DQB1*0602 confers genetic susceptibility to multiple sclerosis in Afro-Brazilians

Clinical and Genetic Analysis in Pediatric Patients with Multiple Sclerosis and Related Conditions: Focus on DR Genes of the Major Histocompatibility Complex

Introduction:

There are several diseases recognized as variants of MS: post-infectious acute disseminated encephalitis, multiple sclerosis (MS), Rasmussen leukoencephalitis and Schilder's leukoencephalitis and related, but separate neuroimmune condition – Neuromyelitis Devic’s. In Kazakhstan diagnosis of such diseases was rare and immune modified treatment was only admitted after the age of 18. Clinical and immunogenetic study of MS spectrum diseases in Kazakhstan would allow to justify early targeted treatment.

Objective:

The aim of the study was to investigate genes of the main complex of human histocompatibility (MHC) associated with diseases of MS spectrum in Kazakhstani population.

Methods:

Complex clinical, neuroimaging and immunogenetic studies were performed in 34 children (24 girls, 10 boys) aged 4 to 18 years. 21 children were diagnosed with MS (11 Kazakh origin and 10 – Russian; 4 boys, 17 girls), 7 with leucoencephalitis (all Kazakh, 5 boys, 2 girls) and 6 with Devic neuromyelitis optica (all Kazakh, 1 boy, 5 girls). Genotyping of HLA DRB1, DQA1, DQB1 genes was performed for all patients.

Results:

MS group was characterized by classical relapsing-remitting MS. Predominant haplotype as a linkage complex was DRB1*15:01~DQA1*01:02~DQB1*06:02 in 20 (47.6%) of 42 DR-alleles, in 16 (76.2%) patients. MS relative risk (RR) was 13,36 for ethnic Kazakhs and RR=5,55 in Russians.

Leukoencephalitis had 7 children, with 28.6% mortality rate. The haplotype DRB1*15:01~DQA1*01:02~DQB1*06:02 as a linkage complex was detected 3 patients (4 alleles), RR=5,88.

Devic’s neuromyelitis optica (NMO) clinical course was characterized by fast and prolonged progression. There was predominance of DRB1*14 allele with RR=3,38.

Conclusion:

Summarizing, in the Kazakh population the haplotype DRB1*15:01∼DQA1*01:02∼DQB1*06:02 as a linkage complex was associated with prediction to MS and leukoencephalitis, but not to Devic’s NMO. Our study highlights the importance of awareness of MS and related disorders diagnosis which allows to implement early admission of disease-modified treatment in pediatric MS in Kazakhstan.

Class II HLA (DRB1, & DQB1) alleles and IL7R (rs6897932) variants and the risk for Multiple Sclerosis in Kerala, India

BACKGROUND

Different human leukocyte antigen (HLA) variants are known to modulate the risk of multiple sclerosis. The main objective of this study was to identify HLA-DRB1 and HLA-DQB1 alleles and Non -HLA gene IL7R (rs6897932) variants associated with MS.

METHODS

Patients attending the MS clinic, diagnosed with Multiple Sclerosis as per Mc Donald diagnostic criteria were the subjects in the study. The association of the highly polymorphic HLA-DRB1 and HLA-DQB1 loci was determined by high resolution tissue typing and the genotyping of the IL7R (rs6897932) variants was performed by Sanger sequencing in MS patients (n = 81) and healthy individuals (n = 82).

RESULTS

HLA-DRB1*15:01/15:02 alleles (OR = 3.65; p< 0.0001) and HLA-DQB1*06:02 (OR=4.19, p<0.0001) were found to be positively associated while HLA-DRB1*14:04:01 (OR = 0.21; p = 0.0009) was found to be negatively associated with MS. The most significant predisposing HLA haplotype was found to be DRB1*15:01-DQB1*06:02 (OR=5.69, p<0.0001). Univariate analysis of IL7R SNP (rs6897932) showed no significant association with MS in our population whereas analysis of HLA-DRB1 alleles and IL7R (rs6897932) genotypes showed significant association between the HLA-DRB1*15:01/15:02 and the IL7R (rs6897932) CC genotype (OR = 3.58, p = 0.0002).

CONCLUSION

HLA-DRB1*15:01, 15:02 and DQB1*06:02 are the predisposing alleles while HLA-DRB1*14:04 is the protective allele for MS in our population.

Association of HLA-DR2-Related Haplotype (HLA-DRB5*01-DRB1*1501-DQB1*0602) in Patients with Multiple Sclerosis in Khuzestan Province

OBJECTIVE

Multiple sclerosis (MS) is a partially heritable autoimmune disease. HLA-DR2 is the largest identified genetic risk factor for MS. The largest identified genetic risk factor is haplotype from the MHC class II HLA-DR2, which increases the disease risk. The HLA-DR2 distribution in MS patients has been confirmed, but contradictory outcomes have been found. Moreover, the HLA-DR2 effect on ethnicity and gender is unclear. There are no data regarding the HLA-DR2 (HLA-DRB1*1501-DRB5*01-DQB1*0602) association with MS in Khuzestan Province, Iran. This study aimed to investigate the association of HLA-DR2 with MS regarding both sex and ethnicity in this province.

MATERIALS & METHODS

A total of 399 individuals were recruited. HLA typing was conducted using the polymerase chain reaction amplification with sequence-specific primers technology. The HLA-DR2 association with MS was analyzed, and also its probable association with gender, ethnicity, the expanded disability status scale (EDSS), and MS clinical course was examined using the Chi-square test.

RESULTS

HLA-DRB5*01 - -DQB1*0602 - as the most common HLA haplotype was found in both patient and control groups. In contrast, the DRB5*01 + -DRB1*1501 + -DQB1*0602 - frequency was very low in the groups. It was observed that haplotypes had no association with MS susceptibility. Most of the haplotypes showed no association with ethnicity, sex, EDSS, and MS course except for the HLA-DRB5*01 + -DRB1*1501 + -DQB1*0602 - haplotype that was positively associated with EDSS steps 5 to 10 (p=0.014) and non-RRMS (p=0.023).

CONCLUSION

There was no association between HLA-DR2 and MS susceptibility. However, the higher HLA-DRB5*01 + -DRB1*1501 + -DQB1*0602 - frequency may play a role in MS development. Also, HLA-DR2 did not increase significantly concerning clinical course, ethnicity, sex, and EDSS. This study further supports the importance of replication studies as susceptible loci that might differ in various ethnicities. Therefore, it is concluded that the association between HLA-DR2 and MS is more allelic than haplotypic in Khuzestan.

Endosomal Toll-Like Receptors Mediate Enhancement of Interleukin-17A Production Triggered by Epstein-Barr Virus DNA in Mice

We previously demonstrated that Epstein-Barr virus (EBV) DNA increases the production of the proinflammatory cytokine interleukin-17A (IL-17A) in mice. This property may contribute to the established association between EBV and autoimmune diseases. The objective of the present study was to elucidate mechanisms through which EBV DNA modulates IL-17A levels in mice. To determine whether endosomal Toll-like receptors (TLRs) played a role in this pathway, the expression of TLR3, -7, or -9 was assessed by real-time reverse transcription-PCR in mouse spleens after injection of EBV DNA. Moreover, specific inhibitors were used for these TLRs in mouse peripheral blood mononuclear cells (PBMCs) cultured with EBV DNA and in mice injected with this viral DNA; IL-17A levels were then assessed using an enzyme-linked immunosorbent assay. The expression of the endosomal receptors TLR3, -7, and -9 was increased in mice injected with EBV DNA. When mouse immune cells were cultured with EBV DNA and a TLR3, -7, or -9 inhibitor or when mice were injected with the viral DNA along with either of these inhibitors, a significant decrease in IL-17A levels was detected. Therefore, endosomal TLRs are involved in the EBV DNA-mediated triggering of IL-17A production in mice. Targeting these receptors in EBV-positive subjects with autoimmunity may be useful pending investigations assessing whether they play a similar role in humans.IMPORTANCE Epstein-Barr virus is a pathogen that causes persistent infection with potential consistent viral DNA shedding. The enhancement of production of proinflammatory cytokines by viral DNA itself may contribute to autoimmune disease development or exacerbation. In this project, we identified that endosomal Toll-like receptors are involved in triggering proinflammatory mediators in response to viral DNA. Pathways and receptors involved may serve as future therapeutic targets for autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, and systemic lupus erythematosus.

Environmental factors influencing multiple sclerosis in Latin America

It is generally accepted that autoimmune diseases like multiple sclerosis (MS) arise from complex interactions between genetic susceptibility and environmental factors. Genetic variants confer predisposition to develop MS, but cannot be therapeutically modified. On the other hand, several studies have shown that different lifestyle and environmental factors influence disease development, as well as activity levels and progression. Unlike genetic risk factors, these can be modified, with potential for prevention, particularly in high-risk populations. Most studies identifying particular lifestyle and environmental factors have been carried out in Caucasian patients with MS. Little or no data is available on the behavior of these factors in Latin American populations. Ethnic and geographic differences between Latin America and other world regions suggest potential regional variations in MS, at least with respect to some of these factors. Furthermore, particular environmental characteristics observed more frequently in Latin America could explain regional differences in MS prevalence. Site-specific studies exploring influences of local environmental factors are warranted.

The immunogenetics of multiple sclerosis. The frequency of HLA-alleles class 1 and 2 is lower in Southern Brazil than in the European population

ABSTRACT Objective To study the HLA of class 1and 2 in a multiple sclerosis (MS) population to verify the susceptibility for the disease in the Southern Brazil. Methods We analyzed patients with MS and controls, by direct sequencing of the genes related to HLA DRB1, DQB1, DPB1, A, B and C alleles with high resolution techniques. Results We found a lower frequency of all HLA alleles class 1 and 2 in MS and controls comparing to the European population. Several alleles had statistical correlation, but after Bonferroni correction, the only allele with significance was the HLA-DQB1*02:03, which has a positive association with MS. Conclusions Our data have different frequency of HLA-alleles than the previous published papers in the Southeast Brazil and European population, possible due to several ethnic backgrounds.

The CIITA genetic polymorphism rs4774*C in combination with the HLA-DRB1*15:01 allele as a putative susceptibility factor to multiple sclerosis in Brazilian females

The objective of this study was to investigate the association between the HLA alleles at the DQA1, DQB1 and DRB1 loci, the CIITA genetic polymorphisms -168A/G and +1614G/C, and susceptibility to multiple sclerosis (MS) in a sample from Rio de Janeiro State, Brazil. Furthermore, we wished to determine whether any of these associations might be more significant in women compared with men. DNA samples from 52 relapsing-remitting MS (RRMS) patients and 126 healthy controls matched for sex and age were analyzed. We identified a significant HLA-DRB1*15:01-MS association that was female-specific (Odds Ratio (OR) = 4.78; p = 0.001). Furthermore, we observed that the +1614G/C mutation in combination with the HLA-DRB1*15:01 allele increased susceptibility to MS in females (OR = 4.55; p = 0.01). Together, these findings highlight the polygenic nature of MS.

HLA associations in South Asian multiple sclerosis

Background:

Previous efforts to identify Human Leukocyte Antigen (HLA) gene associations with multiple sclerosis (MS) in the South Asian population have been underpowered.

Aim:

To identify the primary HLA class II alleles associated with MS in Indians.

Methods:

We typed HLA-DRB1, -DQA1 and -DQB1 in 419 patients and 451 unrelated controls by polymerase chain reaction using sequence specific oligonucleotide probes (PCR-SSOP).

Results:

At the gene level DRB1 showed significant evidence of association ( p=0.0000012), DQA1 showed only marginal evidence of association ( p=0.04) and there was no evidence for association at DQB1 ( p=0.26). At the DRB1 locus association is confirmed with the *15:01 ( p=0.00002) and the *03 ( p=0.00005) alleles.

Conclusion:

Our study confirms that the risk effects attributable to the HLA- DRB1*15:01and DRB1*03 alleles seen in Europeans are also seen in Indians. The absence of any evidence of association with DQB1 alleles reflects the lower linkage disequilibrium between DQB1 alleles and DRB1 risk alleles present in this population, and illustrates the potential value of fine mapping signals of association in different ethnic groups.

The Role of HLA in MS Susceptibility and Phenotype

One of the most consistent findings in multiple sclerosis (MS) is that development of MS is linked with carriage of the class II human leucocyte antigen (HLA) molecule HLA-DRB1*15:01; around 60 % of Caucasian MS patients carry this allele compared to 25-30 % of ethnically matched healthy individuals. However, other HLA molecules have also been linked to the development of MS. In this chapter, the association between different HLA types and susceptibility to MS will be reviewed, and other linkages between the carriage of specific HLA molecules and clinical and experimental findings in MS will be considered.

The genetics of multiple sclerosis: an up-to-date review

Multiple sclerosis (MS) is a prevalent inflammatory disease of the central nervous system that often leads to disability in young adults. Treatment options are limited and often only partly effective. The disease is likely caused by a complex interaction between multiple genes and environmental factors, leading to inflammatory-mediated central nervous system deterioration. A series of genomic studies have confirmed a central role for the immune system in the development of MS, including genetic association studies that have now dramatically expanded the roster of MS susceptibility genes beyond the longstanding human leukocyte antigen (HLA) association in MS first identified nearly 40 years ago. Advances in technology together with novel models for collaboration across research groups have enabled the discovery of more than 50 non-HLA genetic risk factors associated with MS. However, with a large proportion of the disease heritability still unaccounted for, current studies are now geared towards identification of causal alleles, associated pathways, epigenetic mechanisms, and gene-environment interactions. This article reviews recent efforts in addressing the genetics of MS and the challenges posed by an ever increasing amount of analyzable data, which is spearheading development of novel statistical methods necessary to cope with such complexity.

The genetics of multiple sclerosis: an up-to-date review

Multiple sclerosis (MS) is a prevalent inflammatory disease of the central nervous system that often leads to disability in young adults. Treatment options are limited and often only partly effective. The disease is likely caused by a complex interaction between multiple genes and environmental factors, leading to inflammatory-mediated central nervous system deterioration. A series of genomic studies have confirmed a central role for the immune system in the development of MS, including genetic association studies that have now dramatically expanded the roster of MS susceptibility genes beyond the longstanding human leukocyte antigen (HLA) association in MS first identified nearly 40 years ago. Advances in technology together with novel models for collaboration across research groups have enabled the discovery of more than 50 non-HLA genetic risk factors associated with MS. However, with a large proportion of the disease heritability still unaccounted for, current studies are now geared towards identification of causal alleles, associated pathways, epigenetic mechanisms, and gene-environment interactions. This article reviews recent efforts in addressing the genetics of MS and the challenges posed by an ever increasing amount of analyzable data, which is spearheading development of novel statistical methods necessary to cope with such complexity.

The influence of the HLA-DRB1 and HLA-DQB1 allele heterogeneity on disease risk and severity in Iranian patients with multiple sclerosis

Multiple sclerosis (MS) is a common autoimmune disorder of the central nervous system. Recent studies have shown that the HLA-DRB1 and DQB1 alleles are associated with MS susceptibility and severity. However, this is controversial in different population studies. In the present study, the roles of HLA-DRB1 and DQB1 alleles and the amino acids were investigated on disease risk and severity in 120 Iranian patients with MS and 120 controls. Our findings indicate that the DRB1*1501 allele (OR = 3.203 P = 0.001), the DRB1*1501-DQB1*0602 haplotype (OR = 7.792 P = 0.003) and the DRB1*1501/0701- genotype (OR = 3.320 P = 0.006) and amino acid Leu26 (OR = 1.645 P = 0.005) and Phe9 (OR = 1.893 P = 0.009) on the DQβ1 chain are significantly associated with MS susceptibility. DRB1*1001 was the only allele that had a protective effect against MS (P = 0.0004). We also found that the DQB1*0303 allele was significantly associated with disease severity (mean Multiple Sclerosis Severity Score difference = 1.979, P = 0.002). However, protective effect of the DRB1*1001 against MS and also association of DQB1*0303 allele with MS severity need to be confirmed by larger sample size.

Multiple sclerosis risk variant HLA-DRB1*1501 associates with high expression of DRB1 gene in different human populations

The human leukocyte antigen (HLA) DRB1*1501 has been consistently associated with multiple sclerosis (MS) in nearly all populations tested. This points to a specific antigen presentation as the pathogenic mechanism though this does not fully explain the disease association. The identification of expression quantitative trait loci (eQTL) for genes in the HLA locus poses the question of the role of gene expression in MS susceptibility. We analyzed the eQTLs in the HLA region with respect to MS-associated HLA-variants obtained from genome-wide association studies (GWAS). We found that the Tag of DRB1*1501, rs3135388 A allele, correlated with high expression of DRB1, DRB5 and DQB1 genes in a Caucasian population. In quantitative terms, the MS-risk AA genotype carriers of rs3135388 were associated with 15.7-, 5.2- and 8.3-fold higher expression of DQB1, DRB5 and DRB1, respectively, than the non-risk GG carriers. The haplotype analysis of expression-associated variants in a Spanish MS cohort revealed that high expression of DRB1 and DQB1 alone did not contribute to the disease. However, in Caucasian, Asian and African American populations, the DRB1*1501 allele was always highly expressed. In other immune related diseases such as type 1 diabetes, inflammatory bowel disease, ulcerative colitis, asthma and IgA deficiency, the best GWAS-associated HLA SNPs were also eQTLs for different HLA Class II genes. Our data suggest that the DR/DQ expression levels, together with specific structural properties of alleles, seem to be the causal effect in MS and in other immunopathologies rather than specific antigen presentation alone.

HLA associations with multiple sclerosis in Greece

BACKGROUND

Multiple sclerosis (MS) is a demyelinating inflammatory disease of the central nervous system originated by a complex interplay of environmental and genetic factors. The association of MS with the human leukocyte antigen (HLA) class II alleles was investigated in MS patients in northwest Greece, in the geographical region of Epirus.

OBJECTIVE

Our aim was to estimate the prevalence of the HLA-DRB1*1501, HLA-DQB1*0602 and HLA-DQA1*0102 alleles, consisting the most common susceptibility haplotype in North European and North American Caucasians.

METHODS

We studied 126 MS patients and 93 age and sex matched healthy controls. HLA typing was performed by a polymerase chain reaction (PCR) amplification with sequence-specific primers (PCR-SSP) method.

RESULTS

We found that HLA-DRB1*1501, HLA-DQB1*0602 and HLA-DQA1*0102 alleles were significantly more frequent among patients (34% versus 11%, p=0.00015; 69% versus 51%, p=0.01; 76% versus 55%, p=0.002, respectively). HLA-DRB1*1501, HLA-DQB1*0602, HLA-DQA1*0102 haplotype was significantly more common among patients (p=0.00067). HLA-DRB1*1501 and HLA-DQB1*0602 alleles were more frequently detected in patients with initial symptoms from the brainstem or the cerebellum (p=0.024). No significant correlation was observed among these alleles with sex, disease clinical course, or age at onset.

CONCLUSION

This is the first study to investigate genetic susceptibility to MS in Greece. Our results are in line with previous reports in North European and North American patients.

Influence of histocompatibility genes on disease susceptibility and treatment response in patients with relapsing-remitting multiple sclerosis treated with interferon β-1a

Multiple sclerosis (MS) is the most common, non-traumatic cause of neurological disability in young adults. The aim of this study was to investigate the influence of HLA class II alleles DRB1* and DQB1* on susceptibility to relapsing-remitting (RR) MS and response to interferon (IFN) β-1a treatment. A prospective observational study was conducted. Seventeen patients with clinically definite RRMS, attending a tertiary referral center for multiple sclerosis in Israel and receiving treatment with subcutaneous IFN β-1a, 22 mcg three times weekly were recruited between December 1998 and February 2000 and observed for 12 months. HLA genotyping was performed and clinical characteristics (relapse rate and disability progression) assessed at baseline and after 12 months. HLA data for a healthy control group were also used for comparison. HLA and the success of treatment with IFN β-1a in this group of RRMS patients were assessed. The frequency of DRB1*03 was six times higher in patients treated with IFN β-1a than in the healthy control group (n=100): 29% (5/17) versus 5% (5/100), respectively. Additionally, DQB1*03 and DQB1*02 were present in 82% (14/17) and 41% (7/17) of RRMS patients, but in only 33% (33/100) and 18% (18/100) of control patients, respectively. A better response to IFN β-1a treatment was seen in patients carrying these alleles than in patients without these alleles. Our results indicated that DRB1*03, DQB1*03 and DQB1*02 alleles may contribute to MS susceptibility and IFN β-1a responsiveness, and warrant further verification in a larger population.

Acute disseminated encephalomyelitis: clinical features, HLA DRB1*1501, HLA DRB1*1503, HLA DQA1*0102, HLA DQB1*0602, and HLA DPA1*0301 allelic association study

We evaluated the frequency, demographic, clinical, disability evolution and genetic association of HLA DRB1*1501, DRB1*1503, DQA1*0102, DQB1*0602 and DPA1*0301 alleles in patients diagnosed as acute disseminated encephalomyelitis (ADEM) among a population of CNS demyelinating diseases. Fifteen patients (8.4%) of our series were diagnosed as ADEM. The mean age onset was 35.23 years (range 12 to 77), 53.3% were male and follow-up range was 8.5 to 16 years. Two cases (13.3%) had a preceding infection before neurological symptoms, one presented a parainfectious demyelinating, and one case had been submitted to hepatitis B vaccination four weeks before the clinical onset. The EDSS range was 3.0 to 9.5. Eight patients (53.3%) presented MRI with multiple large lesions. CSF was normal in 73.3%. The severe disability observed at EDSS onset improved in 86.66% patients. The genetic susceptibility for ADEM was significantly associated with the HLA DQB1*0602, DRB1*1501 and DRB1*1503 alleles (<0.05) in monophasic ADEM.

Association between protective and deleterious HLA alleles with multiple sclerosis in Central East Sardinia

The human leukocyte antigen (HLA) complex on chromosome 6p21 has been unambiguously associated with multiple sclerosis (MS). The complex features of the HLA region, especially its high genic content, extreme polymorphism, and extensive linkage disequilibrium, has prevented to resolve the nature of HLA association in MS. We performed a family based association study on the isolated population of the Nuoro province (Sardinia) to clarify the role of HLA genes in MS. The main stage of our study involved an analysis of the ancestral haplotypes A2Cw7B58DR2DQ1 and A30Cw5B18DR3DQ2. On the basis of a multiplicative model, the effect of the first haplotype is protective with an odds ratio (OR) = 0.27 (95% confidence interval CI 0.13-0.57), while that of the second is deleterious, OR 1.78 (95% CI 1.26-2.50). We found both class I (A, Cw, B) and class II (DR, DQ) loci to have an effect on MS susceptibility, but we saw that they act independently from each other. We also performed an exploratory analysis on a set of 796 SNPs in the same HLA region. Our study supports the claim that Class I and Class II loci act independently on MS susceptibility and this has a biological explanation. Also, the analysis of SNPs suggests that there are other HLA genes involved in MS, but replication is needed. This opens up new perspective on the study of MS.

Multiple sclerosis and the major histocompatibility complex

PURPOSE OF REVIEW

Multiple sclerosis (MS) is the most common neurological disease affecting young adults. The cause is unknown, but detailed epidemiological and genetic studies have shown a clear inherited component. We review here some of the recent findings of MS genetics with a particular focus on genes of the major histocompatibility complex (MHC).

RECENT FINDINGS

Recent studies add further complexity to the role of the MHC in MS. Reported MHC associations are complex, involving haplotypes rather than single alleles and may involve epigenetic mechanisms and other modulators of gene expression. MHC class II haplotypes display a hierarchy of risks, including protective effects and epistatic interactions, which together dwarf any non-MHC genetic effect. Genes in the MHC region have been shown to influence disease severity, display parent-of-origin effects and interact with a major environmental candidate for MS, vitamin D.

SUMMARY

The MHC class II association with MS is not as straightforward as previously thought. A complete understanding of the epistatic interactions and epigenetic features of this region will be important to understand disease pathogenesis and likely aid the discovery of new therapeutics.

Epistasis among HLA-DRB1, HLA-DQA1, and HLA-DQB1 loci determines multiple sclerosis susceptibility

Multiple sclerosis (MS), a common central nervous system inflammatory disease, has a major heritable component. Susceptibility is associated with the MHC class II region, especially HLA-DRB5*0101-HLA-DRB1*1501-HLA-DQA1*0102-HLA-DQB1*0602 haplotypes(hereafter DR2), which dominate genetic contribution to MS risk. Marked linkage disequilibrium (LD) among these loci makes identification of a specific locus difficult. The once-leading candidate, HLA-DRB1*15, localizes to risk, neutral, and protective haplotypes. HLA-DRB1*15 and HLA-DQB1*0602, nearly always located together on a small ancestral chromosome segment, are strongly MS-associated. One intervening allele on this haplotype, viz. HLA-DQA1*0102, shows no primary MS association. Two Canadian cohorts (n = 830 and n = 438 trios) genotyped for HLA-DRB1, HLA-DQA1 and HLA-DQB1 alleles were tested for association using TDT. To evaluate epistasis involving HLA-DRB1*15, transmissions from HLA-DRB1*15-negative parents were stratified by the presence/absence of HLA-DRB1*15 in affected offspring. All 3 alleles contribute to MS susceptibility through novel epistatic interactions. HLA-DQA1*0102 increased disease risk when combined with HLA-DRB1*1501 in trans, thereby unambiguously implicating HLA-DQ in MS susceptibility. Three-locus haplotypes demonstrated that HLA-DRB1*1501 and HLA-DQB1*0602 each influence risk. Transmissions of rare morcellated DR2 haplotypes showed no interaction with HLA-DQA1*0102. Incomplete haplotypes bearing only HLA-DRB1*1501 or HLA-DQB1*0602 did not predispose to MS. Balanced reciprocal transmission distortion can mask epistatic allelic association. These findings implicate epistasis among HLA class II alleles in human immune responses generally, provide partial explanation for intense linkage disequilibrium in the MHC, have relevance to animal models, and demonstrate key roles for DR2-specific interactions in MS susceptibility. MHC disease associations may be more generally haplotypic or diplotypic.

Analysis of HLA DR2&DQ6 (DRB1*1501, DQA1*0102, DQB1*0602) haplotypes in Iranian patients with multiple sclerosis

Multiple sclerosis (MS) is prototype of inflammatory demyelinating disease of the central nervous system .The etiology of MS remains unclear, but according to current data the disease develops in genetically susceptible individuals and may require additional environmental triggers. The human leukocyte antigen (HLA) class II alleles (DRB1*1501, DQA1*0102, DQB1*0602) may have the strongest genetic effect in MS. In this study, the role of these alleles were investigated in 183 Iranian patients with multiple sclerosis and compared with 100 healthy individuals. HLA typing for DRB1*1501, DQA1*0102, DQB1*0602 was performed by polymerase chain reaction (PCR) amplification with sequence-specific primers (PCR-SSP) method. The results show that, HLA DR B1*1501 was significantly more frequent among MS patients (46% vs. 20%, PV = 0.0006) but DQA1*0102 haplotype was negatively associated with MS (30% vs. 50%, PV = 0.0049) and no significant association was found with DQB1*0602 and MS patients in comparison with control group (24% and 30%, PV = 0.43). No significant correlation was observed among these alleles with sex, type of disease; initial symptoms, expanded disability status scale (EDSS), as well as age at onset and familial MS. This study therefore indicates that there is no association of above HLA haplotypes with clinical presentation, disease duration, and disability in Iranian patients with MS which is in line with other previous studies in different ethnic groups.

The immunogenetics of multiple sclerosis

The discoveries in the 1970s of strong associations between various diseases and certain human leukocyte antigen (HLA) factors were a revolution within genetic epidemiology in the last century by demonstrating for the first time how genetic markers can help unravel the genetics of disorders with complex genetic backgrounds. HLA controls immune response genes and HLA associations indicate the involvement of autoimmunity. Multiple sclerosis (MS) was one of the first conditions proven to be HLA associated involving primarily HLA class II factors. We review how HLA studies give fundamental information on the genetics of the susceptibility to MS, on the importance of linkage disequilibrium in association studies, and on the pathogenesis of MS. The HLA-DRB1*1501 molecule may explain about 50% of MS cases and its role in the pathogenesis is supported by studies of transgenic mice. Studies of polymorphic non-HLA genetic markers are discussed based on linkage studies and candidate gene approaches including complete genome scans. No other markers have so far rivaled the importance of HLA in the genetic susceptibility to MS. Recently, large international collaborations provided strong evidence for the involvement of polymorphism of two cytokine receptor genes in the pathogenesis of MS: the interleukin 7 receptor alpha chain gene (IL7RA) on chromosome 5p13 and the interleukin 2 receptor alpha chain gene (IL2RA (=CD25)) on chromosome 10p15. It is estimated that the C allele of a single nucleotide polymorphism, rs6897932, within the alternative spliced exon 6 of IL7RA is involved in about 30% of MS cases.

The immunological basis for treatment of multiple sclerosis

During the last few years, the concept of multiple sclerosis (MS) as a pure inflammatory disease mediated by myelin reactive T cells has been challenged. Neither the specificity nor the mechanisms triggering or perpetuating the immune response are understood. Genetic studies have so far not identified therapeutic targets outside the HLA complex, but epidemiological and immunological studies have suggested putative pathogenetic factors which may be important in therapy or prevention, including the Epstein-Barr virus and vitamin D. Advances in the treatment of MS have been reached by manipulating the immune response where the pathogenesis of MS intersects experimental autoimmune encephalomyelitis, most recently by blocking T-cell migration through the blood-brain barrier. Antigen-specific approaches are effective in experimental models driven by a focused immune response against defined autoantigens, but MS may not fit into this concept. Novel candidate autoantigens which are not constitutively expressed in the brain, such as protein alpha-B crystallin or IgG V-region idiotopes, as well as evidence of pathogenetic heterogeneity and complexity, suggest that treating MS by tolerizing the immune system against an universal MS antigen may be a fata morgana. Further characterization of MS subtypes may lead to individualized treatment. However, shared immunological features, such as intrathecal production of oligoclonal IgG, suggest that potential therapeutic targets may be shared by most MS patients.

Low frequency of the disease-associated DRB1*15-DQB1*06 haplotype may contribute to the low prevalence of multiple sclerosis in Sami

This study confirms a low frequency of multiple sclerosis (MS) among Sami. Only 12 Sami with a diagnosis of MS were identified in the Norwegian Sami population, which represents a significantly lower prevalence of MS in Sami (30/10(5)) compared with other Norwegians (73-164/10(5)). The clinical characteristics as well as the results of human leukocyte antigen (HLA)-DRB1 and -DQB1 typing of the Sami MS patients are reported, showing that three (27%) of the Sami MS patients carried the MS-associated HLA-DRB1*15-DQB1*06 haplotype. Interestingly, the DRB1*15-DQB1*06 haplotype had a significantly reduced frequency among Sami controls (0.086) compared with non-Sami Norwegian controls (0.163) (P(corrected) = 0.015). The low frequency of the disease-associated DRB1*15-DQB1*06 haplotype in the Sami population may contribute to the low prevalence of MS in Sami, in addition to other yet unidentified genetic and environmental factors.

Variation of the myelin oligodendrocyte glycoprotein gene is not primarily associated with multiple sclerosis in the Sardinian population

BACKGROUND

Multiple sclerosis (MS) is consistently associated with particular HLA-DRB1-DQB1 haplotypes. However, existing evidence suggests that variation at these loci does not entirely explain association of the HLA region with the disease. The MOG locus is a prime positional and functional candidate for such additional predisposing effects but the analysis is complicated by the strong, albeit labyrinthine pattern of linkage disequilibrium in the region. Here we have assessed the association of MOG variation with MS in the Sardinian population to see if it represents an independent contributor to MS predisposition.

RESULTS

After re-sequencing the MOG gene in 21 healthy parents of MS patients we detected 134 variants, 33 of which were novel. A set of 40 informative SNPs was then selected and assessed for disease association together with 1 intragenic microsatellite in an initial data set of 239 MS families. This microsatellite and 11 SNPs were found to be positively associated with MS, using the transmission disequilibrium test, and were followed up in an additional 158 families (total families analysed = 397). While in these 397 families, 8 markers showed significant association with MS, through conditional tests we determined that these MOG variants were not associated with MS independently of the main DRB1-DQB1 disease associations.

CONCLUSION

These results indicate that variation within the MOG gene is not an important independent determinant of MS-inherited risk in the Sardinian population.

HLA-DR15 haplotype and multiple sclerosis: a HuGE review

An association between multiple sclerosis (MS) and the human leukocyte antigen (HLA) complex, a dense cluster of genes on the short arm of chromosome 6, was first noted over 30 years ago. In Caucasian populations of Northern European descent, the DR15 haplotype (DRB1*1501-DQA1*0102-DQB1*0602) has been hypothesized to be the primary HLA genetic susceptibility factor for MS. However, studies of other populations have produced varying results. Thus, the authors reviewed the literature for articles on the association between the DR15 haplotype and MS. They identified 72 papers meeting the inclusion criteria: human genetic studies written in English that were published between 1993 and 2004 and that reported allele frequencies for HLA-DRB1*1501, HLA-DQA1*0102, or HLA-DQB1*0602 or the frequency of the DRB1*1501-DQA1*0102-DQB1*0602 haplotype. Most of the studies identified used a case-control design (n = 60), while the remainder used a family-based design (n = 22). In most of these papers, investigators reported a higher frequency of the DR15 haplotype and/or its component alleles among MS cases than among controls. However, the authors' confidence in these results is tempered by factors related to study design that may have biased the outcomes.

Ethnicity-dependent association of HLA DRB1-DQA1-DQB1 alleles in Brazilian multiple sclerosis patients

OBJECTIVE

The present study focused on human leukocyte antigen (HLA) DQB1, DQA1 and DRB1 allelic variation according to ethnicity and analyzed whether susceptibility to multiple sclerosis (MS) depends on population characteristics.

METHODS

Eighty-eight healthy African-Brazilians and 92 healthy white Brazilians living in Rio de Janeiro City were selected and the HLA phenotype between the two ethnic groups was compared with 44 MS patients of African descent and 40 patients of European descent. HLA class II genes were performed using polymerase chain reaction (PCR) and PCR-sequence-specific primer amplification.

RESULTS

DQA1*0201-0301 alleles were associated with the white Brazilian population (P < 0.001). The DRB*1501 allele was present in White Brazilians (P=0.003), and DRB1*03-1503 in African-Brazilians. The DRB1*1501 allele confers an ethnicity-dependent MS susceptibility in White patients and the DQB1*0602 allele confers genetic susceptibility regardless of ethnicity.

CONCLUSION

Heterogeneous phenotypes occur in both Brazilian ethnic groups. Taking into account that the response to immunomodulator drugs for MS treatment changes according to the DRB1*1501 allele and African-American MS patients presented poor response to the interferons, phenotype heterogeneity of HLA loci found in this study could influence therapeutic decisions in the Brazilian MS population.

Study of polymorphisms in the interleukin-4 and IL-4 receptor genes in a population of Brazilian patients with multiple sclerosis

This study aimed to investigate in a population of Brazilian patients with multiple sclerosis (MS) single-nucleotide polymorphisms (SNP) in the promoter region of IL4 (*33C-T) and receptor IL4R (*Q551R A-G) genes proposed to interfere with disease progression. No significant differences were observed in either of the SNPs investigated between healthy controls (n=135) and MS patients (n=129). However, the IL4+33 TT genotype was significantly (p=0.039) higher in African descendants MS (AF-MS= 9.09%) than in Caucasian MS (CA-MS= 1.35%). It was also observed a significant (p=0.016) increase for the IL4R* Q551R CC genotype in AF-MS compared to those of Caucasian ethnicity (AF-MS= 21.62%; CA-MS= 4.35%). These results suggest that IL4+33 and IL4R*Q551 polymorphisms may have a disease-promoting role of TH2 mediators in African MS descendants. Additionally neither IL4 nor IL4R genes are susceptibility factors for Brazilian MS but may be able to modify ethnicity-dependent disease risk and penetrance of susceptibility factors.

TNF-alpha, TNF-beta and IL-4 gene polymorphisms in Iranian patients with multiple sclerosis

OBJECTIVES

To investigate the association between tumor necrosis factor-alpha (TNF-alpha) G-308A, tumor necrosis factor-beta (TNF-beta) G+252A and interleukin-4 (IL-4) C-590T polymorphisms and susceptibility to multiple sclerosis (MS) development and clinical course of the disease.

MATERIALS AND METHODS

Two hundred and seventy patients with MS and 542 sex and ethnic matched controls were enrolled in the present study. An allele-specific oligonucleotide polymerase chain reaction was used to detect the polymorphism at position -308 of the TNF-alpha gene. The genotypes of TNF-beta and IL-4 were determined by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

Allelic and genotypic frequencies for these polymorphisms were similar in patients with MS and population controls or among different types of the disease.

CONCLUSION

The results of the present study suggest that the three mentioned functional polymorphisms are not likely to cause susceptibility to MS in the Iranian population.

The HLA-B7 allele confers susceptibility to breast cancer in Spanish women

BACKGROUND

Several HLA alleles are associated with susceptibility or protection in breast cancer. The particular allele varies depending on the geographical region. A study in a small group of Spanish patients using serological methods found an association with HLA-B7. We undertook a larger study in southern Spain using molecular biology techniques.

METHODS

Genotype variants of HLA class I and II were typed by PCR-SSP in 132 breast cancer patients and 382 healthy controls.

RESULTS

The frequency of the HLA-B7 allele was increased in the patients compared to the controls (P=0.0019; 95% confidence interval, 1.337-3.409, relative risk=2.135). Bonferroni correction of the P showed it was still significant (P(c)=0.0285).

CONCLUSIONS

These results support previous suggestions that HLA-B7 is associated with the development of breast cancer in our area.

A predominant role for the HLA class II region in the association of the MHC region with multiple sclerosis

Genetic susceptibility to multiple sclerosis is associated with genes of the major histocompatibility complex (MHC), particularly HLA-DRB1 and HLA-DQB1 (ref. 1). Both locus and allelic heterogeneity have been reported in this genomic region. To clarify whether HLA-DRB1 itself, nearby genes in the region encoding the MHC or combinations of these loci underlie susceptibility to multiple sclerosis, we genotyped 1,185 Canadian and Finnish families with multiple sclerosis (n = 4,203 individuals) with a high-density SNP panel spanning the genes encoding the MHC and flanking genomic regions. Strong associations in Canadian and Finnish samples were observed with blocks in the HLA class II genomic region (P < 4.9 x 10(-13) and P < 2.0 x 10(-16), respectively), but the strongest association was with HLA-DRB1 (P < 4.4 x 10(-17)). Conditioning on either HLA-DRB1 or the most significant HLA class II haplotype block found no additional block or SNP association independent of the HLA class II genomic region. This study therefore indicates that MHC-associated susceptibility to multiple sclerosis is determined by HLA class II alleles, their interactions and closely neighboring variants.

Complex interactions among MHC haplotypes in multiple sclerosis: susceptibility and resistance

Mechanisms for observed associations within the major histocompatibility complex (MHC) and autoimmune diseases including multiple sclerosis (MS) remain uncertain. Genotyping of the HLA Class II DRB1 locus in 4347 individuals from 873 multiplex families with MS highlights the genetic complexity of this locus. Excess allele sharing in sibling pair families lacking DRB1*15 and DRB1*17 (58.5% sharing; P=0.012) was comparable to that seen where parents were DRB1*15 positive (62%, P=0.0006). DRB1*17 (P=0.00027) was clearly established as an MS susceptibility allele in addition to DRB1*15 (P<10(-14)). DRB1*14 showed striking under-transmission (P=0.000032) to affected offspring newly establishing this allele as a broadly acting resistance factor. Trans interactions were seen in both DRB1*15 and non-DRB1*15 bearing genotype combinations. DRB1*08 was transmitted preferentially with DRB1*15 (P=0.0114) and, in the presence of DRB1*08, the transmission of DRB1*15 was almost invariable (37 transmissions to one non-transmission). DRB1*01 was under-transmitted to offspring in the presence of DRB1*15 (P=0.019). Both DRB1*01 and DRB1*14 haplotypes carry DQA1*01-DQB1*05 alleles, suggesting a common DQ-related mechanism for the protection mediated by these haplotypes. These studies demonstrate that it is the Class II genotype that determines susceptibility and resistance to MS. By analogy with celiac disease and type I diabetes, the pattern of susceptibility strongly supports an autoimmune aetiology.

The presence of glutamic acid at positions 71 or 74 in pocket 4 of the HLA-DRbeta1 chain is associated with the clinical course of multiple sclerosis

BACKGROUND

Primary progressive multiple sclerosis (PP-MS) differs from relapsing-remitting or secondary progressive MS (RR/SP-MS) in ways suggesting differences in the pathogenic pathways. Susceptibility to both PP-MS and RR/SP-MS is linked to carriage of the HLA molecule DRB1*1501. Several serologically defined HLA-DR groups (DR1, DR4, DR6, and DR9) occur less often in RR/SP-MS than in controls. Some or all of the HLA-DR molecules encoded by alleles in these serologically defined groups have a negatively charged glutamic acid at residue 71 or 74 of the beta1 chain (beta1(71)/beta1(74)). Residues at these positions are important in the formation of pocket 4 in the antigen binding site of the HLA-DR molecule.

OBJECTIVES

To investigate whether the presence of alleles encoding HLA-DR molecules containing glutamic acid at beta1(71)/beta1(74) correlates with the course of MS.

METHODS

HLA-DR and HLA-DQ alleles and genotypes were analysed in 121 MS patients (50 with PP-MS) and 109 controls by molecular typing.

RESULTS

Alleles encoding HLA-DR molecules containing a glutamic acid at beta1(71)/beta1(74) occurred less often in patients with RR/SP-MS than in those with PP-MS or controls. In subjects not carrying the DRB1*1501 allele, a much higher proportion of PP-MS patients carried alleles encoding HLA-DR molecules containing a glutamic acid at beta1(71)/beta1(74) than did RR/SP-MS patients or controls.

CONCLUSIONS

The amino acid residues involved in determining the shape and charge of pocket 4 of the HLA-DR beta1 chain could influence the clinical course of MS by determining protection against RR/SP-MS or susceptibility to the development of PP-MS.

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.

Genetics of multiple sclerosis

Multiple sclerosis (MS) is probably aetiologically heterogeneous. Systematic genetic epidemiological and molecular genetic studies have provided important insights. Both genetic and non-genetic (environment, stochastic) factors may be involved in susceptibility as well as outcome, but we have yet to understand their relative roles. Any environmental factor is likely to be ubiquitous and act on a population-basis rather than within the family microenvironment. Taken together, the results of genome screening studies provide strong evidence for exclusion of a major locus in MS. There are, however, many genes that seem to be associated with MS. These include, but are in no way limited to, HLA classes I and II, T-cell receptor beta, CTLA4, ICAM1, and SH2D2A. The future of MS genetics, as for most common complex disorders, will be dependent on the resources available, ranging from biological samples and comprehensive databases of clinical and epidemiological information to the development of new technologies and statistical methods.

[Determination of autoantibody for myelin antigens in the serum of patients HLA-DQB1*0602 with multiple sclerosis]

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the human central nervous system (CNS) mediated by autoimmune Th1 lymphocytes. We determined the serum levels of autoantibodies for myelin basic protein (MBP), proteolipid (PLP) and myelin oligodendrocyte glycoprotein sequence MOG 92-106 in a group of 54 healthy individuals and 26 MS patients expressing or not HLA-DQB1*0602. Regardless expression of the susceptibility allele DQB1*0602, MS patients presented marked (p<0.0001) IgG antibody production for MBP and MOG92-106. Yet, significant (p<0.0001) IgA antibody levels were mainly observed for PLP and MOG antigens. Our results suggest that other HLA class II alleles may be conferring susceptibility to MS in this population and influencing the pattern of immune recognition of encephalitogen antigens. Furthermore, distinct IgG and/or IgA autoantibody production may be contributing to the control or maintenance of the CNS inflammatory reaction.

Mapping multiple sclerosis susceptibility to the HLA-DR locus in African Americans

An underlying complex genetic susceptibility exists in multiple sclerosis (MS), and an association with the HLA-DRB1*1501-DQB1*0602 haplotype has been repeatedly demonstrated in high-risk (northern European) populations. It is unknown whether the effect is explained by the HLA-DRB1 or the HLA-DQB1 gene within the susceptibility haplotype, which are in strong linkage disequilibrium (LD). African populations are characterized by greater haplotypic diversity and distinct patterns of LD compared with northern Europeans. To better localize the HLA gene responsible for MS susceptibility, case-control and family-based association studies were performed for DRB1 and DQB1 loci in a large and well-characterized African American data set. A selective association with HLA-DRB1*15 was revealed, indicating a primary role for the DRB1 locus in MS independent of DQB1*0602. This finding is unlikely to be solely explained by admixture, since a substantial proportion of the susceptibility chromosomes from African American patients with MS displayed haplotypes consistent with an African origin.

Inflammation in multiple sclerosis: the good, the bad, and the complex

Inflammation has always been thought of as detrimental in the pathophysiology of multiple sclerosis (MS). However, emerging genetic data, magnetic-resonance-imaging studies, and immunopathological evidence challenge this simplistic view. The evidence leads to the conclusion that inflammation is tightly regulated, and that its net effect may be beneficial in MS, thus explaining some of the results from recent trials of anti-inflammatory agents. We argue that the use of anti-inflammatory drugs to treat MS may not be appropriate in all cases. Precise identification of the inflammatory pathways to be targeted in the different phases of the disease and the timing of such interventions are therefore crucial.

Optic neuromyelitis syndrome in Brazilian patients

OBJECTIVES

To report the clinical features and outcome of 24 Brazilian patients with optic neuromyelitis syndrome (ONM); discuss the underlying pathological events associated with the ONM syndrome; review the nosological situation of ONM in the group of inflammatory and demyelinating diseases of the central nervous system.

PATIENTS AND METHODS

Patients with ONM treated at the Hospital da Lagoa, Rio de Janeiro were studied. Demographic, clinical, magnetic resonance imaging, cerebrospinal fluid, and pathological data were analysed.

RESULTS

The study consisted of 20 women, four men of whom 10 were white and 14 Afro-Brazilians. Clinical course was recurrent in 22 cases and monophasic in two. Neurological manifestations at inclusion were: sensory impairment (66%), bilateral (41.6%) or unilateral blindness (20.8%), paraplegia or quadriplegia (37.5%). The EDSS was moderate/severe in 70.8%. The underlying pathological events were respectively pulmonary tuberculosis and upper respiratory infection in the two monophasic cases; in the 22 recurrent ONM patients: pulmonary tuberculosis (3), neurocysticercosis (1), polyarteritis nodosa (1), antinuclear antibody and rheumatoid factor (1), antiphospholipid antibody primary syndrome (1), diabetes mellitus (1), hypothyroidism (1), and amenorrhea-galactorrhea (4). Normal cerebrospinal fluid was found in 52% and an inflammatory profile in 48%. Only four recurrent ONM white patients had brain and spinal cord magnetic resonance imaging and cerebrospinal fluid findings compatible with the diagnosis of multiple sclerosis. Large lesions were seen in 62% of spinal magnetic resonance images. Six of 12 recurrent ONM Afro-Brazilian died. There were no statistical differences in the demographic data of the two ethnic groups. Afro-Brazilians were significantly more severely impaired and had a higher mortality rate than the white patients.

CONCLUSION

These cases were classified as follows: two monophasic acute disseminated encephalomyelitis; one recurrent disseminated encephalomyelitis; three recurrent ONM associated with Hughes syndrome, autoantibodies and polyarteritis nodosa; six recurrent ONM with endocrinopathies; and finally, four multiple sclerosis cases. The remaining cases were not associated with any other condition. It would seem clear that ONM is a syndrome rather than a single disease.

The HLA locus and multiple sclerosis in Spain. Role in disease susceptibility, clinical course and response to interferon-beta

The HLA-DR2 haplotype (DRB1*1501, DQB1*0602) on chromosome 6p21 has consistently demonstrated both association and linkage with multiple sclerosis (MS) in case-control and family studies, particularly in Caucasians of Northern European descent. However, the role of a gene within this region in determining clinical features or response to immunotherapy remains largely unknown. A new familial MS data set from the Mediterranean Spanish Basin was collected according to rigorous ascertainment criteria. We confirm, primarily in the cohort originating from Continental Spain, that similar to other high-risk groups, there was a significant association with HLA-DR2. No other DR or DQ alleles were found to be associated with disease susceptibility nor were alleles at the class I A and B loci. Overall, the effect of HLA appears to be less substantial than that observed in a reference US population with a higher disease incidence. No effect of the HLA-DR2 haplotype on age of onset, initial clinical symptoms and disease course was observed. Similarly, no difference in the distribution of responders and nonresponders to interferon-beta (IFNB) therapy, as defined by primary and secondary end points, was observed when individuals were stratified according to HLA-DR2 status.

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.

Type 1A diabetes mellitus-associated autoimmunity

Type 1A diabetes mellitus has become one of the most intensively studied autoimmune disorders, with characterized animal models and extensive prospective studies of the development of anti-islet autoimmunity. It is now possible to predict the development of type 1A diabetes mellitus, beginning with HLA-encoded genetic susceptibility, followed by the development of a series of anti-islet autoantibodies. Prediction primarily is based on the detection of multiple anti-islet autoantibodies reacting with cloned islet antigens. Multiple international workshops fostered the development of specific and sensitive radioassays for autoantibodies reacting with GAD65 (glutamic acid decarboxylase), ICA512 (also termed IA-2, a tyrosine phosphatase-like protein), and insulin. Similar high throughput radioassays have been applied using autoantigens for additional autoimmune disorders including celiac disease and Addison's disease. Relatives of patients with type 1A diabetes mellitus inherit susceptibility to express multiple autoantibodies, and a subset of autoantibody-positive individuals inherit susceptibility to progress to overt disease. This article reviews autoimmune disorders associated with type 1A diabetes mellitus.