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Optic Neuritis: A Model for the Immuno-pathogenesis of Central Nervous System Inflammatory Demyelinating Diseases
Abstract
Evidence for the tenuous regulation between the immune system and central nervous system (CNS) can be found with examples of interaction between these organ systems gone awry. Multiple sclerosis (MS) is the prototypical inflammatory disease of the CNS and is characterized by widely distributed inflammatory demyelinating plaques that can involve the brain, spinal cord and/or optic nerves. Optic neuritis (ON), inflammatory injury of the optic nerve that frequently occurs in patients with MS, has been the focus of intense study in part given the readily accessible nature of clinical outcome measures. Exploring the clinical and pathological features of ON in relation to other inflammatory demyelinating conditions of the CNS, namely MS and neuromyelitis optica, provides an opportunity to glean common and distinct mechanisms of disease. Emerging data from clinical studies along with various animal models involving ON implicate innate and adaptive immune responses directed at glial targets, including myelin oligodendrocyte glycoprotein and aquaporin 4. Resolution of inflammation in ON is commonly observed both clinically and experimentally, but persistent nerve injury is also one emerging hallmark of ON. One hypothesis seeking evaluation is that, in comparison to other sites targeted in MS, the optic nerve is a highly specialized target within the CNS predisposing to unique immunologic processes that generate ON. Overall, ON serves as a highly relevant entity for understanding the pathogenesis of other CNS demyelinating conditions, most notably MS.
... Structural and functional abnormalities in the visual system are targeted in most patients with MS, typically at the earliest stages of the disease, defining a hallmark feature of MS, namely optic neuritis (ON). The evolution of the clinical picture of patients with MS is extremely variable and heterogeneous in terms of locations and extensions of brain and spinal cord lesions [3]. ON is an inflammatory injury of the optic nerve that leads to visual disability. ...
... Activated T cells mature and expand clonally before dividing into effector cells and migrating through the bloodstream to breach the blood-brain barrier (BBB). Endothelial cells in the CNS microvasculature contain adhesion molecules, which activated T cells can attach to and penetrate [3,18]. The release of cytokines and other proinflammatory mediators aggravates the inflammatory environment, attracting more immune cells to the CNS and eventually leading to demyelination [3,21,22]. ...
... Endothelial cells in the CNS microvasculature contain adhesion molecules, which activated T cells can attach to and penetrate [3,18]. The release of cytokines and other proinflammatory mediators aggravates the inflammatory environment, attracting more immune cells to the CNS and eventually leading to demyelination [3,21,22]. Using a range of experimental animal models, the immunological processes underlying demyelination of the optic nerve secondary to the inflammatory process may be easily investigated [4]. The pathophysiological processes mentioned above are mediated by a variety of molecules with intrinsic action that potentiate the associated pro-inflammatory status [23]. ...
Multiple sclerosis is a central nervous system inflammatory demyelinating disease with a wide range of clinical symptoms, ocular involvement being frequently marked by the presence of optic neuritis (ON). The emergence and progression of ON in multiple sclerosis is based on various pathophysiological mechanisms, disease progression being secondary to inflammation, demyelination, or axonal degeneration. Early identification of changes associated with axonal degeneration or further investigation of the molecular processes underlying remyelination are current concerns of researchers in the field in view of the associated therapeutic potential. This article aims to review and summarize the scientific literature related to the main molecular mechanisms involved in defining ON as well as to analyze existing data in the literature on remyelination strategies in ON and their impact on long-term prognosis.
... O ptic neuropathies encompass a set of neurodegenerative disorders, with notable examples including glaucoma, optic neuritis, and hereditary optic neuropathies. [1][2][3][4] RGCs, the cells most affected in optic neuropathies, are the output neurons of the vertebrate retina. Mechanistically, RGC loss and axon degeneration have been linked to activation of immune cells, altered trabecular meshwork cells, neuroinflammatory processes, dysregulated gut microbiota, and oxidative stress. ...
Purpose:
Retinal ganglion cell (RGC) loss provides the basis for diagnosis and stage determination of many optic neuropathies, and quantification of RGC survival is a critical outcome measure in models of optic neuropathy. This study examines the accuracy of manual RGC counting using two selective markers, Brn3a and RBPMS.
Methods:
Retinal flat mounts from 1- to 18-month-old C57BL/6 mice, and from mice after microbead (MB)-induced intraocular pressure (IOP) elevation, are immunostained with Brn3a and/or RBPMS antibodies. Four individuals masked to the experimental conditions manually counted labeled RGCs in three copies of five images, and inter- and intra-person reliability was evaluated by the intraclass correlation coefficient (ICC).
Results:
A larger population (approximately 10% higher) of RGCs are labeled with RBPMS than Brn3a antibody up to 6 months of age, but differences decrease to approximately 1% at older ages. Both RGC-labeled populations significantly decrease with age. MB-induced IOP elevation is associated with a significant decrease of both Brn3a- and RBPMS-positive RGCs. Notably, RGC labeling with Brn3a provides more consistent cell counts than RBPMS in interpersonal (ICC = 0.87 to 0.11, respectively) and intra-personal reliability (ICC = 0.97 to 0.66, respectively).
Conclusions:
Brn3a and RBPMS markers are independently capable of detecting significant decreases of RGC number with age and in response to IOP elevation despite RPBMS detecting a larger number of RGCs up to 6 months of age. Brn3a labeling is less prone to manual cell counting variability than RBPMS labeling. Overall, either marker can be used as a single marker to detect significant changes in RGC survival, each offering distinct advantages.
... 1× AMP cells given by IV administration (N = 7), and 3× AMP cell treatments given by IP (N = 6) or IV (N = 9) injection all showed a significant (***p < 0.001) attenuation of EAE clinical scores as compared with vehicle-treated EAE mice, whereas 1× treatment with AMP cells by IP injection (N = 6) did not significantly reduce EAE scores. Data represent mean ± SEM and MS optic neuritis [34][35][36][37][38]. To evaluate inflammation in the optic nerve, control, EAE, and AMP cell-treated mice were sacrificed on day 42 p.i. 5 μM longitudinal optic nerve sections were stained with H&E and IBA1 (Fig. 3a, b). ...
The human amnion has been used for decades in wound healing, particularly burns. Amnion epithelial cells (AECs) have been the focus of extensive research based on their possible pluripotent differentiation ability. A novel, cultured cell population derived from AECs, termed human amnion–derived multipotent progenitor (AMP) cells, secrete numerous cytokines and growth factors that enhance tissue regeneration and reduce inflammation. This AMP cell secretome, termed ST266, is a unique biological solution that accumulates in eyes and optic nerves following intranasal delivery, resulting in selective suppression of optic neuritis in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis, but not myelitis at the administered dose. We tested the hypothesis that systemic AMP cell administration could suppress both optic neuritis and myelitis in EAE. Intravenous and intraperitoneal administration of AMP cells significantly reduced ascending paralysis and attenuated visual dysfunction in EAE mice. AMP cell treatment increased retinal ganglion cell (RGC) survival and decreased optic nerve inflammation, with variable improvement in optic nerve demyelination and spinal cord inflammation and demyelination. Results show systemic AMP cell administration inhibits RGC loss and visual dysfunction similar to previously demonstrated effects of intranasally delivered ST266. Importantly, AMP cells also promote neuroprotective effects in EAE spinal cords, marked by reduced paralysis. Protective effects of systemically administered AMP cells suggest they may serve as a potential novel treatment for multiple sclerosis.
... The most known preclinical model of MS is the Experimental Autoimmune Encephalomyelitis (EAE) that is induced through injection of myelin oligodendrocyte glycoprotein peptides (MOG ). 5 Immunized C57BL/6 mice develop a chronic disease in which motor disability onset is generally around 14 dpi and ON is often detected. 6 It has been reported that in the optic nerve, where the volume to surface ratio of myelin is quite low, MOG expression is increased compared to other proteins such as proteolipid protein (PLP), which is concentrated on the compact myelin. 7 Functional damage of the anterior visual system can be detected with Visual Evoked Potential (VEP) and Electroretinogram (ERG), while Optical Coherence Tomography (OCT) is used to evaluate structural retinal alterations. ...
Background
Experimental autoimmune encephalomyelitis (EAE) is a common animal model of multiple sclerosis (MS). C57BL/6 mice immunized with myelin oligodendrocyte glycoprotein exhibit chronic disease course, together with optic neuritis, consisting of demyelination/axonal loss of the optic nerve.
Objectives
To characterize functional and structural visual damages in two different phases of EAE: pre- and post-motor onset.
Methods
Visual alterations were detected with Visual Evoked Potential (VEP), Electroretinogram (ERG) and Optical Coherence Tomography (OCT). Optic nerve histology was performed at 7 (pre-motor onset) or 37 (post-motor onset) days post-immunization (dpi).
Results
At 7 dpi, optic nerve inflammation was similar in EAE eyes with and without VEP latency delay. Demyelination was detected in EAE eyes with latency delay (p < 0.0001), while axonal loss (p < 0.0001) and ERG b-wave amplitude (p = 0.004) were decreased in EAE eyes without latency delay compared to Healthy controls. At 37 dpi, functional and structural optic nerve damage were comparable between EAE groups, while a decrease of ERG amplitude and NGCC thickness were found in EAE eyes with VEP latency delay detected post-motor onset.
Conclusions
Thanks to non-invasive methods, we studied the visual system in a MS model, which could be useful for developing specific therapeutic strategies to target different disease phases.
... The diverse phenotypes that the T cells can possess suggest a specialization for target pathogens. Of interest, CD4+ T cells and Th17 T cells can manifest pro-inflammatory functions in a number of neurological disorders including MS [30,66], optic neuritis [67,68], and PD [69,70]. ...
Parkinson's disease (PD) devastates 6.3 million people, ranking it as one of the most prevalent neurodegenerative motor disorders worldwide. PD patients may manifest symptoms of postural instability, bradykinesia, and resting tremors as a result of increasing α-synuclein aggregation and neuron death with disease progression. Therapy options are limited, and those available to patients may worsen their condition. Thus, investigations to understand disease progression may help develop therapeutic strategies for improvement of quality of life for patients suffering from PD. This review provides an overview of α-synuclein, a presynaptic neuronal protein whose function in the healthy brain and PD pathology remains a mystery. This review also focuses on calcium-induced activation of calpain, a neutral protease, and the subsequent cascade of cellular processing of α-synuclein and emerging defense responses observed in experimental models of PD: microglial activation, dysregulation of T cells, and inflammatory responses in the brain. In addition, this review discusses the events of cross presentation of synuclein peptides by professional antigen presenting cells and microglia, induction of inflammatory responses in the periphery and brain, and emerging calpain-targeted therapeutic strategies to attenuate neuronal death in PD.
Retinal ganglion cell (RGC) death in glaucoma and other optic neuropathies results in irreversible vision loss due to the mammalian central nervous system’s limited regenerative capacity. RGC repopulation is a promising therapeutic approach to reverse vision loss from optic neuropathies if the newly introduced neurons can reestablish functional retinal and thalamic circuits. In theory, RGCs might be repopulated through the transplantation of stem cell-derived neurons or via the induction of endogenous transdifferentiation. The RGC Repopulation, Stem Cell Transplantation, and Optic Nerve Regeneration (RReSTORe) Consortium was established to address the challenges associated with the therapeutic repair of the visual pathway in optic neuropathy. In 2022, the RReSTORe Consortium initiated ongoing international collaborative discussions to advance the RGC repopulation field and has identified five critical areas of focus: (1) RGC development and differentiation, (2) Transplantation methods and models, (3) RGC survival, maturation, and host interactions, (4) Inner retinal wiring, and (5) Eye-to-brain connectivity. Here, we discuss the most pertinent questions and challenges that exist on the path to clinical translation and suggest experimental directions to propel this work going forward. Using these five subtopic discussion groups (SDGs) as a framework, we suggest multidisciplinary approaches to restore the diseased visual pathway by leveraging groundbreaking insights from developmental neuroscience, stem cell biology, molecular biology, optical imaging, animal models of optic neuropathy, immunology & immunotolerance, neuropathology & neuroprotection, materials science & biomedical engineering, and regenerative neuroscience. While significant hurdles remain, the RReSTORe Consortium’s efforts provide a comprehensive roadmap for advancing the RGC repopulation field and hold potential for transformative progress in restoring vision in patients suffering from optic neuropathies.
Acquired demyelinating syndromes of the central nervous system are immune-mediated demyelinating disorders that can affect the brain, optic nerves, and spinal cord. These disorders have become increasingly recognized in children due to advances in imaging techniques, improvements in diagnostic testing, extensive research into understanding the pathophysiology underlying these disorders, and collaborative multi-institutional efforts to raise awareness of these disorders in children. Moreover, developments in the field of neuroimmunology have allowed us to identify autoantibodies that have presumed causal roles in acquired demyelinating syndromes. Identification of these autoantibodies helps determine clinical course (ie, monophasic vs relapsing course), prognosis, and treatment approach. Acquired demyelinating disorders can affect both children and adults. However, the clinical features, disease course, and treatments are often unique in the pediatric population. Thus, it is important to understand the spectrum of these disorders in children to help provide a timely diagnosis and prompt treatment to achieve optimal outcomes. In this article, the epidemiology, clinical features, diagnosis, treatment, and outcomes of the most common monophasic acquired demyelinating syndromes in children will be reviewed.
Background:
Numerous disorders affecting the optic nerve require histological examination of whole length optic nerves and chiasm. Most methods employed to study the histopathology of the optic nerves in animal models of human diseases involve resection of a short retrobulbar section after eye globe exenteration, commonly obtained in mice. This approach might affect the morphology of the optic nerve, thus limiting accurate identification of pathological changes in the tissue. Some histological studies were performed on longer or more posterior parts of the anterior visual pathway included the chiasm. However, an accurate replicable protocol for such whole length (eye globe to chiasm) dissection is not currently unavailable in published literature.
New method:
Here we describe a protocol for dissecting the whole length of the optic nerves and chiasm through a craniotomy incision.
Results:
We describe in detail the stages necessary for exposing the optic nerves, the chiasm and the optic tracts, and for detaching them with minimal traction.
Comparison with existing method:
The existing replicable method provide only a sample of the retrobulbar optic nerve and the sample might be affected by traction. Our protocol provides a whole length specimen of the optic nerve and chiasm without concern of traction artifacts.
Conclusions:
We present a simple and straightforward approach to isolate the complete anterior visual pathway in the mouse for histopathological evaluation.
Using the paired patch-clamp technique, we studied the effects of short-term hypoxia on retinocollicular synaptic transmission in an originally-developed coculture of dissociated retinal cells and superficial superior colliculus (SSC) neurons. Pharmacologically isolated N-methyl-D-aspartate receptor (NMDA)− α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA)− and gamma-aminobutyric acid receptor (GABAA)−mediated postsynaptic currents (PSCs) were evoked in SSC neurons by generation action potentials in presynaptic retinal ganglion cells. Spontaneous and miniature PSCs were recorded in SSC neurons in the absence of presynaptic stimulation. Short-term (up to 5 min) hypoxia induced long-term potentiation of NMDA transmission, long-term depression of GABAA neurotransmission and temporary suppression of AMPA transmission. Also, we observed hypoxia-induced reduction of voltage-dependent magnesium blockade of evoked NMDA response. Evoked, spontaneous and miniature postsynaptic currents were analyzed in terms of a binomial model. This analysis revealed that hypoxia acts mainly presynaptically on excitatory neurotransmission and both pre‒ and postsynaptically on inhibitory retinocollicular transmission. Thus, we showed for the first time hypoxia-induced bidirectional long-term plasticity of the retinocollicular synaptic transmission. The results obtained reflect the electrophysiological basis of hypoxia-involved pathological lesion of the retinocollicular pathway.
Objective: We examined a cohort of adults with aquaporin-4 (AQP4) antibody–negative neuromyelitis optica/neuromyelitis optica spectrum disorder (NMO/NMOSD) for antibodies to myelin oligodendrocyte glycoprotein (MOG). Methods: We performed a flow cytometry cell-based assay using live human lentivirus–transduced cells expressing full-length surface MOG. Serum was tested in 23 AQP4 antibody–negative NMO/NMOSD patients with bilateral and/or recurrent optic neuritis (BON, n = 11), longitudinally extensive transverse myelitis (LETM, n = 10), and sequential BON and LETM (n = 2), as well as in patients with multiple sclerosis (MS, n = 76) and controls (n = 52). Results: MOG antibodies were detected in 9/23 AQP4 antibody–negative patients with NMO/NMOSD, compared to 1/76 patients with MS and 0/52 controls (p < 0.001). MOG antibodies were detected in 8/11 patients with BON, 0/10 patients with LETM, and 1/2 patients with sequential BON and LETM. Six of 9 MOG antibody–positive patients had a relapsing course. MOG antibody–positive patients had prominent optic disc swelling and were more likely to have a rapid response to steroid therapy and relapse on steroid cessation than MOG antibody–negative patients (p = 0.034 and p = 0.029, respectively). While 8/9 MOG antibody–positive patients had good follow-up visual acuity, one experienced sustained visual impairment, 3 had retinal nerve fiber layer thinning, and one had residual spinal disability.
Reports that chronically demyelinated multiple sclerosis brain and spinal cord lesions contained immature oligodendrocyte lineage cells have generated major interest aimed at the potential for promotion of endogenous repair. Despite the prominence of the optic nerve as a lesion site and its importance in clinical disease assessment, no detailed studies of multiple sclerosis-affected optic nerve exist. This study aims to provide insight into the cellular pathology of chronic demyelination in multiple sclerosis through direct morphological and immunohistochemical analysis of optic nerve in conjunction with observations from an experimental cat optic nerve model of successful remyelination. Myelin staining was followed by immunohistochemistry to differentially label neuroglia. Digitally immortalised sections were then analysed to generate quantification data and antigenic phenotypes including maturational stages within the oligodendrocyte lineage. It was found that some chronically demyelinated multiple sclerosis optic nerve lesions contained oligodendroglial cells and that heterogeneity existed in the presence of myelin sheaths, oligodendrocyte maturational stages and extent of axonal investment. The findings advance our understanding of oligodendrocyte activity in chronic demyelinated human optic nerve and may have implications for studies aimed at enhancement of endogenous repair in multiple sclerosis.
The recognition of multiple ligands by a single TCR is an intrinsic feature of T cell biology, with important consequences for physiological and pathological processes. Polyspecific T cells targeting distinct self-antigens have been identified in healthy individuals as well as in the context of autoimmunity. We have previously shown that the 2D2 TCR recognizes the myelin oligodendrocyte glycoprotein epitope (MOG)35-55 as well as an epitope within the axonal protein neurofilament medium (NF-M15-35) in H-2(b) mice. In this study, we assess whether this cross-reactivity is a common feature of the MOG35-55-specific T cell response. To this end, we analyzed the CD4 T cell response of MOG35-55-immunized C57BL/6 mice for cross-reactivity with NF-M15-35. Using Ag recall responses, we established that an important proportion of MOG35-55-specific CD4 T cells also responded to NF-M15-35 in all mice tested. To study the clonality of this response, we analyzed 22 MOG35-55-specific T cell hybridomas expressing distinct TCR. Seven hybridomas were found to cross-react with NF-M15-35. Using an alanine scan of NF-M18-30 and an in silico predictive model, we dissected the molecular basis of cross-reactivity between MOG35-55 and NF-M15-35. We established that NF-M F24, R26, and V27 proved important TCR contacts. Strikingly, the identified TCR contacts are conserved within MOG38-50. Our data indicate that due to linear sequence homology, part of the MOG35-55-specific T cell repertoire of all C57BL/6 mice also recognizes NF-M15-35, with potential implications for CNS autoimmunity.
Background
One of the most common causes of meningitis in South East Asia is angiostrongyliasis or infection by the parasitic nematode Angiostrongyliasis cantonensis. Although this nematode usually resides in the pulmonary arteries of rats, its incidental occurence in other hosts such as humans can cause optic neuritis and lead to serious vision sequelae. Nevertheless, there are currently no systematic studies conducted in this area.
Methods
In order to study the pathogenesis of optic neuritis, mice were tried as a new animal model to study and challenge with A. cantonensis on 7d, 14d and 21d, respectively. Electroretinogram (ERG), visual evoked potential (VEP), ophthalmoscopy and histology were examined on day 7d, 14d and 21d and tribendimidine (TBD) was later used to treat optic neuritis on day 14d for a week to evaluate its therapeutic effects.
Results
Infection of A. cantonensis caused obvious inflammatory cell infiltration in the retina and optic nerve adventitia in day 14d and 21d followed by optic nerve fiber demyelination and retinal ganglion swelling at day 21d in the challenged mice. Prolonged VEP latency and decreased ERG amplitude were also observed on day 21. After treatment of TBD in the infected mice, retinal and optic nerve inflammation were alleviated, but VEP latency and ERG amplitude did not improve on day 21d and 28d.
Conclusions
The current study provides evidence that A. cantonensis can cause optic neuritis along with optic nerve demyelination and retinal ganglion cell damage in a mouse model. TBD alone treatment can improve the symptoms of optic neuritis, but does not aid in vision recovery, suggesting that both neuroprotective agents and Dexamethasone should be administered, along with treatment for the infection, to protect the optic nerve and ganglion cells. Furthermore, as the symptoms of optic neuritis caused by A. cantonensis in mice are similar to the optic neuritis in multiple sclerosis (MS) human patients, we suggest that the BALB/c mouse model provided in this study may be useful to explore therapies of optic neuritis in MS patients.
Optic neuritis is an inflammatory optic neuropathy that affects many patients with multiple sclerosis (MS) at some point during their disease course. Differentiation of acute episodes of MS-associated optic neuritis from other autoimmune and inflammatory optic neuropathies is vital for treatment choice and further patient management, but is not always straightforward. Over the past decade, a number of new imaging, laboratory and electrophysiological techniques have entered the clinical arena. To date, however, no consensus guidelines have been devised to specify how and when these techniques can be most rationally applied for the diagnostic work-up of patients with acute optic neuritis. In this article, we review the literature and attempt to formulate a consensus for the investigation of patients with acute optic neuritis, both in standard care and in research with relevance to clinical treatment trials.
Neurodegeneration plays an important role in permanent disability in multiple sclerosis (MS).
The objective of this paper is to determine whether progressive neurodegeneration occurs in MS eyes without clinically evident inflammation.
Retinal nerve fiver layer thickness (RNFLT) and ganglion cell-inner plexiform layer thickness (GCIPT) were measured using Cirrus optical coherence tomography (OCT) in 133 relapsing-remitting MS (RRMS) patients (149 non-optic neuritis (ON), 97 ON eyes, last ON ≥6 months). Ninety-three patients were scanned at two visits. Percentages of abnormal GCIPT vs RNFLT (<5% of machine norms) in cross-sectional data were compared. Relations between RNFLT/GCIPT and MS duration (cross-sectional) and follow-up time (longitudinal) were assessed.
GCIPT was abnormal in more eyes than RNFLT (27% vs 16% p = 0.004 in non-ON, 82% vs 72% p = 0.007 in ON). RNFLT and GCIPT decreased with MS duration by -0.49 µm/yr (p = 0.0001) and -0.36 (p = 0.005) for non-ON; -0.52 (p = 0.003) and -0.41 (p = 0.007) for ON. RNFLT and GCIPT decreased with follow-up time by -1.49 µm/yr (p < 0.0001) and -0.53 (p = 0.004) for non-ON, -1.27 (p = 0.002) and -0.49 (p = 0.04) for ON.
In RRMS eyes without clinically evident inflammation, progressive loss of RNFLT and GCIPT occurred, supporting the need for neuroprotection in addition to suppression of autoimmune responses and inflammation.
Although optic neuritis (ON) is a defining feature of neuromyelitis optica (NMO), appropriate animal models of NMO ON are lacking. Most NMO patients are seropositive for immunoglobulin G autoantibodies (NMO-IgG) against the astrocyte water channel aquaporin-4 (AQP4).
Several approaches were tested to develop a robust, passive-transfer mouse model of NMO ON, including NMO-IgG and complement delivery by: (i) retrobulbar infusion; (ii) intravitreal injection; (iii) a single intracranial injection near the optic chiasm; and (iv) 3-days continuous intracranial infusion near the optic chiasm.
Little ON or retinal pathology was seen using approaches (i) to (iii). Using approach (iv), however, optic nerves showed characteristic NMO pathology, with loss of AQP4 and glial fibrillary acidic protein immunoreactivity, granulocyte and macrophage infiltration, deposition of activated complement, demyelination and axonal injury. Even more extensive pathology was created in mice lacking complement inhibitor protein CD59, or using a genetically modified NMO-IgG with enhanced complement effector function, including significant loss of retinal ganglion cells. In control studies, optic nerve pathology was absent in treated AQP4-deficient mice, or in wild-type mice receiving control (non-NMO) IgG and complement.
Passive transfer of NMO-IgG and complement by continuous infusion near the optic chiasm in mice is sufficient to produce ON with characteristic NMO pathology. The mouse model of NMO ON should be useful in further studies of NMO pathogenesis mechanisms and therapeutics.
The anatomic location of subsequent relapses in early multiple sclerosis (MS) appears to be predicted by the first attack location. We sought to determine if genetic polymorphisms associated with MS susceptibility are associated with attack location.
17 genome-wide association study-identified MS susceptibility polymorphisms were genotyped in 503 white, non-Hispanic patients seen within a year of MS onset. Their association with the CNS location of the first two MS attacks was assessed in multivariate repeated measures analyses (generalized estimating equations with robust standard errors).
The IL12A polymorphism was independently associated with increased odds of attacks involving the spinal cord (OR = 1.52, 95% CI 1.11, 2.07, p = 0.009), as was the IRF8 polymorphism (OR = 2.40, 95% CI [1.04, 5.50], p = 0.040). The IL7R polymorphism was associated with reduced odds of attacks involving the brainstem/cerebellum (OR = 0.46, 95% CI 0.22, 0.97, p = 0.041), as were the TNFRSF1A and IL12A polymorphisms. The CD6 polymorphism conferred reduced odds of optic neuritis as an attack location (OR = 0.69, 95% CI [0.49, 0.97], p = 0.034). Several other genes showed trends for association with attack location.
Some of the MS susceptibility genes may be associated with MS attack location. The IL12A polymorphism is of particular interest given that interferon beta therapy appears to influence IL12 levels. These findings may lead to improved understanding of MS pathogenesis and treatment.
Abstract Optical neuritis (ON) is characterized by inflammation of the optic nerve, and is one of the first clinical signs of multiple sclerosis (MS). Experimental autoimmune encephalomyelitis (EAE) is the animal model used to study MS and ON. The present study evaluated the induction, development and progression of ON using an EAE model induced by 100 μg or 300 μg of MOG35-55. An EAE model was induced in C57BL/6 mice by tail base injection of 100 μg or 300 μg of MOG35-55 in complete Freund's adjuvant, supplemented with Mycobacterium tuberculosis. On the day of injection and 48 h later, animals received intraperitoneally 300 ng of pertussis toxin. On days 7, 10, 14, 21 and 58 the optic nerve was dissected for histological analysis, production of CCL5 and immunohistochemical detection of CD4 and CD8. The histological changes observed in the optic nerves consisted of inflammatory cell infiltrates showing varying degrees of ON in the two groups. The onset of ON in the 300 μg of MOG35-55 group was coincident with higher production of CCL5, on day 10 after induction. However, the 100 μg MOG35-55 group showed more intense inflammatory infiltrate on day 14 after induction, with higher amounts of CD4 and CD8, reaching an excessive demyelination process on days 21 and 58 after induction. The results suggest that two different concentrations of MOG35-55 lead to different forms of evolution of optic neuritis.
A 27-year-old Thai male presented with progressive visual loss and a membrane-like floater in the right eye that had persisted for 1 month. He had a history of eating raw foods, including snails. His initial visual acuity was counting fingers at 1 ft and he had a relative afferent pupillary defect. A movable larva with subretinal tracks was found in the subretinal space near a normal optic disc. Visually evoked potentials showed delayed latency, which indicated secondary retrobulbar optic neuritis. A diode laser was directly applied to the motile worm. The patient was subsequently prescribed oral prednisolone and albendazole. After treatment, his visual acuity was slightly improved at 2/60. Ocular manifestation is a very rare event resulting from parasitic infection. In only 1.1% of angiostrongyliasis cases is an Angiostrongylus cantonensis larva identified in the eye. Ocular angiostrongyliasis with optic neuritis may be secondary to mechanical injury and/or inflammatory reactions. Steroid treatment is recommended, although most patients have only slight visual improvement after treatment.
Purpose:
To determine if phosphorylated neurofilament heavy chain (pNF-H) released into the bloodstream and the pattern ERG are noninvasive indicators of neurodegeneration in experimental optic neuritis.
Methods:
Serum from Myelin oligodendrocyte glycoprotein (MOG)-specific T cell receptor-positive (TCR+) transgenic mice that develop isolated optic neuritis usually without any other characteristic lesions of inflammation or demyelination in the spinal cord and littermates negative for the transgene were assayed for the presence of serum phosphorylated neurofilament H (pNF-H). In vivo measurements of optic nerve and retinal ganglion cell injury were assessed by magnetic resonance imaging (MRI), optical coherence tomography (OCT), and pattern electroretinogram (PERG). Automated two dimensional fluorescence differential in-gel electrophoresis (2D-DIGE) of pooled optic nerve samples, light, and transmission electron micrographs were used to evaluate optic atrophy postmortem.
Results:
We found an almost 3-fold elevation in serum pNF-H levels in MOG+ mice relative to MOG-littermates (P = 0.02). 2D-DIGE revealed a 3-fold reduction in optic nerve neurofilaments. Visual function assessed by the PERG was reduced by one-quarter (P = 0.033) and latencies increased by 38% (P = 0.036). MOG+ mice with the lowest PERG amplitudes had optic nerve atrophy visualized by MRI. Optic nerve diameters were reduced by one-third (P = 0.0001) and axon counts reduced by more than two-thirds. Histopathology of the spinal cords was normal.
Conclusions:
Elevated serum pNF-H levels and the PERG are useful markers of neurodegeneration of the optic nerve in isolated experimental optic neuritis. Our findings suggest that elevations of this axonal protein in patients with optic neuritis who had a poor visual outcome are likely also due to demise of optic nerve axons.
Reactive astrocytes are typically studied in models that cause irreversible mechanical damage to axons, neuronal cell bodies, and glia. Here, we evaluated the response of astrocytes in the optic nerve head to a subtle injury induced by a brief, mild elevation of the intraocular pressure. Astrocytes demonstrated reactive remodeling that peaked at three days, showing hypertrophy, process retraction, and simplification of their shape. This was not accompanied by any significant changes in the gene expression profile. At no time was there discernible damage to the optic axons, as evidenced by electron microscopy and normal anterograde and retrograde transport. Remarkably, the morphological remodeling was reversible. These findings underscore the plastic nature of reactivity. They show that reactivity can resolve fully if the insult is removed, and suggest that reactivity per se is not necessarily deleterious to axons. This reaction may represent very early events in the sequence that eventually leads to glial scarring.
Background
Optic neuritis is an acute, demyelinating neuropathy of the optic nerve often representing the first appreciable symptom of multiple sclerosis. Wallerian degeneration of irreversibly damaged optic nerve axons leads to death of retinal ganglion cells, which is the cause of permanent visual impairment. Although the specific mechanisms responsible for triggering these events are unknown, it has been suggested that a key pathological factor is the activation of immune-inflammatory processes secondary to leukocyte infiltration. However, to date, there is no conclusive evidence to support such a causal role for infiltrating peripheral immune cells in the etiopathology of optic neuritis.
Methods
To dissect the contribution of the peripheral immune-inflammatory response versus the CNS-specific inflammatory response in the development of optic neuritis, we analyzed optic nerve and retinal ganglion cells pathology in wild-type and GFAP-IκBα-dn transgenic mice, where NF-κB is selectively inactivated in astrocytes, following induction of EAE.
Results
We found that, in wild-type mice, axonal demyelination in the optic nerve occurred as early as 8 days post induction of EAE, prior to the earliest signs of leukocyte infiltration (20 days post induction). On the contrary, GFAP-IκBα-dn mice were significantly protected and showed a nearly complete prevention of axonal demyelination, as well as a drastic attenuation in retinal ganglion cell death. This correlated with a decrease in the expression of pro-inflammatory cytokines, chemokines, adhesion molecules, as well as a prevention of NAD(P)H oxidase subunit upregulation.
Conclusions
Our results provide evidence that astrocytes, not infiltrating immune cells, play a key role in the development of optic neuritis and that astrocyte-mediated neurotoxicity is dependent on activation of a transcriptional program regulated by NF-κB. Hence, interventions targeting the NF-κB transcription factor in astroglia may be of therapeutic value in the treatment of optic neuritis associated with multiple sclerosis.
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).
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.
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.
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.
Serum autoantibodies against the water channel aquaporin-4 (AQP4) are important diagnostic biomarkers and pathogenic factors for neuromyelitis optica (NMO). However, AQP4-IgG are absent in 5-40% of all NMO patients and the target of the autoimmune response in these patients is unknown. Since recent studies indicate that autoimmune responses to myelin oligodendrocyte glycoprotein (MOG) can induce an NMO-like disease in experimental animal models, we speculate that MOG might be an autoantigen in AQP4-IgG seronegative NMO. Although high-titer autoantibodies to human native MOG were mainly detected in a subgroup of pediatric acute disseminated encephalomyelitis (ADEM) and multiple sclerosis (MS) patients, their role in NMO and High-risk NMO (HR-NMO; recurrent optic neuritis-rON or longitudinally extensive transverse myelitis-LETM) remains unresolved.
We analyzed patients with definite NMO (n = 45), HR-NMO (n = 53), ADEM (n = 33), clinically isolated syndromes presenting with myelitis or optic neuritis (CIS, n = 32), MS (n = 71) and controls (n = 101; 24 other neurological diseases-OND, 27 systemic lupus erythematosus-SLE and 50 healthy subjects) for serum IgG to MOG and AQP4. Furthermore, we investigated whether these antibodies can mediate complement dependent cytotoxicity (CDC). AQP4-IgG was found in patients with NMO (n = 43, 96%), HR-NMO (n = 32, 60%) and in one CIS patient (3%), but was absent in ADEM, MS and controls. High-titer MOG-IgG was found in patients with ADEM (n = 14, 42%), NMO (n = 3, 7%), HR-NMO (n = 7, 13%, 5 rON and 2 LETM), CIS (n = 2, 6%), MS (n = 2, 3%) and controls (n = 3, 3%, two SLE and one OND). Two of the three MOG-IgG positive NMO patients and all seven MOG-IgG positive HR-NMO patients were negative for AQP4-IgG. Thus, MOG-IgG were found in both AQP4-IgG seronegative NMO patients and seven of 21 (33%) AQP4-IgG negative HR-NMO patients. Antibodies to MOG and AQP4 were predominantly of the IgG1 subtype, and were able to mediate CDC at high-titer levels.
We could show for the first time that a subset of AQP4-IgG seronegative patients with NMO and HR-NMO exhibit a MOG-IgG mediated immune response, whereas MOG is not a target antigen in cases with an AQP4-directed humoral immune response.
Multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) are neurodegenerative diseases with characteristic inflammatory demyelination in the central nervous system, including the optic nerve. Neuronal and axonal damage is considered to be the main cause of long-term disability in patients with MS. Neuronal loss, including retinal ganglion cell (RGC) apoptosis in eyes with optic neuritis (ON), also occurs in EAE. However, there is significant variability in the clinical course and level of neuronal damage in MS and EAE. The current studies examine the mechanisms and kinetics of RGC loss in C57/BL6 mice immunized with myelin oligodendrocyte glycoprotein to induce a chronic EAE disease. Clinical progression of EAE was scored daily and vision was assessed by optokinetic responses. At various time points, RGCs were counted and optic nerves were examined for inflammatory cell infiltration. Almost all EAE mice develop ON by day 15 post-immunization; however, RGC loss is delayed in these mice. No RGC loss is detected 25 days post-immunization, whereas RGC numbers in EAE mice significantly and progressively decrease compared to controls from 35 to 50 days post-immunization. The delayed time course of RGC loss is in stark contrast to that reported in relapsing EAE, as well as in rats with chronic EAE. Results suggest that different clinical disease courses of optic nerve inflammation may trigger distinct mechanisms of neuronal damage, or RGCs in different rodent strains may have variable resistance to neuronal degeneration.
Genome-wide association (GWA) studies have identified numerous, replicable, genetic associations between common single nucleotide polymorphisms (SNPs) and risk of common autoimmune and inflammatory (immune-mediated) diseases, some of which are shared between two diseases. Along with epidemiological and clinical evidence, this suggests that some genetic risk factors may be shared across diseases-as is the case with alleles in the Major Histocompatibility Locus. In this work we evaluate the extent of this sharing for 107 immune disease-risk SNPs in seven diseases: celiac disease, Crohn's disease, multiple sclerosis, psoriasis, rheumatoid arthritis, systemic lupus erythematosus, and type 1 diabetes. We have developed a novel statistic for Cross Phenotype Meta-Analysis (CPMA) which detects association of a SNP to multiple, but not necessarily all, phenotypes. With it, we find evidence that 47/107 (44%) immune-mediated disease risk SNPs are associated to multiple-but not all-immune-mediated diseases (SNP-wise P(CPMA)<0.01). We also show that distinct groups of interacting proteins are encoded near SNPs which predispose to the same subsets of diseases; we propose these as the mechanistic basis of shared disease risk. We are thus able to leverage genetic data across diseases to construct biological hypotheses about the underlying mechanism of pathogenesis.
CD8 T cells are emerging as important players in multiple sclerosis (MS) pathogenesis, although their direct contribution to tissue damage is still debated. To assess whether autoreactive CD8 T cells can contribute to the pronounced loss of oligodendrocytes observed in MS plaques, we generated mice in which the model Ag influenza hemagglutinin is selectively expressed in oligodendrocytes. Transfer of preactivated hemagglutinin-specific CD8 T cells led to inflammatory lesions in the optic nerve, spinal cord, and brain. These lesions, associating CD8 T cell infiltration with focal loss of oligodendrocytes, demyelination, and microglia activation, were very reminiscent of active MS lesions. Thus, our study demonstrates the potential of CD8 T cells to induce oligodendrocyte lysis in vivo as a likely consequence of direct Ag-recognition. These results provide new insights with regard to CNS tissue damage mediated by CD8 T cells and for understanding the role of CD8 T cells in MS.
Glutamate excitotoxicity mediated by the AMPA/kainate type of glutamate receptors damages not only neurons but also the myelin-producing cell of the central nervous system, the oligodendrocyte. In multiple sclerosis, myelin, oligodendrocytes and some axons are lost as a result of an inflammatory attack on the central nervous system. Because glutamate is released in large quantities by activated immune cells, we expected that during inflammation in MS, glutamate excitotoxicity might contribute to the lesion. We addressed this by using the AMPA/kainate antagonist NBQX to treat mice sensitized for experimental autoimmune encephalomyelitis, a demyelinating model that mimics many of the clinical and pathologic features of multiple sclerosis. Treatment resulted in substantial amelioration of disease, increased oligodendrocyte survival and reduced dephosphorylation of neurofilament H, an indicator of axonal damage. Despite the clinical differences, treatment with NBQX had no effect on lesion size and did not reduce the degree of central nervous system inflammation. In addition, NBQX did not alter the proliferative activity of antigen-primed T cells in vitro, further indicating a lack of effect on the immune system. Thus, glutamate excitotoxicity seems to be an important mechanism in autoimmune demyelination, and its prevention with AMPA/kainate antagonists may prove to be an effective therapy for multiple sclerosis.
Multiple sclerosis is a chronic inflammatory disease of the central nervous system, associated with demyelination and neurodegeneration. The mechanisms of tissue injury are currently poorly understood, but recent data suggest that mitochondrial injury may play an important role in this process. Since mitochondrial injury can be triggered by reactive oxygen and nitric oxide species, we analysed by immunocytochemistry the presence and cellular location of oxidized lipids and oxidized DNA in lesions and in normal-appearing white matter of 30 patients with multiple sclerosis and 24 control patients without neurological disease or brain lesions. As reported before in biochemical studies, oxidized lipids and DNA were highly enriched in active multiple sclerosis plaques, predominantly in areas that are defined as initial or 'prephagocytic' lesions. Oxidized DNA was mainly seen in oligodendrocyte nuclei, which in part showed signs of apoptosis. In addition, a small number of reactive astrocytes revealed nuclear expression of 8-hydroxy-d-guanosine. Similarly, lipid peroxidation-derived structures (malondialdehyde and oxidized phospholipid epitopes) were seen in the cytoplasm of oligodendrocytes and some astrocytes. In addition, oxidized phospholipids were massively accumulated in a fraction of axonal spheroids with disturbed fast axonal transport as well as in neurons within grey matter lesions. Neurons stained for oxidized phospholipids frequently revealed signs of degeneration with fragmentation of their dendritic processes. The extent of lipid and DNA oxidation correlated significantly with inflammation, determined by the number of CD3 positive T cells and human leucocyte antigen-D expressing macrophages and microglia in the lesions. Our data suggest profound oxidative injury of oligodendrocytes and neurons to be associated with active demyelination and axonal or neuronal injury in multiple sclerosis.
The aim of this study is to provide a clinical update on optic neuritis (ON), its association with multiple sclerosis (MS), and neuromyelitis optica (NMO).
This study included a PubMed review of the literature written in the English language.
ON in adults is typically idiopathic or demyelinating, and is characterised by unilateral, subacute, painful loss of vision that is not associated with any systemic or other neurological symptoms. Demyelinating ON is associated with MS, and we review the key studies of ON including the ON treatment trial and several other MS treatment trials and NMO.
Acute demyelinating ON can occur in isolation or be associated with MS. Typical ON does not require additional evaluation other than cranial magnetic resonance imaging. NMO is likely a separate disorder from MS and the ON in NMO has a different treatment and prognosis.
The authors conducted an English language search using Pubmed from the years 1964 to 2010 using the search terms 'ON', 'MS' and 'NMO'. The authors included original articles, review articles, and case reports, which revealed new aspects as far as epidemiology, histopathology, clinical manifestations, imaging, genetics, and treatment of ON. Titles were reviewed for topicality and full references were obtained. Letters to the editor, unpublished work, and abstracts were not included in this review.
The myelination of axons by glial cells was the last major step in the evolution of cells in the vertebrate nervous system, and white-matter tracts are key to the architecture of the mammalian brain. Cell biology and mouse genetics have provided insight into axon-glia signalling and the molecular architecture of the myelin sheath. Glial cells that myelinate axons were found to have a dual role by also supporting the long-term integrity of those axons. This function may be independent of myelin itself. Myelin abnormalities cause a number of neurological diseases, and may also contribute to complex neuropsychiatric disorders.
The CNS is an immune-privileged environment, yet the local control of multiple pathogens is dependent on the ability of immune cells to access and operate within this site. However, inflammation of the distinct anatomical sites (i.e., meninges, cerebrospinal fluid, and parenchyma) associated with the CNS can also be deleterious. Therefore, control of lymphocyte entry and migration within the brain is vital to regulate protective and pathological responses. In this review, several recent advances are highlighted that provide new insights into the processes that regulate leukocyte access to, and movement within, the brain.
The objective of our study was to assess the 5-year risk of and prognostic factors for the development of clinically definite multiple sclerosis (CDMS) following optic neuritis. In a prospective cohort study design, 388 patients, who did not have probable or definite MS at study entry enrolled in the Optic Neuritis Treatment Trial between 1988 and 1991, and were followed for the development of CDMS. The 5-year cumulative probability of CDMS was 30% and did not differ by treatment group. Neurologic impairment in the patients who developed CDMS was generally mild. Brain MRI performed at study entry was a strong predictor of CDMS, with the 5-year risk of CDMS ranging from 16% in the 202 patients with no MRI lesions to 51% in the 89 patients with three or more MRI lesions. Independent of brain MRI, the presence of prior nonspecific neurologic symptoms was also predictive of the development of CDMS. Lack of pain, the presence of optic disk swelling, and mild visual acuity loss were features of the optic neuritis associated with a low risk of CDMS among the 189 patients who had no brain MRI lesions and no history of neurologic symptoms or optic neuritis in the fellow eye. The 5-year risk of CDMS following optic neuritis is highly dependent on the number of lesions present on brain MRI. However, even a normal brain MRI does not preclude the development of CDMS. In these patients with no brain MRI lesions, certain clinical features identify a subgroup with a particularly low 5-year risk of CDMS.
Objective:
To assess visual function 15 years after acute unilateral optic neuritis.
Design:
Longitudinal follow-up of a randomized clinical trial.
Participants:
Two hundred ninety-four patients who were randomized in the Optic Neuritis Treatment Trial between 1988 and 1991 and underwent examination in 2006.
Testing:
A neuro-ophthalmic examination included measurements of visual acuity, contrast sensitivity, and visual field. Quality of life was assessed with the National Eye Institute Visual Function Questionnaire and Neuro-ophthalmic Supplement.
Main outcome measures:
Abnormal vision and health-related quality-of-life scores.
Results:
Seventy-two percent of the eyes affected with optic neuritis at study entry had visual acuity of > or = 20/20 and 66% of patients had > or = 20/20 acuity in both eyes. On average, visual function was slightly worse among patients with multiple sclerosis (MS) than among with those without MS. As expected, quality-of-life scores were lower when acuity was reduced and when neurologic disability from MS was present.
Conclusions:
Long-term visual outcome is favorable for the majority of patients who experience optic neuritis even when MS is present.
Over 20 species of Angiostrongylus have been described from around the world, but only Angiostrongylus cantonensis has been confirmed to cause central nervous system disease in humans. A neurotropic parasite that matures in the pulmonary arteries of rats, A. cantonensis is the most common cause of eosinophilic meningitis in southern Asia and the Pacific and Caribbean islands. The parasite can also cause encephalitis/encephalomyelitis and rarely ocular angiostrongyliasis. The present paper reviews the life cycle, epidemiology, pathogenesis, clinical features, diagnosis, treatment, prevention and prognosis of A. cantonesis infection. Emphasis is given on the spectrum of central nervous system manifestations and disease pathogenesis.
Optic neuritis is frequently the first symptom of multiple sclerosis (MS), an inflammatory demyelinating neurodegenerative disease. Impaired axonal transport has been considered as an early event of neurodegenerative diseases. However, few studies have assessed the integrity of axonal transport in MS or its animal models. We hypothesize that axonal transport impairment occurs at the onset of optic neuritis in experimental autoimmune encephalomyelitis (EAE) mice. In this study, we employed manganese-enhanced MRI (MEMRI) to assess axonal transport in optic nerves in EAE mice at the onset of optic neuritis. Axonal transport was assessed as (a) optic nerve Mn(2+) accumulation rate (in % signal change/hour) by measuring the rate of increased total optic nerve signal enhancement, and (b) Mn(2+) transport rate (in mm/hour) by measuring the rate of change in optic nerve length enhanced by Mn(2+). Compared to sham-treated healthy mice, Mn(2+) accumulation rate was significantly decreased by 19% and 38% for EAE mice with moderate and severe optic neuritis, respectively. The axonal transport rate of Mn(2+) was significantly decreased by 43% and 65% for EAE mice with moderate and severe optic neuritis, respectively. The degree of axonal transport deficit correlated with the extent of impaired visual function and diminished microtubule-associated tubulins, as well as the severity of inflammation, demyelination, and axonal injury at the onset of optic neuritis.
Retinal ganglion cell (RGC) axonal structure and function in the optic nerve head (ONH) is predominantly supported by astrocytes and capillaries. There is good experimental evidence to demonstrate that RGC axons are perturbed in a non-uniform manner following ONH injury and it is likely that the pattern of RGC axonal modification bears some correlation with the quantitative properties of astrocytes and capillaries within laminar compartments. Although there have been some excellent topographic studies concerning glial and microvascular networks in the ONH our knowledge regarding the quantitative properties of these structures are limited. This report is an in-depth quantitative, structural analysis of astrocytes and capillaries in the pre laminar, lamina cribrosa and post laminar compartments of the ONH. 49 optic nerves from human (n = 10), pig (n = 12), horse (n = 6), rat (n = 11) and rabbit (n = 10) eyes are studied. Immunohistochemical and high-magnification confocal microscopy techniques are used to co-localise astrocytes, capillaries and nuclei in the mid-portion of the optic nerve. Quantitative methodology is used to determine the area occupied by astrocyte processes, microglia processes, nuclei density and the area occupied by capillaries in each laminar compartment. Comparisons are made within and between species. Relationships between ONH histomorphometry and astrocyte-capillary constitution are also explored. This study demonstrates that there are significant differences in the quantitative properties of capillaries and astrocytes between the laminar compartments of the human ONH. Astrocyte processes occupied the greatest area in the lamina cribrosa compartment of the human ONH implicating it as an area of great metabolic demands. Microglia were found to occupy only a small proportion of tissue in the rat, rabbit and pig optic nerve suggesting that the astrocyte is the predominant glia cell type in the optic nerve. This study also demonstrates that there is significant uniformity, with respect to astrocyte and capillary constitution, in the post laminar region of species with an unmyelinated anterior optic nerve. This implicates an important role served by oligodendrocytes and myelin in governing the structural characteristics of the post laminar optic nerve. Finally, this study demonstrates that eyes with similar lamina cribrosa structure do not necessarily share an identical cellular constitution with respect to astrocytes. The quantitative properties of astrocytes in the pre laminar and lamina cribrosa regions of the rat, which has a rudimentary lamina cribrosa with only a few collagenous beams, shared more similarities to the human eye than the pig or horse. The quantitative properties of astrocytes and capillaries in the laminar compartments of the ONH provide a basis for understanding the pathogenic mechanisms that are involved in diseases such as glaucoma and ischemic optic neuropathy. The findings in this study also provide valuable information about the distinct advantages of different animal models for studying human optic nerve diseases. Utilisation of structural data provided in this report together with emerging in vivo technology may potentially permit the early identification of RGC axonal injury by quantifying changes in ONH capillaries and astrocytes.
To 1) determine, using contemporary recombinant antigen-based assays, the aquaporin-4 (AQP4)-immunoglobulin G (IgG) detection rate in sequential sera of patients assigned a clinical diagnosis of neuromyelitis optica (NMO) but initially scored negative by tissue-based indirect immunofluorescence (IIF) assay; and 2) evaluate the impact of serostatus on phenotype and outcome.
From Mayo Clinic records (2005-2011), we identified 163 patients with NMO; 110 (67%) were seropositive by IIF and 53 (33%) were scored seronegative. Available stored sera from 49 "seronegative" patients were tested by ELISA, AQP4-transfected cell-based assay, and in-house fluorescence-activated cell sorting assay. Clinical characteristics were compared based on final serostatus.
Thirty of the 49 IIF-negative patients (61%) were reclassified as seropositive, yielding an overall AQP4-IgG seropositivity rate of 88% (i.e., 12% seronegative). The fluorescence-activated cell sorting assay improved the detection rate to 87%, cell-based assay to 84%, and ELISA to 79%. The sex ratio (female to male) was 1:1 for seronegatives and 9:1 for seropositives (p < 0.0001). Simultaneous optic neuritis and transverse myelitis as onset attack type (i.e., within 30 days of each other) occurred in 32% of seronegatives and in 3.6% of seropositives (p < 0.0001). Relapse rate, disability outcome, and other clinical characteristics did not differ significantly.
Serological tests using recombinant AQP4 antigen are significantly more sensitive than tissue-based IIF for detecting AQP4-IgG. Testing should precede immunotherapy; if negative, later-drawn specimens should be tested. AQP4-IgG-seronegative NMO is less frequent than previously reported and is clinically similar to AQP4-IgG-seropositive NMO.
The use of corticosteroids to treat optic neuritis is controversial. At 15 clinical centers, we randomly assigned 457 patients with acute optic neuritis to receive oral prednisone (1 mg per kilogram of body weight per day) for 14 days; intravenous methylprednisolone (1 g per day) for 3 days, followed by oral prednisone (1 mg per kilogram per day) for 11 days; or oral placebo for 14 days. Visual function was assessed over a six-month follow-up period.
Visual function recovered faster in the group receiving intravenous methylprednisolone than in the placebo group; this was particularly true for the reversal of visual-field defects (P = 0.0001). Although the differences between the groups decreased with time, at six months the group that received intravenous methylprednisolone still had slightly better visual fields (P = 0.054), contrast sensitivity (P = 0.026), and color vision (P = 0.033) but not better visual acuity (P = 0.66). The outcome in the oral-prednisone group did not differ from that in the placebo group. In addition, the rate of new episodes of optic neuritis in either eye was higher in the group receiving oral prednisone, but not the group receiving intravenous methylprednisolone, than in the placebo group (relative risk for oral prednisone vs. placebo, 1.79; 95 percent confidence interval, 1.08 to 2.95).
Intravenous methylprednisolone followed by oral prednisone speeds the recovery of visual loss due to optic neuritis and results in slightly better vision at six months. Oral prednisone alone, as prescribed in this study, is an ineffective treatment and increases the risk of new episodes of optic neuritis.
• The baseline characteristics of 448 eligible patients entered into the Optic Neuritis Treatment Trial are described in an effort to summarize the clinical profile of acute optic neuritis. A total of 77.2% of the patients were women. Mean age was 31.8 years. Pain accompanied the visual loss in 92.2% of cases. The optic disc appeared swollen in 35.3% of the patients and normal in 64.7%. A wide variety of visual field defects were present. Abnormalities in asymptomatic fellow eyes were noted, particularly on perimetry. Magnetic resonance imaging showed changes consistent with demyelination of the brain in 48.7% of the patients. Magnetic resonance imaging, serologic studies (such as the antinuclear antibody test and the fluorescent treponemal antibody absorption test), chest roentgenography, and lumbar puncture were of limited utility in defining a cause for visual loss other than optic neuritis associated with demyelinative disease.
Importance Microcystic abnormalities involving the inner nuclear layer of the retina occurs in a subset of patients with multiple sclerosis, most commonly in eyes previously affected by symptomatic optic neuritis. Acute optic neuritis is a cardinal manifestation of neuromyelitis optica (NMO). To our knowledge, microcystic inner nuclear layer abnormalities have not been investigated in NMO.
Objective To establish whether microcystic inner nuclear layer abnormalities occur in NMO.
Design Observational, retrospective study.
Setting University of California at San Francisco Multiple Sclerosis Center (academic specialty clinic).
Patients Twenty-five consecutive patients with NMO based on 2006 diagnostic criteria or with NMO spectrum disease (defined by seropositivity for anti–aquaporin 4 IgG in the context of a single episode of transverse myelitis or optic neuritis).
Exposure Spectral-domain optical coherence tomography.
Main Outcomes and Measures Identification of microcystic inner nuclear layer pathology on spectral-domain optical coherence tomography. Multivariable linear regression was used to examine associations between microcystic changes and measures of retinal structure and function. The hypothesis was generated prior to the data being reviewed and analyzed.
Results Microcystic changes were identified in 5 of 25 patients with NMO (20%) and 7 of 48 total eyes, including 7 of 29 eyes (24%) previously affected by optic neuritis. Microcystic changes occurred exclusively in eyes with a history of acute symptomatic optic neuritis (100% of eyes with microcystic changes had experienced prior optic neuritis compared with 71% of NMO eyes without microcystic abnormalities). There were no significant differences between patients with NMO with and without microcystic changes in terms of age, sex, and aquaporin 4–IgG antibody status. The mean age in this cohort was 44 years (range, 13-81 years); 84% were women; 80% were aquaporin 4–IgG seropositive; and the median Expanded Disability Status Scale score was 4.0 (interquartile range, 3.0-6.5).
Conclusions and Relevance Microcystic inner nuclear layer pathology occurs in a proportion of patients with NMO in eyes previously affected by acute optic neuritis. Additional research is needed to understand the cause of this retinal pathology and determine whether it contributes to persistent visual disability in patients with NMO following optic neuritis.
Neuromyelitis optica is an antibody-mediated autoimmune inflammatory disease of the central nervous system. Reports have suggested that interferon beta which is beneficial for multiple sclerosis, exacerbates neuromyelitis optica. Our aim was to determine whether type I interferon plays a role in formation of neuromyelitis optica lesions. Immunoglobulin G from a neuromyelitis optica patient was injected intracerebrally with human complement to type I interferon receptor deficient and wildtype mice. Loss of aquaporin-4 and glial fibrillary acidic protein were reduced in type I interferon receptor deficient mice brain. Our findings suggest that type I interferon signaling contributes to neuromyelitis optica pathogenesis.
Neuromyelitis optica (NMO) is an idiopathic demyelinating disease of the CNS that can be clearly distinguished from multiple sclerosis (MS) by clinical, neuroradiogic, and pathologic criteria and the presence of the highly specific serum autoantibodies against the water channel aquaporin-4 (AQP4).(1) Although studies support a central role of the anti-AQP4 antibodies in the pathogenesis of NMO, their exact involvement in the immunopathogenetic cascade of the disease is still not clear, and T cells seem to be equally crucial for the full development of clinical and histopathologic NMO.
BAFF (B-cell activating factor of the tumor necrosis factor family) and APRIL (a proliferation-inducing ligand) are two of the major survival factors for B cells. Many studies have shown that BAFF levels were elevated in MS patients. However, whether the levels of CSF BAFF/APRIL increased in NMO patients was still unclear.
To measure the CSF BAFF and APRIL concentration of in NMO patients, and explore their relationship with disease activity in NMO.
CSF BAFF and APRIL was measured by an enzyme-linked immunosorbent assay (ELISA) in NMO (n = 22), MS (n = 18) patients and controls (n = 14).
Concentration of BAFF and APRIL in NMO patients were significantly higher than MS and controls. CSF BAFF and APRIL levels in controls were also lower than MS. Both NMO and MS revealed an increased disease disability with increased CSF BAFF. CSF APRIL was associated with EDSS scores in NMO, but not found in MS.
BAFF/APRIL system considered important for aggressive B cells and T-cell responses, and may stimulates B cells and T cell activation in acute relapse of NMO and MS. In NMO patients, CSF BAFF and APRIL may be key factors of B cell immune response and reflect disease severity.
Macular oedema typically results from blood-retinal barrier disruption. It has recently been reported that patients with multiple sclerosis treated with FTY-720 (fingolimod) may exhibit macular oedema. Multiple sclerosis is not otherwise thought to be associated with macular oedema except in the context of comorbid clinical uveitis. Despite a lack of myelin, the retina is a site of inflammation and microglial activation in multiple sclerosis and demonstrates significant neuronal and axonal loss. We unexpectedly observed microcystic macular oedema using spectral domain optical coherence tomography in patients with multiple sclerosis who did not have another reason for macular oedema. We therefore evaluated spectral domain optical coherence tomography images in consecutive patients with multiple sclerosis for microcystic macular oedema and examined correlations between macular oedema and visual and ambulatory disability in a cross-sectional analysis. Participants were excluded if there was a comorbidity that could account for the presence of macular oedema, such as uveitis, diabetes or other retinal disease. A microcystic pattern of macular oedema was observed on optical coherence tomography in 15 of 318 (4.7%) patients with multiple sclerosis. No macular oedema was identified in 52 healthy controls assessed over the same period. The microcystic oedema predominantly involved the inner nuclear layer of the retina and tended to occur in small, discrete patches. Patients with multiple sclerosis with microcystic macular oedema had significantly worse disability [median Expanded Disability Score Scale 4 (interquartile range 3-6)] than patients without macular oedema [median Expanded Disability Score Scale 2 (interquartile range 1.5-3.5)], P = 0.0002. Patients with multiple sclerosis with microcystic macular oedema also had higher Multiple Sclerosis Severity Scores, a measure of disease progression, than those without oedema [median of 6.47 (interquartile range 4.96-7.98) versus 3.65 (interquartile range 1.92-5.87), P = 0.0009]. Microcystic macular oedema occurred more commonly in eyes with prior optic neuritis than eyes without prior optic neuritis (50 versus 27%) and was associated with lower visual acuity (median logMAR acuity of 0.17 versus -0.1) and a thinner retinal nerve fibre layer. The presence of microcystic macular oedema in multiple sclerosis suggests that there may be breakdown of the blood-retinal barrier and tight junction integrity in a part of the nervous system that lacks myelin. Microcystic macular oedema may also contribute to visual dysfunction beyond that explained by nerve fibre layer loss. Microcystic changes need to be assessed, and potentially adjusted for, in clinical trials that evaluate macular volume as a marker of retinal ganglion cell survival. These findings also have implications for clinical monitoring in patients with multiple sclerosis on sphingosine 1-phosphate receptor modulating agents.
There has been significant progress in our understanding of the pathology and pathogenesis of central nervous system inflammatory demyelinating diseases. Neuropathological studies have provided fundamental new insights into the pathogenesis of these disorders and have led to major advances in our understanding of multiple sclerosis (MS) heterogeneity, the substrate of irreversible progressive disability in MS, the relationship between inflammation and neurodegeneration in MS, the neuroimaging correlates of MS lesions, and the pathogenesis of other central nervous system inflammatory disorders, including neuromyelitis optica, acute disseminated encephalomyelitis, and Balo's concentric sclerosis. Herein, we review the pathological features of these central nervous system inflammatory demyelinating disorders and discuss neuropathological studies that have yielded novel insights into potential mechanisms involved in the formation of the demyelinated lesion.
Visual dysfunction is one of the most common clinical manifestations of multiple sclerosis (MS). Just over a decade ago, MS clinical trials did not include visual outcomes, but experts recognized the need for more sensitive measures of visual function. Low-contrast letter acuity emerged as the leading candidate to measure visual disability in MS, and subsequent studies found low-contrast acuity testing to correlate well with brain MRI lesion burden, visual-evoked potentials, quality of life (QOL), and retinal nerve fiber layer (RNFL) loss, as measured by optical coherence tomography (OCT). OCT in MS has allowed for assessment of structure-function correlations that make the anterior visual pathway and acute optic neuritis (ON) ideal models for testing novel agents for neuroprotection and repair. New therapies that reduce axonal loss by neuroprotective or myelin repair mechanisms can now be assessed noninvasively by OCT and coupled with visual function data. Based on OCT studies in MS, RNFL thickness is reduced significantly among patients (92 μm) vs controls (105 μm) and is particularly reduced in MS eyes with a history of ON (85 μm). Worsening of visual function by a clinically significant ≥ 7 letters or approximately 1.5 lines for low-contrast acuity is associated with approximately 4.5 μm reductions in RNFL thickness in MS eyes. Longitudinal studies of OCT have also shown RNFL axonal loss over time that occurs even in the absence of acute ON and that correlates with clinically meaningful worsening of vision and QOL, even in patients with benign MS. The latest OCT investigations involve high-resolution spectral-domain (SD) OCT with segmentation and measurement of specific retinal layers using computerized algorithms. These methods allow quantitation of ganglion cell (neuronal) layer loss and axonal degeneration in MS in vivo. In this review, we examine the data from these studies and ongoing trials that highlight the entity of ON as a model to investigate neuroprotection and neurorepair. In doing so, we also present representative group data from studies that have examined visual function, OCT measures, and QOL scales in patients with MS and ON and disease-free controls. These data, and those from recent meta-analyses, may be used to provide reference values for the development of clinical trial protocols.
Background:
Disturbances in visual function are common in patients with multiple sclerosis (MS) and are often accompanied by substantial impairments in daily functioning and quality of life. Lesions associated with these impairments frequently involve the afferent visual pathway.
Expert clinical opinion:
Because these impairments are often not readily apparent on commonly used high-contrast acuity tests, low-contrast charts (e.g., low-contrast Sloan letter charts) have gained validity in the assessment of visual dysfunction in patients with MS. Decrements in low-contrast letter acuity are associated with MS and correlate with increasing disability, MRI abnormalities, and reduced retinal nerve fiber layer (RNFL) thickness as measured by optical coherence tomography (OCT). These findings suggest that low-contrast letter acuity testing is a potentially useful addition to disability scales such as the Multiple Sclerosis Functional Composite, serving as another surrogate marker for MS disability. Assessment of RNFL thickness by OCT, which is also associated with visual impairment, also may be considered for inclusion in clinical trials evaluating treatments for MS.
Future directions:
The effects of disease-modifying therapies on visual dysfunction in patients with MS have been evaluated only recently. Two phase 3 studies of natalizumab showed that low-contrast letter acuity testing, included as an exploratory outcome, demonstrated treatment effects. Other ongoing studies have incorporated low-contrast acuity and OCT measures of RNFL thickness. The availability and wider use of low-contrast letter acuity tests, in combination with ocular imaging techniques, may improve assessment of treatment efficacy in patients with MS.
After intracranial inoculation, neurovirulent mouse hepatitis virus (MHV) strains induce acute inflammation, demyelination, and axonal loss in the central nervous system. Prior studies using recombinant MHV strains that differ only in the spike gene, which encodes a glycoprotein involved in virus-host cell attachment, demonstrated that spike mediates anterograde axonal transport of virus to the spinal cord. A demyelinating MHV strain induces optic neuritis, but whether this is due to the retrograde axonal transport of viral particles to the retina or due to traumatic disruption of retinal ganglion cell axons during intracranial inoculation is not known. Using recombinant isogenic MHV strains, we examined the ability of recombinant MHV to induce optic neuritis by retrograde spread from the brain through the optic nerve into the eye after intracranial inoculation. Recombinant demyelinating MHV induced macrophage infiltration of optic nerves, demyelination, and axonal loss, whereas optic neuritis and axonal injury were minimal in mice infected with the nondemyelinating MHV strain that differs in the spike gene. Thus, optic neuritis was dependent on a spike glycoprotein-mediated mechanism of viral antigen transport along retinal ganglion cell axons. These data indicate that MHV spreads by retrograde axonal transport to the eye and that targeting spike protein interactions with axonal transport machinery is a potential therapeutic strategy for central nervous system viral infections and associated diseases.
This review explores the principle features of the immunopathology of multiple sclerosis (MS), particularly relapsing-remitting MS. It highlights the emerging concepts in the pathogenesis of MS in the context of known features of pathology, including the characterization of cytokine networks promoting inflammatory damage of the central nervous system, B-cell involvement, and inflammatory damage of axons and neurons. This article preferentially focuses on MS rather than animal models of the disease, such as experimental autoimmune encephalomyelitis.
Although a fraction of human blood memory CD4(+) T cells expresses chemokine (C-X-C motif) receptor 5 (CXCR5), their relationship to T follicular helper (Tfh) cells is not well established. Here we show that human blood CXCR5(+)CD4(+) T cells share functional properties with Tfh cells and appear to represent their circulating memory compartment. Blood CXCR5(+)CD4(+) T cells comprised three subsets: T helper 1 (Th1), Th2, and Th17 cells. Th2 and Th17 cells within CXCR5(+), but not within CXCR5(-), compartment efficiently induced naive B cells to produce immunoglobulins via interleukin-21 (IL-21). In contrast, Th1 cells from both CXCR5(+) and CXCR5(-) compartments lacked the capacity to help B cells. Patients with juvenile dermatomyositis, a systemic autoimmune disease, displayed a profound skewing of blood CXCR5(+) Th cell subsets toward Th2 and Th17 cells. Importantly, the skewing of subsets correlated with disease activity and frequency of blood plasmablasts. Collectively, our study suggests that an altered balance of Tfh cell subsets contributes to human autoimmunity.
Experimental autoimmune encephalomyelitis (EAE), a model for the human disease multiple sclerosis (MS), is dependent upon the activation and effector functions of autoreactive CD4 T cells. Multiple interactions between CD4 T cells and major histocompatibility class II (MHCII)+ antigen presenting cells (APCs) must occur in both the periphery and central nervous system (CNS) to elicit autoimmunity. The identity of the MHCII+ APCs involved throughout this process remains in question. We investigated which APC in the periphery and CNS mediates disease using transgenic mice with MHCII expression restricted to dendritic cells (DCs). MHCII expression restricted to DCs results in normal susceptibility to peptide-mediated EAE. Indeed, radiation-sensitive bone marrow-derived DCs were sufficient for all APC functions during peptide-induced disease. However, DCs alone were inefficient at promoting disease after immunization with the myelin protein myelin oligodendrocyte glycoprotein (MOG), even in the presence of MHCII-deficient B cells. Consistent with a defect in disease induction following protein immunization, antigen presentation by DCs alone was incapable of mediating spontaneous optic neuritis. These results indicate that DCs are capable of perpetuating CNS-targeted autoimmunity when antigens are readily available, but other APCs are required to efficiently initiate pathogenic cognate CD4 T cell responses.
Detection of aquaporin-4-specific immunoglobulin G (IgG) has expanded the spectrum of neuromyelitis optica (NMO). Rare reports of familial aggregation have suggested a component of genetic susceptibility but these reports mostly antedated the discovery of the NMO-IgG biomarker and recently updated diagnostic criteria.
We report a case series describing the demographic, clinical, neuroimaging, and NMO-IgG serologic status of 12 multiplex NMO pedigrees with a total of 25 affected individuals.
Twenty-one patients (84%) were women. Families were Asian (n = 5), Latino (n = 4), white (n = 1), or African (n = 2). Apparent transmission was either maternal (n = 5) or paternal (n = 2). In 1 family, 3 individuals had NMO; in the others, 2 individuals were affected. Sibling pairs (n = 6), parent-child (n = 4), and aunt-niece (n = 3) pairs were observed. Nineteen patients (76%) were NMO-IgG positive. Twelve (48%) had clinical or serologic evidence of another autoimmune disease. Familial occurrence of NMO occurs in approximately 3% of patients with well-established diagnosis of NMO.
A small proportion of patients with NMO have relatives with this condition, but familial occurrence is more common than would be expected from its frequency in the general population. Familial NMO is indistinguishable from sporadic NMO based on clinical symptoms, age at onset, sex distribution, and frequency of NMO-IgG detection. One or 2 generations were affected and affected individuals represented a small fraction of family members. Taken together, these data suggest complex genetic susceptibility in NMO.
To assess the frequency of bilateral and recurrent optic neuritis (ON) in multiple sclerosis (MS) and to compare these results with epidemiological data of ON in neuromyelitis optica (NMO) and recurrent ON without other signs of disease.
We identified 472 patients with diagnosis of MS from the Swedish Multiple Sclerosis Register. These patients were evaluated for the presence of ON and whether the ON was the presenting symptom of MS; unilateral or bilateral; monophasic or recurrent.
Twenty-one percent presented with ON as their first manifestation of MS. The proportion of patients developing a second attack of ON before demonstration of other manifestations of MS was 5.5% and the frequency of recurrent bilateral ON as the presenting symptom was 3.8%. Only two patients presented with simultaneously appearing bilateral ON corresponding to 0.42%.
Recurrent ON, whether unilateral or bilateral, is a common presentation of MS. As MS is a much more common disease than NMO, care must be taken when evaluating the work-up of patients with recurrent ON. In some cases repeated MRI and lumbar punctures are warranted to improve diagnostic accuracy, even in the presence of the serological marker NMO-IgG.
Acute demyelinating optic neuritis is a condition of the optic nerves characterized by inflammation, demyelination, and neurodegeneration. Optic neuritis is a relatively common demyelinating event, strongly associated with multiple sclerosis. A number of clinical, radiographic, retinal imaging, and electrophysiologic techniques have provided significant insight into the pathologic and pathophysiologic mechanisms of optic neuritis and its related disorder multiple sclerosis. The development of validated biomarkers within the anterior visual system has paved the way for novel investigations aimed at characterizing the processes of axonal loss and neurodegeneration, neuroprotection, and perhaps even neurorestoration strategies.
The serum of most neuromyelitis optica (NMO) patients contains autoantibodies (NMO-IgGs) directed against the aquaporin-4 (AQP4) water channel located on astrocyte foot processes in the perivessel and subpial areas of the brain. Our objectives were to determine the source of central nervous system (CNS) NMO-IgGs and their role in disease pathogenesis.
Fluorescence-activated cell sorting and single-cell reverse transcriptase polymerase chain reaction were used to identify overrepresented plasma cell immunoglobulin (Ig) sequences in the cerebrospinal fluid (CSF) of an NMO patient after a first clinical attack. Monoclonal recombinant antibodies (rAbs) were generated from the paired heavy and light chain sequences and tested for target specificity and Fc effector function. The effect of CSF rAbs on CNS immunopathology was investigated by delivering single rAbs to rats with experimental autoimmune encephalomyelitis (EAE).
Repertoire analysis revealed a dynamic, clonally expanded plasma cell population with features of an antigen-targeted response. Using multiple independent assays, 6 of 11 rAbs generated from CSF plasma cell clones specifically bound to AQP4. AQP4-specific rAbs recognized conformational epitopes and mediated both AQP4-directed antibody-dependent cellular cytotoxicity and complement-mediated lysis. When administered to rats with EAE, an AQP4-specific NMO CSF rAb induced NMO immunopathology: perivascular astrocyte depletion, myelinolysis, and complement and Ig deposition.
Molecular characterization of the CSF plasma cell repertoire in an early NMO patient demonstrates that AQP4-specific Ig is synthesized intrathecally at disease onset and directly contributes to CNS pathology. AQP4 is now the first confirmed antigenic target in human demyelinating disease.
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.
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.
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.
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.