Brigitte Wildemann

Acute disseminated encephalomyelitis: A follow-up study of 40 adult patients

Objectives: To describe the clinical, CSF, and radiologic findings and long-term follow-up in a cohort of patients with acute disseminated encephalomyelitis (ADEM), and to determine possible prognostic factors for progression to MS. Methods: Forty adults (28 women, mean age 33.5 years) diagnosed with ADEM were analyzed. Clinical symptoms, cranial MRI and CSF findings, and the response to a standardized treatment during the acute phase of the disease were analyzed by chart review. The final diagnosis of ADEM or clinically definite MS was established upon follow-up examination after 8 to 137 months. The patients with ADEM and MS were compared to detect differences between the two groups. Results: Fifteen patients had a preceding infection (n = 14) or immunization (n = 1). The most frequent clinical signs were motor deficit (80%), followed by sensory deficits, brainstem signs, and ataxia. CSF findings were highly variable; normal results were present in 20% of patients. Oligoclonal bands were positive in 65% of patients. Ninety-five percent of all patients improved during the acute phase of the disease. Upon follow-up, 14 patients had developed clinically definite MS. Of the 26 patients with the final diagnosis of ADEM, two patients had died, nine had minor deficits, three had moderate deficits, and 12 patients had no remaining symptoms. Patients with the final diagnosis of ADEM were older, and more often had a preceding infection, clinical signs of brainstem involvement, a higher CSF albumin fraction, and infratentorial lesions. Conclusions: Many patients initially diagnosed with ADEM develop clinically definite MS upon long-term follow-up. The authors found no useful diagnostic criteria for the differentiation of a first episode of MS from monophasic ADEM. The term ADEM may still be employed as a description of a clinical syndrome, but should not be used as a distinct entity until reliable diagnostic criteria have been developed.

Reduced suppressive effect of CD4+CD25high regulatory T cells on the T cell immune response against myelin oligodendrocyte glycoprotein in patients with multiple sclerosis

Immunoregulatory T cells of CD4+CD25+ phenotype suppress T cell function and protect rodents from organ‐specific autoimmune disease. The human counterpart of this subset of T cells expresses high levels of CD25 and its role in human autoimmune disorders is currently under intense investigation. In multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system (CNS), the activation of circulating self‐reactive T cells with specificity for myelin components is considered to be an important disease initiating event. Here, we investigated whether MS is associated with an altered ability of CD4+CD25high regulatory T cells (Treg) to confer suppression of myelin‐specific immune responses. Whereas Treg frequencies were equally distributed in blood and cerebrospinal fluid of MS patients and did not differ compared to healthy controls, the suppressive potency of patient‐derived CD4+CD25high T lymphocytes was impaired. Their inhibitory effect on antigen‐specific T cell proliferation induced by human recombinant myelin oligodendrocyte protein as well as on immune responses elicited by polyclonal and allogeneic stimuli was significantly reduced compared to healthy individuals. The effect was persistent and not due to responder cell resistance or altered survival of Treg, suggesting that a defective immunoregulation of peripheral T cells mediated by CD4+CD25high T lymphocytes promotes CNS autoimmunity in MS.

AQP4 antibodies in neuromyelitis optica: diagnostic and pathogenetic relevance

Antibodies to aquaporin-4 (also known as AQP4-Ab or NMO-IgG) are sensitive and highly specific serum markers of autoimmune neuromyelitis optica (NMO). Second-generation recombinant diagnostic assays can detect AQP4-Ab in ≥80% of patients with NMO, and a role for AQP4-Ab in the pathophysiology of this condition was corroborated by a series of in vitro studies that demonstrated disruption of the blood–brain barrier, impairment of glutamate homeostasis and induction of necrotic cell death by AQP4-Ab-positive serum. Additional evidence for such a role has emerged from clinical observations, including the demonstration of a correlation between serum levels of AQP4-Ab and disease activity. The finding of NMO-like CNS lesions and clinical disease following passive transfer of AQP4-Ab-positive serum in several independent animal studies provided definitive proof for a pathogenic role of AQP4-Ab in vivo. Together, these findings provide a strong rationale for the use of therapies targeted against B cells or antibodies in the treatment of NMO. In this Review, we summarize the latest evidence in support of a direct involvement of AQP4-Ab in the immunopathogenesis of NMO, and critically appraise the diagnostic tests currently available for the detection of this serum reactivity.

Mechanisms of Disease: aquaporin-4 antibodies in neuromyelitis optica

Neuromyelitis optica (NMO) is a rare CNS inflammatory disorder that predominantly affects the optic nerves and spinal cord. Recent serological findings strongly suggest that NMO is a distinct disease rather than a subtype of multiple sclerosis. In NMO, serum antibodies, collectively known as NMO-IgG, characteristically bind to cerebral microvessels, pia mater and Virchow–Robin spaces. The main target antigen for this immunoreactivity has been identified as aquaporin-4 (AQP4). The antibodies are highly specific for NMO, and they are also found in patients with longitudinally extensive transverse myelitis without optic neuritis, which is thought to be a precursor to NMO in some cases. An antibody-mediated pathogenesis for NMO is supported by several observations, including the characteristics of the AQP4 antibodies, the distinct NMO pathology—which includes IgG and complement deposition and loss of AQP4 from spinal cord lesions—and emerging evidence of the beneficial effects of B-cell depletion and plasma exchange. Many aspects of the pathogenesis, however, remain unclear.

Update on the diagnosis and treatment of neuromyelitis optica: recommendations of the Neuromyelitis Optica Study Group (NEMOS).

Abstract Neuromyelitis optica (NMO, Devic’s syndrome), long considered a clinical variant of multiple sclerosis, is now regarded as a distinct disease entity. Major progress has been made in the diagnosis and treatment of NMO since aquaporin-4 antibodies (AQP4-Ab; also termed NMO-IgG) were first described in 2004. In this review, the Neuromyelitis Optica Study Group (NEMOS) summarizes recently obtained knowledge on NMO and highlights new developments in its diagnosis and treatment, based on current guidelines, the published literature and expert discussion at regular NEMOS meetings. Testing of AQP4-Ab is essential and is the most important test in the diagnostic work-up of suspected NMO, and helps to distinguish NMO from other autoimmune diseases. Furthermore, AQP4-Ab testing has expanded our knowledge of the clinical presentation of NMO spectrum disorders (NMOSD). In addition, imaging techniques, particularly magnetic resonance imaging of the brain and spinal cord, are obligatory in the diagnostic workup. It is important to note that brain lesions in NMO and NMOSD are not uncommon, do not rule out the diagnosis, and show characteristic patterns. Other imaging modalities such as optical coherence tomography are proposed as useful tools in the assessment of retinal damage. Therapy of NMO should be initiated early. Azathioprine and rituximab are suggested as first-line treatments, the latter being increasingly regarded as an established therapy with long-term efficacy and an acceptable safety profile in NMO patients. Other immunosuppressive drugs, such as methotrexate, mycophenolate mofetil and mitoxantrone, are recommended as second-line treatments. Promising new therapies are emerging in the form of anti-IL6 receptor, anti-complement or anti-AQP4-Ab biologicals.

Prevalence of Newly Generated Naive Regulatory T Cells (Treg) Is Critical for Treg Suppressive Function and Determines Treg Dysfunction in Multiple Sclerosis

The suppressive function of regulatory T cells (Treg) is impaired in multiple sclerosis (MS) patients. The mechanism underlying the Treg functional defect is unknown. Treg mature in the thymus and the majority of cells circulating in the periphery rapidly adopt a memory phenotype. Because our own previous findings suggest that the thymic output of T cells is impaired in MS, we hypothesized that an altered Treg generation may contribute to the suppressive deficiency. We therefore determined the role of Treg that enter the circulation as recent thymic emigrants (RTE) and, unlike their CD45RO+ memory counterparts, express CD31 as typical surface marker. We show that the numbers of CD31+-coexpressing CD4+CD25+CD45RA+CD45RO−FOXP3+ Treg (RTE-Treg) within peripheral blood decline with age and are significantly reduced in MS patients. The reduced de novo generation of RTE-Treg is compensated by higher proportions of memory Treg, resulting in a stable cell count of the total Treg population. Depletion of CD31+ cells from Treg diminishes the suppressive capacity of donor but not patient Treg and neutralizes the difference in inhibitory potencies between the two groups. Overall, there was a clear correlation between Treg-mediated suppression and the prevalence of RTE-Treg, indicating that CD31-expressing naive Treg contribute to the functional properties of the entire Treg population. Furthermore, patient-derived Treg, but not healthy Treg, exhibit a contracted TCR Vβ repertoire. These observations suggest that a shift in the homeostatic composition of Treg subsets related to a reduced thymic-dependent de novo generation of RTE-Treg with a compensatory expansion of memory Treg may contribute to the Treg defect associated with MS.

Cerebrospinal fluid findings in aquaporin-4 antibody positive neuromyelitis optica: results from 211 lumbar punctures.

BACKGROUND Neuromyelitis optica (NMO, Devic disease) is a severely disabling autoimmune disorder of the CNS, which was considered a subtype of multiple sclerosis (MS) for many decades. Recently, however, highly specific serum autoantibodies (termed NMO-IgG or AQP4-Ab) have been discovered in a subset (60-80%) of patients with NMO. These antibodies were subsequently shown to be directly involved in the pathogenesis of the condition. AQP4-Ab positive NMO is now considered an immunopathogenetically distinct disease in its own right. However, to date little is known about the cerebrospinal fluid (CSF) in AQP4-Ab positive NMO. OBJECTIVE To describe systematically the CSF profile of AQP4-Ab positive patients with NMO or its formes frustes, longitudinally extensive myelitis and optic neuritis. MATERIAL AND METHODS Cytological and protein biochemical results from 211 lumbar punctures in 89 AQP4-Ab positive patients of mostly Caucasian origin with neuromyelitis optica spectrum disorders (NMOSD) were analysed retrospectively. RESULTS CSF-restricted oligoclonal IgG bands, a hallmark of MS, were absent in most patients. If present, intrathecal IgG (and, more rarely, IgM) synthesis was low, transient, and, importantly, restricted to acute relapses. CSF pleocytosis was present in around 50% of samples, was mainly mild (median, 19 cells/μl; range 6-380), and frequently included neutrophils, eosinophils, activated lymphocytes, and/or plasma cells. Albumin CSF/serum ratios, total protein and CSF L-lactate levels correlated significantly with disease activity as well as with the length of the spinal cord lesions in patients with acute myelitis. CSF findings differed significantly between patients with acute myelitis and patients with acute optic neuritis at the time of LP. Pleocytosis and blood CSF barrier dysfunction were also present during remission in some patients, possibly indicating sustained subclinical disease activity. CONCLUSION AQP4-Ab positive NMOSD is characterized by CSF features that are distinct from those in MS. Our findings are important for the differential diagnosis of MS and NMOSD and add to our understanding of the immunopathogenesis of this devastating condition.

Standardized method for the detection of antibodies to aquaporin-4 based on a highly sensitive immunofluorescence assay employing recombinant target antigen

BACKGROUND Recently, a highly specific serum autoantibody was discovered in patients with neuromyelitis optica, called NMO-IgG, and aquaporin-4, the most abundant water channel in the CNS, was identified as the target antigen. Several assays for the detection of NMO-IgG/AQP4-Ab have been described. Tests based on recombinant human AQP4 have been repeatedly demonstrated to be more sensitive than the previous gold standard assay, i.e. immunohistochemistry (IHC) on mouse brain tissue. However, the sophisticated techniques applied restrict their availability to few laboratories worldwide. OBJECTIVE To develop an easy-to-use, recombinant immunofluorescence assay (rIFA) suitable for standardized and high-throughput detection of NMO-IgG/AQP4-Ab. METHODS HEK293 cells seeded on cover glasses were transfected with full-length recombinant human AQP4 at large scale. Cover glasses with the immobilized cells were cut into millimetre-sized fragments and transferred to microscopy slides. 151 serum samples from patients with NMO spectrum disorders (NMOSD) and controls were analysed both in the standard IHC assay and in the newly developed rIFA. RESULTS 25/32 (78.1%) patients with clinically definite NMO and 36/51 (70.6%) of total patients with NMOSD were positive for NMO-IgG/AQP4-Ab in the rIFA compared to 65.6% and 58.8%, respectively, in the IHC assay. CONCLUSION The recombinant IFA presented here provides laboratories familiar with indirect immunofluorescence microscopy with a highly sensitive and reproducible diagnostic tool for standardized detection of antibodies to AQP4. This new approach could make AQP4-Ab testing, which is of high clinical relevance, more widely available.

Thymic export function and T cell homeostasis in patients with relapsing remitting multiple sclerosis.

Multiple sclerosis (MS) is an inflammatory and possibly autoimmune mediated demyelinating disease of the CNS. Autoimmunity within the CNS may be triggered by dysfunction of peripheral immune tolerance mechanisms via changes in the homeostatic composition of peripheral T cells. We have assessed the release of naive T lymphocytes from the thymus in patients with relapsing remitting MS (RRMS) to identify alterations in the equilibrium of the peripheral T cell compartment. Thymic T cell production was estimated by measuring TCR excision circles (TRECs) as a traceable molecular marker in recent thymic emigrants. A total of 46 treatment-naive patients with active RRMS and 49 gender- and age-matched healthy persons were included in the study. The levels of TREC-expressing CD4+ and CD8+ T lymphocytes were significantly decreased in MS patients, and TREC quantities overall matched those of 30 years older healthy individuals. The average concentrations of TRECs/106 CD4+ and CD8+ T lymphocytes derived from MS patients and healthy donors were 26 × 103/106 and 28 × 103/106 vs 217 × 103/106 and 169 × 103/106, respectively. To account for any influence of T cell proliferation on TREC levels, we assayed T lymphocytes from additional patients with MS and normal individuals for telomere length (n = 20) and telomerase activity (8 MS patients, 16 controls), respectively. There were no significant differences between CD4+ and CD8+ T cells from MS patients and controls. Altogether, our findings suggest that an impaired thymic export function and, as a consequence, altered ability to maintain T cell homeostasis and immune tolerance may play an important pathogenic role in RRMS.

Cerebrospinal fluid antibodies to aquaporin-4 in neuromyelitis optica and related disorders: frequency, origin, and diagnostic relevance

BackgroundIn 70-80% of cases, neuromyelitis optica (NMO) is associated with highly specific serum auto-antibodies to aquaporin-4 (termed AQP4-Ab or NMO-IgG). Recent evidence strongly suggests that AQP4-Ab are directly involved in the immunopathogenesis of NMO.ObjectiveTo assess the frequency, syndrome specificity, diagnostic relevance, and origin of cerebrospinal fluid (CSF) AQP4-Ab in patients with NMO spectrum disorders (NMOSD).Methods87 CSF samples from 37 patients with NMOSD and 42 controls with other neurological diseases were tested for AQP4-Ab in a cell based assay using recombinant human AQP4. Twenty-three paired CSF and serum samples from AQP4-Ab seropositive NMOSD patients were further analysed for intrathecal IgG synthesis to AQP4.ResultsAQP4-Ab were detectable in 68% of CSF samples from AQP4-Ab seropositive patients with NMOSD, but in none of the CSF samples from AQP4-Ab seronegative patients with NMOSD and in none of the control samples. Acute disease relapse within 30 days prior to lumbar puncture, AQP4-Ab serum titres >1:250, and blood-CSF barrier dysfunction, but not treatment status, predicted CSF AQP4-Ab positivity. A positive AQP4-specific antibody index was present in 1/23 samples analysed.ConclusionsAQP4-Ab are detectable in the CSF of most patients with NMOSD, mainly during relapse, and are highly specific for this condition. In the cohort analysed in this study, testing for CSF AQP4-Ab did not improve the sensitivity and specificity of the current diagnostic criteria for NMO. The substantial lack of intrathecal AQP4-Ab synthesis in patients with NMOSD may reflect the unique localisation of the target antigen at the blood brain barrier, and is important for our understanding of the immunopathogenesis of the disease.