Differentiated pattern of complement system activation between MOG-IgG-associated disease and AQP4-IgG-positive neuromyelitis optica spectrum disorder.

Background: Myelin oligodendrocyte glycoprotein antibody (MOG) immunoglobulin G (IgG)-associated disease (MOGAD) has clinical and pathophysiological features that are similar to but distinct from those of aquaporin-4 antibody (AQP4-IgG)-positive neuromyelitis optica spectrum disorders (AQP4-NMOSD). MOG-IgG and AQP4-IgG, mostly of the IgG1 subtype, can both activate the complement system. Therefore, we investigated whether the levels of serum complement components, regulators, and activation products differ between MOGAD and AQP4-NMOSD, and if complement analytes can be utilized to differentiate between these diseases. Methods: The sera of patients with MOGAD (from during an attack and remission; N=19 and N=9, respectively) and AQP4-NMOSD (N=35 and N=17), and healthy controls (N=38) were analyzed for C1q-binding circulating immune complex (CIC-C1q), C1 inhibitor (C1-INH), factor H (FH), C3, iC3b, and soluble terminal complement complex (sC5b-9). Results: In attack samples, the levels of C1-INH, FH, and iC3b were higher in the MOGAD group than in the NMOSD group (all, p<0.001), while the level of sC5b-9 was increased only in the NMOSD group. In MOGAD, there were no differences in the concentrations of complement analytes based on disease status. However, within AQP4-NMOSD, remission samples indicated a higher C1-INH level than attack samples (p=0.003). Notably, AQP4-NMOSD patients on medications during attack showed lower levels of iC3b (p<0.001) and higher levels of C3 (p=0.008), C1-INH (p=0.004), and sC5b-9 (p<0.001) compared to those not on medication. Among patients not on medication at the time of attack sampling, serum MOG-IgG cell-based assay (CBA) score had a positive correlation with iC3b and C1-INH levels (rho=0.764 and p=0.010, and rho=0.629 and p=0.049, respectively), and AQP4-IgG CBA score had a positive correlation with C1-INH level (rho=0.836, p=0.003). Conclusions: This study indicates a higher prominence of complement pathway activation and subsequent C3 degradation in MOGAD compared to AQP4-NMOSD. On the other hand, the production of terminal complement complexes (TCC) was found to be more substantial in AQP4-NMOSD than in MOGAD. These findings suggest a strong regulation of the complement system, implying its potential involvement in the pathogenesis of MOGAD through mechanisms that extend beyond TCC formation.

Clinical profile and challenges faced in the management of optic neuritis: the Indian scenario.

PURPOSE: Optic neuritis (ON) is a relatively common ophthalmic disease that has recently received renewed attention owing to immunological breakthroughs. We studied the profile of patients with ON with special reference to antibody-mediated ON and the challenges faced in its management. METHODS: Case records of patients with ON presenting to a tertiary eye-care center in South India were analyzed. Data on demographics, presenting visual acuity (VA), clinical features, seropositivity for aquaporin-4 immunoglobulin G (AQP4-IgG) and myelin oligodendrocyte glycoprotein immunoglobulin G (MOG-IgG), details of magnetic resonance imaging (MRI) of orbits and brain, and treatment were collected. RESULTS: Among 138 cases with acute ON, male: female ratio was 1:2. Isolated ON was present in 41.3% of cases. Antibody testing of sera was performed in 68 patients only due to financial limitations. Among these, 48.5% were MOG-IgG-seropositive, 11.76% were AQP4-IgG-seropositive, and 30.88% samples were double seronegative. Other causes included multiple sclerosis (n = 4), lactational ON (n = 4), tuberculosis (n = 2), invasive perineuritis (n = 2), COVID-19 vaccination (n = 2), and COVID-19 (n = 1). The mean presenting best corrected visual acuity (BCVA) was 1.31 ± 1.16 logMAR (logarithm of the minimum angle of resolution). The mean BCVA at 3 months was 0.167 ± 0.46 logMAR. Only initial VA ≤ 'Counting fingers' (CF) had a significant association with the visual outcome for final VA worse than CF. The steep cost of investigations and treatment posed challenges for many patients in the management of ON. CONCLUSION: MOG-IgG-associated ON is common in India. Unfortunately, financial constraints delay the diagnosis and timely management of ON, adversely affecting the outcome.

Detection of Glymphatic Outflow of Tau from Brain to Cerebrospinal Fluid in Mice.

Glymphatic system denotes a brain-wide pathway that eliminates extracellular solutes from brain. It is driven by the flow of brain interstitial fluid (ISF) and cerebrospinal fluid (CSF) via perivascular spaces. Glymphatic convective flow is driven by cerebral arterial pulsation, which is facilitated by a water channel, aquaporin-4 (AQP4) expressed in astrocytic end-foot processes. Since its discovery, the glymphatic system receives a considerable scientific attention due to its pivotal role in clearing metabolic waste as well as neurotoxic substances such as amyloid b peptide. Tau is a microtubule binding protein, however it is also physiologically released into extracellular fluids. The presence of tau in the blood stream indicates that it is eventually cleared from the brain to the periphery, however, the detailed mechanisms that eliminate extracellular tau from the central nervous system remained to be elucidated. Recently, we and others have reported that extracellular tau is eliminated from the brain to CSF by an AQP4 dependent mechanism, suggesting the involvement of the glymphatic system. In this chapter, we describe the detailed protocol of how we can assess glymphatic outflow of tau protein from brain to CSF in mice.

Aquaporin-4 inhibition attenuates Pentylenetetrazole-induced behavioral seizures and cognitive impairments in kindled rats.

Epilepsy is a neurological condition distinguished by recurrent and unexpected seizures. Astrocytic channels and transporters are essential for maintaining normal neuronal functionality. The astrocytic water channel, aquaporin-4 (AQP4), which plays a pivotal role in regulating water homeostasis, is a potential target for epileptogenesis. In present study, we examined the effect of different doses (10, 50, 100 µM and 5 mM) of AQP4 inhibitor, 2-nicotinamide-1, 3, 4-thiadiazole (TGN-020), during kindling acquisition, on seizure parameters and seizure-induced cognitive impairments. Animals were kindled by injection of pentylenetetrazole (PTZ: 37.5 mg/kg, i.p.). TGN-020 was administered into the right lateral cerebral ventricle 30 min before PTZ every alternate day. Seizure parameters were assessed 20 min after PTZ administration. One day following the last PTZ injection, memory performance was investigated using spontaneous alternation in Y-maze and novel object recognition (NOR) tests. The inhibition of AQP4 during the kindling process significantly decreased the maximal seizure stage and seizure duration (two-way ANOVA, P = 0.0001) and increased the latency of seizure onset and the number of PTZ injections required to induce different seizure stages (one-way ANOVA, P = 0.0001). Compared to kindled rats, the results of the NOR tests showed that AQP4 inhibition during PTZ-kindling prevented recognition memory impairment. Based on these results, AQP4 could be involved in seizure development and seizure-induced cognitive impairment. More investigation is required to fully understand the complex interactions between seizure activity, water homeostasis, and cognitive dysfunction, which may help identify potential therapeutic targets for these conditions.

Ginkgolide B can alleviate spinal cord glymphatic system dysfunction and provide neuroprotection in painful diabetic neuropathy rats by inhibiting matrix metalloproteinase-9.

The glymphatic system plays a crucial role in maintaining optimal central nervous system (CNS) function by facilitating the removal of metabolic wastes. Aquaporin-4 (AQP4) protein, predominantly located on astrocyte end-feet, is a key pathway for metabolic waste excretion. ß-Dystroglycan (ß-DG) can anchor AQP4 protein to the end-feet membrane of astrocytes and can be cleaved by matrix metalloproteinase (MMP)-9 protein. Studies have demonstrated that hyperglycemia upregulates MMP-9 expression in the nervous system, leading to neuropathic pain. Ginkgolide B (GB) exerts an inhibitory effect on the MMP-9 protein. In this study, we investigated whether inhibition of MMP-9-mediated ß-DG cleavage by GB is involved in the regulation of AQP4 polarity within the glymphatic system in painful diabetic neuropathy (PDN) and exerts neuroprotective effects. The PDN model was established by injecting streptozotocin (STZ). Functional changes in the glymphatic system were observed using magnetic resonance imaging (MRI). The paw withdrawal threshold (PWT) was measured to assess mechanical allodynia. The protein expressions of MMP-9, ß-DG, and AQP4 were detected by Western blotting and immunofluorescence. Our findings revealed significant decreases in the efficiency of contrast agent clearance within the spinal glymphatic system of the rats, accompanied by decreased PWT, increased MMP-9 protein expression, decreased ß-DG protein expression, and loss of AQP4 polarity. Notably, GB treatment demonstrated the capacity to ameliorate spinal cord glymphatic function by modulating AQP4 polarity through MMP-9 inhibition, offering a promising therapeutic avenue for PDN.

Case report: Identification of Hepatitis B Virus in the cerebrospinal fluid of neuromyelitis optica spectrum disorders and successful treatment with ofatumumab and inebilizumab.

Neuromyelitis optica spectrum disorder (NMOSD) is a rare demyelinating disease of the central nervous system primarily affecting the optic nerves, spinal cord, and brainstem. Viral infection may trigger NMOSD. Here, we report the case of a 34-year-old female presenting with a range of symptoms including nausea, vomiting, dysphagia, choking, and fatigue with unsteady gait, diplopia, hearing loss, left-sided facial paralysis, breathing difficulties, and hoarseness of voice. Her HBV DNA concentration, as determined by quantitative PCR analysis, exceeded 5×107 IU/ml in serum and 4.48×102 IU/ml in CSF. Next-generation sequencing of CSF revealed 1,528 HBV sequences in DNA analysis and 6 sequences in RNA analysis. Serum aquaporin-4 antibody (AQP4-Ab) titer was 1:10, and the CSF titer was 1:3.2. Brain magnetic resonance imaging showed high signal intensities in the brain stem, medulla oblongata, and left middle cerebellar peduncle with mild restricted-diffusion. The patient received antiviral and hepatoprotective medications before the high-dose methylprednisolone pulse therapy. However, the patient did not respond well to the first-line treatment. Subsequently, the patient received ofatumumab and inebilizumab. Throughout the follow-up period, there was a gradual improvement in her neurological symptoms, with no reactivation of hepatitis B or deterioration of liver function observed. Thereby, to the best of our knowledge, we report the first case of successful treatment with ofatumumab and inebilizumab in a patient with NMOSD concurrent with HBV infection.

Neuromyelitis Optica Spectrum Disorders and Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease.

For over two centuries, clinicians have been aware of various conditions affecting white matter which had come to be grouped under the umbrella term multiple sclerosis. Within the last 20 years, specific scientific advances have occurred leading to more accurate diagnosis and differentiation of several of these conditions including, neuromyelitis optica spectrum disorders and myelin oligodendrocyte glycoprotein antibody disease. This new understanding has been coupled with advances in disease-modifying therapies which must be accurately applied for maximum safety and efficacy.

Are monoclonals the only panacea for treatment of aquaporin-4 positive NMOSD? Experience from a low-&middle-income (LMIC) region.

OBJECTIVE: A plethora of monoclonals have ushered up for NMOSD treatment. However, their limited availability and cost concerns poses a challenge for usage in developing nations. We compared relapse rates and disabilities among aquaporin-4 positive(AQP4+ve) patients on conventional immunosuppressants and rituximab in a tertiary referral center in southern India. METHODS: This was a chart review of AQP4+ve patients registered under national demyelination registry maintained at institute. AQP4+ve patients were included if they were on azathioprine, MMF, methotrexate for six months; cyclophosphamide for three months and rituximab for one month. RESULTS: 207 records were screened, 154 fulfilled inclusion criteria. Drugs used were azathioprine (70), MMF (34) and rituximab (33). All three drugs were non-inferior to each other in terms of ARR reduction. Median EDSS at last follow-up was significantly lower for azathioprine(2;IQR:0-5) and rituximab(2;IQR:0.5-5) than MMF(3.5;IQR:2-5.6), however azathioprine was associated with highest switch rate(34.3%) and was the only drug which required change because of intolerance. Failure rate was least for rituximab(27.3%).Patients on azathioprine and MMF required higher mean duration of concurrent steroids(7.8±7.7 and 4.56±2.17 months respectively) when compared to rituximab(2.77±1.38) and had more relapses due to steroid withdrawal. CONCLUSION: Initial treatment with azathioprine, MMF and rituximab is comparable in terms of ARR reduction. Findings suggest that choice may be guided by adverse event profile of drug, rather than efficacy per se. Concurrent treatment duration with steroids should also guide clinical decision. Switch to second immunomodulation in event of initial failure adds to efficacy benefit, irrespective of the drug chosen.

Cell-Based Assay to Detect the Autoantibody Serostatus in Patients with Neuromyelitis Optica Spectrum Disorder (NMOSD).

Cell-based assay (CBA) is an immunofluorescence assay that is extensively used for the confirmatory diagnosis of inflammatory demyelinating diseases of the central nervous system, like neuromyelitis optica spectrum disorder (NMOSD). Detecting the type of autoantibody present in the sera of the patients is the primary goal. CBA is the most sensitive and recommended detection method among all similar tools. Briefly, serum autoantibody is screened by transfecting specific cells seeded on cover glasses with full-length specific antigen fused with green fluorescent protein (GFP), followed by treating them with the patient serum used here as the source of primary antibody. The autoantibody-treated cells are further labeled with a rhodamine-conjugated secondary antibody. The co-localization of GFP and rhodamine is visualized by confocal microscopy, and the intensity of fluorescence is evaluated to determine the presence of autoantibody. A detailed protocol to screen antibodies against AQP4 and MOG in human sera using this method is described.

Mortality of the Danish Nationwide AQP4 Antibody-Seropositive Neuromyelitis Optica Spectrum Disorder Patient Cohort.

BACKGROUND AND OBJECTIVES: We aimed to evaluate the mortality of patients with AQP4 antibody-seropositive (AQP4-Ab+) neuromyelitis optica spectrum disorder (NMOSD) in Denmark compared with that in the general population. METHODS: We identified patients with AQP4-Ab+ NMOSD fulfilling the 2015 International Panel for Neuromyelitis Optica Diagnosis (IPND) criteria from multiple sources (laboratories and the Danish Multiple Sclerosis Registry). We obtained detailed information about patients from hospital records and about the general population matched on age, sex, and calendar year from Statistics Denmark. We calculated standardized mortality ratio (SMR), excess number of deaths per 1,000 person-years (EDR), and life expectancies compared with those of the matched general population. We examined predictive factors of mortality and the cause of death. RESULTS: Of 66 patients with AQP4-Ab+ NMOSD between 2008 and 2020, 15 died. Overall, the SMR was 2.54 (95% CI 1.47-4.09), and the EDR was 16.8 (95% CI 4.6-34.3). The median life expectancy for patients with AQP4-Ab+ NMOSD was 64.08 years (95% CI 53.02-83.9), compared with 83.07 years for the general population. Risk of death over time was increased in the patient population with a hazard ratio (HR) of 2.22 (1.34-3.68; p = 0.002). The cause of death was directly related to NMOSD in 93% of the cases. The age at disease onset was an independent predictor of death (HR 1.042; 95% CI 1.006-1.079; p = 0.02). DISCUSSION: AQP4-Ab+ NMOSD is associated with increased mortality and shorter life expectancy compared with that in the general population, underlining the need for highly effective treatment approaches.

AQP4-DARPin1: A Chimeric Antigen Based on Scaffold Protein DARPin for Efficient Detection of AQP4-IgG in NMOSD.

AQP4-IgG is an autoantibody associated with neuromyelitis optica spectroscopic disorder (NMOSD), a central nervous system inflammatory disease that requires early diagnosis and treatment. We designed two fusion proteins, AQP4-DARPin1 and AQP4-DARPin2, comprising the complete antigenic epitopes of aquaporin-4 (AQP4) and the constant region of the scaffold protein DARPin. These fusion proteins were expressed and purified from Escherichia coli and coated on microplates to develop an efficient method for detecting AQP4-IgG. Molecular dynamics simulation revealed that the fusion of AQP4 extracellular epitopes with DARPin did not alter the main structure of DARPin. The purified AQP4-DARPins bound recombinant antibody rAb-53 (AQP4-IgG) with affinities of 135 and 285 nM, respectively. Enzyme-linked immunosorbent assay (ELISA) and immunoprecipitation demonstrated that AQP4-DARPin1 specifically recognized AQP4-IgG in the NMOSD patient serum. AQP4-DARPin1 as a coated antigen showed higher ELISA signal and end point dilution ratio than full-length AQP4. Our AQP4-DARPin1-coated AQP4-IgG ELISA had 100% specificity and 90% sensitivity. These results indicate that AQP4-DARPin1, compared to existing detection strategies that use full-length or extracellular loop peptides of AQP4, provides a new and more effective approach to the ELISA detection of NMOSD.

Role of aquaporin-4 polarization in extracellular solute clearance.

Waste from the brain has been shown to be cleared via the perivascular spaces through the so-called glymphatic system. According to this model the cerebrospinal fluid (CSF) enters the brain in perivascular spaces of arteries, crosses the astrocyte endfoot layer, flows through the parenchyma collecting waste that is subsequently drained along veins. Glymphatic clearance is dependent on astrocytic aquaporin-4 (AQP4) water channels that are highly enriched in the endfeet. Even though the polarized expression of AQP4 in endfeet is thought to be of crucial importance for glymphatic CSF influx, its role in extracellular solute clearance has only been evaluated using non-quantitative fluorescence measurements. Here we have quantitatively evaluated clearance of intrastriatally infused small and large radioactively labeled solutes in mice lacking AQP4 (Aqp4-/-) or lacking the endfoot pool of AQP4 (Snta1-/-). We confirm that Aqp4-/- mice show reduced clearance of both small and large extracellular solutes. Moreover, we find that the Snta1-/- mice have reduced clearance only for the 500 kDa [3H]dextran, but not 0.18 kDa [3H]mannitol suggesting that polarization of AQP4 to the endfeet is primarily important for clearance of large, but not small molecules. Lastly, we observed that clearance of 500 kDa [3H]dextran increased with age in adult mice. Based on our quantitative measurements, we confirm that presence of AQP4 is important for clearance of extracellular solutes, while the perivascular AQP4 localization seems to have a greater impact on clearance of large versus small molecules.

MAIN POINTS: Solute clearance is reduced in mice lacking AQP4 Polarization of AQP4 to the endfeet may have a greater impact on clearance of large versus small molecules Clearance of large but not small solutes is correlated with age within adult age.

The Role of Gut Microbiota in Neuromyelitis Optica Spectrum Disorder.

Neuromyelitis optica spectrum disorder (NMOSD) is a rare, disabling inflammatory disease of the central nervous system (CNS). Aquaporin-4 (AQP4)-specific T cells play a key role in the pathogenesis of NMOSD. In addition to immune factors, T cells recognizing the AQP4 epitope showed cross-reactivity with homologous peptide sequences in C. perfringens proteins, suggesting that the gut microbiota plays an integral role in the pathogenicity of NMOSD. In this review, we summarize research on the involvement of the gut microbiota in the pathophysiology of NMOSD and its possible pathogenic mechanisms. Among them, Clostridium perfringens and Streptococcus have been confirmed to play a role by multiple studies. Based on this evidence, metabolites produced by gut microbes, such as short-chain fatty acids (SCFAs), tryptophan (Trp), and bile acid (BA) metabolites, have also been found to affect immune cell metabolism. Therefore, the role of the gut microbiota in the pathophysiology of NMOSD is very important. Alterations in the composition of the gut microbiota can lead to pathological changes and alter the formation of microbiota-derived components and metabolites. It can serve as a biomarker for disease onset and progression and as a potential disease-modifying therapy.

An AQP-4-IgG-Positive Patient with Neuroimaging Findings Suggestive of Multiple Sclerosis.

BACKGROUND Multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSDs) are 2 similar but distinct diseases. These diseases were difficult to distinguish from each other until aquaporin-4-IgG (AQP-4-IgG) was discovered. The accurate identification of these 2 diseases is crucial for appropriate drug treatment in clinical practice. Herein, we report a case of AQP-4-IgG seroconversion with magnetic resonance imaging (MRI) findings suggestive of MS. CASE REPORT A 54-year-old woman developed weakness in her right lower extremity that gradually returned to normal 4 years ago. Recently, she was admitted to the hospital for numbness and weakness of both lower limbs and the right upper limb for more than 10 days. The clinical and MRI features of the patient suggested a high susceptibility for misdiagnosis of MS. However, careful observation of the MRI revealed the presence of atypical MS lesions ("red flag" signs), indicating the possibility of other diagnoses in this patient. After further examination, serum AQP-4-IgG was detected, suggesting the potential presence of another disorder, NMOSD, in the patient. CONCLUSIONS Attention should be given to the identification of MS MRI "red flag" signs. Even for patients with a high suspicion of MS, it is necessary to conduct antibody tests for AQP-4-IgG, MOG-IgG and other relevant markers to screen for associated diseases because MS disease-modifying therapy approaches may lead to a deterioration in the state of NMOSD patients. Analyzing this case can help us to further distinguish the differences between these 2 types of diseases, which has important practical clinical value.

The Expression and Role of Aquaporin 4 in Colon Cancer.

BACKGROUND/AIM: Aquaporins (AQPs) were initially discovered as water channel proteins that facilitate transcellular water movements. Recent studies have shown that AQPs are expressed and play an oncogenic role in various cancers. However, the expression and role of Aquaporin 4 (AQP4) in colon cancer have not been investigated. This study aimed to examine the clinical and pathophysiologic significance of AQP4 in colon cancer. PATIENTS AND METHODS: Immunohistochemistry (IHC) of AQP4 for 145 primary tumor samples obtained from patients with stage II or III colon cancer was performed, and the relationship between AQP4 expression and patients' prognoses was analyzed. Knockdown experiments with AQP4 small interfering RNA using human colon cancer cells were conducted to analyze the effects on cell invasiveness. RESULTS: IHC revealed that AQP4 was scarcely expressed in the noncancerous colonic mucosa. Of the 145 patients who enrolled in this study, 109 (75.2%) and 36 (24.8%) patients were classified as negative and positive for AQP4 expression, respectively. A high level of AQP4 expression is significantly associated with deeper tumors with lymph node metastasis and venous invasion. A 5-year progression-free survival rate of AQP4-positive patients was significantly worse than that of AQP-4 negative patients (70.7% vs. 87.0%, p=0.049). Furthermore, AQP4 knockdown significantly inhibited cell migration and invasion in HCT116 cells. CONCLUSION: AQP4 may be a novel biomarker and therapeutic target for colon cancer.

T1 hypointense brain lesions in NMOSD and its relevance with disability: a single institution cross-sectional study.

BACKGROUND: T1 hypointense lesions are considered a surrogate marker of tissue destruction. Although there is a shortage of evidence about T1 hypointense brain lesions, black holes, in patients with Neuromyelitis Optica Spectrum Disorder (NMOSD), the clinical significance of these lesions is not well determined. OBJECTIVES: The impact of T1 hypointense brain lesions on the clinical status and the disability level of patients with NMOSD was sought in this study. METHODS: A total of 83 patients with the final diagnosis of NMOSD were recruited. Aquaporin-4 measures were collected. The expanded disability status scale (EDSS) and MRI studies were also extracted. T1 hypointense and T2/FLAIR hyperintense lesions were investigated. The correlation of MRI findings, AQP-4, and EDSS was assessed. RESULTS: T1 hypointense brain lesions were detected in 22 patients. Mean ± SD EDSS was 3.7 ± 1.5 and significantly higher in patients with brain T1 hypointense lesions than those without them (p-value = 0.01). Noticeably, patients with more than four T1 hypointense lesions had EDSS scores ≥ 4. The presence of T2/FLAIR hyperintense brain lesions correlated with EDSS (3.6 ± 1.6 vs 2.3 ± 1.7; p-value = 0.01). EDSS was similar between those with and without positive AQP-4 (2.7 ± 1.6 vs. 3.2 ± 1.7; p-value = 0.17). Also, positive AQP-4 was not more prevalent in patients with T1 hypointense brain lesions than those without them (50.9 vs 45.4%; p-value = 0.8). CONCLUSION: We demonstrated that the presence of the brain T1-hypointense lesions corresponds to a higher disability level in NMOSD.

CD11chigh B Cell Expansion Is Associated With Severity and Brain Atrophy in Neuromyelitis Optica.

BACKGROUND AND OBJECTIVES: Neuromyelitis optica (NMO) is an autoimmune astrocytopathy mediated by anti-AQP4 antibody-producing B cells. Recently, a B-cell subset highly expressing CD11c and T-bet, originally identified as age-associated B cells, has been shown to be involved in the pathogenesis of various autoimmune diseases. The objective of this study was to determine the relationship between the frequency of CD11chigh B cells per CD19+ B cells in the peripheral blood of patients with NMO and the clinical profiles including the brain volume. METHODS: In this observational study, 45 patients with anti-AQP4 antibody-positive NMO in remission and 30 healthy control subjects (HCs) were enrolled. Freshly isolated peripheral blood mononuclear cells were analyzed for immune cell phenotypes. The frequency of CD11chigh B cells per CD19+ B cells was assessed by flow cytometry and was evaluated in association with the clinical profiles of patients. Brain MRI data from 26 patients were included in the study for the analysis on the correlation between CD11chigh B-cell frequency and brain atrophy. RESULTS: We found that the frequency of CD11chigh B cells in CD19+ B cells was significantly increased in patients with NMO compared with HCs. The expansion of CD11chigh B cells significantly correlated with EDSS, past relapse numbers, and disease duration. In addition, a higher frequency of CD11chigh B cells negatively correlated with total brain, white matter, and gray matter volumes and positively correlated with T2/FLAIR high lesion volumes. When the past clinical relapse episodes of patients with or without the expansion of CD11chigh B cells were compared, relapses in the brain occurred more frequently in patients with CD11chigh B-cell expansion. CD11chigh B cells had distinct features including expression of chemokine receptors associated with migration into peripheral inflammatory tissues and antigen presentation. CD11chigh B-cell frequency was positively correlated with T peripheral helper-1 (Tph-1) cell frequency. DISCUSSION: Even during the relapse-free period, CD11chigh B cells could expand in the long disease context, possibly through the interaction with Tph-1 cells. The increased frequency of CD11chigh B cells associated with brain atrophy and disease severity, indicating that this cell population could be involved in chronic neuroinflammation in NMO.

[Glymphatic System and Idiopathic Normal Pressure Hydrocephalus].

The inflow channel of the glymphatic pathway is the basilar membrane formed by the pia matter and glial border membrane in the outermost layer of the artery. Cerebrospinal fluid from the subarachnoid space enters the brain parenchyma through this pathway, and its water component is pumped into the brain parenchyma through aquaporin 4. One of the driving forces is vascular pulsation, and if this pathway becomes inoperative, cerebrospinal fluid loses its normal dynamics and contributes to idiopathic normal pressure hydrocephalus. Future research is needed to determine the extent of this contribution to the development of idiopathic normal pressure hydrocephalus.

Chimeric AQP4-based immunosorbent for highly-specific removal of AQP4-IgG from blood.

Anti-aquaporin-4 autoantibodies (AQP4-IgG) are implicated in the pathogenesis of neuromyelitis optica spectrum disorders (NMOSD), and their removal from the blood circulation is considered to be an effective method for acute treatment. An ideal extracorporeal AQP4-IgG removal system should have high specificity, which means that it can selectively remove AQP4-IgG without affecting normal immunoglobulins. However, the conventional tryptophan immobilized column lacks sufficient specificity and cannot achieve this goal. In this study, we successfully prepared a fusion protein chimeric AQP4, which consists of the complete antigenic epitopes of human AQP4 and the constant region of scaffold protein DARPin. Chimeric AQP4 was expressed and purified from Escherichia coli, and then immobilized on agarose gel as a ligand for selective capture of AQP4-IgG immunosorbent. The prepared immunosorbent had a theoretical maximum adsorption capacity of 20.48 mg/g gel estimated by Langmuir isotherm. In vitro plasma perfusion tests demonstrated that the chimeric AQP4 coupled adsorbent had remarkable adsorption performance, and could eliminate more than 85 % of AQP4-IgG under the gel-to-plasma ratio of 1:50. Moreover, it exhibited high specificity because other human plasma proteins were not adsorbed in the dynamic adsorption experiment. These results suggest that the chimeric AQP4 coupled immunosorbent can provide a new approach for specific immunoadsorption (IA) treatment of NMOSD.