Molecular mimicry in T cell-mediated autoimmunity: viral peptides activate human T cell clones specific for myelin basic protein

HLA-DR15 Molecules Jointly Shape an Autoreactive T Cell Repertoire in Multiple Sclerosis

The HLA-DR15 haplotype is the strongest genetic risk factor for multiple sclerosis (MS), but our understanding of how it contributes to MS is limited. Because autoreactive CD4⁺ T cells and B cells as antigen-presenting cells are involved in MS pathogenesis, we characterized the immunopeptidomes of the two HLA-DR15 allomorphs DR2a and DR2b of human primary B cells and monocytes, thymus, and MS brain tissue. Self-peptides from HLA-DR molecules, particularly from DR2a and DR2b themselves, are abundant on B cells and thymic antigen-presenting cells. Furthermore, we identified autoreactive CD4⁺ T cell clones that can cross-react with HLA-DR-derived self-peptides (HLA-DR-SPs), peptides from MS-associated foreign agents (Epstein-Barr virus and Akkermansia muciniphila), and autoantigens presented by DR2a and DR2b. Thus, both HLA-DR15 allomorphs jointly shape an autoreactive T cell repertoire by serving as antigen-presenting structures and epitope sources and by presenting the same foreign peptides and autoantigens to autoreactive CD4⁺ T cells in MS.

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HLA-DR15 present abundant HLA-DR-derived self-peptides on B cells

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Autoreactive T cells in MS recognize HLA-DR-derived self-peptides/DR15 complexes

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Foreign peptides/DR15 complexes trigger potential autoreactive T cells in MS

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HLA-DR15 shape an autoreactive T cell repertoire by cross-reactivity/restriction

Autoimmune and rheumatic musculoskeletal diseases as a consequence of SARS-CoV-2 infection and its treatment

The coronavirus disease-2019 (COVID-19) pandemic is likely to pose new challenges to the rheumatology community in the near and distant future. Some of the challenges, like the severity of COVID-19 among patients on immunosuppressive agents, are predictable and are being evaluated with great care and effort across the globe. A few others, such as atypical manifestations of COVID-19 mimicking rheumatic musculoskeletal diseases (RMDs) are being reported. Like in many other viral infections, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection can potentially lead to an array of rheumatological and autoimmune manifestations by molecular mimicry (cross-reacting epitope between the virus and the host), bystander killing (virus-specific CD8 + T cells migrating to the target tissues and exerting cytotoxicity), epitope spreading, viral persistence (polyclonal activation due to the constant presence of viral antigens driving immune-mediated injury) and formation of neutrophil extracellular traps. In addition, the myriad of antiviral drugs presently being tried in the treatment of COVID-19 can result in several rheumatic musculoskeletal adverse effects. In this review, we have addressed the possible spectrum and mechanisms of various autoimmune and rheumatic musculoskeletal manifestations that can be precipitated by COVID-19 infection, its therapy, and the preventive strategies to contain the infection.

Role of Infections in the Pathogenesis of Rheumatoid Arthritis: Focus on Mycobacteria

Rheumatoid arthritis (RA) is a systemic inflammatory autoimmune disease characterized by chronic erosive polyarthritis. A complex interaction between a favorable genetic background, and the presence of a specific immune response against a broad-spectrum of environmental factors seems to play a role in determining susceptibility to RA. Among different pathogens, mycobacteria (including Mycobacterium avium subspecies paratuberculosis, MAP), and Epstein–Barr virus (EBV), have extensively been proposed to promote specific cellular and humoral response in susceptible individuals, by activating pathways linked to RA development. In this review, we discuss the available experimental and clinical evidence on the interplay between mycobacterial and EBV infections, and the development of the immune dysregulation in RA.

Fulminant Acute Disseminated Encephalomyelitis: A Remarkable Outcome with Cyclophosphamide

Acute disseminated encephalomyelitis (ADEM) is an inflammatory demyelinating disease of the central nervous system which occurs predominantly in the pediatric population. Acute treatment is high-dose intravenous glucocorticoids. Alternative treatment is usually intravenous immune globulin and/or plasma exchange. Fulminant ADEM is rare in children. Only a few cases of cyclophosphamide use in refractory ADEM have been reported. Here, we report a case of a 12-year-old girl with fulminant ADEM who was comatose and improved dramatically after cyclophosphamide administration. Cyclophosphamide treatment should be considered as a therapy in children with fulminant ADEM nonresponsive to standard therapies.

To Remember or to Forget: The Role of Good and Bad Memories in Adoptive T Cell Therapy for Tumors

The generation of immunological memory is a hallmark of adaptive immunity by which the immune system “remembers” a previous encounter with an antigen expressed by pathogens, tumors, or normal tissues; and, upon secondary encounters, mounts faster and more effective recall responses. The establishment of T cell memory is influenced by both cell-intrinsic and cell-extrinsic factors, including genetic, epigenetic and environmental triggers. Our current knowledge of the mechanisms involved in memory T cell differentiation has instructed new opportunities to engineer T cells with enhanced anti-tumor activity. The development of adoptive T cell therapy has emerged as a powerful approach to cure a subset of patients with advanced cancers. Efficacy of this approach often requires long-term persistence of transferred T cell products, which can vary according to their origin and manufacturing conditions. Host preconditioning and post-transfer supporting strategies have shown to promote their engraftment and survival by limiting the competition with a hostile tumor microenvironment and between pre-existing immune cell subsets. Although in the general view pre-existing memory can confer a selective advantage to adoptive T cell therapy, here we propose that also “bad memories”—in the form of antigen-experienced T cell subsets—co-evolve with consequences on newly transferred lymphocytes. In this review, we will first provide an overview of selected features of memory T cell subsets and, then, discuss their putative implications for adoptive T cell therapy.

Psychological Stress, Intestinal Barrier Dysfunctions, and Autoimmune Disorders: An Overview

Autoimmune disorders (ADs) are multifactorial diseases involving, genetic, epigenetic, and environmental factors characterized by an inappropriate immune response toward self-antigens. In the past decades, there has been a continuous rise in the incidence of ADs, which cannot be explained by genetic factors alone. Influence of psychological stress on the development or the course of autoimmune disorders has been discussed for a long time. Indeed, based on epidemiological studies, stress has been suggested to precede AD occurrence and to exacerbate symptoms. Furthermore, compiling data showed that most of ADs are associated with gastrointestinal symptoms, that is, microbiota dysbiosis, intestinal hyperpermeability, and intestinal inflammation. Interestingly, social stress (acute or chronic, in adult or in neonate) is a well-described intestinal disrupting factor. Taken together, those observations question a potential role of stress-induced defect of the intestinal barrier in the onset and/or the course of ADs. In this review, we aim to present evidences supporting the hypothesis for a role of stress-induced intestinal barrier disruption in the onset and/or the course of ADs. We will mainly focus on autoimmune type 1 diabetes, multiple sclerosis and systemic lupus erythematosus, ADs for which we could find sufficient circumstantial data to support this hypothesis. We excluded gastrointestinal (GI) ADs like coeliac disease to privilege ADs not focused on intestinal disorders to avoid confounding factors. Indeed, GIADs are characterized by antibodies directed against intestinal barrier actors.

Exome-Sequence Analyses of Four Multi-Incident Multiple Sclerosis Families

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the Central Nervous System (CNS). Currently, it is estimated that 30-40% of the phenotypic variability of MS can be explained by genetic factors. However, low susceptibility variants identified through Genome Wide Association Study (GWAS) were calculated to explain about 50% of the heritability. Whether familial high-risk variants also contribute to heritability is a subject of controversy. In the last few years, several familial variants have been nominated, but none of them have been unequivocally confirmed. One reason for this may be that genetic heterogeneity and reduced penetrance are hindering detection. Sequencing a large number of MS families is needed to answer this question. In this study, we performed whole exome sequencing in four multi-case families, of which at least three affected individuals per family were analyzed. We identified a total of 138 rare variants segregating with disease in each of the families. Although no single variant showed convincing evidence for disease causation, some genes seemed particularly interesting based on their biological function. The main aim of this study was to provide a complete list of all rare segregating variants to provide the possibility for other researchers to cross-check familial candidate genes in an unbiased manner.

The Role of Herpes Simplex Virus Type 1 Infection in Demyelination of the Central Nervous System

Herpes simplex type 1 (HSV-1) is a neurotropic virus that infects the peripheral and central nervous systems. After primary infection in epithelial cells, HSV-1 spreads retrogradely to the peripheral nervous system (PNS), where it establishes a latent infection in the trigeminal ganglia (TG). The virus can reactivate from the latent state, traveling anterogradely along the axon and replicating in the local surrounding tissue. Occasionally, HSV-1 may spread trans-synaptically from the TG to the brainstem, from where it may disseminate to higher areas of the central nervous system (CNS). It is not completely understood how HSV-1 reaches the CNS, although the most accepted idea is retrograde transport through the trigeminal or olfactory tracts. Once in the CNS, HSV-1 may induce demyelination, either as a direct trigger or as a risk factor, modulating processes such as remyelination, regulation of endogenous retroviruses, or molecular mimicry. In this review, we describe the current knowledge about the involvement of HSV-1 in demyelination, describing the pathways used by this herpesvirus to spread throughout the CNS and discussing the data that suggest its implication in demyelinating processes.

Recent Advances in Antigen-Specific Immunotherapies for the Treatment of Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system and is considered to be the leading non-traumatic cause of neurological disability in young adults. Current treatments for MS comprise long-term immunosuppressant drugs and disease-modifying therapies (DMTs) designed to alter its progress with the enhanced risk of severe side effects. The Holy Grail for the treatment of MS is to specifically suppress the disease while at the same time allow the immune system to be functionally active against infectious diseases and malignancy. This could be achieved via the development of immunotherapies designed to specifically suppress immune responses to self-antigens (e.g., myelin antigens). The present study attempts to highlight the various antigen-specific immunotherapies developed so far for the treatment of multiple sclerosis (e.g., vaccination with myelin-derived peptides/proteins, plasmid DNA encoding myelin epitopes, tolerogenic dendritic cells pulsed with encephalitogenic epitopes of myelin proteins, attenuated autologous T cells specific for myelin antigens, T cell receptor peptides, carriers loaded/conjugated with myelin immunodominant peptides, etc), focusing on the outcome of their recent preclinical and clinical evaluation, and to shed light on the mechanisms involved in the immunopathogenesis and treatment of multiple sclerosis.

The effect of home exercise on the posture and mobility of people with HAM/TSP: a randomized clinical trial

BACKGROUND

Physical therapy has positive results in people with tropical spastic paraparesis (TSP). However, mobility and distance from rehabilitation centers limit the participation in outpatient programs.

OBJECTIVE

To evaluate the impact of a home exercise program on the posture and functional mobility of people with TSP.

METHODS

A randomized controlled trial comparing three groups of people who performed guided exercises from a guidebook for six months: supervised (SG), unsupervised (WG), and control (CG). Primary outcomes: postural angles (SAPO®) and functional mobility (TUG).

SECONDARY OUTCOMES

gait parameters (CVMob®).

RESULTS

The protocol described in the guidebook improved postural angles and functional mobility. There were also positive gait parameter effects (p<0.05). SG presented better responses than WG did, but both were preferable to CG.

CONCLUSION

Home exercises oriented by a guidebook may benefit posture, functional mobility and gait parameters in people with TSP, and physiotherapist supervision can ensure better results.

A Bioinformatics Analysis Reveals Novel Pathogens as Molecular Mimicry Triggers of Systemic Sclerosis

A recent bioinformatic analysis revealing dominant B cell epitopes of systemic sclerosis-specific autoantibodies, including anti-centromere B, anti-topoisomerase I and anti-fibrillarin, has demonstrated the existence of several in silico antigenic mimics of pathogens that could act as triggers of the respective dominant autoepitopes. Based on those findings, the aim of the present study was to use a more comprehensive bioinformatic analysis. We demonstrated the presence of a plethora of novel microbial mimics, unnoticed by the studies so far conducted, which share remarkable amino acid similarities with the respective autoantigenic epitopes. This bioinformatic approach coupled by in vitro testing of the homologous self/non-self-mimics in serum samples from patients with systemic sclerosis may provide novel evidence of immunological cross-reactivity, implicating currently ignored or overlooked pathogens, which may indeed play a role in the induction of SSc-specific autoantibodies and assist efforts to understand the pathogenesis of this enigmatic disease.

Viral infections and multiple sclerosis

The etiology and pathogenesis of MS is likely to involve multiple factors interacting with each other, and the role of infectious and viral agents is still under debate, however a consistent amount of studies suggests that some viruses are associated with the disease. The strongest documentation has come from the detection of viral nucleic acid or antigen or of an anti-viral antibody response in MS patients. A further step for the study of the mechanism viruses might be involved in can be made using in vitro and in vivo models. While in vitro models, based on glial and neural cell lines from various sources are widely used, in vivo animal models present challenges. Indeed neurotropic animal viruses are currently used to study demyelination in well-established models, but animal models of demyelination by human virus infection have only recently been developed, using animal gammaherpesviruses closely related to Epstein Barr virus (EBV), or using marmosets expressing the specific viral receptor for Human Herpesvirus 6 (HHV-6). The present review will illustrate the main potential mechanisms of MS pathogenesis possibly associated with viral infections and viruses currently used to study demyelination in animal models. Then the viruses most strongly linked with MS will be discussed, in the perspective that more than one virus might have a role, with varying degrees of interaction, contributing to MS heterogeneity.

GPU-Accelerated Discovery of Pathogen-Derived Molecular Mimics of a T-Cell Insulin Epitope

The strong links between (Human Leukocyte Antigen) HLA, infection and autoimmunity combine to implicate T-cells as primary triggers of autoimmune disease (AD). T-cell crossreactivity between microbially-derived peptides and self-peptides has been shown to break tolerance and trigger AD in experimental animal models. Detailed examination of the potential for T-cell crossreactivity to trigger human AD will require means of predicting which peptides might be recognised by autoimmune T-cell receptors (TCRs). Recent developments in high throughput sequencing and bioinformatics mean that it is now possible to link individual TCRs to specific pathologies for the first time. Deconvolution of TCR function requires knowledge of TCR specificity. Positional Scanning Combinatorial Peptide Libraries (PS-CPLs) can be used to predict HLA-restriction and define antigenic peptides derived from self and pathogen proteins. In silico search of the known terrestrial proteome with a prediction algorithm that ranks potential antigens in order of recognition likelihood requires complex, large-scale computations over several days that are infeasible on a personal computer. We decreased the time required for peptide searching to under 30 min using multiple blocks on graphics processing units (GPUs). This time-efficient, cost-effective hardware accelerator was used to screen bacterial and fungal human pathogens for peptide sequences predicted to activate a T-cell clone, InsB4, that was isolated from a patient with type 1 diabetes and recognised the insulin B-derived epitope HLVEALYLV in the context of disease-risk allele HLA A*0201. InsB4 was shown to kill HLA A*0201⁺ human insulin producing β-cells demonstrating that T-cells with this specificity might contribute to disease. The GPU-accelerated algorithm and multispecies pathogen proteomic databases were validated to discover pathogen-derived peptide sequences that acted as super-agonists for the InsB4 T-cell clone. Peptide-MHC tetramer binding and surface plasmon resonance were used to confirm that the InsB4 TCR bound to the highest-ranked peptide agonists derived from infectious bacteria and fungi. Adoption of GPU-accelerated prediction of T-cell agonists has the capacity to revolutionise our understanding of AD by identifying potential targets for autoimmune T-cells. This approach has further potential for dissecting T-cell responses to infectious disease and cancer.

Flexible Players within the Sheaths: The Intrinsically Disordered Proteins of Myelin in Health and Disease

Myelin ensheathes selected axonal segments within the nervous system, resulting primarily in nerve impulse acceleration, as well as mechanical and trophic support for neurons. In the central and peripheral nervous systems, various proteins that contribute to the formation and stability of myelin are present, which also harbor pathophysiological roles in myelin disease. Many myelin proteins have common attributes, including small size, hydrophobic segments, multifunctionality, longevity, and regions of intrinsic disorder. With recent advances in protein biophysical characterization and bioinformatics, it has become evident that intrinsically disordered proteins (IDPs) are abundant in myelin, and their flexible nature enables multifunctionality. Here, we review known myelin IDPs, their conservation, molecular characteristics and functions, and their disease relevance, along with open questions and speculations. We place emphasis on classifying the molecular details of IDPs in myelin, and we correlate these with their various functions, including susceptibility to post-translational modifications, function in protein–protein and protein–membrane interactions, as well as their role as extended entropic chains. We discuss how myelin pathology can relate to IDPs and which molecular factors are potentially involved.

Immune-mediated genesis of multiple sclerosis

Multiple sclerosis (MS) is widely acknowledged to be an autoimmune disease affecting the neuronal myelin structure of the CNS. Autoantigens recognized as the target of this autoimmune process are: myelin basal protein, anti-proteolipid protein, antimyelin-associated glycoprotein and antimyelin-based oligodendrocytic basic protein. Ample evidence supports the idea of a dysregulation of immunological tolerance towards self-antigens of neuronal myelin structure triggered by one or more viral or bacterial microbial agents in predisposed HLA gene subjects. Genetic predisposition to MS has been highlighted by numerous studies associating the disease to specific HLA haplotypes. Moreover, a wide range of evidence supports the fact that MS may be consequence of one or more viral or bacterial infections such as measles virus, EBV, HHV6, HZV, Chlamydia pneumoniae, Helicobacter Pylori, and other microbial agents. Microbiota elements also seems to have a role on the determinism of the disease as a pathogenic or protective factor. The autoimmune pathogenetic process could arise when a molecular mimicry between a foreign microbial antigen and an auto-antigen occurs in an HLA gene subject competent for that particular antigen. The antigen-presenting cells in this case would induce the activation of a specific Th clone causing a cross-reaction between a foreign antigen and an autoantigen resulting in an autoimmune response.

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A multifactorial ethiopathogenetic model based on immunomediation is a reliable hypothesis for multiple sclerosis.

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Evidence found in the scientific literature makes it possible to reconstruct this etiopathogenetic hypothesis for MS.

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HLA gene predisposition, correlation with infections, molecular mimicry and other immunological data are reported.

High Levels of Epstein-Barr Virus Nuclear Antigen-1-Specific Antibodies and Infectious Mononucleosis Act Both Independently and Synergistically to Increase Multiple Sclerosis Risk

Objective: Elevated levels of anti-EBNA-1 antibodies and infectious mononucleosis (IM) history have consistently been associated with multiple sclerosis (MS) risk. We aimed to study whether these aspects of Epstein–Barr virus (EBV) infection represent separate risk factors for MS and whether they both interact with MS-associated HLA genes in disease development.

Methods: Two Swedish-population-based case–control studies were used, comprising 5,316 cases and 5,431 matched controls. Subjects with different HLA alleles, EBNA-1, and IM status were compared regarding MS risk by calculating odds ratios (OR) with 95% confidence intervals (CI) employing logistic regression. Causal mediation analysis was used to assess to what extent the relationship between IM history and MS risk was mediated by high anti-EBNA-1 antibody levels and vice versa.

Results: The causal mediation analysis revealed that both aspects of EBV infection mainly act directly on MS risk. The direct effect of elevated anti-EBNA-1 antibody levels on MS risk, expressed on the OR scale, was 2.8 (95% CI 2.5–3.1), and the direct effect of IM history on MS risk was 1.7 (95% CI 1.5–2.0). A significant interaction between the two aspects of EBV infection was observed (RERI 1.2, 95% CI 0.3–2.0), accounting for about 50% of the total effect. Further, both aspects of EBV infection interacted with DRB1^*15:01 and absence of A^*02:01.

Interpretation: Elevated anti-EBNA-1 antibody levels and IM history are different risk factors for MS. The two aspects of EBV infection act synergistically to increase MS risk, indicating that they partly are involved in the same biological pathways.

Epstein-Barr Virus in Multiple Sclerosis: Theory and Emerging Immunotherapies

New treatments for multiple sclerosis (MS) focused on B cells have created an atmosphere of excitement in the MS community. B cells are now known to play a major role in disease, demonstrated by the highly impactful effect of a B cell-depleting antibody on controlling MS. The idea that a virus may play a role in the development of MS has a long history and is supported mostly by studies demonstrating a link between B cell-tropic Epstein–Barr virus (EBV) and disease onset. Efforts to develop antiviral strategies for treating MS are underway. Although gaps remain in our understanding of the etiology of MS, the role, if any, of viruses in propagating pathogenic immune responses deserves attention.

HLA DR2b-binding peptides from human endogenous retrovirus envelope, Epstein-Barr virus and brain proteins in the context of molecular mimicry in multiple sclerosis

The aetiology of multiple sclerosis (MS) is as yet poorly understood. Multiple mechanisms in different disease stages are responsible for immunopathology in MS. HLA Class II DR2b (DRB1*1501 β, DRA1*0101 α) is the strongest genetic risk factor for MS. Remnants of ancient retroviruses in the human genome, termed human endogenous retroviruses (HERV), and Epstein-Barr virus (EBV) infection are also associated with MS. In silico analyses of human endogenous retroviral envelope (HERV env) proteins and three myelin proteins that are principal targets of an autoimmune response in MS showed sequence similarities between potential T_H epitopes within pairs of viral and myelin peptides predicted to bind HLA DR2b. This led to the proposal that such molecular mimicry may potentially trigger MS. HLA DR2b binding characteristics of previously identified peptides from the three myelin proteins and HERV env proteins as well as additional in silico predicted peptides from other encephalitogenic brain proteins and EBV proteins were studied to further investigate molecular mimicry. Peptides containing potential T_H epitopes from the myelin oligodendrocyte glycoprotein and HERV env previously predicted to bind HLA DR2b as well as other pertinent potential HLA DR2b-restricted T_H epitopes were confirmed to bind HLA DR2b molecules. Molecular modelling of HLA DR2b in complex with high affinity peptides derived from MOG and HERV env proteins showed that their binding could occur in a similar manner to a HLA DR2b-binding peptide containing a known T_H epitope. A structurally related pair of peptides predicted to bind HLA DR2b from the EBV protein EBNA1 and β synuclein, a brain protein implicated in MS, were also shown to similarly bind HLA DR2b. The findings justify investigating CD4⁺ T cell responses to the identified peptides.

Acute Disseminated Encephalomyelitis in Children: An Updated Review Based on Current Diagnostic Criteria

Acute disseminated encephalomyelitis is an inflammatory disorder of the central nervous system. Uniform diagnostic criteria for acute disseminated encephalomyelitis did not exist until publication of expert-defined consensus definitions by the International Pediatric Multiple Sclerosis Society Group in 2007, with updates in 2013. In the expanding field of pediatric neuroimmunology, consistent diagnostic criteria are essential to correctly categorize patients as increasing information regarding prognosis and management becomes available. Scientific literature is relatively lacking in review articles on International Pediatric Multiple Sclerosis Society Group-defined acute disseminated encephalomyelitis. This review focuses primarily on references applying the International Pediatric Multiple Sclerosis Society Group criteria for acute disseminated encephalomyelitis presenting specific, up-to-date, and translatable information regarding the epidemiology, pathophysiology, clinical features, diagnosis, management, and prognosis of acute disseminated encephalomyelitis in the pediatric population.

Indonesians Human Leukocyte Antigen (HLA) Distributions and Correlations with Global Diseases

In Human, Major Histocompatibility Complex known as Human Leukocyte Antigen (HLA). The HLA grouped into three subclasses regions: the class I region, the class II region, and the class III region. There are thousands of polymorphic HLAs, many of them are proven to have correlations with diseases. Indonesia consists of diverse ethnicity people and populations. It carries a unique genetic diversity between one and another geographical positions. This paper aims to extract Indonesians HLA allele data, mapping the data, and correlating them with global diseases. From the study, it is found that global diseases, like Crohn's disease, rheumatoid arthritis, Graves' disease, gelatin allergy, T1D, HIV, systemic lupus erythematosus, juvenile chronic arthritis, and Mycobacterial disease (tuberculosis and leprosy) suspected associated with the Indonesian HLA profiles.

Viral Infections and Autoimmune Disease: Roles of LCMV in Delineating Mechanisms of Immune Tolerance

Viral infections are a natural part of our existence. They can affect us in many ways that are the result of the interaction between the viral pathogen and our immune system. Most times, the resulting immune response is beneficial for the host. The pathogen is cleared, thus protecting our vital organs with no other consequences. Conversely, the reaction of our immune system against the pathogen can cause organ damage (immunopathology) or lead to autoimmune disease. To date, there are several mechanisms for virus-induced autoimmune disease, including molecular mimicry and bystander activation, in support of the “fertile field” hypothesis (terms defined in our review). In contrast, viral infections have been associated with protection from autoimmunity through mechanisms that include Treg invigoration and immune deviation, in support of the “hygiene hypothesis”, also defined here. Infection with lymphocytic choriomeningitis virus (LCMV) is one of the prototypes showing that the interaction of our immune system with viruses can either accelerate or prevent autoimmunity. Studies using mouse models of LCMV have helped conceive and establish several concepts that we now know and use to explain how viruses can lead to autoimmune activation or induce tolerance. Some of the most important mechanisms established during the course of LCMV infection are described in this short review.

Viral Hormones: Expanding Dimensions in Endocrinology

Viruses have developed different mechanisms to manipulate their hosts, including the process of viral mimicry in which viruses express important host proteins. Until recently, examples of viral mimicry were limited to mimics of growth factors and immunomodulatory proteins. Using a comprehensive bioinformatics approach, we have shown that viruses possess the DNA/RNA with potential to encode 16 different peptides with high sequence similarity to human peptide hormones and metabolically important regulatory proteins. We have characterized one of these families, the viral insulin/IGF-1-like peptides (VILPs), which we identified in four members of the Iridoviridae family. VILPs can bind to human insulin and IGF-1 receptors and stimulate classic postreceptor signaling pathways. Moreover, VILPs can stimulate glucose uptake in vitro and in vivo and stimulate DNA synthesis. DNA sequences of some VILP-carrying viruses have been identified in the human enteric virome. In addition to VILPs, sequences with homology to 15 other peptide hormones or cytokines can be identified in viral DNA/RNA sequences, some with a very high identity to hormones. Recent data by others has identified a peptide that resembles and mimics α-melanocyte-stimulating hormone's anti-inflammatory effects in in vitro and in vivo models. Taken together, these studies reveal novel mechanisms of viral and bacterial pathogenesis in which the microbe can directly target or mimic the host endocrine system. These findings also introduce the concept of a system of microbial hormones that provides new insights into the evolution of peptide hormones, as well as potential new roles of microbial hormones in health and disease.

Immune reconstitution therapy (IRT) in multiple sclerosis: the rationale

Immunotherapy of multiple sclerosis (MS) and other neuroimmune diseases is rapidly evolving. For the past 25 years, there has been an accelerating inclusion of new immunomodulating drugs. Based on their molecular construction and their basic mechanism of action, immunotherapeutic agents belong to the following categories: (1) cytotoxic drugs, (2) synthetic immunomodulators, (3) monoclonal antibodies, (4) vaccines (T cell vaccines, antigen vaccines), (5) oral tolerizing agents, (6) modalities that act as indirect immunosuppressants (plasmapheresis, intravenous immunoglobulins [IVIG]), and (7) cellular therapies. MS immunotherapies may also be classified in a different way, into treatments that are given continuously (chronic treatments) and medications that are applied intermittently (IRTs). The principle behind the latter is depletion of the immune system that allows it to rebuild itself. Upon its reconstitution/resetting, the immune system regains the ability to respond to infections and survey the periphery for cancer. An IRT by definition is given at short intermittent courses and not continuously. IRT modalities were shown to induce long-term remission of MS that, in some cases, is close to the definition of a "cure." There are cohorts of patients having been treated with the IRTs, alemtuzumab, and HSCT, who experience-under these modalities-no evidence of disease activity (NEDA) for over 10 years. Most importantly, IRTs cause radical changes in the lymphocyte repertoire after the reconstitution phase that may explain the long-term beneficial effects of IRT and the possibility of re-induction of self-tolerance to self/myelin antigens. In comparison, a chronic treatment cannot result in cure of the autoimmune reactivity, because it only blocks the immune system, as long as it is given; it cannot therefore radically affect the immunopathogenesis of the disease. The risks of adverse events related to immune suppression (such as opportunistic infections and secondary malignancies) with IRTs are lower and front-loaded, whereas the common side effects of chronic immunomodulation are higher and accumulate with time. In conclusion, IRT provides a novel concept for MS therapy with substantial advantages over chronic immunosuppression. IRT therapies have shown a significantly higher level of efficacy in MS. The "Holy grail" of the treatment of autoimmunity, which is to re-induce the disrupted self-tolerance, seems to be achievable-at least in part-with this approach. Moreover, the benefits of IRT, administered in short pulses, include significantly higher adherence to treatment and lower risks for accumulative side effects that are typically associated with chronic immunosuppression.

Epstein-Barr virus infection as a predisposing factor for multiple sclerosis. An update from molecular biology, immunology and epidemiology

Introduction: Epstein-Barr virus is an infectious agent used to immortalize and induce polyclonal activation of B cells. It has been widely described that this virus produces changes in the cells it infects and in the immune response, and stimulates the development of autoimmune diseases.Objective: To characterize the association between Epstein-Barr virus and multiple sclerosis described in current scientific literature.Materials and methods: A 59-years range literature search was conducted in the PubMed, ScienceDirect, Redalyc and SciELO databases using the following MeSH terms: “Epstein-Barr virus, multiple sclerosis autoimmune diseases, autoimmune diseases of the nervous system”.Results: Many studies describe the association between Epstein-Barr virus and multiple sclerosis. It is believed that acute infection and viral reactivation promote the development of multiple sclerosis.Conclusions: It is necessary to conduct further research on the pathogenesis and morphophysiological and neuroimmunological changes –at the ecological, molecular, cellular, tissue, organic and systemic level– induced by the immune response and that favor the development of multiple sclerosis.

Resiquimod-Mediated Activation of Plasmacytoid Dendritic Cells Is Amplified in Multiple Sclerosis

Background: Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system. The cause of multiple sclerosis is unknown but there are several evidences that associate the genetic basis of the disease with environmental causes. An important association between viral infection and development of MS is clearly demonstrated. Viruses have a strong impact on innate immune cells. In particular, myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs), are able to respond to viruses and to activate the adaptive immune response. Methods: In this study we mimic viral infection using synthetic single-strand RNA, Resiquimod, and we compared the response of both DC subsets derived from healthy donors and MS patients by characterizing the expression of costimulatory molecules on the DC surface. Results: We found that pDCs from MS patients express higher levels of OX40-L, HLA-DR, and CD86 than healthy donors. Moreover, we found that blood cells from MS patients and healthy donors upon Resiquimod-stimulation are enriched in a subpopulation of pDCs, characterized by a high amount of costimulatory molecules. Conclusion: Overall, these results indicate that activation of pDCs is enhanced in MS, likely due to a latent viral infection, and that costimulatory molecules expressed on pDCs could mediate a protective response against the viral trigger of autoimmunity.

Development of a dual-functional conjugate of antigenic peptide and Fc-III mimetics (DCAF) for targeted antibody blocking

Targeted antibody blocking enables characterization of binding sites on immunoglobulin G (IgG), and can efficiently eliminate harmful antibodies from organisms. In this report, we present a novel peptide-denoted as a dual-functional conjugate of antigenic peptide and Fc-III mimetics (DCAF)-for targeted blocking of antibodies. Synthesis of DCAF was achieved by native chemical ligation, and the molecule consists of three functional parts: a specific antigenic peptide, a linker and the Fc-III mimetic peptide, which has a high affinity toward the Fc region of IgG molecules. We demonstrate that DCAF binds the cognate antibody with high selectivity by simultaneously binding to the Fab and Fc regions of IgG. Animal experiments revealed that DCAF molecules diminish the antibody-dependent enhancement effect in a dengue virus infection model, and rescue the acetylcholine receptor by inhibiting the complement cascade in a myasthenia gravis model. These results suggest that DCAFs could have utility in the development of new therapeutics against harmful antibodies.

Difference in Pathomechanism Between Crohn's Disease and Ulcerative Colitis Revealed by Colon Transcriptome

BACKGROUND

We aim to identify the differences in colonic mucosal transcriptome between Crohn's disease (CD) and ulcerative colitis (UC) for a better understanding of the molecular pathology.

METHODS

Differentially expressed genes (DEG) in the colonic mucosa of CD and UC were identified with a global gene expression microarray dataset generated from the colon biopsies of CD and UC patients and normal controls. The DEGs were then processed to identify altered pathways and modularized DEGs and pathways. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis with an independent cohort of samples was performed to validate the microarray data.

RESULTS

At the pathway level, virus infection and autoimmune pathways were upregulated in CD but not in UC when compared with controls. Some of the relevant DEGs (such as TAP1 and TAP2) were elevated in both CD and UC, with CD exhibiting more pronounced elevations. Gene expression levels in viral infection pathways were correlated with those of autoimmune pathways. In contrast, pattern recognition-mediated innate immune pathways (TLR4 and TLR2) were significantly elevated in UC but not in CD. Similar results were observed with an independent cohort by qRT-PCR.

CONCLUSIONS

Our data support the hypothesis that viral infection induced autoimmunity may represent a pathomechanism for IBD, especially CD. However, pattern recognition-mediated innate immunity targeting microbiome may play a more important role in UC compared with CD. Our findings identified different intervention targets for CD and UC, which may lead to more effective treatments for IBD patients.

Herpes Simplex Virus Type 1 Infection of the Central Nervous System: Insights Into Proposed Interrelationships With Neurodegenerative Disorders

Herpes simplex virus type 1 (HSV-1) is highly prevalent in humans and can reach the brain without evident clinical symptoms. Once in the central nervous system (CNS), the virus can either reside in a quiescent latent state in this tissue, or eventually actively lead to severe acute necrotizing encephalitis, which is characterized by exacerbated neuroinflammation and prolonged neuroimmune activation producing a life-threatening disease. Although HSV-1 encephalitis can be treated with antivirals that limit virus replication, neurological sequelae are common and the virus will nevertheless remain for life in the neural tissue. Importantly, there is accumulating evidence that suggests that HSV-1 infection of the brain both, in symptomatic and asymptomatic individuals could lead to neuronal damage and eventually, neurodegenerative disorders. Here, we review and discuss acute and chronic infection of particular brain regions by HSV-1 and how this may affect neuron and cognitive functions in the host. We review potential cellular and molecular mechanisms leading to neurodegeneration, such as protein aggregation, dysregulation of autophagy, oxidative cell damage and apoptosis, among others. Furthermore, we discuss the impact of HSV-1 infection on brain inflammation and its potential relationship with neurodegenerative diseases.

Human Anti-fungal Th17 Immunity and Pathology Rely on Cross-Reactivity against Candida albicans

Th17 cells provide protection at barrier tissues but may also contribute to immune pathology. The relevance and induction mechanisms of pathologic Th17 responses in humans are poorly understood. Here, we identify the mucocutaneous pathobiont Candida albicans as the major direct inducer of human anti-fungal Th17 cells. Th17 cells directed against other fungi are induced by cross-reactivity to C. albicans. Intestinal inflammation expands total C. albicans and cross-reactive Th17 cells. Strikingly, Th17 cells cross-reactive to the airborne fungus Aspergillus fumigatus are selectively activated and expanded in patients with airway inflammation, especially during acute allergic bronchopulmonary aspergillosis. This indicates a direct link between protective intestinal Th17 responses against C. albicans and lung inflammation caused by airborne fungi. We identify heterologous immunity to a single, ubiquitous member of the microbiota as a central mechanism for systemic induction of human anti-fungal Th17 responses and as a potential risk factor for pulmonary inflammatory diseases.

Why Don't We Have a Vaccine Against Autoimmune Diseases? - A Review

This review examines some of the reasons why we don't have a vaccine against autoimmune diseases and highlights the progress that has been made. Many autoimmune diseases, such as rheumatoid arthritis (RA), multiple sclerosis (MS) and type 1 diabetes (T1D), are driven by autoimmune T cell responses. Unlike vaccines for most infectious diseases, which elicit antibody responses, are intended for immuno-naive individuals and considered preventative, a vaccine for an autoimmune disease must be therapeutic and resolve or control the on-going autoimmune response and condition in the diseased host. Despite these differences, many of the same considerations for infectious disease vaccines must also be addressed to develop a therapeutic vaccine for autoimmune diseases. The disease initiator/triggers, antigens and autoantigens, nature of the immunopathogenic and protective/therapeutic immune response will be compared for infectious and autoimmune diseases as will approaches for developing vaccines including formulations, animal models and indicators of success. The rationale for a therapeutic vaccine for RA will be discussed in greater detail with a relatively limited discussion of T1D, MS and other autoimmune diseases.

HPV vaccines and lupus: current approaches towards preventing adverse immune cross-reactivity

INTRODUCTION

If not properly treated, human papillomavirus (HPV) infection may evolve from a common sexually transmitted disease to genital warts and cervical cancer. Various prophylactic HPV vaccines (HPVv), approved to reduce the incidence of the infection, have been found to be effective and safe; however, accounts of post-vaccination autoimmune phenomena, including systemic lupus erythematosus (SLE), have been reported in genetically susceptible individuals.

AREAS COVERED

Infectious agents play a role in breaking the immunologic tolerance to self-antigens, resulting in autoimmune events. There is molecular evidence supporting the involvement of HPV in SLE, with a high prevalence of L1 HPV peptide homology to proteins being associated with SLE. Therefore, approaches in vaccine preparations aiming to prevent adverse immune cross-reactivity are sought. Performing a broad search of the literature, we review the association between SLE, HPV, and HPVv, with a focus on the mechanisms of molecular mimicry and cross-reactivity, and the approaches currently being elaborated towards preventing such phenomena.

EXPERT COMMENTARY

The advantages of using low-similarity peptide antigens may be two-fold, abolishing the risk of cross-reactivity and eliminating the vaccine adjuvantation procedure. Vaccines based on pathogen unique sequences would provide effective vaccine preparation while curbing the risk for the human host.

Class II MHC antigen processing in immune tolerance and inflammation

Presentation of peptide antigens by MHC-II proteins is prerequisite to effective CD4 T cell tolerance to self and to recognition of foreign antigens. Antigen uptake and processing pathways as well as expression of the peptide exchange factors HLA-DM and HLA-DO differ among the various professional and non-professional antigen-presenting cells and are modulated by cell developmental state and activation. Recent studies have highlighted the importance of these cell-specific factors in controlling the source and breadth of peptides presented by MHC-II under different conditions. During inflammation, increased presentation of selected self-peptides has implications for maintenance of peripheral tolerance and autoimmunity.

Long non-coding RNA: its evolutionary relics and biological implications in mammals: a review

The central dogma of gene expression propounds that DNA is transcribed to mRNA and finally gets translated into protein. Only 2–3% of the genomic DNA is transcribed to protein-coding mRNA. Interestingly, only a further minuscule part of genomic DNA encodes for long non-coding RNAs (lncRNAs) which are characteristically more than 200 nucleotides long and can be transcribed from both protein-coding (e.g. H19 and TUG1) as well as non-coding DNA by RNA polymerase II. The lncRNAs do not have open reading frames (with some exceptions), 3`-untranslated regions (3’-UTRs) and necessarily these RNAs lack any translation-termination regions, however, these can be spliced, capped and polyadenylated as mRNA molecules. The flexibility of lncRNAs confers them specific 3D-conformations that eventually enable the lncRNAs to interact with proteins, DNA or other RNA molecules via base pairing or by forming networks. The lncRNAs play a major role in gene regulation, cell differentiation, cancer cell invasion and metastasis and chromatin remodeling. Deregulation of lncRNA is also responsible for numerous diseases in mammals. Various studies have revealed their significance as biomarkers for prognosis and diagnosis of cancer. The aim of this review is to overview the salient features, evolution, biogenesis and biological importance of these molecules in the mammalian system.

Infectious agents and different course of multiple sclerosis: a systematic review

Multiple sclerosis (MS) causes demyelination of white matter of central nervous system and neuro-degeneration due to inflammation. Different types of MS, as well as disease progression, come with different pathology and pathophysiology. The objective of this study was to evaluate the possible association between different micro-organisms and the relapse or progression of MS. Studies indexed in Medline/PMC, Scopus and Web of Science published without time and language limitation until March 2017 were identified through the search terms "infection" or "infectious" and "multiple sclerosis". A total of 20878 abstracts were identified through the initial search terms. Selection of articles and assessment of their quality was done based on Cochrane library guidelines. Full texts were reviewed for 33 articles out of which 14 articles met the criteria for inclusion. Different micro-organisms are known to play roles in the pathogenesis of MS and its relapse; including Human herpesvirus 6 (HHV-6), Human herpesvirus 7 (HHV-7), Epstein-Barr virus (EBV), Chlamydia pneumoniae and Torque teno virus (TTV). But in this review only HHV-6, C. pneumoniae and TTV have been considered to play a role in disease progression in some studies and not all of them. This review concluded that some micro-organisms such as HHV-6, C. pneumoniae and TTV have been considered as cofactors to make MS a progressive type. It should be considered that these findings do not necessarily rule out the role of other pathogens in MS progression but may represent population differences or different sensitivity of the technique used.

Memory B Cells Activate Brain-Homing, Autoreactive CD4+ T Cells in Multiple Sclerosis

Multiple sclerosis is an autoimmune disease that is caused by the interplay of genetic, particularly the HLA-DR15 haplotype, and environmental risk factors. How these etiologic factors contribute to generating an autoreactive CD4⁺ T cell repertoire is not clear. Here, we demonstrate that self-reactivity, defined as “autoproliferation” of peripheral Th1 cells, is elevated in patients carrying the HLA-DR15 haplotype. Autoproliferation is mediated by memory B cells in a HLA-DR-dependent manner. Depletion of B cells in vitro and therapeutically in vivo by anti-CD20 effectively reduces T cell autoproliferation. T cell receptor deep sequencing showed that in vitro autoproliferating T cells are enriched for brain-homing T cells. Using an unbiased epitope discovery approach, we identified RASGRP2 as target autoantigen that is expressed in the brain and B cells. These findings will be instrumental to address important questions regarding pathogenic B-T cell interactions in multiple sclerosis and possibly also to develop novel therapies.

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Autoproliferation of CD4⁺ T cells and B cells is involved in multiple sclerosis

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The main genetic factor of MS, HLA-DR15, plays a central role in autoproliferation

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Memory B cells drive autoproliferation of Th1 brain-homing CD4⁺ T cells

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Autoproliferating T cells recognize antigens expressed in B cells and brain lesions

Vaccine-induced autoimmunity: the role of molecular mimicry and immune crossreaction

Since the early 1800s vaccines have saved numerous lives by preventing lethal infections. However, during the past two decades, there has been growing awareness of possible adverse events associated with vaccinations, cultivating heated debates and leading to significant fluctuations in vaccination rates. It is therefore pertinent for the scientific community to seriously address public concern of adverse effects of vaccines to regain public trust in these important medical interventions. Such adverse reactions to vaccines may be viewed as a result of the interaction between susceptibility of the vaccinated subject and various vaccine components. Among the implicated mechanisms for these reactions is molecular mimicry. Molecular mimicry refers to a significant similarity between certain pathogenic elements contained in the vaccine and specific human proteins. This similarity may lead to immune crossreactivity, wherein the reaction of the immune system towards the pathogenic antigens may harm the similar human proteins, essentially causing autoimmune disease. In this review, we address the concept of molecular mimicry and its application in explaining post vaccination autoimmune phenomena. We further review the principal examples of the influenza, hepatitis B, and human papilloma virus vaccines, all suspected to induce autoimmunity via molecular mimicry. Finally, we refer to possible implications on the potential future development of better, safer vaccines.

Impacts of microbiome metabolites on immune regulation and autoimmunity

A vast number of studies have demonstrated a remarkable role for the gut microbiota and their metabolites in the pathogenesis of inflammatory diseases, including multiple sclerosis (MS). Recent studies in experimental autoimmune encephalomyelitis, an animal model of MS, have revealed that modifying certain intestinal bacterial populations may influence immune cell priming in the periphery, resulting in dysregulation of immune responses and neuroinflammatory processes in the central nervous system (CNS). Conversely, some commensal bacteria and their antigenic products can protect against inflammation within the CNS. Specific components of the gut microbiome have been implicated in the production of pro-inflammatory cytokines and subsequent generation of Th17 cells. Similarly, commensal bacteria and their metabolites can also promote the generation of regulatory T-cells (Treg), contributing to immune suppression. Short-chain fatty acids may induce Treg either by G-protein-coupled receptors or inhibition of histone deacetylases. Tryptophan metabolites may suppress inflammatory responses by acting on the aryl hydrocarbon receptor in T-cells or astrocytes. Interestingly, secretion of these metabolites can be impaired by excess consumption of dietary components, such as long-chain fatty acids or salt, indicating that the diet represents an environmental factor affecting the complex crosstalk between the gut microbiota and the immune system. This review discusses new aspects of host-microbiota interaction and the immune system with a special focus on MS as a prototype T-cell-mediated autoimmune disease of the CNS.

Herpesviruses: Harmonious Pathogens but Relevant Cofactors in Other Diseases?

Most vertebrates are infected with one or more herpesviruses and remain so for the rest of their lives. The relationship of immunocompetent healthy host with herpesviruses may sometime be considered as harmonious. However, clinically severe diseases can occur when host immunity is compromised due to aging, during some stress response, co-infections or during neoplastic disease conditions. Discord can also occur during iatrogenic immunosuppression used for controlling graft rejection, in some primary genetic immunodeficiencies as well as when the virus infects a non-native host. In this review, we discuss such issues and their influence on host-herpesvirus interaction.

Microbiota epitope similarity either dampens or enhances the immunogenicity of disease-associated antigenic epitopes

The microbiome influences adaptive immunity and molecular mimicry influences T cell reactivity. Here, we evaluated whether the sequence similarity of various antigens to the microbiota dampens or increases immunogenicity of T cell epitopes. Sets of epitopes and control sequences derived from 38 antigenic categories (infectious pathogens, allergens, autoantigens) were retrieved from the Immune Epitope Database (IEDB). Their similarity to microbiome sequences was calculated using the BLOSUM62 matrix. We found that sequence similarity was associated with either dampened (tolerogenic; e.g. most allergens) or increased (inflammatory; e.g. Dengue and West Nile viruses) likelihood of a peptide being immunogenic as a function of epitope source category. Ten-fold cross-validation and validation using sets of manually curated epitopes and non-epitopes derived from allergens were used to confirm these initial observations. Furthermore, the genus from which the microbiome homologous sequences were derived influenced whether a tolerogenic versus inflammatory modulatory effect was observed, with Fusobacterium most associated with inflammatory influences and Bacteroides most associated with tolerogenic influences. We validated these effects using PBMCs stimulated with various sets of microbiome peptides. "Tolerogenic" microbiome peptides elicited IL-10 production, "inflammatory" peptides elicited mixed IL-10/IFNγ production, while microbiome epitopes homologous to self were completely unreactive for both cytokines. We also tested the sequence similarity of cockroach epitopes to specific microbiome sequences derived from households of cockroach allergic individuals and non-allergic controls. Microbiomes from cockroach allergic households were less likely to contain sequences homologous to previously defined cockroach allergens. These results are compatible with the hypothesis that microbiome sequences may contribute to the tolerization of T cells for allergen epitopes, and lack of these sequences might conversely be associated with increased likelihood of T cell reactivity against the cockroach epitopes. Taken together this study suggests that microbiome sequence similarity influences immune reactivity to homologous epitopes encoded by pathogens, allergens and auto-antigens.

Lipids hide or step aside for CD1-autoreactive T cell receptors

Peptide and lipid antigens are presented to T cells when bound to MHC or CD1 proteins, respectively. The general paradigm of T cell antigen recognition is that T cell receptors (TCRs) co-recognize an epitope comprised of the antigen and antigen presenting molecule. Here we review the latest studies in which T cells operate outside the co-recognition paradigm: TCRs can broadly contact CD1 itself, but not the carried lipid. The essential structural feature in these new mechanisms is a large 'antigen free' zone on the outer surface of certain antigen presenting molecules. Whereas peptides dominate the exposed surface of MHC-peptide complexes, all human CD1 proteins have a closed, antigen-free surface, which is known as the A' roof. These new structural models help to interpret recent biological studies of CD1 autoreactive T cells in vivo, which have now been broadly observed in studies on TCR-transgenic mice, healthy humans and patients with autoimmune disease.

Environmental factors in the development of multiple sclerosis

Epidemiology of Multiple Sclerosis (MS) has been intensively studied and we know now that its occurrence result from the combined action of genetic and environmental factors. There are significant geographic and temporal variations in MS incidence and the risk associated with the development of MS may be affected by many potential factors (including infections, climate, diet, etc.). But none of these factors has been identified as "causal". The accumulation of these different agents as well as their interactions probably contribute to the development of the disease.

Respiratory virus-induced heterologous immunity: Part of the problem or part of the solution?

Purpose

To provide current knowledge on respiratory virus-induced heterologous immunity (HI) with a focus on humoral and cellular cross-reactivity. Adaptive heterologous immune responses have broad implications on infection, autoimmunity, allergy and transplant immunology. A better understanding of the mechanisms involved might ultimately open up possibilities for disease prevention, for example by vaccination.

Methods

A structured literature search was performed using Medline and PubMed to provide an overview of the current knowledge on respiratory-virus induced adaptive HI.

Results

In HI the immune response towards one antigen results in an alteration of the immune response towards a second antigen. We provide an overview of respiratory virus-induced HI, including viruses such as respiratory syncytial virus (RSV), rhinovirus (RV), coronavirus (CoV) and influenza virus (IV). We discuss T cell receptor (TCR) and humoral cross-reactivity as mechanisms of HI involving those respiratory viruses. Topics covered include HI between respiratory viruses as well as between respiratory viruses and other pathogens. Newly developed vaccines, which have the potential to provide protection against multiple virus strains are also discussed. Furthermore, respiratory viruses have been implicated in the development of autoimmune diseases, such as narcolepsy, Guillain-Barré syndrome, type 1 diabetes or myocarditis. Finally, we discuss the role of respiratory viruses in asthma and the hygiene hypothesis, and review our recent findings on HI between IV and allergens, which leads to protection from experimental asthma.

Conclusion

Respiratory-virus induced HI may have protective but also detrimental effects on the host. Respiratory viral infections contribute to asthma or autoimmune disease development, but on the other hand, a lack of microbial encounter is associated with an increasing number of allergic as well as autoimmune diseases. Future research might help identify the elements which determine a protective or detrimental outcome in HI-based mechanisms.

Galectin-3 deficiency drives lupus-like disease by promoting spontaneous germinal centers formation via IFN-γ

Germinal centers (GC) are important sites for high-affinity and long-lived antibody induction. Tight regulation of GC responses is critical for maintaining self-tolerance. Here, we show that Galectin-3 (Gal-3) is involved in GC development. Compared with WT mice, Gal-3 KO mice have more GC B cells and T follicular helper cells, increased percentages of antibody-secreting cells and higher concentrations of immunoglobulins and IFN-γ in serum, and develop a lupus-like disease. IFN-γ blockade in Gal-3 KO mice reduces spontaneous GC formation, class-switch recombination, autoantibody production and renal pathology, demonstrating that IFN-γ overproduction sustains autoimmunity. The results from chimeric mice show that intrinsic Gal-3 signaling in B cells controls spontaneous GC formation. Taken together, our data provide evidence that Gal-3 acts directly on B cells to regulate GC responses via IFN-γ and implicate the potential of Gal-3 as a therapeutic target in autoimmunity.

Germinal center (GC) is where B cells interact with other immune cells for optimal induction of antibody responses. Here the authors show that galectin-3 regulates GC development by modulating interferon-γ and B cell-intrinsic signaling, such that galectin-3 deficiency mice exhibit lupus-like autoimmune symptoms.

Respiratory virus-induced heterologous immunity: Part of the problem or part of the solution?

Purpose

To provide current knowledge on respiratory virus-induced heterologous immunity (HI) with a focus on humoral and cellular cross-reactivity. Adaptive heterologous immune responses have broad implications on infection, autoimmunity, allergy and transplant immunology. A better understanding of the mechanisms involved might ultimately open up possibilities for disease prevention, for example by vaccination.

Methods

A structured literature search was performed using Medline and PubMed to provide an overview of the current knowledge on respiratory-virus induced adaptive HI.

Results

In HI the immune response towards one antigen results in an alteration of the immune response towards a second antigen. We provide an overview of respiratory virus-induced HI, including viruses such as respiratory syncytial virus (RSV), rhinovirus (RV), coronavirus (CoV) and influenza virus (IV). We discuss T cell receptor (TCR) and humoral cross-reactivity as mechanisms of HI involving those respiratory viruses. Topics covered include HI between respiratory viruses as well as between respiratory viruses and other pathogens. Newly developed vaccines which have the potential to provide protection against multiple virus strains are also discussed. Furthermore, respiratory viruses have been implicated in the development of autoimmune diseases, such as narcolepsy, Guillain–Barré syndrome, type 1 diabetes or myocarditis. Finally, we discuss the role of respiratory viruses in asthma and the hygiene hypothesis, and review our recent findings on HI between IV and allergens, which leads to protection from experimental asthma.

Conclusion

Respiratory-virus induced HI may have protective but also detrimental effects on the host. Respiratory viral infections contribute to asthma or autoimmune disease development, but on the other hand, a lack of microbial encounter is associated with an increasing number of allergic as well as autoimmune diseases. Future research might help identify the elements which determine a protective or detrimental outcome in HI-based mechanisms.

Bone morphogenetic proteins in multiple sclerosis: Role in neuroinflammation

Bone morphogenetic proteins (BMPs) are growth factors that represent the largest subgroup of signalling ligands of the transforming growth factor beta (TGF-β) superfamily. Their participation in the proliferation, survival and cell fate of several cell types and their involvement in many pathological conditions are now well known. BMP expression is altered in multiple sclerosis (MS) patients, suggesting that BMPs have a role in the pathogenesis of this disease. MS is a demyelinating and neurodegenerative autoimmune disorder of the central nervous system (CNS). MS is a complex pathological condition in which genetic, epigenetic and environmental factors converge, although its aetiology remains elusive. Multifunctional molecules, such as BMPs, are extremely interesting in the field of MS because they are involved in the regulation of several adult tissues, including the CNS and the immune system. In this review, we discuss the extensive data available regarding the role of BMP signalling in neuronal progenitor/stem cell fate and focus on the participation and expression of BMPs in CNS demyelination. Additionally, we provide an overview of the involvement of BMPs as modulators of the immune system, as this subject has not been thoroughly explored even though it is of great interest in autoimmune disorders. Moreover, we describe the data on BMP signalling in autoimmunity and inflammatory diseases, including MS and its experimental models. Thus, we aim to provide an integrated view of the putative role of BMPs in MS pathogenesis and to open the field for the further development of alternative therapeutic strategies for MS patients.

HLA variation and disease

Fifty years since the first description of an association between HLA and human disease, HLA molecules have proven to be central to physiology, protective immunity and deleterious, disease-causing autoimmune reactivity. Technological advances have enabled pivotal progress in the determination of the molecular mechanisms that underpin the association between HLA genetics and functional outcome. Here, we review our current understanding of HLA molecules as the fundamental platform for immune surveillance and responsiveness in health and disease. We evaluate the scope for personalized antigen-specific disease prevention, whereby harnessing HLA-ligand interactions for clinical benefit is becoming a realistic prospect.

The "Gut Feeling": Breaking Down the Role of Gut Microbiome in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic neuroinflammatory disease of the central nervous system with unknown etiology. Recently, the gut microbiota has emerged as a potential factor in the development of MS, with a number of studies having shown that patients with MS exhibit gut dysbiosis. The gut microbiota helps the host remain healthy by regulating various functions, including food metabolism, energy homeostasis, maintenance of the intestinal barrier, inhibition of colonization by pathogenic organisms, and shaping of both mucosal and systemic immune responses. Alteration of the gut microbiota, and subsequent changes in its metabolic network that perturb this homeostasis, may lead to intestinal and systemic disorders such as MS. Here we discuss the findings of recent MS microbiome studies and potential mechanisms through which gut microbiota can predispose to, or protect against, MS. These findings highlight the need of an improved understanding of the interactions between the microbiota and host for developing therapies based on gut commensals with which to treat MS.