Norio Chihara

Interleukin 6 signaling promotes anti-aquaporin 4 autoantibody production from plasmablasts in neuromyelitis optica

Neuromyelitis optica (NMO) is an inflammatory disease affecting the optic nerve and spinal cord, in which autoantibodies against aquaporin 4 (AQP4) water channel protein probably play a pathogenic role. Here we show that a B-cell subpopulation, exhibiting the CD19intCD27highCD38highCD180− phenotype, is selectively increased in the peripheral blood of NMO patients and that anti-AQP4 antibodies (AQP4-Abs) are mainly produced by these cells in the blood of these patients. These B cells showed the morphological as well as the phenotypical characteristics of plasmablasts (PB) and were further expanded during NMO relapse. We also demonstrate that interleukin 6 (IL-6), shown to be increased in NMO, enhanced the survival of PB as well as their AQP4-Ab secretion, whereas the blockade of IL-6 receptor (IL-6R) signaling by anti–IL-6R antibody reduced the survival of PB in vitro. These results indicate that the IL-6–dependent B-cell subpopulation is involved in the pathogenesis of NMO, thereby providing a therapeutic strategy for targeting IL-6R signaling.

Dysbiosis in the gut microbiota of patients with multiple sclerosis, with a striking depletion of species belonging to clostridia XIVa and IV clusters

The pathogenesis of multiple sclerosis (MS), an autoimmune disease affecting the brain and spinal cord, remains poorly understood. Patients with MS typically present with recurrent episodes of neurological dysfunctions such as blindness, paresis, and sensory disturbances. Studies on experimental autoimmune encephalomyelitis (EAE) animal models have led to a number of testable hypotheses including a hypothetical role of altered gut microbiota in the development of MS. To investigate whether gut microbiota in patients with MS is altered, we compared the gut microbiota of 20 Japanese patients with relapsing-remitting (RR) MS (MS20) with that of 40 healthy Japanese subjects (HC40) and an additional 18 healthy subjects (HC18). All the HC18 subjects repeatedly provided fecal samples over the course of months (158 samples in total). Analysis of the bacterial 16S ribosomal RNA (rRNA) gene by using a high-throughput culture-independent pyrosequencing method provided evidence of a moderate dysbiosis in the structure of gut microbiota in patients with MS. Furthermore, we found 21 species that showed significant differences in relative abundance between the MS20 and HC40 samples. On comparing MS samples to the 158 longitudinal HC18 samples, the differences were found to be reproducibly significant for most of the species. These taxa comprised primarily of clostridial species belonging to Clostridia clusters XIVa and IV and Bacteroidetes. The phylogenetic tree analysis revealed that none of the clostridial species that were significantly reduced in the gut microbiota of patients with MS overlapped with other spore-forming clostridial species capable of inducing colonic regulatory T cells (Treg), which prevent autoimmunity and allergies; this suggests that many of the clostridial species associated with MS might be distinct from those broadly associated with autoimmune conditions. Correcting the dysbiosis and altered gut microbiota might deserve consideration as a potential strategy for the prevention and treatment of MS.

Differential effects of fingolimod on B-cell populations in multiple sclerosis

Background: Fingolimod is an oral drug approved for multiple sclerosis (MS) with an ability to trap central memory T cells in secondary lymphoid tissues; however, its variable effectiveness in individual patients indicates the need to evaluate its effects on other lymphoid cells. Objective: To clarify the effects of fingolimod on B-cell populations in patients with MS. Methods: We analysed blood samples from 9 fingolimod-treated and 19 control patients with MS by flow cytometry, to determine the frequencies and activation states of naive B cells, memory B cells, and plasmablasts. Results: The frequencies of each B-cell population in peripheral blood mononuclear cells (PBMC) were greatly reduced 2 weeks after starting fingolimod treatment. Detailed analysis revealed a significant reduction in activated memory B cells (CD38int-high), particularly those expressing Ki-67, a marker of cell proliferation. Also, we noted an increased proportion of activated plasmablasts (CD138+) among whole plasmablasts, in the patients treated with fingolimod. Conclusions: The marked reduction of Ki-67+ memory B cells may be directly linked with the effectiveness of fingolimod in treating MS. In contrast, the relative resistance of CD138+ plasmablasts to fingolimod may be of relevance for understanding the differential effectiveness of fingolimod in individual patients.

Plasmablasts as Migratory IgG-Producing Cells in the Pathogenesis of Neuromyelitis Optica

Neuromyelitis optica (NMO) is an inflammatory disease characterized by recurrent attacks of optic neuritis and myelitis. It is generally accepted that autoantibodies against aquaporin 4 water channel protein play a pathogenic role in neuromyelitis optica. We have recently reported that plasmablasts are increased in the peripheral blood of this autoimmune disease, and are capable of producing autoantibodies against aquaporin 4. Here, we demonstrate that CD138+HLA-DR+ plasmablasts, a subset of IgG-producing cells, are increased in the peripheral blood and are enriched among the cerebrospinal fluid (CSF) lymphocytes during the relapse of neuromyelitis optica. Notably, these CD138+HLA-DR+ plasmablasts overexpress CXCR3, whose ligands are present in the cerebrospinal fluid during the relapse of neuromyelitis optica. These results led us to speculate that plasmablasts producing anti-aquaporin 4 autoantibodies might traffic toward the central nervous system (CNS). Furthermore, we performed single-cell sorting of plasmablasts from peripheral blood and CSF samples from NMO and sequenced the complementarity-determining regions (CDRs) of the IgG heavy chain expressed by the sorted plasmablast clones. There were high frequencies of mutations in the CDRs compared with framework regions, indicating that these plasmablast clones would represent a post-germinal center B-cell lineage. Consistent with the preceding results, the plasmablast clones from the peripheral blood shared the same CDR sequences with the clones from the CSF. These results indicate that IgG-producing plasmablasts, which are guided by helper T-cells, may migrate from the peripheral blood preferentially to the CSF. Since migratory plasmablasts could be involved in the inflammatory pathology of NMO, the B-cell subset and their migration might be an attractive therapeutic target.

Increase of Ki-67+ natural killer cells in multiple sclerosis patients treated with interferon-β and interferon-β combined with low-dose oral steroids

Interferon-β (IFN-β) is known to expand regulatory CD56(bright) natural killer (NK) cells in multiple sclerosis (MS). In this cross-sectional study we show that MS patients treated with IFN-β alone or in combination with low-dose prednisolone displayed increased proportion of all NK cell subsets in the active phase of the cell cycle (Ki-67+). There was no difference in NK cell apoptosis markers. In vitro experiments showed that both IFN-β and IFN-β in combination with corticosteroids increased the proportion of Ki-67(+) NK cells. This study, although limited, shows that treatment with IFN-β affects NK cell cycle without altering NK cell apoptosis in MS patients.

A case of multiple sclerosis who relapsed early after fingolimod therapy introduced

The patient was a 46-year-old woman having a history of multiple sclerosis (MS) for 14 years. She had been treated with interferon β-1b since 2001, but discontinued because of psychiatric problems in 2006. Thereafter relapses were observed 1-2 times a year, and EDSS became 2.5 to 6.5. In April 2012, relapse of MS was noticed and the patient received introduction of fingolimod (FTY) after methylprednisolone (mPSL) pulse therapy. Twenty days later, dysarthria and lower limb weakness were appeared. Brain MRI showed more than 20 several millimeter Gd enhanced lesions in periventricular white matter, juxta-cortical white matter, and cerebellum. Careful determination and observation are required upon the FTY administration into the MS with high frequency of relapse.

Videofluorographic detection of anti–muscle-specific kinase–positive myasthenia gravis

A 47-year-old woman with dysphagia and ptosis gradually developed dysarthria and muscular weakness. Magnetic resonance imaging, testing for anti-acetylcholine receptor antibodies, edrophonium chloride (EC) test, and electrophysiologic test revealed no abnormalities. A psychogenic reaction was suspected. Four months after disease onset, the patient presented to our hospital. In videofluoroscopic examination of swallowing (VF), there was no aspiration for swallowing of either liquid or soft food. It revealed, however, poor pharyngeal constriction, no epiglottis inversion, repeated swallowing movements, and large amounts of pharyngeal residue. Videofluoroscopic examination of swallowing after an intravenous injection of 10 mg EC showed improvements in all above observations; particularly, it was clear when swallowing soft food. Furthermore, the anti-muscle-specific kinase (MuSK) antibody titer was elevated, and anti-MuSK antibody-positive myasthenia gravis (MuSK-MG) was diagnosed. Thus VF during EC test may be helpful in diagnosing MuSK-MG in patients with dysphagia.

Dysregulated T cells in multiple sclerosis

Multiple exogenous signals received from cell surface molecules or cytokines play a significant role in altering the host immune response. In chronic autoimmune‐mediated diseases, such as multiple sclerosis (MS), immune cells, especially T cells, are involved in the long‐term pathophysiology. In the past few decades, mechanisms of pathogenic T‐cell involvement at the onset or relapse of disease have been highlighted. However, the factors controlling the disease course have yet to be elucidated because of the complexity of tissue environmental factors. In contrast, dysfunctional or exhausted T cells have been identified as distinct cell lineages in chronic inflammatory diseases, such as cancer or chronic viral infections that show regulatory T cell phenotypes; for example, expressing high levels of co‐inhibitory receptors. Regarding cell surface molecule expression, while co‐stimulatory molecules promote effector T‐cell function, co‐inhibitory molecules promote regulatory T‐cell function, limiting the inflammatory response. In MS, augmented activation of effector T cells as a result of the impairment of regulatory T‐cell function has been implicated. Thus, a comparison between these regulatory T cells in MS and dysfunctional T cells in cancer could provide clues to understand the mechanism of dysregulated T cells, resulting in sustained immune reactions in the long‐term disease course of MS. Furthermore, this reveals new immunomodulatory strategies to regain regulatory T‐cell function in MS.

Japanese WDR45 de novo mutation diagnosed by exome analysis: A case report

A 40‐year‐old Japanese woman presented with slowly progressing parkinsonism in adulthood. She had a history of epilepsy with intellectual disability in childhood. In a head magnetic resonance scan, T2‐weighted imaging showed low signal intensity areas in the globus pallidus and the substantia nigra; T1‐weighted imaging showed a halo in the nigra. Because the patients symptoms and history were similar to those of patients with neurodegeneration with brain iron accumulation, we ran an exome analysis to investigate neurodegeneration with brain iron accumulation‐associated genes. We identified a c.700 C>T (p.Arg 234*) mutation in exon 9 of the WDR45 gene, which had not been reported in Japanese patients with beta‐propeller protein‐associated neurodegeneration (a neurodegeneration with brain iron accumulation subtype). Sanger sequencing confirmed a heterozygous mutation in this patient that was absent in both her parents, so it was judged to be a de novo nonsense mutation.