Effects of natalizumab treatment on Foxp3+ T regulatory cells

Alterations of Thymus-Derived Tregs in Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Multiple sclerosis (MS) is considered a prototypic autoimmune disease of the CNS. It is the leading cause of chronic neurologic disability in young adults. Proinflammatory B cells and autoreactive T cells both play important roles in its pathogenesis. We aimed to study alterations of regulatory T cells (Tregs), which likely also contribute to the disease, but their involvement is less clear.

METHODS

By combining multiple experimental approaches, we examined the Treg compartments in 41 patients with relapsing-remitting MS and 17 healthy donors.

RESULTS

Patients with MS showed a reduced frequency of CD4+ T cells and Foxp3+ Tregs and age-dependent alterations of Treg subsets. Treg suppressive function was compromised in patients, who were treated with natalizumab, while it was unaffected in untreated and anti-CD20-treated patients. The changes in natalizumab-treated patients included increased proinflammatory cytokines and an altered transcriptome in thymus-derived (t)-Tregs, but not in peripheral (p)-Tregs.

DISCUSSION

Treg dysfunction in patients with MS might be related to an altered transcriptome of t-Tregs and a proinflammatory environment. Our findings contribute to a better understanding of Tregs and their subtypes in MS.

Multiple faces of multiple sclerosis in the era of highly efficient treatment modalities: Lymphopenia and switching treatment options challenges daily practice

The expanded treatment landscape in relapsing-remitting multiple sclerosis (MS) has resulted in highly effective treatment options and complexity in managing disease- or drug-related events during disease progression. Proper decision-making requires thorough knowledge of the immunobiology of MS itself and an understanding of the main principles behind the mechanisms that lead to secondary autoimmunity affecting organs other than the central nervous system as well as opportunistic infections. The immune system is highly adapted to both environmental and disease-modifying agents. Immune reconstitution following cell depletion or cell entrapment therapies eliminates pathogenic aspects of the disease but can also lead to distorted immune responses with harmful effects. Atypical relapses occur with second-line treatments or after their discontinuation and require appropriate clinical decisions. Lymphopenia is a result of the mechanism of action of many drugs used to treat MS. However, persistent lymphopenia and cell-specific lymphopenia could result in disease exacerbation, secondary autoimmunity, or the emergence of opportunistic infections. Clinicians treating patients with MS should be aware of the multiple faces of MS under novel, efficient treatment modalities and understand the intricate brain-immune cell interactions in the context of an altered immune system. MS relapses and disease progression still occur despite the current treatment modalities and are mediated either by failure to control effector mechanisms inherent to MS pathophysiology or by new drug-related mechanisms. The multiple faces of MS due to the highly adapted immune system of patients impose the need for appropriate switching therapies that safeguard disease remission and further clinical improvement.

Natalizumab Treatment of Relapsing Remitting Multiple Sclerosis Has No Long-Term Effects on the Proportion of Circulating Regulatory T Cells

INTRODUCTION

Natalizumab (NTZ), a monoclonal antibody against the integrin α4β1 (VLA-4) found on activated T cells and B cells, blocks the interaction of this integrin with adhesion molecules of central nervous system (CNS) endothelial cells and lymphocyte migration through the blood-brain barrier, effectively preventing new lesion formation and relapses in multiple sclerosis (MS). Whether NTZ treatment has additional effects on the peripheral immune system cells, and how its actions compare with other MS disease-modifying treatments, have not been extensively investigated. In particular, its effect on the proportions of circulating regulatory T cells (Treg) is unclear.

METHODS

In this study, we investigated the effect of NTZ treatment in 12 patients with relapsing MS, at 6 and 12 months after the start of treatment. We evaluated the proportions of regulatory T cells (Treg), defined by flow cytometry as CD4+ CD25++ FoxP3+ cells and CD4+ CD25++ CD127- cells at these intervals. As an exploratory study, we also investigated the NTZ effects on the proportions of bulk T and B lymphocyte populations, and of those expressing novel the markers CD195 (CCR5), CD196 (CCR6), or CD161 (KLRB1), which are involved in MS pathogenesis but have been studied less in the context of MS treatment. The effects of NTZ were compared to those obtained with 11 patients under interferon-beta-1a (IFN-β1a) treatment, and against 9 healthy volunteers.

RESULTS

We observed a transient increment in the proportion of Treg cells at 6 months, which was not sustained at 12 months. We observed a reduction in the proportion of T cells expressing CD195 (CCR5) and CD161 (KLRB1) subsets of T cells.

CONCLUSION

We conclude that NTZ does not have an effect on the proportion of Treg cells over 1 year, but it may affect the expression of molecules important for some aspects MS pathogenesis, in a manner that is not shared with IFN-β1a.

Moving to the Outskirts: Interplay Between Regulatory T Cells and Peripheral Tissues

Regulatory T cells (Tregs) restrain excessive immune responses and dampen inflammation. In addition to this classical immune suppressive role, Tregs in non-lymphoid tissues also promote tissue homeostasis, regeneration and repair. In this review, we outline our current understanding of how Tregs migrate to peripheral tissues and the factors required for their maintenance at these sites. We discuss the tissue-specific adaptations of Tregs at barrier and immuno-privileged sites and the mechanisms that regulate their function within these organs. Furthermore, we outline what is known about the interactions of Tregs with non-immune cells in the different peripheral tissues at steady state and upon challenge or tissue damage. A thorough understanding of the tissue-specific adaptations and functions of Tregs will potentially pave the way for therapeutic approaches targeting their regenerative role.

Regulatory Cells in Multiple Sclerosis: From Blood to Brain

Multiple sclerosis (MS) is a chronic, autoimmune, and neurodegenerative disease of the central nervous system (CNS) that affects myelin. The etiology of MS is unclear, although a variety of environmental and genetic factors are thought to increase the risk of developing the disease. Historically, T cells were considered to be the orchestrators of MS pathogenesis, but evidence has since accumulated implicating B lymphocytes and innate immune cells in the inflammation, demyelination, and axonal damage associated with MS disease progression. However, more recently the importance of the protective role of immunoregulatory cells in MS has become increasingly evident, such as that of myeloid-derived suppressor cells (MDSCs), regulatory T (Treg) and B (Breg) cells, or CD56bright natural killer cells. In this review, we will focus on how peripheral regulatory cells implicated in innate and adaptive immune responses are involved in the physiopathology of MS. Moreover, we will discuss how these cells are thought to act and contribute to MS histopathology, also addressing their promising role as promoters of successful remyelination within the CNS. Finally, we will analyze how understanding these protective mechanisms may be crucial in the search for potential therapies for MS.

In Vivo Induction of Regulatory T Cells Via CTLA-4 Signaling Peptide to Control Autoimmune Encephalomyelitis and Prevent Disease Relapse

Regulatory T cells play a key role in immune tolerance to self-antigens, thereby preventing autoimmune diseases. However, no drugs targeting Treg cells have been approved for clinical trials yet. Here, a chimeric peptide is generated by conjugation of the cytoplasmic domain of CTLA-4 (ctCTLA-4) with dNP2 for intracellular delivery, dNP2-ctCTLA-4, and evaluated Foxp3 expression during Th0, Th1, Treg, and Th17 differentiation dependent on TGF-β. The lysine motif of ctCTLA-4, not tyrosine motif, is required for Foxp3 expression for Treg induction and amelioration of experimental autoimmune encephalomyelitis (EAE). Transcriptome analysis reveals that dNP2-ctCTLA-4-treated T cells express Treg transcriptomic patterns with properties of suppressive functions. In addition, the molecular interaction between the lysine motif of ctCTLA-4 and PKC-η is critical for Foxp3 expression. Although both CTLA-4-Ig and dNP2-ctCTLA-4 treatment in vivo ameliorated EAE progression, only dNP2-ctCTLA-4 requires Treg cells for inhibition of disease progression and prevention of relapse. Furthermore, the CTLA-4 signaling peptide is able to induce human Tregs in vitro and in vivo as well as from peripheral blood mononuclear cells (PBMCs) of multiple sclerosis patients. These results collectively suggest that the chimeric CTLA-4 signaling peptide can be used for successful induction of regulatory T cells in vivo to control autoimmune diseases, such as multiple sclerosis.

Natalizumab Pharmacokinetics and -Dynamics and Serum Neurofilament in Patients With Multiple Sclerosis

Background: Natalizumab (NAT) is a high-efficacy treatment for relapsing remitting multiple sclerosis (RRMS). However, it is associated with an increased risk of progressive multifocal leukoencephalopathy that sometimes requires treatment cessation with a risk of returning disease activity. The aim of this study was to characterize the pharmacokinetics and -dynamics as well as neurodestruction marker serum neurofilament light chain (sNfL) in patients with RRMS and secondary progressive MS (SPMS) stopping NAT in correlation to clinical data. Methods: In this study, 50 RRMS and 9 SPMS patients after NAT cessation were included. Five RRMS patients on NAT treatment holiday were evaluated. Clinical and radiological disease activity were systemically assessed by frequent exams after NAT stop. Free NAT concentration, cell bound NAT, α4-integrin expression and α4-integrin-receptor saturation as well as immune cell frequencies were measured for up to 4 months after NAT withdrawal. Additionally, sNfL levels were observed up to 12 months in RRMS and up to 4 months in SPMS patients. Results: NAT cessation was associated with a return of disease activity in 38% of the RRMS and 33% of the SPMS patients within 12 and 7 months, respectively. Concentration of free and cell bound NAT as well as α4-integrin-receptor saturation decreased in the RRMS and SPMS patients whereas α4-integrin expression increased over time. NAT induced increase of lymphocytes and its subsets normalized and a non-significant drop of NK and Th17 T-cells counts could be detected. All RRMS patients showed physiological sNfL levels <8pg/ml 1 month after last NAT infusion. During follow-up period sNfL levels peaked up to 16-fold and were linked to return of disease activity in 19 of the 37 RRMS patients. Treatment holiday was also associated with a return of disease activity in 4 of 5 patients and with an increase of sNfL at an individual level. Conclusions: We demonstrate the reversibility of NAT pharmacodynamic and -kinetic markers. sNfL levels are associated with the recurrence of disease activity and can also serve as an early marker to predict present before onset of clinical or radiological disease activity on the individual level.

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.

Drugs Modulating CD4+ T Cells Blood-Brain Barrier Interaction in Alzheimer's Disease

The effect of Alzheimer’s disease (AD) medications on CD4+ T cells homing has not been thoroughly investigated. CD4+ T cells could both exacerbate and reduce AD symptoms based on their infiltrating subpopulations. Proinflammatory subpopulations such as Th1 and Th17 constitute a major source of proinflammatory cytokines that reduce endothelial integrity and stimulate astrocytes, resulting in the production of amyloid β. Anti-inflammatory subpopulations such as Th2 and Tregs reduce inflammation and regulate the function of Th1 and Th17. Recently, pathogenic Th17 has been shown to have a superior infiltrating capacity compared to other major CD4+ T cell subpopulations. Alzheimer’s drugs such as donepezil (Aricept), rivastigmine (Exelon), galantamine (Razadyne), and memantine (Namenda) are known to play an important part in regulating the mechanisms of the neurotransmitters. However, little is known about the effect of these drugs on CD4+ T cell subpopulations’ infiltration of the brain during AD. In this review, we focus on understanding the influence of AD drugs on CD4+ T cell subpopulation interactions with the BBB in AD. While current AD therapies improve endothelial integrity and reduce astrocytes activations, they vary according to their influence on various CD4+ T cell subpopulations. Donepezil reduces the numbers of Th1 but not Th2, Rivastigmine inhibits Th1 and Th17 but not Th2, and memantine reduces Th1 but not Treg. However, none of the current AD drugs is specifically designed to target the dysregulated balance in the Th17/Treg axis. Future drug design approaches should specifically consider inhibiting CD4+ Th17 to improve AD prognosis.

Dawn of Monitoring Regulatory T Cells in (Pre-)clinical Studies: Their Relevance Is Slowly Recognised

Regulatory T cells (Tregs) have a prominent role in the control of immune homeostasis. Pharmacological impact on their activity or balance with effector T cells could contribute to (impaired) clinical responses or adverse events. Monitoring treatment-related effects on T cell subsets may therefore be part of (pre-)clinical studies for medicinal products. However, the extent of immune monitoring performed in studies for marketing authorisation and the degree of correspondence with data available in the public domain is not known. We evaluated the presence of T cell immunomonitoring in 46 registration dossiers of monoclonal antibodies indicated for immune-related disorders and published scientific papers. We found that the depth of Treg analysis in registration dossiers was rather small. Nevertheless, data on treatment-related Treg effects are available in public academia-driven studies (post-registration) and suggest that Tregs may act as a biomarker for clinical responses. However, public data are fragmented and obtained with heterogeneity of experimental approaches from a diversity of species and tissues. To reveal the potential added value of T cell (and particular Treg) evaluation in (pre-)clinical studies, more cell-specific data should be acquired, at least for medicinal products with an immunomodulatory mechanism. Therefore, extensive analysis of T cell subset contribution to clinical responses and the relevance of treatment-induced changes in their levels is needed. Preferably, industry and academia should work together to obtain these data in a standardised manner and to enrich our knowledge about T cell activity in disease pathogenesis and therapies. This will ultimately elucidate the necessity of T cell subset monitoring in the therapeutic benefit-risk assessment.

One, No One, and One Hundred Thousand: T Regulatory Cells' Multiple Identities in Neuroimmunity

As the Nobel laureate Luigi Pirandello wrote in his novels, identities can be evanescent. Although a quarter of a century has passed since regulatory T cells (Treg) were first described, new studies continue to reveal surprising and contradictory features of this lymphocyte subset. Treg cells are the core of the immunological workforce engaged in the restraint of autoimmune or inflammatory reactions, and their characterization has revealed substantial heterogeneity and complexity in the phenotype and gene expression profiles, proving them to be a most versatile and adaptive cell type, as exemplified by their plasticity in fine-tuning immune responses. Defects in Treg function are associated with several autoimmune diseases, including multiple sclerosis, which is caused by an inappropriate immune reaction toward brain components; conversely, the beneficial effects of immunomodulating therapies on disease progression have been shown to partly act upon the biology of these cells. Both in animals and in humans the pool of circulating Treg cells is a mixture of natural (nTregs) and peripherally-induced Treg (pTregs). Particularly in humans, circulating Treg cells can be phenotypically subdivided into different subpopulations, which so far are not well-characterized, particularly in the context of autoimmunity. Recently, Treg cells have been rediscovered as mediators of tissue healing, and have also shown to be involved in organ homeostasis. Moreover, stability of the Treg lineage has recently been addressed by several conflicting reports, and immune-suppressive abilities of these cells have been shown to be dynamically regulated, particularly in inflammatory conditions, adding further levels of complexity to the study of this cell subset. Finally, Treg cells exert their suppressive function through different mechanisms, some of which—such as their ectoenzymatic activity—are particularly relevant in CNS autoimmunity. Here, we will review the phenotypically and functionally discernible Treg cell subpopulations in health and in multiple sclerosis, touching also upon the effects on this cell type of immunomodulatory drugs used for the treatment of this disease.

Regulatory B and T lymphocytes in multiple sclerosis: friends or foes?

Current clinical experience with immunomodulatory agents and monoclonal antibodies in principle has established the benefit of depleting lymphocytic populations in relapsing–remitting multiple sclerosis (RRMS). B and T cells may exert multiple pro-inflammatory actions, but also possess regulatory functions making their role in RRMS pathogenesis much more complex. There is no clear correlation of Tregs and Bregs with clinical features of the disease. Herein, we discuss the emerging data on regulatory T and B cell subset distributions in MS and their roles in the pathophysiology of MS and its murine model, experimental autoimmune encephalomyelitis (EAE). In addition, we summarize the immunomodulatory properties of certain MS therapeutic agents through their effect on such regulatory cell subsets and their relevance to clinical outcomes.

Regulation of lymphocyte trafficking in central nervous system autoimmunity

CD4⁺ T helper (Th) cells play a central role in orchestrating protective immunity but also in autoimmunity. Multiple Sclerosis (MS) is a human autoimmune disease of the central nervous system (CNS) characterized by the infiltration of inflammatory lymphocytes and myeloid cells into the brain and spinal cord, leading to demyelination, axonal damage, and progressive loss of motor functions. The release of T cells in the circulation and their migration in the central nervous system are key and tightly regulated processes which have been targeted to decrease CD4⁺ T cell presence in the CNS and limit disease progression. Here, we review two of these pathways and discuss how their blockade modulate different subsets of CD4⁺ T cells.

Regulatory Cell Populations in Relapsing-Remitting Multiple Sclerosis (RRMS) Patients: Effect of Disease Activity and Treatment Regimens

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) of autoimmune etiology that results from an imbalance between CNS-specific T effector cells and peripheral suppressive mechanisms mediated by regulatory cells (RC). In this research, we collected blood samples from 83 relapsing remitting MS (RRMS) patients and 45 healthy persons (HC), to assess the sizes of their RC populations, including CD4⁺CD25(high)Foxp3⁺ (nTregs), CD3⁺CD4⁺HLA(-)G⁺, CD3⁺CD8⁺CD28(-), CD3⁺CD56⁺, and CD56(bright) cells, and how RC are affected by disease activity (acute phase or remission) and types of treatment (methylprednisolone, interferon, or natalizumab). In addition, we isolated peripheral blood mononuclear cells (PBMC) and cultured them with peptides mapping to myelin antigens, to determine RC responsiveness to autoantigens. The results showed decreased levels of nTregs in patients in the acute phase ± methylprednisolone and in remission + natalizumab, but HC levels in patients in remission or receiving interferon. Patients + interferon had the highest levels of CD3⁺CD4⁺HLA(-)G⁺ and CD3⁺CD8⁺CD28(-) RC, and patients in the acute phase + methylprednisolone the lowest. Patients in remission had the highest levels of CD3⁺CD56⁺, and patients in remission + natalizumab the highest levels of CD56(bright) cells. Only nTregs responded to autoantigens in culture, regardless of disease activity or treatment. The highest suppressive activity was exhibited by nTregs from patients in remission. In conclusion, in RRMS disease activity and type of treatment affect different RC populations. nTregs respond to myelin antigens, indicating that it is possible to restore immunological tolerance through nTreg induction.

Integrin alpha L controls the homing of regulatory T cells during CNS autoimmunity in the absence of integrin alpha 4

Experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis (MS), results from an autoimmune attack of the central nervous system (CNS) by effector T helper (Th) 1 and Th17 cells. Regulatory T cells (Treg) can control effector T cells and limit the progression of CNS autoimmunity. Integrin alpha 4 (Itga4) is critical for the entry of Th1 but not Th17 cells into the CNS during EAE. Whether Itga4 controls the homing of Tregs in the CNS and whether Tregs can limit Th17-mediated EAE has, however, not been addressed. Through selective elimination of Itga4 in Foxp3-expressing cells, we show here that Tregs can suppress Th17-mediated EAE and enter into the CNS independently of Itga4. Furthermore, similarly to Th17 cells and in contrast to Th1 cells, Tregs depend on LFA-1 for their entry into the CNS in the absence of Itga4. Therefore, these data suggest that the efficacy of Itga4 neutralization on MS progression may be associated with the prevention of Th1 cells and the maintenance of Tregs migration into the CNS.

Cell-based modulation of autoimmune responses in multiple sclerosis and experimental autoimmmune encephalomyelitis: therapeutic implications

Multiple sclerosis (MS) is a prototypic autoimmune inflammatory disorder of the central nervous system (CNS). MS pathogenesis is a complex phenomenon that is influenced by genetic and environmental factors that lead to the dysregulation of immune homeostasis and tolerance. It has been shown that pathogenic T lymphocyte subsets, such as T helper 1 (Th1) and Th17 cells, play a crucial role in the autoimmune cascade influencing disease initiation, progression and subsequent tissue damage during MS. On the other hand, several mechanisms have been described in both patients and animal models of MS with the potential to modulate myelin-specific autoimmune responses and to facilitate amelioration of disease pathology. To this end, regulatory T cells (Tregs) are considered to be a powerful cell subset not only in the maintenance of homeostasis but also in the re-establishment of tolerance. Along these lines, other cell subsets such as dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs), γδ T cells and natural killer (NK) cells have been shown to regulate the autoimmune response in the CNS under certain circumstances. This review will attempt to summarize the relevant knowledge of the regulatory mechanisms exerted by immune cells in MS that could hold the promise for the design of novel therapeutic strategies.

VLA-4 blockade promotes differential routes into human CNS involving PSGL-1 rolling of T cells and MCAM-adhesion of TH17 cells

Schneider-Hohendorf describe expression of adhesion molecules MCAM and PSGL-1 on human CD4⁺ T cells and Th17 T cells in multiple sclerosis patients under long-term natalizumab treatment. The authors identify that despite blockade of VLA-4, MCAM⁺ T cells can migrate through the blood–brain barrier to access the CNS through PSGL-1 and MCAM.

The focus of this study is the characterization of human T cell blood–brain barrier migration and corresponding molecular trafficking signatures. We examined peripheral blood and cerebrospinal fluid immune cells from patients under long-term anti–very late antigen-4 (VLA-4)/natalizumab therapy (LTNT) and from CNS specimens. LTNT patients’ cerebrospinal fluid T cells exhibited healthy central-/effector-memory ratios, but lacked CD49d and showed enhanced myeloma cell adhesion molecule (MCAM) expression. LTNT led to an increase of PSGL-1 expression on peripheral T cells. Although vascular cell adhesion molecule-1 (VLA-4 receptor) was expressed at all CNS barriers, P-selectin (PSGL-1-receptor) was mainly detected at the choroid plexus. Accordingly, in vitro experiments under physiological flow conditions using primary human endothelial cells and LTNT patients’ T cells showed increased PSGL-1–mediated rolling and residual adhesion, even under VLA-4 blockade. Adhesion of MCAM⁺/T_H17 cells was not affected by VLA-4 blocking alone, but was abrogated when both VLA-4 and MCAM were inhibited. Consistent with these data, MCAM⁺ cells were detected in white matter lesions, and in gray matter of multiple sclerosis patients. Our data indicate that lymphocyte trafficking into the CNS under VLA-4 blockade can occur by using the alternative adhesion molecules, PSGL-1 and MCAM, the latter representing an exclusive pathway for T_H17 cells to migrate over the blood–brain barrier.

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.

Regulatory T cells in autoimmune neuroinflammation

Regulatory T cells are the central element for the maintenance of peripheral tolerance. Several subtypes of regulatory T (Treg) cells have been described, and most of them belong to the CD4(+) T-helper (Th) cell lineage. These specific subtypes can be discriminated according to phenotype and function. Forkhead box protein 3 (FoxP3)-expressing natural Treg cells (Tregs) and IL-10-producing, T-regulatory type 1 cells (Tr1) are the best-studied types of CD4(+) regulatory T cells in humans and experimental animal models. It was shown that they play a crucial role during autoimmune neuroinflammation. Both cells types seem to be particularly important for multiple sclerosis (MS). Here, we discuss the role of CD4(+) regulatory T cells in autoimmune neuroinflammation with an emphasis on Tregs and Tr1 cells in MS.

A changing treatment landscape for multiple sclerosis: challenges and opportunities

Multiple sclerosis (MS) is primarily an autoimmune disease of the central nervous system, but also encompasses prominent neurodegenerative aspects. A significant proportion of MS patients will develop neurological disability over time and up until recently treatment options have been limited. However, MS treatment is now at a stage of rapid progress, with several new drugs that have reached the market or will be launched in the near future. This provides new opportunities for individualized treatment, but also creates new challenges regarding monitoring of disease activity, long-term safety issues and efficacy, not least in patients with progressive disease.

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

Background

Changes in the blood lymphocyte composition probably both mediate and reflect the effects of natalizumab treatment in multiple sclerosis, with implications for treatment benefits and risks.

Methods

A broad panel of markers for lymphocyte populations, including states of activation and co-stimulation, as well as functional T cell responses to recall antigens and mitogens, were assessed by flow cytometry in 40 patients with relapsing multiple sclerosis before and after one-year natalizumab treatment.

Results

Absolute numbers of all major lymphocyte populations increased after treatment, most markedly for NK and B cells. The fraction of both memory and presumed regulatory B cell subsets increased, as did CD3^-CD56^dim cytotoxic NK cells, whereas CD3^-CD56^bright regulatory NK cells decreased. The increase in cell numbers was further associated with a restored T cell responsiveness to recall antigens and mitogens in functional assays.

Conclusions

Our data confirms that natalizumab treatment increases the number of lymphocytes in blood, likely mirroring the expression of VLA-4 being highest on NK and B cells. This finding supports reduction of lymphocyte extravasation as a main mode of action, although the differential effects on subpopulation composition suggests that cell-signalling may also be affected. The systemic increase in T cell responsiveness reflects the increase in numbers, and while augmenting anti-infectious responses systemically, localized responses may become correspondingly decreased.

T-cell responses after haematopoietic stem cell transplantation for aggressive relapsing-remitting multiple sclerosis

Autologous haematopoietic stem cell transplantation (HSCT) for relapsing-remitting multiple sclerosis is a potentially curative treatment, which can give rise to long-term disease remission. However, the mode of action is not yet fully understood. The aim of the study was to evaluate similarities and differences of the CD4(+) T-cell populations between HSCT-treated patients (n = 12) and healthy controls (n = 9). Phenotyping of memory T cells, regulatory T (Treg) cells and T helper type 1 (Th1) and type 17 (Th17) cells was performed. Further, T-cell reactivity to a tentative antigen, myelin oligodendrocyte glycoprotein, was investigated in these patient populations. Patients treated with natalizumab (n = 15) were included as a comparative group. White blood cells were analysed with flow cytometry and T-cell culture supernatants were analysed with magnetic bead panel immunoassays. HSCT-treated patients had similar levels of Treg cells and of Th1 and Th17 cells as healthy subjects, whereas natalizumab-treated patients had lower frequencies of Treg cells, and higher frequencies of Th1 and Th17 cells. Cells from HSCT-treated patients cultured with overlapping peptides from myelin oligodendrocyte glycoprotein produced more transforming growth factor-β1 than natalizumab-treated patients, which suggests a suppressive response. Conversely, T cells from natalizumab-treated patients cultured with those peptides produced more interleukin-17 (IL-17), IL-1 and IL-10, indicating a Th17 response. In conclusion, we demonstrate circumstantial evidence for the removal of autoreactive T-cell clones as well as development of tolerance after HSCT. These results parallel the long-term disease remission seen after HSCT.

Targeting cells in motion: migrating toward improved therapies

The development of clinical therapeutics that interfere with the migration of leukocytes has revolutionized the treatment of multiple sclerosis and holds great promise for the treatment of a wide range of inflammatory diseases. As the molecules essential for the multi-step adhesion cascade that mediates cellular migration have been elucidated, the number of potential targets available to modulate leukocyte trafficking has increased exponentially. In this Viewpoint, we briefly review our current understanding of these mole-cular targets and how these targets vary by tissue and leukocyte subset with emphasis on T cells. We then describe the two currently approved therapeutics that target cell migration, natalizumab and fingolimod, and discuss how an improved understanding of their function could pave the way for the development of safer and more efficacious therapies for inflammatory and autoimmune diseases.

Effect of natalizumab on circulating CD4+ T-cells in multiple sclerosis

In multiple sclerosis (MS), treatment with the monoclonal antibody natalizumab effectively reduces the formation of acute lesions in the central nervous system (CNS). Natalizumab binds the integrin very late antigen (VLA)-4, expressed on the surface of immune cells, and inhibits VLA-4 dependent transmigration of circulating immune-cells across the vascular endothelium into the CNS. Recent studies suggested that natalizumab treated MS patients have an increased T-cell pool in the blood compartment which may be selectively enriched in activated T-cells. Proposed causes are sequestration of activated T-cells due to reduced extravasation of activated and pro-inflammatory T-cells or due to induction of VLA-4 mediated co-stimulatory signals by natalizumab. In this study we examined how natalizumab treatment altered the distribution of effector and memory T-cell subsets in the blood compartment and if T-cells in general or myelin-reactive T-cells in particular showed signs of increased immune activation. Furthermore we examined the effects of natalizumab on CD4(+) T-cell responses to myelin in vitro. Natalizumab-treated MS patients had significantly increased numbers of effector-memory T-cells in the blood. In T-cells from natalizumab-treated MS patients, the expression of TNF-α mRNA was increased whereas the expression of fourteen other effector cytokines or transcription factors was unchanged. Natalizumab-treated MS patients had significantly decreased expression of the co-stimulatory molecule CD134 on CD4(+)CD26(HIGH) T-cells, in blood, and natalizumab decreased the expression of CD134 on MBP-reactive CD26(HIGH)CD4(+) T-cells in vitro. Otherwise CD4(+) T-cells from natalizumab-treated and untreated MS patients showed similar responses to MBP. In conclusion natalizumab treatment selectively increased the effector memory T-cell pool but not the activation state of T-cells in the blood compartment. Myelin-reactive T-cells were not selectively increased in natalizumab treated MS.

The role of regulatory T cells in neurodegenerative diseases

A sustained neuroinflammatory response is the hallmark of many neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, multiple sclerosis, and HIV-associated neurodegeneration. A specific subset of T cells, currently recognized as FOXP3(+) CD25(+) CD4(+) regulatory T cells (Tregs), are pivotal in suppressing autoimmunity and maintaining immune homeostasis by mediating self-tolerance at the periphery as shown in autoimmune diseases and cancers. A growing body of evidence shows that Tregs are not only important for maintaining immune balance at the periphery but also contribute to self-tolerance and immune privilege in the central nervous system. In this article, we first review the current status of knowledge concerning the development and the suppressive function of Tregs. We then discuss the evidence supporting a dysfunction of Tregs in several neurodegenerative diseases. Interestingly, a dysfunction of Tregs is mainly observed in the early stages of several neurodegenerative diseases, but not in their chronic stages, pointing to a causative role of inflammation in the pathogenesis of neurodegenerative diseases. Furthermore, we provide an overview of a number of molecules, such as hormones, neuropeptides, neurotransmitters, or ion channels, that affect the dysfunction of Tregs in neurodegenerative diseases. We also emphasize the effects of the intestinal microbiome on the induction and function of Tregs and the need to study the crosstalk between the enteric nervous system and Tregs in neurodegenerative diseases. Finally, we point out the need for a systems biology approach in the analysis of the enormous complexity regulating the function of Tregs and their potential role in neurodegenerative diseases.

Immunological and clinical consequences of treating a patient with natalizumab

BACKGROUND

Long-term therapy with natalizumab increases the risk of progressive multifocal leukoencephalopathy (PML).

OBJECTIVES

We present a patient study through therapy, the diagnosis of PML (after 29 infusions), plasma exchange (PE) and development of immune reconstitution inflammatory syndrome (IRIS).

METHODS

Routine diagnostics, magnetic resonance imaging (MRI), immunological status (flow cytometry, T-cell migration assays and T-cell repertoire analysis), and brain biopsy with immunohistological analysis.

RESULTS

CD49d decreased after 12 months of treatment. At PML diagnosis, CD49d expression and migratory capacity of T cells was low and peripheral T-cell receptor (TCR) complexity showed severe perturbations. The distribution of peripheral monocytes changed from CCR5+ to CCR7+. After PE some changes reverted: CD49d increased and overshot earliest levels, migratory capacities of T cells recovered and peripheral TCR complexity increased. With no clinical, routine laboratory or cerebrospinal fluid (CSF) changes, MRI 2 months after PE demonstrated progressive lesion development. Brain histopathology confirmed the presence of infiltrates indicative of IRIS without clinical signs, immunologically accompanied by CCR7/CCR5 recovery of peripheral monocytes.

CONCLUSION

Natalizumab-associated immunological changes accompanying PML were reversible after PE; IRIS can occur very late, remain asymptomatic and be elusive to CSF analysis. Our study may provide insights into the changes under treatment with natalizumab associated with JC virus control.

Massive astrocyte destruction in neuromyelitis optica despite natalizumab therapy

Auto-antibody mediated astrocyte injury is implicated as a primary event in neuromyelitis optica (NMO) by biomarker, post-mortem and experimental studies that differentiate the condition from multiple sclerosis. We describe the clinical, radiological and neuropathological features of a severe cerebral attack in a natalizumab-treated patient with relapsing myelitis and serum aquaporin-4 antibodies. Our findings support autopsy evidence that abrupt astrocyte destruction precedes demyelination in NMO, and emphasize the importance of serological testing in patients with limited disease. Adherence to current NMO diagnostic criteria may delay treatment, or lead to inappropriate therapy with beta-interferon or natalizumab.

Novel mechanisms of immune modulation of natalizumab in multiple sclerosis patients

The goal of this study was to investigate the effects of natalizumab therapy on the immune cell composition and phenotype in the blood of relapsing MS patients treated over the course of 12 months. We collected peripheral blood from 26 RRMS patients before treatment onset, and then 6 and 12 months after therapy. PBMC was isolated and then analyzed for phenotypic characteristics by FACS and for cytokine production by ELISA. The results of our studies showed changes in both numbers and activation states of immune cells following therapy. These changes were observed at the 6 month timepoint and generally persisted through the 12 month timepoint. The proportions of NK cells (CD3⁻CD56+) and hematopoetic stem cells (CD34+lin⁻) were increased after natalizumab treatment. Decreases were noted in numbers of CD14+ monocytes, and possibly their migratory potential, since their expression levels of α4β1 were decreased. Relative numbers of CD20+ B cells were increased, but the proportion of CD20+ cells expressing high levels of α4β1 integrin was decreased. While proportions of CD4+ and CD8+ T cells did not change, the percentage of cells expressing α4β1 integrin was significantly decreased for both subsets. Natalizumab therapy produces a number of phenotypic changes in the immune composition of peripheral blood. These changes may help to explain both the mechanisms of action of natalizumab and also shed light on the potential for the observed increase in PML in these patients.

Treatment with natalizumab in relapsing-remitting multiple sclerosis patients induces changes in inflammatory mechanism

Natalizumab is a widely accepted drug for the relapsing–remitting subtype of multiple sclerosis (RRMS). The present longitudinal exploratory study in RRMS patients analyzes the effects of natalizumab treatment on the levels of pro-inflammatory and anti-inflammatory cytokine protein levels and also the frequency and suppressor function of regulatory T cells. Flow cytometry was used to determine cytokines and regulatory T cell frequency while regulatory T cell suppressor function was assayed in vitro at different time-points after starting with natalizumab. Results showed serum levels of pro-inflammatory interferon gamma and interleukin (IL)-12p70, as well as anti-inflammatory IL-4 and IL-10, were elevated just a few hours or days after first IV infusion of natalizumab. Interestingly, other cytokines like IL-5 or IL-13 were also elevated while pro-inflammatory IL-17, IL-2, and IL-1β increased only after a long-term treatment, suggesting different immune mechanisms. In contrast, we did not observe any effect of natalizumab treatment on regulatory T cell frequency or activity. In conclusion, these results suggest natalizumab has other immunological effects beyond VLA-4 interaction and inhibition of CNS extravasation, the relevance of which is as yet unknown and warrants further investigation.

Intracerebral human regulatory T cells: analysis of CD4+ CD25+ FOXP3+ T cells in brain lesions and cerebrospinal fluid of multiple sclerosis patients

Impaired suppressive capacity of CD4(+)CD25(+)FOXP3(+) regulatory T cells (Treg) from peripheral blood of patients with multiple sclerosis (MS) has been reported by multiple laboratories. It is, however, currently unresolved whether Treg dysfunction in MS patients is limited to reduced control of peripheral T cell activation since most studies analyzed peripheral blood samples only. Here, we assessed early active MS lesions in brain biopsies obtained from 16 patients with MS by FOXP3 immunohistochemistry. In addition, we used six-color flow cytometry to determine numbers of Treg by analysis of FOXP3/CD127 expression in peripheral blood and cerebrospinal fluid (CSF) of 17 treatment-naïve MS patients as well as quantities of apoptosis sensitive CD45RO(hi)CD95(hi) cells in circulating and CSF Treg subsets. Absolute numbers of FOXP3(+) and CD4(+) cells were rather low in MS brain lesions and Treg were not detectable in 30% of MS biopsies despite the presence of CD4(+) cell infiltrates. In contrast, Treg were detectable in all CSF samples and Treg with a CD45RO(hi)CD95(hi) phenotype previously shown to be highly apoptosis sensitive were found to be enriched in the CSF compared to peripheral blood of MS patients. We suggest a hypothetical model of intracerebral elimination of Treg by CD95L-mediated apoptosis within the MS lesion.

CD4+T-bet+, CD4+pSTAT3+ and CD8+T-bet+ T cells accumulate in peripheral blood during NZB treatment

Circulating T cells and monocytes expressing T-bet, pSTAT1 and pSTAT3 increase in relapsing-remitting multiple sclerosis (RRMS) during relapse. Natalizumab (NZB) is an effective drug in RRMS, but exacerbation of the disease after its discontinuation has been described in some patients. The aim of this research was to study the effect of NZB treatment on circulating lymphomonocyte subpopulations expressing T-bet, pSTAT1, pSTAT3 and CD4+CD25+Foxp3+ regulatory T cells. Flow cytometry was used to evaluate the percentages of circulating CD4+ and CD8+ T cells, CD14+ monocytes and B cells expressing T-bet, pSTAT1, and pSTAT3, and CD4+CD25+Foxp3+ regulatory T cells from RRMS patients before and after 6-12 NZB infusions. In NZB-treated RRMS patients, the percentages of CD4+pSTAT1+ and CD8+pSTAT1+ T cells, CD14+pSTAT1+ monocytes, CD4+T-bet+, CD8+T-bet+ and CD4+pSTAT3+ T cells and CD14+pSTAT3+ monocytes increased after 12 drug infusions and were similar to those observed in untreated relapsing RRMS patients. Otherwise in vitro NZB exposure of peripheral blood mononuclear cells from untreated RRMS patients and controls had no effect. It was concluded that NZB treatment determines an accumulation of CD4+pSTAT1+, CD8+pSTAT1+, CD4+T-bet+, CD8+T-bet+ and CD4+STAT3+ T cells in peripheral blood that may account for the exacerbation of the disease observed in some patients after the discontinuation of the drug.

A transcription factor map as revealed by a genome-wide gene expression analysis of whole-blood mRNA transcriptome in multiple sclerosis

Background

Several lines of evidence suggest that transcription factors are involved in the pathogenesis of Multiple Sclerosis (MS) but complete mapping of the whole network has been elusive. One of the reasons is that there are several clinical subtypes of MS and transcription factors that may be involved in one subtype may not be in others. We investigate the possibility that this network could be mapped using microarray technologies and contemporary bioinformatics methods on a dataset derived from whole blood in 99 untreated MS patients (36 Relapse Remitting MS, 43 Primary Progressive MS, and 20 Secondary Progressive MS) and 45 age-matched healthy controls.

Methodology/Principal Findings

We have used two different analytical methodologies: a non-standard differential expression analysis and a differential co-expression analysis, which have converged on a significant number of regulatory motifs that are statistically overrepresented in genes that are either differentially expressed (or differentially co-expressed) in cases and controls (e.g., V$KROX_Q6, p-value <3.31E-6; V$CREBP1_Q2, p-value <9.93E-6, V$YY1_02, p-value <1.65E-5).

Conclusions/Significance

Our analysis uncovered a network of transcription factors that potentially dysregulate several genes in MS or one or more of its disease subtypes. The most significant transcription factor motifs were for the Early Growth Response EGR/KROX family, ATF2, YY1 (Yin and Yang 1), E2F-1/DP-1 and E2F-4/DP-2 heterodimers, SOX5, and CREB and ATF families. These transcription factors are involved in early T-lymphocyte specification and commitment as well as in oligodendrocyte dedifferentiation and development, both pathways that have significant biological plausibility in MS causation.

Disturbed regulatory T cell homeostasis in multiple sclerosis

The pathological features of multiple sclerosis (MS), a chronic inflammatory disorder of the central nervous system, support an autoimmune etiology. Strong evidence has been provided for a potential functional defect of CD4(+)CD25(+)FOXP3(+) regulatory T cells (Tregs) in patients with relapsing-remitting MS. More recently, alterations in homeostatic parameters related to the development and function of naive and memory-like Tregs were discovered in MS patients. In this review, we evaluate the evidence for disturbed Treg homeostasis in MS and discuss the role of potential compensatory mechanisms in the chronic disease phase. Better insights into the processes underlying the compromised immune regulation in MS patients will be important to understand the potential of Treg-based therapies.

Severe relapses after the first infusion of natalizumab in active relapsing-remitting multiple sclerosis

We describe three patients suffering from a very active form of relapsing-remitting multiple sclerosis (MS), who experienced severe disease worsening, associated with a marked increase in brain inflammation, a few days after the first administration of natalizumab. In line with preclinical studies, our observations suggest that natalizumab, when administered during active disease phases, may worsen disease evolution possibly by modifying the regulatory network in the brain. We suggest that relapsing-remitting MS patients having had a recent relapse should be treated with natalizumab only after achieving complete clinical and radiological remission.

Natalizumab treatment is associated with peripheral sequestration of proinflammatory T cells

BACKGROUND

Natalizumab is an antibody directed against integrin alpha4 that reduces disease activity in patients with multiple sclerosis (MS) by blocking migration of T and B cells into the CNS. The goal of this study was to characterize the effects of natalizumab treatment on cytokine production and expression of activation markers, costimulatory molecules, and trafficking determinants on CD4+ and CD8+ T cells.

METHODS

In a longitudinal study, we investigated the expression of surface makers and cytokine expression on peripheral blood lymphocytes from 28 patients with MS who started natalizumab treatment and were followed for 1 year. A mixed effects model was used to compare pretreatment to on-treatment measurements.

RESULTS

The frequency of CD4+ T cells producing interferon-gamma, tumor necrosis factor, and interleukin (IL)-17 upon anti-CD3 stimulation increased 6 months after initiation of natalizumab treatment and remained elevated throughout the follow-up. The frequency of CD4+ T cells expressing CD25, HLA-DR, and CCR6 ex vivo was increased at one or more time points during treatment. Among CD8+ T cells, the frequency of cells producing IL-2 and IL-17 after stimulation was increased during natalizumab treatment, as was the frequency of CD8+ T cells expressing CD58 and CCR5 ex vivo. The increase in the frequency of activated cells could not be replicated by in vitro exposure to natalizumab.

CONCLUSION

Natalizumab treatment increases the percentage of activated leukocytes producing proinflammatory cytokines in blood, presumably due to sequestration of activated cells in the peripheral circulation.