Adult-onset Krabbe disease presenting with an isolated form of peripheral neuropathy.

INTRODUCTION: Adult-onset Krabbe disease is clinically rare and usually affects the pyramidal tracts in the central nervous system. Patients develop a spastic gait, and peripheral neuropathy sometimes occurs simultaneously. METHODS: A 55-year-old woman with consanguineous parents developed slowly progressive, asymmetric muscle weakness and atrophy in her forearms, while her ability to walk remained unaffected without pyramidal tract signs after onset at age 51 years. RESULTS: Nerve conduction studies demonstrated an asymmetric demyelinating-type peripheral neuropathy, and sural nerve biopsy documented reduced myelinated nerve fiber density with uniformly thin myelin sheaths, suggesting hypomyelination. Brain MRI demonstrated minor white-matter injury along the optic radiations, which was associated with asymptomatic, mild, prolonged latency on visual evoked potentials. Laboratory analysis documented low enzyme activity of galactocerebrosidase (GALC) and a known mutation of the GALC gene. CONCLUSION: Isolated peripheral neuropathy occurs very rarely in adult-onset Krabbe disease. Muscle Nerve 54: 152-157, 2016.

[Successful corticosteroid therapies in a case of acute motor, sensory, autonomic neuropathy after cytomegalovirus infection].

We report a rare case of autonomic neuropathy associated with cytomegalovirus (CMV) infection. The patient, a 53-year-old male, was admitted to our hospital because of prolonged fever, headache and neck stiffness followed by urinary retention. Cerebrospinal fluid examination revealed pleocytosis (219/mm(3), predominantly lymphocytes) with a markedly increased protein level (217 mg/dl) and serum IgM anti-CMV antibody was detected. While his meningitic symptoms gradually improved after intravenous administration of ganciclovir, he complained of numbness in the extremities and difficulty in walking. Neurologically, marked orthostatic hypotension, glove and stocking type of paresthesia, severe muscle weakness in extremities, and neurogenic atonic bladder were noted. Nerve conduction studies showed normal except for F-waves, which were absent in the left tibial nerve. A sural nerve specimen appeared normal in both myelinated and unmyelinated fibers. He was given immunological therapies such as corticosteroid and intravenous high dose immunoglobulin therapies. After corticosteroid therapies, not only sensory and motor symptoms but also autonomic symptoms remarkably improved. Of the anti-ganglioside antibodies, IgM anti-GM1 antibody and IgM anti-GM2 antibody were detected. Although some cases with Guillain-Barré syndrome preceded by CMV infection have been reported, few cases with autonomic neuropathy have been described in association with successful corticosteroid therapies.

Accelerated tumor growth mediated by sublytic levels of antibody-induced complement activation is associated with activation of the PI3K/AKT survival pathway.

PURPOSE: We addressed the possibility that low levels of tumor cell-bound antibodies targeting gangliosides might accelerate tumor growth. EXPERIMENTAL DESIGN: To test this hypothesis, we treated mice with a range of monoclonal antibody (mAb) doses against GM2, GD2, GD3, and CD20 after challenge with tumors expressing these antigens and tested the activity of the same mAbs in vitro. We also explored the mechanisms behind the complement-mediated tumor growth acceleration that we observed and an approach to overcome it. RESULTS: Serologically detectable levels of IgM-mAb against GM2 are able to delay or prevent tumor growth of high GM2 expressing cell lines both in vitro and in a SCID mouse model, whereas very low levels of this mAb resulted in slight but consistent acceleration of tumor growth in both settings. Surprisingly, this is not restricted to IgM mAb targeting GM2 but consistent against an IgG mAb targeting GD3 as well. These findings were mirrored by in vitro studies with antibodies against these antigens as well as GD2 and CD20 (with Rituxan), and shown to be complement-dependent in all cases. Complement-mediated accelerated growth of cultured tumor cell lines initiated by low mAb levels was associated with activation of the phosphoinositide 3-kinase (PI3K)/AKT survival pathway and significantly elevated levels of both p-AKT and p-PRAS40. This complement-mediated PI3K activation and accelerated tumor growth in vitro and in vivo are eliminated by PI3K inhibitors NVP-BEZ235 and Wortmannin. These PI3K inhibitors also significantly increased efficacy of high doses of these four mAbs. CONCLUSION: Our findings suggest that manipulation of the PI3K/AKT pathway and its signaling network can significantly increase the potency of passively administered mAbs and vaccine-induced antibodies targeting a variety of tumor cell surface antigens.

Knock-down of HEXA and HEXB genes correlate with the absence of the immunostimulatory function of HSC-derived dendritic cells.

In an attempt to investigate whether the genetic defect in the HEXA and HEXB genes (which causes the absence of the lysosomal ß-N-acetyl-hexosaminidase), are related to the wide inflammation in GM2 gangliosidoses (Tay-Sachs and Sandhoff disease), we have chosen the dendritic cells (DCs) as a study model. Using the RNA interference approach, we generated an in vitro model of HEXs knock-down immunogenic DCs (i-DCs) from CD34(+)-haemopoietic stem cells (CD34(+)-HSCs), thus mimicking the Tay-Sachs (HEXA-/-) and Sandhoff (HEXB-/-) cells. We showed that the absence of ß-N-acetyl-hexosaminidase activity does not alter the differentiation of i-DCs from HSCs, but it is critical for the activation of CD4(+)T cells because knock-down of HEXA or HEXB gene causes a loss of function of i-DCs. Notably, the silencing of the HEXA gene had a stronger immune inhibitory effect, thereby indicating a major involvement of ß-N-acetyl-hexosaminidase A isoenzyme within this mechanism.

Thymic alterations in GM2 gangliosidoses model mice.

BACKGROUND: Sandhoff disease is a lysosomal storage disorder characterized by the absence of ß-hexosaminidase and storage of GM2 ganglioside and related glycolipids. We have previously found that the progressive neurologic disease induced in Hexb(-/-) mice, an animal model for Sandhoff disease, is associated with the production of pathogenic anti-glycolipid autoantibodies. METHODOLOGY/PRINCIPAL FINDINGS: In our current study, we report on the alterations in the thymus during the development of mild to severe progressive neurologic disease. The thymus from Hexb(-/-) mice of greater than 15 weeks of age showed a marked decrease in the percentage of immature CD4(+)/CD8(+) T cells and a significantly increased number of CD4(+)/CD8(-) T cells. During involution, the levels of both apoptotic thymic cells and IgG deposits to T cells were found to have increased, whilst swollen macrophages were prominently observed, particularly in the cortex. We employed cDNA microarray analysis to monitor gene expression during the involution process and found that genes associated with the immune responses were upregulated, particularly those expressed in macrophages. CXCL13 was one of these upregulated genes and is expressed specifically in the thymus. B1 cells were also found to have increased in the thy mus. It is significant that these alterations in the thymus were reduced in FcRγ additionally disrupted Hexb(-/-) mice. CONCLUSIONS/SIGNIFICANCE: These results suggest that the FcRγ chain may render the usually poorly immunogenic thymus into an organ prone to autoimmune responses, including the chemotaxis of B1 cells toward CXCL13.

Elevated levels of select gangliosides in T cells from renal cell carcinoma patients is associated with T cell dysfunction.

Increased expression of gangliosides by different tumor types including renal cell carcinoma (RCC) is thought to contribute to the immune suppression observed in cancer patients. In this study, we report an increase in apoptotic T cells from RCC patients compared with T cells from normal donors that coincided with the detection of T cells staining positive for GM2 and that the apoptosis was predominantly observed in the GM2(+) but not the GM2(-) T cell population. Ganglioside shedding from tumor rather than endogenous production accounts for GM2(+) T cells since there was no detectable level of mRNA for GM2 synthase in RCC patient T cells and in T cells from normal healthy donors after incubation with either purified GM2 or supernatant from RCC cell lines despite their staining positive for GM2. Moreover, reactive oxygen species as well as activated caspase 3, 8, and 9 were predominantly elevated in GM2(+) but not GM2(-) T cells. Similarly, increased staining for GD2 and GD3 but not GD1a was detected with patient T cells with elevated levels of apoptosis in the GD2(+) and GD3(+) cells. These findings suggest that GM2, GD2, and GD3 play a significant role in immune dysfunction observed in RCC patient T cells.

Sensory loss in multifocal motor neuropathy: a clinical and electrophysiological study.

Some patients fulfilling the criteria for the diagnosis of multifocal motor neuropathy with conduction block (MMN-CB) at the onset of disease may subsequently develop a sensory loss associated with electrophysiological sensory abnormalities. The latter could represent an overlap between MMN-CB and multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy. The objective was to specify the features of MMN-CB with sensory loss (MMN-CB-Se). Five patients in a series of 11 consecutive patients who fulfilled the criteria of the American Association of Neuromuscular and Electrodiagnostic Medicine for MMN-CB at the first examination and were treated periodically with intravenous immunoglobulin (IVIg) developed sensory loss in the course of the disease. In these five patients we compared the clinical, laboratory, and electrophysiological features found after the development of sensory loss with those at the first examination. The mean time to appearance of objective sensory signs was 7.2 years. In three of the five patients the sensory loss was preceded by intermittent paresthesias in the same nerve territories as the motor involvement. The most frequent electrophysiological abnormality was amplitude reduction of sensory nerve action potentials. There were no bilateral or symmetrical clinical and electrophysiological sensory abnormalities. Anti-GM1 IgM antibodies were positive in four patients. MMN-CB-Se could be an overlap between MMN-CB and MADSAM. It shares the distribution of the sensory disorders encountered in MADSAM, but it is closer to MMN-CB on clinical and therapeutic levels. Study of more patients would be useful to classify this subgroup more accurately.

Anti-GM2 gangliosides IgM paraprotein induces neuromuscular block without neuromuscular damage.

We analyzed the effect on the mouse neuromuscular synapses of a human monoclonal IgM, which binds specifically to gangliosides with the common epitope [GalNAc beta 1-4Gal(3-2 alpha NeuAc)beta 1-]. We focused on the role of the complement. Evoked neurotransmission was partially blocked by IgM both acutely (1 h) and chronically (10 days). Transmission electron microscopy shows important nerve terminal growth and retraction remodelling though axonal injury can be ruled out. Synapses did not show mouse C5b-9 immunofluorescence and were only immunolabelled when human complement was added. Therefore, the IgM-induced synaptic changes occur without complement-mediated membrane attack.

Possible role of autoantibodies in the pathophysiology of GM2 gangliosidoses.

Mice containing a disruption of the Hexb gene have provided a useful model system for the study of the human lysosomal storage disorder known as Sandhoff disease (SD). Hexb(-/-) mice rapidly develop a progressive neurologic disease of ganglioside GM2 and GA2 storage. Our study revealed that the disease states in this model are associated with the appearance of antiganglioside autoantibodies. Both elevation of serum antiganglioside autoantibodies and IgG deposition to CNS neurons were found in the advanced stages of the disease in Hexb(-/-) mice; serum transfer from these mice showed IgG binding to neurons. To determine the role of these autoantibodies, the Fc receptor gamma gene (FcR gamma) was additionally disrupted in Hexb(-/-) mice, as it plays a key role in immune complex-mediated autoimmune diseases. Clinical symptoms were improved and life spans were extended in the Hexb(-/-)FcR gamma(-/-) mice; the number of apoptotic cells was also decreased. The level of ganglioside accumulation, however, did not change. IgG deposition was also confirmed in the brain of an autopsied SD patient. Taken together, these findings suggest that the production of autoantibodies plays an important role in the pathogenesis of neuropathy in SD and therefore provides a target for novel therapies.