Induction of EAE by T cells specific for alpha B-crystallin depends on prior viral infection in the CNS

Peripheral viral challenge exacerbates experimental autoimmune encephalomyelitis

Peripheral viral infections are potent triggers of exacerbation in multiple sclerosis (MS). Here, we used a preclinical model of MS, the experimental autoimmune encephalomyelitis (EAE) to corroborate this comorbidity in an experimental setting. EAE was induced by immunization of mice with MOG peptide, and paralysis was scored using a 5-point scale. At the onset of the chronic phase of the disease (Days 42-58 after MOG injection) the animals were divided into low responders (LR) and high responders (HR) with the mean score of 1.5 and 2.5, respectively. The acute phase response (APR) was induced by intraperitoneal injections of a viral mimetic, polyinosinic-polycytidylic acid (PIC). Two daily injections were performed on Days 42 and 44 (PIC_42,44 challenge) and on Days 54, 55 and 56 (PIC_54,55,56 challenge). PIC_42,44 challenge had no effect of EAE disease, whereas PIC_54,55,56 challenge rapidly increased paralysis but only in HR group. This exacerbation ultimately led to animal death by Day 58. These results demonstrate that antiviral APR is a potent exacerbator of EAE, and that this activity directly correlates with the severity of the disease. This in turn, indicates that antiviral APR might play a pivot role in linking peripheral viral infections with MS exacerbations.

Positive or negative involvement of heat shock proteins in multiple sclerosis pathogenesis: an overview

Multiple sclerosis (MS) is the most diffuse chronic inflammatory disease of the central nervous system. Both immune-mediated and neurodegenerative processes apparently play roles in the pathogenesis of this disease. Heat shock proteins (HSPs) are a family of highly evolutionarily conserved proteins; their expression in the nervous system is induced in a variety of pathologic states, including cerebral ischemia, neurodegenerative diseases, epilepsy, and trauma. To date, investigators have observed protective effects of HSPs in a variety of brain disease models (e.g. of Alzheimer disease and Parkinson disease). In contrast, unequivocal data have been obtained for their roles in MS that depend on the HSP family and particularly on their localization (i.e. intracellular or extracellular). This article reviews our current understanding of the involvement of the principal HSP families in MS.

Virus-induced CD8+ T cells accelerate the onset of experimental autoimmune encephalomyelitis: implications for how viral infections might trigger multiple sclerosis exacerbations

Viral infections can exacerbate multiple sclerosis (MS) through poorly defined mechanisms. We developed an experimental system whereby infection with an asymptomatic neurotropic alphavirus caused a transient acceleration of experimental autoimmune encephalomyelitis (EAE) without altering the expansion or differentiation of autoreactive CD4+ T cells. Instead, this effect on the clinical course of EAE depended on CD8+ T cells that neither participate in viral clearance nor induce neuropathology in infected mice without EAE. Our system should be useful to further unravel how certain viral infections trigger MS exacerbations and to understand how CD8+ T cells can exert pathogenic effects within active demyelinating lesions.

The protective and therapeutic function of small heat shock proteins in neurological diseases

Historically, small heat shock proteins (sHSPs) have been extensively studied in the context of being intracellular molecular chaperones. However, recent studies looking at the role of sHSPs in neurological diseases have demonstrated a near universal upregulation of certain sHSPs in damaged and diseased brains. Initially, it was thought that sHSPs are pathological in these disease states because they are found in the areas of damage. However, transgenic overexpression and exogenous administration of sHSPs in various experimental disease paradigms have shown just the contrary – that sHSPs are protective, not pathological. This review examines sHSPs in neurological diseases and highlights the potential for using these neuroprotective sHSPs as novel therapeutics. It first addresses the endogenous expression of sHSPs in a variety of neurological disorders. Although many studies have examined the expression of sHSPs in neurological diseases, there are no review articles summarizing these data. Furthermore, it focuses on recent studies that have investigated the therapeutic potential of sHSPs for neurological diseases. Finally, it will explain what we think is the function of endogenous sHSPs in neurological diseases.

More to come: humoral immune responses in MS

Interest in the role of B-cells in multiple sclerosis (MS) pathogenesis has increased, and a number of B-cell targeted therapies are currently in clinical trials. B-cells are key mediators of the humoral immune response, with roles including antibody production and acting as antigen presenting cells. Whilst previously, the presence of B-cells within MS plaques has been thought to be secondary to T-cell dysregulation, it is now becoming clear that B-cells play an independent role in disease. In this review we will discuss the potential role of B-cells in MS, how this influences our understanding of the disease, and potential therapeutic implications.

Experimental in vivo and in vitro models of multiple sclerosis: EAE and beyond

Although the primary cause of multiple sclerosis (MS) is unknown, the widely accepted view is that aberrant (auto)immune responses possibly arising following infection(s) are responsible for the destructive inflammatory demyelination and neurodegeneration in the central nervous system (CNS). This notion, and the limited access of human brain tissue early in the course of MS, has led to the development of autoimmune, viral and toxin-induced demyelination animal models as well as the development of human CNS cell and organotypic brain slice cultures in an attempt to understand events in MS. The autoimmune models, collectively known as experimental autoimmune encephalomyelitis (EAE), and viral models have shaped ideas of how environmental factors may trigger inflammation, demyelination and neurodegeneration in the CNS. Understandably, these models have also heavily influenced the development of therapies targeting the inflammatory aspect of MS. Demyelination and remyelination in the absence of overt inflammation are better studied in toxin-induced demyelination models using cuprizone and lysolecithin. The paradigm shift of MS as an autoimmune disease of myelin to a neurodegenerative disease has required more appropriate models reflecting the axonal and neuronal damage. Thus, secondary progressive EAE and spastic models have been crucial to develop neuroprotective approaches. In this review the current in vivo and in vitro experimental models to examine pathological mechanisms involved in inflammation, demyelination and neuronal degeneration, as well as remyelination and repair in MS are discussed. Since this knowledge is the basis for the development of new therapeutic approaches for MS, we particularly address whether the currently available models truly reflect the human disease, and discuss perspectives to further optimise and develop more suitable experimental models to study MS.

Multiple sclerosis: immunopathogenesis and controversies in defining the cause

PURPOSE OF REVIEW

Multiple sclerosis is a major cause of neurological disability in Western societies. The most important reason for the limited success obtained in the treatment and prevention so far is most likely related to the limited knowledge about its cause and pathogenesis. This paper discusses recent progress and controversies in the understanding of the pathogenesis and cause of multiple sclerosis.

RECENT FINDINGS

Both T helper cells type 1 (Th1 cells), Th17 cells, cytotoxic T cells, B cells and regulatory T cells are involved in the inflammatory process. Axonal loss seems to be driven by inflammation during the early stages of disease but may become independent of inflammation at later stages. The target antigen of the immune response has not been identified. Weak genetic association has been established in two cytokine receptors, whereas increasing female: male ratio support the importance of environmental risk factors. A substantial proportion of intrathecal B cells are infected with Epstein-Barr virus.

SUMMARY

Multiple sclerosis is a complex disease and calls for integrated efforts from immunology, epidemiology, neuroscience and genetics. In particular, the immunological implications of environmental risk factors such as vitamin D desufficiency, smoking and Epstein-Barr virus infection need to be explored.

The immunological basis for treatment of multiple sclerosis

During the last few years, the concept of multiple sclerosis (MS) as a pure inflammatory disease mediated by myelin reactive T cells has been challenged. Neither the specificity nor the mechanisms triggering or perpetuating the immune response are understood. Genetic studies have so far not identified therapeutic targets outside the HLA complex, but epidemiological and immunological studies have suggested putative pathogenetic factors which may be important in therapy or prevention, including the Epstein-Barr virus and vitamin D. Advances in the treatment of MS have been reached by manipulating the immune response where the pathogenesis of MS intersects experimental autoimmune encephalomyelitis, most recently by blocking T-cell migration through the blood-brain barrier. Antigen-specific approaches are effective in experimental models driven by a focused immune response against defined autoantigens, but MS may not fit into this concept. Novel candidate autoantigens which are not constitutively expressed in the brain, such as protein alpha-B crystallin or IgG V-region idiotopes, as well as evidence of pathogenetic heterogeneity and complexity, suggest that treating MS by tolerizing the immune system against an universal MS antigen may be a fata morgana. Further characterization of MS subtypes may lead to individualized treatment. However, shared immunological features, such as intrathecal production of oligoclonal IgG, suggest that potential therapeutic targets may be shared by most MS patients.

Tolerization of an established alphaB-crystallin-reactive T-cell response by intravenous antigen

Tolerance induction to prevent activation of a naïve T-cell repertoire has been well documented in rodents and can be readily achieved by intravenous, oral or intranasal administration of antigen in the absence of adjuvants. In autoimmune diseases such as multiple sclerosis (MS) the presence of an established memory/effector T-cell repertoire against self-antigens is likely to be more relevant than the potential reactivity of naive T cells. Methods to eliminate such an established T-cell response are less well understood. In this study, we explored the effectiveness of intravenous soluble antigen to eliminate a pre-existing T-cell response against alphaB-crystallin, a candidate autoantigen in MS. We used mice that are deficient for the target antigen. This condition allowed for a vigourous T-cell and antibody response to develop upon immunization, and eliminated all possible endogenous mechanisms of tolerance for alphaB-crystallin that are found in normal rodents. When applied 3 weeks after priming with alphaB-crystallin, intravenous administration of soluble antigen almost completely abrogated the established T-cell response in a dose-dependent manner as evidenced by T-cell non-responsiveness in tolerized animals to a re-challenge with antigen in complete Freund's adjuvant. Evaluating delayed-type hypersensitivity responses after tolerance induction revealed that the tolerizing effect was achieved within 24 hr. Furthermore, the tolerizing effect was found to be antigen-specific and long lasting. In contrast, serum antibody levels were markedly increased. Our data clarify that in the absence of any natural form of immune regulation, antigen-specific memory/effector T cells can be effectively silenced by intravenous antigen.