Rejuvenating fecal microbiota transplant enhances peripheral nerve repair in aged mice by modulating endoneurial inflammation

Peripheral nerve injury (PNI) resulting from trauma or neuropathies can cause significant disability, and its prognosis deteriorates with age. Emerging evidence suggests that gut dysbiosis and reduced fecal short-chain fatty acids (SCFAs) contribute to an age-related systemic hyperinflammation (inflammaging), which hinders nerve recovery after injury. This study thus aimed to evaluate the pro-regenerative effects of a rejuvenating fecal microbiota transplant (FMT) in a preclinical PNI model using aged mice. Aged C57BL/6 mice underwent bilateral crush injuries to their sciatic nerves. Subsequently, they either received FMT from young donors at three and four days after the injury or retained their aged gut microbiota. We analyzed gut microbiome composition and SCFA concentrations in fecal samples. The integrity of the ileac mucosal barrier was assessed by immunofluorescence staining of Claudin-1. Flow cytometry was utilized to examine immune cells and cytokine production in the ileum, spleen, and sciatic nerve. Various assessments, including behavioural tests, electrophysiological studies, and morphometrical analyses, were conducted to evaluate peripheral nerve function and repair following injury. Rejuvenating FMT reversed age-related gut dysbiosis by increasing Actinobacteria, especially Bifidobacteriales genera. This intervention also led to an elevation of gut SCFA levels and mitigated age-related ileac mucosal leakiness in aged recipients. Additionally, it augmented the number of T-helper 2 (Th2) and regulatory T (Treg) cells in the ileum and spleen, with the majority being positive for anti-inflammatory interleukin-10 (IL-10). In sciatic nerves, rejuvenating FMT resulted in increased M2 macrophage counts and a higher IL-10 production by IL-10+TNF-α- M2 macrophage subsets. Ultimately, restoring a youthful gut microbiome in aged mice led to improved nerve repair and enhanced functional recovery after PNI. Considering that FMT is already a clinically available technique, exploring novel translational strategies targeting the gut microbiome to enhance nerve repair in the elderly seems promising and warrants further evaluation.

Blockade of Rho-associated kinase prevents inhibition of axon regeneration of peripheral nerves induced by anti-ganglioside antibodies

Anti-ganglioside antibodies are associated with delayed/poor clinical recovery in Guillain-Barrè syndrome, mostly related to halted axon regeneration. Cross-linking of cell surface gangliosides by anti-ganglioside antibodies triggers inhibition of nerve repair in in vitro and in vivo paradigms of axon regeneration. These effects involve the activation of the small GTPase RhoA/ROCK signaling pathways, which negatively modulate growth cone cytoskeleton, similarly to well stablished inhibitors of axon regeneration described so far. The aim of this work was to perform a proof of concept study to demonstrate the effectiveness of Y-27632, a selective pharmacological inhibitor of ROCK, in a mouse model of axon regeneration of peripheral nerves, where the passive immunization with a monoclonal antibody targeting gangliosides GD1a and GT1b was previously reported to exert a potent inhibitory effect on regeneration of both myelinated and unmyelinated fibers. Our results demonstrate a differential sensitivity of myelinated and unmyelinated axons to the pro-regenerative effect of Y-27632. Treatment with a total dosage of 9 mg/kg of Y-27632 resulted in a complete prevention of anti-GD1a/GT1b monoclonal antibody-mediated inhibition of axon regeneration of unmyelinated fibers to skin and the functional recovery of mechanical cutaneous sensitivity. In contrast, the same dose showed toxic effects on the regeneration of myelinated fibers. Interestingly, scale down of the dosage of Y-27632 to 5 mg/kg resulted in a significant although not complete recovery of regenerated myelinated axons exposed to anti-GD1a/GT1b monoclonal antibody in the absence of toxicity in animals exposed to only Y-27632. Overall, these findings confirm the in vivo participation of RhoA/ROCK signaling pathways in the molecular mechanisms associated with the inhibition of axon regeneration induced by anti-GD1a/GT1b monoclonal antibody. Our findings open the possibility of therapeutic pharmacological intervention targeting RhoA/Rock pathway in immune neuropathies associated with the presence of anti-ganglioside antibodies and delayed or incomplete clinical recovery after injury in the peripheral nervous system.

CSF Findings in Relation to Clinical Characteristics, Subtype, and Disease Course in Patients With Guillain-Barré Syndrome

BACKGROUND AND OBJECTIVES

To investigate CSF findings in relation to clinical and electrodiagnostic subtypes, severity, and outcome of Guillain-Barré syndrome (GBS) based on 1,500 patients in the International GBS Outcome Study.

METHODS

Albuminocytologic dissociation (ACD) was defined as an increased protein level (>0.45 g/L) in the absence of elevated white cell count (<50 cells/μL). We excluded 124 (8%) patients because of other diagnoses, protocol violation, or insufficient data. The CSF was examined in 1,231 patients (89%).

RESULTS

In 846 (70%) patients, CSF examination showed ACD, which increased with time from weakness onset: ≤4 days 57%, >4 days 84%. High CSF protein levels were associated with a demyelinating subtype, proximal or global muscle weakness, and a reduced likelihood of being able to run at week 2 (odds ratio [OR] 0.42, 95% CI 0.25-0.70; p = 0.001) and week 4 (OR 0.44, 95% CI 0.27-0.72; p = 0.001). Patients with the Miller Fisher syndrome, distal predominant weakness, and normal or equivocal nerve conduction studies were more likely to have lower CSF protein levels. CSF cell count was <5 cells/μL in 1,005 patients (83%), 5-49 cells/μL in 200 patients (16%), and ≥50 cells/μL in 13 patients (1%).

DISCUSSION

ACD is a common finding in GBS, but normal protein levels do not exclude this diagnosis. High CSF protein level is associated with an early severe disease course and a demyelinating subtype. Elevated CSF cell count, rarely ≥50 cells/μL, is compatible with GBS after a thorough exclusion of alternative diagnoses.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that CSF ACD (defined by the Brighton Collaboration) is common in patients with GBS.

Predicting Outcome in Guillain-Barré Syndrome: International Validation of the Modified Erasmus GBS Outcome Score

BACKGROUND AND OBJECTIVES

The clinical course and outcome of the Guillain-Barré syndrome (GBS) are diverse and vary among regions. The modified Erasmus GBS Outcome Score (mEGOS), developed with data from Dutch patients, is a clinical model that predicts the risk of walking inability in patients with GBS. The study objective was to validate the mEGOS in the International GBS Outcome Study (IGOS) cohort and to improve its performance and region specificity.

METHODS

We used prospective data from the first 1,500 patients included in IGOS, aged ≥6 years and unable to walk independently. We evaluated whether the mEGOS at entry and week 1 could predict the inability to walk unaided at 4 and 26 weeks in the full cohort and in regional subgroups, using 2 measures for model performance: (1) discrimination: area under the receiver operating characteristic curve (AUC) and (2) calibration: observed vs predicted probability of being unable to walk independently. To improve the model predictions, we recalibrated the model containing the overall mEGOS score, without changing the individual predictive factors. Finally, we assessed the predictive ability of the individual factors.

RESULTS

For validation of mEGOS at entry, 809 patients were eligible (Europe/North America [n = 677], Asia [n = 76], other [n = 56]), and 671 for validation of mEGOS at week 1 (Europe/North America [n = 563], Asia [n = 65], other [n = 43]). AUC values were >0.7 in all regional subgroups. In the Europe/North America subgroup, observed outcomes were worse than predicted; in Asia, observed outcomes were better than predicted. Recalibration improved model accuracy and enabled the development of a region-specific version for Europe/North America (mEGOS-Eu/NA). Similar to the original mEGOS, severe limb weakness and higher age were the predominant predictors of poor outcome in the IGOS cohort.

DISCUSSION

mEGOS is a validated tool to predict the inability to walk unaided at 4 and 26 weeks in patients with GBS, also in countries outside the Netherlands. We developed a region-specific version of mEGOS for patients from Europe/North America.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that the mEGOS accurately predicts the inability to walk unaided at 4 and 26 weeks in patients with GBS.

TRIAL REGISTRATION INFORMATION

NCT01582763.

Precision Intravenous Immunoglobulin Dosing and Clinical Outcomes: A Retrospective Chart Review

OBJECTIVES

Intravenous immunoglobulin (IVIg) is used for treatment of acute neurologic conditions such as Guillain-Barre syndrome, chronic inflammatory demyelinating polyradiculoneuropathy relapse, and myasthenia gravis exacerbation. Precision dosing (adjusted or ideal body weight) is proposed to conserve IVIg. There have been no published studies comparing clinical outcomes in traditional dosing (actual body weight) with precision dosing. In 2014, our institution began dosing patients with precision dosing. This decision was largely performed by administration rather than physicians' preference. We sought to analyze our retrospective data to understand the change in dosing methods with neurologic outcomes.

METHODS

We performed a retrospective review of all patients hospitalized at a single center who received IVIg for myasthenia gravis, Guillain-Barre syndrome, and chronic inflammatory demyelinating polyradiculoneuropathy from January 2010 to October 2017. We collected baseline information and clinical outcomes including mortality, readmission, need for second rescue treatment, length of stay, discharge disposition, treatment-related adverse events, and modified research council posttreatment sum score.

RESULTS

Length of stay was significantly shorter with precision dosing. There was no statistically significant difference in discharge disposition, readmission, rescue treatment, or modified research council posttreatment sum score with precision dosing.

CONCLUSION

Precision dosing did not adversely affect short-term neurologic outcomes.

Guillain-Barré Syndrome

PURPOSE OF REVIEW

This article reviews the clinical features, diagnosis and differential diagnosis, prognosis, pathogenesis, and current and upcoming treatments of Guillain-Barré syndrome (GBS).

RECENT FINDINGS

GBS is an acute inflammatory neuropathic illness with striking clinical manifestations and significant morbidity. A substantial proportion of patients with GBS do not respond to current immunomodulatory therapies (ie, plasma exchange and IV immunoglobulin [IVIg]), highlighting the need for new therapies. Prognostic models that can accurately predict functional recovery and the need for artificial ventilation have emerged. These models are practical, and online calculators are available for clinical use, facilitating early recognition of patients with poor outcome and the opportunity to personalize management decisions. Clinical and experimental studies have identified innate immune effectors (complement, macrophage lineage cells, and activating Fcγ receptors) as important mediators of inflammatory nerve injury. Two complement inhibitors are undergoing clinical testing for efficacy in GBS.

SUMMARY

GBS is the most common cause of acute flaccid paralysis in the United States and worldwide. New treatments for GBS have not emerged since the 1990s. Our understanding of the pathogenesis of this disorder has progressed, particularly over the past decade; as a result, new therapeutic agents targeting different components of the complement cascade are at advanced stages of clinical development.

Subcutaneous immunoglobulin treatment for chronic inflammatory demyelinating polyneuropathy

Immunoglobulin G (IgG) therapy is an established long‐term treatment in chronic inflammatory demyelinating polyneuropathy (CIDP) that is commonly administered intravenously (IVIg). The subcutaneous immunoglobulin (SCIg) administration route is a safe and effective alternative option, approved by the United States Food and Drug Administration (FDA) in 2018, for maintenance treatment of adults with CIDP. Physicians and patients alike need to be aware of all their treatment options in order to make informed decisions and plan long‐term treatment strategies. In this review, we collate the evidence for SCIg in CIDP from all published studies and discuss their implications and translation to clinical practice. We also provide guidance on the practicalities of how and when to transition patients from IVIg to SCIg and ongoing patient support. Evidence suggests that IVIg and SCIg have comparable long‐term efficacy in CIDP. However, SCIg can provide additional benefits for some patients, including no requirement for venous access or premedication, and reduced frequency of systemic adverse events. Local‐site reactions are more common with SCIg than IVIg, but these are mostly well‐tolerated and abate with subsequent infusions. Data suggest that many patients prefer SCIg following transition from IVIg. SCIg preference may be a result of the independence and flexibility associated with self‐infusion, whereas IVIg preference may be a result of familiarity and reliance on a healthcare professional for infusions. In practice, individualizing maintenance dosing based on disease behavior and determining the minimally effective IgG dose for individuals are key considerations irrespective of the administration route chosen.

Heat shock protein is a key therapeutic target for nerve repair in autoimmune peripheral neuropathy and severe peripheral nerve injury

Guillain-Barré syndrome (GBS) is an autoimmune peripheral neuropathy and a common cause of neuromuscular paralysis. Preceding infection induces the production of anti-ganglioside (GD) antibodies attacking its own peripheral nerves. In severe proximal peripheral nerve injuries that require long-distance axon regeneration, motor functional recovery is virtually nonexistent. Damaged axons fail to regrow and reinnervate target muscles. In mice, regenerating axons must reach the target muscle within 35 days (critical period) to reform functional neuromuscular junctions and regain motor function. Successful functional recovery depends on the rate of axon regeneration and debris removal (Wallerian degeneration) after nerve injury. The innate-immune response of the peripheral nervous system to nerve injury such as timing and magnitude of cytokine production is crucial for Wallerian degeneration. In the current study, forced expression of human heat shock protein (hHsp) 27 completely reversed anti-GD-induced inhibitory effects on nerve repair assessed by animal behavioral assays, electrophysiology and histology studies, and the beneficial effect was validated in a second mouse line of hHsp27. The protective effect of hHsp27 on prolonged muscle denervation was examined by performing repeated sciatic nerve crushes to delay regenerating axons from reaching distal muscle from 37 days up to 55 days. Strikingly, hHsp27 was able to extend the critical period of motor functional recovery for up to 55 days and preserve the integrity of axons and mitochondria in distal nerves. Cytokine array analysis demonstrated that a number of key cytokines which are heavily involved in the early phase of innate-immune response of Wallerian degeneration, were found to be upregulated in the sciatic nerve lysates of hHsp27 Tg mice at 1 day postinjury. However, persistent hyperinflammatory mediator changes were found after chronic denervation in sciatic nerves of littermate mice, but remained unchanged in hHsp27 Tg mice. Taken together, the current study provides insight into the development of therapeutic strategies to enhance muscle receptiveness (reinnervation) by accelerating axon regeneration and Wallerian degeneration.

Elimination of activating Fcγ receptors in spontaneous autoimmune peripheral polyneuropathy model protects from neuropathic disease

Spontaneous autoimmune peripheral polyneuropathy (SAPP) is a reproducible mouse model of chronic inflammatory peripheral neuropathy in female non-obese diabetic mice deficient in co-stimulatory molecule, B7-2 (also known as CD86). There is evidence that SAPP is an interferon-γ, CD4+ T-cell-mediated disorder, with autoreactive T-cells and autoantibodies directed against myelin protein zero involved in its immunopathogenesis. Precise mechanisms leading to peripheral nerve system inflammation and nerve injury including demyelination in this model are not well defined. We examined the role of activating Fc-gamma receptors (FcγRs) by genetically ablating Fcγ-common chain (Fcer1g) shared by all activating FcγRs in the pathogenesis of this model. We have generated B7-2/ Fcer1g-double null animals for these studies and found that the neuropathic disease is substantially ameliorated in these animals as assessed by behavior, electrophysiology, immunocytochemistry, and morphometry. Our current studies focused on characterizing systemic and endoneurial inflammation in B7-2-null and B7-2/ Fcer1g-double nulls. We found that accumulation of endoneurial inflammatory cells was significantly attenuated in B7-2/ Fcer1g-double nulls compared to B7-2-single nulls. Whereas, systemically the frequency of CD4+ regulatory T cells and expression of immunosuppressive cytokine, IL-10, were significantly enhanced in B7-2/ Fcer1g-double nulls. Overall, these findings suggest that elimination of activating FcγRs modulate nerve injury by altering endoneurial and systemic inflammation. These observations raise the possibility of targeting activating FcγRs as a treatment strategy in acquired inflammatory demyelinating neuropathies.

Anti-glycan antibodies halt axon regeneration in a model of Guillain Barrè Syndrome axonal neuropathy by inducing microtubule disorganization via RhoA-ROCK-dependent inactivation of CRMP-2

Several reports have linked the presence of high titers of anti-Gg Abs with delayed recovery/poor prognosis in GBS. In most cases, failure to recover is associated with halted/deficient axon regeneration. Previous work identified that monoclonal and patient-derived anti-Gg Abs can act as inhibitory factors in an animal model of axon regeneration. Further studies using primary dorsal root ganglion neuron (DRGn) cultures demonstrated that anti-Gg Abs can inhibit neurite outgrowth by targeting gangliosides via activation of the small GTPase RhoA and its associated kinase (ROCK), a signaling pathway common to other established inhibitors of axon regeneration. We aimed to study the molecular basis of the inhibitory effect of anti-Gg abs on neurite outgrowth by dissecting the molecular dynamics of growth cones (GC) cytoskeleton in relation to the spatial-temporal analysis of RhoA activity. We now report that axon growth inhibition in DRGn induced by a well characterized mAb targeting gangliosides GD1a/GT1b involves: i) an early RhoA/ROCK-independent collapse of lamellipodia; ii) a RhoA/ROCK-dependent shrinking of filopodia; and iii) alteration of GC microtubule organization/and presumably dynamics via RhoA/ROCK-dependent phosphorylation of CRMP-2 at threonine 555. Our results also show that mAb 1B7 inhibits peripheral axon regeneration in an animal model via phosphorylation/inactivation of CRMP-2 at threonine 555. Overall, our data may help to explain the molecular mechanisms underlying impaired nerve repair in GBS. Future work should define RhoA-independent pathway/s and effectors regulating actin cytoskeleton, thus providing an opportunity for the design of a successful therapy to guarantee an efficient target reinnervation.

Fluorescently-tagged anti-ganglioside antibody selectively identifies peripheral nerve in living animals

Selective in vivo delivery of cargo to peripheral nervous system (PNS) has broad clinical and preclinical applications. An important applicability of this approach is systemic delivery of fluorescently conjugated ligands that selectively label PNS, which could allow visualization of peripheral nerves during any surgery. We examine the use of an anti-ganglioside monoclonal antibody (mAb) as selective neuronal delivery vector for surgical imaging of peripheral nerves. Systemic delivery of an anti-ganglioside mAb was used for selective intraneuronal/axonal delivery of fluorescent agents to visualize nerves by surgical imaging in living mice. In this study, we show that intact motor, sensory, and autonomic nerve fibers/paths are distinctly labeled following a single nanomolar systemic injection of fluorescently labeled anti-ganglioside mAb. Tissue biodistribution studies with radiolabeled mAb were used to validate neuronal uptake of fluorescently labeled mAb. Implications of this proof of concept study are that fluorescent conjugates of anti-ganglioside mAbs are valuable delivery vectors to visualize nerves during surgery to avoid nerve injury and monitor nerve degeneration and regeneration after injury. These findings support that antibodies, and their derivatives/fragments, can be used as selective neuronal delivery vector for transport of various cargos to PNS in preclinical and clinical settings.

Dissecting the Role of Anti-ganglioside Antibodies in Guillain-Barré Syndrome: an Animal Model Approach

Guillain-Barré syndrome (GBS) is an autoimmune polyneuropathy disease affecting the peripheral nervous system (PNS). Most of the GBS patients experienced neurological symptoms such as paresthesia, weakness, pain, and areflexia. There are also combinations of non-neurological symptoms which include upper respiratory tract infection and diarrhea. One of the major causes of GBS is due largely to the autoantibodies against gangliosides located on the peripheral nerves. Gangliosides are sialic acid-bearing glycosphingolipids consisting of a ceramide lipid anchor with one or more sialic acids attached to a neutral sugar backbone. Molecular mimicry between the outer components of oligosaccharide of gangliosides on nerve membrane and lipo-oligosaccharide of microbes is thought to trigger the autoimmunity. Intra-peritoneal implantation of monoclonal ganglioside antibodies secreting hybridoma into animals induced peripheral neuropathy. Recent studies demonstrated that injection of synthesized anti-ganglioside antibodies raised by hybridoma cells into mice initiates immune response against peripheral nerves, and eventually failure in peripheral nerve regeneration. Accumulating evidences indicate that the conjugation of anti-ganglioside monoclonal antibodies to activating FcγRIII present on the circulating macrophages inhibits axonal regeneration. The activation of RhoA signaling pathways is also involved in neurite outgrowth inhibition. However, the link between these two molecular events remains unresolved and requires further investigation. Development of anti-ganglioside antagonists can serve as targeted therapy for the treatment of GBS and will open a new approach of drug development with maximum efficacy and specificity.

Inhibition of Rho-kinase differentially affects axon regeneration of peripheral motor and sensory nerves

The small GTPase RhoA and its down-stream effector Rho-kinase (ROCK) are important effector molecules of the neuronal cytoskeleton. Modulation of the RhoA/ROCK pathway has been shown to promote axonal regeneration, however in vitro and animal studies are inconsistent regarding the extent of axonal outgrowth induced by pharmacological inhibition of ROCK. We hypothesized that injury to sensory and motor nerves result in diverse activation levels of RhoA, which may impact the response of those nerve fiber modalities to ROCK inhibition. We therefore examined the effects of Y-27632, a chemical ROCK inhibitor, on the axonal outgrowth of peripheral sensory and motor neurons grown in the presence of growth-inhibiting chondroitin sulfate proteoglycans (CSPGs). In addition we examined the effects of three different doses of Y-27632 on nerve regeneration of motor and sensory nerves in animal models of peripheral nerve crush. In vitro, sensory neurons were less responsive to Y-27632 compared to motor neurons in a non-growth permissive environment. These differences were associated with altered expression and activation of RhoA in sensory and motor axons. In vivo, systemic treatment with high doses of Y-27632 significantly enhanced the regeneration of motor axons over short distances, while the regeneration of sensory fibers remained largely unchanged. Our results support the concept that in a growth non-permissive environment, the regenerative capacity of sensory and motor axons is differentially affected by the RhoA/ROCK pathway, with motor neurons being more responsive compared to sensory. Future treatments, that are aimed to modulate RhoA activity, should consider this functional diversity.

Sural sparing pattern discriminates Guillain-Barré syndrome from its mimics

INTRODUCTION

Electrodiagnostic features of demyelination are essential for establishing the diagnosis in demyelinating subtypes of Guillain-Barré syndrome (GBS), but they may also occur in disorders that mimic GBS clinically. Information about their frequency in GBS mimics is sparse.

METHODS

Evaluation of electrodiagnostic features from 38 patients with suspected GBS in whom the diagnosis was later refuted (GBS mimics). Their diagnostic accuracy was analyzed by comparison with nerve conduction studies (NCS) from 73 confirmed GBS patients.

RESULTS

Disorders that mimicked GBS clinically at the time of hospital admission included other inflammatory, metabolic, toxic, or infectious neuropathies and spinal cord disorders. The sural sparing pattern was the most specific electrodiagnostic feature for demyelinating GBS.

CONCLUSIONS

Common electrodiagnostic abnormalities in early demyelinating GBS do not usually exclude other rare differential diagnoses. An exception to this is the sural sparing pattern described here, which strongly supports the diagnosis of demyelinating GBS.

Fcγ receptor-mediated inflammation inhibits axon regeneration

Anti-glycan/ganglioside antibodies are the most common immune effectors found in patients with Guillain-Barré Syndrome, which is a peripheral autoimmune neuropathy. We previously reported that disease-relevant anti-glycan autoantibodies inhibited axon regeneration, which echo the clinical association of these antibodies and poor recovery in Guillain-Barré Syndrome. However, the specific molecular and cellular elements involved in this antibody-mediated inhibition of axon regeneration are not previously defined. This study examined the role of Fcγ receptors and macrophages in the antibody-mediated inhibition of axon regeneration. A well characterized antibody passive transfer sciatic nerve crush and transplant models were used to study the anti-ganglioside antibody-mediated inhibition of axon regeneration in wild type and various mutant and transgenic mice with altered expression of specific Fcγ receptors and macrophage/microglia populations. Outcome measures included behavior, electrophysiology, morphometry, immunocytochemistry, quantitative real-time PCR, and western blotting. We demonstrate that the presence of autoantibodies, directed against neuronal/axonal cell surface gangliosides, in the injured mammalian peripheral nerves switch the proregenerative inflammatory environment to growth inhibitory milieu by engaging specific activating Fcγ receptors on recruited monocyte-derived macrophages to cause severe inhibition of axon regeneration. Our data demonstrate that the antibody orchestrated Fcγ receptor-mediated switch in inflammation is one mechanism underlying inhibition of axon regeneration. These findings have clinical implications for nerve repair and recovery in antibody-mediated immune neuropathies. Our results add to the complexity of axon regeneration in injured peripheral and central nervous systems as adverse effects of B cells and autoantibodies on neural injury and repair are increasingly recognized.

Axonal degeneration in dorsal columns of spinal cord does not induce recruitment of hematogenous macrophages

It is generally accepted that there are two populations of macrophages that respond to neural injuries and successful recruitment of hematogenous macrophages has been shown to help the process of nerve repair in the peripheral nervous system (PNS). Meanwhile, the recruitment of circulating macrophages after central nerve system (CNS) injuries is considered mild and delayed. We compared the recruitment of circulating macrophages in the peripheral nerves and spinal cord after dorsal root ganglionectomies, which induce selective and approximately similar extent of sensory fiber degeneration in PNS and CNS, in bone marrow chimeric mice. Our results showed that circulating macrophages were efficiently recruited in PNS but virtually no recruitment in CNS despite degeneration of peripheral and central sensory projections emanating from the same dorsal root ganglion (DRG) neurons. The mechanisms that prevent recruitment of circulating macrophages in CNS after injury remain poorly elucidated.

High resolution diffusion tensor imaging of human nerves in forearm

PURPOSE

To implement high resolution diffusion tensor imaging (DTI) for visualization and quantification of peripheral nerves in human forearm.

MATERIALS AND METHODS

This HIPAA-compliant study was approved by our Institutional Review Board and written informed consent was obtained from all the study participants. Images were acquired with T1 -and T2 -weighted turbo spin echo with/without fat saturation, short tau inversion recovery (STIR). In addition, high spatial resolution (1.0 × 1.0 × 3.0 mm(3) ) DTI sequence was optimized for clearly visualizing ulnar, superficial radial and median nerves in the forearm. Maps of the DTI derived indices, fractional anisotropy (FA), mean diffusivity (MD), longitudinal diffusivity (λ// ) and radial diffusivity (λ⊥ ) were generated.

RESULTS

For the first time, the three peripheral nerves, ulnar, superficial radial, and median, were visualized unequivocally on high resolution DTI-derived maps. DTI delineated the forearm nerves more clearly than other sequences. Significant differences in the DTI-derived measures, FA, MD, λ// and λ⊥ , were observed among the three nerves. A strong correlation between the nerve size derived from FA map and T2 -weighted images was observed.

CONCLUSION

High spatial resolution DTI is superior in identifying and quantifying the median, ulnar, and superficial radial nerves in human forearm. Consistent visualization of small nerves and nerve branches is possible with high spatial resolution DTI. These normative data could potentially help in identifying pathology in diseased nerves. J. Magn. Reson. Imaging 2014;39:1374-1383. © 2013 Wiley Periodicals, Inc.

Peripheral neuropathy: assessment of proximal nerve integrity by diffusion tensor imaging

INTRODUCTION

We investigated the utility of diffusion tensor imaging (DTI) for detecting neuropathic changes in proximal nerve segments in patients with peripheral neuropathy.

METHODS

Twenty-one individuals with (n = 11) and without (n = 10) peripheral neuropathy underwent DTI of a defined sciatic nerve segment. Patients and controls were evaluated by clinical examination and nerve conduction studies at baseline and 6 months after the initial DTI scan.

RESULTS

The mean fractional anisotropy (FA) value was significantly lower in sciatic nerves from patients with peripheral neuropathy as compared with controls. Sciatic nerve FA values correlated with clinical disability scores and electrophysiological parameters of axonal damage at baseline and 6 months after MRI scan.

CONCLUSIONS

DTI-derived FA values are a sensitive measure to discriminate healthy from functionally impaired human sciatic nerve segments. DTI of proximal nerve segments may be useful for estimating the proximal axonal degeneration burden in patients with peripheral neuropathies.

Behavioral, electrophysiological, and histopathological characterization of a severe murine chronic demyelinating polyneuritis model

The objective of this study was to define the behavioral, electrophysiological, and morphological characteristics of spontaneous autoimmune peripheral polyneuropathy (SAPP) in female B7-2 deficient non-obese diabetic (NOD) mice. A cohort of 77 female B7-2 deficient and 31 wild-type control NOD mice were studied from 18 to 40 weeks of age. At pre-defined time points, the dorsal caudal tail and sciatic motor nerve conduction studies (MNCS) were performed. Sciatic nerves were harvested for morphological evaluation. SAPP mice showed slowly progressive severe weakness in hind and forelimbs without significant recovery after 30 weeks of age. MNCS showed progressive reduction in mean compound motor action potential amplitudes and conduction velocities, and increase in mean total waveform duration from 24 to 27 weeks of age, peaking between 32 and 35 weeks of age. Toluidine blue-stained, semi-thin plastic-embedded sections demonstrated focal demyelination associated with mononuclear cell infiltration early in the disease course, with progressively diffuse demyelination and axonal loss associated with more intense mononuclear infiltration at peak severity. Immunohistochemistry confirmed macrophage-predominant inflammation. This study verifies SAPP as a progressive, unremitting chronic inflammatory demyelinating polyneuropathy with axonal loss.

Diffusion tensor imaging of forearm nerves in humans

PURPOSE

To implement a diffusion tensor imaging (DTI) protocol for visualization of peripheral nerves in human forearm.

MATERIALS AND METHODS

This Health Insurance Portability and Accountability Act (HIPAA)-compliant study was approved by our Institutional Review Board and written informed consent was obtained from 10 healthy participants. T(1) - and T(2) -weighted turbo spin echo with fat saturation, short tau inversion recovery (STIR), and DTI sequences with 21 diffusion-encoding directions were implemented to acquire images of the forearm nerves with an 8 channel knee coil on a 3T MRI scanner. Identification of the nerves was based on T(1) -weighted, T(2) -weighted, STIR, and DTI-derived fractional anisotropy (FA) images. Maps of the DTI-derived indices, FA, mean diffusivity (MD), longitudinal diffusivity (λ(//) ), and radial diffusivity (λ(⟂) ) along the length of the nerves were generated.

RESULTS

DTI-derived maps delineated the forearm nerves more clearly than images acquired with other sequences. Only ulnar and median nerves were clearly visualized on the DTI-derived FA maps. No significant differences were observed between the left and right forearms in any of the DTI-derived measures. Significant variation in the DTI measures was observed along the length of the nerve. Significant differences in the DTI measures were also observed between the median and ulnar nerves.

CONCLUSION

DTI is superior in visualizing the median and ulnar nerves in the human forearm. The normative data could potentially help distinguish normal from diseased nerves.

Erythropoietin enhances nerve repair in anti-ganglioside antibody-mediated models of immune neuropathy

Guillain-Barré syndrome (GBS) is a monophasic immune neuropathic disorder in which a significant proportion of patients have incomplete recovery. The patients with incomplete recovery almost always have some degree of failure of axon regeneration and target reinnervation. Anti-ganglioside antibodies (Abs) are the most commonly recognized autoimmune markers in all forms of GBS and specific Abs are associated with the slow/poor recovery. We recently demonstrated that specific anti-ganglioside Abs inhibit axonal regeneration and nerve repair in preclinical models by activation of small GTPase RhoA and its downstream effectors. The objective of this study was to determine whether erythropoietin (EPO), a pleiotropic cytokine with neuroprotective and neurotrophic properties, enhances nerve regeneration in preclinical cell culture and animal models of autoimmune neuropathy/nerve repair generated with monoclonal and patient derived Abs. Primary neuronal cultures and a standardized sciatic crush nerve model were used to assess the efficacy of EPO in reversing inhibitory effects of anti-ganglioside Abs on nerve repair. We found that EPO completely reversed the inhibitory effects of anti-ganglioside Abs on axon regeneration in cell culture models and significantly improved nerve regeneration/repair in an animal model. Moreover, EPO-induced proregenerative effects in nerve cells are through EPO receptors and Janus kinase 2/Signal transducer and activator of transcription 5 pathway and not via early direct modulation of small GTPase RhoA. These preclinical studies indicate that EPO is a viable candidate drug to develop further for neuroprotection and enhancing nerve repair in patients with GBS.

Erythropoietin ameliorates rat experimental autoimmune neuritis by inducing transforming growth factor-β in macrophages

Erythropoietin (EPO) is a pleiotropic cytokine originally identified for its role in erythropoiesis. In addition, in various preclinical models EPO exhibited protective activity against tissue injury. There is an urgent need for potent treatments of autoimmune driven disorders of the peripheral nervous system (PNS), such as the Guillain-Barré syndrome (GBS), a disabling autoimmune disease associated with relevant morbidity and mortality. To test the therapeutic potential of EPO in experimental autoimmune neuritis (EAN) - an animal model of human GBS--immunological and clinical effects were investigated in a preventive and a therapeutic paradigm. Treatment with EPO reduced clinical disease severity and if given therapeutically also shortened the recovery phase of EAN. Clinical findings were mirrored by decreased inflammation within the peripheral nerve, and myelin was well maintained in treated animals. In contrast, EPO increased the number of macrophages especially in later stages of the experimental disease phase. Furthermore, the anti-inflammatory cytokine transforming growth factor (TGF)-beta was upregulated in the treated cohorts. In vitro experiments revealed less proliferation of T cells in the presence of EPO and TGF-beta was moderately induced, while the secretion of other cytokines was almost not altered by EPO. Our data suggest that EPO revealed its beneficial properties by the induction of beneficial macrophages and the modulation of the immune system towards anti-inflammatory responses in the PNS. Further studies are warranted to elaborate the clinical usefulness of EPO for treating immune-mediated neuropathies in affected patients.

Autoantobodies activate small GTPase RhoA to modulate neurite outgrowth

This review illustrates an example of adaptive immune responses (auto-antibodies) modulating growth/repair behavior of neurons in the disease context of Guillain-Barré syndrome (GBS), which is a prototypic autoimmune, acute monophasic disorder of the peripheral nerves that is the commonest cause of acute flaccid paralysis worldwide. Anti-ganglioside antibodies (Abs) are the most commonly recognized autoimmune markers in all forms of GBS and these Abs are associated with poor recovery. Extent of axonal injury and failure of axonal regeneration are critical determinants of recovery after GBS. In this clinical context, our group examined the hypothesis that anti-ganglioside Abs adversely affect axon regeneration after peripheral nerve injury. We show that anti-ganglioside Abs inhibit axon regeneration in preclinical cell culture and animal models. This inhibition is mediated by activation of small GTPase RhoA and its downstream effector Rho kinase (ROCK) by modulation of growth cone extension and associated neurite elongation in neuronal cultures. Our studies suggest that RhoA and ROCK are potential targets for development of novel therapeutic strategies to enhance nerve repair.

An unusual case of familial ALS and cerebellar ataxia

We report a case of familial amyotrophic lateral sclerosis (FALS) with clinical signs of cerebellar and posterior column involvement. The patient's work-up showed a known mutation (E100K) in the gene for Cu/Zn superoxide dismutase 1 (SOD1). Our case illustrates that extramotor symptoms, such as prominent cerebellar signs, can be seen in patients with FALS.

Management of biliary ascariasis in children living in an endemic area

BACKGROUND

One quarter of the world's population is known to be infected with ascariasis. It is endemic in various parts of the Indian subcontinent with a high incidence in the Kashmir valley. Although intestinal obstruction is the commonest complication of ascariasis in children, biliary ascariasis remains the second most common complication. We aimed to study the various types of clinical presentations, complications and different diagnostic tools and to assess various options for the management of biliary ascariasis.

MATERIALS AND METHODS

Sixty-one cases of ultrasound documented hepatobiliary ascariasis were studied prospectively over a period of 3 years from Jan 2003 to Dec 2005 at the Sheri-Kashmir Institute of Medical Sciences in Srinagar, Kashmir. All patients were children aged between 3 and 14 years. All patients were admitted to hospital and put on intravenous fluids, nothing per os until patients were symptom-free, broadspectrum antibiotics and antispasmodics. All patients received antihelminthics in the form of albendazole 400 mg as soon as patients could accept oral medication. Conservative management was continued until the patients were symptom-free. Endoscopic extraction was deferred until 3 weeks later except in patients with pyogenic cholangitis where urgent endoscopic intervention was carried out. Surgical intervention was carried out if both conservative management and endoscopic extraction failed or ERCP could not be performed for technical reasons or complications developed.

RESULTS

The most common presentation was upper abdominal pain in 36 (59%) patients followed by vomiting of worms in 20 (33.3%) cases. Complications included cholangitis in 8 (13.1%), obstructive jaundice in 7 (11.4%), acute pancreatitis in 1 (1.6%) and hepatic abscess in 1 (1.6%) patient. Spontaneous passage of worms from the biliary ducts was observed in 44 (72.1%) patients. ERCP was successful in 8 (13.1%) patients, and 9 (14.7%) patients needed surgical intervention.

CONCLUSION

In endemic countries, ascariasis should be suspected in patients with biliary disease. Most patients respond to conservative management although a few may need surgical intervention. Although this disease is prevalent in developing countries, because of increased travel and migration, clinicians elsewhere should be aware of the problems associated with ascariasis.

An update on pathobiologic roles of anti-glycan antibodies in Guillain-Barré syndrome

Anti-glycan antibodies directed against gangliosides are now considered the major immune effectors that induce damage to intact nerve fibers in some variants of the monophasic neuropathic disorders that comprise Guillain-Barré syndrome. Recent experimental studies elucidating the complexity of anti-glycan antibody-mediated pathobiologic effects on intact and injured nerves undergoing repair are discussed.

Diffusion tensor imaging to assess axonal regeneration in peripheral nerves

Development of outcome measures to assess ongoing nerve regeneration in the living animal that can be translated to human can provide extremely useful tools for monitoring the effects of therapeutic interventions to promote nerve regeneration. Diffusion tensor imaging (DTI), a magnetic resonance based technique, provides image contrast for nerve tracts and can be applied serially on the same subject with potential to monitor nerve fiber content. In this study, we examined the use of ex vivo high-resolution DTI for imaging intact and regenerating peripheral nerves in mice and correlated the MRI findings with electrophysiology and histology. DTI was done on sciatic nerves with crush, without crush, and after complete transection in different mouse strains. DTI measures, including fractional anisotropy (FA), parallel diffusivity, and perpendicular diffusivity were acquired and compared in segments of uninjured and crushed/transected nerves and correlated with morphometry. A comparison of axon regeneration after sciatic nerve crush showed a comparable pattern of regeneration in different mice strains. FA values were significantly lower in completely denervated nerve segments compared to uninjured sciatic nerve and this signal was restored toward normal in regenerating nerve segments (crushed nerves). Histology data indicate that the FA values and the parallel diffusivity showed a positive correlation with the total number of regenerating axons. These studies suggest that DTI is a sensitive measure of axon regeneration in mouse models and provide basis for further development of imaging technology for application to living animals and humans.

Structural requirements of anti-GD1a antibodies determine their target specificity

The acute motor axonal neuropathy (AMAN) variant of Guillain-Barré syndrome (GBS) is associated with anti-GD1a and anti-GM1 IgG antibodies. The basis of preferential motor nerve injury in this disease is not clear, however, because biochemical studies demonstrate that sensory and motor nerves express similar quantities of GD1a and GM1 gangliosides. To elucidate the pathophysiology of AMAN, we have developed several monoclonal antibodies (mAbs) with GD1a reactivity and reported that one mAb, GD1a-1, preferentially stained motor axons in human and rodent nerves. To understand the basis of this preferential motor axon staining, several derivatives of GD1a were generated by various chemical modifications of N-acetylneuraminic (sialic) acid residues (GD1a NeuAc 1-amide, GD1a NeuAc ethyl ester, GD1a NeuAc 1-alcohol, GD1a NeuAc 1-methyl ester, GD1a NeuAc 7-alcohol, GD1a NeuAc 7-aldehyde) on this ganglioside. Binding of anti-GD1a mAbs and AMAN sera with anti-GD1a Abs to these derivatives was examined. Our results indicate that mAbs with selective motor axon staining had a distinct pattern of reactivity with GD1a-derivatives compared to mAbs that stain both motor and sensory axons. The fine specificity of the anti-GD1a antibodies determines their motor selectivity, which was validated by cloning a new mAb (GD1a-E6) with a chemical and immunocytochemical binding pattern similar to that of GD1a-1 but with two orders of magnitude higher affinity. Control studies indicate that selective binding of mAbs to motor nerves is not due to differences in antibody affinity or ceramide structural specificity. Since GD1a-reactive mAb with preferential motor axon staining showed similar binding to sensory- and motor nerve-derived GD1a in a solid phase assay, we generated computer models of GD1a based on binding patterns of different GD1a-reactive mAbs to different GD1a-derivatives. These modelling studies suggest that critical GD1a epitopes recognized by mAbs are differentially expressed in motor and sensory nerves. The GD1a-derivative binding patterns of AMAN sera resembled those with motor-specific mAbs. On the basis of these findings we postulate that both the fine specificity and ganglioside orientation/exposure in the tissues contribute to target recognition by anti-ganglioside antibodies and this observation provides one explanation for preferential motor axon injury in AMAN.

Magnetic resonance imaging of mouse skeletal muscle to measure denervation atrophy

We assessed the potential of different MRI measures to detect and quantify skeletal muscle changes with denervation in two mouse models of denervation/neurogenic atrophy. Acute complete denervation and chronic partial denervation were examined in calf muscles after sciatic nerve axotomy and in transgenic SOD1(G93A) mice, respectively. Serial T(2), diffusion tensor, and high resolution anatomical images were acquired, and compared to behavioral, histological, and electrophysiological data. Increase in muscle T(2) signal was first detected after sciatic nerve axotomy. Progressive muscle atrophy could be monitored with MRI-based volume measurements, which correlated strongly with postmortem muscle mass measurements. Significant increase in muscle fractional anisotropy and decreases in secondary and tertiary eigenvalues obtained from diffusion tensor imaging (DTI) were observed after denervation. In SOD1(G93A) animals, muscle denervation was detected by elevated muscle T(2) and atrophy in the medial gastrocnemius at 10 weeks. Changes in T(2) and muscle volume were first observed in medial gastrocnemius and later in other calf muscles. Alterations in secondary and tertiary eigenvalues obtained from DTI were first observed in tibialis anterior and medial gastrocnemius muscles at age 12 weeks. We propose that MRI of skeletal muscle is a sensitive surrogate outcome measure of denervation atrophy in animal models of neuromuscular disorders, with potential applicability in preclinical therapeutic screening studies in rodents.

Anti-ganglioside antibodies alter presynaptic release and calcium influx

Acute motor axonal neuropathy (AMAN) variant of Guillain-Barré syndrome is often associated with IgG anti-GM1 and -GD1a antibodies. The pathophysiological basis of antibody-mediated selective motor nerve dysfunction remains unclear. We investigated the effects of IgG anti-GM1 and -GD1a monoclonal antibodies (mAbs) on neuromuscular transmission and calcium influx in hemidiaphragm preparations and in cultured neurons, respectively, to elucidate mechanisms of Ab-mediated muscle weakness. Anti-GM1 and -GD1a mAbs depressed evoked quantal release to a significant yet different extent, without affecting postsynaptic currents. At equivalent concentrations, anti-GD1b, -GT1b, or sham mAbs did not affect neuromuscular transmission. At fourfold higher concentration, an anti-GD1b mAb (specificity described in immune sensory neuropathies) induced completely reversible blockade. In neuronal cultures, anti-GM1 and -GD1a mAbs significantly reduced depolarization-induced calcium influx. In conclusion, different anti-ganglioside mAbs induce distinct effects on presynaptic transmitter release by reducing calcium influx, suggesting that this is one mechanism of antibody-mediated muscle weakness in AMAN.

Neurologic Symptoms and Neuropathologic Antibodies in Poultry Workers Exposed to Campylobacter jejuni

OBJECTIVES

To examine associations between occupational exposure to live poultry with Campylobacter exposure, Campylobacter-associated neurologic symptoms, and neuropathologic antibodies.

METHODS

Questionnaires, serum samples, and stool specimens were collected from 20 poultry workers and 40 community referents. Campylobacter exposure was evaluated by stool culture and serum antibodies; neurologic symptoms were assessed by questionnaire; and neuropathologic antibodies were measured by serum anti-glycolipid antibody concentrations.

RESULTS

Poultry workers had significantly higher anti-Campylobacter immunoglobulin G titers compared with that of referents (P < 0.05); they were significantly more likely to report multiple Campylobacter-associated neurologic symptoms; and male poultry workers had a higher point risk estimate for detectable neuropathologic anti-glycolipid immunoglobulin G titers (P = 0.07) compared with male referents.

CONCLUSIONS

These data suggest that poultry workers are at elevated risk of Campylobacter exposure and may be at elevated risk for Campylobacter-associated neurologic sequelae.

Passive immunization with anti-ganglioside antibodies directly inhibits axon regeneration in an animal model

Recent studies have proposed that neurite outgrowth is influenced by specific nerve cell surface gangliosides, which are sialic acid-containing glycosphingolipids highly enriched in the mammalian nervous system. For example, the endogenous lectin, myelin-associated glycoprotein (MAG), is reported to bind to axonal gangliosides (GD1a and GT1b) to inhibit neurite outgrowth. Clustering of gangliosides in the absence of inhibitors such as MAG is also shown to inhibit neurite outgrowth in culture. In some human autoimmune PNS and CNS disorders, autoantibodies against GD1a or other gangliosides are implicated in pathophysiology. Because of neurobiological and clinical relevance, we asked whether anti-GD1a antibodies inhibit regeneration of injured axons in vivo. Passive transfer of anti-GD1a antibody severely inhibited axon regeneration after PNS injury in mice. In mutant mice with altered ganglioside or complement expression, inhibition by antibodies was mediated directly through GD1a and was independent of complement-induced cytolytic injury. The impaired regenerative responses and ultrastructure of injured peripheral axons mimicked the abortive regeneration typically seen after CNS injury. These data demonstrate that inhibition of axon regeneration is induced directly by engaging cell surface gangliosides in vivo and imply that circulating autoimmune antibodies can inhibit axon regeneration through neuronal gangliosides independent of endogenous regeneration inhibitors such as MAG.

Comparison of different brands of IVIg in an in vitro model of immune neuropathy

Intravenous immunoglobulin (IVIg) is used for the treatment of a number of autoimmune neurological disorders. Whether different brands of IVIg or different lots of the same brand are comparably efficacious for the treatment of neurological disorders is not clear. To examine this issue we compared the efficacy of different brands and/or lots of IVIg in a cell culture model of immune neuropathy. We report that products examined were equally effective and there was no lot-to-lot variability in our experimental model. These findings support the notion that efficacy of different IVIg products is comparable in a standardized model.

Myelin-associated glycoprotein and complementary axonal ligands, gangliosides, mediate axon stability in the CNS and PNS: neuropathology and behavioral deficits in single- and double-null mice

Complementary interacting molecules on myelin and axons are required for long-term axon-myelin stability. Their disruption results in axon degeneration, contributing to the pathogenesis of demyelinating diseases. Myelin-associated glycoprotein (MAG), a minor constituent of central and peripheral nervous system myelin, is a member of the Siglec family of sialic acid-binding lectins and binds to gangliosides GD1a and GT1b, prominent molecules on the axon surface. Mice lacking the ganglioside biosynthetic gene Galgt1 fail to express complex gangliosides, including GD1a and GT1b. In the current studies, CNS and PNS histopathology and behavior of Mag-null, Galgt1-null, and double-null mice were compared on the same mouse strain background. When back-crossed to >99% C57BL/6 strain purity, Mag-null mice demonstrated marked CNS, as well as PNS, axon degeneration, in contrast to prior findings using mice of mixed strain background. On the same background, Mag- and Galgt1-null mice exhibited quantitatively and qualitatively similar CNS and PNS axon degeneration and nearly identical decreases in axon diameter and neurofilament spacing. Double-null mice had qualitatively similar changes. Consistent with these findings, Mag- and Galgt1-null mice had similar motor behavioral deficits, with double-null mice only modestly more impaired. Despite their motor deficits, Mag- and Galgt1-null mice demonstrated hyperactivity, with spontaneous locomotor activity significantly above that of wild type mice. These data demonstrate that MAG and complex gangliosides contribute to axon stability in both the CNS and PNS. Similar neuropathological and behavioral deficits in Galgt1-, Mag-, and double-null mice support the hypothesis that MAG binding to gangliosides contributes to long-term axon-myelin stability.

Overlap of pathology in paralytic rabies and axonal Guillain-Barre syndrome

We describe clinical and pathological features of a case of paralytic rabies with acute axonal neuropathy that closely resembled axonal Guillain-Barre syndrome. This case emphasizes that there is overlap of both clinical and pathological features in paralytic rabies and axonal Guillain-Barre syndrome. These findings raise the possibility that infectious and autoimmune etiologies can lead to similar morphological changes in the nerves.

An anti-ganglioside antibody-secreting hybridoma induces neuropathy in mice

Immune responses against gangliosides are strongly implicated in the pathogenesis of some variants of Guillain-Barré syndrome (GBS). For example, IgG antibodies against GM1, GD1a, and related gangliosides are frequently present in patients with post-Campylobacter acute motor axonal neuropathy (AMAN) variant of GBS, and immunization of rabbits with GM1 has produced a model of AMAN. However, the role of anti-ganglioside antibodies in GBS continues to be debated because of lack of a passive transfer model. We recently have raised several monoclonal IgG anti-ganglioside antibodies. We passively transfer these antibodies by intraperitoneal hybridoma implantation and by systemic administration of purified anti-ganglioside antibodies in mice. Approximately half the animals implanted with an intraperitoneal clone of anti-ganglioside antibody-secreting hybridoma developed a patchy, predominantly axonal neuropathy affecting a small proportion of nerve fibers. In contrast to hybridoma implantation, passive transfer with systemically administered anti-ganglioside antibodies did not cause nerve fiber degeneration despite high titre circulating antibodies. Blood-nerve barrier studies indicate that animals implanted with hybridoma had leaky blood-nerve barrier compared to mice that received systemically administered anti-ganglioside antibodies. Our findings suggest that in addition to circulating antibodies, factors such as antibody accessibility and nerve fiber resistance to antibody-mediated injury play a role in the development of neuropathy.

Myelin-associated glycoprotein (Siglec-4) expression is progressively and selectively decreased in the brains of mice lacking complex gangliosides

Myelin-associated glycoprotein (MAG, Siglec-4) is a quantitatively minor membrane component expressed preferentially on the innermost myelin wrap, adjacent to the axon. It stabilizes myelin-axon interactions by binding to complementary ligands on the axolemma. MAG, a member of the Siglec family of sialic acid-binding lectins, binds specifically to gangliosides GD1a and GT1b, which are the major sialoglycoconjugates on mammalian axons. Mice with a disrupted Galgt1 gene lack UDP-GalNAc:GM3/GD3 N-acetylgalactosaminyltransferase (GM2/GD2 synthase) and fail to express complex brain gangliosides, including GD1a and GT1b, instead expressing a comparable amount of the simpler gangliosides GM3, GD3, and O-acetyl-GD3. Galgt1-null mice produce similar amounts of total myelin compared to wild-type mice, but as the mice age, they exhibit axon degeneration and dysmyelination with accompanying motor behavioral deficits. Here we report that Galgt1-null mice display progressive and selective loss of MAG from the brain. At 1.5 months of age, MAG expression was similar in Galgt1-null and wild-type mice. However, by 6 months of age MAG was decreased approximately 60% and at 12 months of age approximately 70% in Galgt1-null mice compared to wild-type littermates. Expression of the major myelin proteins (myelin basic protein and proteolipid protein) was not reduced in Galgt1-null mice compared to wild type. MAG mRNA expression was the same in 12-month-old Galgt1-null compared to wild-type mice, an age at which MAG protein expression was markedly reduced. We conclude that the maintenance of MAG protein levels depends on the presence of complex gangliosides, perhaps due to enhanced stability when MAG on myelin binds to its complementary ligands, GD1a and GT1b, on the apposing axon surface.

Anti-ganglioside antibody-mediated neuronal cytotoxicity and its protection by intravenous immunoglobulin: implications for immune neuropathies

Antibodies against GD1a, GM1 and related gangliosides are frequently present in patients with the motor variant of Guillain-Barré syndrome (GBS), and their pathological role in this variant of GBS is now widely accepted. However, two basic issues related to anti-ganglioside antibody-mediated neural injury are not completely resolved: (i) some anti-ganglioside antibodies can cross-react with glycoproteins and therefore the nature of antigens targeted by these antibodies is not well established; and (ii) although pathological studies suggest that complement activation occurs in GBS, experimental data for the role of complement remain inconclusive. To address these issues, we developed and characterized a simple anti-ganglioside antibody-mediated cytotoxicity assay. Our results demonstrate first, that both GBS sera containing anti-ganglioside antibodies and monoclonal anti-ganglioside antibodies cause neuronal cell lysis by targeting specific cell surface gangliosides, and secondly, that this cell lysis is complement dependent. In this assay, the GD1a cell membrane pool appears to be more susceptible to anti-ganglioside antibody-mediated injury than the GM1 pool. Further, human intravenous immunoglobulin (i.v.Ig), now a standard treatment for GBS, significantly decreased cytotoxicity in this assay. Our data indicate that the mechanisms of i.v.Ig-mediated protection in this assay include anti-idiotypic antibodies and downregulation of complement activation. This simple cytotoxicity assay can potentially be used for screening of (i) pathogenic anti-ganglioside antibodies in patients with immune-mediated neuropathies; and (ii) new/experimental therapies to prevent anti-ganglioside antibody-mediated neural injury.

Localization of major gangliosides in the PNS: implications for immune neuropathies

Antibodies targeting major gangliosides that are broadly distributed in the nervous system are sometimes associated with clinical symptoms that imply selective nerve damage. For example, anti-GD1a antibodies are associated with acute motor axonal neuropathy (AMAN), a form of Guillain-Barré syndrome that selectively affects motor nerves, despite reports that GD1a is present in human axons and myelin and is not expressed differentially in motor versus sensory roots. We used a series of high-affinity monoclonal antibodies (mAbs) against the major nervous system gangliosides GM1, GD1a, GD1b and GT1b to test whether any of them bind motor or sensory fibres differentially in rodent and human peripheral nerves. The following observations were made. (i) Some of the anti-GD1a antibodies preferentially stained motor fibres, supporting the association of human anti-GD1a antibodies with predominant motor neuropathies such as AMAN. (ii) A GD1b antibody preferentially stained the large dorsal root ganglion (DRG) neurones, in keeping with the proposed role of human anti-GD1b antibodies in sensory ataxic neuropathies. (iii) Two mAbs with broad structural cross-reactivity bound to both gangliosides and peripheral nerve proteins. (iv) Myelin was poorly stained; all clones stained axons nearly exclusively. Our findings suggest that anti-ganglioside antibody fine specificity as well as differences in ganglioside accessibility in axons and myelin influence the selectivity of injury to different fibre systems and cell types in human autoimmune neuropathies.

Anti-myelin-associated glycoprotein antibodies alter neurofilament spacing

Axon calibre is crucial to efficient impulse transmission in the peripheral nervous system. Neurofilament numbers determine gross axonal diameter, but intra-axonal distribution depends on the phosphorylation status of neurofilament sidearms. Myelin-associated glycoprotein (MAG) has been implicated in the signalling cascade controlling neurofilament phosphorylation and hence in the control of axon calibre. In an electron microscopic morphometric study we measured nearest neighbour neurofilament distances (NNND) in the axons of sural nerves from patients with anti-MAG paraproteinaemic neuropathies and compared these with normal human sural nerves and those from patients with Guillain-Barré syndrome or chronic inflammatory demyelinating polyradiculoneuropathy. Axon calibre was similar in all groups. In normal human sural nerves, axonal NNND was correlated with axonal diameter (r = 0.56). In diseased axons this correlation did not exist. The NNND was significantly reduced in demyelinated axons (30.5+/-2.2 nm) and those with widely spaced myelin (28.9+/-1.3 nm) from patients with anti-MAG antibodies compared with normal axons from normal patients (39.8+/- 3.2 nm) or those with demyelinating neuropathy (35.8+/-4.6 nm). This reinforces the hypothesis that MAG is involved in the control of neurofilament spacing through sidearm phosphorylation and demonstrates a MAG-mediated pathogenic effect of the anti-MAG antibody in peripheral nerves.

The wound healing properties of Channa striatus-cetrimide cream-wound contraction and glycosaminoglycan measurement

Haruan has been proved to influence the different phases of wound healing process. The current research focuses on the effects of haruan on the different constituents of extracellular matrix of healing wounds in normal and diabetic rats. Anaesthetized normal and streptozotocin induced diabetic rats were provided with excision wounds at the back and then animals were divided into four groups as: group 1, wounds treated with cetrimide+haruan cream; group 2, wounds treated with haruan cream; group 3, wounds treated with cetrimide (commercial) cream; and group 4, wounds untreated and served as control. Animals were sacrificed after 3, 6, 9 and 12 days. These wounds were used to determine the hexosamine, protein, uronic acid and glycosaminoglycan contents and the wound contraction. The results suggested a marked increase (P<0.05) in the uronic acid, hexosamine and dermatan sulfate contents on day 3 of group 1 when compared with groups 2-4. Wound contraction of group 1 was also markedly enhanced of group 1 (P<0.01) when compared with groups 2- 4. On the basis of these results, we conclude that haruan enhances the synthesis of different glycosaminoglycans in healing wounds, which are the first component of extracellular matrix to be synthesized during the wound healing process. The enhanced levels of glycosaminoglycans may help in the formation of a resistant scar and enhanced wound contraction represents the positive influence of haruan on the fibroplastic phase of wound healing.

High-affinity anti-ganglioside IgG antibodies raised in complex ganglioside knockout mice: reexamination of GD1a immunolocalization

Gangliosides, sialic acid-bearing glycosphingolipids, are highly enriched in the vertebrate nervous system. Anti-ganglioside antibodies are associated with various human neuropathies, although the pathogenicity of these antibodies remains unproven. Testing the pathogenic role of anti-ganglioside antibodies will be facilitated by developing high-affinity IgG-class complement-fixing monoclonal anti-bodies against major brain gangliosides, a goal that has been difficult to achieve. In this study, mice lacking complex gangliosides were used as immune-naive hosts to raise anti-ganglioside antibodies. Wild-type mice and knockout mice with a disrupted gene for GM2/GD2 synthase (UDP-N-acetyl-D-galactosamine : GM3/GD3 N-acetyl-D-glactosaminyltransferase) were immunized with GD1a conjugated to keyhole limpet hemocyanin. The knockout mice produced a vigorous anti-GD1a IgG response, whereas wildtype littermates failed to do so. Fusion of spleen cells from an immunized knockout mouse with myeloma cells yielded numerous IgG anti-GD1a antibody-producing colonies. Ganglioside binding studies revealed two specificity classes; one colony representing each class was cloned and characterized. High-affinity monoclonal antibody was produced by each hybridoma : an IgG1 that bound nearly exclusively to GD1a and an IgG2b that bound GD1a, GT1b, and GT1aalpha. Both antibodies readily readily detected gangliosides via ELISA, TLC immune overlay, immunohistochemistry, and immunocytochemistry. In contrast to prior reports using anti-GD1a and anti-GT1b IgM class monoclonal antibodies, the new antibodies bound avidly to granule neurons in brain tissue sections and cell cultures. Mice lacking complex gangliosides are improved hosts for raising high-affinity, high-titer anti-ganglioside IgG antibodies for probing for the distribution and physiology of gangliosides and the pathophysiology of anti-ganglioside antibodies.