression of IFN response genes before the start of therapy, and a lack of a pharmacologically induced increase in IFN response gene activity. Because Interferon Regulatory Factor 5 (IRF5) is a master regulator of IFN-activity, we carried out a candidate gene study of IRF5 gene variants in relation to the pharmacological and clinical response upon IFNß treatment. We found that patients with the IRF5 rs2004640-TT and rs47281420-AA genotype exerted a poor pharmacological response to IFNß compared with patients carrying the respective G-alleles (P=0.0006 and P=0.0023, respectively). Moreover, patients with the rs2004640-TT genotype developed more magnetic resonance imaging (MRI)-based T2 lesions during IFNß treatment (P=0.003). Accordingly, an association between MRI-based non-responder status and rs2004640-TT genotype was observed (P=0.010). For the rs4728142-AA genotype a trend of an association with more T2 lesions during IFNß treatment and MRI-based non-responder status was observed (P=0.103 and P=0.154, respectively). The clinical relevance of the rs2004640-TT genotype was validated in an independent cohort wherein a shorter time to first relapse was found (P=0.037). These findings suggest a role for IRF5 gene variation in the pharmacological and clinical outcome of IFNß therapy that might have relevance as biomarker to predict the response to IFNß in multiple sclerosis.

Genetic correlations of brain lesion distribution in multiple sclerosis: an exploratory study.

BACKGROUND AND PURPOSE: In MS, the total brain lesion volume and spatial distribution of lesions across the brain vary widely among individual patients. We hypothesized that spatial distribution may be partially driven by genetic predisposition, and we aimed to explore relations among candidate genes and the spatial distribution of white matter brain lesions in MS. MATERIAL AND METHODS: Genotypes of 69 SNPs in 208 patients with MS were related to the spatial distribution of T2 brain lesions. Lesions were manually outlined on MR images, and binary lesion masks were produced and registered to a common space. With Randomise software, the lesion masks were related to genotype by using a voxelwise nonparametric GLM approach, followed by clusterwise analysis. We used a DNA chip with SNPs selected from the literature on MS susceptibility, severity, and phenotypes. RESULTS: For 11 of these SNPs, 1 of the genotypes expressed significant clusters of increased or decreased lesion probability in varying, predominantly periventricular, brain regions. When we statistically controlled the voxelwise analyses for effects of total brain lesion volume, only 1 SNP remained significant: rs2227139, located within the MHC class II region. This SNP retained its periventricular cluster of significantly increased lesion probability for the heterozygote genotype. CONCLUSIONS: Heterozygosity of rs2227139 (MHC class II region) is associated with increased right frontal periventricular lesion probability (P<.01). Ten other SNPs showed associations between genotype and spatial lesion distribution that are partly explained by total lesion volume.

NOD2, CD14 and TLR4 mutations do not influence response to adalimumab in patients with Crohn's disease: a preliminary report.

INTRODUCTION: Adalimumab is a recombinant fully-human monoclonal immunoglobulin (IgG1) antibody utilized in the treatment of Crohn's disease. Unfortunately no clinical or genetic markers exist to predict response to anti-tumor necrosis factor-alpha (TNF) therapy. The aim of this study was to evaluate the association between selected genes involved in cytokine regulation and response to adalimumab treatment in Crohn's disease. METHODS: twenty-four patients with Crohn's disease either naïve (n = 8) or had lost response or were unable to tolerate the chimeric anti-TNF antibody infliximab (n=16) were enrolled in the study. Patients were genotyped for main polymorphisms in NOD2, CD14 and TLR4 genes. Response to adalimumab treatment was defined as a decrease of Crohn's disease activity index of at least 100 points or a closure of at least 50% of fistulas in case of fistulizing Crohn's disease. RESULTS: overall, 75% of patients did respond to treatment. However, no statistically significant association was found between any of the genotypes and the response to adalimumab. CONCLUSIONS: In our small study group no association between the studied polymorphisms and response to adalimumab was apparent. Systematic studies to search for genetic markers of response to anti-TNF therapy are necessary.

Coeliac disease in China, a field waiting for exploration.

BACKGROUND: no systematic studies on the prevalence of coeliac disease (CD) have been reported from China. In western populations CD is more common in patients with insulin dependent diabetes mellitus (IDDM) and in diarrhoea-predominant irritable bowel syndrome (D-IBS). We have screened patients with these conditions presenting to the outpatient department of a large hospital of "Traditional Chinese Medicine" (TCM) in Nanjing, Jiangsu province, P.R. China. METHODS: we tested sera of 78 unrelated Han Chinese patients (5 IDDM and 73 D-IBS), using ELISA serological tests for IgG anti-gliadin antibodies (IgG-AGA) and IgA anti-tissue transglutaminase antibodies (IgA-tTG). RESULTS: six out of 78 patients (7.7%) were positive for IgG-AGA (two men and four women) and two (2.6%) were positive for IgA-tTGs. One of the latter patients was negative for IgG-AGA. Besides, one patient had a dubious IgA-tTG antibody and a positive IgG-AGA. None of the six patients agreed to undergo duodenal biopsy. Two out of these six patients followed a gluten-free diet for one year. In one patient the diarrhoea ceased and his body weight increased. Another stopped losing weight. CONCLUSIONS: this study previously published as a letter in GUT (Wu J, Xia B, von Blomberg BME, Zhao C, Yang XW, Crusius JBA, Peña AS. Coeliac disease: emerging in China? Gut 2010; 59(3): 418-9) demonstrated that CD may exist in the Jiangsu province of P.R. China. The present article draws attention to the difficulties of following a standard protocol in China such as established in western countries and highlights important factors less well known in the west in relation to the development of CD in China. Wheat production became significant in China between 1600 and 1300 B.C. After the Han dynasty (500-200 B.C.), wheat was one of the main cereals in China. One the major wheat fields in China is located in the Jiangsu province where the research for this article was performed. A review of Chinese literature shows that the predominant HLA-DQ CD risk alleles and haplotypes are present in the Jiangsu province. Genetic background, food consumption, and the results of our study suggest that CD should actively be investigated in P.R. China.

A new avenue to investigate: the autophagic process. From Crohn's disease to Chlamydia.

The finding that a variant (T300A) of the autophagyrelated 16-like 1 (ATG16L1) gene is associated with Crohn's disease suggests that the inability to eliminate intestinal intracellular microbes via (macro)autophagy may be involved in the pathogenesis of this disease. The variant induces an autophagy-associated defect in Paneth cells, specialized cells in the crypts of Lieberkuhn within the small intestine that secrete defensins and other antimicrobial peptides. Moreover, other loci, IRGM and LRRK2 involved in autophagy and implicated in clearance of intracellular bacteria have been found to be associated with Crohn's disease. These unexpected findings have changed the focus of research in Crohn's disease and have stimulated an in-depth study of the complex process of autophagy. Autophagy is regulated by many genes and is emerging as a central player in the immunologic control of intracellular bacteria. Chlamydia trachomatis is able to inhibit apoptosis and the production of nuclear factor kappa B (NFkappaB) in order to survive in the host. Extensive studies on association of genes regulating the inflammatory response in experimental models and in humans as revised in other sections of this supplement have failed to explain the longterm complications of C. trachomatis infection. The advances in the molecular pathways of Chlamydia infection and their effects on the Golgi apparatus and other cytoplasmic organelles suggests that defects in autophagic genes may predispose the host to chronic infection and be responsible for the long-term complications. A new genomic approach of the complete autophagic pathway may reveal new insight to understand the presence of a complication in affected individuals, even if at present there is no evidence that C. trachomatis is affected by this pathway.