Characterization of the T cell receptor repertoire in the Japanese neuromyelitis optica: T cell activity is up-regulated compared to multiple sclerosis

Foxp3+ regulatory T cells expression in neuromyelitis optica spectrum disorders

BACKGROUND

Alterations in the frequency or function of regulatory T cells (Tregs), which play a critical role in the maintenance of peripheral immune tolerance, are known to be involved in the pathogenesis of several autoimmune diseases. Neuromyelitis optica spectrum disorders (NMOSD) are autoimmune inflammatory diseases of the central nervous system (CNS), of which the etiology and mechanisms underlying its development are not completely understood. Although there is increasing evidence for the involvement of effector T cells in NMOSD, no data are available regarding the role of Tregs in its pathogenesis.

AIM

The aim of this study was to investigate the mRNA expression level of regulatory T cell genes in NMOSD.

METHODS

We used gene expression array and RT-PCR analysis to study Treg cell genes in NMOSD RESULTS: A distinctive Treg gene signature in the peripheral blood of NMOSD patients is described, as well as significantly decreased FoxP3 mRNA expression in the peripheral blood mononuclear cells (PBMCs) of the patients vs that in the healthy controls (HCs) (NMOSD,1.8RQ vs HC, 6.8RQ, p = 0.01).

CONCLUSIONS

The present study shows downregulation at the mRNA expression level of a Treg key transcription factor FoxP3, in NMOSD. Exploration of Tregs function and interconnections in the peripheral immune system should advance our understanding of NMOSD pathogenesis.

Reduced expression of the IL7Ra signaling pathway in Neuromyelitis optica

Neuromyelitis optica (NMO) is a chronic inflammatory demyelinating autoimmune disease of the central nervous system that most commonly affects the optic nerves and spinal cord. To characterize the immunological pathways involved in NMO, whole blood RNA expression array was performed using Nanostring nCounter technology. Two major clusters of genes were found associated with NMO: T cell-associated genes and the TNF/NF-kB signaling pathway. Analysis of the genes within the first cluster confirmed significantly reduced expression of IL7Ra (CD127) in the peripheral blood of NMO patients vs that in healthy controls. IL7Ra upstream transcription factors and its downstream survival signaling pathway were also markedly reduced. In line with the essential role of IL7Ra in T cell maturation and survival, a significantly lower number of naïve T cells, and reduced T cell survival signaling mediated by increased BID (BH3-interacting domain death agonist) expression and increased apoptosis was observed. Cumulatively, these findings indicate that the IL7Ra signaling pathway may play a role in the autoimmune process in NMO.

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

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

Study of the T-cell receptor repertoire by CDR3 spectratyping

The T-cell receptor (TCR) is the key player within the so called immunological synapse and the analysis of its repertoire offers a picture of both versatility and wideness of the whole immune T-cell compartment. Among the different approaches applied to its study the so-called spectratyping identifies the pattern of the third complementarity determining region (CDR3) length distribution in each one of the beta variable (TRBV) subfamilies encoded by the corresponding genes. This technique consists in a CDR3 fragment analysis through capillary electrophoresis, performed after cell separation, RNA extraction and reverse transcriptase PCR. This review will run through the most relevant studies which have tried to dissect the TCR repertoire usage in patients with different immune-mediated and infective diseases as well as solid or haematologic malignancies.

T-cell responses to distinct AQP4 peptides in patients with neuromyelitis optica (NMO)

BACKGROUND

Although antibodies to aquaporin-4(AQP4) are strongly associated with Neuromyelitis optica (NMO), the sole transfer of these antibodies is not sufficient to induce an NMO-like disease in experimental animals and T-cells and complement are also needed. Initial data indicating the presence of T-cell responses to AQP4 in patients with NMO, have beeen recently reported.

OBJECTIVE

To evaluate the T-cell responses to specific AQP4 peptides/epitopes in patients with NMO and multiple sclerosis (MS).

METHODS

Peripheral blood mononuclear cells (PBMCs) were obtained from 14 patients fulfilling the criteria for definite NMO and the proliferation responses to one of 15 distinct pentadecapeptides of AQP4, spanning the whole protein (except of its transmembrane parts) were tested by a standard [H3]-thymidine uptake assay and compared with those of 9 healthy controls and 7 MS patients. A cytometric bead array assay (CBA) and flow cytometry were used to evaluate cytokine (IFNγ, IL17, IL2, IL4, IL5, IL10 and TNFα) and chemokine (CXCL8, CCL5, CXCL10, CXCL9, CCL2) secretion by PHA-stimulated PBMCs and AQP4-specific T-cell lines.

RESULTS

Four main immunodominant epitopes of the AQP4 protein (p137-151, p222-236, p217-231 and the p269-283) were identified in the NMO group. The first two epitopes (assigned as peptides 3 and 9) showed the highest sensitivity (~60% positivity), whereas the latter two (assigned as peptides 8 and 11), the higher specificity. Longitudinal follow up of 5 patients revealed changes in the epitope-specificities during the course of NMO. T-cell lines specific for the AQP4 peptides, produced from NMO patients (but not healthy donors) secreted mainly IL-17 and IL-10 and less IFNγ.

CONCLUSIONS

Our findings indicate that T-cells bearing characteristics of both Th1 and Th17 T-cells and targeting specific immunodominant epitopes of the AQP4 protein might be involved in the pathogenesis of NMO.

Copy number variations in multiple sclerosis and neuromyelitis optica

OBJECTIVE

To clarify the potential association of copy number variations (CNVs) with multiple sclerosis (MS) and neuromyelitis optica (NMO) in Japanese cases.

METHODS

Genome-wide association analyses of CNVs among 277 MS patients, 135 NMO/NMO spectrum disorder (NMOSD) patients, and 288 healthy individuals as a discovery cohort, and among 296 MS patients, 76 NMO/NMOSD patients, and 790 healthy individuals as a replication cohort were performed using high-density single nucleotide polymorphism microarrays.

RESULTS

A series of discovery and replication studies revealed that most identified CNVs were 5 to 50kb deletions at particular T cell receptor (TCR) gamma and alpha loci regions. Among these CNVs, a TCR gamma locus deletion was found in 16.40% of MS patients (p = 2.44E-40, odds ratio [OR] = 52.6), and deletion at the TCR alpha locus was found in 17.28% of MS patients (p = 1.70E-31, OR = 13.0) and 13.27% of NMO/NMOSD patients (p = 5.79E-20, OR = 54.6). These CNVs were observed in peripheral blood T-cell subsets only, suggesting the CNVs were somatically acquired. NMO/NMOSD patients carrying the CNV tended to be seronegative for anti-aquaporin-4 antibody or had significantly lower titers than those without CNV.

INTERPRETATION

Deletion-type CNVs at specific TCR loci regions contribute to MS and NMO susceptibility.

Neuromyelitis optica: clinical features, immunopathogenesis and treatment

The term 'neuromyelitis optica' ('Devic's syndrome', NMO) refers to a syndrome characterized by optic neuritis and myelitis. In recent years, the condition has raised enormous interest among scientists and clinical neurologists, fuelled by the detection of a specific serum immunoglobulin (Ig)G reactivity (NMO-IgG) in up to 80% of patients with NMO. These autoantibodies were later shown to target aquaporin-4 (AQP4), the most abundant water channel in the central nervous system (CNS). Here we give an up-to-date overview of the clinical and paraclinical features, immunopathogenesis and treatment of NMO. We discuss the widening clinical spectrum of AQP4-related autoimmunity, the role of magnetic resonance imaging (MRI) and new diagnostic means such as optical coherence tomography in the diagnosis of NMO, the role of NMO-IgG, T cells and granulocytes in the pathophysiology of NMO, and outline prospects for new and emerging therapies for this rare, but often devastating condition.

Monoclonal antibodies in treatment of multiple sclerosis

Monoclonal antibodies (mAbs) are used as therapeutics in a number of disciplines in medicine, such as oncology, rheumatology, gastroenterology, dermatology and transplant rejection prevention. Since the introduction and reintroduction of the anti-alpha4-integrin mAb natalizumab in 2004 and 2006, mAbs have gained relevance in the treatment of multiple sclerosis (MS). At present, numerous mAbs have been tested in clinical trials in relapsing-remitting MS, and in progressive forms of MS. One of the agents that might soon be approved for very active forms of relapsing-remitting MS is alemtuzumab, a humanized mAb against CD52. This review provides insights into clinical studies with the mAbs natalizumab, alemtuzumab, daclizumab, rituximab, ocrelizumab and ofatumumab.

Abnormal nerve conduction study findings indicating the existence of peripheral neuropathy in multiple sclerosis and neuromyelitis optica

OBJECTIVE

Chronic inflammatory demyelinating polyneuropathy (CIDP) has been reported in patients with multiple sclerosis (MS). However, there have been limited reports of peripheral neuropathy as a complication of neuromyelitis optica (NMO). In this paper, we showed the characteristics and differences between peripheral neuropathy as a complication of MS and NMO.

METHOD

We analyzed a series of 58 MS and 28 NMO patients and evaluated nerve conduction studies (NCS) in 21 MS and 5 NMO patients.

RESULTS

Six of the 58 MS and 3 of the 28 NMO patients revealed abnormal NCS findings. Three (5.2%) of the 58 MS patients fulfilled the criteria for CIDP. One (3.6%) of the 28 NMO patients showed peripheral neuropathy at the same time of NMO relapse, although CIDP was not seen in NMO. The other 5 (3 MS and 2 NMO) patients were complicated with neuropathy caused by concomitant diabetes mellitus and Sjögren's syndrome.

CONCLUSION

Frequency of abnormal NCS findings might exhibit no significant difference between MS and NMO, although the cause and pathophysiology of peripheral neuropathy were different in MS and in NMO. There might be a group of NMO who were affected simultaneously in the central and peripheral nervous tissues.

Immunology of neuromyelitis optica: a T cell-B cell collaboration

Neuromyelitis optica (NMO) is a debilitating autoimmune inflammatory disease of the central nervous system (CNS) that is distinct from multiple sclerosis (MS). The discovery of NMO-immunoglobulin G (IgG) in the serum of NMO-but not MS-patients was a breakthrough in defining diagnostic criteria for NMO. NMO-IgG is an antibody directed against the astrocytic water channel protein aquaporin-4 (AQP4). While there is evidence that NMO-IgG is also involved in mediating tissue damage in the CNS, many aspects of the pathogenic cascade in NMO remain to be determined. It is clear that antigen-specific T cells contribute to the generation of NMO-IgG in the peripheral immune compartment, as well as to the development of NMO lesions in the CNS. T helper 17 (Th17) cells, equipped both in providing B cell help and inducing tissue inflammation, may be involved in NMO development and pathogenesis. Here, we review immunologic aspects of NMO, placing recent findings in the biology of T-B cell cooperation into perspective with autoimmunity of the CNS.

Cross-immunoreactivity between bacterial aquaporin-Z and human aquaporin-4: potential relevance to neuromyelitis optica

Neuromyelitis optica (NMO) is a chronic inflammatory disease of the CNS that is mediated, in part, by a self-reactive Ab against the astrocyte aquaporin-4 protein. In the current study, we examined the possibility and the biological significance of cross-immunoreactivity between bacterial aquaporin-Z and human aquaporin-4 proteins. Sequence-alignment analysis of these proteins revealed several regions of significant structural homology. Some of the homologous regions were also found to overlap with important immune and disease-relevant epitopes. Cross-immunoreactivity between aquaporin-Z and aquaporin-4 was investigated and ascertained in multiple immune-based assays using sera from patients with neuromyelitis optica, immune mouse serum, and Abs raised against aquaporin-Z. The biological significance of this phenomenon was established in series of experiments demonstrating that induction of an immune response against aquaporin-Z or its homologous regions can also trigger an autoimmune reaction against aquaporin-4 and inflammation of the CNS. Our study indicates that the autoimmune response against aquaporin-4 in neuromyelitis optica may be triggered by infection-induced cross-immunoreactivity and presents a new perspective on the pathogenesis of this disease.

Aquaporin 4-specific T cells in neuromyelitis optica exhibit a Th17 bias and recognize Clostridium ABC transporter

OBJECTIVE

Aquaporin 4 (AQP4)-specific autoantibodies in neuromyelitis optica (NMO) are immunoglobulin (Ig)G1, a T cell-dependent Ig subclass, indicating that AQP4-specific T cells participate in NMO pathogenesis. Our goal was to identify and characterize AQP4-specific T cells in NMO patients and healthy controls (HC).

METHODS

Peripheral blood T cells from NMO patients and HC were examined for recognition of AQP4 and production of proinflammatory cytokines. Monocytes were evaluated for production of T cell-polarizing cytokines and expression of costimulatory molecules.

RESULTS

T cells from NMO patients and HC proliferated to intact AQP4 or AQP4 peptides (p11-30, p21-40, p61-80, p131-150, p156-170, p211-230, and p261-280). T cells from NMO patients demonstrated greater proliferation to AQP4 than those from HC, and responded most vigorously to p61-80, a naturally processed immunodominant determinant of intact AQP4. T cells were CD4(+), and corresponding to association of NMO with human leukocyte antigen (HLA)-DRB1*0301 and DRB3, AQP4 p61-80-specific T cells were HLA-DR restricted. The T-cell epitope within AQP4 p61-80 was mapped to 63-76, which contains 10 residues with 90% homology to a sequence within Clostridium perfringens adenosine triphosphate-binding cassette (ABC) transporter permease. T cells from NMO patients proliferated to this homologous bacterial sequence, and cross-reactivity between it and self-AQP4 was observed, supporting molecular mimicry. In NMO, AQP4 p61-80-specific T cells exhibited Th17 polarization, and furthermore, monocytes produced more interleukin 6, a Th17-polarizing cytokine, and expressed elevated CD40 and CD80 costimulatory molecules, suggesting innate immunologic dysfunction.

INTERPRETATION

AQP4-specific T-cell responses are amplified in NMO, exhibit a Th17 bias, and display cross-reactivity to a protein of an indigenous intestinal bacterium, providing new perspectives for investigating NMO pathogenesis.

Pathogenic T cell responses against aquaporin 4

Inflammatory lesions in the central nervous system of patients with neuromyelitis optica are characterized by infiltration of T cells and deposition of aquaporin-4-specific antibodies and complement on astrocytes at the glia limitans. Although the contribution of aquaporin-4-specific autoantibodies to the disease process has been recently elucidated, a potential role of aquaporin-4-specific T cells in lesion formation is unresolved. To address this issue, we raised aquaporin-4-specific T cell lines in Lewis rats and characterized their pathogenic potential in the presence and absence of aquaporin-4-specific autoantibodies of neuromyelitis optica patients. We show that aquaporin-4-specific T cells induce brain inflammation with particular targeting of the astrocytic glia limitans and permit the entry of pathogenic anti-aquaporin-4-specific antibodies to induce NMO-like lesions in spinal cord and brain. In addition, transfer of aquaporin-4-specific T cells provoked mild (subclinical) myositis and interstitial nephritis. We further show that the expression of the conformational epitope, recognized by NMO patient-derived aquaporin-4-specific antibodies is induced in kidney cells by the pro-inflammatory cytokine gamma-interferon. Our data provide further support for the view that NMO lesions may be induced by a complex interplay of T cell mediated and humoral immune responses against aquaporin-4.

Immunodominant T cell determinants of aquaporin-4, the autoantigen associated with neuromyelitis optica

Autoantibodies that target the water channel aquaporin-4 (AQP4) in neuromyelitis optica (NMO) are IgG1, a T cell-dependent Ig subclass. However, a role for AQP4-specific T cells in this CNS inflammatory disease is not known. To evaluate their potential role in CNS autoimmunity, we have identified and characterized T cells that respond to AQP4 in C57BL/6 and SJL/J mice, two strains that are commonly studied in models of CNS inflammatory diseases. Mice were immunized with either overlapping peptides or intact hAQP4 protein encompassing the entire 323 amino acid sequence. T cell determinants identified from examination of the AQP4 peptide (p) library were located within AQP4 p21-40, p91-110, p101-120, p166-180, p231-250 and p261-280 in C57BL/6 mice, and within p11-30, p21-40, p101-120, p126-140 and p261-280 in SJL/J mice. AQP4-specific T cells were CD4⁺ and MHC II-restricted. In recall responses to immunization with intact AQP4, T cells responded primarily to p21-40, indicating this region contains the immunodominant T cell epitope(s) for both strains. AQP4 p21-40-primed T cells secreted both IFN-γ and IL-17. The core immunodominant AQP4 21-40 T cell determinant was mapped to residues 24-35 in C57BL/6 mice and 23-35 in SJL/J mice. Our identification of the AQP4 T cell determinants and characterization of its immunodominant determinant should permit investigators to evaluate the role of AQP4-specific T cells in vivo and to develop AQP4-targeted murine NMO models.

Relapsing neuromyelitis optica: demographic and clinical features in Iranian patients

BACKGROUND

Neuromyelitis Optica (NMO) is a severe inflammatory demyelinating disease of the central nervous system with distinguishing features from multiple sclerosis (MS). NMO has an unknown etiology with poor prognosis in which anti-aquaporin-4 receptor IgG seems to play a major role. The purpose of this study is to represent a clinical and demographic data of NMO in Iranian population.

METHODS

Of 1800 patients attending our MS clinic, 44 patients with NMO were recruited from 2006 to 2009.

RESULTS

Female to male ratio was 3:1 and the disease affected women in younger ages than men (P = 0.04). The median expanded disability status scale score was 3 and the mean duration of symptoms was 4.53 +/- 3.41 (median = 4) years with annual relapse rate of 1.13 year/patient. The most frequent symptoms at presentation were optic neuritis 22 (50%) and transverse myelitis 14 (31.8%). Out of 12 patients whose titer of NMO-IgG was measured, four (30.7%) patients were seropositive. Twenty-eight patients (63%) received azathioprine for a mean duration of 16.84 +/- 27.91 months with significantly lower annual relapse rate (0.4 year/patient).

CONCLUSIONS

Iranian patients as a Caucasian population living in Asia seem to have the same clinical features in comparison with the reported studies from Western countries. Although the duration of follow-up was not too long, but they may possibly have a more benign course.

Neuromyelitis optica: pathogenicity of patient immunoglobulin in vivo

OBJECTIVE

Severe inflammation and astrocyte loss with profound demyelination in spinal cord and optic nerves are typical pathological features of neuromyelitis optica (NMO). A diagnostic hallmark of this disease is the presence of serum autoantibodies against the water channel aquaporin-4 (AQP-4) on astrocytes.

METHODS

We induced acute T-cell-mediated experimental autoimmune encephalomyelitis in Lewis rats and confronted the animals with an additional application of immunoglobulins from AQP-4 antibody-positive and -negative NMO patients, multiple sclerosis patients, and control subjects.

RESULTS

The immunoglobulins from AQP-4 antibody-positive NMO patients are pathogenic. When they reach serum titers in experimental animals comparable with those seen in NMO patients, they augment clinical disease and induce lesions in the central nervous system that are similar in structure and distribution to those seen in NMO patients, consisting of AQP-4 and astrocyte loss, granulocytic infiltrates, T cells and activated macrophages/microglia cells, and an extensive immunoglobulin and complement deposition on astrocyte processes of the perivascular and superficial glia limitans. AQP-4 antibody containing NMO immunoglobulin injected into naïve rats, young rats with leaky blood-brain barrier, or after transfer of a nonencephalitogenic T-cell line did not induce disease or neuropathological alterations in the central nervous system. Absorption of NMO immunoglobulins with AQP-4-transfected cells, but not with mock-transfected control cells, reduced the AQP-4 antibody titers and was associated with a reduction of astrocyte pathology after transfer.

INTERPRETATION

Human anti-AQP-4 antibodies are not only important in the diagnosis of NMO but also augment disease and induce NMO-like lesions in animals with T-cell-mediated brain inflammation.

Neuromyelitis optica pathogenesis and aquaporin 4

Neuromyelitis optica (NMO) is a severe, debilitating human disease that predominantly features immunopathology in the optic nerves and the spinal cord. An IgG1 autoantibody (NMO-IgG) that binds aquaporin 4 (AQP4) has been identified in the sera of a significant number of NMO patients, as well as in patients with two related neurologic conditions, bilateral optic neuritis (ON), and longitudinal extensive transverse myelitis (LETM), that are generally considered to lie within the NMO spectrum of diseases. NMO-IgG is not the only autoantibody found in NMO patient sera, but the correlation of pathology in central nervous system (CNS) with tissues that normally express high levels of AQP4 suggests NMO-IgG might be pathogenic. If this is the case, it is important to identify and understand the mechanism(s) whereby an immune response is induced against AQP4. This review focuses on open questions about the "events" that need to be understood to determine if AQP4 and NMO-IgG are involved in the pathogenesis of NMO. These questions include: 1) How might AQP4-specific T and B cells be primed by either CNS AQP4 or peripheral pools of AQP4? 2) Do the different AQP4-expressing tissues and perhaps the membrane structural organization of AQP4 influence NMO-IgG binding efficacy and thus pathogenesis? 3) Does prior infection, genetic predisposition, or underlying immune dysregulation contribute to a confluence of events which lead to NMO in select individuals? A small animal model of NMO is essential to demonstrate whether AQP4 is indeed the incipient autoantigen capable of inducing NMO-IgG formation and NMO. If the NMO model is consistent with the human disease, it can be used to examine how changes in AQP4 expression and blood-brain barrier (BBB) integrity, both of which can be regulated by CNS inflammation, contribute to inductive events for anti-AQP4-specific immune response. In this review, we identify reagents and experimental questions that need to be developed and addressed to enhance our understanding of the pathogenesis of NMO. Finally, dysregulation of tolerance associated with autoimmune disease appears to have a role in NMO. Animal models would allow manipulation of hormone levels, B cell growth factors, and other elements known to increase the penetrance of autoimmune disease. Thus an AQP4 animal model would provide a means to manipulate events which are now associated with NMO and thus demonstrate what set of events or multiplicity of events can push the anti-AQP4 response to be pathogenic.