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Ludvig M Sollid

Publications and source records attributed to Ludvig M Sollid.

At least 19 recordsLinked to original sources
PubMed2006

FOXP3 polymorphisms in type 1 diabetes and coeliac disease.

The FOXP3 gene encodes a transcription factor thought to be essential for the development and function of T regulatory cells. Two previous studies have tested common polymorphisms in FOXP3 for association with type 1 diabetes (T1D) with conflicting results. The aim of our study was to see whether there is any evidence of association between the FOXP3 polymorphisms previously reported to be associated with T1D, in a Caucasian population regarding T1D and coeliac disease (CD). We further looked for evidence of interaction between FOXP3 polymorphisms and HLA-DR3 in conferring susceptibility to T1D. Initially, we analysed two microsatellites in the FOXP3 gene in 363 T1D nuclear families. Our results indicated an association between FOXP3 and T1D (global p=0.004) and a possible interaction between FOXP3 and the HLA-DR3-DQ2 susceptibility haplotype. We then genotyped an additional independent set of 826 T1D patients and 1459 controls as well as one CD dataset consisting of 325 families. A similar tendency was revealed in the CD family material (pnc=0.055 for the associated allele). On the other hand, we were unable to reproduce our initial findings in the T1D case-control dataset (global p=0.6). Our results suggest that the tested FOXP3 markers do not have any major impact on susceptibility for these diseases.

Adolescent↗
PubMed2006

HLA-DQ2 and -DQ8 signatures of gluten T cell epitopes in celiac disease.

Celiac disease is associated with HLA-DQ2 and, to a lesser extent, HLA-DQ8. Type 1 diabetes is associated with the same DQ molecules in the opposite order and with possible involvement of trans-encoded DQ heterodimers. T cells that are reactive with gluten peptides deamidated by transglutaminase 2 and invariably restricted by DQ2 or DQ8 can be isolated from celiac lesions. We used intestinal T cells from celiac patients to map DQ2 and DQ8 epitopes within 2 representative gluten proteins, alpha-gliadin AJ133612 and gamma-gliadin M36999. For alpha-gliadin, DQ2- and DQ8-restricted T cells recognized deamidated peptides of 2 separate regions. For gamma-gliadin, DQ2- and DQ8-restricted T cells recognized deamidated peptides of the same region. Some gamma-gliadin peptides were recognized by T cells in the context of DQ2 or DQ8 when bound in exactly the same registers, but with different requirements for deamidation; deamidation at peptide position 4 (P4) was important for DQ2-restricted T cells, whereas deamidation at P1 and/or P9 was important for DQ8-restricted T cells. Peptides combining the DQ2 and DQ8 signatures could be presented by DQ2, DQ8, and trans-encoded DQ heterodimers. Our findings shed light on the basis for the HLA associations in celiac disease and type 1 diabetes.

Amino Acid Sequence↗
PubMed2006

Mapping genes and pathways in autoimmune disease.

Identifying novel genes and pathways controlling T-cell activation holds the promise of developing novel therapies for autoimmune disease and cancer. Recent advances in the human genome project have shown that it is timely for small groups searching for this Holy Grail to rethink their options. In this review, some alternative strategies employed in pursuing novel disease pathways in rodents and humans, including recent results, are presented. Examples include the murine Roquin and Ncf1 genes, and the PTPN22 gene identified in humans. The potential benefit of reducing the heterogeneity of clinically defined diseases by the careful phenotyping of patients, cells and lesions using advanced molecular biology and imaging techniques is highlighted.

Animals↗
PubMed2006

Association analysis of MYO9B gene polymorphisms with celiac disease in a Swedish/Norwegian cohort.

Association between myosin IXB (MYO9B) gene variants and celiac disease (CD) has been reported in a study of a Dutch cohort. Six single nucleotide polymorphisms (SNPs) within the 3' part of the MYO9B gene showed significant genetic association and formed an associated haplotype. The current study aimed to replicate these findings in a Swedish/Norwegian cohort. Genotyping of the three SNPs which tagged the associated haplotype was performed in a CD family dataset (n = 326) and in an additional set of healthy controls (n = 562). Although our material provided reasonable power to detect the previously observed association, we were unable to replicate association with these SNPs. Lack of reproducibility could be explained by no or negligible contribution of MYO9B to the genetic predisposition to CD in the Swedish/Norwegian population. Alternatively, it might be due to variable linkage disequilibria in distinct populations in the tested SNPs and a causative mutation yet to be identified or to false positive findings (type I error) in the Dutch study.

Celiac Disease↗
PubMed2006

A gut feeling for joint inflammation - using coeliac disease to understand rheumatoid arthritis.

Major advances have been made in the molecular understanding of coeliac disease, initiated by the identification of intestinal gluten-reactive T cells. It is now clear that this common intestinal disorder, which is precipitated by the ingestion of wheat gluten, is mediated by DQ2-restricted T cells specific for gluten peptides modified by transglutaminase 2, the same enzyme that is targeted by disease-specific autoantibodies. Interestingly, many of the important features identified in coeliac disease, including HLA association, target organ T-cell infiltration, disease-specific autoantibodies and the distinct targeting of in vivo modified antigens, are also present in rheumatoid arthritis. The experiences from coeliac disease should therefore help identify disease-relevant T-cell epitopes in rheumatoid arthritis.

Arthritis, Rheumatoid↗
PubMed2006

Specific modification of peptide-bound citrulline residues.

Immune reactions to citrulline-containing proteins appear to be central in the immunopathogenesis of rheumatoid arthritis. Citrulline residues are introduced into proteins by deimination of arginine residues, likely by an enzymatic process. There is a need to characterize which proteins in the inflamed joints of rheumatoid patients contain citrulline in situ. The characterization of deiminated proteins will be greatly facilitated by specific modification of peptide-bound citrulline residues that will enable specific enrichment and detection of citrulline-containing peptides. This study presents the details of such a modification method. The chemistry behind the reaction of the ureido group of citrulline with 2,3-butanedione in the presence of antipyrine is unraveled. Parameters for optimization of the reaction with respect to specificity and completeness, including the testing of different acids, reactant concentrations, and reaction time, are presented. This modification reaction is specific for citrulline residues. The modified product shows a characteristic mass shift of +238Da, as demonstrated by mass spectrometry. The product absorbs UV-Vis radiation at 464nm, and it is demonstrated that this can be used to selectively monitor citrulline-containing peptides during the separation of protein digests. Finally, the structure of the product of modified citrulline is solved by nuclear magnetic resonance spectroscopy using N-butylurea as a model substance. The results presented should facilitate the development of tags that can be used for the enrichment and subsequent detection of citrulline-containing protein fragments by mass spectrometry.

Antipyrine↗
PubMed2006

Inhibition of HLA-DQ2-mediated antigen presentation by analogues of a high affinity 33-residue peptide from alpha2-gliadin.

Human leukocyte antigen DQ2 is a class II major histocompatibility complex protein that plays a critical role in the pathogenesis of Celiac Sprue by binding to epitopes derived from dietary gluten and triggering the inflammatory response of disease-specific T cells. Inhibition of DQ2-mediated antigen presentation in the small intestinal mucosa of Celiac Sprue patients therefore represents a potentially attractive mode of therapy for this widespread but unmet medical need. Starting from a pro-inflammatory, proteolytically resistant, 33-residue peptide, LQLQPFPQPELPYPQPELPYPQPELPYPQPQPF, we embarked upon a systematic effort to dissect the relationships between peptide structure and DQ2 affinity and to translate these insights into prototypical DQ2 blocking agents. Three structural determinants within the first 20 residues of this 33-mer peptide, including a PQPELPYPQ epitope, its N-terminal flanking sequence, and a downstream Glu residue, were found to be important for DQ2 binding. Guided by the X-ray crystal structure of DQ2, the L11 and L18 residues in the truncated 20-mer analogue were replaced with sterically bulky groups so as to retain high DQ2 affinity but abrogate T cell recognition. A dimeric ligand, synthesized by regiospecific coupling of the 20-mer peptide with a bifunctional linker, was identified as an especially potent DQ2 binding agent. Two such ligands were able to attenuate the proliferation of disease-specific T cell lines in response to gluten antigens and, therefore, represent prototypical examples of pharmacologically suitable DQ2 blocking agents for the potential treatment of Celiac Sprue.

Amino Acid Sequence↗
PubMed2006

Heterologous expression, purification, refolding, and structural-functional characterization of EP-B2, a self-activating barley cysteine endoprotease.

We describe the heterologous expression in Escherichia coli of the proenzyme precursor to EP-B2, a cysteine endoprotease from germinating barley seeds. High yields (50 mg/l) of recombinant proEP-B2 were obtained from E. coli inclusion bodies in shake flask cultures following purification and refolding. The zymogen was rapidly autoactivated to its mature form under acidic conditions at a rate independent of proEP-B2 concentration, suggesting a cis mechanism of autoactivation. Mature EP-B2 was stable and active over a wide pH range and efficiently hydrolyzed a recombinant wheat gluten protein, alpha2-gliadin, at sequences with known immunotoxicity in celiac sprue patients. The X-ray crystal structure of mature EP-B2 bound to leupeptin was solved to 2.2 A resolution and provided atomic insights into the observed subsite specificity of the endoprotease. Our findings suggest that orally administered proEP-B2 may be especially well suited for treatment of celiac sprue.

Amino Acid Sequence↗
PubMed2006

Mechanisms of disease: immunopathogenesis of celiac disease.

Celiac disease is a genetic inflammatory disorder with autoimmune components that is induced by the ingestion of dietary gluten. Refractory sprue and enteropathy-associated T-cell lymphoma are rare but distinctive complications of the disease. Although the importance of the adaptive immune response to gluten has been well established, observations now also point towards a central role for the gluten-induced innate stress response in the pathogenesis of celiac disease and its malignant complications.

Celiac Disease↗
PubMed2006

A unique dendritic cell subset accumulates in the celiac lesion and efficiently activates gluten-reactive T cells.

BACKGROUND & AIMS: Celiac disease is a chronic inflammation of the duodenal mucosa driven by gluten-reactive T cells restricted by the disease-associated HLA-DQ2 molecule. The mechanisms that regulate the activation of mucosal T cells are, however, understood poorly. The aim of this study was to identify the antigen-presenting cells that are responsible for the activation of gluten-reactive T cells in the celiac lesion. METHODS: Intestinal biopsy specimens obtained from untreated and treated celiac patients and normal controls were either snap-frozen directly or incubated for 24 hours with or without gluten peptides. Cryosections were subjected to multicolor immunofluorescence applying monoclonal antibodies to a range of antigen-presenting cell markers. Macrophages and dendritic cells were isolated from enzymatically digested small intestinal biopsies of untreated patients and incubated with gluten-reactive T-cell clones to measure their antigen-presenting capacity. RESULTS: HLA-DQ2+ cells in the normal duodenal mucosa consisted of 2 distinct cell populations: about 80% were CD68+ DC-lysosome intercellular adhesion molecule-3-grabbing nonintegrin+ macrophages and 20% were CD11c+ dendritic cells. Importantly, the CD11c+ dendritic cells accumulated in the celiac lesion and revealed an activated phenotype expressing CD86 and DC-specific-associated membrane protein. Moreover, when isolated from challenged biopsy specimens, the CD11c+ dendritic cells efficiently activated gluten-reactive T cells. CONCLUSIONS: Our results suggest that a unique subset of dendritic cells are responsible for local activation of gluten-reactive T cells in the celiac lesion.

Adolescent↗
PubMed2005

Is celiac disease an autoimmune disorder?

Celiac disease, which results from an immune reaction to ingested cereal gluten proteins, has several autoimmune features. In particular, celiac disease patients produce highly disease specific IgA and IgG autoantibodies to tissue transglutaminase when they are on a gluten-containing diet, and they have small intestinal intraepithelial lymphocytes which can mediate direct cytotoxicity of enterocytes expressing MIC molecules in an antigen non-specific manner. Similar to typical autoimmune disorders, celiac disease has a multifactorial aetiology with complex genetics, and several autoimmune diseases are commonly presented by patients with celiac disease. Much has been learned about the immunology of celiac disease in recent years, and there is overwhelming evidence that the immune response to gluten is central to the pathogenesis. In light of this, the many autoimmune phenomena associated with celiac disease are thought-provoking, and they challenge us to rethink the boundaries between autoimmunity and immunopathology.

Autoantibodies↗
PubMed2005

Refining the rules of gliadin T cell epitope binding to the disease-associated DQ2 molecule in celiac disease: importance of proline spacing and glutamine deamidation.

Celiac disease is driven by intestinal T cells responsive to proline-rich gluten peptides that often harbor glutamate residues formed by tissue transglutaminase-mediated glutamine conversion. The disease is strongly associated with the HLA variant DQ2.5 (DQA1*05, DQB1*02), and intestinal gluten-reactive T cells from DQ2.5-positive patients are uniquely restricted by this HLA molecule. In this study, we describe the mapping of two novel T cell epitopes of gamma-gliadin and the experimental identification of the DQ2.5 binding register of these and three other gamma-gliadin epitopes. The new data extend the knowledge base for understanding the binding of gluten peptides to DQ2.5. The alignment of the experimentally determined binding registers of nine gluten epitopes reveal positioning of proline residues in positions P1, P3, P6, and P8 but never in positions P2, P4, P7, and P9. Glutamate residues formed by tissue transglutaminase-mediated deamidation are found in position P1, P4, P6, P7, or P9, but only deamidations in positions P4 and P6, and rarely in P7, seem to be crucial for T cell recognition. The majority of these nine epitopes are recognized by celiac lesion T cells when presented by the related but nonassociated DQ2.2 (DQA1*0201, DQB1*02) molecule. Interestingly, the DQ2.2 presentation for most epitopes is less efficient than presentation by the DQ2.5 molecule, and this is particularly prominent for the alpha-gliadin epitopes. Contrary to previous findings, our data do not show selective presentation of DQ2.5 over DQ2.2 for gluten epitopes that carry proline residues at the P3 position.

Amino Acid Sequence↗
PubMed2005

Main chain hydrogen bond interactions in the binding of proline-rich gluten peptides to the celiac disease-associated HLA-DQ2 molecule.

Binding of peptide epitopes to major histocompatibility complex proteins involves multiple hydrogen bond interactions between the peptide main chain and major histocompatibility complex residues. The crystal structure of HLA-DQ2 complexed with the alphaI-gliadin epitope (LQPFPQPELPY) revealed four hydrogen bonds between DQ2 and peptide main chain amides. This is remarkable, given that four of the nine core residues in this peptide are proline residues that cannot engage in amide hydrogen bonding. Preserving main chain hydrogen bond interactions despite the presence of multiple proline residues in gluten peptides is a key element for the HLA-DQ2 association of celiac disease. We have investigated the relative contribution of each main chain hydrogen bond interaction by preparing a series of N-methylated alphaI epitope analogues and measuring their binding affinity and off-rate constants to DQ2. Additionally, we measured the binding of alphaI-gliadin peptide analogues in which norvaline, which contains a backbone amide hydrogen bond donor, was substituted for each proline. Our results demonstrate that hydrogen bonds at P4 and P2 positions are most important for binding, whereas the hydrogen bonds at P9 and P6 make smaller contributions to the overall binding affinity. There is no evidence for a hydrogen bond between DQ2 and the P1 amide nitrogen in peptides without proline at this position. This is a unique feature of DQ2 and is likely a key parameter for preferential binding of proline-rich gluten peptides and development of celiac disease.

Amino Acid Sequence↗
PubMed2005

Equilibrium and kinetic analysis of the unusual binding behavior of a highly immunogenic gluten peptide to HLA-DQ2.

HLA-DQ2 predisposes an individual to celiac sprue by presenting peptides from dietary gluten to intestinal CD4(+) T cells. A selectively deamidated multivalent peptide from gluten (LQLQPFPQPELPYPQPELPYPQPELPYPQPQPF; underlined residues correspond to posttranslational Q --> E alterations) is a potent trigger of DQ2 restricted T cell proliferation. Here we report equilibrium and kinetic measurements of interactions between DQ2 and (i) this highly immunogenic multivalent peptide, (ii) its individual constituent epitopes, (iii) its nondeamidated precursor, and (iv) a reference high-affinity ligand of HLA-DQ2 that is not recognized by gluten-responsive T cells from celiac sprue patients. The deamidated 33-mer peptide efficiently exchanges with a preloaded peptide in the DQ2 ligand-binding groove at pH 5.5 as well as pH 7.3, suggesting that the peptide can be presented to T cells comparably well through the endocytic pathway or via direct loading onto extracellular HLA-DQ2. In contrast, the monovalent peptides, and the nondeamidated precursor, as well as the tight-binding reference peptide show a much poorer ability to exchange with a preloaded peptide in the DQ2 binding pocket, especially at pH 7.3, suggesting that endocytosis of these peptides is a prerequisite for T cell presentation. At pH 5.5 and 7.3, dissociation of the deamidated 33-mer peptide from DQ2 is much slower than dissociation of its constituent monovalent epitopes or the nondeamidated precursor but faster than dissociation of the reference high-affinity peptide. Oligomeric states involving multiple copies of the DQ2 heterodimer bound to a single copy of the multivalent 33-mer peptide are not observed. Together, these results suggest that the remarkable antigenicity of the 33-mer gluten peptide is primarily due to its unusually efficient ability to displace existing ligands in the HLA-DQ2 binding pocket, rather than an extremely low rate of dissociation.

Amides↗
PubMed2005

Tissue transglutaminase-mediated formation and cleavage of histamine-gliadin complexes: biological effects and implications for celiac disease.

Celiac disease is an HLA-DQ2-associated disorder characterized by an intestinal T cell response. The disease-relevant T cells secrete IFN-gamma upon recognition of gluten peptides that have been deamidated in vivo by the enzyme tissue transglutaminase (transglutaminase 2 (TG2)). The celiac intestinal mucosa contains elevated numbers of mast cells, and increased histamine secretion has been reported in celiac patients. This appears paradoxical because histamine typically biases T cell responses in the direction of Th2 instead of the Th1 pattern seen in the celiac lesions. We report that histamine is an excellent substrate for TG2, and it can be efficiently conjugated to gluten peptides through TG2-mediated transamidation. Histamine-peptide conjugates do not exert agonistic effects on histamine receptors, and scavenging of biologically active histamine by gluten peptide conjugation can have physiological implications and may contribute to the mucosal IFN-gamma response in active disease. Interestingly, TG2 is able to hydrolyze the peptide-histamine conjugates when the concentrations of substrates are lowered, thereby releasing deamidated gluten peptides that are stimulatory to T cells.

Amino Acid Sequence↗
PubMed2005

Pathomechanisms in celiac disease.

Celiac disease is an inflammatory disorder of the small intestine caused by an immune response to ingested wheat gluten and similar proteins of rye and barley. It affects at least 1 in 200 individuals, corresponding to roughly three million patients in Western Europe and Northern America alone. Data accumulated since the discovery of gluten specific T cells in the intestine of celiac disease patients the early 1990s have allowed the deciphering of the interplay between the triggering environmental factor, gluten, the main genetic risk factor, the HLA-DQ2/8 haplotypes and the autoantigen; the enzyme tissue transglutaminase (tTG). This established a key role of adaptive immunity orchestrated by lamina propria T cells responding to a set of gluten derived peptides. More recent work points to an important contribution of innate immunity triggered by a distinct gluten peptide and driven by the proinflammatory cytokine Interleukine-5 (IL-15). Together, these observations provide a unique explanation for the disease inducing capacity of gluten.

Celiac Disease↗
PubMed2005

Celiac disease genetics: current concepts and practical applications.

Celiac disease is a multifactorial disease with complex genetics. Both HLA and non-HLA genes contribute to the genetic component, but recent findings suggest that the importance of non-HLA genes might have been overestimated. No susceptibility genes other than HLA-DQ have yet been identified in celiac disease. In contrast to the meager knowledge regarding non-HLA genes, we have acquired a detailed understanding about which HLA genes are predisposing for disease, and how they are involved in the pathogenesis. This knowledge might pave the road for novel treatments for the disease. The role of HLA as a necessary, but not sufficient, genetic factor can moreover be used for diagnostic purposes to exclude a celiac disease diagnosis. The applicability of HLA genotyping is particularly useful for excluding celiac disease in family members or risk groups with fairly unbiased distribution of HLA alleles (ie, patients with Turner syndrome and patients with Down syndrome) and in patients with a clinical suspicion of celiac disease.

CD4-Positive T-Lymphocytes↗