HLA-DP: a class II restriction molecule involved in epitope spreading during the development of multiple sclerosis

HLA-DPB1*03 as Risk Allele and HLA-DPB1*04 as Protective Allele for Both Early- and Adult-Onset Multiple Sclerosis in a Hellenic Cohort

Background: Human Leucocyte Antigens (HLA) represent the genetic loci most strongly linked to Multiple Sclerosis (MS). Apart from HLA-DR and HLA–DQ, HLA-DP alleles have been previously studied regarding their role in MS pathogenesis, but to a much lesser extent. Our objective was to investigate the risk/resistance influence of HLA-DPB1 alleles in Hellenic patients with early- and adult-onset MS (EOMS/AOMS), and possible associations with the HLA-DRB1*15:01 risk allele. Methods: One hundred MS-patients (28 EOMS, 72 AOMS) fulfilling the McDonald-2010 criteria were enrolled. HLA genotyping was performed with standard low-resolution Sequence-Specific Oligonucleotide techniques. Demographics, clinical and laboratory data were statistically processed using well-defined parametric and nonparametric methods and the SPSSv22.0 software. Results: No significant HLA-DPB1 differences were found between EOMS and AOMS patients for 23 distinct HLA-DPB1 and 12 HLA-DRB1 alleles. The HLA-DPB1*03 allele frequency was found to be significantly increased, and the HLA-DPB1*02 allele frequency significantly decreased, in AOMS patients compared to controls. The HLA-DPB1*04 allele was to be found significantly decreased in AOMS and EOMS patients compared to controls. Conclusions: Our study supports the previously reported risk susceptibility role of the HLA-DPB1*03 allele in AOMS among Caucasians. Additionally, we report for the first time a protective role of the HLA-DPB1*04 allele among Hellenic patients with both EOMS and AOMS.

Modulation of MS-like disease by a multi epitope protein is mediated by induction of CD11c+CD11b+Gr1+ myeloid-derived dendritic cells

Specific neutralization of the pathogenic autoimmune cells is the ultimate goal in therapy of Multiple Sclerosis (MS). However, the pathogenic autoimmunity in MS, can be directed against several major target antigens, and therefore targeting pathogenic T-cells directed against a single target antigen is unlikely to be effective. To overcome this multiplicity and the potential complexity of pathogenic autoreactivities in MS, we have put forward the concept of concomitant multi-antigen/multi-epitope targeting as, a conceivably more effective approach to immunotherapy of MS. We constructed an (Experimental Autoimmune Encephalomeylitis (EAE)/MS-related synthetic human Target Autoantigen Gene (MS-shMultiTAG) designed to encode in tandem only EAE/MS related epitopes of all known encephalitogenic proteins. The MS-related protein product (designated Y-MSPc) was immunofunctional and upon tolerogenic administration, it effectively suppressed and reversed EAE induced by a single encephalitogenic protein. Furthermore, Y-MSPc also fully abrogated the development of "complex EAE" induced by a mixture of five encephalitogenic T-cell lines, each specific for a different encephalitogenic epitope of MBP, MOG, PLP, MOBP and OSP. Strikingly, Y-MSPc was consistently more effective than treatment with the single disease-specific peptide or with the peptide cocktail, both in suppressing the development of "classical" or "complex" EAE and in ameliorating ongoing disease. Overall, the modulation of EAE by Y-MSPc was associated with anergizing the pathogenic autoreactive T-cells, downregulation of Th1/Th17 cytokine secretion and upregulation of TGF-β secretion. Moreover, we show that both suppression and treatment of ongoing EAE by tolerogenic administration of Y-MSPc is associated also with a remarkable increase in a unique subset of dendritic-cells (DCs), CD11c+CD11b+Gr1+-myeloid derived DCs in both spleen and CNS of treated mice. These DCs, which are with strong immunoregulatory characteristics and are functional in down-modulation of MS-like-disease displayed increased production of IL-4, IL-10 and TGF-β and low IL-12. Functionally, these myeloid DCs suppress the in-vitro proliferation of myelin-specific T-cells and more importantly, the cells were functional in-vivo, as their adoptive transfer into EAE induced mice resulted in strong suppression of the disease, associated with a remarkable induction of CD4 + FoxP3+ regulatory cells. These results, which highlight the efficacy of "multi-epitope-targeting" agent in induction of functional regulatory CD11c+CD11b+Gr1+myeloid DCs, further indicate the potential role of these DCs in maintaining peripheral tolerance and their involvement in downregulation of MS-like-disease.

Association of CD8(+) T lymphocyte repertoire spreading with the severity of DRESS syndrome

T-cell receptor (TCR)-mediated cross-recognition is a major mechanism in the pathogenesis of drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome. However, the characteristics of the TCR repertoire and the clinical significance of repertoire reformation throughout the course of DRESS are unknown. Here, we isolated CD4(+) and CD8(+) T-cells from peripheral blood of 8 DRESS patients at 10-day intervals and, sequenced CDR3-regions of the TCRB chain by high-throughput sequencing to analyze the dynamic reformation in the T-cell repertoire hierarchy. Compared with healthy donors, T-cell expanded in peripheral repertoires from DRESS patient. The extent of fluctuation of dominant CD8(+) T-cell clones, but not of CD4(+) counterparts, correlated positively with the clinical severity and helped classify the enrolled subjects into "fluctuant" and "flat" repertoire groups. The anti-herpesvirus response, which was measured using anti-EBV/HHV antibodies, and the proportion of the homologous CD8(+) EBV-specific clonotypes, in the "fluctuant" group was substantial higher than that in the "flat" group. Furthermore, autoimmune sequelae were observed in a cured "fluctuant" patient. Collectively, the clinical relevance of the fluctuant CD8(+) T-cell repertoires supports the notion that herpes virus-mediated continuously de novo priming of newly pathogenic CD8(+) T-cell clones is an alternate mechanism responsible for the pathogenicity of DRESS.

From classic to spontaneous and humanized models of multiple sclerosis: impact on understanding pathogenesis and drug development

Multiple sclerosis (MS), a demyelinating disease of the central nervous system (CNS), presents as a complex disease with variable clinical and pathological manifestations, involving different pathogenic pathways. Animal models, particularly experimental autoimmune encephalomyelitis (EAE), have been key to deciphering the pathophysiology of MS, although no single model can recapitulate the complexity and diversity of MS, or can, to date, integrate the diverse pathogenic pathways. Since the first EAE model was introduced decades ago, multiple classic (induced), spontaneous, and humanized EAE models have been developed, each recapitulating particular aspects of MS pathogenesis. The advances in technologies of genetic ablation and transgenesis in mice of C57BL/6J background and the development of myelin-oligodendrocyte glycoprotein (MOG)-induced EAE in C57BL/6J mice yielded several spontaneous and humanized EAE models, and resulted in a plethora of EAE models in which the role of specific genes or cell populations could be precisely interrogated, towards modeling specific pathways of MS pathogenesis/regulation in MS. Collectively, the numerous studies on the different EAE models contributed immensely to our basic understanding of cellular and molecular pathways in MS pathogenesis as well as to the development of therapeutic agents: several drugs available today as disease modifying treatments were developed from direct studies on EAE models, and many others were tested or validated in EAE. In this review, we discuss the contribution of major classic, spontaneous, and humanized EAE models to our understanding of MS pathophysiology and to insights leading to devising current and future therapies for this disease.

Genetics of primary progressive multiple sclerosis

Multiple sclerosis (MS) patients are classified as either having relapsing onset or progressive onset disease, also known as primary progressive MS (PPMS). Relative to relapsing onset patients, PPMS patients are older at disease onset, are equally likely to be men or women, and have more rapid accumulation of disability that does not respond well to treatments used in relapsing onset MS. Although estimates vary, 5-15% of all MS patients have a PPMS disease course. Genetic variance is a proposed determinant of MS disease course. If distinct genes associated with PPMS were identified study of these genes might lead to an understanding of the biology underlying disease progression and neural degeneration that are the hallmarks of PPMS. These genes and their biological pathways might also represent therapeutic targets. This chapter systematically reviews the PPMS genetic literature. Despite the intuitively appealing notion that differences between PPMS and relapsing onset MS are due to genetics, definite differences associated with these phenotypes at the major histocompatibility complex or elsewhere in the genome have not been found. Recent large-scale genome wide screens identified multiple genes associated with MS susceptibility outside the MHC. The genetic variants identified thus far make only weak individual contributions to MS susceptibility. If the genetic effects that contribute to the differences between PPMS and relapsing MS are similar in magnitude to those that distinguish MS from healthy controls then, given the relative scarcity of the PPMS phenotype, very large datasets will be needed to identify PPMS associated genes. International collaborative efforts could provide the means to identify such genes. Alternately, it is possible that factors other than genetics underlie the differences between these clinical phenotypes.

'Multi-epitope-targeted' immune-specific therapy for a multiple sclerosis-like disease via engineered multi-epitope protein is superior to peptides

Antigen-induced peripheral tolerance is potentially one of the most efficient and specific therapeutic approaches for autoimmune diseases. Although highly effective in animal models, antigen-based strategies have not yet been translated into practicable human therapy, and several clinical trials using a single antigen or peptidic-epitope in multiple sclerosis (MS) yielded disappointing results. In these clinical trials, however, the apparent complexity and dynamics of the pathogenic autoimmunity associated with MS, which result from the multiplicity of potential target antigens and “epitope spread”, have not been sufficiently considered. Thus, targeting pathogenic T-cells reactive against a single antigen/epitope is unlikely to be sufficient; to be effective, immunospecific therapy to MS should logically neutralize concomitantly T-cells reactive against as many major target antigens/epitopes as possible. We investigated such “multi-epitope-targeting” approach in murine experimental autoimmune encephalomyelitis (EAE) associated with a single (“classical”) or multiple (“complex”) anti-myelin autoreactivities, using cocktail of different encephalitogenic peptides vis-a-vis artificial multi-epitope-protein (designated Y-MSPc) encompassing rationally selected MS-relevant epitopes of five major myelin antigens, as “multi-epitope-targeting” agents. Y-MSPc was superior to peptide(s) in concomitantly downregulating pathogenic T-cells reactive against multiple myelin antigens/epitopes, via inducing more effective, longer lasting peripheral regulatory mechanisms (cytokine shift, anergy, and Foxp3+ CTLA4+ regulatory T-cells). Y-MSPc was also consistently more effective than the disease-inducing single peptide or peptide cocktail, not only in suppressing the development of “classical” or “complex EAE” or ameliorating ongoing disease, but most importantly, in reversing chronic EAE. Overall, our data emphasize that a “multi-epitope-targeting” strategy is required for effective immune-specific therapy of organ-specific autoimmune diseases associated with complex and dynamic pathogenic autoimmunity, such as MS; our data further demonstrate that the “multi-epitope-targeting” approach to therapy is optimized through specifically designed multi-epitope-proteins, rather than myelin peptide cocktails, as “multi-epitope-targeting” agents. Such artificial multi-epitope proteins can be tailored to other organ-specific autoimmune diseases.

Urothelial antigen-specific CD4+ T cells function as direct effector cells and induce bladder autoimmune inflammation independent of CD8+ T cells

The role of CD4(+) T cells in bladder autoimmune inflammation has not been identified because of the lack of a proper animal model. We investigated CD4(+) T-cell responses to bladder urothelial ovalbumin (OVA), a model self-antigen (Ag), in transgenic URO-OVA mice. The expression of bladder urothelial OVA rendered mice unresponsive to OVA and resulted in quick clearance of Ag-specific CD4(+) T cells. Adoptive transfer of naive OVA-specific CD4(+) T cells led to exogenous T-cell proliferation, activation, and bladder infiltration but no inflammatory induction. In contrast, adoptive transfer of preactivated OVA-specific CD4(+) T cells induced bladder inflammation. Studies further demonstrated that CD4(+) T cells induced bladder inflammation in URO-OVA mice depleted of CD8(+) T cells or deficient in the recombinase activating gene-1 (Rag-1(-/-)). These results indicate that urothelial Ag-specific CD4(+) T cells can function as direct effector cells to induce bladder autoimmune inflammation independent of CD8(+) T cells.

A polymorphism in the HLA-DPB1 gene is associated with susceptibility to multiple sclerosis

We conducted an association study across the human leukocyte antigen (HLA) complex to identify loci associated with multiple sclerosis (MS). Comparing 1927 SNPs in 1618 MS cases and 3413 controls of European ancestry, we identified seven SNPs that were independently associated with MS conditional on the others (each P ≤ 4 x 10(-6)). All associations were significant in an independent replication cohort of 2212 cases and 2251 controls (P ≤ 0.001) and were highly significant in the combined dataset (P ≤ 6 x 10(-8)). The associated SNPs included proxies for HLA-DRB1*15:01 and HLA-DRB1*03:01, and SNPs in moderate linkage disequilibrium (LD) with HLA-A*02:01, HLA-DRB1*04:01 and HLA-DRB1*13:03. We also found a strong association with rs9277535 in the class II gene HLA-DPB1 (discovery set P = 9 x 10(-9), replication set P = 7 x 10(-4), combined P = 2 x 10(-10)). HLA-DPB1 is located centromeric of the more commonly typed class II genes HLA-DRB1, -DQA1 and -DQB1. It is separated from these genes by a recombination hotspot, and the association is not affected by conditioning on genotypes at DRB1, DQA1 and DQB1. Hence rs9277535 represents an independent MS-susceptibility locus of genome-wide significance. It is correlated with the HLA-DPB1*03:01 allele, which has been implicated previously in MS in smaller studies. Further genotyping in large datasets is required to confirm and resolve this association.

Clinical, pathological, and immunologic aspects of the multiple sclerosis model in common marmosets (Callithrix jacchus)

The efficacy of many new immunomodulatory therapies for multiple sclerosis (MS) patients has often been disappointing, reflecting our incomplete understanding of this enigmatic disease. There is a growing awareness that, at least in part, there may be limited applicability to the human disease of results obtained in the widely studied MS model experimental autoimmune encephalomyelitis in rodents. This review describes the experimental autoimmune encephalomyelitis model developed in a small neotropical primate, the common marmoset (Callithrix jacchus). The model has features including clinicopathologic correlation patterns, lesion heterogeneity, immunologic mechanisms, and disease markers that more closely mimic the human disease. Several unique features of experimental autoimmune encephalomyelitis in marmosets, together with their outbred nature and close genetic and immunologic similarities to humans, create an attractive experimental model for translational research into MS, particularly for the preclinical evaluation of new biologic therapeutic molecules that cannot be investigated in rodents because of their species specificity. Moreover, this model provides new insights into possible pathogenetic mechanisms in MS.

The importance of HLA-DPB1 in unrelated donor hematopoietic cell transplantation

Hematopoietic cell transplantation (HCT) from an HLA-A, HLA-B, HLA-C, HLA-DRB1, and HLA-DQB1 allele-matched unrelated donor is a well-recognized life-saving treatment modality for patients with hematologic disorders. The morbidity and mortality from clinically significant acute graft-versus-host disease (aGVHD) remains a limitation. The extent to which transplantation outcome may be improved with donor matching for HLA-DP is not well defined. The risks of aGVHD, relapse, and mortality associated with HLA-DPB1 allele mismatching were determined in 5929 patients who received a myeloablative HCT from an HLA-A-, HLA-B-, HLA-C-, HLA-DRB1-, and HLA-DQB1-matched or -mismatched donor. There was a statistically significantly higher risk of both grades 2 to 4 aGVHD (odds ratio [OR] = 1.33; P < .001) and grades 3 to 4 aGVHD (OR = 1.26; P < .001) after HCT from an HLA-DPB1-mismatched donor compared with a matched donor. The increased risk of aGVHD was accompanied by a statistically significantly decrease in disease relapse (hazard ratio [HR] = 0.82; P = .01). HLA-DPB1 functions as a classical transplantation antigen. The increased risk of GVHD associated with HLA-DPB1 mismatching is accompanied by a lower risk of relapse. Knowledge of the DPB1 matching status prior to transplantation will aid in more precise risk stratification for the individual patient.

Expression of HLA-DP0401 molecules for identification of DP0401 restricted antigen specific T cells

Human histocompatibility leukocyte antigen (HLA)-DPA1*0103/DPB1*0401 (DP0401) is the most common HLA class II molecule and is present in approximately 45% of the Caucasian population. In this study, soluble HLA-DP0401 molecules were expressed as "empty'' class II molecules in insect cells. Utilizing these soluble DP molecules and the Tetramer Guided Epitope Mapping (TGEM) approach, the influenza A Puerto Rico/8/34 matrix protein (MP) derived peptide MP(41-60) VLMEWLKTRPILSPLTKGIL and the Clostridium tetani Tetanus Toxin (TT) derived peptide TT(634-653) DKISDVSTIVPYIGPALNIV were identified as the DP0401 restricted MP and TT epitopes, respectively. In addition, T cells specific for the cancer testis antigen NY-ESO-1 and the breast/ovarian cancer over-expressing antigen Her-2/neu were detected in DP0401 subjects by DP0401 tetramers. The availability of HLA-DP0401 tetramers should facilitate the study of DP restricted T cell responses.

HLA-DPB1 matching status has significant implications for recipients of unrelated donor stem cell transplants

Studies in unrelated donor (UD) hematopoietic stem cell transplantations (HSCT) show an effect of the matching status of HLA-DPB1 on complications. We analyzed 423 UD-HSCT pairs. Most protocols included T-cell depletion (TCD). All pairs had high-resolution tissue typing performed for 6 HLA loci. Two hundred eighty-two pairs were matched at 10 of 10 alleles (29% were DPB1 matched). In 141 HLA-mismatched pairs, 28% were matched for DPB1. In the 10 of 10 matched pairs (n = 282), the 3-year probability of relapse was 61%. This was significantly higher in DPB1-matched pairs (74%) as compared with DPB1-mismatched pairs (56%) (log rank, P = .001). This finding persisted in multivariate analysis. In the group overall (n = 423), relapse was also significantly increased if DPB1 was matched (log rank; P < .001). These results were similar in chronic myeloid leukemia (CML; P < .001) and acute lymphoblastic leukemia (ALL; P = .013). In ALL, DPB1-matched pairs had a significantly worse overall survival (log rank; P = .025). Thus, in recipients of TCD UD-HSCT, a match for DPB1 is associated with a significantly increased risk of disease relapse, irrespective of the matching status for the other HLA molecules. It is possible that this effect is especially apparent following TCD transplantations and invites speculation about the function of DPB1 within the immune system.

Interaction of loci within the HLA region influences multiple sclerosis course in the Sardinian population

We examined the influence of alleles at the HLA loci, previously found to be associated with multiple sclerosis (MS) in Sardinia, on the clinical course of the disease in 835 relapsing (R) and 100 primary progressive (PP) patients. Multivariate analysis was carried out on predisposing 0301 or non-associated DPB1 alleles, susceptible or non-associated DRB1-DQB1 haplotypes, both predisposing and non-predisposing, and negatively and non-negatively associated D6S1683 alleles, taking interaction between them into account. Intra-patient analysis showed that the presence of the susceptible or protective D6S1683 allele interacting with predisposing DP 0301 modulated risk of PP disease. These findings suggest that a locus telomeric to HLA class I exerts an effect on alleles at the DPB1 locus in modulating disease course.

Immunology of multiple sclerosis

Multiple sclerosis (MS) develops in young adults with a complex predisposing genetic trait and probably requires an inciting environmental insult such as a viral infection to trigger the disease. The activation of CD4+ autoreactive T cells and their differentiation into a Th1 phenotype are a crucial events in the initial steps, and these cells are probably also important players in the long-term evolution of the disease. Damage of the target tissue, the central nervous system, is, however, most likely mediated by other components of the immune system, such as antibodies, complement, CD8+ T cells, and factors produced by innate immune cells. Perturbations in immunomodulatory networks that include Th2 cells, regulatory CD4+ T cells, NK cells, and others may in part be responsible for the relapsing-remitting or chronic progressive nature of the disease. However, an important paradigmatic shift in the study of MS has occurred in the past decade. It is now clear that MS is not just a disease of the immune system, but that factors contributed by the central nervous system are equally important and must be considered in the future.

Native myelin oligodendrocyte glycoprotein promotes severe chronic neurological disease and demyelination in Biozzi ABH mice

Myelin oligodendrocyte glycoprotein (MOG) is a powerful encephalitogen for experimental autoimmune demyelination. However, the use of MOG peptides or recombinant proteins representing part of the protein fails to fully address the possible pathogenic role of the full-length myelin-derived protein expressing post-translational modifications. Immunization of mice with central nervous system tissues from wild-type (WT) and MOG-deficient (MOG(-/-)) mice demonstrates that MOG in myelin is necessary for the development of chronic demyelinating experimental autoimmune encephalomyelitis (EAE) in mice. While immunization with WT spinal cord homogenate (SCH) resulted in a progressive EAE phenotype, MOG(-/-) SCH induced a mild self-limiting acute disease. Following acute EAE with MOG(-/-) SCH, mice developed T cell responses to recombinant mouse MOG (rmMOG), indicating that MOG released from myelin is antigenic; however, the lack of chronic disease indicates that such responses were not pathogenic. Chronic demyelinating EAE was observed when MOG(-/-) SCH was reconstituted with a dose of rmMOG comparable to MOG in myelin (2.5% of total white matter-derived protein). These data reveal that while immunization with the full-length post-translational modified form of MOG in myelin promotes the development of a more chronic autoimmune demyelinating neurological disease, MOG (and/or other myelin proteins) released from myelin during ongoing disease do not induce destructive autoimmunity.

Candidate epitope identification using peptide property models: application to cancer immunotherapy

Peptides derived from pathogens or tumors are selectively presented by the major histocompatibility complex proteins (MHC) to the T lymphocytes. Antigenic peptide-MHC complexes on the cell surface are specifically recognized by T cells and, in conjunction with co-factor interactions, can activate the T cells to initiate the necessary immune response against the target cells. Peptides that are capable of binding to multiple MHC molecules are potential T cell epitopes for diverse human populations that may be useful in vaccine design. Bioinformatical approaches to predict MHC binding peptides can facilitate the resource-consuming effort of T cell epitope identification. We describe a new method for predicting MHC binding based on peptide property models constructed using biophysical parameters of the constituent amino acids and a training set of known binders. The models can be applied to development of anti-tumor vaccines by scanning proteins over-expressed in cancer cells for peptides that bind to a variety of MHC molecules. The complete algorithm is described and illustrated in the context of identifying candidate T cell epitopes for melanomas and breast cancers. We analyzed MART-1, S-100, MBP, and CD63 for melanoma and p53, MUC1, cyclin B1, HER-2/neu, and CEA for breast cancer. In general, proteins over-expressed in cancer cells may be identified using DNA microarray expression profiling. Comparisons of model predictions with available experimental data were assessed. The candidate epitopes identified by such a computational approach must be evaluated experimentally but the approach can provide an efficient and focused strategy for anti-cancer immunotherapy development.

Early-stage multiple sclerosis : what are the treatment options?

Converging evidence from recent years indicates that the current attitude to the use of immunomodulatory drugs in the treatment of multiple sclerosis (MS) may be too conservative. This evidence originates from studies of the pathophysiology and pathology of MS, magnetic resonance imaging (MRI) studies and clinical trials. Several studies have shown that antigen spreading and propagation of self-recognition seem to occur during the clinical progression of MS. The immunopathology may change during the course of disease. Primary selective demyelination can be followed by a secondary oligodendrocyte loss and remyelination becomes less effective. MRI studies have shown that patients with clinically isolated syndromes, who at presentation have more than a few brain lesions on MRI, have a high risk of disease progression over a period of 5-10 years. The most direct evidence comes from two placebo-controlled trials of interferon-beta in very early MS. A delay in time to conversion to clinically definite MS and a significant decrease in MRI activity support an early stage treatment strategy. Taken together, the evidence indicates that treatment with immunomodulatory therapy should be started at an early stage in patients with a high-risk profile for further disease activity, although this may result in over-treatment of a small number of patients. However, further prolonged studies are needed to investigate the long-term benefit of early-stage treatment in MS.

Theiler's virus infection: a model for multiple sclerosis

Both genetic background and environmental factors, very probably viruses, appear to play a role in the etiology of multiple sclerosis (MS). Lessons from viral experimental models suggest that many different viruses may trigger inflammatory demyelinating diseases resembling MS. Theiler's virus, a picornavirus, induces in susceptible strains of mice early acute disease resembling encephalomyelitis followed by late chronic demyelinating disease, which is one of the best, if not the best, animal model for MS. During early acute disease the virus replicates in gray matter of the central nervous system but is eliminated to very low titers 2 weeks postinfection. Late chronic demyelinating disease becomes clinically apparent approximately 2 weeks later and is characterized by extensive demyelinating lesions and mononuclear cell infiltrates, progressive spinal cord atrophy, and axonal loss. Myelin damage is immunologically mediated, but it is not clear whether it is due to molecular mimicry or epitope spreading. Cytokines, nitric oxide/reactive nitrogen species, and costimulatory molecules are involved in the pathogenesis of both diseases. Close similarities between Theiler's virus-induced demyelinating disease in mice and MS in humans, include the following: major histocompatibility complex-dependent susceptibility; substantial similarities in neuropathology, including axonal damage and remyelination; and paucity of T-cell apoptosis in demyelinating disease. Both diseases are immunologically mediated. These common features emphasize the close similarities of Theiler's virus-induced demyelinating disease in mice and MS in humans.

Non-invasive measurement of brain damage in a primate model of multiple sclerosis

Early recognition of whether a product has potential as a new therapy for treating multiple sclerosis (MS) relies upon the quality of the animal models used in the preclinical trials. The promising effects of new treatments in rodent models of experimental autoimmune encephalomyelitis (EAE) have rarely been reproduced in patients suffering from MS. EAE in outbred marmoset monkeys, Callithrix jacchus, is a valid new model, and might provide an experimental link between EAE in rodent models and human MS. Using magnetic resonance imaging techniques similar to those used in patients suffering from MS pathological abnormalities in the brain, white matter of the animal can be visualized and quantified. Moreover, NMR spectroscopy, in combination with pattern recognition, offers an advanced uroscopic technique for the identification of biomarkers of inflammatory demyelination.

Decreased expression of the CD3zeta chain in T cells infiltrating the synovial membrane of patients with osteoarthritis

Osteoarthritis (OA) is a heterogeneous disease which rheumatologists consider to be noninflammatory. However, recent studies suggest that, at least in certain patients, OA is an inflammatory disease and that patients often exhibit inflammatory infiltrates in the synovial membranes (SMs) of macrophages and activated T cells expressing proinflammatory cytokines. We report here that the expression of CD3zeta is significantly decreased in T cells infiltrating the SMs of patients with OA. The CD3zeta chain is involved in the T-cell signal transduction cascade, which is initiated by the engagement of the T-cell antigen receptor and which culminates in T-cell activation. Double immunofluorescence of single-cell suspensions derived from the SMs from nine patients with OA revealed significantly increased proportions of CD3epsilon-positive (CD3epsilon+) cells compared with the proportions of CD3zeta-positive (CD3zeta+) T cells (means +/- standard errors of the means, 80.48% +/- 3.92% and 69.02% +/- 6.51%, respectively; P = 0.0096), whereas there were no differences in the proportions of these cells in peripheral blood mononuclear cells (PBMCs) from healthy donors (94.73% +/- 1.39% and 93.79% +/- 1.08%, respectively; not significant). The CD3zeta+ cell/CD3epsilon+ cell ratio was also significantly decreased for T cells from the SMs of patients with OA compared with that for T cells from the PBMCs of healthy donors (0.84 +/- 0.17 and 0.99 +/- 0.01, respectively; P = 0.0302). The proportions of CD3epsilon+ CD3zeta+ cells were lower in the SMs of patients with OA than in the PBMCs of healthy donors (65.04% +/- 6.7% and 90.81% +/- 1.99%, respectively; P = 0.0047). Substantial proportions (about 15%) of CD3epsilon+ CD3zeta-negative (CD3zeta-) and CD3epsilon-negative (CD3epsilon-) CD3zeta- cells were found in the SMs of patients with OA. Amplification of the CD3zeta and CD3delta transcripts from the SMs of patients with OA by reverse transcriptase PCR consistently exhibited stronger bands for CD3delta cDNA than for CD3zeta cDNA The CD3zeta/CD3delta transcript ratio in the SMs of patients with OA was significantly lower than that in PBMCs from healthy controls (P < 0.0001). These results were confirmed by competitive MIMIC PCR. Immunoreactivities for the CD3zeta protein were detected in the SMs of 10 of 19 patients with OA, and they were of various intensities, whereas SMs from all patients were CD3epsilon+ (P = 0.0023). The decreased expression of the CD3zeta transcript and protein in T cells from the SMs of patients with OA relative to that of the CD3epsilon transcript is suggestive of chronic T-cell stimulation and supports the concept of T-cell involvement in OA.

The degree of matching at HLA-DPB1 predicts for acute graft-versus-host disease and disease relapse following haematopoietic stem cell transplantation

The importance of matching for HLA-DPB1 in unrelated donor haematopoietic stem cell (HSC) transplantation is little understood. Most transplant centres do not, currently, prospectively match for DPB1, but emerging data show that DPB1 matching does play a role in determining outcome. We studied the impact of HLA-DPB1 matching on outcome in 143 recipients of T-cell depletion transplants, who matched with their respective unrelated donors (allelic level) at HLA-A, -B, -C, -DRB1 and -DQB1. Of those matched at DPB1, 47.2% (17/36) developed acute graft-versus-host disease (aGvHD) as compared to 66.3% (55/83) of those who were mismatched. This led to a 19.1% (95% CI 0.1-38.3%) increase in the chance of developing aGvHD in mismatched patients (P=0.049). Relapse of the original disease occurred in 51 recipients; 23 of 37 (62%) matched at both DPB1 alleles, 28 of 82 (34%) were mismatched at one or two DPB1 alleles. Thus, there was a significantly higher relapse rate (P=0.0011) in transplant recipients who matched at both DPB1 alleles. In conclusion, a donor/recipient DPB1 match was associated with a significantly lower incidence of aGvHD and a significantly higher incidence of disease relapse. This study provides further evidence for an immunogenic role of HLA-DPB1 in HSC transplants.

Multiple sclerosis complexity in selected populations: the challenge of Sardinia, insular Italy

Several lines of evidence indicate a genetic contribution to multiple sclerosis (MS) both in terms of predisposition to the disease and of immunological mechanisms which are known to play crucial roles in MS pathogenesis. The presence of high- and low-risk areas for MS in neighbouring regions supports the theory that MS predisposition is influenced by a complex interaction of genetic and environmental factors. Therefore, the use of genetically homogeneous and geographically isolated populations becomes an increasing requirement to reduce biasing biological variables. Sardinians fulfil these conditions well because of their different phylogeny from Europeans and the unique selective pressures which shaped their genome. Sardinians display amongst the highest MS prevalence rates world-wide and increasing MS incidence rates over time. Also, MS in Sardinia is linked to distinct human leucocyte antigen (HLA) alleles and associated to different patterns of cytokine production from lymphoid cells of different HLA subtypes. In this context, recent findings and future perspectives on the peculiarities of Sardinian MS concerning genetic, immunological and epidemiological aspects are presented. So far, our results indicate that variations at the level of territorial distribution and HLA-association are present which render MS heterogeneous even in this ethnically homogeneous population.

Development of autoimmunity after skin graft rejection via an indirect alloresponse

BACKGROUND

T cell allorecognition occurs through direct contact with donor peptide: MHC complexes on graft cells and through indirect recognition of donor-derived determinants expressed by recipient MHC molecules. As both indirect allorecognition and autoantigen recognition are self-restricted, we hypothesized that chronic activation of indirectly primed T cells might result in determinant spreading to involve autoantigens, analogous to that which occurs during chronic autoimmune diseases.

METHODS

We placed C57BL/6 MHC II knockout (B6 II-/-) skin grafts onto BALB/c SCID mice reconstituted with wild-type (WT) CD4+ T cells. Under these conditions the CD4+ cells could not recognize any antigen on the graft, but could respond through the indirect pathway. CD4+ cell-mediated rejection of WT B6 skin was studied to determine if autoreactivity was induced after direct allorecognition. Recall immune responses against donor- and self-stimulator cells were determined by ELISPOT and animals were tested for their ability to reject second isografts.

RESULTS

WT allografts were rejected by day 14 although B6 II-/- grafts underwent delayed rejection over 4-5 weeks. CD4+ cells reisolated from the recipients of the MHC II-/- grafts, but not from the recipients of WT grafts, vigorously produced interferon-gamma and interleukin-2 in response to self, BALB/c stimulators. These autoreactive CD4+ T cells mediated rejection of a second isogenic BALB/c skin graft, demonstrating that the autoimmune response was pathogenic.

CONCLUSION

Autoreactivity can develop after transplant rejection via the indirect pathway. Although the direct alloresponse is likely to be the driving force in acute graft rejection, posttransplantation induced autoimmune responses may be important elements of delayed or chronic rejection.

Identification of a new HLA-DPB1 allele,HLA-DPB1*9001

During routine typing of a potential bone marrow donor, a new HLA DPB1 allele was identified. The new allele, officially named HLA DPB1*9001, differs from HLA DPB1*01011 in the second hypervariable region, where a single nucleotide substitution in position 191 changes the codon 35 from TAC to TTC with a predicted amino acid change from Tyr to Phe.

The major histocompatibility complex influences the ethiopathogenesis of MS-like disease in primates at multiple levels

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease primarily affecting the central nervous system. Of the many candidate polymorphic major histocompatibility complex (MHC) and non-MHC genes contributing to disease susceptibility, including those encoding effector (cytokines and chemokines) or receptor molecules within the immune system (MHC, TCR, Ig or FcR), human leukocyte antigen (HLA) class II genes have the most significant influence. In this article we put forward the hypothesis that the influence of HLA genes on the risk to develop MS is actually the sum of multiple antigen presenting cell (APC) and T-cell interactions involving HLA class I and class II molecules. This article will also discuss that, because of the genetic and immunologic similarity to humans, autoimmune models of MS in non-human primates are the experimental models "par excellence" to test this hypothesis.

Differences between T-cell reactivities to major myelin protein-derived peptides in opticospinal and conventional forms of multiple sclerosis and healthy controls

In Japanese, susceptibility to the conventional form of multiple sclerosis (C-MS) is associated with the HLA-DRB1*1501-DRB5*0101 haplotype while susceptibility to the opticospinal form of MS (OS-MS) is associated with HLA-DPA1*0202-DPB1*0501. To clarify the characteristics of T cells autoreactive to myelin proteins in each MS subtype, we established T-cell lines reactive to such myelin antigens as myelin basic protein (MBP), proteolipid protein (PLP) and myelin oligodendrocyte glycoprotein (MOG) from 5 of 10 OS-MS patients, 6 of 11 C-MS patients and 7 of 13 healthy controls (HCs), and T-cell epitopes and their restriction molecules were determined. We found that (a) intermolecular epitope spreading was found to be significantly more frequent in MS patients than in HCs (P=0.0128), (b) intramolecular epitope spreading also tended to occur more frequently in MS patients than in HCs (P=0.0584), (c) in OS-MS, HLA-DR-restricted and MOG-autoreactive T cells were more frequently established as compared with those reactive to MBP or PLP epitopes and (d) in C-MS, HLA-DQ-restricted and PLP-autoreactive T cells dominated those autoreactive to MBP or MOG epitopes. A DPB1*0501-restricted MBP-reactive T-cell clone from a patient with OS-MS provided evidence that the first HLA class II anchor amino acid of peptide bound to disease-susceptible DP5 molecule was distinct from that for the DR2 molecule. Taken together, these differences in specificities of myelin-autoreactive T cells between C-MS and OS-MS as well as the difference in the anchor motif of the binding peptides between each MS subtype-susceptible HLA class II molecule may contribute to the development of distinct clinical phenotypes.

The biological significance of HLA-DP gene variation in haematopoietic cell transplantation

Although it has been over 25 years since HLA-DP was mapped to the major histocompatibility complex (MHC), its biological functions remain ill-defined. We sought to test the hypothesis that HLA-DP functions in a manner similar to that of other class II genes by measuring the risk of clinically severe grades III-IV acute graft-vs.-host disease (GVHD) associated with recipient HLA-DP disparity after haematopoietic cell transplantation. HLA-DPB1 exon 2 was sequenced in 205 patients who underwent transplantation from HLA-A, -B, -C, -DRB1 and -DQB1 allele-matched unrelated donors. HLA-DPB1 mismatched recipients experienced a significantly increased risk of acute GVHD compared with HLA-DP-identical transplants. Patients who were mismatched for a single HLA-DPB1 allele had an odds ratio (OR) of 1.0 (0.5, 2.2; P = 0.99) and patients who were mismatched for two alleles had an OR of 2.2 (1.0, 4.9; P = 0.06) for developing acute GVHD. Compared with matched and single-allele mismatched transplants, patients who were mismatched for two DPB1 alleles had an OR of 2.2 (1.2, 4.1; P = 0.01). HLA-DP plays an important role in the alloimmune response. A threshold effect of multiple HLA-DP disparities is evident in determining the risk of acute GVHD after haematopoietic cell transplantation from unrelated donors.

Residual public repertoires to self

The consensus view about the constitution of the T cell receptor repertoire has shifted greatly even during this decade. Although the discovery of autoimmunity in the fifties had clearly shown that a repertoire must exist directed against self antigens, the extent of this repertoire was not fully appreciated. In our work we have tried to elucidate the nature of the antigenic specificities against which this self-directed repertoire is directed. The non-tolerized (residual) self-directed repertoire is a direct consequence of the hierarchy of antigenic determinant display, and is the most important influence in the organism's choice of which T cells to delete. Certain determinants remain "silent" and are neither displayed in the thymus nor in the periphery: these are a heterogeneous group which are invisible to T cells for a variety of reasons. One reason relates to the processing and presentation of determinants, and a second derives from the nature of the T cell receptor (TcR) and the avidity of the T cell for its target specificity.

Both the HLA-CPB1 and -DRB1 alleles correlate with risk for multiple sclerosis in Japanese: clinical phenotypes and gender as important factors

The purpose of this study was to clarify the association of HLA-DRB1 and -DPB1 alleles with multiple sclerosis (MS) in Japanese, to determine whether optico-spinal MS (OS-MS) and conventional MS are immunogenetically distinct, and to verify the role of gender difference in HLA associations of MS. We studied HLA-DRB1 and -DPB1 polymorphisms in 166 Japanese patients with MS. Forty-seven patients were classified as having the optico-spinal MS (OS-MS) and 119 as having conventional MS. A lack of DPB1*0301 and a higher frequency of DPB1*0501 compared with controls (corrected P<0.0074; odds ratio=9.48) were found in OS-MS. By contrast, we found for the first time an association of DPB1*0301 with conventional MS in Japanese (corrected P=0.0444; odds ratio=3.28). Logistic analysis, adjusted for sex and age, revealed independent associations of DPB1*0301 (P=0.0004, adjusted odds ratio (aOR)=4.70), DPB1*0501 (P=0.0081, aOR= 2.50) and DRB1*1501 (P=0.0252, aOR=2.21) with conventional MS. However, the frequencies of DRB1*1501 and DPB1*0501 in male patients with conventional MS were equal to those in male controls while the DPB1*0301 frequency was increased in both male and female patients. We did not find any association of these HLA alleles with disease course and severity. In conclusion, OS-MS is a DPB1*0501-associated distinct subtype of MS, and DPB1*0301 is the most strongly associated allele with conventional MS in Japanese. In addition, gender plays an important role in HLA association with MS.

Regression and spreading of self-recognition during the development of autoimmune demyelinating disease

The autoimmune T cell repertoire in experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS) is characterized by CD4(+)T cells of the Th1 phenotype that recognize peptide determinants of central nervous system (CNS) myelin proteins in an MHC class II-restricted manner. Our recent studies and those performed by others have shown that progression to chronicity in EAE and MS is accompanied by a broadening of the T cell repertoire with time. This acquired neo-autoreactivity is commonly referred to as epitope spreading and is presumably the result of endogenous priming to new self-determinants during the CNS inflammation that accompanies disease onset and relapse. In the present study we extend our earlier observations by showing that disease progression in both EAE and MS is accompanied by two concurrent events, viz. (1) the spontaneous regression of the primary established autoimmune repertoire associated with disease onset, and (2) the emergence of the epitope spreading cascade associated with disease progression. Our data show that disease initiation and disease progression in both EAE and MS are typically associated with distinctly different autoimmune T cell repertoires. Our data support the view that the natural development of self-recognition during autoimmune disease may best be understood when considered in the temporal context of an 'epitope du jour' and 'moving target' perspective.

Spontaneous regression of primary autoreactivity during chronic progression of experimental autoimmune encephalomyelitis and multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is a widely used animal model for multiple sclerosis (MS). EAE is typically initiated by CD4(+) T helper cell type 1 (Th1) autoreactivity directed against a single priming immunodominant myelin peptide determinant. Recent studies have shown that clinical progression of EAE involves the accumulation of neo-autoreactivity, commonly referred to as epitope spreading, directed against peptide determinants not involved in the priming process. This study directly addresses the relative roles of primary autoreactivity and secondary epitope spreading in the progression of both EAE and MS. To this end we serially evaluated the development of several epitope-spreading cascades in SWXJ mice primed with distinctly different encephalitogenic determinants of myelin proteolipid protein. In a series of analogous experiments, we examined the development of epitope spreading in patients with isolated monosymptomatic demyelinating syndrome as their disease progressed to clinically definite MS. Our results indicate that in both EAE and MS, primary proliferative autoreactivity associated with onset of clinical disease invariably regresses with time and is often undetectable during periods of disease progression. In contrast, the emergence of sustained secondary autoreactivity to spreading determinants is consistently associated with disease progression in both EAE and MS. Our results indicate that chronic progression of EAE and MS involves a shifting of autoreactivity from primary initiating self-determinants to defined cascades of secondary determinants that sustain the self-recognition process during disease progression.

The epitope spreading cascade during progression of experimental autoimmune encephalomyelitis and multiple sclerosis

We have made the following observations regarding self-recognition during the development and progression of murine experimental autoimmune encephalomyelitis (EAE) and human multiple sclerosis (MS): 1) chronic progression of EAE is accompanied by a sequential, predictable cascade of neo-autoreactivity, commonly referred to as epitope spreading, presumably caused by endogenous self-priming during autoimmune-mediated tissue damage; 2) there is an invariant relationship between the progression of EAE and the emergence of epitope spreading; 3) progression of EAE can be inhibited by the induction of antigen-specific tolerance to spreading determinants after onset of initial neurologic symptoms; 4) CD4+ Th 1 cells responding to spreading determinants are autonomously encephalitogenic; 5) epitope spreading occurs during the development of MS and in some cases involves HLA-DP class II-restricted self-recognition; and 6) progression of both EAE and MS is accompanied by the decline of primary T-cell autoreactivity associated with disease onset and by the concurrent emergence of the epitope spreading cascade. Our studies directly challenge the traditional view that EAE and MS are initiated and maintained by autoreactivity directed against a single predominant myelin protein or determinant. Our results indicate that progression of EAE and MS involves a shifting of T-cell autoreactivity from primary initiating self-determinants to defined cascades of secondary determinants that sustain the inflammatory self-recognition process during disease progression.