Failure of allogeneic bone marrow transplantation to arrest disease activity in multiple sclerosis

Hematopoietic Stem Cell Transplantation for Neurological Disorders: A Focus on Inborn Errors of Metabolism

Hematopoietic stem cells have been investigated and applied for the treatment of certain neurological disorders for a long time. Currently, their therapeutic potential is harnessed in autologous and allogeneic hematopoietic stem cell transplantation (HSCT). Autologous HSCT is helpful in immune-mediated neurological diseases such as Multiple Sclerosis. However, clinical benefits derive more from the immunosuppressive conditioning regimen than the interaction between stem cells and the nervous system. Mainly used for hematologic malignancies, allogeneic HSCT explores the therapeutic potential of donor-derived hematopoietic stem cells. In the neurological setting, it has proven to be most valuable in Inborn Errors of Metabolism, a large spectrum of multisystem disorders characterized by congenital deficiencies in enzymes involved in metabolic pathways. Inborn Errors of Metabolism such as X-linked Adrenoleukodystrophy present with brain accumulation of enzymatic substrates that result in progressive inflammatory demyelination. Allogeneic HSCT can halt ongoing inflammatory neural destruction by replacing hematopoietic-originated microglia with donor-derived myeloid precursors. Microglia, the only neural cells successfully transplanted thus far, are the most valuable source of central nervous system metabolic correction and play a significant role in the crosstalk between the brain and hematopoietic stem cells. After transplantation, engrafted donor-derived myeloid cells modulate the neural microenvironment by recapitulating microglial functions and enhancing repair mechanisms such as remyelination. In some disorders, additional benefits result from the donor hematopoietic stem cell secretome that cross-corrects neighboring neural cells via mannose-6-phosphatase paracrine pathways. The limitations of allogeneic HSCT in this setting relate to the slow turnover of microglia and complications such as graft-vs.-host disease. These restraints have accelerated the development of hematopoietic stem cell gene therapy, where autologous hematopoietic stem cells are collected, manipulated ex vivo to overexpress the missing enzyme, and infused back into the patient. With this cellular drug vehicle strategy, the brain is populated by improved cells and exposed to supraphysiological levels of the flawed protein, resulting in metabolic correction. This review focuses on the mechanisms of brain repair resulting from HSCT and gene therapy in Inborn Errors of Metabolism. A brief mention will also be made on immune-mediated nervous system diseases that are treated with this approach.

Efficacy of Allogeneic Hematopoietic Cell Transplantation for Autoimmune Diseases

Allogeneic hematopoietic cell transplantation (HCT) may be efficacious for autoimmune diseases (AIDs), but its efficacy for individual AIDs is unknown. Factors influencing the likelihood of relapse for each AID are also unknown. This study aimed to determine the likelihood of relapse for each common AID and to generate hypotheses about factors influencing the likelihood of relapse. We reviewed charts of adult patients with nonhematologic AIDs who had undergone HCT in Alberta (n = 21) and patients described in the literature (n = 67). We used stringent inclusion criteria to minimize the inclusion of patients whose AID may have been cured before transplantation. We also used stringent definitions of AID relapse and remission. AID relapsed in 2 of 9 patients (22%) with lupus, in 4 of 12 (33%) with rheumatoid arthritis (RA), in 0 of 4 (0%) with systemic sclerosis (SSc), in 3 of 16 (19%) with psoriasis, in 1 of 12 (8%) with Behçet's disease (BD), in 1 of 15 (7%) with Crohn's disease (CD), in 0 of 5 (0%) with ulcerative colitis (UC), in 4 of 8 (50%) with multiple sclerosis (MS), and in 3 of 3 (100%) with type 1 diabetes mellitus (T1DM). Among highly informative patients (followed for >1 year after discontinuation of immunosuppressive therapy if no relapse, or donor AID status known if relapse), relapse occurred in 0 of 3 patients with lupus, in 2 of 7 with RA, in 0 of 2 with SSc, in 3 of 6 with psoriasis, in 0 of 3 with BD, in 0 of 10 with CD, in 0 of 3 with UC, in 2 of 3 with MS, and in 2 of 2 with T1DM. There appeared to be no associations between AID relapse and low intensity of pretransplantation chemoradiotherapy, multiple lines of AID therapy (surrogate for AID refractoriness) except perhaps for lupus, absence of serotherapy for graft-versus-host disease (GVHD) prophylaxis, lack of GVHD except perhaps for lupus, or incomplete donor chimerism. Even though remission commonly occurs after HCT in lupus, RA, SSc, psoriasis, BD, CD, and UC, HCT is efficacious for only a subset of patients. The efficacy appears to be unrelated to pretransplantation therapy, GVHD, or chimerism. Large studies are needed to determine the characteristics of patients likely to benefit from HCT for each AID.

Progression and CSF Inflammation after Eradication of Oligoclonal Bands in an MS Patient Treated with Allogeneic Hematopoietic Cell Transplantation for Follicular Lymphoma

Background

Allogeneic hematopoietic cell transplantation (allo-HCT) has been proposed as treatment for multiple sclerosis (MS) and other autoimmune diseases.

Aims

To describe the effects of allo-HCT on the course of MS in a 49-year-old woman with longstanding progressive MS who was treated with allo-HCT for follicular lymphoma.

Methods

Non-myeloablative conditioning allo-HCT, examination for IgG oligoclonal bands and measurement of CXCL13 and matrix metalloproteinase-9 (MMP-9) concentration in the cerebrospinal fluid (CSF).

Results

Despite the disappearance of oligoclonal bands in CSF, disease progression and CSF inflammation was observed.

Conclusions

We hypothesize that CXCL13 and MMP-9 detected in CSF may reflect ongoing, pathogenic immune activation even after the eradication of intrathecal IgG synthesis. This suggests that progressive MS may depend more on innate than on adaptive immune activation.

Oxidative stress and reduced glutamine synthetase activity in the absence of inflammation in the cortex of mice with experimental allergic encephalomyelitis

Pathological changes occur in areas of CNS tissue remote from inflammatory lesions in multiple sclerosis (MS) and its animal model experimental allergic encephalomyelitis (EAE). To determine if oxidative stress is a significant contributor to this non-inflammatory pathology, cortex tissues from mice with clinical signs of EAE were examined for evidence of inflammation and oxidative stress. Histology and gene expression analysis showed little evidence of immune/inflammatory cell invasion but reductions in natural antioxidant levels and increased protein oxidation that paralleled disease severity. Two-dimensional oxyblots and mass-spectrometry-based protein fingerprinting identified glutamine synthetase (GS) as a particular target of oxidation. Oxidation of GS was associated with reductions in enzyme activity and increased glutamate/glutamine levels. The possibility that this may cause neurodegeneration through glutamate excitotoxicity is supported by evidence of increasing cortical Ca(2+) levels in cortex extracts from animals with greater disease severity. These findings indicate that oxidative stress occurs in brain areas that are not actively undergoing inflammation in EAE and that this can lead to a neurodegenerative process due to the susceptibility of GS to oxidative inactivation.

Multiple sclerosis: distribution of inflammatory cells in newly forming lesions

OBJECTIVE

CD4 T-cell-dependent macrophage activation directed against a myelin or oligodendrocyte antigen is generally thought to be the mechanism causing myelin destruction in multiple sclerosis (MS). However, areas within expanding MS lesions may exhibit prominent oligodendrocyte loss and apoptosis in the absence of infiltrating lymphocytes. The present study was designed to further investigate the inflammatory profile of different regions within rapidly expanding MS lesions.

METHODS

Twenty-six active lesions from 11 patients with early MS were serially sectioned and immunostained for T and B cells, plasma cells, ramified microglia, macrophages, monocytes, and CD209-positive dendritic cells. Cell counts were compared in prephagocytic, phagocytic, and immediately postphagocytic areas.

RESULTS

Parenchymal T and B cells were largely absent in areas of initial oligodendrocyte loss and in areas of degenerate and dead myelin infiltrated by myelin phagocytes. In contrast, trailing areas of complete demyelination packed with lipid macrophages, and, in some lesions, regenerating oligodendrocytes, showed large numbers of T cells, B cells, and immunoglobulin G (IgG)-positive plasma cells. Lesions in 2 exceptionally early cases contained relatively few T and B cells, and no IgG-positive plasma cells.

INTERPRETATION

Early loss of oligodendrocytes is a prominent feature in tissue bordering rapidly expanding MS lesions. Macrophage activity is largely an innate scavenging response to the presence of degenerate and dead myelin. Adaptive immune activity involving T and B cells is conspicuous chiefly in recently demyelinated tissue, which may show signs of oligodendrocyte regeneration. The findings suggest that plaque formation has some basis other than destructive cell-mediated immunity directed against a myelin or oligodendrocyte antigen.

Restraint stress modulates virus specific adaptive immunity during acute Theiler's virus infection

Multiple sclerosis (MS) is a devastating CNS disease of unknown origin. Multiple factors including genetic background, infection, and psychological stress affect the onset or progression of MS. Theiler's murine encephalomyelitis virus (TMEV) infection is an animal model of MS in which aberrant immunity leads to viral persistence and subsequently results in demyelination that resembles MS. Here, we examined how stress during acute TMEV infection altered virus-specific cell mediated responses. Using immunodominant viral peptides specific for either CD4(+) or CD8(+) T cells, we found that stress reduced IFN-gamma producing virus-specific CD4(+) and CD8(+) T cells in the spleen and CD8(+) T cells CNS. Cytokine production by cells isolated from the CNS or spleens following stimulation with virus or viral peptides, indicated that stress decreased both type 1 and type 2 responses. Glucocorticoids were implicated in the decreased T cell function as the effects of stress were partially reversed by concurrent RU486 administration but mimicked by dexamethasone. As T cells mediate viral clearance in this model, our data support the hypothesis that stress-induced immunosuppression may provide a mechanism for enhanced viral persistence within the CNS.

Autologous haematopoietic stem-cell transplantation in multiple sclerosis

Intense immunosuppression followed by autologous haematopoietic stem-cell transplantation has been assessed over the past few years as a possible new therapeutic strategy in severe forms of multiple sclerosis. Pioneering studies began in 1995, and since then, more than 400 patients worldwide have been treated with this procedure. Small uncontrolled studies show that about 60-70% of treated cases do not progress in the follow-up period of at least 3 years. Transplant-related mortality, which was 5-6% in the first reported series, has reduced in the past 5 years to 1-2%. Relapses dramatically decrease and inflammatory MRI activity is almost completely suppressed. Autologous haematopoietic stem-cell transplantation is associated with qualitative immunological changes in the blood, suggesting that, beyond its immunosuppressive potential, it could also have some beneficial effect for the resetting of the immune system. Patients with severe, rapidly worsening multiple sclerosis who are unresponsive to approved therapies could be candidates for this treatment, but its clinical efficacy has still to be shown in large, prospective, controlled studies.

Autologous and allogeneic hematopoietic stem cell transplantation for Multiple Sclerosis: perspective on mechanisms of action

Multiple Sclerosis (MS) is a frequent demyelinating immune-mediated disease of the central nervous system (CNS) that affects principally young adults and leads to severe physical and cognitive impairment. The current standard treatment makes use of the immune modulators beta-interferon, glatiramer acetate and natalizumab, or immunosuppressants such as mitoxantrone. However, these agents are only partially effective and in a number of patients fail to achieve satisfactory disease control. Autologous hematopoietic stem cell transplantation (HSCT) is being explored in the treatment of severe MS as a means of delivering high-dose immunosuppression followed by 'rescue' of the immuno-hematopoietic system with autologous HSC. The potential therapeutic benefit is based on the concept of so-called 'resetting' the immune system. The use of allogeneic HSCT as a possible therapeutic approach for severe MS is inspired by case reports of MS patients that underwent allogeneic HSCT for a concomitant hematological malignancy, and subsequently is supported by data from rodent models of MS. Allogeneic HSCT may offer specific therapeutic effects, such as the replacement of the autoreactive immune compartment by healthy allogeneic cells and the development of a graft-versus-autoimmunity (GVA) effect. Here, we review the currently available experimental and clinical evidence to support the role of autologous and allogeneic HSCT in MS.