Activation and clonal expansion of human myelin basic protein-reactive T cells by bacterial superantigens

Guillain-Barré syndrome, transverse myelitis and infectious diseases

Guillain-Barré syndrome (GBS) and transverse myelitis (TM) both represent immunologically mediated polyneuropathies of major clinical importance. Both are thought to have a genetic predisposition, but as of yet no specific genetic risk loci have been clearly defined. Both are considered autoimmune, but again the etiologies remain enigmatic. Both may be induced via molecular mimicry, particularly from infectious agents and vaccines, but clearly host factor and co-founding host responses will modulate disease susceptibility and natural history. GBS is an acute inflammatory immune-mediated polyradiculoneuropathy characterized by tingling, progressive weakness, autonomic dysfunction, and pain. Immune injury specifically takes place at the myelin sheath and related Schwann-cell components in acute inflammatory demyelinating polyneuropathy, whereas in acute motor axonal neuropathy membranes on the nerve axon (the axolemma) are the primary target for immune-related injury. Outbreaks of GBS have been reported, most frequently related to Campylobacter jejuni infection, however, other agents such as Zika Virus have been strongly associated. Patients with GBS related to infections frequently produce antibodies against human peripheral nerve gangliosides. In contrast, TM is an inflammatory disorder characterized by acute or subacute motor, sensory, and autonomic spinal cord dysfunction. There is interruption of ascending and descending neuroanatomical pathways on the transverse plane of the spinal cord similar to GBS. It has been suggested to be triggered by infectious agents and molecular mimicry. In this review, we will focus on the putative role of infectious agents as triggering factors of GBS and TM.

Treatment against human endogenous retrovirus: a possible personalized medicine approach for multiple sclerosis

Human endogenous retroviruses (HERV) represent about 8 % of the human genome. Some of these genetic elements are expressed in pathological circumstances. A HERV protein, the multiple sclerosis-associated retrovirus (MSRV) envelope protein (MSRV-Env), is expressed in the blood and active brain lesions of multiple sclerosis (MS) patients. It possesses pro-inflammatory and myelinotoxic properties. The patterns of expression and pathogenic properties of MSRV-Env make it a relevant drug target for MS therapeutics-in particular for preventing neurodegeneration, a key component of progressive forms of MS. An immunoglobulin G4 monoclonal antibody (mAb), called GNbAC1, has been developed to neutralize this pathogenic target. After showing neutralizing effects in vitro and in mouse models of MS, GNbAC1 is now in phase II clinical development. MSRV-related biomarkers such as MSRV-Env and MSRV polymerase (MSRV-Pol) gene transcripts are overexpressed in the blood and cerebrospinal fluid of patients with MS. These biomarkers may have prognostic value for long-term MS evolution, and their transcription levels in blood decline during treatments with GNbAC1, which has also been reported in patients administered reference MS drugs such as natalizumab or interferon-β. GNbAC1 as a new MSRV-Env-antagonist mAb could be a specific and causal treatment for MS, with a particular application for progressive forms of the disease. For possible use in companion diagnostic tests, MSRV-associated biomarkers could open the door to a personalized therapeutic approach for MS.

MSRV envelope protein is a potent, endogenous and pathogenic agonist of human toll-like receptor 4: Relevance of GNbAC1 in multiple sclerosis treatment

Multiple sclerosis associated retrovirus envelope protein (MSRV-Env) was repeatedly detected in brain lesions and blood of multiple sclerosis (MS) patients. We performed the first pharmacological characterisation of MSRV-Env on recombinant and native human TLR4. MSRV-Env is a full and highly potent TLR4 agonist of endogenous origin. MSRV-Env induces TLR4-dependent pro-inflammatory stimulation of immune cells in vitro and in vivo, and impairs oligodendrocytes precursor cells differentiation to myelinating oligodendrocytes. MSRV-Env may play a role in chronic inflammation and impaired remyelination in MS. GNbAC1, a selective monoclonal antibody, antagonizes MSRV-Env pathogenic effects and represents an innovative therapeutic approach of MS.

Previous infection with Staphylococcus aureus strains attenuated experimental encephalomyelitis

BACKGROUND

Bacterial superantigens are potent T cell activators that can activate T cells with specificity for antigens of the central nervous system (CNS). In this study, we compared the effect of two S. aureus strains on experimental autoimmune encephalomyelitis (EAE) development. C57BL/6 female mice were infected with S. aureus ATCC 51650, which produces toxic shock syndrome toxin 1 (TSST-1+) or S. aureus ATCC 43300, which does not produce toxins (TOX-). Three days later, the animals were subjected to EAE induction by immunization with myelin oligodendrocyte glycoprotein (MOG). The weight variation, disease incidence and clinical score were recorded daily. Cytokines and Foxp3+ regulatory T cells in the brain were evaluated during the acute disease phase. Cytokines and Foxp3+ regulatory T cells in the spleen and histopathological analysis of the CNS were assessed during the chronic stage.

RESULTS

Previous infection with both strains similarly decreased the clinical score; however, only the TSST-1+ strain clearly diminished inflammation in the CNS. The infections also modulated cytokine production in the spleen and CNS. Reduced production of IL-5 and IL-10 was detected in MOG-stimulated spleen cultures in the TOX- and TSST-1+ infected groups, respectively. In S. aureus stimulated cultures, there was an increased production of IFN-γ and IL-10 in both infected groups and an increased level of IL-5 in the TSST-1+ group. CNS infiltrating cell cultures from previously infected mice produced less IL-17 in response to MOG and more IFN-γ in response to S. aureus stimulation.

CONCLUSIONS

These results indicated that both strains attenuated clinical EAE manifestations, but only TSST-1 clearly decreased CNS inflammation.

Superantigens induce IL-17 production from polarized Th1 clones

Differentiation of naïve CD4(+) T cells has been considered to be an irreversible event and, in particular, the plasticity is believed to be completely lost in Th1 subset in vitro after multiple stimulations. However, here we demonstrate that highly polarized myelin oligodendrocyte glycoprotein (MOG)- and herpes simples virus-specific Th1 clones were still capable of producing IL-17 upon superantigen stimulation. Anti-MHC class-II and anti-TCR αβ chains partially blocked superantigen-induced IL-17 production. These findings suggest that fully differentiated Th1 cells still have capability to produce cytokines of other Th subsets and production of IL-17 by MOG-specific Th1 cells may have implication in initiation and/or exacerbation of neurological autoimmune diseases.

Activation of myelin reactive T cells in multiple sclerosis: a possible role for T cell degeneracy?

While it is widely accepted that myelin reactive T cells are key players in the immunopathogenesis of multiple sclerosis (MS), the initial triggers that turn on these self-reactive T-cells remain to be determined. One mechanism, which is already text book knowledge for a decade, is molecular mimicry by which viral or microbial antigens are able to cross-activate T cells specific for myelin epitopes, the major target in MS pathology. Although proof of concept for this principle was given in animal model studies, evidence for such a mechanism in MS is limited. In this issue, Zhang et al. demonstrate an increased frequency of T cells that cross-react with a wide variety of antigens, a phenomenon termed as T cell degeneracy. While the role of these degenerate T cells in MS remains to be determined the authors now provide new elegant tools to study this T cell population, thus providing a starting point to better understand their function in MS.

The role of CD4 T cells in the pathogenesis of multiple sclerosis

T lymphocytes play a central role in the pathogenesis of multiple sclerosis (MS) (Zhang et al., 1992). Both CD4+ and CD8+ T cells have been demonstrated in MS lesions, with CD4+ T cells predominating in acute lesions and CD8+ T cells being observed more frequently in chronic lesions (Raine, 1994). Additionally, T cells are found in all four of the described histopathologic subtypes of MS (Lucchinetti et al., 2000). Activated myelin‐reactive CD4+ T cells are present in the blood and cerebrospinal fluid (CSF) of MS patients; in contrast, only nonactivated myelin‐reactive T cells are present in the blood of controls (Zhang et al., 1994). The success of several T‐cell‐targeted therapies in MS reinforces the importance of the role of the T cell in MS pathogenesis. Here, we outline basic concepts in CD4+ T‐cell immunology and summarize the current understanding of the role of CD4+ T cells in the pathogenesis of MS.

Long-term human coronavirus-myelin cross-reactive T-cell clones derived from multiple sclerosis patients

Autoimmune reactions associated with MS involve genetic and environmental factors. Because murine coronaviruses induce an MS-like disease, the human coronaviruses (HCoV) are attractive candidates as environmental factors involved in a demyelinating pathology. We previously reported the isolation of HCoV-229E/myelin basic protein (MBP) cross-reactive T-cell lines (TCL) in MS patients. To investigate antigenic cross-reactivity at the molecular level, 155 long-term T-cell clones (TCC) were derived from 32 MS patients by in vitro selection with MBP, proteolipid protein (PLP) or HCoV (strains 229E and OC43). Overall, 114 TCC were virus-specific, 31 were specific for myelin Ag and 10 other were HCoV/myelin cross-reactive. Twenty-eight virus-specific TCC and 7 myelin-specific TCC were obtained from six healthy donors. RACE RT-PCR amplification of the Vbeta chains of five of ten the cross-reactive TCC confirmed clonality and sequencing identified the CDR3 region associated with cross-reactivity. Our findings have promising implications in the investigation of the role of molecular mimicry between coronaviruses and myelin in MS as a mechanism related to disease initiation or relapses.

Diagnosis and management of acute myelopathies

BACKGROUND

Acute myelopathies represent a heterogeneous group of disorders with distinct etiologies, clinical and radiologic features, and prognoses. Transverse myelitis (TM) is a prototype member of this group in which an immune-mediated process causes neural injury to the spinal cord, resulting in varying degrees of weakness, sensory alterations, and autonomic dysfunction. TM may exist as part of a multifocal CNS disease (eg, MS), multisystemic disease (eg, systemic lupus erythematosus), or as an isolated, idiopathic entity.

REVIEW SUMMARY

In this article, we summarize recent classification and diagnostic schemes, which provide a framework for the diagnosis and management of patients with acute myelopathy. Additionally, we review the state of current knowledge about the epidemiology, natural history, immunopathogenesis, and treatment strategies for patients with TM.

CONCLUSIONS

Our understanding of the classification, diagnosis, pathogenesis, and treatment of TM has recently begun to expand dramatically. With more rigorous criteria applied to distinguish acute myelopathies and with an emerging understanding of immunopathogenic events that underlie TM, it may now be possible to effectively initiate treatments in many of these disorders. Through the investigation of TM, we are also gaining a broader appreciation of the mechanisms that lead to autoimmune neurologic diseases in general.

Presence of IgE antibodies to bacterial superantigens and increased IL-13-producing T cells in myelitic patients with atopic diathesis

BACKGROUND

Superantigens are considered to exacerbate autoimmune inflammation through the expansion of autoreactive T cells; however, the immune response to bacterial superantigens has not been extensively studied in any type of myelitis. We recently reported the occurrence of a distinct type of myelitis in patients with atopic diathesis, which in a recent nationwide survey was reported to be widespread in Japan. The aim of this study was to investigate the presence of IgE antibodies to bacterial superantigens and the proportion of IL-13- or IL-5-producing CD4+ or CD8+ T cells in patients with myelitis and atopic diathesis.

METHODS

Twenty-four myelitic patients with and 12 myelitic patients without hyperIgEemia, 28 patients with multiple sclerosis (MS) and 34 healthy controls were enrolled in this study. IgE antibodies to staphylococcal enterotoxins A (SEA) and B (SEB) in sera were measured using a liquid-phase enzyme immunoassay, and the intracellular production of IL-5 and IL-13 in peripheral blood CD4+ and CD8+ T cells was measured by flow cytometry.

RESULTS

The myelitic patients with hyperIgEemia showed significantly higher positive rates of serum SEA/SEB-specific IgE antibodies (41.7 and 62.5%, respectively) than the healthy controls (5.9 and 8.8%), patients with MS (0 and 21.4%) and those with normoIgEemic myelitis (0 and 0%). Moreover, IL-13-producing CD4+ T cells and CD8+ T cells increased significantly in the myelitic patients with hyperIgEemia compared to the controls, while IL-5-producing CD4+ or CD8+ T cells did not.

CONCLUSIONS

The IgE response to staphylococcal superantigens is heightened in myelitic patients with atopic diathesis, which might contribute to increases in IL-13-producing T cells and thus the development of myelitis.

Insights into the immunopathogenesis of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). Significant progress has been made in our understanding of the etiology of MS. MS is widely believed to be an autoimmune disease that results from aberrant immune responses to CNS antigens. T cells are considered to be crucial in orchestrating an immunopathological cascade that results in damage to the myelin sheath. This review summarizes the currently available data supporting the idea that myelin reactive T cells are actively involved in the immunopathogenesis of MS. Some of the therapeutic strategies for MS are discussed with a focus on immunotherapies that aim to specifically target the myelin reactive T cells.

Hepatocyte growth factor in cerebrospinal fluid in neurologic disease

OBJECTIVE

To investigate hepatocyte growth factor (HGF) concentration in cerebrospinal fluid (CSF) in neurologic disease.

MATERIALS AND METHODS

We determined CSF concentration of HGF with human-HGF-specific enzyme-linked immunosorbent assays (ELISA) in 121 patients: Alzheimer's disease (AD) (33), amyotrophic lateral sclerosis (ALS) (10), Parkinson's disease (PD) (5), progressive supranuclear palsy (PSP) (3), spinocerebellar degeneration (7), acute disseminating encephalomyelitis (ADEM) (6), human T-lymphotropic virus-1 (HTLV-1)-associated myelopathy (HAM) (6), multiple sclerosis (MS) (7), aseptic meningitis (AM) (12), and peripheral neuropathy and myopathy as control diseases (32).

RESULTS

HGF concentrations in CSF were significantly higher with diseases of the central nervous system (CNS) than control diseases and were slightly higher with AD than other neurodegenerative diseases. Values were highest with ADEM but decreased during corticosteroid treatment. We found no relationship between HGF in CSF and CSF cells or protein, immunoglobulin index, or Q albumin.

CONCLUSION

It is suggested that high concentrations of HGF in CSF may be partially related to CNS pathology, especially to demyelinating disease.

Immunopathogenesis of acute transverse myelitis

Acute transverse myelitis is a group of disorders characterized by focal inflammation of the spinal cord and resultant neural injury. Acute transverse myelitis may be an isolated entity or may occur in the context of multifocal or even multisystemic disease. It is clear that the pathological substrate--injury and dysfunction of neural cells within the spinal cord--may be caused by a variety of immunological mechanisms. For example, in acute transverse myelitis associated with systemic disease (i.e. systemic lupus erythematosus or sarcoidosis), a vasculitic or granulomatous process can often be identified. In idiopathic acute transverse myelitis, there is an intraparenchymal or perivascular cellular influx into the spinal cord, resulting in the breakdown of the blood-brain barrier and variable demyelination and neuronal injury. There are several critical questions that must be answered before we truly understand acute transverse myelitis: (1) What are the various triggers for the inflammatory process that induces neural injury in the spinal cord? (2) What are the cellular and humoral factors that induce this neural injury? and (3) Is there a way to modulate the inflammatory response in order to improve patient outcome? Although much remains to be elucidated about the causes of acute transverse myelitis, tantalizing clues as to the potential immunopathogenic mechanisms in acute transverse myelitis and related inflammatory disorders of the spinal cord have recently emerged. It is the purpose of this review to illustrate recent discoveries that shed light on this topic, relying when necessary on data from related diseases such as acute disseminated encephalomyelitis, Guillain-Barré syndrome and neuromyelitis optica. Developing a further understanding of how the immune system induces neural injury will depend upon confirmation and extension of these findings and will require multicenter collaborative efforts.

Multiple sclerosis retrovirus particles and recombinant envelope trigger an abnormal immune response in vitro, by inducing polyclonal Vbeta16 T-lymphocyte activation

A retroviral element (MSRV) defining a family of genetically inherited endogenous retroviruses (HERV-W) has recently been characterized in cell cultures from patients with multiple sclerosis (MS). To address the possible relationship with MS, direct detection of circulating virion RNA was proposed but revealed technically difficult to perform in standardized conditions, in the face of multiple endogenous HERV-W copies. A parallel approach has evaluated MSRV potential pathogenicity in relation to characteristic features of multiple sclerosis, in particular, T-lymphocyte-mediated immunopathology. We report here that MSRV particles induce T-lymphocyte response with a bias in the Vbeta16 chain usage in surface receptor, whatever the HLA DR of the donor. A recombinant MSRV envelope-but not core-protein reproduced similar nonconventional activation. Molecular analysis of Vbeta CDR3 showed that Vbeta16 expansions are polyclonal. Our results thus provide evidence that MSRV envelope protein can trigger an abnormal immune response with similar characteristics to that of superantigens.

T cell receptor BV gene rearrangements in the spinal cords and cerebrospinal fluid of patients with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal disorder whose etiology and pathogenesis remain unknown. Recent studies, however, have demonstrated the presence of inflammatory infiltrates within ALS spinal cord and suggested the possibility of an immune-mediated process in motor neuron degeneration. We have analyzed the diversity of T-cells in the spinal cord in ALS. Reverse transcriptase polymerase chain reaction (RT-PCR) with variable (V) region sequence specific oligonucleotide primers was used to amplify T-cell receptor (TCR)BV transcripts from spinal cords obtained at autopsy from patients with ALS, patients who died without inflammatory disease of the central nervous system, brains from patients with ALS, and brains from patients who died with inflammatory CNS disease. Sequencing was then performed on the amplified transcripts. An overall increase in the level of TCRBV 2 transcripts was detected in ALS specimens when compared to controls. This result was independent of the HLA genotype of the individual. Furthermore, enrichment of TCRBV2-positive T cells could be demonstrated in cerebrospinal fluid derived from patients with ALS, using PCR analysis and a T cell stimulation assay with toxic shock syndrome toxin-1 (TSST-1), a Vbeta2-specific superantigen. Our results suggest that an immunological process involving the specific expansion of Vbeta2 TCR-positive T-cells may be important in the pathogenesis of ALS.

Myelin reactive T cells in the autoimmune pathogenesis of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) leading to demyelination. Although it is widely accepted that demyelination in MS results from an active inflammatory process, the cause of the inflammation is still not completely resolved. Findings in experimental autoimmune encephalomyelitis (EAE), an animal model of MS, and observations in human MS have led to the hypothesis that MS is an autoimmune disease mediated by autoreactive T cells with specificity for myelin antigens. The identity of the brain antigen(s) which is (are) the primary target(s) of the autoimmune process is not known, but current evidence indicates that myelin basic protein (MBP) is a likely candidate. In this paper we will overview some of the experimental evidence suggesting that MBP reactive T cells hold a central position in the pathogenesis of MS, and discuss some of the currently tested therapeutic strategies in MS which are directed towards the pathogenic MBP reactive T cells. Although there appears to be no direct correlation between anti-MBP T cell responses and clinical disease activity, some recent observations suggest that monitoring of anti-MBP T cell responses could be helpful to study immunological efficacy of experimental immunotherapies in MS.

Cytokine profile of myelin basic protein-reactive T cells in multiple sclerosis and healthy individuals

Myelin basic protein (MBP)-reactive T cells have been implicated in the autoimmune pathogenesis of multiple sclerosis (MS). In this study, we examined the cytokine profile of 531 primary MBP-reactive T-cell lines and 72 independently established clones from 32 patients with MS and 18 healthy controls (NS) by using highly sensitive enzyme-linked immunosorbent assays. An increased number of primary T-cell lines producing interferon-gamma (IFN gamma) and/or interleukin-4 (IL-4) in response to MBP were found in patients with MS compared with controls. No distinct Th1 or Th2 subtypes could be demonstrated among the MBP-reactive clones. IL-4 was more frequently observed among MS-derived clones. Clones derived from MS patients produced increased levels of IL-2, IL-4, tumor necrosis factor-alpha (TNF alpha), IFN gamma, and IL-10, but not IL-6. It is interesting that MBP-reactive T cells from MS patients expressing the disease-associated HLA-DRB1*15 allele produced increased quantities of TNF alpha, a cytokine suggested to play an important role in inflammation and demyelination. When challenged with either MBP or a bacterial superantigen, the clones expressed similar levels of the proinflammatory cytokine IFN gamma. Our study suggests a functional difference in T-cell responses to MBP in patients with MS compared with healthy individuals, and provides further insights into the role of MBP-reactive T cells and their cytokine profile in the inflammatory processes of MS.