HLAs and genes in Japanese patients with multiple sclerosis: evidence for increased frequencies of HLA-Cw3, HLA-DR2, and HLA-DQB1*0602

Mediterranean and Amerindian MHC class II alleles are associated with multiple sclerosis in Mexicans

OBJECTIVES

Human leukocyte antigen (HLA)-DRB1, DQA1, DQB1 allele typing was performed in Mexicans Mestizos with multiple sclerosis (MS) to define the HLA class II alleles associated with the disease in this population.

METHODS

Patients (n = 51) diagnosed according to the Poser criteria and a group of 173 unrelated healthy subjects were studied. PCR-SSOP and PCR-SSP were used for genotyping.

RESULTS

Fifty five percent of the patients were females. The mean age at disease onset was 27 years. A relapsing-remitting disease was the most frequent type of MS (67%). A significant association of DRB1*0403 (OR = 5.68) with MS was shown. DRB1*0802 was also involved in susceptibility (OR = 2.41). An excess of DRB1*0802 homozygotes was observed in patients (P = 0.005), this genotype being in genetic equilibrium in controls.

CONCLUSIONS

Two novel class II associations are described in Mexicans with MS: DRB1*0403 and DRB1*0802. Both alleles share with DRB1*1501, valine-86 and negatively charged amino acids, in the DRB1-anchoring motif of pocket 4.

Molecular diversity of HLA-Cw alleles in the Maratha community of Mumbai, Maharashtra, western India

Recent advances suggest a significant role for the HLA-C locus as a target of alloreactions after bone marrow transplantation. The biological importance of products of the HLA-C locus, both as transplant antigens and as ligands for natural killer (NK) cells, is well established. A total of 10 different serologically defined HLA-Cw antigen specificities (Cw1-Cw10) are encoded by the C locus; however, there are now 151 different alleles that can be identified by molecular methods. Serological definition of Cw alleles therefore includes 20-50% blanks, which cannot be detected by the available antisera. We used the molecular method of polymerase chain reaction (PCR)-based sequence-specific amplification and probe hybridization to define Cw alleles in 91 individuals from the Maratha community, and compared the data with data for 92 serologically typed Maratha individuals from India. We identified Cw*12, Cw*14, Cw*15, Cw*16 and Cw*18, along with the serologically identified Cw*01, Cw*02, Cw*03, Cw*04, Cw*06 and Cw*07 alleles. The HLA-Cw blank allele frequency in the Maratha was reduced from 0.5706 to 0.00. Furthermore, by using a molecular technique, it was possible to identify novel allele subtypes, such as Cw*0104, Cw*0203 and Cw*0707, and a high frequency of Cw* 1801 in the Maratha community compared with other Indian and world populations. Our results will have clinical implications in related and unrelated HLA-matched bone marrow transplantation in India.

Evidence for novel DRB1*15 allele association among clinically definite multiple sclerosis patients from Mumbai, India

Multiple sclerosis (MS) is a clinically heterogeneous demylinating disease and an important cause of acquired neurologic disability. MS has been reported from different regions of India and its infrequency has been attributed to have genetic implications. Further, a high incidence of MS and its human leukocyte antigen B12 (HLA-B12) associations have been reported among highly inbred Parsi population from Mumbai. However, consistent HLA associations have not been reported from India. We analyzed the HLA-B, -Cw, and -DRB1 allele associations among 23 clinically definite Western Indian non-Parsi MS patients and compared them with 146 ethnically matched clinically normal individuals. HLA serologic (A, B, and Cw) as well as molecular (DRB1) typing methodology was followed. The study revealed a significant increase of HLA-A11 (24% vs. 13%; OR = 2.6; EF = 0.14; 95%CI = 1.1-3.05), B16 (4.3% vs 0.3%; OR = 13.8; EF = 0.03; 95% CI = 1.19-134.44), Cw7 (15.2% vs 3.7%; OR = 5.46; EF = 0.12; 95% CI = 0.944-17.86), and DRB1*15 (21.7% vs 2.2%; OR = 16.15; EF = 0.19; 95% CI = 1.33-68.64). Further molecular subtyping of HLA-DRB1*15 among the patients revealed two novel alleles, DRB1*1506 (20%) and DRB1*1508 (30%), along with the commonly reported DRB1*1501 (50%) for the first time in MS patients that were hitherto unidentified from other parts of India and world as well. This study reveals that there is a complexity of the genetic susceptibility to MS in different populations studied and reported.

Genetics of multiple sclerosis: linkage and association studies

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system caused by an interplay of environmental and genetic factors. The only genetic region that has been clearly demonstrated by linkage and association studies to contribute to MS genetic susceptibility is the human leukocyte antigen (HLA) system. The majority of HLA population studies in MS have focused on Caucasians of Northern European descent, where the predisposition to disease has been consistently associated with the class II DRB1*1501-DQA1*0102-DQB1*0602 haplotype. A positive association with DR4 was detected in Sardinians and in other Mediterranean populations. Moreover DR1, DR7, DR11 have been found to be protective in several populations. Systematic searches aimed at identifying non-HLA susceptibility genes were undertaken in several populations by means of linkage studies with microsatellite markers distributed across the whole genome. The conclusion of these studies was that there is no major MS locus, and genetic susceptibility to the disease is most likely explained by the presence of different genes each conferring a small contribution to the overall familial aggregation. The involvement of several candidate genes was tested by association studies, utilizing either a population-based (case control) or a family-based (transmission disequilibrium test) approach. Candidate genes were selected mainly on the basis of their involvement in the autoimmune pathogenesis and include immunorelevant molecules such as cytokines, cytokine receptors, immunoglobulin, T cell receptor subunits and myelin antigens. With the notable exception of HLA, association studies met only modest success. This failure may result from the small size of the tested samples and the small number of markers considered for each gene. New tools for large scale screening are needed to identify genetic determinants with a low phenotypic effect. Large collaborative studies are planned to screen several thousands of patients with MS with several thousands of genetic markers. The tests are increasingly based on the DNA pooling procedure.

Molecular and cellular analyses of HLA class II-associated susceptibility to autoimmune diseases in the Japanese population

Abstract It is well known that individuals who are positive for particular HLA class II alleles show a high risk of developing autoimmune diseases. HLA class II molecules expressed on antigen-presenting cells present antigenic peptides to CD4(+) T cells. Their extensive polymorphism affects the structures of peptides bound to HLA class II molecules to create individual differences in immune responses to antigenic peptides. In order to gain a better understanding of mechanisms of the association between HLA class II alleles and susceptibility to autoimmune diseases, it is important to identify self-peptides presented by disease-susceptible HLA class II molecules and triggering disease-causative T cells. Many of the autoimmune diseases are observed in all ethnic groups, whereas the incidence of diseases, clinical manifestations and disease-susceptible HLA class II alleles are different among various ethnic groups for some autoimmune diseases. These phenomena suggest that differences in autoimmune self-peptide(s) in the context of disease-susceptible HLA class II molecules may cause these differences. Therefore, comparisons among disease-susceptible HLA class II alleles, autoantigenic peptides, and clinical manifestations of autoimmune diseases in different ethnic groups would be helpful in elucidating the pathogenesis of the diseases. In this review, we describe our recent findings on (1) the uniqueness of both clinical manifestations and the HLA-linked genetic background of Asian-type (opticospinal form) multiple sclerosis, (2) the characteristics of glutamic acid decarboxylase 65 (GAD65) or β2-glycoprotein I (β2-GPI) autoreactive T cells in Japanese patients with insulin-dependent diabetes mellitus (IDDM) or anti-β2-GPI antibody-associated autoimmunity, respectively, and (3) the generation of an efficient delivery system of peptides to the HLA class II-restricted antigen presentation path-way by utilizing a class II-associated invariant chain peptide (CLIP)-substituted invariant chain, which may be applicable to an evaluation of the "molecular mimicry hypothesis" for the activation of autoreactive T cells.

Molecular mimicry and multiple sclerosis--a possible role for degenerate T cell recognition in the induction of autoimmune responses

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system. The etiology is unknown, but several lines of evidence support the hypothesis that the pathogenesis is mediated by autoreactive T lymphocytes. Molecular mimicry has been proposed as a possible mechanism for the development of an autoimmune response to myelin antigens. According to this model, an immune reaction to self antigens could be initiated by T cells that cross-react with infectious agents that "mimic" the autoantigen, i.e. they share immunologic epitopes. It was previously thought that, in order for a cross-reaction of T cells to two different antigens to occur, a substantial amino acid sequence homology between the two antigens was required. More recent studies on the basic mechanisms of T cell antigen recognition have shown that, at least for some T cell clones, antigen recognition is more "degenerate" and sequence homology is not required for crossreactivity to occur. This article reviews the relevance of these recent advances in basic T cell receptor immunology to the occurrence of autoimmunity in the central nervous system.

Peptide-based molecular analyses of HLA class II-associated susceptibility to autoimmune diseases

Recent advances in knowledge of crystal structures of MHC class II molecules has advanced understanding of the molecular basis for interactions between peptides and HLA class II molecules. Polymorphism of HLA class II molecules influences structures of peptides bound to HLA class II molecules. To better understand mechanisms related to particular HLA class II alleles and autoimmune diseases, it is important to identify self-peptides presented by disease-susceptible HLA class II molecules and triggering disease-causative autoreactive T cells. Autoimmune diseases occur in Caucasians, Blacks and Asians, albeit with a different incidence. In some autoimmune diseases, disease-susceptible HLA class II alleles are closely related but different, and clinical manifestations of diseases differ among ethnic groups. These phenomena strongly suggest that difference in autoimmune self-peptide(s) in the context of disease-susceptible HLA class II molecules may explain the different clinical manifestations of diseases. Therefore, a comparison among disease-susceptible HLA class II alleles, autoimmune self-peptides and clinical manifestations of autoimmune diseases in different ethnic groups would be instructive. We directed efforts to determining: (1) HLA-class II alleles specific to Asian populations and which are associated with susceptibility to autoimmune diseases, (2) binding-peptide motifs for these HLA class II molecules, and (3) self-peptides presented by susceptible HLA class II molecules to stimulate autoreactive T cells related to the development of autoimmune diseases in Asians. In this review, our related recent investigations are described and the uniqueness of HLA class II-associated autoimmune diseases in Asians is given emphasis.

Molecular analysis of HLA class I (HLA-A and -B) and HLA class II (HLA-DRB1) genes in Japanese patients with multiple sclerosis (Western type and Asian type)

The types of HLA-A, -B and -DRB1 genes were studied in 146 Japanese patients with multiple sclerosis (MS) using polymerase chain reaction-sequence-specific oligonucleotide probe analysis. Fifty-seven patients who displayed selective clinical involvement of the optic nerve and spinal cord were classified as having Asian type MS. The other 89 patients had disseminated central nervous system involvement and were classified as having Western type MS. The frequency of HLA-B*5101 was increased in both types of MS patients compared with controls. The frequency of HLA-DRB1*1501 was increased in Western type MS and the frequency of HLA-DRB1*0802 was increased in Asian type MS compared to controls. After correction of P values, the association of Western type MS patients with HLA-DRB1*1501 was statistically significant (Pc=0.0003) whereas other HLA alleles showed no significant association. These results suggest that HLA class I (HLA-A and -B) alleles may not contribute to a strong susceptibility to MS in Japanese compared to HLA class II (HLA-DRB1) alleles.

Molecular analyses of HLA class II-associated susceptibility to subtypes of autoimmune diseases unique to Asians

It is well known that individuals positive for particular HLA-class II alleles show high risks for the development of Takayasu arteritis and other diseases caused by immunological disorders such as autoimmune diseases and allergies. HLA class II molecules present antigenic peptides to CD4+ T cells. Their extensive polymorphism affects the structures of peptides bound to HLA class II molecules to create individual differences in immune responses to antigenic peptides. To better understand the mechanisms for association between HLA class II alleles and susceptibility to autoimmune diseases, it is important to identify self-peptides presented by disease-susceptible HLA class II molecules and triggering disease-causative T cells. Many autoimmune diseases are observed in all ethnic groups, whereas the incidences of diseases, clinical manifestations and disease-susceptible HLA class II alleles are different among various ethnic groups for some autoimmune diseases. These phenomena suggest that differences in autoimmune self-peptide(s) in the context of disease-susceptible HLA class II molecules may cause these differences. Therefore, comparisons among disease-susceptible HLA class II alleles, autoimmune self-peptides and clinical manifestations of autoimmune diseases in different ethnic groups would be helpful in determining the pathogenesis of the diseases. In this paper, we describe our recent findings on: (1) the uniqueness of both clinical manifestations and HLA-linked genetic background of Asian-type (optico-spinal form) multiple sclerosis; (2) the structural characteristics of peptides bound to HLA-DQ molecules susceptible to insulin-dependent diabetes mellitus; (3) the identification of a disease-related autoantigenic peptide presented by disease-susceptible HLA-DQ molecules in Asians-specific infant onset myasthenia gravis; and (4) a manipulation of human T cell response by altered peptide ligands, as a possible candidate for new and antigen-specific immuno-suppressive therapy against autoimmune diseases.

HLA-DP-associated susceptibility to the optico-spinal form of multiple sclerosis in the Japanese

We studied polymorphism of the HLA-DP gene in 46 patients with optico-spinal form (Asian type) multiple sclerosis (MS) showing recurrent opticomyelitis and 46 patients with Western type MS with disseminated central nervous system involvement. We previously reported a significant association between an HLA-DRB1 *1501-DRB5*0101 haplotype and susceptibility to Western type but not Asian type MS. In the present study, we found that the frequencies of DPA1 *0202 and DPB1 *0501 alleles were significantly increased in patients with Asian type MS, as compared with findings in 92 healthy control subjects (91.3% vs 65.2%, P(corr)<0.05 and 89.1% vs 63.0%, P(corr)<0.05 respectively), but not in Western type MS. Our data provide further evidence that Asian and Western type MS are distinct regarding the immunogenetic background.

HLA-DR and -DQ associations with multiple sclerosis in Turkey

The DRB, DQA, and DQB subregions of the major histocompatibility complex (MHC) were investigated by polymerase chain reaction and sequence-specific oligonucleotide probe hybridization (PCR/SSO) in 103 multiple sclerosis (MS) patients and 101 healthy controls from Turkey. Significant differences were detected between MS and control populations in the frequencies of DRB1*1501 [29 vs. 14, p = 0.02, odds ratio (OR) = 2.4], DRB1*04 (35 vs. 18, p = 0.01, OR = 2.3), DQB1*0302 (30 vs. 15, p = 0.02, OR = 2.3), DQB1*0602 (27 vs. 10, p = 0.005, OR = 3.2), DQB1*0501 (10 vs. 24, p = 0.01, OR = 0.3), DQA1*0101 (16 vs. 31, p = 0.02, OR = 0.4), and DQA1*0103 (7 vs. 19, p = 0.02, OR = 0.3). These results confirm the proposed positive association of the Dw2 (DRB1*1501 DQA1*0102 DQB1*0602) haplotype with MS in Caucasians in our Turkish population (25 vs. 8, p = 0.003, OR = 3.7). Furthermore, the "putative" haplotype supposed to be more frequent in the MS population of Mediterranean countries, namely DRB1*04 DQA1*03 DQB1*0302, is also associated with MS in Turkey (29 vs. 12, p = 0.006, OR = 2.9). The presence of two different haplotypic associations in MS emphasizes the complexity of the genetic susceptibility to MS in different populations.

Western versus Asian types of multiple sclerosis: immunogenetically and clinically distinct disorders

The polymorphism of HLA-DRB1, -DRB3, and -DRB5 genes as well as magnetic resonance images of the brain and spinal cord were studied in 57 Japanese patients with multiple sclerosis (MS). Twenty-three patients clinically displayed selective involvement of the optic nerve and spinal cord and were classified as having Asian-type MS. The other 34 patients had disseminated central nervous system involvement and were classified as having Western-type MS. Patients with Asian-type MS had fewer brain lesions shown by magnetic resonance imaging, but more gadolinium-enhanced spinal cord lesions than did patients with Western-type MS (47% vs 17%). Furthermore, the DR2-associated DRB1*1501 allele and DRB5*0101 allele were associated with Western-type MS (41.2%), but not with either Asian-type MS (0%) or healthy control subjects (14.2%). Heterogeneity in the immunogenetic background and in the magnetic resonance imaging features between the two subtypes of MS thus suggests the presence of two etiologically distinct diseases in Asians.

Genetic susceptibility to multiple sclerosis

Twin studies have established that susceptibility to multiple sclerosis (MS) is partly genetic. Attempts to identify the relevant genetic loci have involved population-based studies, to detect associations between a genetic marker and MS, and family studies, to detect linkage between a putative marker and MS. Most of this genetic work is driven by the view that MS is an autoimmune disease. Thus, the focus has been mainly on genes known to be important in the immune response: human leukocyte antigen (HLA) genes, T-cell receptor genes, and immunoglobulin genes. To date, only the particular HLA-DR2 haplotype that is common in Caucasians can be concluded to be important in MS susceptibility in most populations. Studies of other genetic loci have been few, the data obtained often have been conflicting or controversial, and further studies are needed to clarify the biological significance of these loci in MS. Recommendations for further studies are provided in order to overcome some of the problems that have plagued earlier work in MS such as nonreproducibility of results.

Multiple sclerosis: multiple etiologies, multiple genes?

Multiple sclerosis is a chronic inflammatory disease characterized by multifocal damage of the central nervous system myelin. Both humoral and cell-mediated immune abnormalities have been observed in patients with multiple sclerosis, but their relation to the demyelination process is not understood. The etiology of the disease is still unknown; however, evidence exists for an interplay between environmental and genetic factors. Several genes are involved in determining the disease susceptibility, at least one of them encoded within human leukocyte antigen gene complex. Other genomic regions coding for components of the immune system or myelin have also been suggested. Clinical, immunological and genetic data suggest that multiple sclerosis may turn out to be a heterogeneous disease. Therefore, molecular genetic dissection of this complex disease should provide important clues to its pathogenesis as well as unravel metabolic pathways for potential therapeutic or preventive strategies. This review will give an overview of recent progress and future challenges in identifying susceptibility genes for multiple sclerosis.

Human leukocyte antigen studies in multiple sclerosis

Multiple sclerosis (MS) has been associated with HLA-DR2 for more than 20 years, and a large number of studies have addressed the relation between MS and the HLA class II genes, which are our major immune-response genes. This has produced a complex and confusing picture that is difficult to interpret. With the advent of reliable and comprehensive DNA-based typing techniques, it is now possible to extract a coherent pattern from this mass of data. The associated haplotype has been specified to HLA-Dw2 in cellular typing nomenclature, which equals DR15,DQ6 by serology, and DRB1*1501,DQA1*0102,DQB1*0602 in sequence-based terminology. This haplotype is increased among groups of MS patients worldwide, although most strongly in North and West Europeans, and it is the only haplotype with a clear importance in MS. Attempts to map this association within the haplotype have not been successful.