PML: The Dark Side of Immunotherapy in Multiple Sclerosis

Update on the role of T cells in cognitive impairment

The central nervous system (CNS) has long been considered an immune-privileged site, with minimal interaction between immune cells, particularly of the adaptive immune system. Previously, the presence of immune cells in this organ was primarily linked to events involving disruption of the blood-brain barrier (BBB) or inflammation. However, current research has shown that immune cells are found patrolling CNS under homeostatic conditions. Specifically, T cells of the adaptive immune system are able to cross the BBB and are associated with ageing and cognitive impairment. In addition, T-cell infiltration has been observed in pathological conditions, where inflammation correlates with poor prognosis. Despite ongoing research, the role of this population in the ageing brain under both physiological and pathological conditions is not yet fully understood. In this review, we provide an overview of the interactions between T cells and other immune and CNS parenchymal cells, and examine the molecular mechanisms by which these interactions may contribute to normal brain function and the scenarios in which disruption of these connections lead to cognitive impairment. A comprehensive understanding of the role of T cells in the ageing brain and the underlying molecular pathways under normal conditions could pave the way for new research to better understand brain disorders. LINKED ARTICLES: This article is part of a themed issue From Alzheimer's Disease to Vascular Dementia: Different Roads Leading to Cognitive Decline. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.6/issuetoc.

Progressive Multifocal Leukoencephalopathy: Pathogenesis, Diagnostic Tools, and Potential Biomarkers of Response to Therapy

JC polyomavirus (JCV) establishes an asymptomatic latent and/or persistent infection in most of the adult population. However, in immunocompromised individuals, JCV can cause a symptomatic infection of the brain, foremost progressive multifocal leukoencephalopathy (PML). In the past 2 decades, there has been increasing concern among patients and the medical community because PML was observed as an adverse event in individuals treated with modern (selective) immune suppressive treatments for various immune-mediated diseases, especially multiple sclerosis. It became evident that this devastating complication also needs to be considered beyond the patient populations historically at risk, including those with hematologic malignancies or HIV-infected individuals. We review the clinical presentation of PML, its variants, pathogenesis, and current diagnostic approaches. We further discuss the need to validate JCV-directed interventions and highlight current management strategies based on early diagnosis and restoring JCV-specific cellular immunity, which is crucial for viral clearance and survival. Finally, we discuss the importance of biomarkers for diagnosis and response to therapy, instrumental in defining sensitive study end points for successful clinical trials of curative or preventive therapeutics. Advances in understanding PML pathophysiology, host and viral genetics, and diagnostics in conjunction with novel immunotherapeutic approaches indicate that the time is right to design and perform definitive trials to develop preventive options and curative therapy for JCV-associated diseases.

Immunosenescence and multiple sclerosis: inflammaging for prognosis and therapeutic consideration

Aging is associated with a progressive decline of innate and adaptive immune responses, called immunosenescence. This phenomenon links to different multiple sclerosis (MS) disease courses among different age groups. While clinical relapse and active demyelination are mainly related to the altered adaptive immunity, including invasion of T- and B-lymphocytes, impairment of innate immune cell (e.g., microglia, astrocyte) function is the main contributor to disability progression and neurodegeneration. Most patients with MS manifest the relapsing-remitting phenotype at a younger age, while progressive phenotypes are mainly seen in older patients. Current disease-modifying therapies (DMTs) primarily targeting adaptive immunity are less efficacious in older patients, suggesting that immunosenescence plays a role in treatment response. This review summarizes the recent immune mechanistic studies regarding immunosenescence in patients with MS and discusses the clinical implications of these findings.

Type O blood group associates with higher anti-JC polyomavirus antibody levels

BACKGROUND

Patients with multiple sclerosis (MS) and high anti-JC polyomavirus (JCPyV) antibodies in blood have an increased risk for the development of progressive multifocal leukoencephalopathy (PML) when treated for MS. To test the hypothesis that type O blood group associates with anti-JCPyV antibody levels and the risk of developing PML, we characterized ABO blood group antigen on blood samples of 62 patients with PML, and 64 MS controls without PML.

METHODS

Monocentric retrospective cohort study. Anti-JCPyV antibody levels in arbitrary units (AU) were determined in sera using an ELISA-based method, and blood group specific antibodies using standardised test erythrocytes.

RESULTS

Anti-JCPyV antibody levels were higher in individuals with blood group O compared with all other blood groups (O: median AU: 129; not O: median AU: 53; p = .005). This association was not observed for the closely related BK virus. Of the 62 patients with PML, 29 (47%, 95% confidence interval (CI) 35%-59%) were of blood group O, which showed a nonsignificant trend to differ from the expected distribution in the German population (41%), and the MS controls studied (36%, 95% CI 25%-48%).

CONCLUSION

The ABO blood group O antigen associates with higher anti-JCPyV antibody levels and may impact the risk of the later development of PML. The overrepresentation of blood group O in cases with PML was in line with a previous publication. Larger studies are warranted to assess a potential value of host genetic markers, such as the ABO status, for PML risk prediction during immunotherapy.

Pharmacovigilance during treatment of multiple sclerosis: early recognition of CNS complications

An increasing number of highly effective disease-modifying therapies for people with multiple sclerosis (MS) have recently gained marketing approval. While the beneficial effects of these drugs in terms of clinical and imaging outcome measures is welcomed, these therapeutics are associated with substance-specific or group-specific adverse events that include severe and fatal complications. These adverse events comprise both infectious and non-infectious complications that can occur within, or outside of the central nervous system (CNS). Awareness and risk assessment strategies thus require interdisciplinary management, and robust clinical and paraclinical surveillance strategies. In this review, we discuss the current role of MRI in safety monitoring during pharmacovigilance of patients treated with (selective) immune suppressive therapies for MS. MRI, particularly brain MRI, has a pivotal role in the early diagnosis of CNS complications that potentially are severely debilitating and may even be lethal. Early recognition of such CNS complications may improve functional outcome and survival, and thus knowledge on MRI features of treatment-associated complications is of paramount importance to MS clinicians, but also of relevance to general neurologists and radiologists.

Diagnostic and therapeutic issues of inflammatory diseases of the elderly

Inflammatory diseases of the central nervous system (CNS) mainly occur during early adulthood and multiple sclerosis (MS) represents the overwhelming majority of these disorders. Nevertheless, MS only rarely begins after 50 years and a diagnosis of late-onset MS should only be done when clinical as well as radiological and biological findings are typical of MS since the probability of misdiagnosis is higher in elderly patients. Indeed, in patients aged over 50 years, along with a relative decrease of MS incidence, other inflammatory diseases of the CNS but also differential diagnoses including neoplastic as well as infectious disorders should be thoroughly searched to avoid diagnostic mistakes and the prescription of inadequate and potentially harmful immunomodulatory/immunosuppressive therapies. Moreover, aging is associated with diverse immune changes also known as immunosenescence resulting in, notably, higher risk of comorbidities (including vascular diseases) and infections which need to be considered when planning medical treatments of elderly patients with inflammatory diseases of the CNS. Herein, therapeutic and diagnostic challenges faced by neurologists are reviewed to ease patient management.

Age and the risks of high-efficacy disease modifying drugs in multiple sclerosis

PURPOSE OF REVIEW

A variety of high-efficacy disease-modifying therapies (DMTs) are available for the treatment of multiple sclerosis (MS). After evaluation and approval by regulatory agencies, DMTs are likely to be administered to patients whose characteristics differ from those enrolled in clinical trials. This may contribute to the emergence of unexpected adverse events observed in the real-world setting. Higher age may be a relevant factor that could change the benefit-risk balance of DMTs, as it may associate with lower efficiency and higher frequency of adverse events.

RECENT FINDINGS

The absolute and relative number of patients with MS who reach the age of 55 and higher increases. Growing evidence demonstrates lower efficacy of DMTs in older persons with MS. Specific risks during DMTs for MS, such as the risk of developing progressive multifocal leukoencephalopathy (PML) or the outcome following PML, have been associated with age. It is hypothesized that age-related and therapy-induced alterations to the immune system may have (super)additive effects, resulting in an acceleration of physiological immunosenescence and inflamm-aging.

SUMMARY

In this article, we review the risks of high-efficacy DMTs in MS with a specific focus on age-related efficacy and risks, including opportunistic infections, malignancies, and autoimmune reactions.

Therapeutic Effect of the Mitochondria-Targeted Antioxidant SkQ1 on the Culture Model of Multiple Sclerosis

Multiple sclerosis (MS) is a heterogeneous autoimmune disease of unknown etiology characterized by inflammation, demyelination, and axonal degeneration that affects both the white and gray matter of CNS. Recent large-scale epidemiological and genomic studies identified several genetic and environmental risk factors for the disease. Among them are environmental factors of infectious origin, possibly causing MS, which include Epstein-Barr virus infection, reactivation of some endogenous retrovirus groups, and infection by pathogenic bacteria (mycobacteria, Chlamydia pneumoniae, and Helicobacter pylori). However, the nature of the events leading to the activation of immune cells in MS is mostly unknown and there is no effective therapy against the disease. Amazingly, whatever the cause of the disease, signs of damage to the nerve tissue with MS lesions were the same as with infectious leprosy, while in the latter case nitrozooxidative stress was suggested as the main cause of the nerve damage. With this in mind and following the hypothesis that excessive production of mitochondrial reactive oxygen species critically contributes to MS pathogenesis, we studied the effect of mitochondria-targeted antioxidant SkQ1 in an in vitro MS model of the primary oligodendrocyte culture of the cerebellum, challenged with lipopolysaccharide (LPS). SkQ1 was found to accumulate in the mitochondria of oligodendrocytes and microglial cells, and it was also found to prevent LPS-induced inhibition of myelin production in oligodendrocytes. The results implicate that mitochondria-targeted antioxidants could be promising candidates as components of a combined therapy for MS and related neurological disorders.

Self-Limited Cytomegalovirus Infection During Natalizumab Treatment for Multiple Sclerosis

Natalizumab is indicated as monotherapy for the treatment of relapsing-remitting multiple sclerosis; it prevents outbreaks and delays the progression of physical disability. Here, we report the case of a 30-year-old patient with multiple sclerosis receiving natalizumab as monotherapy who subsequently developed self-limited cytomegalovirus disease. Cytomegalovirus infection has been reported during treatment with natalizumab, and in this study, we use new techniques to analyze the possible association of cytomegalovirus infection with natalizumab.

LEARNING POINTS

Natalizumab is a humanized recombinant monoclonal antibody (IgG4k) against α4-integrin which promotes immunocompromise by blocking the adhesion interactions necessary for lymphocyte trafficking.Cytomegalovirus infection has been described during natalizumab treatment, although the pathogenesis and mechanisms are not complete understood.This case highlights the importance of awareness of this association and possible complications.

Managing Multiple Sclerosis: Treatment Initiation, Modification, and Sequencing

Recent therapeutic advances in the management of multiple sclerosis (MS) have raised questions about the selection of appropriate patient candidates for various treatments and, if the plan is to move from one treatment to another, the appropriate sequencing of these therapies. The selected approach should provide optimal disease management without limiting future therapeutic options based on safety concerns, and recognize potential future treatments and the possibility of combination therapies. Additional challenges include incorporation of patient needs and preferences into the overall therapeutic approach, in order to ensure optimal outcomes in the short and long term. The objective of this manuscript is to provide an overview of what is currently known regarding the impact of various therapies for MS on future therapeutic choices (sequencing). In this context, we reviewed the available evidence in support of various treatments and, based on the presence of disease activity, suggested a scheme for switching or escalating therapy with the main focus on sequencing of therapeutic approaches.

Survivorship and Outcomes in Patients With Multiple Sclerosis Undergoing Total Joint Arthroplasty

BACKGROUND

Patients with multiple sclerosis (MS) frequently require total joint arthroplasty (TJA). The outcomes of TJA in patients with MS, who are frequently on immunomodulatory medications and physically deconditioned, remain largely unknown. The aim of this study is to elucidate the survivorship and reasons for failure in this patient population.

METHODS

A single-institution retrospective review of 108 TJAs (46 knees and 62 hips) was performed from 2000 to 2016. An electronic chart query based on MS medications and International Classification of Diseases, Ninth Revision codes was used to identify this population followed by a manual review to confirm the diagnosis. Outcomes were then assessed using revision for any reason as the primary end point. Functional outcomes were assessed using Short Form 12 scores. Survivorship curves were generated using the Kaplan-Meier method.

RESULTS

At an average follow-up of 6.2 years, 19.4% (21/108) of patients required a revision surgery. Instability (5.6%, P = .0278) and periprosthetic joint infection (4.6%, P = .0757) were among the most common reasons for revision. The overall survivorship of TJA at years 2, 5, and 7, respectively, was 96.5% (95% confidence interval [CI], 92.6-100), 86.3% (95% CI, 77.7-94.5), and 75.3% (95% CI, 63.5-87.0). Functional score improvement was less in MS cohort than patients without MS.

CONCLUSION

Patients with MS are at increased risk of complications, particularly instability and periprosthetic joint infection. Despite this increased risk of complications, patients with MS can demonstrate improved functional outcomes, but not as much as patients without MS. Patients with MS should be counseled appropriately before undergoing TJA.

Steering through complexity: management approaches in multiple sclerosis

PURPOSE OF REVIEW

This review evaluates current and late-phase developing therapies for multiple sclerosis in regard to therapeutic efficacy and patient safety in light of recent published and presented observations from 2015.

RECENT FINDINGS

We describe data that provide supportive evidence for comparisons of therapeutic efficacy of multiple sclerosis therapies and review available data on rare but serious adverse events associated with these therapies.

SUMMARY

Serious adverse events that are sometimes rare and unpredictable may substantially alter current approaches to multiple sclerosis treatments. New therapies that have proved superior effects compared with older therapies will also impact multiple sclerosis treatment practice in the near future.

Drugs approved for the treatment of multiple sclerosis: review of their safety profile

INTRODUCTION

Multiple sclerosis (MS) is a chronic immune-mediated inflammatory disorder of the brain and spinal cord characterized by inflammation, demyelination, and axonal degeneration. Area covered: Even though the pharmacological armamentarium for MS treatment is considerably improved in the last 20 years, safety data especially for the second-line and innovative treatments are lacking. In order to analyze the safety profile of drugs used for the treatment of MS, a literature review of pre-marketing, post-marketing studies and case reports was performed. Expert opinion: Nowadays, the numerous drugs approved in the last years for the treatment of MS allow a better control of the disease and a better patient compliance. The main advantages of the new disease-modifying agents for MS (DMTs), in fact, derive from the new oral administration and the prolonged half-life with consequent improvement in compliance compared to first-line therapy which required subcutaneous administrations. However, DMTs can cause serious, sometimes life-threatening or fatal, drug adverse reactions. Due to the lack of safety data and given the recent marketing approval of the last DMTs for MS, observational studies and post-marketing surveillance activities will be necessary in order to improve the knowledge about the safety profile of these drugs and the improvement of their use in clinical practice.

Anti-JCV serology during natalizumab treatment: Review and meta-analysis of 17 independent patient cohorts analyzing anti-John Cunningham polyoma virus sero-conversion rates under natalizumab treatment and differences between technical and biological sero-converters

BACKGROUND

Anti-John Cunningham virus (JCV) serology has been studied with varying results concerning longitudinal changes.

OBJECTIVES AND METHODS

Results from 17 published natalizumab-treated multiple sclerosis (MS) patient cohorts were analyzed with common parameters and subsequently verified in two large independent cohorts with 722 and 499 patients from Germany and the United States.

RESULTS

Published studies and the verification showed (1) a mean of 10.80% sero-negative patients presented with sero-status change to positivity per year; (2) patients, who sero-convert to index values <0.9, convert from near the threshold and have a high probability of reverting with time; (3) patients, who convert to index values >0.9, start with low index values; (4) while JCV sero-positive patients with low index values sometimes revert to sero-negativity, patients with high index values almost never revert; and (5) the conversion rate of natalizumab-treated patients is three to four times higher than the biological conversion by age.

CONCLUSION

JCV sero-conversion was comparable using standardized parameters and indicates influence of natalizumab on JCV immune control. Converters to low index values are probably consistently infected with JCV with varying low levels of activity, in line with their low risk to develop progressive multifocal leukoencephalopathy (PML). Patients with high index values rarely revert back to sero-negativity.

Development and Validation of an Enzyme-Linked Immunosorbent Assay for the Detection of Binding Anti-Drug Antibodies against Interferon Beta

Objective

To develop and validate a method for the detection of binding anti-drug antibodies (ADAs) against interferon beta (IFN-β) in human serum as part of a European initiative (ABIRISK) aimed at the prediction and analysis of clinical relevance of anti-biopharmaceutical immunization to minimize the risk.

Method

A two-tiered bridging enzyme-linked immunosorbent assay (ELISA) format was selected and validated according to current recommendations. Screening assay: ADA in serum samples form complexes with immobilized IFN-β and biotinylated IFN-β, which are then detected using HRP labeled Streptavidin and TMB substrate. Confirmation assay: Screen “putative positive” samples are tested in the presence of excess drug (preincubation of sera with 0.3 µg/mL of soluble IFN-β) and percentage of inhibition is calculated.

Results

The assay is precise, and the sensitivity of the assay was confirmed to be 26 ng/mL using commercially available polyclonal rabbit antihuman IFN-β in human sera as the positive control.

Conclusion

An ultrasensitive ELISA for IFN-β-binding ADA testing has been validated. This will form the basis to assess anti-biopharmaceutical immunization toward IFN-β with regards to its clinical relevance and may allow for the development of predictive tools, key aims within the ABIRISK consortium.

Expanding Role of T Cells in Human Autoimmune Diseases of the Central Nervous System

It is being increasingly recognized that a dysregulation of the immune system plays a vital role in neurological disorders and shapes the treatment of the disease. Aberrant T cell responses, in particular, are key in driving autoimmunity and have been traditionally associated with multiple sclerosis. Yet, it is evident that there are other neurological diseases in which autoreactive T cells have an active role in pathogenesis. In this review, we report on the recent progress in profiling and assessing the functionality of autoreactive T cells in central nervous system (CNS) autoimmune disorders that are currently postulated to be primarily T cell driven. We also explore the autoreactive T cell response in a recently emerging group of syndromes characterized by autoantibodies against neuronal cell-surface proteins. Common methodology implemented in T cell biology is further considered as it is an important determinant in their detection and characterization. An improved understanding of the contribution of autoreactive T cells expands our knowledge of the autoimmune response in CNS disorders and can offer novel methods of therapeutic intervention.

Is the risk of progressive multifocal leukoencephalopathy the real reason for natalizumab discontinuation in patients with multiple sclerosis?

Background

Progressive multifocal leukoencephalopathy (PML) is one of the major risks of natalizumab therapy. Despite introduction of the currently employed PML risk stratification algorithm, the incidence of natalizumab-associated PML cases is not decreasing.

Objectives

We addressed the following questions: How do natalizumab-treated multiple sclerosis patients and their treating physicians assess and deal with PML risk? Is PML risk the real reason for natalizumab discontinuation?

Methods

699 natalizumab-treated multiple sclerosis patients and 99 physicians were included in this prospective observational study. Questionnaires were completed at 5 different time points. Patients were stratified into 5 subgroups according to the presence of PML risk factors (prior immunosuppression, anti-JCV antibody status, treatment duration). Patients with prior immunosuppression (n = 30, treated by n = 7 physicians) were excluded from analyses, because patient numbers were too small. Patients’ anti-JCV antibody index was not considered because data recruitment ended in 2014. Using Bayesian network and regression analysis, we examined the relationship between different patient- and physician-related factors and patients’ discontinuation of natalizumab.

Results

Patients of all subgroups and physicians assessed the PML risk as low. Overall patient adherence to natalizumab was high (87%). Only 13% of patients discontinued therapy. Natalizumab treatment cessation was associated with different patient- and physician-related factors (physicians’ assessment of general PML risk, number of treated patients per year, natalizumab treatment duration, relapses during the course of study) upon which only physicians’ judgment on treatment continuation, patients’ perception of personal PML risk, and JCV seroconversion showed significant relationships.

Conclusion

According to the currently employed risk stratification algorithm, the objective PML risk probably doesn’t play a dominant role in a patients’ decision to continue or stop natalizumab treatment. The decision-making process is rather guided by subjective views and experiences of patients and treating neurologists. Treating physicians should consider this discrepancy in their advice to improve the risk-benefit-ratio for the individual patient.

Severe Cytomegalovirus Gastritis During Natalizumab-Mediated Immunosuppression

We report a 35-year-old female receiving natalizumab as monotherapy for multiple sclerosis who subsequently developed severe cytomegalovirus gastritis. As cytomegalovirus gastritis has not been previously described during natalizumab treatment, we discuss the biological plausibility of this potential association and avenues for further study.

Interdisciplinary Risk Management in the Treatment of Multiple Sclerosis

BACKGROUND

Multiple sclerosis (MS) is the most common autoimmune disease of the central nervous system. There are at least 150 000 persons with MS in Germany. Recent years have seen the approval of new drugs against.

METHODS

This article is based on pertinent literature retrieved by a selective search in PubMed as well as on documentation of relevant risks and adverse effects in "red hand letters" (information bulletins from pharmaceutical companies to physicians about adverse drug effects) and elsewhere, along with data provided by the German Multiple Sclerosis Competence Network.

RESULTS

In recent years, there have been major advances enabling better, more individualized treatment of patients with MS. Physicians must, however, give due consideration to potentially severe or even life-threatening adverse drug effects. These can include, for example, transaminase elevation (hepatotoxicity), cardio- and nephrotoxicity, or lympho- and leukopenia with a variable risk of infection. Among patients taking natalizumab, the cumulative risk of developing progressive multifocal leukencephalopathy (PML) may be 1:100 or higher, depending on the individual risk profile. Rare cases of PML have also been seen under treatment with fingolimod and dimethyl fumarate. Moreover, any type of immunosuppressive treatment can, at least theoretically, increase the risk of malignant disease. Secondary autoimmune diseases can arise as well: approximately 35% of patients treated with alemtuzumab develop autoimmune thyroid disease within two years, and 2% of patients who take daclizumab have severe autoimmune dermatological side effects. Teriflunomide, fingolimod, natalizumab, mitoxantrone, interferon β1-a/b, and daclizumab can all damage the liver. There are also psychiatric, reproductive, and vaccineassociated risks and side effects that must be considered.

CONCLUSION

Newer drugs for MS have enabled more effective treatment, but are also associated with a higher risk of side effects. Interdisciplinary risk management is needed.

Injectable Disease Modifying Agents in Multiple Sclerosis: Pattern of Medication Use and Clinical Effectiveness

The objective of this study was to assess long-term use, adherence and efficacy of injectable disease modifying agents (DMAs). Multiple Sclerosis (MS) patients diagnosed during 2002-2010 with early treatment start and at least one year in first choice medication were included in a large university district in Finland. Annualized relapse rates (ARR) during each treatment period were studied, and number of switches by medication evaluated. Use of health care facilities during 2002-2010 was assessed. In the study were included 113 MS patients; 15 (13%) switched medication. The mean duration of treatment period (128) was 3.8 years. In 77% (98/128) the treatment continued with the first DMA for (mean) 3.8 years, in 19% (25/128) with the second for 3.5 years and in 4% (5/128) with the third for 4.8 years. Mean ARR was 0.26, with 54% (69/128) of the periods relapse free. Mean ARR during the treatment periods with product switch was 0.41 before, and 0.28 after the switch, showing a trend towards better efficacy with the second DMA. The usage of health care resources remained within the guidelines. Long-term adherence to first choice DMA was observed, and a switch of product within the DMAs showed continuous adherence and efficacy. The efforts to seek a clinically effective and well tolerated agent within the first-line DMAs is warranted, leading to continued adherence and increased clinical effectiveness.

Re-evaluating the incidence of natalizumab-associated progressive multifocal leukoencephalopathy

OBJECTIVE

To estimate the prospective risk of developing PML during therapy with natalizumab in JCV-seropositive patients.

METHODS

We analyzed postmarketing data about the incidence of PML on natalizumab, and quantified the risk by either applying the Kaplan-Meier estimator or, where this was not possible due to the unavailability of the respective raw data, using formulae yielding very similar figures.

RESULTS

In JCV-seropositive patients with prior immunosuppressant (IS) use, the incidence of PML during months 25-48 of natalizumab therapy is about 19.5 per thousand. Without prior IS use, the incidence during months 25-48 is approximately 7.4 per thousand, and during months 49-72, it is approximately 10.8 per thousand. If one additionally assumes that the JCV index is in the range 0.9-1.5, then the incidence during months 49-72 is around 6.2 per thousand in comparison to 17.0 per thousand when the JCV index exceeds 1.5.

CONCLUSIONS

Biogen's statistics concerning the risk of PML on natalizumab, while in principle helpful, underestimate the true incidence systematically and significantly; realistic estimates of the longterm risk of PML are nearly double those previously published, with some patient groups carrying a risk that is almost nine times higher. Fortunately, a refined risk-stratification algorithm with the incorporation of such markers as L-selectin and CSF lipid-specific IgM bands has the potential to make natalizumab a considerably safer drug.

Immune suppression of JC virus gene expression is mediated by SRSF1

Progressive multifocal leukoemcephalopathy (PML) is a fatal demyelinating disease caused by the human neurotropic JC virus (JCV). JCV infects the majority of the human population during childhood and establishes a latent/persistent life-long infection. The virus reactivates under immunosuppressive conditions by unknown mechanisms, resulting in productive infection of oligodendrocytes in the central nervous system (CNS). Given the fact that the natural occurrence of PML is strongly associated with immunosuppression, the functional and molecular interaction between glial cells and neuroimmune signaling mediated by soluble immune mediators is likely to play a major role in reactivation of JCV and the progression of the lytic viral life cycle leading to the development of PML. In order to explore the effect of soluble immune mediators secreted by peripheral blood mononuclear cells (PBMCs) on JCV transcription, primary human fetal glial (PHFG) cells were treated with conditioned media from PBMCs. We observed a strong suppression of JCV early as well as late gene transcription in cells treated with conditioned media from induced PBMCs. Using a variety of virological and molecular biological approaches, we demonstrate that immune mediators secreted by PBMCs induce the expression of SRSF1, a strong inhibitor of JCV gene expression, and inhibit the replication of JCV. Our results show that downregulation of SRSF1 in glial cells overcomes the suppression of JCV gene expression and its replication mediated by soluble immune mediators. These findings suggest the presence of a novel immune signaling pathway between glial cells and PBMCs that may control JCV gene expression during the course of viral reactivation.

Disease-modifying therapies and infectious risks in multiple sclerosis

Immunomodulatory and immunosuppressive treatments for multiple sclerosis (MS) are associated with an increased risk of infection, which makes treatment of this condition challenging in daily clinical practice. Use of the expanding range of available drugs to treat MS requires extensive knowledge of treatment-associated infections, risk-minimizing strategies and approaches to monitoring and treatment of such adverse events. An interdisciplinary approach to evaluate the infectious events associated with available MS treatments has become increasingly relevant. In addition, individual stratification of treatment-related infectious risks is necessary when choosing therapies for patients with MS, as well as during and after therapy. Determination of the individual risk of infection following serial administration of different immunotherapies is also crucial. Here, we review the modes of action of the available MS drugs, and relate this information to the current knowledge of drug-specific infectious risks and risk-minimizing strategies.

Advances in and Algorithms for the Treatment of Relapsing-Remitting Multiple Sclerosis

Treatment options in relapsing-remitting multiple sclerosis have increased considerably in recent years; currently, a dozen different preparations of disease-modifying therapies are available and some more are expected to be marketed soon. For the treating neurologist this broad therapeutic repertoire not only greatly improves individualized management of the disease, but also makes choices more complex and difficult. A number of factors must be considered, including disease activity and severity, safety profile, and patient preference. We here discuss the currently existing options and suggest treatment algorithms for managing relapsing-remitting multiple sclerosis.