Epstein-Barr virus-specific adoptive immunotherapy: a new horizon for multiple sclerosis treatment?

Virus-Specific T-Cell Therapy for Viral Infections of the Central Nervous System: A Review

Opportunistic viral infections of the central nervous system represent a significant cause of morbidity and mortality among an increasing number of immunocompromised patients. Since antiviral treatments are usually poorly effective, the prognosis generally relies on the ability to achieve timely immune reconstitution. Hence, strategies aimed at reinvigorating antiviral immune activity have recently emerged. Among these, virus-specific T-cells are increasingly perceived as a principled and valuable tool to treat opportunistic viral infections. Here we briefly discuss how to develop and select virus-specific T-cells, then review their main indications in central nervous system infections, including progressive multifocal leukoencephalopathy, CMV infection, and adenovirus infection. We also discuss their potential interest in the treatment of progressive multiple sclerosis, or EBV-associated central nervous system inflammatory disease. We finish with the key future milestones of this promising treatment strategy.

Adoptive T-cell therapy targeting Epstein-Barr virus as a treatment for multiple sclerosis

Emergence of a definitive link between Epstein-Barr virus (EBV) and multiple sclerosis has provided an impetus to develop immune-based therapies to target EBV-infected B cells. Initial studies with autologous EBV-specific T-cell therapy demonstrated that this therapy is safe with minimal side effects and more importantly multiple patients showed both symptomatic and objective neurological improvements including improved quality of life, reduction of fatigue and reduced intrathecal IgG production. These observations have been successfully extended to an 'off-the-shelf' allogeneic EBV-specific T-cell therapy manufactured using peripheral blood lymphocytes of healthy seropositive individuals. This adoptive immunotherapy has also been shown to be safe with encouraging clinical responses. Allogeneic EBV T-cell therapy overcomes some of the limitations of autologous therapy and can be rapidly delivered to patients with improved therapeutic potential.

EBV transformation induces overexpression of hMSH2/3/6 on B lymphocytes and enhances γδT-cell-mediated cytotoxicity via TCR and NKG2D

The engagement of Epstein-Barr virus (EBV)-induced protein ligands in γδ T-cell-mediated anti-EBV immunity, especially in EBV-associated B-cell malignancies, has not been fully elucidated. Previously we reported the overexpression of human MutS homologue 2 (hMSH2), a stress-inducible protein ligand for human γδ T-cells, on EBV-transformed B lymphoblastic cell lines (B-LCLs). In this study, we first generated EBV-transformed B-LCLs from peripheral blood mononuclear cells of healthy volunteers with B95-8 cellular supernatant and cyclosporine A. Secondly, we demonstrated the significantly elevated cell surface protein expression and mRNA transcription of hMSH2 in EBV-transformed B-LCLs, 3D5 and EBV-positive B lymphoma cell line Daudi and Raji. Thirdly, hMSH2-mediated recognition of EBV-transformed B malignant cells by human γδ T-cells was confirmed by specific antibody blocking and siRNA interference. Both TCRγδ and NKG2D participated in hMSH2-mediated recognition of EBV-transformed B malignant cells. Furthermore, hMSH3 and hMSH6, the companion proteins of hMSH2, along with CD98, were found overexpressed on the surface of EBV-transformed malignant B-cells. We concluded that the induced overexpression of hMSH proteins might serve as early alerting biomarkers emerged in EBV-related B-cell malignances or as potential targets for establishing γδ T-cell-based therapeutic immunotherapies towards EBV infection.

New advances in CNS immunity against viral infection

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Advances in CNS immunity and anatomy bridge the CNS and the peripheral immune system.

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Region-specific antiviral responses alter BBB permeability during viral invasion.

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CNS barriers have anatomical specializations with tailored defenses against pathogens.

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Immunocytotherapies for persistent CNS infections can promote non-cytopathic viral clearance.

The central nervous system (CNS) is an immunologically specialized organ where restrictive barrier structures protect the parenchyma from inflammation and infection. This protection is important in preventing damage to non-renewable resident cell populations, such as neurons, responsible for functions ranging from executive to autonomic. Despite these barriers, the CNS can be infected through several entry portals, giving rise to meningitis and encephalitis. Following infection, resident cells recruit peripherally derived immune cells to sites of viral infection. In this review, we discuss recent advances in immune recruitment and entry at barrier structures as well as current immunotherapeutic strategies for the treatment of persistent viral infections.

CD8(+) T-Cells as Immune Regulators of Multiple Sclerosis

The vast majority of studies regarding the immune basis of MS (and its animal model, EAE) have largely focused on CD4(+) T-cells as mediators and regulators of disease. Interestingly, CD8(+) T-cells represent the predominant T-cell population in human MS lesions and are oligoclonally expanded at the site of pathology. However, their role in the autoimmune pathologic process has been both understudied and controversial. Several animal models and MS patient studies support a pathogenic role for CNS-specific CD8(+) T-cells, whereas we and others have demonstrated a regulatory role for these cells in disease. In this review, we describe studies that have investigated the role of CD8(+) T-cells in MS and EAE, presenting evidence for both pathogenic and regulatory functions. In our studies, we have shown that cytotoxic/suppressor CD8(+) T-cells are CNS antigen-specific, MHC class I-restricted, IFNγ- and perforin-dependent, and are able to inhibit disease. The clinical relevance for CD8(+) T-cell suppressive function is best described by a lack of their function during MS relapse, and importantly, restoration of their suppressive function during quiescence. Furthermore, CD8(+) T-cells with immunosuppressive functions can be therapeutically induced in MS patients by glatiramer acetate (GA) treatment. Unlike CNS-specific CD8(+) T-cells, these immunosuppressive GA-induced CD8(+) T-cells appear to be HLA-E restricted. These studies have provided greater fundamental insight into the role of autoreactive as well as therapeutically induced CD8(+) T-cells in disease amelioration. The clinical implications for these findings are immense and we propose that this natural process can be harnessed toward the development of an effective immunotherapeutic strategy.

Epstein-Barr virus and multiple sclerosis: potential opportunities for immunotherapy

Multiple sclerosis (MS) is a common chronic inflammatory demyelinating disease of the central nervous system (CNS) causing progressive disability. Many observations implicate Epstein–Barr virus (EBV) in the pathogenesis of MS, namely universal EBV seropositivity, high anti-EBV antibody levels, alterations in EBV-specific CD8⁺ T-cell immunity, increased spontaneous EBV-induced transformation of peripheral blood B cells, increased shedding of EBV from saliva and accumulation of EBV-infected B cells and plasma cells in the brain. Several mechanisms have been postulated to explain the role of EBV in the development of MS including cross-reactivity between EBV and CNS antigens, bystander damage to the CNS by EBV-specific CD8⁺ T cells, activation of innate immunity by EBV-encoded small RNA molecules in the CNS, expression of αB-crystallin in EBV-infected B cells leading to a CD4⁺ T-cell response against oligodendrocyte-derived αB-crystallin and EBV infection of autoreactive B cells, which produce pathogenic autoantibodies and provide costimulatory survival signals to autoreactive T cells in the CNS. The rapidly accumulating evidence for a pathogenic role of EBV in MS provides ground for optimism that it might be possible to prevent and cure MS by effectively controlling EBV infection through vaccination, antiviral drugs or treatment with EBV-specific cytotoxic CD8⁺ T cells. Adoptive immunotherapy with in vitro-expanded autologous EBV-specific CD8⁺ T cells directed against viral latent proteins was recently used to treat a patient with secondary progressive MS. Following the therapy, there was clinical improvement, decreased disease activity on magnetic resonance imaging and reduced intrathecal immunoglobulin production.