Enhancement of EAE and induction of autoantibodies to T-cell epitopes in mice infected with a recombinant vaccinia virus encoding myelin proteolipid protein

Bioinformatics Analysis of Gut Microbiota and CNS Transcriptome in Virus-Induced Acute Myelitis and Chronic Inflammatory Demyelination; Potential Association of Distinct Bacteria With CNS IgA Upregulation

Virus infections have been associated with acute and chronic inflammatory central nervous system (CNS) diseases, e.g., acute flaccid myelitis (AFM) and multiple sclerosis (MS), where animal models support the pathogenic roles of viruses. In the spinal cord, Theiler's murine encephalomyelitis virus (TMEV) induces an AFM-like disease with gray matter inflammation during the acute phase, 1 week post infection (p.i.), and an MS-like disease with white matter inflammation during the chronic phase, 1 month p.i. Although gut microbiota has been proposed to affect immune responses contributing to pathological conditions in remote organs, including the brain pathophysiology, its precise role in neuroinflammatory diseases is unclear. We infected SJL/J mice with TMEV; harvested feces and spinal cords on days 4 (before onset), 7 (acute phase), and 35 (chronic phase) p.i.; and examined fecal microbiota by 16S rRNA sequencing and CNS transcriptome by RNA sequencing. Although TMEV infection neither decreased microbial diversity nor changed overall microbiome patterns, it increased abundance of individual bacterial genera Marvinbryantia on days 7 and 35 p.i. and Coprococcus on day 35 p.i., whose pattern-matching with CNS transcriptome showed strong correlations: Marvinbryantia with eight T-cell receptor (TCR) genes on day 7 and with seven immunoglobulin (Ig) genes on day 35 p.i.; and Coprococcus with gene expressions of not only TCRs and IgG/IgA, but also major histocompatibility complex (MHC) and complements. The high gene expression of IgA, a component of mucosal immunity, in the CNS was unexpected. However, we observed substantial IgA positive cells and deposition in the CNS, as well as a strong correlation between CNS IgA gene expression and serum anti-TMEV IgA titers. Here, changes in a small number of distinct gut bacteria, but not overall gut microbiota, could affect acute and chronic immune responses, causing AFM- and MS-like lesions in the CNS. Alternatively, activated immune responses would alter the composition of gut microbiota.

The role of B cells in multiple sclerosis: Current and future therapies

While it was long held that T cells were the primary mediators of multiple sclerosis (MS) pathogenesis, the beneficial effects observed in response to treatment with Rituximab (RTX), a monoclonal antibody (mAb) targeting CD20, shed light on a key contributor to MS that had been previously underappreciated: B cells. This has been reaffirmed by results from clinical trials testing the efficacy of subsequently developed B cell-depleting mAbs targeting CD20 as well as studies revisiting the effects of previous disease-modifying therapies (DMTs) on B cell subsets thought to modulate disease severity. In this review, we summarize current knowledge regarding the complex roles of B cells in MS pathogenesis and current and potential future B cell-directed therapies.

Evidence for the role of B cells and immunoglobulins in the pathogenesis of multiple sclerosis

The pathogenesis of multiple sclerosis (MS) remains elusive. Recent reports advocate greater involvement of B cells and immunoglobulins in the initiation and propagation of MS lesions at different stages of their ontogeny. The key role of B cells and immunoglobulins in pathogenesis was initially identified by studies in which patients whose fulminant attacks of demyelination did not respond to steroids experienced remarkable functional improvement following plasma exchange. The positive response to Rituximab in Phase II clinical trials of relapsing-remitting MS confirms the role of B cells. The critical question is how B cells contribute to MS. In this paper, we discuss both the deleterious and the beneficial roles of B cells and immunoglobulins in MS lesions. We provide alternative hypotheses to explain both damaging and protective antibody responses.

Experimental autoimmune encephalomyelitis as a testing paradigm for adjuvants and vaccines

Experimental autoimmune encephalomyelitis (EAE) is an experimental model for multiple sclerosis. EAE can be induced by inoculation with central nervous system (CNS) proteins or peptides emulsified in complete Freund's adjuvant. Protection from EAE, enhancement of EAE or subclinical priming for EAE can occur as a result of either live viral infection or DNA immunization with molecular mimics of CNS proteins or peptides. Here we review the published data describing modulation of EAE through administration of various CNS proteins/peptides introduced via live virus or plasmid DNA and modulation of EAE through choice of adjuvant (immunostimulating agents).

Studies in the modulation of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), an experimental model for multiple sclerosis, can be induced through inoculation with several different central nervous system (CNS) proteins or peptides. Modulation of EAE, resulting in either protection from EAE or enhancement of EAE, can also be accomplished through either vaccination or DNA immunization with molecular mimics of self-CNS proteins. Previously published data on this method of EAE modulation will be reviewed. New data is presented, which demonstrates that EAE can also be modulated through the administration of the beta-(1,3)-D-glucan, curdlan. Dendritic cells stimulated by curdlan are involved in the differentiation of the interleukin-17 producing subset of CD4(+) T cells that are recognized effector cells in EAE. Using two different systems to study the effects of curdlan on EAE, it was found that curdlan increased the incidence of EAE and/or the severity of the disease course.

Potential triggers of MS

MS is an immune mediated disease of the central nervous system (CNS) characterized by demyelination, axonal damage and neurologic disability. The primary cause of this CNS disease remains elusive. Here we will address our current understanding of the role of viruses as potential environmental triggers for MS. Virus infections can act peripherally (outside the CNS) or within the CNS. The association of viral infections with demyelinating disease, in both animals and humans, will be discussed, as will the potential contributions of peripheral infection with Torque Teno virus, infection outside of and/or within the CNS with Epstein-Barr virus and infection within the CNS with Human Herpesvirus 6 to MS. An experimental animal model, Theiler's murine encephalomyelitis virus infection of susceptible strains of mice is an example of viral infections of the CNS as a prerequisite for demyelination. Finally, the proposition that multiple virus infections are required, which first prime the immune system and then trigger the disease, as a model where infections outside of the CNS lead to inflammatory changes within the CNS, for the development of a MS-like disease is explored.

B cells and antibodies in MS

Increasing research activities on humoral immune responses involved in the immunopathogenesis of multiple sclerosis (MS) led to a revival of the importance of B cells and antibodies in MS. B cells seem now to play various immunopathogenetic roles in the initiation and propagation of inflammatory demyelinating processes at different disease stages of MS. The biological activities of antibodies in MS is, in general, still less known, although it emerges that antibodies are specifically involved in demyelination or, at least, mirror tissue destruction in the central nervous system. Finally, there is growing evidence that treatments, which specifically target B cells and/or antibodies, are effective in MS and its variants neuromyelitis optica (NMO). This chapter therefore aims to summarize the present knowledge and to outline future directions about the role of B cells and antibodies in research and therapy of MS and NMO.

Immunological basis for the development of tissue inflammation and organ-specific autoimmunity in animal models of multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is an animal model for multiple sclerosis (MS) that has shaped our understanding of autoimmune tissue inflammation in the central nervous system (CNS). Major therapeutic approaches to MS have been first validated in EAE. Nevertheless, EAE in all its modifications is not able to recapitulate the full range of clinical and histopathogenic aspects of MS. Furthermore, autoimmune reactions in EAE-prone rodent strains and MS patients may differ in terms of the relative involvement of various subsets of immune cells. However, the role of specific molecules that play a role in skewing the immune response towards pathogenic autoreactivity is very similar in mice and humans. Thus, in this chapter, we will focus on the identification of a novel subset of inflammatory T cells, called Th17 cells, in EAE and their interplay with other immune cells including protective regulatory T cells (T-regs). It is likely that the discovery of Th17 cells and their relationship with T-regs will change our understanding of organ-specific autoimmune diseases in the years to come.

Targeting myelin proteolipid protein to the MHC class I pathway by ubiquitination modulates the course of experimental autoimmune encephalomyelitis

Relapsing-remitting experimental autoimmune encephalomyelitis (EAE), a multiple sclerosis model, is induced in mice by injection of myelin proteolipid protein (PLP) encephalitogenic peptide, PLP139-151, in adjuvant. In this study, prior to EAE induction, mice were vaccinated with a bacterial plasmid encoding a PLP-ubiquitin fusion (pCMVUPLP). During the relapse phase of EAE, clinical signs, histopathologic changes, in vitro lymphoproliferation to PLP139-151 and interferon-gamma levels were reduced in pCMVUPLP-vaccinated mice, compared to mock-vaccinated mice (controls). Lymphocytes from pCMVUPLP-vaccinated mice produced interleukin-4, a cytokine lacking in controls. Thus, pCMVUPLP vaccination can modulate the relapse after EAE induction.

Differential effects of the type I interferons alpha4, beta, and epsilon on antiviral activity and vaccine efficacy

The type I IFNs exert a range of activities that include antiviral, antiproliferative, and immunomodulatory effects. To study this further, we have constructed recombinant vaccinia viruses expressing HIV or hemagglutinin (HA) Ags along with murine type I IFNs, IFN-alpha(4) (HA-VV-IFN-alpha(4)), IFN-beta (HA-VV-IFN-beta), or IFN-epsilon (HIV-VV-IFN-epsilon), a recently discovered member of this family. Our aims were to characterize IFN-epsilon functionality as a type I IFN and also to study the biological properties of these factors toward the development of safer and more effective vector-based vaccines. HIV-VV-IFN-epsilon and HA-VV-IFN-beta grew to lower titers than did their parental controls in murine cell lines. In vivo, however, HIV-VV-IFN-epsilon growth was not attenuated, while IFN-beta demonstrated potent local antiviral activity with no replication of HA-VV-IFN-beta detected. Flow cytofluorometric analysis of B lymphocytes incubated with virally encoded IFN-epsilon showed up-regulation of activation markers CD69 and CD86, while RT-PCR of IFN-epsilon-treated cells revealed that gene expression levels of antiviral proteins were elevated, indicating the induction of an antiviral state. The use of these constructs in a poxvirus prime-boost immunization regime led to robust humoral and cellular immune responses against the encoded Ags, despite the lack of replication in the case of HA-VV-IFN-beta. Thus, coexpression of these factors may be beneficial in the design of safer vector-based vaccines. Our data also indicate that while IFN-epsilon exhibits certain biological traits similar to other type I IFNs, it may also have a specific role in mucosal immune regulation that is quite distinct.

The role of B cells in multiple sclerosis: rationale for B-cell-targeted therapies

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system with no clear etiology. Until recently, most studies have emphasized the role of T cells in the pathogenesis of multiple sclerosis. Data suggesting that B cells play a role in the pathogenesis of multiple sclerosis have been accumulating for the past five decades, demonstrating that the cerebrospinal fluid and central nervous system tissues of multiple sclerosis patients contain B cells, plasma cells, antibodies, and immunoglobulins. Data suggest that B cells are involved in antigen capture and presentation to T cells, cytokine production, antibody secretion, demyelination, tissue damage, and remyelination in multiple sclerosis. These advances in the understanding of B-cell and antibody roles in the pathophysiology of multiple sclerosis provide a strong rationale for B-cell-targeted therapies.

Vaccines for multiple sclerosis: progress to date

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the CNS, characterized pathologically by a perivascular infiltrate consisting predominantly of T cells and macrophages. Although its aetiology remains unknown, several lines of evidence support the hypothesis that autoimmune mechanisms play a major role in the development of the disease. Several widely used disease-modifying agents are approved for the treatment of MS. However, these agents are only partially effective and their ability to attenuate the more progressive phases of the disease is not clear at this time. Therefore, there is a need to develop improved treatment options for MS. This article reviews the role of several novel, selective vaccine strategies that are currently under investigation, including: (i) T-cell vaccination (TCV); (ii) T-cell receptor (TCR) peptide vaccination; (iii) DNA vaccination; and (iv) altered peptide ligand (APL) vaccination. The administration of attenuated autoreactive T cells induces regulatory networks to specifically suppress pathogenic T cells in MS, a strategy named TCV. The concept of TCV was based on the experience of vaccination against aetiological agents of infectious diseases in which individuals are purposely exposed to an attenuated microbial pathogen, which then instructs the immune system to recognize and neutralize it in its virulent form. In regard to TCV, attenuated, pathogenic T cells are similarly used to instruct the immune system to recognize and neutralize disease-inducing T cells. In experimental allergic encephalomyelitis (EAE), an animal model for MS, pathogenic T cells use a strikingly limited number of variable-region elements (V region) to form TCR specific for defined autoantigens. Thus, vaccination with peptides directed against these TCR structures may induce immunoregulatory mechanisms, thereby preventing EAE. However, unlike EAE, myelin-reactive T cells derived from MS patients utilize a broad range of different V regions, challenging the clinical utility of this approach. Subsequently, the demonstration that injection of plasmid DNA encoding a reporter gene into skeletal muscle results in expression of the encoded proteins, as well as in the induction of immune responses in animal models of autoimmunity, was explored as another strategy to re-establish self-tolerance. This approach has promise for the treatment of MS and, therefore, warrants further investigation. APLs are molecules in which the native encephalitogenic peptides are modified by substitution(s) of one or a few amino acids critical for contact with the TCR. Depending on the substitution(s) at the TCR contact residues of the cognate peptide, an APL can induce immune responses that can protect against or reverse EAE. However, the heterogeneity of the immune response in MS patients requires further study to determine which patients are most likely to benefit from APL therapy. Other potential approaches for vaccines in MS include vaccination against axonal growth inhibitors associated with myelin, use of dendritic cells pulsed with specific antigens, and active vaccination against proinflammatory cytokines. Overall, vaccines for MS represent promising approaches for the treatment of this devastating disease, as well as other autoimmune diseases.

The role of the humoral immune system in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE)

The pathogenic events in multiple sclerosis (MS) that result in immune cell infiltration, multifocal demyelination and axonal loss have been focused by the strong impact of the classical MS model experimental autoimmune encephalomyelitis (EAE) towards the hypothesis that MS is an entirely T cell-mediated disease. Although conspicuous humoral immune responses have been known since Kabal's seminal finding of elevated immunoglobulins (Igs) in the cerebrospinal fluid (CSF), only in the past few years evidence derived from recent studies of the MS lesion of anti-myelin antibodies (Abs) in patients with early MS and of MS animal models has led to a renewed interest in the role for B cells, plasma cells and their products in the pathogenesis of MS. This review surveys the actual data concerning the role of the humoral immune system in MS and EAE and explains potential modes of action and long-time persistence in the inflamed brain tissue as a B cell-supportive microenvironment in MS. These mechanisms include the modulation of antigen presentation and costimulation to T cells, increased myelin opsonisation und recruitment of inflammatory cells to the CNS, but also immunoregulatory influences on the remyelination by anti-myelin B cells and Abs. So, affecting the humoral immune system in MS would be a reasonable therapeutic option.

OSP/claudin-11-induced EAE in mice is mediated by pathogenic T cells primarily governed by OSP192Y residue of major encephalitogenic region OSP179-207

Pathogenic autoimmunity against oligodendrocyte-specific protein (OSP/claudin-11), recently implicated in multiple sclerosis (MS) pathophysiology, has been poorly investigated as compared to that against other myelin encephalitogens. Using recombinant soluble mouse OSP (smOSP) and overlapping peptides thereof, we show that smOSP-induced chronic EAE in C57BL/6J mice is primarily associated with CD4(+) T cells reactive against OSP179-207 and OSP22-46, the major and minor encephalitogenic regions, respectively, and with a predominant B cell response against OSP22-46. The encephalitogenic OSP179-207-specific T cells recognized OSP190-202 as minimal stimulatory epitope, while minimal encephalitogenic sequence was OSP191-199. Further delineation and structural bioinformatic analysis of the major encephalitogenic region suggested four overlapping potential I-A(b) core epitopes, predicting OSP192Y as major TCR-contact residue shared by OSP 188-196, OSP190-198, and OSP191-199 cores, albeit at different MHC-II pockets. Accordingly, substitution at OSP192Y yielded OSP188-192A-202, a non-stimulatory/non-encephalitogenic altered peptide ligand (APL) that was antagonistic for OSP188-202-specific encephalitogenic T cells. Systemic administration of OSP188-192A-202 suppressed OSP188-202-induced EAE and fully reversed smOSP-induced EAE. These data suggest that a single epitopic residue (OSP192Y) governs the selection and control of most pathogenic T cells associated with smOSP-induced EAE in H-2(b) mice. This may impact profoundly on peripheral self-tolerance to OSP and on potential APL-mediated therapy of OSP-related autoimmune pathogenesis.

Pathogenic epitopes, heterologous immunity and vaccine design

Vaccine strategies are focused on developing protective responses to immunogenic peptide epitopes of pathogens that are normally recognized by T and B cells. However, some epitopes stimulate crossreactive T-cell responses between pathogens and can prime a host to damaging pathology on infection with the crossreactive pathogen. The removal of potentially pathogenic epitopes from vaccines might enhance prophylaxis and reduce the risk of side effects of vaccine-associated disease.

Substantial research has been directed towards the development of a new generation of vaccines that are based on the inclusion of immunogenic epitopes in recombinant vectors. Here we examine the evidence that under certain conditions immunogenic epitopes can do more harm than good and might therefore be considered pathogenic. We suggest that the specific removal of such pathogenic epitopes from vaccines might increase their prophylactic potential, while minimizing the risk of side-effects from vaccine use.

Sequential polymicrobial infections lead to CNS inflammatory disease: possible involvement of bystander activation in heterologous immunity

VV(PLP) is a recombinant vaccinia virus (VV) encoding myelin proteolipid protein (PLP) that has been used to investigate molecular mimicry and autoimmunity. Since virus infections can cause bystander activation, mice were first infected with VV(PLP), and later challenged with wild-type VV, lymphocytic choriomeningitis virus (LCMV), or murine cytomegalovirus (MCMV). Among the VV(PLP)-primed mice, only MCMV challenge induced significant Ki-67(+), CD3(+)T cell infiltration into the central nervous system (CNS) with a mild PLP antibody response. While MCMV alone caused no CNS disease, control VV-infected mice followed with MCMV developed mild CNS inflammation. Thus, heterologous virus infections can induce CNS pathology.

Polyreactive myelin oligodendrocyte glycoprotein antibodies: Implications for systemic autoimmunity in progressive experimental autoimmune encephalomyelitis

Two myelin oligodendrocyte glycoprotein (MOG92-106) monoclonal antibodies (mAbs) were produced from an A.SW mouse with progressive experimental autoimmune encephalomyelitis. Polyreactivity/specificity of the mAbs was demonstrated by ELISA. Functionality and a potential role in pathogenesis of systemic autoimmunity were demonstrated in vitro in a lymphocytotoxicity assay and in vivo upon injection into naïve mice. Injection of MOG mAb producing hybridomas into naïve mice resulted in immunoglobulin deposition in kidneys and liver. This model will be useful in determining whether transitional forms between CNS (organ)-specific and systemic autoimmune diseases exist, and whether progressive multiple sclerosis has features of a systemic autoimmune disease.

Immunology of multiple sclerosis

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

Specificity of autoantibodies to epitopes of myelin proteins in multiple sclerosis

An autoimmune response to one or more myelin-protein components is thought to be part of the pathogenesis of multiple sclerosis (MS). The immunodominant-autoantibody epitope may be localized on a linear peptide segment, on a conformation-sensitive epitope, or on an epitope resulting from post-translational modifications. Primary, secondary, and tertiary structures of myelin proteins may determine the specific site for binding of autoantibodies. A myelin protein-specific autoantibody can bind to either a linear or conformational epitope, whereas all of the T cell epitopes are linear. At present, the conformational epitopes of myelin proteins have not been identified; most of the methods used to identify the myelin-protein epitopes corresponding to the pathogenesis of multiple sclerosis are involved in the linear epitope mapping. Polymorphism or mutations may cause inappropriate expression of the myelin proteins with alterations to their linear and/or conformational epitopes, and make them susceptible to autoantibody binding, especially if these changes occur at the surface of the protein. This review focuses on the specificity of autoantibodies to the epitopes of myelin proteins and correlates this to the structures of proteins. Factors that influence the expression of myelin-protein epitopes such as the alpha-helical or beta-sheet structure of the protein, the tri-proline site, and the post-translational modifications as well as physicochemical properties of amino acid changed are included.

Novel monoclonal antibodies against proteolipid protein peptide 139-151 demonstrate demyelination and myelin uptake by macrophages in MS and marmoset EAE lesions

Experimental autoimmune encephalomyelitis (EAE) induced by immunization of mice with epitopes of the proteolipid protein (PLP), a major myelin constituent, forms a useful model for the study of multiple sclerosis (MS). In addition, MS patients display PLP-specific T- and B-cell responses, suggesting that PLP reactivity is relevant to pathogenesis.Here, the generation and characterization of a panel of mouse monoclonal antibodies (Mab) against PLP139-151, the prominent encephalitogenic sequence in SJL/J mice is described. Five Mab were generated by conventional immunization of an SJL/J mouse and hybridoma generation. These Mab reacted well with the PLP139-151 peptide in ELISA and belonged to the IgG2a and IgG2b subclasses, consistent with CD4+ T helper 1-cell-supported antibody formation. The Mab also efficiently detected PLP peptide-BSA conjugates in Western blot, confirming their multi-assay applicability. The Mab were subsequently used to determine the occurrence of demyelination in brains of MS patients and marmoset monkeys with EAE. Immunohistochemistry on both paraffin and frozen sections demonstrated a homogeneous expression of PLP139-151 in normal myelin, and a complete absence in lesions containing demyelinated areas, confirming that the Mab can be used as a general myelin marker. In active demyelinating MS lesions, the Mab visualized the peptide in the cytoplasm of macrophages containing phagocytosed myelin. In conclusion, this panel of Mab against the encephalitogenic PLP139-151 epitope forms a useful tool for further study of autoantigen expression, demyelination/remyelination and the staging of lesional activity in MS patients, as well as in EAE models in distinct animal species.

B cells and antibodies in CNS demyelinating disease

There is much evidence to implicate B cells, plasma cells, and their products in the pathogenesis of MS. Despite unequivocal evidence that the animal model for MS, EAE, is initiated by myelin-specific T cells, there is accumulating evidence of a role for B cells, plasma cells, and their products in EAE pathogenesis. The role(s) played by B cells, plasma cells, and antibodies in CNS inflammatory demyelinating diseases are likely to be multifactorial and complex, involving distinct and perhaps opposing roles for B cells versus antibody.

Infection with a recombinant vaccinia virus encoding myelin proteolipid protein causes suppression of chronic relapsing-remitting experimental allergic encephalomyelitis

Mice infected with a recombinant vaccinia virus (VVplp) encoding the myelin proteolipid protein (PLP) and then challenged with the encephalitogenic peptide, PLP139-151, developed a more severe acute attack vs. control mice. Following this initial acute attack, vaccinated mice had significantly less clinical disease (relapses) than control vaccinated or mock vaccinated mice. Control mice developed a relapsing-remitting disease with severe clinical relapses. During the remission state in VVplp vaccinated mice, histopathologic changes were markedly reduced in the central nervous system (CNS) vs. control vaccinated or unvaccinated mice. Inflammation was mainly limited to the meninges with a reduction of mononuclear cells in the parenchyma of the spinal cord in VVplp vaccinated and PLP139-151 challenged mice vs. control mice where inflammatory changes with demyelination was observed. During the remission period an increase in IL-4 was seen. In addition, there was significantly less T cell proliferation to PLP139-151 that was confirmed by an in vivo measurement of T cell reactivity, DTH responses. This suggests that the almost permanent remission state was dictated by a decreased responsiveness to PLP139-151 in VVplp vaccinated mice.