Role of HLA class II genes in susceptibility and resistance to multiple sclerosis: studies using HLA transgenic mice

Multiple sclerosis (MS), an inflammatory and demyelinating autoimmune disease of CNS has both, a genetic and an environmental predisposition. Among all the genetic factors associated with MS susceptibility, HLA class II haplotypes such as DR2/DQ6, DR3/DQ2, and DR4/DQ8 show the strongest association. Although a direct role of HLA-DR alleles in MS have been confirmed, it has been difficult to understand the contribution of HLA-DQ alleles in disease pathogenesis, due to strong linkage disequilibrium. Population studies have indicated that DQ alleles may play a modulatory role in the progression of MS. To better understand the mechanism by which HLA-DR and -DQ genes contribute to susceptibility and resistance to MS, we utilized single and double transgenic mice expressing HLA class II gene(s) lacking endogenous mouse class II genes. HLA class II transgenic mice have helped us in identifying immunodominant epitopes of PLP in context of various HLA-DR and -DQ molecules. We have shown that HLA-DR3 transgenic mice were susceptible to PLP_91–110 induced experimental autoimmune encephalomyelitis (EAE), while DQ6 (DQB1*0601) and DQ8 (DQB1*0302) transgenic mice were resistant. Surprisingly DQ6/DR3 double transgenic mice were resistant while DQ8/DR3 mice showed higher disease incidence and severity than DR3 mice. The protective effect of DQ6 in DQ6/DR3 mice was mediated by IFNγ, while the disease exacerbating effect of DQ8 molecule was mediated by IL-17. Further, we have observed that myelin-specific antibodies play an important role in PLP_91–110 induced EAE in HLA-DR3DQ8 transgenic mice. Based on these observations, we hypothesize that epistatic interaction between HLA-DR and -DQ genes play an important role in predisposition to MS and our HLA transgenic mouse model provides a novel tool to study the effect of linkage disequilibrium in MS.     

HLA class II transgenic mice: models of the human CD4+ T-cell immune response

Summary: This review examines the field of current HLA class II transgenic mouse models and the individual approaches applied in production of these mice. The majority of these mice have been created with the objective of obtaining a disease model with clinical features mimicking human autoimmune disease. The development process of a different type of HLA class II transgenic mice, which are designed to function as a substitute for a normal human immune system in studies of human autoantigens, is described. Several HLA-DR4 transgenic lines with normally expressed HLA-DR4 molecules have been produced. To obtain adequate positive selection of the HLA-DR4-restricted CD4⁺ T-cell repertoire in these mice it is essential both to introduce a human CD4 transgene. and to delete the murine major histocompatibility complex (MHC) class II molecules. These HLA-DR4 transgenic mice have been used to determine the immunogenic CD4⁺ T-cell epitopes of several human autoantigenic proteins.     

HLA class II transgenic mice as models of human diseases

Summary: Predisposition co develop Various autoimmune disorders has been associated with certain HLA class II molecules but there is a lack of information on che pathophysiological rule of HLA genes in conferring susceptibility Various experimental animal models of autoimmune disease have been studied to address the role of immune response genes. To study the interactions involved between class II molecules (DQ and DR) and define the immunologic mechanisms in various diseases, we generated HLA-DR and DQ transgenic mice that lacked endogenous class II molecules. The HLA molecules in these mice arc expressed on the cell surface and can positively select CD4+ T cells expressing Various Vβ T-cell receptors (TCR). A peripheral tolerance is maintained co transgenic HLA molecules thus indicating that these molecules act as self, Mouse co stimulatory and accessory molecules can interact with the HLA-peptide-TCR complex leading to efficient T-cell activation. In this review, we describe immunogenetic models for human diseases using these transgenic mice. Our studies show that HLA class II transgene-restricted T cells recognize the immunodominant antigens and peptide epitopes, similar to HLA class II-restricted human T cells. Thus these mice provide powerful tools to understand the role of HLA class II molecules in predisposition and onset of human diseases and to develop immunotherapy and vaccines.     

Soluble HLA class I and class II antigens in patients with multiple sclerosis

Abstract: Soluble HLA class I (sHLA-I) and soluble HLA class II (sHLA-II) antigen levels during different stages of disease were investigated in paired serum and cerebrospinal fluid (CSF) samples from 37 patients with multiple sclerosis (MS) using ELISA and Western blot analysis. Soluble HLA-II antigens in the serum of untreated patients with the relapsing-remitting type of MS (RRMS) were found to be significantly elevated in acute relapse as compared to values obtained from patients under steroid treatment, in remission or healthy controls. No significant differences in circulating sHLA-I levels could be detected. In contrast, a trend towards increased intrathecal production of sHLA-I molecules in the CSF was observed in untreated RRMS patients in acute relapse, whereas the levels of soluble HLA-II antigens in the CSF were below the detection limit of the ELISA method. Our observations underline the presence of systemic immune activation in MS patients, as reflected in elevated serum sHLA-II antigen levels, and reveal a dichotomy between sHLA class I and II antigen production in the peripheral blood versus CSF in acute MS. Serial measurements of sHLA-II antigen levels might represent a non-invasive method to assess disease activity in MS patients.     

Increased reactivity to myelin oligodendrocyte glycoprotein peptides and epitope mapping in HLA DR2(15)+ multiple sclerosis

Multiple sclerosis (MS) is a central nervous system-specific inflammatory and demyelinating disease where a myelin-directed autoimmune response is thought to be pathogenetically relevant. Myelin oligodendrocyte glycoprotein (MOG) is a surface-exposed minor myelin component that is a prime candidate autoantigen. We have investigated peripheral blood lymphocyte responses to synthetic 15 – 26 amino acids long overlapping MOG peptides in 20 MS patients and 14 healthy controls with the MS-associated HLA haplotype DR2(15). There were significantly increased responses, in terms of numbers of cells secreting IFN-γ detected by Elispot in response to several MOG-derived peptides in the MS patients, but not the healthy controls. MOG peptide 63 – 87 evoked the strongest response, and the stimulatory property of this peptide was confirmed in additional DR2(15)+ MS patients where a peptide concentration-dependent proliferative response, which was inhibited by the addition of anti-HLA class II antibodies, was observed. This is the first work detailing putative immunodominant T cell epitopes of MOG in DR2(15)+ MS patients.     

In vivo activation of myelin oligodendrocyte glycoprotein-specific T cells in healthy control subjects

Collagen-induced arthritis (CIA) is a murine model of autoimmune-mediated polyarthritis. CIA can be prevented by the administration (intravenously) of CII, inducing regulatory CD4+ T cells which produce Th2 cytokines. However, the relative importance of IL-4 in suppressing arthritis remains unclear. To address this question, a neutralizing monoclonal antibody to IL-4 was given to mice treated with tolerized, CII-specific cells. The antibody significantly reversed the expected suppression of arthritis. Moreover, CII administered intravenously to DBA/1 IL4-/- mice (developed by backcrossing C57B1/6 IL4-/- to wild-type DBA/1 mice) was completely ineffective in suppressing disease. These data support the importance of IL-4 in the regulation of autoimmune arthritis. Compensatory increases in mRNA message for other Th2 cytokines were observed, but they did not restore suppression of arthritis. Antibodies to CII, mostly IgG2a, were increased in IL4-/- mice. These studies represent a unique opportunity to analyze the role of IL-4 and its absence on an autoimmune murine model of arthritis.     

Skewed autoantibody reactivity to the extracellular domain of myelin oligodendrocyte glycoprotein in multiple sclerosis

Myelin oligodendrocyte glycoprotein (MOG) is found to induce both autoreactive T-cell and antibody responses associated with demyelinating pathology and is implicated in the pathogenesis of multiple sclerosis (MS). In this study, we addressed the potential association of anti-MOG immune responses with MS by examining, comparatively, both the T-cell and antibody responses to recombinant MOG fragments in MS patients and healthy subjects. T cells recognizing MOG were detected in MS patients as well as in healthy subjects, and their precursor frequency in the blood was not increased in patients with MS. MOG-reactive T cells isolated from both MS patients and healthy subjects exhibited a similar cytokine profile, producing interleukin (IL)-4, IL-10 and tumour necrosis factor (TNF), but not interferon-gamma (IFN-gamma), and recognized predominantly the extracellular (residues 1-60) and the transmembrane/cytoplasmic (residues 154-218) domains of MOG. In contrast, anti-MOG antibodies derived from MS patients displayed a skewed reactivity pattern, even though the occurrence and titres of serum anti-MOG antibodies were only slightly elevated in MS patients. MS-derived autoantibodies were predominantly directed at the 1-60 region of MOG, while naturally occurring anti-MOG antibodies derived from healthy individuals reacted selectively to the 154-218 domain. These differences were statistically significant. The findings of this study are consistent with the presence of anti-MOG antibodies within demyelinating lesions of MS and their role in the induction of demyelinating pathology in animal models. The study has important implications in the understanding of the autoimmune processes in MS.     

HLA class II polymorphism influences onset and severity of pathology in Schistosoma mansoni-infected transgenic mice

Genetic factors that might influence susceptibility or resistance in naive individuals and early-stage pathology in schistosomiasis are difficult to study in clinical trials, since in areas where the disease is endemic the first contact with the parasite occurs most often at very early ages. Therefore, four strains (DR1.Abeta degrees, DR2.Abeta degrees, DQ8.Abeta degrees, and DQ6.Abeta degrees ) of major histocompatibility complex class II-deficient mice (Abeta degrees ), transgenic for different HLA alleles, have been used to evaluate the potential role of HLA class II polymorphism in the onset of the infection by Schistosoma mansoni. The survival rates and parasitological and immunological parameters after infection were evaluated and compared against the control values obtained with Abeta degrees mice. All four mouse strains used in this study were able to generate a specific immune response against S. mansoni antigens (cytokine production and antibody production). However, only mice expressing DR alleles survived until the chronic stage of the infection and were able to mount protective granulomatous response avoiding hepatic damage, presenting predominant gamma interferon production. In contrast, strains expressing DQ alleles revealed an impairment in generating effective granulomas, resulting in earlier death, which was associated with an impaired hepatic granulomatous response and liquefactic necrosis, reflecting the influence of HLA polymorphism in the establishment of protective response in the early stage of infection.     

Genetic factors and multiple sclerosis in the Moroccan population: A role for HLA class II

Background and objective

Multiple sclerosis (MS) is an autoimmune inflammatory demyelinating disease of the central nervous system that mainly affects young adults. The association between susceptibility to MS and HLA class II genes, in particular the DRB1*15 allele, has been reported in diverse ethnic groups. The aim of our study was to investigate the distribution of HLA-DRB1* and -DQB1* alleles in Moroccan population and their implication in the susceptibility to the disease.

Methods

Fifty-seven MS patients were compared to 172 healthy controls unrelated to one another and matched by age, sex and ethnic origin. HLA class II (DRB1* and DQB1*) typing was performed by PCR-SSP and/or Luminex (PCR-SSO). Allelic and haplotypic frequencies, P-values, odds ratio (OR) and 95% confidence interval (CI) were calculated using the software SPSS.

Results

A significant increase of DRB1*15 allele frequency (17.6% vs 8.4%, OR = 2.67, 95% CI = 1.36–5.23, P = 0.004) and HLA-DRB1*15-DQB1*06 haplotype (8.8% vs 4.08%, OR = 2.78, 95% CI = 1.41–5.48, P = 0.002) were observed in Moroccan MS patients. No association of the DR15 allele with sex or age at onset was appreciated. Concerning HLA-DQB1* alleles, no significant difference between patients and controls was found.

Conclusions

Our results reveal a role for HLA-DRB1*15 allele molecules in the predisposition of Moroccan patients to MS. Although this study should be confirmed on a larger sample size, it analyzes for the first time the possible role of a genetic marker for susceptibility to MS in Moroccan population.     

Reduced suppressive effect of CD4+CD25high regulatory T cells on the T cell immune response against myelin oligodendrocyte glycoprotein in patients with multiple sclerosis

Immunoregulatory T cells of (CD4+)CD25+ phenotype suppress T cell function and protect rodents from organ-specific autoimmune disease. The human counterpart of this subset of T cells expresses high levels of CD25 and its role in human autoimmune disorders is currently under intense investigation. In multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system (CNS), the activation of circulating self-reactive T cells with specificity for myelin components is considered to be an important disease initiating event. Here, we investigated whether MS is associated with an altered ability of (CD4+)CD25high regulatory T cells (Treg) to confer suppression of myelin-specific immune responses. Whereas Treg frequencies were equally distributed in blood and cerebrospinal fluid of MS patients and did not differ compared to healthy controls, the suppressive potency of patient-derived (CD4+)CD25high T lymphocytes was impaired. Their inhibitory effect on antigen-specific T cell proliferation induced by human recombinant myelin oligodendrocyte protein as well as on immune responses elicited by polyclonal and allogeneic stimuli was significantly reduced compared to healthy individuals. The effect was persistent and not due to responder cell resistance or altered survival of Treg, suggesting that a defective immunoregulation of peripheral T cells mediated by (CD4+)CD25high T lymphocytes promotes CNS autoimmunity in MS.     

Tolerance to class II MHC in transgenic mice

Transgenic mice offer new possibilities in experimental techniques for understanding the familiar questions of T cell development and the selection of the T cell repertoire. As a powerful method to manipulate gene expression in the whole animal, precisely defined in vivo models can be developed. In our own studies, we have used transgenic mice with targeted expression of I-E and new monoclonal antibodies defining T cell receptors specific for class II I-E molecules. In the thymus, our results suggest that thymic epithelium has significant tolerance inducing capability, but the mechanism may be different from the clonal deletion induced by bone marrow derived cells. In the periphery, our results suggest that tolerance to tissue restricted antigens is not induced by clonal deletion. Instead, clonal paralysis may be an important mechanism for both inducing and maintaining peripheral tolerance.     

Induction of CTL response by a minimal epitope vaccine in HLA A*0201/DR1 transgenic mice: dependence on HLA class II restricted T(H) response

CTL play a pivotal role in the immune response during viral infections. In this study, the HLA class II restricted T(H) requirement for optimal in vivo induction of HLA class I restricted CTL responses has been investigated. Towards this goal, transgenic mice expressing both HLA class I (A*0201 or A2.1) and class II (DRB1*0101 or DR1) molecules have been derived. Immunization of these mice with an HLA A*0201-restricted and CMV-specific CTL epitope (pp65(495-503)), and either of three different tetanus toxin-derived MHC class II-binding T(H) epitopes, resulted in a vigorous CTL response. CTL specific for the pp65(495-503) epitope were dramatically enhanced in mice expressing both the HLA-DR1 and HLA-A*0201 transgenes. Notably, preinjection of three TT peptides (TT(639-652), TT(830-843), and TT(947-967)) increased the capability of HLA A*0201/DR1 Tg mice to respond to subsequent immunization with the T(H) + CTL peptide mixture. These results indicate that the use of HLA A*0201/DR1 Tg mice constitute a versatile model system (in lieu of immunizing humans) for the study of both HLA class I and class II restricted T-cell responses. These studies provide a rational model for the design and assessment of new minimal-epitope vaccines based on their in vivo induction of a pathogen-specific CTL response.     

T cell epitope spreading to myelin oligodendrocyte glycoprotein in HLA-DR4 transgenic mice during experimental autoimmune encephalomyelitis

Epitope spreading has been implicated in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) and human multiple sclerosis (MS). T cell epitope spreading has been demonstrated in rodents for myelin basic protein (MBP) and proteolipid protein (PLP) determinants, but not for myelin oligodendrocyte glycoprotein (MOG), another important myelin antigen. Moreover, the role of human autoimmunity-associated MHC molecules in epitope spreading, including HLA-DR2 and DR4, has not been formally examined. To address these questions, we investigated epitope spreading to MOG determinants in HLA-DR4 (DRB1*0401) transgenic mice during EAE. The data show that upon induction of EAE in HLA-DR4 transgenic mice with the immunodominant HLA-DR4-restricted MOG peptide 97-108 (MOG(97-108); TCFFRDHSYQEE), the T cell response diversifies over time to MOG(181-200) (core: MOG(183-191); FVIVPVLGP) and MBP. The spreading epitope MOG(181-200) binds with high affinity to HLA-DRB1*0401 and is presented by human HLA-DRB1*0401+antigen presenting cells. Moreover, this epitope is encephalitogenic in HLA-DRB1*0401 transgenic mice. This study demonstrates intra- and intermolecular epitope spreading to MOG and MBP in "humanized" HLA-DR4 transgenic mice.     

HLA class II-associated genetic susceptibility in multiple sclerosis: a critical evaluation

Multiple sclerosis (MS) has, since the 1970s, been known to be associated with the HLA-Dw2 and -DR2 specificities in Caucasian Europeans and North Americans. By the use of genomic typing techniques, the association has been specified to be with the DRw15,DQw6,Dw2, i.e. the DRB1*1501-DQA1*0102-DQB1*0602 haplotype. A significant DPw4 association in Scandinavian MS patients has been described in one report. However, this association has not been confirmed in several subsequent studies with patients from the same and other ethnic groups. During the last few years several reports, based on serological, RFLP and PCR-SSO data, have suggested that the HLA class II-associated MS susceptibility gene(s) may be more closely associated with the DQ than with the DR subregion. The observations that the HLA-DQB1 genes of MS patients share long stretches of sequence motifs and also carry DQA1 alleles encoding glutamine at position 34 of the DQ alpha chain have received considerable attention. It has been suggested that the susceptibility to develop MS might be determined by the corresponding DQ alpha-beta heterodimers either encoded in cis or in trans. We have investigated these issues in a large group of Swedish MS patients (n = 179). We found that the associations with the suggested DQB1 sequences and position 34 of the DQ alpha chain were due to linkage disequilibrium and secondary to the association with the DRw15,DQw6,Dw2 haplotype (p less than 10(-9) and p less than 10(-8), respectively). No overrepresentation of the implicated DQ alpha-beta heterodimers was observed in DRw15,DQw6,Dw2-negative patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genes in the HLA class I region may contribute to the HLA class II-associated genetic susceptibility to multiple sclerosis

In order to analyze whether loci in the human leukocyte antigen (HLA) class I region may contribute to the HLA class II-associated genetic susceptibility to multiple sclerosis (MS), we examined selected microsatellite markers in 177 Nordic sib-pair families, 222 British sib-pair families, 323 sporadic Norwegian MS patients and 386 Norwegian controls. All samples were, in addition, genotyped for the HLA-DR DQ haplotype, and the Norwegian case-control samples were also typed for HLA-A and -B loci. In the Norwegian sporadic MS patients association was seen with HLA-A, HLA-B, and with the D6S265 marker, located 100 kb centromeric to HLA-A. Associations with HLA-A and D6S265 loci were also suggested when restricting the analysis to HLA-DR15 haplotypes. In the sib-pair data a similar trend was seen with marker D6S265. Higher genotypic relative risk (GRR) was found for individuals who carry both HLA-DR15 and -A3 (GRR = 15), compared to those who carry only HLA-DR15 (GRR = 7), only HLA-A3 (GRR = 3) or none of these alleles (GRR = 1). The highest risk was conferred by a combination of HLA-DR15 and -A3 (odds ratio (OR) = 5.2). These results suggest that HLA-A or a gene in linkage disequilibrium with it may contribute to the HLA class II-associated genetic susceptibility to MS.     

Multiple sclerosis: a modifying influence of HLA class I genes in an HLA class II associated autoimmune disease

Multiple sclerosis (MS) is a presumed autoimmune disease of the central nervous system, shown to be associated with the HLA class II haplotype DRB1*15,DQB1*06. Carrying the HLA class II haplotype DRB1*15,DQB1*06 increases the risk of MS by 3.6. By adopting a polymerase chain reaction (PCR)-based typing technique for HLA class I and class II genes, 200 Swedish MS patients and 210 Swedish healthy controls were analysed for their HLA alleles. Additional HLA class I alleles that increase and decrease the genetic susceptibility to MS were identified. The HLA-A*0301 allele increases the risk of MS (odds ratio=2.1) independently of DRB1*15,DQB1*06. HLA-A*0201 decreases the overall risk (odds ratio= 0.52) and the presence of A*0201 reduces the risk of MS for DRB1*15,DQB1*06 carriers from 3.6 to 1.5. Our findings are the first to identify a major modulating effect of HLA class I alleles on the susceptibility to a human autoimmune disease; a phenomenon that has previously only been observed in animal models.     

髓鞘修复与多发性硬化

多发性硬化（MS）是以中枢神经系统炎性脱髓鞘为特征的自身免疫性疾病,神经功能障碍与髓鞘和轴索损伤有关。MS动物模型研究认为：髓鞘修复是治疗MS极有前景的途径。中枢神经系统存在少突胶质细胞前体细胞（OPCs）,在髓鞘修复和再生过程起关键作用。由于MS病人OPC分化受抑制,因此,在髓鞘再生过程中调控OPCs分化是髓鞘修复的重点。另外,移植外源性的髓鞘形成细胞促进髓鞘修复和神经再生,是修复MS脱髓鞘和轴索损伤的重要途径。