Increased B cell and cytotoxic NK cell proportions and increased T cell responsiveness in blood of natalizumab-treated multiple sclerosis patients

Identification of alemtuzumab-suitable multiple sclerosis patients in Slovakia and sequencing of post-alemtuzumab immunomodulatory treatment

Background

Alemtuzumab (ALEM) is a humanised monoclonal antibody that depletes circulating lymphocytes by selectively targeting CD52, which is expressed in high levels on T- and B-lymphocytes. This depletion is followed by lymphocyte repopulation and a cytokine expression shift towards a lesser inflammatory profile, both of which may contribute to prolonged efficacy. National recommendations for enrolling and treating multiple sclerosis (MS) patients with ALEM have been established. However, there are no recommendations in place for the treatment of MS reactivation after the ALEM treatment.

Objectives

To evaluate the effectiveness and safety of the use of ALEM and to analyse subsequent disease-modifying treatments (DMTs). A multidimensional prediction model was developed to make a patient-specific prognosis regarding the response to ALEM.

Design

A multicentre, prospective, non-controlled, non-interventional, observational cohort study.

Methods

Relapsing multiple sclerosis patients (RMSp) who received ⩾1 dose of ALEM were enrolled. In each treatment year, the following baseline and prospective data were collected: age, MS history, number, type and duration of previous disease-modifying treatment (PDMT), relapse rate (REL), expanded disability status scale (EDSS), magnetic resonance imaging and serious adverse events (AE). In cases of reactivation of MS, all data about the subsequent DMT were collected.

Results

A total of 142 RMSp from 10 MS Slovak Centres fulfilled the inclusion criteria. The average age was 35 years (standard error 8.56). The overall average EDSS was 3.87 (1.46) when ALEM was started. The average duration of PDMT was 6.0 (4.04) years, and the median number of PDMTs was 3 (0-5), while the patients were mostly treated with 2 or 3 DMTs (>65.00%). Post-ALEM treatment was needed in 39 cases (27.46%). The most frequent post-ALEM treatment indicated was ocrelizumab, followed by natalizumab (NAT), siponimod and cladribine. The ocrelizumab and NAT treatment bring little benefit to patients. Siponimod showed less EDSS increase in contrast to ocrelizumab and NAT. Another repopulation therapy, cladribine, may also be an effective option. Statistically significant predictors for the expected EDSS are age (p-value <0.0001), number of ALEM cycles (0.0066), high number of PDMT (0.0459) and the occurrence of relapses (<0.0001). There was no statistically significant effect on the patient's gender (0.6038), duration of disease-modifying treatment before alemtuzumab (0.4466), or the occurrence of AE (0.6668).

Conclusion

The study confirms the positive effect of ALEM on clinical and radiological outcomes. We need more data from long-term sequencing studies.

An overview on disease modifying and symptomatic drug treatments for multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is an inflammatory and degenerative autoimmune condition, resulting frequently in a disabling condition. Significant improvements of long-term prognosis have been recently achieved with an early and more aggressive use of disease modifying therapies (DMTs). Addressing the complexity of managing its progressive forms remains a significant challenge.

AREAS COVERED

This review provides an update on DMTs for relapsing-remitting MS (RRMS) and progressive MS and their efficacy, safety, and mechanism of action, emphasizing the critical role of biomarkers in optimizing treatment decisions. Moreover, some key information on drugs used to manage symptoms such as pain, fatigue, spasticity and urinary problems will be provided. The literature search was conducted using PubMed, Embase, and Cochrane Library databases covering the period from January 2000 to January 2024.

EXPERT OPINION

Major advances have been achieved in the treatment of RRMS. Treatment should start immediately as soon as the neurologist is confident with the diagnosis and its choice should be based on the prognostic profile and on the patient's propensity to accept drug-related risks. The therapeutic landscape for progressive MS is quite disappointing and necessitates further innovation. Personalized medicine, leveraging biomarker insights, holds promise for refining treatment efficacy and patient outcomes.

The role of CD56bright NK cells in neurodegenerative disorders

Emerging evidence suggests a potential role for natural killer (NK) cells in neurodegenerative diseases, such as multiple sclerosis, Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. However, the precise function of NK cells in these diseases remains ambiguous. The existence of two NK cell subsets, CD56bright and CD56dim NK cells, complicates the understanding of the contribution of NK cells in neurodegeneration as their functions within the context of neurodegenerative diseases may differ significantly. CD56bright NK cells are potent cytokine secretors and are considered more immunoregulatory and less terminally differentiated than their mostly cytotoxic CD56dim counterparts. Hence, this review focusses on NK cells, specifically on CD56bright NK cells, and their role in neurodegenerative diseases. Moreover, it explores the mechanisms underlying their ability to enter the central nervous system. By consolidating current knowledge, we aim to provide a comprehensive overview on the role of CD56bright NK cells in neurodegenerative diseases. Elucidating their impact on neurodegeneration may have implications for future therapeutic interventions, potentially ameliorating disease pathogenesis.

T Lymphocyte Serotonin 5-HT7 Receptor Is Dysregulated in Natalizumab-Treated Multiple Sclerosis Patients

Serotonin (5-HT) is known as a potent immune cell modulator in autoimmune diseases and should be protective in the pathogenesis of multiple sclerosis (MS). Nevertheless, there is limited knowledge about receptors involved in 5-HT effects as well as induced mechanisms. Among 5-HT receptors, the 5-HT₇ receptor is able to activate naïve T cells and influence the inflammatory response; however, its involvement in the disease has never been studied so far. In this study, we collected blood sample from three groups: acute relapsing MS patients (ARMS), natalizumab-treated MS patients (NTZ), and control subjects. We investigated the 5-HT₇ expression on circulating lymphocytes and evaluated the effects of its activation on cytokine production with peripheral blood mononuclear cell (PBMC) cultures. We found a significant increase in the 5-HT₇ surface expression on T lymphocytes and on the different CD4⁺ T cell subsets exclusively in NTZ-treated patients. We also showed that the selective agonist 5-carboxamidotryptamine (5-CT)-induced 5-HT₇R activation significantly promotes the production of IL-10, a potent immunosuppressive cytokine in PBMCs. This study provides for the first time a dysregulation of 5-HT₇ expression in NTZ-MS patients and its ability to promote IL-10 release, suggesting its protective role. These findings strengthen the evidence that 5-HT₇ may play a role in the immuno-protective mechanisms of NTZ in MS disease and could be considered as an interesting therapeutic target in MS.

RNA-sequencing and mass-spectrometry proteomic time-series analysis of T-cell differentiation identified multiple splice variants models that predicted validated protein biomarkers in inflammatory diseases

Profiling of mRNA expression is an important method to identify biomarkers but complicated by limited correlations between mRNA expression and protein abundance. We hypothesised that these correlations could be improved by mathematical models based on measuring splice variants and time delay in protein translation. We characterised time-series of primary human naïve CD4+ T cells during early T helper type 1 differentiation with RNA-sequencing and mass-spectrometry proteomics. We performed computational time-series analysis in this system and in two other key human and murine immune cell types. Linear mathematical mixed time delayed splice variant models were used to predict protein abundances, and the models were validated using out-of-sample predictions. Lastly, we re-analysed RNA-seq datasets to evaluate biomarker discovery in five T-cell associated diseases, further validating the findings for multiple sclerosis (MS) and asthma. The new models significantly out-performing models not including the usage of multiple splice variants and time delays, as shown in cross-validation tests. Our mathematical models provided more differentially expressed proteins between patients and controls in all five diseases. Moreover, analysis of these proteins in asthma and MS supported their relevance. One marker, sCD27, was validated in MS using two independent cohorts for evaluating response to treatment and disease prognosis. In summary, our splice variant and time delay models substantially improved the prediction of protein abundance from mRNA expression in three different immune cell types. The models provided valuable biomarker candidates, which were further validated in MS and asthma.

Natural killer cell homing and trafficking in tissues and tumors: from biology to application

Natural killer (NK) cells, a subgroup of innate lymphoid cells, act as the first line of defense against cancer. Although some evidence shows that NK cells can develop in secondary lymphoid tissues, NK cells develop mainly in the bone marrow (BM) and egress into the blood circulation when they mature. They then migrate to and settle down in peripheral tissues, though some special subsets home back into the BM or secondary lymphoid organs. Owing to its success in allogeneic adoptive transfer for cancer treatment and its "off-the-shelf" potential, NK cell-based immunotherapy is attracting increasing attention in the treatment of various cancers. However, insufficient infiltration of adoptively transferred NK cells limits clinical utility, especially for solid tumors. Expansion of NK cells or engineered chimeric antigen receptor (CAR) NK cells ex vivo prior to adoptive transfer by using various cytokines alters the profiles of chemokine receptors, which affects the infiltration of transferred NK cells into tumor tissue. Several factors control NK cell trafficking and homing, including cell-intrinsic factors (e.g., transcriptional factors), cell-extrinsic factors (e.g., integrins, selectins, chemokines and their corresponding receptors, signals induced by cytokines, sphingosine-1-phosphate (S1P), etc.), and the cellular microenvironment. Here, we summarize the profiles and mechanisms of NK cell homing and trafficking at steady state and during tumor development, aiming to improve NK cell-based cancer immunotherapy.

SARS-CoV-2 Specific Antibody Response and T Cell-Immunity in Immunocompromised Patients up to Six Months Post COVID: A Pilot Study

COVID-19 generates SARS-CoV-2-specific antibodies in immunocompetent individuals. However, in immunocompromised patients, the humoral immunity following infection may be impaired or absent. Recently, the assessment of cellular immunity to SARS-CoV-2, both following natural infection and vaccination, has contributed new knowledge regarding patients with low or no antibody responses. As part of a prospective cohort study which included hospitalized patients with COVID-19, we identified immunocompromised patients and compared them with age- and sex-matched immunocompetent patients regarding co-morbidities, biomarkers of COVID-19 and baseline viral load by real-time PCR in nasopharyngeal swabs. Spike and nucleocapsid antibody responses were analyzed at inclusion and after two weeks, six weeks and six months. Plasma immunoglobulin G (IgG) levels were quantified, lymphocyte phenotyping was performed, and SARS-CoV-2 specific CD4 and CD8 T cell responses after in vitro antigen stimulation were assessed at six months post infection. All patients showed IgG levels above or within reference limits. At six months, all patients had detectable SARS-CoV-2 anti-spike antibody levels. SARS-CoV-2 specific T cell responses were detected in 12 of 12 immunocompetent patients and in four of six immunocompromised patients. The magnitude of long-lived SARS-CoV-2 specific T cell responses were significantly correlated with the number of CD4 T cells and NK cells. Determining the durability of the humoral and cellular immune response against SARS-CoV-2 in immunocompromised individuals could be of importance by providing insights into the risk of re-infection and the need for vaccine boosters.

The CD8 T Cell-Epstein-Barr Virus-B Cell Trialogue: A Central Issue in Multiple Sclerosis Pathogenesis

The cause and the pathogenic mechanisms leading to multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system (CNS), are still under scrutiny. During the last decade, awareness has increased that multiple genetic and environmental factors act in concert to modulate MS risk. Likewise, the landscape of cells of the adaptive immune system that are believed to play a role in MS immunopathogenesis has expanded by including not only CD4 T helper cells but also cytotoxic CD8 T cells and B cells. Once the key cellular players are identified, the main challenge is to define precisely how they act and interact to induce neuroinflammation and the neurodegenerative cascade in MS. CD8 T cells have been implicated in MS pathogenesis since the 80's when it was shown that CD8 T cells predominate in MS brain lesions. Interest in the role of CD8 T cells in MS was revived in 2000 and the years thereafter by studies showing that CNS-recruited CD8 T cells are clonally expanded and have a memory effector phenotype indicating in situ antigen-driven reactivation. The association of certain MHC class I alleles with MS genetic risk implicates CD8 T cells in disease pathogenesis. Moreover, experimental studies have highlighted the detrimental effects of CD8 T cell activation on neural cells. While the antigens responsible for T cell recruitment and activation in the CNS remain elusive, the high efficacy of B-cell depleting drugs in MS and a growing number of studies implicate B cells and Epstein-Barr virus (EBV), a B-lymphotropic herpesvirus that is strongly associated with MS, in the activation of pathogenic T cells. This article reviews the results of human studies that have contributed to elucidate the role of CD8 T cells in MS immunopathogenesis, and discusses them in light of current understanding of autoreactivity, B-cell and EBV involvement in MS, and mechanism of action of different MS treatments. Based on the available evidences, an immunopathological model of MS is proposed that entails a persistent EBV infection of CNS-infiltrating B cells as the target of a dysregulated cytotoxic CD8 T cell response causing CNS tissue damage.

Herpesvirus Antibodies, Vitamin D and Short-Chain Fatty Acids: Their Correlation with Cell Subsets in Multiple Sclerosis Patients and Healthy Controls

Although the etiology of multiple sclerosis (MS) is still unknown, it is commonly accepted that environmental factors could contribute to the disease. The objective of this study was to analyze the humoral response to Epstein-Barr virus, human herpesvirus 6A/B and cytomegalovirus, and the levels of 25-hydroxyvitamin D (25(OH)D) and the three main short-chain fatty acids (SCFA), propionate (PA), butyrate (BA) and acetate (AA), in MS patients and healthy controls (HC) to understand how they could contribute to the pathogenesis of the disease. With this purpose, we analyzed the correlations among them and with different clinical variables and a wide panel of cell subsets. We found statistically significant differences for most of the environmental factors analyzed when we compared MS patients and HC, supporting their possible involvement in the disease. The strongest correlations with the clinical variables and the cell subsets analyzed were found for 25(OH)D and SCFAs levels. A correlation was also found between 25(OH)D and PA/AA ratio, and the interaction between these factors negatively correlated with interleukin 17 (IL-17)-producing CD4+ and CD8+ T cells in untreated MS patients. Therapies that simultaneously increase vitamin D levels and modify the proportion of SCFA could be evaluated in the future.

Natalizumab in Multiple Sclerosis Treatment: From Biological Effects to Immune Monitoring

Multiple sclerosis is a chronic demyelinating disease of the central nervous system (CNS) with an autoimmune component. Among the recent disease-modifying treatments available, Natalizumab, a monoclonal antibody directed against the alpha chain of the VLA-4 integrin (CD49d), is a potent inhibitor of cell migration toward the tissues including CNS. It potently reduces relapses and active brain lesions in the relapsing remitting form of the disease. However, it has also been associated with a severe infectious complication, the progressive multifocal leukoencephalitis (PML). Using the standard protocol with an injection every 4 weeks it has been shown by a close monitoring of the drug that trough levels soon reach a plateau with an almost saturation of the target cell receptor as well as a down modulation of this receptor. In this review, mechanisms of action involved in therapeutic efficacy as well as in PML risk will be discussed. Furthermore the interest of a biological monitoring that may be helpful to rapidly adapt treatment is presented. Indeed, development of anti-NAT antibodies, although sometimes unapparent, can be detected indirectly by normalization of CD49d expression on circulating mononuclear cells and might require to switch to another drug. On the other hand a stable modulation of CD49d expression might be useful to follow the circulating NAT levels and apply an extended interval dose scheme that could contribute to limiting the risk of PML.

The role of B cells in the immunopathogenesis of multiple sclerosis

There is ongoing debate on how B cells contribute to the pathogenesis of multiple sclerosis (MS). The success of B-cell targeting therapies in MS highlighted the role of B cells, particularly the antibody-independent functions of these cells such as antigen presentation to T cells and modulation of the function of T cells and myeloid cells by secreting pathogenic and/or protective cytokines in the central nervous system. Here, we discuss the role of different antibody-dependent and antibody-independent functions of B cells in MS disease activity and progression proposing new therapeutic strategies for the optimization of B-cell targeting treatments.

Treatment effects of fingolimod in multiple sclerosis: Selective changes in peripheral blood lymphocyte subsets

BACKGROUND

Treatment with fingolimod reduces inflammation in multiple sclerosis (MS) by inhibiting lymphocyte egress from lymph nodes. We aimed to map, in detail, the alterations in peripheral blood lymphocyte subpopulations in relation to clinical outcome in MS patients treated with fingolimod.

METHODS

Paired blood samples from relapsing-remitting MS patients (n = 19) were collected before and after one year of treatment with fingolimod (0.5 mg/day). Absolute counts and relative proportions of a broad set of T- B- and NK-cell subsets were analyzed by flow cytometry. Blood samples from 18 healthy controls were used for baseline comparisons.

RESULTS

Treatment with fingolimod markedly decreased the absolute numbers of all major lymphocyte subsets, except for NK cells. The reduction was most pronounced within the T helper (Th) and B cell populations (p<0.001). By phenotyping differentiation status of T cells, dramatic reductions within the naïve and central memory (CM) cell populations were found (p<0.001), while a less pronounced reduction was observed among effector memory (EM) cells (p<0.001). The numbers of regulatory T cells (Tregs) were also decreased (p<0.001), but to a lesser extent than other T cell populations, resulting in a relative preservation of Tregs with a memory phenotype (p = 0.002).

CONCLUSIONS

Our results confirm that fingolimod therapy markedly reduces lymphocyte counts in peripheral blood of MS patients. Subgroup analysis of T cells showed that naïve and CM Th cells were the most profoundly affected and that memory Tregs were relatively preserved.

Hepatic Natural Killer Cells: Organ-Specific Sentinels of Liver Immune Homeostasis and Physiopathology

The liver is considered a preferential tissue for NK cells residency. In humans, almost 50% of all intrahepatic lymphocytes are NK cells that are strongly imprinted in a liver-specific manner and show a broad spectrum of cellular heterogeneity. Hepatic NK (he-NK) cells play key roles in tuning liver immune response in both physiological and pathological conditions. Therefore, there is a pressing need to comprehensively characterize human he-NK cells to better understand the related mechanisms regulating their effector-functions within the dynamic balance between immune-tolerance and immune-surveillance. This is of particular relevance in the liver that is the only solid organ whose parenchyma is constantly challenged on daily basis by millions of foreign antigens drained from the gut. Therefore, the present review summarizes our current knowledge on he-NK cells in the light of the latest discoveries in the field of NK cell biology and clinical relevance.

Real-World Lab Data in Natalizumab Treated Multiple Sclerosis Patients Up to 6 Years Long-Term Follow Up

Natalizumab inhibits the transmigration of immune cells across the blood-brain barrier thus inhibiting inflammation in the central nervous system. Generally, this blockade at the blood-brain barrier has significant influence on the circulating lymphocytes. Up to date, only short-term data on peripheral blood parameters are available which are mostly from controlled clinical trials and not from real-world experience. Real-world lab data of 120 patients diagnosed with highly active disease course of relapsing-remitting multiple sclerosis (RRMS) were analyzed during natalizumab treatment. Patient sampling was performed by consecutive recruitment in the Multiple Sclerosis Center Dresden. Lab testing was performed before and at every third infusion up to 72 months follow-up. After first natalizumab infusion, absolute numbers of all major lymphocyte populations including CD4+ T-cells, CD8+ T-cells, CD19+ B-cells, and NK-cells significantly increased and remained stable during the whole observation period of 72 months. Upon lymphocyte subsets, CD19+ B-cells presented a disproportionate increase up to levels higher than normal level in most of the treated patients. Neutralizing antibodies to natalizumab abrogated the described changes. Intra-individual variation of lymphocytes and its subsets remained in a narrow range for the whole treatment period. CD4/CD8 ratio did not change compared to baseline measurement up to 6 years of natalizumab treatment. Monocytes, eosinophils, and basophils, but not neutrophils persistently increased during natalizumab treatment. Hematological parameters including erythrocyte, platelet count, hemoglobin, and hematocrit remained unchanged compared to baseline. Interestingly, immature precursor cells including erythroblasts were detectable in 36,8% of the treated patients during natalizumab therapy, but not in the pretreatment period. Asymptomatic elevations of liver enzymes were rare, mostly only transient and lower than 3x upper normal limit. Kidney function parameters remained stable within physiological ranges in most patients. CRP levels >20 mg/dl were recognized only in 10 patients during natalizumab therapy and were mostly linked to respiratory tract infections. In our present analysis, we report persistent, but stable increases of peripheral immune cell subtypes in natalizumab treated patients. Additional serological analyses confirm excellent tolerability and safety even 6 years after natalizumab initiation in post-marketing experience.

Molecular Mechanisms Directing Migration and Retention of Natural Killer Cells in Human Tissues

A large body of data shows that Natural Killer (NK) cells are immune effectors exerting a potent cytolytic activity against tumors and virus infected cells. The discovery and characterization of several inhibitory and activating receptors unveiled most of the mechanisms allowing NK cells to spare healthy cells while selectively attacking abnormal tissues. Nevertheless, the mechanisms ruling NK cell subset recirculation among the different compartments of human body have only lately started to be investigated. This is particularly true for pathological settings such as tumors or infected tissues but also for para-physiological condition like pregnant human uterine mucosa. It is becoming evident that the microenvironment associated to a particular clinical condition can deeply influence the migratory capabilities of NK cells. In this review we describe the main mechanisms and stimuli known to regulate the expression of chemokine receptors and other molecules involved in NK cell homing to either normal or pathological/inflamed tissues, including tumors or organs such as lung and liver. We will also discuss the role played by the chemokine/chemokine receptor axes in the orchestration of physiological events such as NK cell differentiation, lymphoid organ retention/egress and recruitment to decidua during pregnancy.

Lymphocyte Disturbances in Primary Antiphospholipid Syndrome and Application to Venous Thromboembolism Follow-Up

Among patients with venous thromboembolism (VTE), the persistent detection of antiphospholipid (aPL) antibodies (Ab) represents an independent high risk factor for recurrence. However, oral anticoagulation vitamin K antagonist therapy, frequently used in these patients, is problematic in assessing and/or confirming a diagnosis of primary aPL syndrome (pAPS), suggesting use of alternative strategies. For this reason, and by analogy with other autoimmune diseases, a flow cytometer approach testing peripheral T cell subsets (CD3, CD4, and CD8), B cell subsets (B1, transitional, naive, and memory), and NK cells can be proposed. As an example and to validate the concept, pAPS patients selected from the monocentric VTE case-control EDITH's cohort were selected during their follow-up. As suspected and in contrast to non-APS VTE patients, other autoimmune diseases, and controls, pAPS VTE patients displayed specific lymphocyte disturbances. Quantitative and qualitative modifications were related to total CD4⁺ T cell reduction, a lower CD4/CD8 ratio, and disturbance in B cell homeostasis with increased proportions of B1 cells, transitional B cells (CD24⁺⁺CD38⁺⁺), and naive B cells (IgD⁺CD27^-), while memory B cells (IgD⁺CD27⁺ and IgD^-CD27⁺) were reduced. Interestingly, the absolute number of CD4⁺ T cells positively correlated with IgG anti-cardiolipin Ab levels. Altogether, disturbances of T and B cell homeostasis characterized pAPS VTE patients during their follow-up. This suggests a means of profiling that could be used in addition to existing criteria to characterize them.

Understanding Progressive Multifocal Leukoencephalopathy Risk in Multiple Sclerosis Patients Treated with Immunomodulatory Therapies: A Bird's Eye View

The increased use of newer potent immunomodulatory therapies for multiple sclerosis (MS), including natalizumab, fingolimod, and dimethyl fumarate, has expanded the patient population at risk for developing progressive multifocal leukoencephalopathy (PML). These MS therapies shift the profile of lymphocytes within the central nervous system (CNS) leading to increased anti-inflammatory subsets and decreased immunosurveillance. Similar to MS, PML is a demyelinating disease of the CNS, but it is caused by the JC virus. The manifestation of PML requires the presence of an active, genetically rearranged form of the JC virus within CNS glial cells, coupled with the loss of appropriate JC virus-specific immune responses. The reliability of metrics used to predict risk for PML could be improved if all three components, i.e., viral genetic strain, localization, and host immune function, were taken into account. Advances in our understanding of the critical lymphocyte subpopulation changes induced by these MS therapies and ability to detect viral mutation and reactivation will facilitate efforts to develop these metrics.

Dynamic Response Genes in CD4+ T Cells Reveal a Network of Interactive Proteins that Classifies Disease Activity in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the CNS and has a varying disease course as well as variable response to treatment. Biomarkers may therefore aid personalized treatment. We tested whether in vitro activation of MS patient-derived CD4+ T cells could reveal potential biomarkers. The dynamic gene expression response to activation was dysregulated in patient-derived CD4+ T cells. By integrating our findings with genome-wide association studies, we constructed a highly connected MS gene module, disclosing cell activation and chemotaxis as central components. Changes in several module genes were associated with differences in protein levels, which were measurable in cerebrospinal fluid and were used to classify patients from control individuals. In addition, these measurements could predict disease activity after 2 years and distinguish low and high responders to treatment in two additional, independent cohorts. While further validation is needed in larger cohorts prior to clinical implementation, we have uncovered a set of potentially promising biomarkers.

Deciphering the Role of B Cells in Multiple Sclerosis-Towards Specific Targeting of Pathogenic Function

B cells, plasma cells and antibodies may play a key role in the pathogenesis of multiple sclerosis (MS). This notion is supported by various immunological changes observed in MS patients, such as activation and pro-inflammatory differentiation of peripheral blood B cells, the persistence of clonally expanded plasma cells producing immunoglobulins in the cerebrospinal fluid, as well as the composition of inflammatory central nervous system lesions frequently containing co-localizing antibody depositions and activated complement. In recent years, the perception of a respective pathophysiological B cell involvement was vividly promoted by the empirical success of anti-CD20-mediated B cell depletion in clinical trials; based on these findings, the first monoclonal anti-CD20 antibody—ocrelizumab—is currently in the process of being approved for treatment of MS. In this review, we summarize the current knowledge on the role of B cells, plasma cells and antibodies in MS and elucidate how approved and future treatments, first and foremost anti-CD20 antibodies, therapeutically modify these B cell components. We will furthermore describe regulatory functions of B cells in MS and discuss how the evolving knowledge of these therapeutically desirable B cell properties can be harnessed to improve future safety and efficacy of B cell-directed therapy in MS.

Reversibility of the effects of natalizumab on peripheral immune cell dynamics in MS patients

OBJECTIVE

To characterize the reversibility of natalizumab-mediated changes in pharmacokinetics/pharmacodynamics in patients with multiple sclerosis (MS) following therapy interruption.

METHODS

Pharmacokinetic/pharmacodynamic data were collected in the Safety and Efficacy of Natalizumab in the Treatment of Multiple Sclerosis (AFFIRM) (every 12 weeks for 116 weeks) and Randomized Treatment Interruption of Natalizumab (RESTORE) (every 4 weeks for 28 weeks) studies. Serum natalizumab and soluble vascular cell adhesion molecule-1 (sVCAM-1) were measured using immunoassays. Lymphocyte subsets, α4-integrin expression/saturation, and vascular cell adhesion molecule-1 (VCAM-1) binding were assessed using flow cytometry.

RESULTS

Blood lymphocyte counts (cells/L) in natalizumab-treated patients increased from 2.1 × 10⁹ to 3.5 × 10⁹. Starting 8 weeks post last natalizumab dose, lymphocyte counts became significantly lower in patients interrupting treatment than in those continuing treatment (3.1 × 10⁹ vs 3.5 × 10⁹; p = 0.031), plateauing at prenatalizumab levels from week 16 onward. All measured cell subpopulation, α4-integrin expression/saturation, and sVCAM changes demonstrated similar reversibility. Lymphocyte counts remained within the normal range. Ex vivo VCAM-1 binding to lymphocytes increased until ≈16 weeks after the last natalizumab dose, then plateaued, suggesting reversibility of immune cell functionality. The temporal appearance of gadolinium-enhancing lesions was consistent with pharmacodynamic marker reversal.

CONCLUSIONS

Natalizumab's effects on peripheral immune cells and pharmacodynamic markers were reversible, with changes starting 8 weeks post last natalizumab dose; levels returned to those observed/expected in untreated patients ≈16 weeks post last dose. This reversibility differentiates natalizumab from MS treatments that require longer reconstitution times. Characterization of the time course of natalizumab's biological effects may help clinicians make treatment sequencing decisions.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that the pharmacodynamic markers of natalizumab are reversed ≈16 weeks after stopping natalizumab.

Quantification of γδ T cells and HLA-DR+ NK cells does not predict emergence of new contrast enhancing lesions in MS patients suspending natalizumab treatment

Background

Natalizumab (NTZ) is a drug that has been widely used in the treatment of multiple sclerosis (MS). NTZ is very effective in suppressing inflammation, but if treatment is suspended many patients will experience relapses.

Objective

To investigate if quantification of γδ T cells and HLA-DR⁺ NK cells could predict early disease reactivation after NTZ suspension.

Methods

Absolute counts of γδ T cells and HLA-DR⁺ NK cells in whole blood were determined with flow cytometry in fifteen patients treated with NTZ. NTZ treatment was then withdrawn and patients were followed with clinical visits and MR investigations.

Results

Patients with recurrent disease had higher absolute counts of γδ T cells 129 (±156) cells/μl in comparison to patients with stable disease 50.0 (±51.0) cells/μl but the difference was not statistically significant and largely driven by outliers. Patients with recurrent and stable disease had similar absolute counts of HLA-DR⁺ NK cells.

Conclusion

Quantification of γδ T cells and HLA-DR⁺ NK cells could not predict active disease after NTZ suspension.

In vitro VLA-4 blockade results in an impaired NK cell-mediated immune surveillance against melanoma

Natalizumab (NTZ) is a monoclonal antibody targeting the α4β1 integrin (CD49d/CD29), very late antigen-4 (VLA-4), which is approved for treatment of relapsing-remitting multiple sclerosis (RR-MS). A possible association between NTZ treatment and a higher risk of melanoma is under debate. Natural Killer (NK) cells, which express VLA-4, represent an innate barrier limiting spreading of melanoma under steady state conditions. Indeed, because of their expression of activating receptors, they are very efficient in recognizing and killing melanoma cells without the need of a previous priming. For this reason, we aimed at assessing whether NK-cell functions might be impaired by sustained exposure to NTZ. To investigate this possibility we isolated NK cells from healthy donors and tested their cytotoxic and migratory functions against primary melanoma cells derived from subcutaneous and lymph node metastases. Flow cytometry analysis demonstrated expression of CD49d on both freshly isolated NK cells and activated NK cells. Moreover, VLA-4 and its receptor, vascular cell adhesion protein-1 (VCAM-1) were similarly expressed on freshly isolated NK cells. However, upon a short exposure to NTZ, expression of VLA-4 on NK cells decreased. Analysis of NK receptor expression upon exposure of NK cells from three healthy donors to NTZ indicated that DNAM-1 and NKp46 are apparently decreased, while NKG2A is increased. The degranulation of NK cells towards melanoma cells, which express both VLA-4 and VCAM-1, was not affected when NTZ was added to the co-culture or when both NK cells and melanoma cells were each pre-exposed to NTZ for over 12h. In contrast, degranulation was significantly inhibited after 48h of pre-incubation indicating that NTZ can influence NK-cell degranulation towards melanoma cells only after a prolonged exposure. Using a migration chamber assay, we observed that the migration of NK cells towards melanoma cells was dependent upon the concentration of melanoma cells in the lower chamber, and that it was significantly reduced in presence of NTZ. Our results show that upon exposure to NTZ both cytolytic activity and migration toward melanoma cells were affected, suggesting that binding of NTZ to NK cells affects pathways involved in these NK-cell functions. We analyzed the expression of CD49d on NK cells from MS patients treated with NTZ and observed that it decreases with time of treatment. These data suggest that blockade of VLA-4 on NK-cell surface alters some key functions involved in the immune surveillance toward melanoma by NK cells and may provide a mechanistic explanation for the reported occurrence of melanoma in MS patients treated with NTZ.

B Cell-Directed Therapeutics in Multiple Sclerosis: Rationale and Clinical Evidence

Over the last decade, evidence condensed that B cells, B cell-derived plasma cells and antibodies play a key role in the pathogenesis and progression of multiple sclerosis (MS). In many patients with MS, peripheral B cells show signs of chronic activation; within the cerebrospinal fluid clonally expanded plasma cells produce oligoclonal immunoglobulins, which remain a hallmark diagnostic finding. Confirming the clinical relevance of these immunological alterations, recent trials testing anti-CD20-mediated depletion of peripheral B cells showed an instantaneous halt in development of new central nervous system lesions and occurrence of relapses. Notwithstanding this enormous success, not all B cells or B cell subsets may contribute in a pathogenic manner, and may, in contrast, exert anti-inflammatory and, thus, therapeutically desirable properties in MS. Naïve B cells, in MS patients similar to healthy controls, are a relevant source of regulatory cytokines such as interleukin-10, which dampens the activity of other immune cells and promotes recovery from acute disease flares in experimental MS models. In this review, we describe in detail pathogenic but also regulatory properties of B and plasma cells in the context of MS and its animal model experimental autoimmune encephalomyelitis. In the second part, we review what impact current and future therapies may have on these B cell properties. Within this section, we focus on the highly encouraging data on anti-CD20 antibodies as future therapy for MS. Lastly, we discuss how B cell-directed therapy in MS could be possibly advanced even further in regard to efficacy and safety by integrating the emerging information on B cell regulation in MS into future therapeutic strategies.

CX3CR1-dependent recruitment of mature NK cells into the central nervous system contributes to control autoimmune neuroinflammation

Fractalkine receptor (CX3CR1)-deficient mice develop very severe experimental autoimmune encephalomyelitis (EAE), associated with impaired NK cell recruitment into the CNS. Yet, the precise implications of NK cells in autoimmune neuroinflammation remain elusive. Here, we investigated the pattern of NK cell mobilization and the contribution of CX3CR1 to NK cell dynamics in the EAE. We show that in both wild-type and CX3CR1-deficient EAE mice, NK cells are mobilized from the periphery and accumulate in the inflamed CNS. However, in CX3CR1-deficient mice, the infiltrated NK cells displayed an immature phenotype contrasting with the mature infiltrates in WT mice. This shift in the immature/mature CNS ratio contributes to EAE exacerbation in CX3CR1-deficient mice, since transfer of mature WT NK cells prior to immunization exerted a protective effect and normalized the CNS NK cell ratio. Moreover, mature CD11b(+) NK cells show higher degranulation in the presence of autoreactive 2D2 transgenic CD4(+) T cells and kill these autoreactive cells more efficiently than the immature CD11b(-) fraction. Together, these data suggest a protective role of mature NK cells in EAE, possibly through direct modulation of T cells inside the CNS, and demonstrate that mature and immature NK cells are recruited into the CNS by distinct chemotactic signals.

The low EOMES/TBX21 molecular phenotype in multiple sclerosis reflects CD56+ cell dysregulation and is affected by immunomodulatory therapies

Multiple Sclerosis (MS) is an autoimmune disease treated by therapies targeting peripheral blood cells. We previously identified that expression of two MS-risk genes, the transcription factors EOMES and TBX21 (ET), was low in blood from MS and stable over time. Here we replicated the low ET expression in a new MS cohort (p<0.0007 for EOMES, p<0.028 for TBX21) and demonstrate longitudinal stability (p<10(-4)) and high heritability (h(2)=0.48 for EOMES) for this molecular phenotype. Genes whose expression correlated with ET, especially those controlling cell migration, further defined the phenotype. CD56+ cells and other subsets expressed lower levels of Eomes or T-bet protein and/or were under-represented in MS. EOMES and TBX21 risk SNP genotypes, and serum EBNA-1 titres were not correlated with ET expression, but HLA-DRB1*1501 genotype was. ET expression was normalised to healthy control levels with natalizumab, and was highly variable for glatiramer acetate, fingolimod, interferon-beta, dimethyl fumarate.

Effect of natalizumab treatment on circulating plasmacytoid dendritic cells: a cross-sectional observational study in patients with multiple sclerosis

Objectives

Dendritic cells (DCs) serve a critical role both in promoting and inhibiting adaptive immunity. The goal of this study was to investigate the effect of natalizumab (NTZ) treatment on DC numbers, phenotype, and function in patients with multiple sclerosis (MS).

Methods

Frequency and phenotype of myeloid and plasmacytoid DCs (MDCs and PDCs, respectively) were analyzed in blood from two separate cohorts of untreated, interferon-treated, or NTZ-treated MS patients. In addition, PDCs were stimulated with CpG-containing oligonucleotides or co-cultured with homologous T cells in the presence or absence of NTZ in vitro to determine functional effects of NTZ treatment.

Results

We observed that NTZ treatment was associated with a 25–50% reduction in PDC frequency in peripheral blood as compared to untreated MS patients, while the frequency of MDCs was unchanged. PDCs in NTZ-treated patients displayed a mature, activated phenotype with increased expression of HLA-DR, TLR9, CCR7, IL-6 and IL-12. In contrast, in vitro treatment with NTZ did not increase markers of PDC activation or their ability to induce T cell differentiation.

Conclusion

Our study shows that NTZ treatment is associated with a reduced frequency of PDCs in the peripheral circulation, but that PDCs in NTZ-treated individuals display an activated phenotype. Taken together the data suggests that transmigration of activated PDCs is preferentially affected by blockade of integrin α4 leading to an increased frequency of activated PDCs in blood.

Long-term follow-up of peripheral lymphocyte subsets in a cohort of multiple sclerosis patients treated with natalizumab

Natalizumab, an anti-alpha4 integrin monoclonal antibody inhibiting the adhesion of lymphocytes to the endothelium, is a widely accepted drug treatment for relapsing-remitting multiple sclerosis (RRMS). A peripheral increase of T and B lymphocytes has already been observed as an early treatment effect. This retrospective observational study was aimed to evaluate the peripheral lymphocyte subsets during a long-term treatment follow-up. We included 23 RRMS patients treated with natalizumab for at least 24-48 months who had pretreatment lymphocyte evaluation. Baseline values of lymphocyte subsets and CD4/CD8 ratio did not differ significantly from the 23 matched healthy subjects. The periodic (every 3-6 months) assessment of immune cell subsets was performed by flow cytometry on peripheral blood collected before drug injection. Therapy with natalizumab was confirmed to be effective during the observational period. For all patients, the increase in lymphocytes during natalizumab therapy compared to baseline at every assessment was significantly higher compared to that of overall white blood cells (2·1- and 1·3-fold, respectively, P < 0·0001). Both T cell subsets were proportionally modified and the CD4/CD8 ratio did not change significantly, while B cells increased significantly compared to T and NK cells (3·2-, 1·88- and 1·92-fold, respectively, P < 0·0001). These changes remained constant throughout the 25-48-month period of therapy. In conclusion, effective natalizumab treatment of RRMS patients was associated with the persistence of its biological effects through a stable increase of peripheral lymphocytes, mainly B cells, and an unchanged proportion of T cell subsets in long-term follow-up.