Bone marrow transplantation in multiple sclerosis

Immunopathogenesis of multiple sclerosis: molecular and cellular mechanisms and new immunotherapeutic approaches

BACKGROUND

Multiple sclerosis (MS) is a central nervous system (CNS) demyelinating autoimmune disease with increasing global prevalence. It predominantly affects females, especially those of European descent. The interplay between environmental factors and genetic predisposition plays a crucial role in MS etiopathogenesis.

METHODS

We searched recent relevant literature on reputable databases, which include, PubMed, Embase, Web of Science, Scopus, and ScienceDirect using the following keywords: multiple sclerosis, pathogenesis, autoimmunity, demyelination, therapy, and immunotherapy.

RESULTS

Various animal models have been employed to investigate the MS etiopathogenesis and therapeutics. Autoreactive T cells within the CNS recruit myeloid cells through chemokine expression, leading to the secretion of inflammatory cytokines driving the MS pathogenesis, resulting in demyelination, gliosis, and axonal loss. Key players include T cell lymphocytes (CD4+ and CD8+), B cells, and neutrophils. Signaling dysregulation in inflammatory pathways and the immunogenetic basis of MS are essential considerations for any successful therapy to MS. Data indicates that B cells and neutrophils also have significant roles in MS, despite the common belief that T cells are essential. High neutrophil-to-lymphocyte ratios correlate with MS severity, indicating their contribution to disease progression. Dysregulated signaling pathways further exacerbate MS progression.

CONCLUSION

MS remains incurable, but disease-modifying therapies, monoclonal antibodies, and immunomodulatory drugs offer hope for patients. Research on the immunogenetics and immunoregulatory functions of gut microbiota is continuing to provide light on possible treatment avenues. Understanding the complex interplay between genetic predisposition, environmental factors, and immune dysregulation is critical for developing effective treatments for MS.

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.

Autologous Hematopoietic Stem Cell Transplantation in the Treatment of Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disorder that typically affects young people during their most productive years, causing irreversible damage and accumulation of disability. Treatments over time have had modest effects at completely controlling or suppressing disease activity, but are generally aimed at controlling early dominating inflammation that, over time, accumulates damage and leads to progressive disability. Some unfortunate patients are destined to deteriorate despite even newer and more effective agents because of the inability of these drugs to fully curb the inflammatory component of the disease. These patients require something more that might be capable of halting the disease process. Using high-intensity myeloablative chemotherapeutic agents, it is now possible to completely remove the peripheral immune system and replace it anew from autologous bone marrow-derived hematopoietic stem cells, purged of disease-causing MS cells. This procedure, referred to as hematopoietic stem cell transplantation (HSCT), produces a new immune system that appears tolerant and no longer attacks the central nervous system (CNS).

Oligodendrocytes engineered with migratory proteins as effective graft source for cell transplantation in multiple sclerosis

Multiple sclerosis (MS) is characterized by widespread immunomodulatory demyelination of the CNS resulting in nerve cell dysfunction. Accordingly, treatment strategies have been centered on immunodulation and remyelination, with the former primarily focused on reducing the pathology rather than enhancing myelin repair which the latter targets. While conceding to the emerging view of heterogeneity in the pathology of MS, which precludes variations in degree of immune response (i.e., inflammation) and demyelination, the concept of enhancing myelin repair is appealing since it is likely to provide both disease-reducing and disease-inhibiting therapeutic approach to MS. In this regard, we and several others, have proposed that cell replacement therapy is an effective strategy to repair the myelin in MS. Here, we hypothesize that transplantation of mouse bone marrow-derived oligodendrocytes (BMDOs) and BMDOs transfected with Ephrin proteins (BMDO+Ephrin), which are known to enhance cell and axonal migratory capacity, may produce therapeutic benefits in animal models of MS.

Role of mesenchymal stem cells in neurogenesis and nervous system repair

Bone marrow-derived mesenchymal stem cells (MSCs) are attractive candidates for use in regenerative medicine since they are easily accessible and can be readily expanded in vivo, and possess unique immunogenic properties. Moreover, these multipotent cells display intriguing environmental adaptability and secretory capacity. The ability of MSCs to migrate and engraft in a range of tissues has received significant attention. Evidence indicating that MSC transplantation results in functional improvement in animal models of neurological disorders has highlighted exciting potential for their use in neurological cell-based therapies. The manner in which MSCs elicit positive effects in the damaged nervous system remains unclear. Cell fusion and/or 'transdifferentiation' phenomena, by which MSCs have been proposed to adopt neural cell phenotypes, occur at very low frequency and are unlikely to fully account for observed neurological improvement. Alternatively, MSC-mediated neural recovery may result from the release of soluble molecules, with MSC-derived growth factors and extracellular matrix components influencing the activity of endogenous neural cells. This review discusses the potential of MSCs as candidates for use in therapies to treat neurological disorders and the molecular and cellular mechanisms by which they are understood to act.

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.

Intense immunosuppression in patients with rapidly worsening multiple sclerosis: treatment guidelines for the clinician

Several lines of evidence link immunosuppression to inflammation in patients with multiple sclerosis (MS) and provide a rationale for the increasing use of immunosuppressive drugs in the treatment of MS. Treatment-refractory, clinically active MS can quickly lead to devastating and irreversible neurological disability and treating these patients can be a formidable challenge to the clinician. Patients with refractory MS have been treated with intense immunosuppression, such as cyclophosphamide or mitoxantrone, or with autologous haematopoeitic stem cell transplants. Evidence shows that intense immunosuppression might be effective in patients who are unresponsive to immunomodulating therapy, such as interferon beta and glatiramer acetate. Natalizumab, a new addition to the armamentarium for treating MS, might also have a role in the treatment of this MS phenotype. This Review describes the use of intense immunosuppressant drugs and natalizumab in patients with rapidly worsening MS and provides clinicians with guidelines for the use of these drugs in this patient group.

Stem cell transplantation in Multiple Sclerosis: Safety and Ethics

Stem cell therapy is considered a promising strategy aiming at neuronal and glial cell replacement or neuroprotection in neurological diseases affecting the brain and spinal cord. Multiple Sclerosis (MS), characterized by inflammation-induced destruction of the myelin sheath surrounding axons leading to conduction deficits and variability of clinical signs, is not an exception. MS is considered an autoimmune disease and, in the last few years, an intense immunodepletion followed by autologous hematopoietic-stem-cell transplant (HSCT) is being assessed as potential therapeutical strategy for severe patients unresponsive to the immunomodulatory and immunosuppressive treatment. Partially supported by evidence in animal models and by anecdotal reports on the beneficial effects on MS patients with concomitant malignant diseases, HSCT programs for MS have been initiated worldwide and follow-up data are accumulating. A Consensus Meeting has been held in Milano (1998) providing a document that defined criteria for patient selection, transplantation procedures, and outcome evaluations. Nowadays the high number of patients already treated allows us to draw initial conclusions related to clinical efficacy. After careful monitoring of the available data and improvement of the procedure, safety seems not to be anymore an issue. Ethics of HSCT deserve, on the contrary, a profound evaluation: the procedure is a multistep process with manifold options, each step with different ethical implications. Even more difficult appears the definition of the MS patient selection criteria for HSCT. The informed consensus needs to be exhaustive for the full comprehension of a complex procedure. In conclusion, although HCST is today an established therapeutical option for MS patients, safety and ethical issues need to be further clarified.

Emerging therapies for MS

Immune modulators, such as interferon beta (IFNB) and glatiramer acetate (GA), have focused on T cells as the primary therapeutic target. In the past few year several novel therapeutic strategies have emerged that will be reviewed here. These include treatments that modify the immune balance in general, others that inhibit more specifically various key players of the immune response such as antibody-dependent, and antibody-independent B cell responses in MS, but also some that inhibit migration of inflammatory cells to the central nervous system (CNS). At this time, there are several phase III trials in relapsing-remitting MS with promising agents, including intravenous agents administered once or twice a year (alemtuzumab, rituximab) and oral agents (FTY720, fumaric acid, laquinomod). Finally, new therapeutic approaches are now also addressing neuroprotection and CNS repair.

Autologous Haematopoietic Stem Cell Transplantation for the Treatment of Multiple Sclerosis

Introduction: Autologous haematopoietic stem cell transplantation (auto-HSCT) has been performed for severe multiple sclerosis (MS) refractory to standard therapy with increasing frequency worldwide. However, experience in Asia employing this modality in MS has been limited. In this review, we explored the pathophysiology of autoimmunity and the underlying rationale for auto-HSCT in treating autoimmune diseases including MS, as well as existing published pre-clinical and clinical data. We aimed thereby to better understand the utility of treating MS with auto-HSCT and the feasibility of this procedure in Singapore. Methods: A Medline search was performed with the terms “haematopoietic stem cell transplantation”, “multiple sclerosis” and “autoimmune diseases” from 1996 to 2005. Both original papers and review articles were considered. Main Findings: The majority of publications were from Europe or the United States and most clinical series from single centres had relatively small numbers of patients. Worldwide, the number of patients reported has been less than 300 since 1997. Existing data support the feasibility and promise of this procedure and ongoing Phase III trials may serve to confirm this initial experience. Conclusion: Pre-clinical and early clinical data support the rationale for immunoablative therapy for autoimmune disorders. Auto-HSCT for severe MS is a feasible procedure and can be safely performed in centres with experience managing HSCT patients. Key words: Autoimmunity, Induction of tolerance, Progressive multiple sclerosis

Allogeneic bone marrow transplantation in models of experimental autoimmune encephalomyelitis: evidence for a graft-versus-autoimmunity effect

Autologous hematopoietic stem cell transplantation (HSCT) is being explored in the treatment of severe multiple sclerosis (MS), and is based on the concept of "resetting" the immune system. The use of allogeneic HSCT may offer additional advantages, such as the replacement of the autoreactive immune compartment by healthy allogeneic cells and development of a graft-versus-autoimmunity (GVA) effect. However, in clinical practice, the genetic susceptibility to MS of allogeneic stem cell donors is generally unknown, and GVA may therefore be an important mechanism of action. Experimental autoimmune encephalomyelitis (EAE)-susceptible and -resistant mouse strains were used to determine the roles of genetic susceptibility, level of donor-chimerism, and alloreactivity in the therapeutic potential of syngeneic versus allogeneic bone marrow transplant (BMT) for EAE. After transplantation and EAE induction, animals were evaluated for clinical EAE and ex vivo myelin oligodendrocyte glycoprotein-specific proliferation. Early after BMT, both syngeneic and allogeneic chimeras were protected from EAE development. On the longer term, allogeneic but not syngeneic BMT conferred protection, but this required high-level donor-chimerism from EAE-resistant donors. Importantly, when EAE-susceptible donors were used, robust protection from EAE was obtained when active alloreactivity, induced by donor lymphocyte infusions, was provided. Our findings indicate the requirement of a sufficient level of donor-chimerism from a nonsusceptible donor in the therapeutic effect of allogeneic BMT. Importantly, the data indicate that, independently of genetic susceptibility, active alloreactivity is associated with a GVA effect, thereby providing new evidence to support the potential role of allogeneic BMT in the treatment of MS.

[CARIMS (Cancer Risk In Multiple Sclerosis) project: impact of long-term treatment]

Controversial results have been published on potential link between cancer and multiple sclerosis. Multiple sclerosis has been linked to reduced rates of cancer prior to the era of immunomodulating or immunosuppressive treatments and until today, only 9 studies can be found in the literature. New strategies and early use of IM or IS drugs in MS justify to study and follow patients to detect a potential increase of cancer's incidence in treated patients. It is important to follow and collect prospectively in MS centers, patients with history of cancer, to document histologies, and potential relations with repeated IM or IS treatments. A prospective study is in progress in French MS centers on behalf the Club Francophone de la SEP (CARIMS Project).

Autologous peripheral blood stem cell transplantation for severe multiple sclerosis

We describe the results of a clinical trial to evaluate the feasibility and toxicity of autologous hematopoietic stem cell transplantation (auto-HSCT) for patients with progressive multiple sclerosis (MS). Fifteen patients (all patients with secondary progressive MS) were enrolled. The median expanded disability status scale (EDSS) score at baseline was 6.0 (range, 4.5-7.5). Peripheral blood stem cells were obtained by leukapheresis after mobilization with granulocyte colony-stimulating factor. In 9 patients, CD34+ cell selection was performed with a CliniMACS cell selection system, and 6 patients accepted infusion of unmodified peripheral blood stem cells. The modified BEAM (carmustine, teniposide, cytarabine, and melphalan) was the sole conditioning regimen used. The adverse effects included infections, mucositis, transient hepatotoxicity, and diarrhea. Three patients had flares of neurologic deterioration during mobilization, 8 patients had the same manifestation during transplantation, and 2 patients had similar flares within 3 months of transplantation. Six patients experienced continuous neurologic improvement after transplantation, 5 patients experienced neurologic progression, and 4 patients had stabilization of their disease. The confirmed progression-free rate was 63.8% at 49 months. The results of lymphocyte purging were no better than for no purging. Auto-HSCT proved to be safe and beneficial for some MS patients. Further studies are needed to establish the merit of this procedure for MS patients.

Intense T cell depletion followed by autologous bone marrow transplantation for severe multiple sclerosis

BACKGROUND

Certain stem cell transplantation procedures might slow down inflammatory pathology in multiple sclerosis (MS).

AIMS

To halt disease progression in aggressive MS by a bone marrow transplantation (BMT) protocol aimed at maximum T cell suppression.

METHODS

Autologous BMT was performed in 14 patients with rapid secondary progressive MS (median EDSS score at baseline, 6; median disease duration, five years). To accomplish rigorous T cell ablation, a strong conditioning protocol was chosen--cyclophosphamide, total body irradiation, and antithymocyte globulin. To minimise the possibility of reinfusing mature T cells in the graft, bone marrow, not peripheral blood, was used as the CD34+ stem cell source.

RESULTS

Median follow up was 36 months (range, 7-36). Post-transplant haemopoietic recovery was successful in all patients. Early toxicity included Epstein-Barr virus related post-transplantation lymphoproliferative disorder. Longterm effects were development of antithyroid antibodies (three) and myelodysplastic syndrome (one). One patient died of progressive disease five years after transplantation. Treatment failure, defined by EDSS increase sustained for six months or more, was seen in nine patients and stabilisation or improvement in five. Other clinical parameters generally showed the same outcome. No gadolinium enhanced lesions were seen on post-treatment magnetic resonance imaging, in either cerebral or spinal cord scans. However, cerebrospinal fluid oligoclonal bands remained positive in most cases.

CONCLUSIONS

This strong immunosuppressive regimen did not prevent clinical progression in patients with aggressive secondary MS. The lack of efficacy, together with some serious side effects, does not favour the use of similar rigorous T cell depleting protocols in the future.

Tolerance induction by bone marrow transplantation in a multiple sclerosis model

Experimental autoimmune encephalomyelitis (EAE) in rats is a highly valuable model of multiple sclerosis (MS) because it mimics major hallmarks of the human disease. EAE induced with myelin-oligodendrocyte-glycoprotein (MOG) in DA rats is relapsing/remitting, and lesions in the central nervous system show inflammation, demyelination, and axonal and neuronal loss. Recently, bone marrow transplantation (BMT) was introduced as a novel strategy to treat MS, but its efficiency and the underlying mechanism are debatable. In MOG-induced EAE we found that BMT at the peak of EAE but not in the chronic phase leads to disease attenuation. In both settings, rats receiving bone marrow (BM) transplants were protected from subsequently induced relapses. These findings could be confirmed by histopathology in which rats receiving BM transplants did not have lesions compared with controls not receiving transplants. Importantly, the protective effect was achieved by allogeneic, syngeneic, and BM grafts from diseased rats. BMT resulted in increased numbers of CD4(+)CD25(bright) regulatory T cells, increased Foxp3 expression, a shift in T-cell epitope recognition, and a strong reduction of autoantibodies even after rechallenge with MOG. Thus, our results indicate potential mechanisms of how BMT may contribute to the improvement of MS and provide a rationale for its application in patients suffering from various autoimmune diseases.

Haemopoietic stem cell transplantation in autoimmune diseases: a European perspective

The potential of haemopoietic stem cell transplantation (HSCT) for the treatment of autoimmune and inflammatory diseases was originally supported by almost three decades of animal experiments and by the serendipitous remissions of autoimmune disease observed in patients undergoing transplantation for haematological disorders. Improved safety of both autologous and allogeneic HSCT over the last decade has been followed by increasing acceptance of HSCT as an experimental treatment for severe autoimmune diseases that are resistant to conventional treatment. International databases have collated over 700 procedures performed specifically for a variety of autoimmune diseases. Phase III clinical trials are in progress for some diseases. This review provides a comprehensive update on the efficacy and toxicity of HSCT in severe autoimmune disease. Future directions in the context of other evolving therapies are discussed.

Waldenström's macroglobulinemia developing in a patient with multiple sclerosis: coincidence or association?

Multiple sclerosis (MS) has been reported in association with haematological abnormalities, including monoclonal gammopathies. We present a 54-year-old male patient with a 30-year history of MS who was admitted to our hospital for investigation of anaemia and increased erythrocyte sedimentation rate. A monoclonal IgM protein was detected by serum protein immunofixation, while bone marrow biopsy indicated a 70% infiltration by small lymphoplasmacytoid cells, in the context of a lymphoplasmacytoid immunocytoma, findings compatible to the diagnosis of Waldenström's macroglobulinemia (WM). To our knowledge, this is the first report of WM in a patient with MS. Further to the coexistence of the two diseases observed in the case presented here, there is additional evidence suggesting that the association of MS with plasma cell dyscrasias may not be coincidental.

Autologous haematopoietic-stem-cell transplantation for multiple sclerosis

Intense immunosuppression followed by autologous haematopoietic-stem-cell transplantation (HSCT) is being assessed as a potential treatment for patients with severe multiple sclerosis (MS). The treatment was developed from research that showed autologous HSCT was as effective as allogeneic HSCT in the treatment of experimental autoimmune encephalomyelitis. The treatment is thought to eradicate the defective immune system, and the infused haematopoietic stem cells reconstitute an immune system that is more tolerant to the nervous system. About 250 patients with MS have been treated with autologous HSCT as part of phase I and phase II open trials. Autologous HSCT seems feasible in MS and assessment with clinical and MRI measures suggests it induces a profound and long-lasting suppression of inflammation. The course of MS seems to be stabilised after autologous HSCT, especially in ambulatory patients with evidence of active disease. Autologous HSCT deserves further study in randomised controlled trials.

Stem cell transplantation for autoimmune disorders. Coincidental autoimmune disease in patients transplanted for conventional indications

The practice of stem cell transplantation for severe autoimmune diseases refractory to conventional therapy originated from two landmark discoveries: the excellent results of animal experiments, and serendipitous observations in human coincidental diseases. The latter include patients with an often long-standing autoimmune disease who have developed a haematological condition (aplasia, leukaemia, lymphoma) requiring stem cell transplantation (from marrow as well as from blood). Allogeneic and autologous transplants have been performed. The initial information deriving from both procedures is their feasibility, even more convincing since the patients were affected by two simultaneous severe diseases. The information derived from autologous transplants has, however, now been superseded by the considerable and increasing number of those transplants performed for primary autoimmune diseases. On the other hand, allogeneic stem cell transplantation for very severe autoimmune diseases is being cautiously explored in current protocols. Allogeneic transplants in coincidental disease have also suggested a graft-versus-autoimmunity effect, which may become relevant in conjunction with non-myeloablative, less toxic condition regimens.

High-dose immunosuppression and autologous hematopoietic stem cell rescue for severe multiple sclerosis

Multiple sclerosis is a relatively common and seriously disabling disease of autoimmune pathogenesis, for which there is currently no cure. Available therapies include immunomodulating agents and standard-dose immunosuppressants, which may be helpful but are not curative. Recently, studies in animal models have indicated that control of autoimmune disease can be obtained by high-dose immunosuppression followed by hematopoietic stem cell transplantation (rescue). Autologous transplants for severe and refractory multiple sclerosis were proposed in 1997 and have been performed ever since in selected patients and in the context of phase I/II trials. To date, more than 200 patients have been treated worldwide, and similar results were obtained in different centers: high-dose therapy suppresses inflammation in the brain to a degree superior to any other conventional therapy and seems to delay significantly clinical disease progression. There is, however, a procedure-related mortality risk of 1.5-5%, requiring careful patient selection before transplant. The treatment should be reserved for patients having high chance of response, i.e., young patients with low disability scores but rapidly progressing disease, having inflammatory rather than neurodegenerative changes in the central nervous system. The mechanism of action of transplantation is unclear. The initial concept of immune ablation by high-dose therapy and reconstitution of normal immunity from transplant-derived lymphocyte progenitors has given way to the concept of "resetting" the immune system and of bringing the disease to a lower level of activity. One could also speculate on a tissue repair effect, given the ability of human hematopoietic stem cells to migrate also into the central nervous system. The clinical effect of transplantation remains to be demonstrated in a randomized study. The Autoimmune Disease Working Party of the European Group for Blood and Marrow Transplantation has launched such a trial, comparing transplantation to the currently best available therapy, i.e., mitoxantrone, and in about 5 years we should know whether transplantation offers more than the benefit of a transient immunosuppressive effect.

Autologous hemopoietic stem cell transplantation in the treatment of multiple sclerosis: rationale and clinical experience

Based on the encouraging results of transplantation in animals with experimental autoimmune encephalomyelitis (EAE), small-scale phase I/II trials of autologous hematopoietic stem cell transplantation (autoHSCT) were initiated in 1995 for the treatment of severe cases of multiple sclerosis (MS). More than 200 patients with treatment-resistant multiple sclerosis have been transplanted so far, mainly in Europe and the USA. The results of these studies appear promising in terms of impact on MRI disease parameters and, to a lesser extent, clinical stabilization or even improvement. Despite concerns raised by the morbidity and mortality noted in the initial pilot studies, a controlled, randomized, phase III trial of autoHSCT against the best currently available treatment, i.e., mitoxantrone, seems justified and is under way.

Multiple sclerosis

Autologous transplants for severe and refractory multiple sclerosis (MS) were proposed in 1997 and have been performed on about 200 selected patients worldwide. Phase I/II clinical studies have shown that high-dose immunosuppressive therapy suppresses inflammation in the CNS and may delay the progression of clinical disease. The procedure is associated with toxicity from the high-dose cytotoxic therapy and a risk of serious infections. There is a transplant-related mortality risk of 1-5%, requiring careful patient selection before transplantation. Treatment should be reserved for patients who have a significant chance of response, i.e. young patients with low disability scores but rapidly progressing disease who have inflammatory rather than neurodegenerative changes in the CNS. The long term effect of high-dose immunosuppression after transplantation on the frequency of relapse or progression of MS is unclear, but the initial concept of immune ablation by high-dose therapy and the reconstitution of normal immunity and tolerance from transplant-derived lymphocyte progenitors has given way to the concept of 'resetting' the immune system. The clinical effect of transplantation remains to be demonstrated in comparative studies.

Emerging disease modifying therapies for multiple sclerosis

Multiple sclerosis (MS), the most common central nervous system (CNS) demyelinating disease, is thought to be mediated in part by CNS autoantigen-specific T cells. The aetiology of the disease is unclear, but includes genetic and environmental factors. The disease onset often occurs in young adults and is characterised by bouts of neurological symptoms such as numbness, weakness, imbalance or visual difficulties that may not be recovered from. Sometimes the course is more progressive. Since the disease can be disabling, several treatments have been developed that reduce the risk of relapse and progression of sustained disability. Although earlier treatment is encouraged, currently approved disease modifying therapies for MS are only partially effective, administered parenterally and associated with significant side effects and potential toxicities. Therefore, many promising new therapies are under development that target various goals, including immunosuppression, immunomodulation, cell traffic through the blood-brain barrier (BBB), neuroprotection and enhancement of CNS repair.

Stem cell transplantation for multiple sclerosis: What is the evidence?

Experimental and clinical observations have indicated that high-dose immunosuppression followed by autologous stem cell transplantation (ASCT) can induce remissions in severe, refractory, autoimmune diseases including multiple sclerosis (MS), a T cell-mediated autoimmune disorder against CNS myelin components, causing severe chronic disability. Control of the disease is unsatisfactory in most of the patients, especially those with rapidly evolving relapsing-remitting course and those with chronic progressive disease. The rationale for treating autoimmune diseases with ASCT is based on the immunosuppressive and immunomodulating effects of ASCT which may shift the immunological balance towards disease quiescence, a hypothesis supported by the results of ASCT in animal models of MS and by clinical observations in MS patients transplanted for concurrent malignancies. A number of phase I-II studies of ASCT in patients with active MS, conducted worldwide since 1995, and a comprehensive analysis of 85 patients, recently reported by the European Group for Blood and Marrow Transplantation (EBMT), have shown the feasibility of the method, a prominent anti-inflammatory effect on magnetic resonance imaging (MRI) disease, and a possible clinical benefit for active and refractory cases. The impact on MRI disease parameters appears superior with ASCT than with conventional therapies but the clinical results, in terms of stabilization of disease and prevention of disability, need to be validated in prospective, controlled trials. The procedure is also associated with a transplant-related mortality risk, of about 5% in high-risk cases, i.e., in older patients, those with high disability scores, those receiving strong myeloablative conditioning regimens and those undergoing intensive in vivo or ex vivo T cell-depletion. Therefore, it could be recommended for the treatment of a chronic, non-lethal, disease like MS only if it proved superior to standard therapies. A randomized trial is now launched by the EBMT to compare ASCT to mitoxantrone, currently regarded as one of the best available treatments, in properly selected patients having high chance of response at minimal mortality risk.

Hematopoietic stem cell transplantation for multiple sclerosis: finding equipoise

Hematopoietic stem cell transplantation of multiple sclerosis is rapidly expanding. Success for this approach requires an understanding of the pathophysiology of multiple sclerosis and design of trials that select patients with active inflammatory disease, low disability scores, and avoidance of conditioning agents that may damage neural stem cell compartments or further compromise already injured axons.

Celiac disease: a model autoimmune disease with gene therapy applications

Gene therapy (GT) is still at the 'experimental' stage and some recent setbacks have cooled the potential use of this therapeutic tool even in life-threatening conditions. However, this therapeutic approach has a potential, which is not limited to disease for which we have not other option. There are increasing evidence that GT will be soon used in diseases that are not life threatening. One group of diseases that can benefit from GT is the autoimmune one. Several experimental animal models have indicated the efficacy (proof of principle) of GT. In the present review, we have addressed the possibility that even extremely benign autoimmune-like diseases such as Celiac Disease (CD) might one day profit from this type of therapy. We further point that in conditions such as CD, where the trigger is well known and the pathogenic cascade is relatively well defined, a situation not common in autoimmunity, we can even have a better situation where to explore and use GT to control disease initiation and progression. Once the risks that are still intrinsic to GT will have been reduced the therapeutic options we outline in the present review might not appear too far from reality.

Clinically demonstrable anti-autoimmunity mediated by allogeneic immune cells favorably affects outcome after stem cell transplantation in human autoimmune diseases

To determine the role of allogeneic, autologous and syngeneic hemopoietic stem cell transplantation (SCTx) as a treatment for severe autoimmune disease (AID) we performed a literature search employing Medline, Cancer Lit and abstract books for reports on transplants for blood disorders and a concomitant AID. All reviews, case reports and abstracts available between June 1977 and September 2001 were used and attempts made to update them by e-mail by the corresponding authors. Disease-free survival (DFS) after allogeneic SCTx for 23 patients with severe aplastic anemia was 78% at 16 years and survival in unmaintained remission of concomitant AID was 64% at 13 years. DFS after allogeneic SCTx for 24 patients with hematologic malignancies was 87% at 15 years and survival in unmaintained remission for concomitant AID was 70% at 11 years. DFS after autologous SCTx for 24 patients with hematologic malignancies was 48% at 6 years and survival in unmaintained remission for concomitant AID was 29% at 3 years. Among 30 patients given allogeneic SCTx 19 developed graft-versus-host disease (GVHD) and 11 did not. Upon clinically justified discontinuation of all immunosuppressive therapy, 3/11 patients without GVHD relapsed with their concomitant AID (freedom of AID-relapse 69% at 9 years), whereas none of 19 patients with GVHD did so (log rank: P = 0.0135). Freedom of AID-relapse was superior after allo SCTx compared to autologous SCTx (89% at 18 years vs 38% at 5 years; log rank: P = 0.0002). Our data suggest that a graft-versus-autoimmunity effect after allogeneic hemopoietic SCTx mediates elimination of autoimmunity.

Induction of tolerance in autoimmune diseases by hematopoietic stem cell transplantation: getting closer to a cure?

Hematopoietic stem cells (HSCs) are the earliest cells of the immune system, giving rise to B and T lymphocytes, monocytes, tissue macrophages, and dendritic cells. In animal models, adoptive transfer of HSCs, depending on circumstances, may cause, prevent, or cure autoimmune diseases. Clinical trials have reported early remission of otherwise refractory autoimmune disorders after either autologous or allogeneic hematopoietic stem cell transplantation (HSCT). By percentage of transplantations performed, autoimmune diseases are the most rapidly expanding indication for stem cell transplantation. Although numerous editorials or commentaries have been previously published, no prior review has focused on the immunology of transplantation tolerance or development of phase 3 autoimmune HSCT trials. Results from current trials suggest that mobilization of HSCs, conditioning regimen, eligibility and exclusion criteria, toxicity, outcome, source of stem cells, and posttransplantation follow-up need to be disease specific. HSCT-induced remission of an autoimmune disease allows for a prospective analysis of events involved in immune tolerance not available in cross-sectional studies.

Autologous stem cell transplants in treatment of multiple sclerosis: where we stand and future prospects

Based on experimental and clinical observations, high-dose immunosuppression followed by autologous transplantation may induce remissions in severe, refractory, autoimmune disorders including multiple sclerosis, a disease which, in its progressive form, does not respond to treatment. Phase I/II studies of transplantation in MS published by individual centers as well as a comprehensive analysis of the reports to the EBMT registry have shown that transplantation may positively affect MS by stabilizing the clinical condition of the patients, by improving their disability status, and by completely abrogating the inflammatory process in the brain as evidenced in magnetic resonance imaging. Other available therapies do not appear to be so efficacious as transplantation. However, the procedure is associated with a transplant-related mortality risk of about 3 to 8%. Therefore, it cannot be recommended for the treatment of a chronic, non-lethal, disease like MS unless it proves superior to standard therapies in terms of efficacy. This can be demonstrated only in a randomized trial, which is being launched by the EBMT under the name ASTIMS. It compares the BEAM regimen plus autotransplantation to mitoxantrone, which is currently regarded as one of the best available treatments, in patients with secondary progressive or rapidly evolving relapsing/remitting multiple sclerosis.

Differentiation of multiple sclerosis subtypes: implications for treatment

There has been tremendous progress in the immunomodulatory treatment of multiple sclerosis (MS) during recent years. With the introduction of interferon-beta, glatiramer acetate and mitoxantrone (recently registered for MS in the US), there are at least three therapeutic strategies that have proven effective in large phase III studies. However, not all patients with MS respond well to treatment with these drugs. This may largely be a consequence of disease heterogeneity. From a clinical perspective, patients with different disease courses show different treatment responses. Patients with relapsing-remitting MS are more likely to respond to immunomodulatory therapy than those with a progressive disease course. Studies of patients with secondary progressive MS have yielded inconsistent results and, so far, there has been no positive phase III study of immunomodulatory therapy in patients with primary progressive MS. Pathological evidence indicates that subtyping based on clinical findings alone does not reflect actual disease heterogeneity. In a large series of biopsy and autopsy specimens, at least four subtypes could be identified with respect to oligodendrocyte/myelin pathology and immunopathology. As long as the only method of identifying subtypes of disease is histopathology, differential therapy will remain a future goal. Thus, there is an urgent need for in vivo markers of immunopathogenesis in an individual patient that would allow treatment to be specifically directed towards a given pathological focus. However, at least from a theoretical point of view, some therapeutic approaches appear very attractive. Plasmapheresis and/or intravenous immunoglobulins could most plausibly be the best approach for the immunopathological subtype of MS, which is characterised by antibody and complement deposition next to demyelinated axons, in order to remove antibodies. The subtype of MS that is associated with heavy macrophage activation, T cell infiltration and expression of inflammatory mediator molecules, including tumour necrosis factor-alpha, may be most likely to respond to immunomodulation with interferon-beta or glatiramer acetate. There are other subtypes of MS in which viral infection or oligodendrocyte degeneration, rather than autoimmunity, appear to play a role. It is possible that these could benefit from antiviral therapy, oligodendrocyte protection or oligodendrocyte transplantation, although therapies based on these latter approaches have yet to be developed.

Primary progressive multiple sclerosis: increasing clarity but many unanswered questions

Heterogeneity in the clinical course of multiple sclerosis (MS) is well recognised and patients following a primary progressive course, 10-15% of the MS population, have a distinct clinical and paraclinical phenotype. This review examines recent advances in our understanding of this subgroup of patients and examines the new criteria to be applied in diagnosis. It also highlights developments in genetic, immunological, magnetic resonance and pathological aspects of the disease, whilst also outlining the results of recent therapeutic trials.

Treatment of neural injury with marrow stromal cells

We describe our preclinical studies on the use of bone-marrow stromal cells (MSC; an uncharacterised mixed population of plastic-adherent cells) in the treatment of neural injury. These cells obtained from donor rats or human beings have been directly transplanted into brain or administered intra-arterially or intravenously. MSC selectively target injured tissue and promote functional recovery. Signals that target inflammatory cells to injured tissue probably direct MSC to injury sites. Although some MSC express proteins typical of neural cells, the possibility that benefit is derived by replacement of infarcted tissue with differentiated MSC is highly unlikely. MSC activate endogenous restorative responses in injured brain, which include angiogenesis, neurogenesis, and synaptogenesis. Given the robust therapeutic benefit of these cells in the treatment of experimental neural injury, and the fact that MSC have been used in the treatment of other human disease, there is justification for further preclinical studies leading to clinical trials for the treatment of neural injury such as stroke.

Microchimerism in autoimmunity and transplantation: potential relevance to multiple sclerosis

Microchimerism (MC) is the stable presence of small numbers of non-host cells and appears to be commonly present in parous women. There are several methods of detecting microchimerism and each has advantages for different types of studies, but the risk of contamination and the differing levels of sensitivity lead to difficulties in estimating the proportion of individuals that are microchimeric. Recent observations of an increased frequency of microchimerism in women with scleroderma and Hashimoto's thyroiditis suggest that microchimerism may increase the risk of developing autoimmune disease. Inferences regarding autoimmunity are drawn from the immunological effects of organ and bone-marrow transplantation. Potential research questions regarding microchimerism, human leukocyte antigen (HLA) similarity, and autoimmune diseases in the context of multiple sclerosis (MS) are discussed.

Stem cell transplantation in multiple sclerosis: multiple choices and multiple challenges

Multiple sclerosis (MS) is generally considered as an autoimmune disease of the central nervous system. This concept has led to the idea that profound immunosuppression followed by transplantation of stem cell grafts would stop, or at least slow down, disease activity. Supported by the positive effects of hematopoietic stem cell transplantation (HSCT) on experimental autoimmune encephalomyelitis and by anecdotal reports on the beneficial effect of HSCT on MS patients with concomitant malignant disease, HSCT programs for MS have been initiated worldwide. At this stage, it is impossible to draw general conclusions from the preliminary data reported and therefore overenthusiastic expectations should be tempered. The follow-up periods are too short the groups are too small, the selected patients and protocols too heterogeneous, and publication bias on positive results cannot be excluded. However, there is ample evidence that HSCT is a technically feasible approach in MS, not more dangerous than in the hemato-oncological diseases. For every step in the HSCT procedure, there are many different options. The time has come for a systematic analysis of the safety and efficacy associated with the different methodologies.

Engraftment syndrome: a common cause for rash and fever following autologous hematopoietic stem cell transplantation for multiple sclerosis

Autologous hematopoietic stem cell transplantation (HSCT) is currently being evaluated as a therapy for patients with progressive multiple sclerosis (MS) at risk of debilitating neurological impairment. While preliminary results from a few studies have been reported, little is known about toxicities or outcome of HSCT for MS. We report a relatively frequent triad of non-infectious fever, rash and fatigue or lassitude that may also be associated with pruritus, pulmonary symptoms, and eosinophilia and frequently occurs around engraftment. This syndrome occurred in 26% of our series of patients (5/19) undergoing HSCT for multiple sclerosis. The engraftment syndrome is usually self-limited but may require intervention with systemic corticosteroids.