Background: The major histocompatibility complex (MHC) molecules play an important role in the immune response regulation and in the maintenance of the immune homeostasis. Regulation of their expression is therefore a key factor influencing the adaptive immune response. DNA methylation of gene regulatory regions is one of the mechanisms of gene expression control that affects the accessibility of DNA to transcription factors. Ageing is connected with changes in DNA methylation and increased predisposition to autoimmune diseases in older age could be associated with changes in MHC class II genes methylation. Aims: The aim of this diploma thesis is to analyze the methylation profile of DQA1 and DQB1 genes regulatory regions and to compare its differences between the generations and between individual alleles. The next aim is to compare DQA1 mRNA expression between the generations and between single alleles. Methods: DNA and RNA were isolated from blood of three age group donors. DNA was converted by the bisulfite treatment and regulatory regions of HLA class II genes were amplified and cloned into bacteria. Positive clones were sequenced and then analyzed. RNA was reverse transcribed and its expression level was determined by real-time PCR. Results: Statistically significant differences were found by...

L'induction d'une immunité efficace contre les tumeurs nécessite de recruter des lymphocytes T CD4+ auxiliaires et spécifiques. De ce fait, les peptides de tumeurs présentés par les molécules HLA II sont de potentiels candidats pour l'immunothérapie anticancéreuse. Le but de ce travail a été l'identification de nouveaux épitopes T CD4+ dérivés de trois antigènes différents : Trag-3 (Taxol Resistant Associated Gene) (un travail effectué en collaboration), un antigène spécifique des tumeurs ; la Survivine, un antigène surexprimé ; et l'ensemble de la famille MAGE-A, une famille d'antigènes spécifiques des tumeurs. Toutefois, l'utilisation d'épitopes peptidiques dans la vaccination nécessite de tenir compte du polymorphisme des molécules HLA afin de couvrir le maximum d'individus. Dans cette optique, nous avons appliqué deux stratégies différentes d'identification de peptides, à savoir : 1) identifier des peptides présentés par plusieurs molécules de HLA II (ces peptides sont appelés épitopes promiscuous). Cette stratégie a été appliquée à l'antigène Trag-3 et à la Survivine ; 2) identifier des peptides présentés par les molécules les plus représentées dans la population : les molécules HLA-DP4. Cette stratégie a été appliquée à la famille d'antigènes MAGE-A. Pour chercher les épitopes promiscuous, des peptides chevauchants couvrant l'intégralité de la séquence de Trag-3 et de la Survivine ont tous été synthétisés et testés pour leur capacité de liaison vis-à-vis de 12 molécules HLA-II (DR et DP). L'immunogénicité de peptides pouvant se lier avec plusieurs molécules de HLA II a été évaluée par la génération de lymphocytes T CD4+. Finalement, un peptide de Trag-3 (P34-48) et 4 peptides de la Survivine ont été mis en évidence. De plus, des réponses spontanée vis-à-vis du peptide Trag-3 34-48 ont été détectées dans les patients atteints de cancers. Pour chercher les épitopes restreints au HLA-DP4, nous avons d'abord établi un programme de prédiction de ligands potentiels de HLA-DP4. 9 gènes de la famille de MAGE-A ont été analysés et 12 peptides prédits ont été finalement synthétisés et testés dans les tests de liaison de HLA-DP4. 7 peptides ayant une meilleure activité avec les molécules de HLA-DP4 ont été sélectionnés pour évaluer leur immunigénicité in vitro. Finalement, 2 peptides de MAGE-A1 et un peptide de MAGE-A12 ont été mis en évidence qu'ils contiennent des épitopes naturellement présentés et apprêtés dans la présentation de l'antigène natif. En conclusion, tous les peptides identifiés dans ce travail présentent tous un intérêt pour la conception des vaccins peptidiques. Nous avons aussi proposé une méthode de prédiction de liaison de HLA-DP4 qui facilite significativement la sélection des peptides..

Les maladies immunitaires chroniques incluant les maladies auto-immunes et inflammatoires touchent 20 à 25% de la population des pays occidentaux. La comparaison des taux de concordance chez les jumeaux ou l’histoire familiale de sujets atteints de la maladie cœliaque (maladie auto-immune de l’intestin) ou de l’œsophagite éosinophilique (maladie inflammatoire de l’œsophage) indiquent que des facteurs génétiques et environnementaux interviennent dans la susceptibilité à ces maladies. Cependant, ces études ne distinguent pas de manière claire la prédisposition génétique selon l’hétérogénéité clinique (enfants versus adultes) ou ethnique (stratification des populations). Méthodes. Les haplotypes HLA de prédisposition à la maladie cœliaque et les polymorphismes des gènes candidats IL-13 (R130Q), IL-5 (-746 T/G) et IL-5R (-80A/G) impliqués dans la physiopathologie de l’œsophagite éosinophilique, ont été caractérisés par la technique PCR-SSP sur l’ADN génomique. Résultats: Nos études familiales et cas-contrôles réalisées chez une population Québécoises avec un fond génétique très homogène nous a permis : i) d’éviter le problème de stratification des populations, ii) de confirmer que les gènes HLA sont également associés à la maladie cœliaque (enfants et adultes) au Québec comme dans les autres populations Caucasiennes, iii) de mettre en évidence le rôle du gène IL-13 dans la prédisposition à l’œsophagite éosinophilique (garçons et filles) et d’exclure les gènes IL-5 et IL-5R comme facteurs de susceptibilité dans notre population. Conclusion: Ce travail confirme pour la première fois l’impact des gènes HLA dans la prédisposition à la maladie cœliaque et le rôle du facteur génétique dans l’œsophagite éosinophilique chez une population Canadienne Française avec un fond génétique ayant un fort effet fondateur. / Chronic immune diseases including autoimmune and inflammatory diseases affect 20 to 25% of Western country population. The higher concordance of disease in twins or in first-degree relative of patients with celiac disease (bowel autoimmune disease) or eosinophilic esophagitis (inflammatory disease of the esophagus) indicate that genetic and environmental factors are involved in susceptibility to these diseases. However, these studies do not distinguish clearly genetic predisposition according to clinical heterogeneity (children versus adults) or ethnicity (population stratification). Methods: HLA haplotypes predisposing to celiac disease and polymorphisms of candidate genes IL-13 (R130Q), IL-5 (-746 T / G) and IL-5R (-80A / G) involved in physiopathology of eosinophilic esophagitis, have been evaluated by PCR-SSP on genomic DNA. Results: Our familial and case-control studies performed in populations having a very similar genetic background with a strong founder effect, allowed us: i) to avoid the problem of population stratification, ii) to confirm that HLA genes are also associated with celiac disease in Quebec (children and adults) as in other Caucasian populations, iii) to identify the role of IL-13 gene in susceptibility to eosinophilic esophagitis (boys and girls) and to exclude IL-5 and IL-5R genes as susceptibility factor in our population. Conclusion: This study confirms for the first time the impact of HLA genes in predisposition to celiac disease and the role of genetic factors in eosinophilic esophagitis in a French Canadian population with a strong founder effect.

Background: Type 1 diabetes mellitus is a multifactorial disease caused by beta cell destruction of Langerhans pancreatic islets. From the genetic aspect the main predisposition lays on HLA class II genes (40 - 50%), molecules of which present exogenous peptides to CD4+ T lymphocytes. Enviromental factors play a crucial role in the etiopathogenesis of T1DM. Through epigenetic regulation (e.g. DNA methylation) the genetic and enviromental factors communicate. The level of methylation in the regulatory regions can significantly affect expression of these genes. Aims: The aim of the diploma thesis was to define methylation profile of HLA DQB1 alleles in type 1 diabetes mellitus patients and determine their expression. Methods: The genotyping of HLA class II genes (HLA-DRB1, HLA-DQA1, HLA-DQB1) was performed using sequence specific primers. DNA was treated with sodium bisulfite, regulatory region of HLA DQB1 was amplified and cloned into E.coli, strain DH5α/XL1-Blue. Positive clones were sent for sequencing and results analyzed. RNA was transcribed to cDNA by reverse transcription and the level of expression was analyzed by quantitative PCR. Results: Statistically significant differences were found in total methylation of DQB1*0201 and *0302 alleles in the B section of DQB1 gene. Difference in...

Introduction: Glycoproteins of the major histocompatibility complex (MHC) are an irreplaceable part of immune response regulation and immune homeostasis maintenance. The regulation of the expression plays an important role in adaptive immune response. Recently, DNA methylation in regulatory areas, crucial for DNA availability to transcription factors, is one of the most researched mechanisms of this type of regulation. The DNA methylation is, among others, related to the aging processes. Increased predisposition age-related immunosenescence in higher age could result from the changes in methylation status of regulatory areas of MHC class II genes. Aims: The aim of this thesis is to analyze the methylation status of regulatory areas of DQB1 gene and to compare the differences between generations and specific alleles. The differences in the levels of DQB1 gene mRNA transcription between generations and specific alleles is also compared. Methods: Both DNA and RNA were isolated from blood samples obtained from donors of three different age groups. DNA was genotypized and modified by bisulfite conversion. The regulatory areas of DQB1 genes were then amplified and subcloned into bacteria. The positive clones were selected and subjected to DNA methylation analysis. RNA was reverse transcribed into cDNA...

Introduction: Recent findings about the pathogenesis of glaucoma have already demonstrated the presence of some specific autoimmune mechanisms. It has also been shown that autoimmune diseases often manifest in co-occurrence, such as celiac disease and type 1 diabetes mellitus or psoriasis. This association can be explained by sharing some of the risk variants of HLA molecules class II. Considering glaucoma an autoimmune disease, the question raises how the glaucoma genetic risk factors affect the phenotype of another autoimmune disease or vice versa, whether genetic risk variants associated for example with celiac disease can affect the glaucoma phenotype. Aims: The aims of this study were to i) identify possible genetic risk markers associated with the development of glaucoma, based on the available literature, and to map their occurrence among members of a three-generation family suffering from glaucoma and multiple autoimmune diseases, ii) find carriers of HLA-DQ2/DQ8 among the members of the same family, iii) verify whether an individual's genotype correlates with his/her phenotype, and iv) determine the potential effect of specific HLA alleles on the glaucoma phenotype. Material and methods: This study used DNA samples derived from 34 members of a three-generation family, in which coeliac...

Abstract Background: Type 1 diabetes (T1D) is a multifactorial autoimmune disease. Its incidence in Europe is continuously rising. The highest T1D risk is associated with HLA (human leukocyte antigen) class II genes. HLA class II molecules play a key role in regulation of immune response. They contribute to the selection of T cell repertoire by presenting antigenic peptides to the CD4+ T lymphocytes. HLA class II expression is controlled by regulatory module that is situated 150 - 300 base pairs upstream of the transcription- initiation site in all HLA class II genes. Polymorphisms in this region are linked to some autoimmune diseases. There were identified several promoter alleles (named QAP) in the HLA DQA1 gene promoter region. Most of the polymorphisms appear to be conserved within haplotype. Individual QAP alleles may have a different promoter strength by which they influence expression of HLA DQA1 gene alleles. Promoter strength can be modulated by DNA methylation. Aims:Our aim was to define methylation profile of HLA DQA1 promoters and determine the mRNA expression of individual alleles of HLA DQA1 gene in T1D patients. The mRNA expression level of HLA DQA1 gene alleles was determined using quantitative PCR. Methods: 30 diabetic pacients (age range 21 to 76 years), were included in this pilot...

Introduction: At our post-genomic era the studies of epigenetic regulation constitutes one of the tools for understanding the function of genes. Epigenetic regulation can directly control the temporal and spatial gene activity or silencing. The molecular basis of these regulations are DNA bases modifications, chromatin remodeling and RNA interference. At the same time, these mechanisms have a special way of transferring genetic information to subsequent generations called epigenetic inheritance. It has been proven epigenetic deregulation of certain genes as cause for many disease. For this reason, the study of epigenome HLA genes seems particularly important because these genes play a fundamental role in regulating the immune system. Aims: The aim of this work is to create a description of epigenetic modifications within families. It is an analysis of histone modifications and DNA methylation in the promoter region of the gene HLA DQA1. The aim was also to compare the differences in epigenetic modifications between alleles and compared the differences in these modifications between generations. The results will be compared with the analysis of the level of expression of the gene HLA DQA1. Methods: From collected peripheral blood of donors were isolated DNA, RNA, and leukocytes. DNA was used for...