Visualization of myelin basic protein (MBP) T cell epitopes in multiple sclerosis lesions using a monoclonal antibody specific for the human histocompatibility leukocyte antigen (HLA)-DR2-MBP 85-99 complex

HLA-transgenic mouse models to study autoimmune central nervous system diseases

It is known that certain human leukocyte antigen (HLA) genes are associated with autoimmune central nervous system (CNS) diseases, such as multiple sclerosis (MS), but their exact role in disease susceptibility and etiopathogenesis remains unclear. The best studied HLA-associated autoimmune CNS disease is MS, and thus will be the primary focus of this review. Other HLA-associated autoimmune CNS diseases, such as autoimmune encephalitis and neuromyelitis optica will be discussed. The lack of animal models to accurately capture the complex human autoimmune response remains a major challenge. HLA transgenic (tg) mice provide researchers with powerful tools to investigate the underlying mechanisms promoting susceptibility and progression of HLA-associated autoimmune CNS diseases, as well as for elucidating the myelin epitopes potentially targeted by T cells in autoimmune disease patients. We will discuss the potential role(s) of autoimmune disease-associated HLA alleles in autoimmune CNS diseases and highlight information provided by studies using HLA tg mice to investigate the underlying pathological mechanisms and opportunities to use these models for development of novel therapies.

Antigen-specific T cells and autoimmunity

Autoimmune diseases (ADs) showcase the intricate balance between the immune system's protective functions and its potential for self-inflicted damage. These disorders arise from the immune system's erroneous targeting of the body's tissues, resulting in damage and disease. The ability of T cells to distinguish between self and non-self-antigens is pivotal to averting autoimmune reactions. Perturbations in this process contribute to AD development. Autoreactive T cells that elude thymic elimination are activated by mimics of self-antigens or are erroneously activated by self-antigens can trigger autoimmune responses. Various mechanisms, including molecular mimicry and bystander activation, contribute to AD initiation, with specific triggers and processes varying across the different ADs. In addition, the formation of neo-epitopes could also be implicated in the emergence of autoreactivity. The specificity of T cell responses centers on the antigen recognition sequences expressed by T cell receptors (TCRs), which recognize peptide fragments displayed by major histocompatibility complex (MHC) molecules. The assortment of TCR gene combinations yields a diverse array of T cell populations, each with distinct affinities for self and non-self antigens. However, new evidence challenges the traditional notion that clonal expansion solely steers the selection of higher-affinity T cells. Lower-affinity T cells also play a substantial role, prompting the "two-hit" hypothesis. High-affinity T cells incite initial responses, while their lower-affinity counterparts perpetuate autoimmunity. Precision treatments that target antigen-specific T cells hold promise for avoiding widespread immunosuppression. Nevertheless, detection of such antigen-specific T cells remains a challenge, and multiple technologies have been developed with different sensitivities while still harboring several drawbacks. In addition, elements such as human leukocyte antigen (HLA) haplotypes and validation through animal models are pivotal for advancing these strategies. In brief, this review delves into the intricate mechanisms contributing to ADs, accentuating the pivotal role(s) of antigen-specific T cells in steering immune responses and disease progression, as well as the novel strategies for the identification of antigen-specific cells and their possible future use in humans. Grasping the mechanisms behind ADs paves the way for targeted therapeutic interventions, potentially enhancing treatment choices while minimizing the risk of systemic immunosuppression.

Macrophages and HLA-Class II Alleles in Multiple Sclerosis: Insights in Therapeutic Dynamics

Antigen presentation is a crucial mechanism that drives the T cell-mediated immune response and the development of Multiple Sclerosis (MS). Genetic alterations within the highly variable Major Histocompatibility Complex Class II (MHC II) have been proven to result in significant changes in the molecular basis of antigen presentation and the clinical course of patients with both Adult-Onset MS (AOMS) and Pediatric-Onset MS (POMS). Among the numerous polymorphisms of the Human Leucocyte Antigens (HLA), within MHC II complex, HLA-DRB1*15:01 has been labeled, in Caucasian ethnic groups, as a high-risk allele for MS due to the ability of its structure to increase affinity to Myelin Basic Protein (MBP) epitopes. This characteristic, among others, in the context of the trimolecular complex or immunological synapsis, provides the foundation for autoimmunity triggered by environmental or endogenous factors. As with all professional antigen presenting cells, macrophages are characterized by the expression of MHC II and are often implicated in the formation of MS lesions. Increased presence of M1 macrophages in MS patients has been associated both with progression and onset of the disease, each involving separate but similar mechanisms. In this critical narrative review, we focus on macrophages, discussing how HLA genetic alterations can promote dysregulation of this population's homeostasis in the periphery and the Central Nervous System (CNS). We also explore the potential interconnection in observed pathological macrophage mechanisms and the function of the diverse structure of HLA alleles in neurodegenerative CNS, seen in MS, by comparing available clinical with molecular data through the prism of HLA-immunogenetics. Finally, we discuss available and experimental pharmacological approaches for MS targeting the trimolecular complex that are based on cell phenotype modulation and HLA genotype involvement and try to reveal fertile ground for the potential development of novel drugs.

Citrullination of myelin basic protein induces a Th17-cell response in healthy individuals and enhances the presentation of MBP85-99 in patients with multiple sclerosis

The post-translational modification citrullination has been proposed to play a role in the pathogenesis of multiple sclerosis (MS). Myelin basic protein (MBP) is a candidate autoantigen which is citrullinated to a minor extent under physiological conditions and hypercitrullinated in MS. We examined immune cell responses elicited by hypercitrullinated MBP (citMBP) in cultures of mononuclear cells from 18 patients with MS and 42 healthy donors (HDs). The immunodominant peptide of MBP, MBP85-99, containing citrulline in position 99, outcompeted the binding of native MBP85-99 to HLA-DR15, which is strongly linked to MS. Moreover, using the monoclonal antibody MK16 as probe, we observed that B cells and monocytes from HLA-DR15+ patients with MS presented MBP85-99 more efficiently after challenge with citMBP than with native MBP. Both citMBP and native MBP induced proliferation of CD4+ T cells from patients with MS as well as TNF-α production by their B cells and CD4+ T cells, and citrullination of MBP tended to enhance TNF-α secretion by CD4+ T cells from HLA-DR15+ patients. Unlike native MBP, citMBP induced differentiation into Th17 cells in cultures from HDs, while neither form of MBP induced Th17-cell differentiation in cultures from patients with MS. These data suggest a role for citrullination in the breach of tolerance to MBP in healthy individuals and in maintenance of the autoimmune response to MBP in patients with MS.

Myelin Basic Protein in Oligodendrocyte-Derived Extracellular Vesicles as a Diagnostic and Prognostic Biomarker in Multiple Sclerosis: A Pilot Study

Approximately 15% of multiple sclerosis (MS) patients develop a progressive form of disease from onset; this condition (primary progressive-PP) MS is difficult to diagnose and treat, and is associated with a poor prognosis. Extracellular vesicles (EVs) of brain origin isolated from blood and their protein cargoes could function as a biomarker of pathological conditions. We verified whether MBP and MOG content in oligodendrocytes-derived EVs (ODEVs) could be biomarkers of MS and could help in the differential diagnosis of clinical MS phenotypes. A total of 136 individuals (7 clinically isolated syndrome (CIS), 18 PPMS, 49 relapsing remitting (RRMS)) and 70 matched healthy controls (HC) were enrolled. ODEVs were enriched from serum by immune-capture with anti-MOG antibody; MBP and MOG protein cargoes were measured by ELISA. MBP concentration in ODEVs was significantly increased in CIS (p < 0.001), RRMS (p < 0.001) and PPMS (p < 0.001) compared to HC and was correlated with disease severity measured by EDSS and MSSS. Notably, MBP concentration in ODEVs was also significantly augmented in PPMS compared to RRMS (p = 0.004) and CIS (p = 0.03). Logistic regression and ROC analyses confirmed these results. A minimally invasive blood test measuring the concentration of MBP in ODEVs is a promising tool that could facilitate MS diagnosis.

Multiple sclerosis: Motor dysfunction

Multiple sclerosis is a chronic neurological disease characterized by inflammation and degeneration within the central nervous system. Over the course of the disease, most MS patients successively accumulate inflammatory lesions, axonal damage, and diffuse CNS pathology, along with an increasing degree of motor disability. While the pharmacological approach to MS targets inflammation to decrease relapse rates and relieve symptoms, disease-modifying therapy and immunosuppressive medications may not prevent the accumulation of pathology in most patients leading to long-term motor disability. This has been met with recent interest in promoting plasticity-guided concepts, enhanced by neurophysiological and neuroimaging approaches to address the preservation of motor function.

The immunology of multiple sclerosis

Our incomplete understanding of the causes and pathways involved in the onset and progression of multiple sclerosis (MS) limits our ability to effectively treat this complex neurological disease. Recent studies explore the role of immune cells at different stages of MS and how they interact with cells of the central nervous system (CNS). The findings presented here begin to question the exclusivity of an antigen-specific cause and highlight how seemingly distinct immune cell types can share common functions that drive disease. Innovative techniques further expose new disease-associated immune cell populations and reinforce how environmental context is critical to their phenotype and subsequent role in disease. Importantly, the differentiation of immune cells into a pathogenic state is potentially reversible through therapeutic manipulation. As such, understanding the mechanisms that provide plasticity to causal cell types is likely key to uncoupling these disease processes and may identify novel therapeutic targets that replace the need for cell ablation.

TCR-like antibodies targeting autoantigen-mhc complexes: a mini-review

T cell receptors (TCRs) recognize peptide antigens bound to major histocompatibility complex (MHC) molecules (p/MHC) that are expressed on cell surfaces; while B cell-derived antibodies (Abs) recognize soluble or cell surface native antigens of various types (proteins, carbohydrates, etc.). Immune surveillance by T and B cells thus inspects almost all formats of antigens to mount adaptive immune responses against cancer cells, infectious organisms and other foreign insults, while maintaining tolerance to self-tissues. With contributions from environmental triggers, the development of autoimmune disease is thought to be due to the expression of MHC risk alleles by antigen-presenting cells (APCs) presenting self-antigen (autoantigen), breaking through self-tolerance and activating autoreactive T cells, which orchestrate downstream pathologic events. Investigating and treating autoimmune diseases have been challenging, both because of the intrinsic complexity of these diseases and the need for tools targeting T cell epitopes (autoantigen-MHC). Naturally occurring TCRs with relatively low (micromolar) affinities to p/MHC are suboptimal for autoantigen-MHC targeting, whereas the use of engineered TCRs and their derivatives (e.g., TCR multimers and TCR-engineered T cells) are limited by unpredictable cross-reactivity. As Abs generally have nanomolar affinity, recent advances in engineering TCR-like (TCRL) Abs promise advantages over their TCR counterparts for autoantigen-MHC targeting. Here, we compare the p/MHC binding by TCRs and TCRL Abs, review the strategies for generation of TCRL Abs, highlight their application for identification of autoantigen-presenting APCs, and discuss future directions and limitations of TCRL Abs as immunotherapy for autoimmune diseases.

A high-affinity human TCR-like antibody detects celiac disease gluten peptide-MHC complexes and inhibits T cell activation

Antibodies specific for peptides bound to human leukocyte antigen (HLA) molecules are valuable tools for studies of antigen presentation and may have therapeutic potential. Here, we generated human T cell receptor (TCR)-like antibodies toward the immunodominant signature gluten epitope DQ2.5-glia-α2 in celiac disease (CeD). Phage display selection combined with secondary targeted engineering was used to obtain highly specific antibodies with picomolar affinity. The crystal structure of a Fab fragment of the lead antibody 3.C11 in complex with HLA-DQ2.5:DQ2.5-glia-α2 revealed a binding geometry and interaction mode highly similar to prototypic TCRs specific for the same complex. Assessment of CeD biopsy material confirmed disease specificity and reinforced the notion that abundant plasma cells present antigen in the inflamed CeD gut. Furthermore, 3.C11 specifically inhibited activation and proliferation of gluten-specific CD4⁺ T cells in vitro and in HLA-DQ2.5 humanized mice, suggesting a potential for targeted intervention without compromising systemic immunity.

Single-Domain Antibody-Based TCR-Like CAR-T: A Potential Cancer Therapy

Retargeting the antigen-binding specificity of T cells to intracellular antigens that are degraded and presented on the tumor surface by engineering chimeric antigen receptor (CAR), also named TCR-like antibody CAR-T, remains limited. With the exception of the commercialized CD19 CAR-T for hematological malignancies and other CAR-T therapies aiming mostly at extracellular antigens achieving great success, the rareness and scarcity of TCR-like CAR-T therapies might be due to their current status and limitations. This review provides the probable optimized initiatives for improving TCR-like CAR-T reprogramming and discusses single-domain antibodies administered as an alternative to conventional scFvs and secreted by CAR-T cells, which might be of great value to the development of CAR-T immunotherapies for intracellular antigens.

Nanoimmunosensor based on atomic force spectroscopy to detect anti-myelin basic protein related to early-stage multiple sclerosis

Multiple Sclerosis (MS) is a chronic inflammatory disorder in the central nervous system for which biomarkers for diagnosis still remain unknown. One potential biomarker is the myelin basic protein. Here, a nanoimmunosensor based on atomic force spectroscopy (AFS) successfully detected autoantibodies against the MBP_85-99 peptide from myelin basic protein. The nanoimmunosensor consisted of an atomic force microscope tip functionalization with MBP_85-99 peptide, which was made to interact with a mica surface coated either with a layer of anti-MBP_85-99 (positive control) or samples of cerebrospinal fluid (CSF) from five multiple sclerosis (MS) patients at different stages of the disease and five non-MS subjects. The adhesion forces obtained from AFS pointed to a high concentration of anti-MBP_85-99 for the two patients at early stages of relapsing-remitting multiple sclerosis (RRMS), which were indistinguishable from the positive control. In contrast, considerably lower adhesion forces were measured for all the other eight subjects, including three MS patients with longer history of the disease and under treatment, without episodes of acute MS activity. We have also shown that the average adhesion force between MBP_85-99 and anti-MBP_85-99 is compatible with the value estimated using steered molecular dynamics. Though further tests will be required with a larger cohort of patients, the present results indicate that the nanoimmunosensor may be a simple tool to detect early-stage MS patients and be useful to understand the molecular mechanisms behind MS.

Aberrant DNA methylation profile exacerbates inflammation and neurodegeneration in multiple sclerosis patients

Multiple sclerosis (MS) is an autoimmune and demyelinating disease of the central nervous system characterised by incoordination, sensory loss, weakness, changes in bladder capacity and bowel function, fatigue and cognitive impairment, creating a significant socioeconomic burden. The pathogenesis of MS involves both genetic susceptibility and exposure to distinct environmental risk factors. The gene x environment interaction is regulated by epigenetic mechanisms. Epigenetics refers to a complex system that modifies gene expression without altering the DNA sequence. The most studied epigenetic mechanism is DNA methylation. This epigenetic mark participates in distinct MS pathophysiological processes, including blood-brain barrier breakdown, inflammatory response, demyelination, remyelination failure and neurodegeneration. In this study, we also accurately summarised a list of environmental factors involved in the MS pathogenesis and its clinical course. A literature search was conducted using MEDLINE through PubMED and Scopus. In conclusion, an exhaustive study of DNA methylation might contribute towards new pharmacological interventions in MS by use of epigenetic drugs.

An Overview of the Intrinsic Role of Citrullination in Autoimmune Disorders

A protein undergoes many types of posttranslation modification. Citrullination is one of these modifications, where an arginine amino acid is converted to a citrulline amino acid. This process depends on catalytic enzymes such as peptidylarginine deiminase enzymes (PADs). This modification leads to a charge shift, which affects the protein structure, protein-protein interactions, and hydrogen bond formation, and it may cause protein denaturation. The irreversible citrullination reaction is not limited to a specific protein, cell, or tissue. It can target a wide range of proteins in the cell membrane, cytoplasm, nucleus, and mitochondria. Citrullination is a normal reaction during cell death. Apoptosis is normally accompanied with a clearance process via scavenger cells. A defect in the clearance system either in terms of efficiency or capacity may occur due to massive cell death, which may result in the accumulation and leakage of PAD enzymes and the citrullinated peptide from the necrotized cell which could be recognized by the immune system, where the immunological tolerance will be avoided and the autoimmune disorders will be subsequently triggered. The induction of autoimmune responses, autoantibody production, and cytokines involved in the major autoimmune diseases will be discussed.

Opportunities and Challenges for Antibodies against Intracellular Antigens

Therapeutic antibodies are one most significant advances in immunotherapy, the development of antibodies against disease-associated MHC-peptide complexes led to the introduction of TCR-like antibodies. TCR-like antibodies combine the recognition of intracellular proteins with the therapeutic potency and versatility of monoclonal antibodies (mAb), offering an unparalleled opportunity to expand the repertoire of therapeutic antibodies available to treat diseases like cancer. This review details the current state of TCR-like antibodies and describes their production, mechanisms as well as their applications. In addition, it presents an insight on the challenges that they must overcome in order to become commercially and clinically validated.

The Contribution of Major Histocompatibility Complex Class II Genes to an Association with Autoimmune Diseases

Genetic studies of patients with autoimmune diseases have shown that one of the most important roles in the developing of these diseases is played by a cluster of genes of the major histocompatibility complex (MHC), as compared with other genome areas. Information on the specific contribution of MHC alleles, mostly MHC class II ones, to the genetic predisposition to autoimmune diseases is crucial for understanding their pathogenesis. This review dwells on the most relevant aspects of this problem: namely, the correlation between carriage of certain MHC II alleles and an increased (positively associated allele) or reduced (negatively associated allele) probability of developing the most common autoimmune diseases, such as type 1 diabetes, rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, autoimmune thyroiditis, etc. The most universal haplotypes, DR3-DQ2 and DR4-DQ8, are positively associated with many of these diseases, while the universal allele HLA-DRB1*0701 is protective.

Multiple sclerosis pathogenesis: missing pieces of an old puzzle

Traditionally, multiple sclerosis (MS) was considered to be a CD4 T cell-mediated CNS autoimmunity, compatible with experimental autoimmune encephalitis model, which can be characterized by focal lesions in the white matter. However, studies of recent decades revealed several missing pieces of MS puzzle and showed that MS pathogenesis is more complex than the traditional view and may include the following: a primary degenerative process (e.g. oligodendroglial pathology), generalized abnormality of normal-appearing brain tissue, pronounced gray matter pathology, involvement of innate immunity, and CD8 T cells and B cells. Here, we review these findings and discuss their implications in MS pathogenesis.

Targeting the MHC Ligandome by Use of TCR-Like Antibodies

Monoclonal antibodies (mAbs) are valuable as research reagents, in diagnosis and in therapy. Their high specificity, the ease in production, favorable biophysical properties and the opportunity to engineer different properties make mAbs a versatile class of biologics. mAbs targeting peptide–major histocompatibility molecule (pMHC) complexes are often referred to as “TCR-like” mAbs, as pMHC complexes are generally recognized by T-cell receptors (TCRs). Presentation of self- and non-self-derived peptide fragments on MHC molecules and subsequent activation of T cells dictate immune responses in health and disease. This includes responses to infectious agents or cancer but also aberrant responses against harmless self-peptides in autoimmune diseases. The ability of TCR-like mAbs to target specific peptides presented on MHC allows for their use to study peptide presentation or for diagnosis and therapy. This extends the scope of conventional mAbs, which are generally limited to cell-surface or soluble antigens. Herein, we review the strategies used to generate TCR-like mAbs and provide a structural comparison with the analogous TCR in pMHC binding. We further discuss their applications as research tools and therapeutic reagents in preclinical models as well as challenges and limitations associated with their use.

Design and molecular dynamic simulation of a new double-epitope tolerogenic protein as a potential vaccine for multiple sclerosis disease

One of the debilitating diseases affecting the central nervous system is multiple sclerosis (MS). As there is no definitive treatment for MS, researchers have mainly consented with optimization of strategies which slows down the progression of the disease such as specific auto-antigens tolerance induction. In this regard, the aim of this study was design of a new double-epitope protective vaccine based on interleukin (IL)-16-neuroantigens fusion proteins. First, we selected highly antigenic epitopes of myelin basic protein (MBP) (aa 84-104) and myelin oligodendrocyte glycoprotein (MOG) (aa 99-107) from available literature and our bioinformatics analysis. The correct cleavage of our constructs and major histocompatibility complex class II binding affinities of cleaved epitopes were checked and evaluated using Pepcleave and IEDB servers, respectively. Then, different combination of MOG and MBP epitopes with or without fusion to C-terminal active part of IL-16 were designed as constructs. Afterward, Modeller and Gromacs softwares used for the investigation of the MBP, and MOG epitopes antigenicity in these constructs. The results of molecular dynamics simulations showed that IL-16 in MOG + linker + MBP + IL-16 construct does not interfere with final epitopes antigenicity of MOG + linker + MBP construct. To sum up, the construct with IL-16 is suggested as a new double-epitope tolerogenic vaccine for prevention and amelioration of MS in human.

Anti-Mycobacterial Antibodies in Paired Cerebrospinal Fluid and Serum Samples from Japanese Patients with Multiple Sclerosis or Neuromyelitis Optica Spectrum Disorder

Local synthesis of antibodies and presence of oligoclonal bands in the cerebrospinal fluid (CSF) are hallmarks of multiple sclerosis (MS). We investigated the frequency of antibodies against mycobacterial and relevant human epitopes in the CSF of patients with MS or neuromyelitis optica spectrum disorder (NMOSD) and whether these antibodies differed from those present in the serum. Matched serum and CSF samples from 46 patients with MS, 42 patients with NMOSD, and 29 age-matched and sex-matched control subjects were screened retrospectively for the presence of antibodies against Mycobacterium avium subsp. paratuberculosis (MAP) pentapeptide (MAP_5p), MAP_2694_295–303, and myelin basic protein (MBP)_85–98 peptides by using indirect ELISA. Serum levels of anti-MAP_5p and anti-MAP_2694_295–303 antibodies were highly prevalent in patients with MS when compared to patients with NMOSD and controls. Several patients with MS had detectable anti-MAP_5p and anti-MAP_2694_295–303 antibodies in the CSF. Furthermore, a group of patients with MS showed intrathecally restricted production of antibodies against these peptides. Women appeared to mount a stronger humoral response to mycobacterial peptides than men. No significant difference in the frequency of anti-MBP_85–98 antibodies was found between patients with MS and those with NMOSD. These data highlight the zoonotic potential of MAP, which suggests its involvement in MS etiopathogenesis.

Association of human leukocyte antigen-DRB haplotype in multiple sclerosis population of Khuzestan, Iran

Background: One of the demyelinating and inflammatory diseases of the central nervous system (CNS) is multiple sclerosis (MS). Though pathogenesis of MS is still unknown, both genetic and environmental factors are involved. The human leukocyte antigen (HLA) class-II alleles including HLA-DRB5*01, DQB1*0602, DRB1*1501, and DQA1*0102 may have remarkable effect in MS risk although it is controversial in studies. As there is no data with respect to the HLA-DRB1*1501-DRB5*01 correlation with MS in Khuzestan Province, Iran, the goal of the survey was to investigate the association of this haplotype with MS in this population. Methods: The study focused on DRB5*01-DRB1*1501 haplotype association with MS in 200 patients and 200 healthy individuals. Typing of HLA was carried out by polymerase chain reaction (PCR) amplification with sequence-specific primers (SSP) method. SPSS software was used for the statistical analyses. Results: No association between DRB5*01⁺-DRB1*1501⁺ and MS was found (P = 0.156). Distribution of DRB1*1501⁺-DRB5*01^- (carrying DRB1*1501⁺ but not DRB5*01^-) and DRB1*1501^--DRB5*01^- haplotypes was statistically different between patients and controls (29.73% vs. 11.81%, P < 0.001) and (42.16% vs. 68.50%, P < 0.001), respectively. However, DRB1*1501^--DRB5*01⁺ revealed no association with MS (15.13% vs. 11.81%, P = 0.403). HLA-DRB1*1501^--DRB5*01⁺ was significantly more frequent among female patients with MS (16.19% vs. 6.12%, P = 0.019) and Persian group (17.11% vs. 5.79%, P = 0.027). Positive correlation of HLA-DRB1*1501⁺-DRB5*01^- haplotype with the expanded disability status scale (EDSS) steps from 5 to 10 was observed (62.50% vs. 25.76%, P = 0.026). Moreover, no meaningful association was shown among the haplotypes with EDSS, course of MS, ethnicity, and gender. Conclusion: Our findings suggest that DRB1*1501⁺-DRB5*01^- and DRB1*1501^--DRB5*01^- haplotypes may have positive association with MS risk. Also, this survey indicates that HLA-DRB1*1501^--DRB5*01⁺ is involved in susceptibility of the disease among women and Persians. DRB1*1501⁺-DRB5*01^- genotype frequency may have a key role in MS developing.

Structure-based selection of human metabolite binding P4 pocket of DRB1*15:01 and DRB1*15:03, with implications for multiple sclerosis

Binding of small molecules in the human leukocyte antigen (HLA) peptide-binding groove may result in conformational changes of bound peptide and an altered immune response, but previous studies have not considered a potential role for endogenous metabolites. We performed virtual screening of the complete Human Metabolite Database (HMDB) for docking to the multiple sclerosis (MS) susceptible DRB1*15:01 allele and compared the results to the closely related yet non-susceptible DRB1*15:03 allele; and assessed the potential impact on binding of human myelin basic peptide (MBP). We observed higher energy scores for metabolite binding to DRB1*15:01 than DRB1*15:03. Structural comparison of docked metabolites with DRB1*15:01 and DRB1*15:03 complexed with MBP revealed that Phenylalanine^MBP92 allows binding of metabolites in the P4 pocket of DRB1*15:01 but Valine^MBP89 abrogates metabolite binding in the P1 pocket. We observed differences in the energy scores for binding of metabolites in the P4 pockets of DRB1*15:01 vs. DRB1*15:03 suggesting stronger binding to DRB1*15:01. Our study confirmed that specific, disease-associated human metabolites bind effectively with the most polymorphic P4 pocket of DRB1*15:01, the primary MS susceptible allele in most populations. Our results suggest that endogenous human metabolites bound in specific pockets of HLA may be immunomodulatory and implicated in autoimmune disease.

Cyclic MOG35-55 ameliorates clinical and neuropathological features of experimental autoimmune encephalomyelitis

EAE is induced to susceptible mice using linear peptides of myelin proteins of the central nervous system. Specific peptide motifs within the peptide-binding groove of the MHC peptide-complex determines the affinity of the peptide in each animal and the consequent T-cell receptor recognition and activation of the cell. Altered peptide ligand (APL) vaccination is a novel approach based on an effort to induce T-cell tolerance or alter cytokine profile from pro-inflammatory to anti-inflammatory. In the present study we synthesized the MOG_35-55 peptide and altered its 3-dimensional conformation to make it a cyclic one (c-MOG_35-55). EAE was induced in C57BL/6 mice and pathology was studied on acute and chronic phase of the disease. Our data indicates that c-MOG_35-55 peptide alone induces a mild transient acute phase without chronic axonopathy. Administration of the c-MOG_35-55 peptide at a 1:1 ratio during disease induction significantly ameliorates clinical disease and underlying pathology, such as demyelination and axonopathy in the acute and chronic phases. Binding and structural studies revealed milder interactions between the c-MOG_35-55 and mouse or human MHC class II alleles (H2-IA^b and HLA-DR2). Collectively, we provide data supporting for the first time the concept that the cyclic modification of an established encephalitogenic peptide ameliorates the clinical outcomes and underlying pathological processes of EAE. Such a cyclic modification of linear peptides could provide a novel treatment approach for future, patient-selective, immunomodulative treatments of multiple sclerosis.

A parallel panning scheme used for selection of a GluA4-specific Fab targeting the ligand-binding domain

A method for development of murine Fab fragments towards extracellular domains of a surface receptor is presented. The GluA4 ionotropic glutamate receptor is used as a model system. Recombinant GluA4 ectodomain comprising both the N-terminal domain (NTD) and the ligand-binding domain (LBD) in one molecule was used for immunization. A Fab-phage library was constructed and a parallel panning approach enabled selection of murine Fab fragments towards either intact ectodomain or the isolated LBD of the GluA4 receptor. One LBD-Fab (FabL9) showed exclusive selectivity for the GluA4 LBD, over a panel of LBDs from GluA2, GluK1, GluK2 and GluD2. Soluble FabL9 was produced in amounts suitable for characterization. Competitive ELISA and rat-brain immunoprecipitation experiments confirmed that the FabL9 epitope is conserved in the LBD and in the intact native receptor. By an alignment of GluA2 and GluA4, the likely binding epitope for FabL9 was predicted. This study demonstrates a simple approach for development of antibody fragments towards specific sub-domains of a large ligand-gated ion channel, and this method could be utilized for all multi-domain surface receptors where antibody domain-selectivity may be desirable. Furthermore, we present for the first time a GluA4 subtype-specific murine Fab fragment targeting the LBD of the receptor.

Myelin Basic Protein Citrullination in Multiple Sclerosis: A Potential Therapeutic Target for the Pathology

Multiple sclerosis (MS) is a multifactorial demyelinating disease characterized by neurodegenerative events and autoimmune response against myelin component. Citrullination or deimination, a post-translational modification of protein-bound arginine into citrulline, catalyzed by Ca(2+) dependent peptidylarginine deiminase enzyme (PAD), plays an essential role in physiological processes include gene expression regulation, apoptosis and the plasticity of the central nervous system, while aberrant citrullination can generate new epitopes, thus involving in the initiation and/or progression of autoimmune disorder like MS. Myelin basic protein (MBP) is the major myelin protein and is generally considered to maintain the stability of the myelin sheath. This review describes the MBP citrullination and its consequence, as well as offering further support for the "inside-out" hypothesis that MS is primarily a neurodegenerative disease with secondary inflammatory demyelination. In addition, it discusses the role of MBP citrullination in the immune inflammation and explores the potential of inhibition of PAD enzymes as a therapeutic strategy for the disease.

Activity of 8F4, a T-cell receptor-like anti-PR1/HLA-A2 antibody, against primary human AML in vivo

The PR1 peptide, derived from the leukemia-associated antigens proteinase 3 and neutrophil elastase, is overexpressed on HLA-A2 in acute myeloid leukemia (AML). We developed a high affinity T cell receptor-like murine monoclonal antibody, 8F4, which binds to the PR1/HLA-A2 complex, mediates lysis of AML, and inhibits leukemia colony formation. Here, we explored whether 8F4 was active in vivo against chemotherapy-resistant AML, including secondary AML. In a screening model, co-incubation of AML with 8F4 ex vivo prevented engraftment of all tested AML subtypes in immunodeficient NSG mice. In a treatment model of established human AML, administration of 8F4 significantly reduced or eliminated AML xenografts and extended survival compared with isotype antibody-treated mice. Moreover, in secondary transfer experiments, mice inoculated with bone marrow from 8F4-treated mice showed no evidence of AML engraftment, supporting possible activity of 8F4 against the subset of AML with self-renewing potential. Our data provide evidence that 8F4 antibody is highly active in AML, including chemotherapy-resistant disease, supporting its potential use as a therapeutic agent in patients with AML.

Myelin Basic Protein-Induced Production of Tumor Necrosis Factor-α and Interleukin-6, and Presentation of the Immunodominant Peptide MBP85-99 by B Cells from Patients with Relapsing-Remitting Multiple Sclerosis

B cells are involved in driving relapsing-remitting multiple sclerosis (RRMS), as demonstrated by the positive effect of therapeutic B-cell depletion. Aside from producing antibodies, B cells are efficient antigen-presenting and cytokine-secreting cells. Diverse polyclonal stimuli have been used to study cytokine production by B cells, but here we used the physiologically relevant self-antigen myelin basic protein (MBP) to stimulate B cells from untreated patients with RRMS and healthy donors. Moreover, we took advantage of the unique ability of the monoclonal antibody MK16 to recognize the immunodominant peptide MBP85-99 presented on HLA-DR15, and used it as a probe to directly study B-cell presentation of self-antigenic peptide. The proportions of B cells producing TNF-α or IL-6 after stimulation with MBP were higher in RRMS patients than in healthy donors, indicating a pro-inflammatory profile for self-reactive patient B cells. In contrast, polyclonal stimulation with PMA + ionomycin and MBP revealed no difference in cytokine profile between B cells from RRMS patients and healthy donors. Expanded disability status scale (EDSS) as well as multiple sclerosis severity score (MSSS) correlated with reduced ability of B cells to produce IL-10 after stimulation with MBP, indicative of diminished B-cell immune regulatory function in patients with the most severe disease. Moreover, EDSS correlated positively with the frequencies of TNF-α, IL-6 and IL-10 producing B cells after polyclonal stimulation. Patient-derived, IL-10-producing B cells presented MBP85-99 poorly, as did IL-6-producing B cells, particulary in the healthy donor group. B cells from MS patients thus present antigen to T cells in a pro-inflammatory context. These findings contribute to understanding the therapeutic effects of B-cell depletion in human autoimmune diseases, including MS.

Antigen Presentation, Autoantigens, and Immune Regulation in Multiple Sclerosis and Other Autoimmune Diseases

Antigen presentation is in the center of the immune system, both in host defense against pathogens, but also when the system is unbalanced and autoimmune diseases like multiple sclerosis (MS) develop. It is not just by chance that a major histocompatibility complex gene is the major genetic susceptibility locus in MS; a feature that MS shares with other autoimmune diseases. The exact etiology of the disease, however, has not been fully understood yet. T cells are regarded as the major players in the disease, but most probably a complex interplay of altered central and peripheral tolerance mechanisms, T-cell and B-cell functions, characteristics of putative autoantigens, and a possible interference of environmental factors like microorganisms are at work. In this review, new data on all these different aspects of antigen presentation and their role in MS will be discussed, probable autoantigens will be summarized, and comparisons to other autoimmune diseases will be drawn.

Divergent paths for the selection of immunodominant epitopes from distinct antigenic sources

Immunodominant epitopes are few selected epitopes from complex antigens that initiate T cell responses. Here, to provide further insights into this process, we use a reductionist cell-free antigen processing system composed of defined components. We use the system to characterize steps in antigen processing of pathogen-derived proteins or autoantigens and we find distinct paths for peptide processing and selection. Autoantigen-derived immunodominant epitopes are resistant to digestion by cathepsins, whereas pathogen-derived epitopes are sensitive. Sensitivity to cathepsins enforces capture of pathogen-derived epitopes by Major Histocompatibility Complex class II (MHC class II) prior to processing, and resistance to HLA-DM-mediated-dissociation preserves the longevity of those epitopes. We show that immunodominance is established by higher relative abundance of the selected epitopes, which survive cathepsin digestion either by binding to MHC class II and resisting DM-mediated-dissociation, or being chemically resistant to cathepsins degradation. Non-dominant epitopes are sensitive to both DM and cathepsins and are destroyed.

Uptake and presentation of myelin basic protein by normal human B cells

B cells may play both pathogenic and protective roles in T-cell mediated autoimmune diseases such as multiple sclerosis (MS). These functions relate to the ability of B cells to bind and present antigens. Under serum-free conditions we observed that 3–4% of circulating B cells from healthy donors were capable of binding the MS-associated self-antigen myelin basic protein (MBP) and of presenting the immunodominant peptide MBP85-99, as determined by staining with the mAb MK16 recognising the peptide presented by HLA-DR15-positive cells. In the presence of serum, however, the majority of B cells bound MBP in a complement-dependent manner, and almost half of the B cells became engaged in presentation of MBP85-99. Even though complement receptor 1 (CR1, CD35) and CR2 (CD21) both contributed to binding of MBP to B cells, only CR2 was important for the subsequent presentation of MBP85-99. A high proportion of MBP85-99 presenting B cells expressed CD27, and showed increased expression of CD86 compared to non-presenting B cells. MBP-pulsed B cells induced a low frequency of IL-10-producing CD4+ T cells in 3 out of 6 donors, indicating an immunoregulatory role of B cells presenting MBP-derived peptides. The mechanisms described here refute the general assumption that B-cell presentation of self-antigens requires uptake via specific B-cell receptors, and may be important for maintenance of tolerance as well as for driving T-cell responses in autoimmune diseases.

Dynamic interaction between astrocytes and infiltrating PBMCs in context of neuroAIDS

HIV-mediated neuropathogenesis is a multifaceted process involving several players, including resident brain cells (neurons, astrocytes, and microglia) and infiltrating cells [peripheral blood mononuclear cells (PBMCs)]. We evaluated the dynamic interaction between astrocytes and infiltrating PBMCs as it impacts HIV in the CNS. We demonstrate that human primary-derived astrocytes (PDAs) predominantly secrete Wnt 1, 2b, 3, 5b, and 10b. Wnts are small secreted glycoproteins that initiate either β-catenin-dependent or independent signal transduction. The Wnt pathway plays a vital role in the regulation of CNS activities including neurogenesis, neurotransmitter release, synaptic plasticity, and memory consolidation. We show that HIV infection of PDAs altered astrocyte Wnt profile by elevating Wnts 2b and 10b. Astrocyte conditioned media (ACM) inhibited HIV replication in PBMCs by 50%. Removal of Wnts from ACM abrogated its ability to suppress HIV replication in PBMCs. Inversely, PBMCs supernatant activated PDAs, as demonstrated by a 10-fold increase in HLA-DR and a 5-fold increase in IFNγ expression, and enhanced astrocyte susceptibility to HIV by 2-fold, which was mediated by IFNγ in a Stat-3-dependent manner. Collectively, these data demonstrate a dynamic interaction between astrocytes and PBMCs, whereby astrocyte-secreted Wnts exert an anti-HIV effect on infected PBMCs and PBMCs, in turn, secrete IFNγ that enhance astrocyte susceptibility to productive HIV infection and mediate their activation.

Pathology of multiple sclerosis and related inflammatory demyelinating diseases

This article provides a comprehensive overview of the pathology of multiple sclerosis (MS), including recent insights into its molecular neuropathology and immunology. It shows that all clinical manifestations of relapsing and progressive MS display the same basic features of pathology, such as chronic inflammation, demyelination in the white and gray matter, and diffuse neurodegeneration within the entire central nervous system. However, the individual components of the pathological spectrum vary quantitatively between early relapsing and late progressive MS. Widespread confluent and plaque-like demyelination with oligodendrocyte destruction is the unique pathological hallmark of the disease, but axonal injury and neurodegeneration are additionally present and in part extensive. Remyelination of existing lesions may occur in MS brains; it is extensive in a subset of patients, while it fails in others. Active tissue injury in MS is always associated with inflammation, consistent with T-cell and macrophage infiltration and microglia activation. Recent data suggest that oxidative injury and subsequent mitochondrial damage play a major pathogenetic role in neurodegeneration. Finally we discuss similarities and differences of the pathology between classical MS and other inflammatory demyelinating diseases, such as neuromyelitis optica, concentric sclerosis, or acute disseminated encephalomyelitis.

Construction and molecular characterization of a T-cell receptor-like antibody and CAR-T cells specific for minor histocompatibility antigen HA-1H

The genetic transfer of T-cell receptors (TCRs) directed toward target antigens into T lymphocytes has been used to generate antitumor T cells efficiently without the need for the in vitro induction and expansion of T cells with cognate specificity. Alternatively, T cells have been gene-modified with a TCR-like antibody or chimeric antigen receptor (CAR). We show that immunization of HLA-A2 transgenic mice with tetramerized recombinant HLA-A2 incorporating HA-1 H minor histocompatibility antigen (mHag) peptides and β2-microglobulin (HA-1 H/HLA-A2) generate highly specific antibodies. One single-chain variable region moiety (scFv) antibody, #131, demonstrated high affinity (KD=14.9 nM) for the HA-1 H/HLA-A2 complex. Primary human T cells transduced with #131 scFV coupled to CD28 transmembrane and CD3ζ domains were stained with HA-1 H/HLA-A2 tetramers slightly more intensely than a cytotoxic T lymphocyte (CTL) clone specific for endogenously HLA-A2- and HA-1 H-positive cells. Although #131 scFv CAR-T cells required >100-fold higher antigen density to exert cytotoxicity compared with the cognate CTL clone, they could produce inflammatory cytokines against cells expressing HLA-A2 and HA-1 H transgenes. These data implicate that T cells with high-affinity antigen receptors reduce the ability to lyse targets with low-density peptide/MHC complexes (~100 per cell), while they could respond at cytokine production level.

Demyelination in multiple sclerosis

This review, focused on demyelination in multiple sclerosis, is divided in two parts. The first part addresses the many and not exclusive mechanisms leading to demyelination in the central nervous system. Although the hypothesis that a primary oligodendrocyte or myelin injury induces a secondary immune response in the central nervous system is still a matter of debate, most recent advances underline the influence of a primary immune response against myelin antigen(s), with a diversity of potential targets. Whereas multiple sclerosis was long considered as a T cell-mediated disease, the role of B lymphocytes is now increasingly recognized, and the influence of antibodies on tissue damage actively investigated. The second part of the review describes the axonal consequences of demyelination. Segmental demyelination results in conduction block or slowing of conduction through adaptative responses, notably related to modifications in the distribution of voltage gated sodium channels along the denuded axon. If demyelination persists, these changes, as well as the loss of trophic and metabolic support, will lead to irreversible axonal damage and loss. In this respect, favouring early myelin repair, during a window of time when axonal damage is still reversible, might pave the way for neuroprotection.

Small molecule inhibitor of antigen binding and presentation by HLA-DR2b as a therapeutic strategy for the treatment of multiple sclerosis

The strong association of HLA-DR2b (DRB1*1501) with multiple sclerosis (MS) suggests this molecule as prime target for specific immunotherapy. Inhibition of HLA-DR2b-restricted myelin-specific T cells has the potential to selectively prevent CNS pathology mediated by these MHC molecules without undesired global immunosuppression. In this study, we report development of a highly selective small molecule inhibitor of peptide binding and presentation by HLA-DR2b. PV-267, the candidate molecule used in these studies, inhibited cytokine production and proliferation of myelin-specific HLA-DR2b-restricted T cells. PV-267 had no significant effect on T cell responses mediated by other MHC class II molecules, including HLA-DR1, -DR4, or -DR9. Importantly, PV-267 did not induce nonspecific immune activation of human PBMC. Lastly, PV-267 showed treatment efficacy both in preventing experimental autoimmune encephalomyelitis and in treating established disease. The results suggest that blocking the MS-associated HLA-DR2b allele with small molecule inhibitors may be a promising therapeutic strategy for the treatment of MS.

The kinetics of myelin antigen uptake by myeloid cells in the central nervous system during experimental autoimmune encephalomyelitis

Induction of experimental autoimmune encephalomyelitis (EAE) in susceptible animals requires reactivation of encephalitogenic CD4(+) T cells by APCs in the CNS. However, it has remained unresolved from where APCs in the CNS acquire myelin Ag for T cell activation and under which conditions, that is, whether only during EAE or also in the naive CNS. In this study, we investigated the kinetics of myelin Ag uptake by CNS APCs during EAE and in the naive CNS. Our results show that during EAE CX3CR1(+)CD11b(+) microglia were the first APCs in the CNS to contain myelin Ag upon induction of disease, albeit in very small numbers. Dendritic cells (DCs) arrived in the CNS in sizable numbers significantly later (day 5 postimmunization), without detectable myelin Ag, but acquired it by day 7 postimmunization. Furthermore, a sharp increase in neuroantigen-containing DCs coincided with the onset of EAE symptoms. Importantly, in naive mice a low but consistent number of microglia contained myelin Ag, suggesting release by oligodendrocytes under steady state conditions. Although microglia isolated from naive brain and spinal cord did not elicit a strong CD4(+) T cell response in vitro, myelin Ag-containing microglia may still play a local role in modulating encephalitogenic CD4(+) T cell responses in early EAE prior to the arrival of other professional APCs, such as DCs. Finally, newly arriving DCs in the CNS not yet loaded with myelin Ag before the onset of EAE may be a potential therapeutic target.

Antigen-specific immunomodulation for type 1 diabetes by novel recombinant antibodies directed against diabetes-associates auto-reactive T cell epitope

The trimolecular complex composed of autoreactive T-cell receptor, MHC class II, and an autoantigenic peptide plays a central role in the activation of pathogenic Islet-specific CD4+ T cells in type 1 diabetes (T1D). We isolated and characterized novel antibodies against autoreactive T-cell epitopes associated with T1D. Our antibodies mimic the specificity of the T-cell receptor (TCR), while binding MHC class II/peptide complexes in an autoantigen peptide specific, MHC-restricted manner. The isolated TCR-like antibodies were directed against the minimal T-cell epitope GAD-555-567 in the context of the HLA-DR4-diabetic-associated molecule. A representative high-affinity TCR-like antibody clone (G3H8) enabled the detection of intra- and extra-cellular DR4/GAD-555-567 complexes in antigen presenting cells. I561M single mutation at the central position (P5) of the GAD-555-567 peptide abolished the binding of G3H8 to the DR4/GAD complex, demonstrating its high fine TCR-like specificity. The G3H8 TCR-like antibody significantly inhibited GAD-555-567 specific, DR4 restricted T-cell response in vitro and in vivo in HLA-DR4 transgenic mice. Our findings constitute a proof-of-concept for the utility of TCR-like antibodies as antigen-specific immunomodulation agents for regulating pathogenic T-cells and suggest that TCR-like antibodies targeting autoreactive MHC class II epitopes are valuable research tools that enable studies related to antigen presentation as well as novel therapeutic agents that may be used to modulate autoimmune disorders such as T1D.

Vaccination with single chain antigen receptors for islet-derived peptides presented on I-A(g7) delays diabetes in NOD mice by inducing anergy in self-reactiveT-cells

To develop a vaccination approach for prevention of type 1 diabetes (T1D) that selectively attenuates self-reactive T-cells targeting specific autoantigens, we selected phage-displayed single chain antigen receptor libraries for clones binding to a complex of the NOD classII MHC I-A(g7) and epitopes derived from the islet autoantigen RegII. Libraries were generated from B-cell receptor repertoires of classII-mismatched mice immunized with RegII-pulsed NOD antigen presenting cells or from T-cell receptor repertoires in pancreatic lymph nodes of NOD mice. Both approaches yielded clones recognizing a RegII-derived epitope in the context of I-A(g7), which activated autoreactive CD4(+) T-cells. A receptor with different specificity was obtained by converting the BDC2.5 TCR into single chain form. B- but not T-cells from donors vaccinated with the clones transferred protection from diabetes to NOD-SCID recipients if the specificity of the diabetes inducer cell and the single chain receptor were matched. B-cells and antibodies from donors vaccinated with the BDC2.5 single chain receptor induced a state of profound anergy in T-cells of BDC2.5 TCR transgenic NOD recipients while B-cells from donors vaccinated with a single chain receptor specific for I-A(g7) RegII peptide complexes induced only partial non-responsiveness. Vaccination of normal NOD mice with receptors recognizing I-A(g7) RegII peptide complexes or with the BDC2.5 single chain receptor delayed onset of T1D. Thus anti-idiotypic vaccination can be successfully applied to T1D with vaccines either generated from self-reactive T-cell clones or derived from antigen receptor libraries.

Glatiramer acetate in treatment of multiple sclerosis: a toolbox of random co-polymers for targeting inflammatory mechanisms of both the innate and adaptive immune system?

Multiple sclerosis is a disease of the central nervous system, resulting in the demyelination of neurons, causing mild to severe symptoms. Several anti-inflammatory treatments now play a significant role in ameliorating the disease. Glatiramer acetate (GA) is a formulation of random polypeptide copolymers for the treatment of relapsing-remitting MS by limiting the frequency of attacks. While evidence suggests the influence of GA on inflammatory responses, the targeted molecular mechanisms remain poorly understood. Here, we review the multiple pharmacological modes-of-actions of glatiramer acetate in treatment of multiple sclerosis. We discuss in particular a newly discovered interaction between the leukocyte-expressed integrin α(M)β(2) (also called Mac-1, complement receptor 3, or CD11b/CD18) and perspectives on the GA co-polymers as an influence on the function of the innate immune system.

Myelin basic protein-specific TCR/HLA-DRB5*01:01 transgenic mice support the etiologic role of DRB5*01:01 in multiple sclerosis

Genetic susceptibility to multiple sclerosis (MS) has been linked to the HLA-DR15 haplotype consisting of DRB1*15:01(DR2b) and DRB5*01:01(DR2a) alleles. Given almost complete linkage disequilibrium of the two alleles, recent studies suggested differential roles in susceptibility (DR2b) or protection from MS (DR2a). Our objective was to assess the potential contribution of DR2a to disease etiology in MS using a humanized model of autoimmunity. To assess the potential contribution of DR2a to disease etiology, we created DR2a humanized transgenic (Tg) mice and subsequently crossed them to Tg mice expressing TL3A6, an MS patient-derived myelin basic protein 83-99-specific TCR. In TL3A6/DR2a Tg mice, CD4 Tg T cells escape thymic and peripheral deletion and initiate spontaneous experimental autoimmune encephalomyelitis (EAE) at low rates, depending on the level of DR2a expression. The ability to induce active EAE was also increased in animals expressing higher levels of DR2a. Inflammatory infiltrates and neuronal damage were present throughout the spinal cord, consistent with a classical ascending EAE phenotype with minor involvement of the cerebellum, brainstem, and peripheral nerve roots in spontaneous, as well as actively induced, disease. These studies emphasize the pathologic contribution of the DR2a allele to the development of autoimmunity when expressed as the sole MHC class II molecule, as well as strongly argue for DR2a as a contributor to the CNS autoimmunity in MS.

The future of autoimmunity

There have been enormous strides in our understanding of autoimmunity. These strides have come under the umbrellas of epidemiology, immunological phenotype and function, disease definitions and classification and especially new therapeutic reagents. However, while these advances have been herculean, there remains enormous voids. Some of these voids include genetic susceptibility and the interaction of genes and environment. The voids include induction of tolerance in preclinical disease and definitions of host susceptibility and responses to the expensive biologic agents. The voids include the so-called clustering of human autoimmune diseases and the issues of whether the incidence is rising in our western society. Other voids include the relationships between microbiology, vaccination, gut flora, overzealous use of antibiotics, and the role of nanoparticles and environmental pollution in either the induction or the natural history of disease. One cannot even begin to address even a fraction of these issues. However, in this special issue, we are attempting to discuss clinical issues in autoimmunity that are not usually found in generic reviews. The goal is to bring to the readership provocative articles that ultimately will lead to improvement in patient care.

PmpG303-311, a protective vaccine epitope that elicits persistent cellular immune responses in Chlamydia muridarum-immune mice

Urogenital Chlamydia serovars replicating in reproductive epithelium pose a unique challenge to host immunity and vaccine development. Previous studies have shown that CD4 T cells are necessary and sufficient to clear primary Chlamydia muridarum genital tract infections in the mouse model, making a protective CD4 T cell response a logical endpoint for vaccine development. Our previous proteomics studies identified 13 candidate Chlamydia proteins for subunit vaccines. Of those, PmpG-1 is the most promising vaccine candidate. To further that work, we derived a PmpG(303-311)-specific multifunctional Th1 T cell clone, designated PmpG1.1, from an immune C57BL/6 mouse and used it to investigate the presentation of the PmpG(303-311) epitope by infected epithelial cells. Epithelial presentation of the PmpG(303-311) epitope required bacterial replication, occurred 15 to 18 h postinfection, and was unaffected by gamma interferon (IFN-γ) pretreatment. Unlike epitopes recognized by other Chlamydia-specific CD4 T cell clones, the PmpG(303-311) epitope persisted on splenic antigen-presenting cells (APC) of mice that cleared primary genital tract infections. PmpG1.1 was activated by unmanipulated irradiated splenocytes from immune mice without addition of exogenous Chlamydia antigen, and remarkably, activation of PmpG1.1 by unmanipulated immune splenocytes was stronger 6 months postinfection than it was 3 weeks postinfection. Enhanced presentation of PmpG(303-311) epitope on splenic APC 6 months postinfection reflects some type of "consolidation" of a protective immune response. Understanding the antigen-presenting cell populations responsible for presenting PmpG(303-311) early (3 weeks) and late (6 months) postinfection will likely provide important insights into stable protective immunity against Chlamydia infections of the genital tract.

T-cell-receptor-like antibodies - generation, function and applications

Tumour and virus-infected cells are recognised by CD8+ cytotoxic T cells that, in response, are activated to eliminate these cells. In order to be activated, the clonotypic T-cell receptor (TCR) needs to encounter a specific peptide antigen presented by the membrane surface major histocompatibility complex (MHC) molecule. Cells that have undergone malignant transformation or viral infection present peptides derived from tumour-associated antigens or viral proteins on their MHC class I molecules. Therefore, disease-specific MHC-peptide complexes are desirable targets for immunotherapeutic approaches. One such approach transforms the unique fine specificity but low intrinsic affinity of TCRs to MHC-peptide complexes into high-affinity soluble antibody molecules endowed with a TCR-like specificity towards tumour or viral epitopes. These antibodies, termed TCR-like antibodies, are being developed as a new class of immunotherapeutics that can target tumour and virus-infected cells and mediate their specific killing. In addition to their therapeutic capabilities, TCR-like antibodies are being developed as diagnostic reagents for cancer and infectious diseases, and serve as valuable research tools for studying MHC class I antigen presentation.