The HLA-Dw2 haplotype segregates closely with multiple sclerosis in multiplex families

Gender influence in EBV antibody response in multiple sclerosis patients from Kuwait

BACKGROUND

Epstein-Barr virus (EBV) infection is implicated with multiple sclerosis (MS) risk, exacerbation, and progression. The HLA-DRB1*1501 haplotype is a strong MS risk factor consistently documented in MS populations. There are no studies of EBV infections and HLA-DRB1*1501 haplotype associating with MS from Kuwait where MS prevalence has increased significantly.

OBJECTIVES

To determine the association of EBV infection with MS incidence, and to investigate HLA-DRB1*1501 as a potential genetic risk factor for MS in Kuwait.

METHODS

This is a case-control study involving 141 MS patients and 40 healthy controls. Antibody titers against EBV antigens' viral capsid antigen (VCA) and Epstein-Barr nuclear antigen 1 (EBNA1) were measured using enzyme-linked immunosorbent assays. HLA-DRB1*1501 haplotype assessment was done using rs3135005 TaqMan genotyping assay.

RESULTS

Antibody titers against EBV were significantly elevated in MS patients compared to healthy controls (anti-EBNA1, p=0.008; anti-VCA, p=0.028). MS males had higher antibody titers to EBNA1 than healthy male controls (p=0.005) and female MS patients (p=0.03). HLA-DRB1*1501 haplotype genotypes failed to generate a risk association with MS or EBV antibody titers (p=0.6).

CONCLUSION

An increased immune response to EBV infection is associated with MS incidence influenced by the type of antigen and sex. HLA-DRB1*1501 haplotype is not associated with MS risk in our Kuwaiti MS cohort.

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.

Myelin-reactive type B T cells and T cells specific for low-affinity MHC-binding myelin peptides escape tolerance in HLA-DR transgenic mice

Genes of the MHC show the strongest genetic association with multiple sclerosis (MS), but the underlying mechanisms have remained unresolved. In this study, we asked whether the MS-associated MHC class II molecules, HLA-DRB1*1501, HLA-DRB5*0101, and HLA-DRB1*0401, contribute to autoimmune CNS demyelination by promoting pathogenic T cell responses to human myelin basic protein (hMBP), using three transgenic (Tg) mouse lines expressing these MHC molecules. Unexpectedly, profound T cell tolerance to the high-affinity MHC-binding hMBP82-100 epitope was observed in all Tg mouse lines. T cell tolerance to hMBP82-100 was abolished upon back-crossing the HLA-DR Tg mice to MBP-deficient mice. In contrast, T cell tolerance was incomplete for low-affinity MHC-binding hMBP epitopes. Furthermore, hMBP82-100-specific type B T cells escaped tolerance in HLA-DRB5*0101 Tg mice. Importantly, T cells specific for low-affinity MHC-binding hMBP epitopes and hMBP82-100-specific type B T cells were highly encephalitogenic. Collectively, the results show that MS-associated MHC class II molecules are highly efficient at inducing T cell tolerance to high-affinity MHC-binding epitope, whereas autoreactive T cells specific for the low-affinity MHC-binding epitopes and type B T cells can escape the induction of T cell tolerance and may promote MS.

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.

Second-generation peptidomimetic inhibitors of antigen presentation effectively treat autoimmune diseases in HLA-DR-transgenic mouse models

Peptidomimetic compounds that bind to major histocompatibility complex class II molecules and are resistant to cathepsins can competitively inhibit the presentation of processed protein antigens. Therefore, compounds that bind to autoimmune disease-associated class II molecules are expected to compete with autoantigens for presentation and thereby interrupt the disease process. The first generation of such competitors developed for rheumatoid arthritis-associated HLA-DR molecules, although resistant to cathepsins, has remained sensitive to plasma proteases, and was thus unlikely to be effective in vivo. We have therefore produced a second generation of compounds that are resistant to cathepsins and stable in plasma while maintaining binding affinity for HLA-DR molecules associated with rheumatoid arthritis and multiple sclerosis. Selected compounds of this series are shown to inhibit antigen presentation in vivo, as well as effectively treat collagen induced arthritis and experimental autoimmune encephalomyelitis in HLA-DR transgenic mouse models.

Peptide 15-mers of defined sequence that substitute for random amino acid copolymers in amelioration of experimental autoimmune encephalomyelitis

Myelin basic protein (MBP) is a major candidate autoantigen in multiple sclerosis (MS). Its immunodominant epitope, MBP 85-99, forms a complex with human leukocyte antigen (HLA)-DR2 with which multiple sclerosis is genetically associated. Copolymer 1 (Copaxone), a random amino acid copolymer [poly (Y,E,A,K)n] as well as two modified synthetic copolymers [poly (F,Y,A,K)n and poly (V,W,A,K)n] also form complexes with HLA-DR2 (DRA/DRB1*1501) and compete with MBP 85-99 for binding. Moreover, two high-affinity synthetic peptide 15-mers that could inhibit binding even more effectively were previously designed. Here, we show that further-modified peptide 15-mers inhibited even more strongly (in order J5 > J3 > J2) both the binding of MBP 85-99 to HLA-DR2 and IL-2 production by two MBP 85-99-specific HLA-DR2-restricted T cells. J5, J3, and J2 also suppressed both MBP 85-99-induced experimental autoimmune encephalomyelitis (EAE) in humanized mice and proteolipid protein 139-151-induced EAE in SJL/J mice. Moreover, none of these previously uncharacterized peptide inhibitors crossreacted with MBP 85-99- or proteolipid protein 139-151-specific T cells. In both cases, spleen and lymph node cultures stimulated with these peptides produced large amounts of Th2 cytokines (IL-4 and IL-10), and adoptive transfer of established T cell lines suppressed disease induction. These peptide 15-mers provide specific, nonrandom sequences that appear to be at least as effective as random copolymers in suppressing EAE in several models.

The pathogenesis of primary progressive multiple sclerosis: antibody-mediated attack and no repair?

Primary progressive multiple sclerosis (MS) differs from the more common form of MS which has an initial relapsing-remitting course in a number of ways, including pathological features, clinical course, differential diagnosis and response to treatment. The lesions in primary progressive MS tend to be more diffuse, less inflammatory and less likely to remyelinate than those occurring in relapsing-remitting MS and secondary progressive MS; there are also fewer focal lesions in the brain in primary progressive MS. Recent evidence suggests that antibodies to central nervous system (CNS) antigens have an important role in disease progression. Such antibodies could cause demyelination, inhibit remyelination and cause axonal destruction. Ongoing immune attack by autoantibody and lack of CNS repair could be responsible for the gradually increasing disability in primary progressive MS. Further research on the B-cell and autoantibody response in primary progressive MS might lead to advances in diagnosis and treatment. Inhibition of autoantibody production by inducing B-cell apoptosis with rituximab is a potential new therapy for primary progressive MS.

Familial bipolar disorder and multiple sclerosis: a three-generation HLA family study

The coexistence of bipolar disorder (BD) and multiple sclerosis (MS) is well known. Manic symptoms may represent initial symptoms of MS, at least in some cases, and follow the MS-HLA phenotype frequencies. The purpose of this study was to examine the possible relation of BD and MS based on an HLA family study of a woman with BD and comorbid MS, with family history of BD. Five members of the family from three generations (the patient, her mother, her brother, and her two daughters) were examined regarding the two disorders and the HLA class I and II specificities, performed by serology and molecular techniques. Her deceased father, her brother, and her older daughter suffered from BD. Moreover, in her brother, BD and MS comorbidity was diagnosed. The three affected members and the nonaffected grandmother share the same class I and II, HLA-A2, B18, CW8, DR2, DQ1 haplotype. The shared class II, HLA-DR2, DQ1 haplotype among affected individuals, which is well known to be associated with MS in Caucasians, suggests a possible susceptibility locus for BD, mapped on chromosome 6, very close to the HLA region, underlying the clinical comorbidity of the two disorders.

Genetic basis for clinical expression in multiple sclerosis

Multiple sclerosis is a clinically heterogeneous demyelinating disease and an important cause of acquired neurological disability. An underlying complex genetic susceptibility plays an important role in multiple sclerosis aetiology; however, the role of genetic factors in determining clinical features of multiple sclerosis is unknown. We studied 184 stringently ascertained Caucasian multiple sclerosis families with multiple affected cases. A detailed evaluation of patient histories identified clinical variables including age of onset, initial clinical manifestations and disease severity. The concordance within families for continuous and categorical clinical variables was investigated using an intraclass correlation or Cohen's kappa coefficient, respectively. Genetic analyses included model-dependent, model-independent and association methodology. Linear and logistic regression models were used to evaluate the effect of human leucocyte antigen (HLA)-DR2 (DRB1*1501, DQB1*0602) on clinical outcome, taking account of correlation within families. Significant concordance for early clinical manifestations within families was observed for individuals with exclusive optic neuritis and/or spinal cord involvement as first and second multiple sclerosis attacks (P < 10(-6)). Linkage (LOD = 3.80, theta = 0.20) and association (P = 0.0002) to HLA-DR were present in the dataset; however, linkage was restricted to families in which the DR2 haplotype was present in at least one nuclear member. No evidence for linkage to HLA-DR in DR2-negative families was observed. When families were stratified by concordance of early clinical manifestations, a significant DR2 association was present in all subgroups. Concordance for early manifestations of multiple sclerosis was present in this familial dataset, but was not associated with HLA-DR2. The association of DR2 in families with different clinical presentations suggests that a common basis exists for susceptibility in multiple sclerosis. However, non-HLA genes or other epigenetic factors must modulate disease expression. Locus heterogeneity at the HLA region suggests a distinct immunopathogenesis in DR2 negative patients.

No linkage or association of the nitric oxide synthase genes to multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) of unknown etiology. Nitric oxide (NO) is a free radical that participates in a variety of biological processes. It is an important mediator in the immune response. Several studies indicate involvement of NO in the pathogenesis of MS. We studied five markers within the three NO synthase genes with regards to susceptibility and disease course in 156 affected sib-pairs and in 96 "benign" and 96 "severe" definite MS patients and 148 controls. We found no significant association or evidence for linkage in our data sets.

Synthetic peptides that inhibit binding of the myelin basic protein 85-99 epitope to multiple sclerosis-associated HLA-DR2 molecules and MBP-specific T-cell responses

Copolymer 1 (Cop 1, poly [Y, E, A, K]) is a random synthetic amino acid copolymer effective in the treatment of relapsing forms of multiple sclerosis (MS), a disease that is linked to HLA-DR2 (DRB1*1501). In the present study various peptides, synthesized according to the binding motifs for both the immunodominant epitope of myelin basic protein (MBP) 85-99, a candidate autoantigen in MS, and Cop 1, differentially inhibited binding of these antigens to disease-associated HLA-DR2 (DRB1*1501) molecules. In particular, two peptides with residue K at position P-1, as referred to MBP 85-99, inhibited effectively the binding of both biotinylated MBP 85-99 and Cop 1 to HLA-DR2 molecules as well as IL-2 production by two MBP-specific HLA-DR2-restricted T-cell clones. These findings suggest the possible utility of these compounds or their more stable derivatives in treatment of MS.

Crystal structure of a superantigen bound to the high-affinity, zinc-dependent site on MHC class II

MHC class II molecules possess two binding sites for bacterial superantigens (SAGs): a low-affinity site on the alpha chain and a high-affinity, zinc-dependent site on the beta chain. Only the former has been defined crystallographically. We report the structure of streptococcal pyrogenic exotoxin C (SPE-C) complexed with HLA-DR2a (DRA*0101, DRB5*0101) bearing a self-peptide from myelin basic protein (MBP). SPE-C binds the beta chain through a zinc bridge that links the SAG and class II molecules. Surprisingly, SPE-C also makes extensive contacts with the MBP peptide, such that peptide accounts for one third of the surface area of the MHC molecule buried in the complex, similar to TCR-peptide/MHC complexes. Thus, SPE-C may optimize T cell responses by mimicking the peptide dependence of conventional antigen presentation and recognition.

Structural basis for the binding of an immunodominant peptide from myelin basic protein in different registers by two HLA-DR2 proteins

Susceptibility to multiple sclerosis (MS) is associated with certain MHC class II haplotypes, in particular HLA-DR2. Two DR beta chains, DRB1*1501 and DRB5*0101, are co-expressed in the HLA-DR2 haplotype, resulting in the formation of two functional cell surface heterodimers, HLA-DR2a (DRA*0101, DRB5*0101) and HLA-DR2b (DRA*0101, DRB1*1501). Both isotypes can present an immunodominant peptide of myelin basic protein (MBP 84-102) to MBP-specific T cells from MS patients. We have determined the crystal structure of HLA-DR2a complexed with MBP 86-105 to 1.9 A resolution. A comparison of this structure with that of HLA-DR2b complexed with MBP 85-99, reported previously, reveals that the peptide register is shifted by three residues, such that the MBP peptide is bound in strikingly different conformations by the two MHC molecules. This shift in binding register is attributable to a large P1 pocket in DR2a, which accommodates Phe92, in conjunction with a relatively shallow P4 pocket, which is occupied by Ile95. In DR2b, by contrast, the small P1 pocket accommodates Val89, while the deep P4 pocket is filled by Phe92. In both complexes, however, the C-terminal half of the peptide is positioned higher in the binding groove than in other MHC class II/peptide structures. As a result of the register shift, different side-chains of the MBP peptide are displayed for interaction with T cell receptors in the DR2a and DR2b complexes. These results demonstrate that MHC molecules can impose different alignments and conformations on the same bound peptide as a consequence of topological differences in their peptide-binding sites, thereby creating distinct T cell epitopes.

The epidemiology and the pathogenesis of inflammatory bowel disease

The etiology of inflammatory bowel disease (IBD) is still unknown. However, a satisfactory solution cannot be far away. IBD actually encompasses two diseases, i.e. Crohn's disease (CD) and ulcerous colitis (UC). These diseases resemble each other so closely that they cannot be distinguished even pathologically, but differ from each other sufficiently to regard them as independent entities. Epidemiological observations may be helpful in identifying the true causative factors of this evasive disease. Geographically, the prevalence of the disease has a slope from North to South and, to a lesser degree, from West to East. The Western-Eastern discrepancy can be attributed to a difference in Western life styles. The incidence of the disease has been increasing world-wide of late, but its spread has been slowing down in highly affected countries. Racial and ethnic relations in different populations and immigration studies offer interesting data which can reflect genetic, inherited, environmental and behavioural factors. The disease seems to have a characteristic racial-ethnic distribution: the Jewish population is highly susceptible everywhere, but its prevalence in that population nears that of the domestic society in which they live. In Hungary, the Roma (Gypsies) have a considerably lower prevalence than the average population. This can be attributed to a genetic or environmental influence. According to age, the onset of the disease occurs more often in the second or the third decade of life, but there also is another peak in the 60s. Regarding sexual distribution, there is a slight preponderance of colitis ulcerosa in men and of Crohn's disease in women. It may correspond to the stronger auto-immune affection in the process of Crohn's disease. Environmental factors and behavioural influences also are investigated. Diet, the role of the early ages, smoking habits and the influence of hormonal status and drugs are viewed as useful contributing factors in the manifestation of the disease. Genetic studies show that one-fourth of IBD patients have an affected family member. HLAB27 histocombatibility also plays an important, but not determining role in the development of the disease. Genetic factors seem to have a stronger influence in Crohn's disease than ulcerative colitis. The existence of multiple sclerosis-IBD families may reflect the common genetic background or the similar microbial effect as well. A great number of bacterial and viral factors has been suspected of being infectious factors in IBD, mostly in CD. Mycobacteria, Yersinia, Campylobacter, Clostridium, Clamidias, etc. as well as bacteria and some viruses such as herpes and rotavirus and the primary measles virus. None of them has been proven as a real and exclusively pathogenic factor. Immunological background has an important function in the manifestation of the disease. If an individual has a genetic susceptibility to infections, the down regulation of an inflammation in the bowel wall does not occur in a proper way. This initiates the auto-immune process which is a self-increasing cycle. Extra-intestinal manifestations of IBD are of high importance because they can not only follow intestinal symptoms, but precede them by years. Hepatic and biliary disturbances (primary sclerosing cholangitis), are the most serious complications. Mucocutaneous manifestations can be the first appearance of the main disease (in the mouth). Auto-immune consequences (erythema nodosum) or complications caused even by the therapy can occur. Ocular and musculoskeletal manifestations supposedly have the same genetic background and often precede the intestinal symptoms. Considering the epidemiological, genetic and immunological data, we can conclude that ulcerative colitis and Crohn's disease are heterogeneous disorders of mutifactorial etiology in which hereditary (genetic) and environmental (microbial, behaviour) factors interact to produce the disease.

The genetics of multiple sclerosis. A review

Multiple sclerosis (MS) is characterized by chronic inflammation and demyelination in the central nervous system (CNS). Although the etiology of MS is unknown, both genetic and environmental contributions to the pathogenesis are inferred from epidemiologic studies. Geographic distributions and epidemics of MS and data from migration studies provide evidence for some, thus far unidentified, environmental effects. The co-occurrence of MS with high and low frequencies in ethnic groups often sharing an environment, the increased recurrence rate in families, and the high concordance rate among identical twins point to inheritable determinants of susceptibility. Based on the autoimmune hypothesis of demyelination, genetic studies sought associations between MS and polymorphic alleles of candidate genes which regulate either the immune response or myelin production. The most consistent finding in case-control studies was the association with the major histocompatibility complex (MHC) (also called human leukocyte antigen--HLA) class II, DR15, DQ6, Dw2 haplotype. Studies on other gene products encoded within or close to the MHC complex on chromosome 6p21.3 (e.g., HLA DP, complement components, transporter proteins, tumor necrosis factor, and myelin-oligodendrocyte glycoprotein) resulted in conflicting observations in different patient populations. The potential contribution of polymorphic alleles within the genes of the T-cell receptor alpha beta chains, immunoglobulins, cytokines, and oligodendrocyte growth factors or their receptors to MS susceptibility either remains equivocal or is rejected. Studies on families with multiple affected members have revealed that MS is a complex trait, that the contribution of individual genes to susceptibility is probably small, and that differences are possible between familial and sporadic forms. The development of molecular and computer technologies have facilitated the performance of comprehensive genomic scans in multiplex families, which have confirmed the possible linkage of multiple loci to susceptibility, each with a minor contribution. Several provisional sites were reported, but only 6p21 (MHC complex), 5p14, and 17q22 were positive in more than one study. The British update demonstrated segregation among regions of interest depending on DR15 sharing, and excluded a gene of major effect from 95%, and one with a moderate effect from 65% of the genome. The extended study by the US collaboration group revealed that the MHC linkage was limited to families segregating HLA DR2 alleles, which suggested that linkage to the MHC is related to the HLA DR2 association, and that sporadic and familial MS share at least one common susceptibility marker. Further identification of MS susceptibility loci may involve additional family sets, more polymorphic markers, and the exploration of telomeric chromosomal regions. Data from these studies may further elucidate pathogenic mechanisms of MS.

A study of the HLA-DR region in clinical subgroups of multiple sclerosis and its influence on prognosis

OBJECTIVE

To investigate the HLA-DR associations in relapsing-remitting/secondary progressive multiple sclerosis (RR/SPMS) and primary progressive MS (PPMS). The HLA-DR2 allele (or its split, HLA-DRB1*15) is felt to be a risk factor for MS, rather than a genetic marker for the population of origin. Some studies have indicated a different HLA-DR antigen profile in PPMS patients compared with those having an initially relapsing-remitting course, only those with relapsing disease showing an increase in HLA-DR2. Association of PPMS with DR4 has been suggested. Several DR alleles have also been felt to influence the prognosis in MS.

METHODS

Genomic DNA was prepared from peripheral blood of 202 RR/SPMS patients identified in a population-based prevalence study, 102 PPMS patients identified throughout Northern Ireland and 398 normal controls (Nor) matched for the postcode areas of those identified in the prevalence study. Samples were typed for the HLA-DR antigens using polymerase chain reaction (PCR) technology and sequence specific oligonucleotide probes (SSOP).

RESULTS

A high incidence of HLA-DRB1*15 was found in each MS group - PPMS (63.73%), RR/SPMS (66.83%) - compared with normals (32.41%), (PPMS vs. Nor, P<0.0001: RR/SPMS vs. Nor, P<0.0001). HLA-DRB1*04 occurred at a lower incidence in both MS groups compared with controls - RR/SPMS (22%), PPMS (30%), Nor (35%). Overall, highly significant differences existed across the full HLA-DR allele distribution (RR/SPMS vs. Nor, P<0.0001, df=12: PPMS vs. Nor, P=0.0007, df=12). No significant differences existed between PPMS and RR/SPMS (P=0.47, df=12), and the allele distributions in benign and aggressive MS were similar.

CONCLUSIONS

These data suggest that in this population, HLA-DRB1*15 is indeed associated with PPMS and that PPMS has a HLA-DR profile distinct from the normal population but not from those with an initially relapsing-remitting course. No single allele is associated with either a good or poor prognosis.

Familial multiple sclerosis: volumetric assessment in clinically symptomatic and asymptomatic individuals

A genetic basis for clustering of multiple sclerosis (MS) cases, based on studies of MS families, has been proposed for decades. Few reports provide detailed neurological as well as neuroradiological findings on these patients. We report total T2-weighted intracranial lesion volumes on members of three familial MS cohorts: a mother and father with conjugal MS with one affected son and a neurologically normal son and daughter, one pair of monozygotic twin sisters with MS, and a female sibling pair with MS. We hypothesized that asymptomatic siblings in a family with two affected parents and another affected child might demonstrate clinically silent T2-weighted lesions; and that monozygotic twins with MS are more likely to express similar T2-weighted lesion volumes than non-twin sibling pairs. We found clinically silent lesions in unaffected children of the symptomatic parent couple, with a significant difference in total T2 lesion volume between these unaffected siblings and their parents, as well as their affected brother. In our other sibling pairs, T2 lesion volumes were similar between the twins and significantly different in the non-twin pair, despite similar levels of clinical functioning as determined by EDSS scoring. These results suggest that foci of demyelination might be expected in clinically normal offspring of parents with MS, possibly reflecting a genetic predisposition to subsequent development of MS.

Structural Features of Autoreactive TCR That Determine the Degree of Degeneracy in Peptide Recognition

Structural aspects of human TCRs that allow the activation of autoreactive T cells by diverse microbial peptides were examined using two human myelin basic protein (MBP)-specific T cell clones. The TCR sequences of these clones differed only in the N region of TCR-α and -β since the clones had the same Vα-Jα and Vβ-Jβ rearrangements. The two clones had a similar fine specificity for the MBP peptide, except for the P5 position of the peptide (lysine). In the crystal structure of the HLA-DR2/MBP peptide complex, P5 lysine is a prominent, solvent-exposed residue in the center of the DR2/MBP peptide surface. Five microbial peptides with conservative or nonconservative changes at the P5 position (lysine to arginine, serine, or proline) activated one of these clones. In contrast, the other clone was activated only by three of these peptides which had a conservative lysine to arginine change at P5. The degree of specificity/degeneracy in recognition of the P5 side chain was the key difference between these TCRs since the Escherichia coli/Haemophilus influenzae peptide stimulated both clones when the P5 position was substituted from serine to arginine. These results demonstrate that the complementarity-determining region 3 loops contribute to the degree of degeneracy in peptide recognition by human MBP-specific TCRs.

Crystal structure of HLA-DR2 (DRA*0101, DRB1*1501) complexed with a peptide from human myelin basic protein

Susceptibility to multiple sclerosis is associated with the human histocompatibility leukocyte antigen (HLA)-DR2 (DRB1*1501) haplotype. The structure of HLA-DR2 was determined with a bound peptide from human myelin basic protein (MBP) that is immunodominant for human MBP-specific T cells. Residues of MBP peptide that are important for T cell receptor recognition are prominent, solvent exposed residues in the crystal structure. A distinguishing feature of the HLA-DR2 peptide binding site is a large, primarily hydrophobic P4 pocket that accommodates a phenylalanine of the MBP peptide. The necessary space for this aromatic side chain is created by an alanine at the polymorphic DRbeta 71 position. These features make the P4 pocket of HLA-DR2 distinct from DR molecules associated with other autoimmune diseases.

Expression and crystallization of the complex of HLA-DR2 (DRA, DRB1*1501) and an immunodominant peptide of human myelin basic protein

HLA-DR2 is associated with susceptibility to multiple sclerosis (MS). A peptide from human myelin basic protein (MBP, residues 85-99) was previously found to bind to purified HLA-DR2 (DRA, DRB1*1501) and to be recognized by human MBP-specific T cell clones. Soluble HLA-DR2 was expressed in the baculovirus system by replacing the hydrophobic transmembrane regions and cytoplasmic segments of DRalpha and DRbeta with leucine zipper dimerization domains from the transcription factors Fos and Jun. In the expression construct, the MBP(85-99) sequence was covalently linked to the N terminus of the mature DRbeta chain. The recombinant protein was secreted by Sf9 cells infected with the recombinant baculovirus and purified by affinity chromatography. The leucine zipper dimerization domains were then cleaved from the assembled HLA-DR2/MBP peptide complex with V8 protease, and the protein was further purified by anion-exchange HPLC. Analysis by HPLC gel filtration indicated that the HLA-DR2/MBP peptide complex did not have a tendency to aggregate. The purified HLA-DR2/MBP peptide complex readily crystallized by the hanging drop method in 15-18% polyethylene glycol 6000/100 mM glycine, pH 3.5. At a synchrotron radiation source, a crystal with a tetragonal space group diffracted to a resolution of 2.6 A. The expression of such homogenous HLA-DR/peptide complexes may facilitate cocrystallization with T cell receptors as well as other molecules involved in T cell receptor recognition and signaling.

Quantitative trait loci disposing for both experimental arthritis and encephalomyelitis in the DA rat; impact on severity of myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis and antibody isotype pattern

Quantitative trait loci (QTL) controlling inflammatory diseases with different organ specificity may hypothetically either be unique for one disease or shared among different diseases. We have investigated whether five non-MHC QTL controlling susceptibility to experimental arthritis in the DA rat also influence myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) in an F2 intercross between inbred DA and PVG.RT1a rats. Two of the five chromosome regions affecting arthritis in the DA rat also regulate phenotypes of EAE. The DA allele at markers in Cia3 (collagen-induced arthritis QTL) on chromosome 4 is associated with more severe EAE and high levels of anti-MOG antibodies of the IgG2c subclass. Since production of antibodies of the IgG2c subclass may be stimulated by Th1 cells, and there is previous evidence that such cells promote EAE, it is possible that both of the studied phenotypes are controlled by the same gene or genes regulating Th1/Th2 cell differentiation. Furthermore, we show that Oia2 (oil-induced arthritis QTL) on chromosome 4 regulates levels of anti-MOG antibodies of the IgG1 subclass and of anti-MOG IgE, but that this gene region does not affect clinical disease severity in our study. Since production of IgE and IgG1 may be stimulated by Th2 cells, this QTL may also control Th1/Th2 bias. We conclude that Cia3 and Oia2 regulate MOG-induced EAE in rats. Furthermore, since both EAE and arthritis phenotypes co-localize to these gene regions, they may harbor genes which are key regulators of pathogenic immune responses.

Identification of multiple sclerosis-associated genes

Multiple sclerosis (MS) is a complex genetic trait. Analyses to identify genetic variants that increase susceptibility to MS have primarily focused on candidate genes, either in family linkage investigations or in association (linkage disequilibrium) studies in sporadic cases and control subjects. Most of the candidate genes considered to date either influence immune function or encode structural myelin proteins. Recently, three preliminary whole genomic surveys were completed, and they reveal multiple loci of possible genetic linkage that are worthy of further study. No convincing evidence for a single strong locus has emerged from analysis of the three studies. Linkage promises to focus the future choice of candidate genes for further investigation.

The association of HLA-DR15 and intermediate uveitis

PURPOSE

To evaluate the association between human leukocyte antigen (HLA-DR15) specificity and intermediate uveitis.

METHODS

Eighteen patients diagnosed with intermediate uveitis underwent HLA-DR15 serotyping. Additionally, DNA-based phenotyping for a specific HLA-DR15 allele was performed in four patients. The clinical features of HLA-DR15-positive intermediate uveitis were compared with those of HLA-DR15-negative intermediate uveitis.

RESULTS

Thirteen of 18 patients (72%) were positive for HLA-DR15. The frequency of the HLA-DR15 specificity in intermediate uveitis patients was significantly higher than in the control subjects (relative risk, 6.36; P < .001). Each of four patients tested carried the specific allele, DR beta 1*1501, which has been associated with multiple sclerosis. In the HLA-DR15-positive group were four patients (31%) with coexisting multiple sclerosis or optic neuritis, one patient with coexisting narcolepsy, and three patients (23%) with a family history of multiple sclerosis. Retinal periphlebitis, especially if bilateral, was a frequent ophthalmoscopic finding in HLA-DR15-positive intermediate uveitis.

CONCLUSIONS

This study identifies a significant association between intermediate uveitis and the HLA-DR15 specificity. Patients who are HLA-DR15-positive and have intermediate uveitis may have systemic findings of another HLA-DR15-related disorder. Intermediate uveitis may belong to a constellation of HLA-DR15-related disorders, which includes multiple sclerosis, optic neuritis, and narcolepsy.

Genetics of demyelinating diseases

Multiple sclerosis (MS), the prototypic demyelinating disease in humans, is the most common cause of acquired neurological dysfunction arising between early to mid adulthood. MS is an inflammatory disorder and is believed to result from an autoimmune response, directed against myelin proteins and perhaps other antigens, resulting in demyelination and dense astrogliosis. A genetic component in MS is indicated by an increased relative risk to siblings compared to the general population (lambda s) of 20-40, and an increased concordance rate in monozygotic compared to dizygotic twins. Association and/or linkage studies to candidate genes have yielded a considerable number of reports showing significant genetic effects for the major histocompatibility complex (MHC), immunoglobulin heavy chain, T cell antigen receptor, and myelin basic protein loci. With the exception of the MHC, however, these results have been difficult to replicate or apply beyond isolated populations. Recently, a multi-analytical genomic screen effort was completed to identify genomic regions potentially harboring MS susceptibility genes. Nineteen such regions were identified. The data confirm the reported genetic effect of the MHC region. However, no single locus generated overwhelming evidence of linkage. These results suggest a multifactorial etiology, including both environmental and multiple genetic factors of moderate effect.

Epidemiology of multiple sclerosis

The inhomogeneous distribution of MS may represent an important clue about the cause of the disease. The prevalence of MS appears to be increasing in many regions of the world, although it is likely that in a majority of regions surveyed, this increase is attributable to differences in ascertainment over the relatively short period that MS has been surveyed worldwide, which is almost exclusively the last 50 years. MS occurs most frequently in regions populated by northern Europeans, and in these areas, it is much more common in the northern European population than in the indigenous populations. MS occurs in relatives of MS patients at a rate 10- to 50-fold greater than in the general population. On average, the absolute risk to a first-degree relative of an MS patient is 2% to 5%, depending on the exact degree of relatedness. Although the mode of transmission is not certain, a multigenic pattern best fits the observed pattern of transmission. A majority of monozygotic twins are discordant for MS, indicating that a major component of MS susceptibility is environmentally determined, although recent observations in adopted relatives suggest that this risk is not transmissible. Rare epidemics of MS involving small numbers of individuals in geographically isolated regions have been reported. A number of migrant studies suggest that the risk of acquiring MS may be altered by migration, although some also support genetic factors. Analytic approaches to address the role of various risk factors include ecologic studies, case-control studies, and cohort studies. Ecologic studies are best suited for addressing risk factors that influence overall population risk, whereas case-control studies are best suited for addressing risk factors that pertain to individuals within a population. If a risk factor is distributed homogeneously in a given population, a case-control study is insensitive to its effect. Improved methodology to diminish the biases inherent in case-control studies and identification of other important risk factors from basic scientific studies undoubtedly will be important for analytic epidemiologic studies of the future. Furthermore, analysis of highly informative populations, such as discordant identical twins and adoptive siblings of MS patients, likely will improve the specificity of case-control studies by minimizing the vast number of potential differences between cases and controls.

Acute optic neuritis: myelin basic protein and proteolipid protein antibodies, affinity, and the HLA system

Anti-myelin basic protein, anti-proteolipid protein, and anti-myelin basic protein peptide (amino acid residues 1-20, 63-88, and 89-101) antibody-secreting cells were studied in 20 patients with idiopathic optic neuritis, 20 with optic neuritis as part of multiple sclerosis, and 20 neurological control subjects. Antibody-secreting cells were enumerated with an immunospot assay; the relative binding affinity of the antibodies was estimated by elution with thiocyanate. Patients with optic neuritis had more anti-myelin basic protein and anti-proteolipid protein antibodies than did control subjects (both p < 0.05); there was no difference between idiopathic optic neuritis and optic neuritis as a symptom of multiple sclerosis. Presence of the multiple sclerosis-associated DRB1*1501 gene was not associated with preferential synthesis of high-affinity antibodies reactive with a single myelin basic protein peptide or with preferential synthesis of either anti-myelin basic protein or anti-proteolipid protein antibodies. The results demonstrate a potential for intrathecal synthesis of both anti-myelin basic protein and anti-proteolipid protein antibodies of high apparent affinity in patients with optic neuritis.

Multiple sclerosis and the HLA-D region: linkage and association studies

Inheritance patterns of multiple sclerosis (MS) in multiplex families suggest a complex aetiology involving environmental and genetically determined components. The association between the HLA class II DR15, DQ6, Dw2 haplotype and MS has been well documented in patients with ancestral origins in Northern Europe. Conversely, linkage analysis of this region in multiplex families, derived from a population base, has generated negative results. Thus, given the Dw2 specificity association, evidence implicating this locus in disease susceptibility appears contradictory. We have collected and determined the HLA-DR and -DQ haplotypes of 115 sibling pairs with multiple sclerosis, and confirm a significant association with the Dw2-associated haplotype, both in index cases and their affected siblings compared with controls. However, using a sibling pair linkage analysis that restricts haplotype sharing probabilities to defined genetic models, we have not observed linkage of this region to susceptibility in MS. We discuss the basis for association and linkage and conclude that the DR15, DQ6, Dw2 haplotype does represent a susceptibility locus but its contribution to the pathogenesis is small; although it may interact epistatically with other susceptibility genes, this haplotype is not necessary for disease expression.

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.