Aquaporin-4 Immunoglobulin G Research Articles

C3a Mediates Endothelial Barrier Disruption in Brain-Derived, but Not Retinal, Human Endothelial Cells.

Neuromyelitis optica spectrum disorder (NMOSD) is associated with pathological aquaporin-4 immunoglobulin G (AQP4-IgG), which cause brain damage. However, the impact of AQP4-IgG on retinal tissue remains unclear. Additionally, dysregulated complement anaphylatoxins C3a and C5a, known to modulate the endothelial barrier, are implicated in NMOSD. This study evaluates the susceptibility of human brain microvascular endothelial cells (HBMEC) and human retinal endothelial cells (HREC) to C3a- and C5a-mediated stress using real-time cell barrier analysis, immunocytochemical staining, qPCR and IgG transmigration assays. The findings reveal that C3a induced a concentration-dependent paracellular barrier breakdown and increased transcellular permeability in HBMEC, while HREC maintained barrier integrity under the same conditions. C5a attenuated C3a-induced disruption in HBMEC, indicating a protective role. Anaphylatoxin treatment elevated transcript levels of complement component C3 and increased C5 gene and protein expression in HREC, with no changes observed in HBMEC. In HBMEC, C5a treatment led to a transient upregulation of C3a receptor (C3AR) mRNA and an early decrease in C5a receptor 1 (C5AR1) protein detection. Conversely, HREC exhibited a late increase in C5aR1 protein levels. These results indicate that the retinal endothelial barrier is more stable under anaphylatoxin-induced stress compared to the brain, potentially offering better protection against paracellular AQP4-IgG transport.

Correlation between severe attacks and serum aquaporin-4 antibody titer in neuromyelitis optica spectrum disorder.

Aquaporin 4-immunoglobulin G (AQP4-IgG) specifically targets aquaporin 4 in approximately 80% of Neuromyelitis Optica Spectrum Disorder (NMOSD) cases. NMOSD is presently categorized as anti-AQP4-antibody (Ab) positive or negative based on AQP4-Ab presence. The association between antibody titers and patient prognosis remains unclear. Therefore, the present study explores the correlation between severe attacks and serum AQP4 Ab titers in patients with neuromyelitis optica spectrum disorder. Data were gathered retrospectively from 546 patients with NMOSD between September 1, 2009, and December 1, 2021. Patients were categorized based on their AQP4-Ab titers: AQP4 titer ≥ 1:320 were classified as the high-titer group, AQP4 (+ +), and AQP4 titer of ≤ 1:100 were classified as the low-titer group, AQP4 ( +). Clinical characteristics and prognoses between the two groups were compared. Patients with AQP4 ( +) exhibited few severe optic neuritis (SON) attacks (false discovery rate [FDR] corrected p < 0.001), a reduced percentage experiencing SON attacks, and a lower incidence of visual disability than patients with AQP4 (+ +). Patients with AQP4 (+ +) and AQP4 ( +) NMOSD exhibited significant difference in annual recurrence rate (ARR) (FDR-corrected p < 0.001). The lower AQP4 Ab titer group demonstrated reduced susceptibility to severe relapse with conventional immunosuppressive agents and rituximab (RTX) than the higher titer group. No significant differences in sex, age at onset, coexisting connective tissue diseases, motor disability, or mortality rates were observed between the two groups. Higher AQP4 Ab titers correlated with increased disease severity and visual disability in patients with NMOSD.

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

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. Caserecords 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. Among138cases 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 3months 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. MOG-IgG-associated ON is common in India. Unfortunately, financial constraints delay the diagnosis and timely management of ON, adversely affecting the outcome.

A case report on seronegative neuromyelitis optica spectrum disorder

An inflammatory, demyelinating, autoimmune disease that primarily affects the central nervous system mainly targeting optic nerve and spinal cord is called neuromyelitis optica (NMO). The term NMOSD refers to a recently revised nomenclature that includes new diagnostic criteria, such as serum aquaporin-4 immunoglobulin G (AQP4-IgG) antibody serological testing. One of the two common symptoms of NMOSD is optic neuritis or myelitis, which might appear as the initial symptom. And other symptoms include weakness, numbness, paralysis of limbs, nausea, vomiting, imbalance. It is thought to be related to an autoimmune reaction in which the immune system unintentionally targets healthy cells, particularly targeting proteins in the central nervous system like aquaporin-4. Seronegative NMOSD is treated with methylprednisolone, plasma exchange therapy, and IV immunoglobulin-G therapy.

Association of plasma sPD-1 and sPD-L1 with disease status and future relapse in AQP4-IgG (+) NMOSD.

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune-mediated disorder with aquaporin 4-immunoglobulin G (AQP4-IgG) in most settings. Soluble programmed death-1 (sPD-1) and soluble programmed death ligand 1 (sPD-L1) play key roles in immunomodulation. We aim to assess the association of sPD-1 and sPD-L1 with cytokines and their clinical significance in AQP4-IgG (+) NMOSD. We measured plasma sPD-1, sPD-L1, and 10 cytokines levels of 66 AQP4-IgG (+) NMOSD patients, including 40 patients in attack (attack-NMOSD) and 26 patients in remission (remission-NMOSD) phases, and 28 healthy controls through ultrasensitive Simoa and SP-X platform, respectively. We also performed >2 years (median) of follow-up after testing and analyzed the relationship between the detection index and current and future clinical parameters. Plasma sPD-1 level discriminated attack-NMOSD from remission-NMOSD (AUC = 0.692, p = 0.009). sPD-1 and sPD-L1 levels positively correlated with IL-6 (rsPD-1 = 0.313; rsPD-L1 = 0.508), IFN-γ (rsPD-1 = 0.331; rsPD-L1 = 0.456), and TNF-α (rsPD-1 = 0.451; rsPD-L1 = 0.531) expression, as well as clinical indicators, including the EDSS score (rsPD-1 = 0.331; rsPD-L1 = 0.402), number of attacks (rsPD-1 = 0.431) and segments of spinal cord involvement (rsPD-1 = 0.462; rsPD-L1 = 0.508). The risk of relapse within 2 years after sampling was associated with higher sPD-1/sPD-L1 ratio in attack-NMOSD (p = 0.022; Exp(B) = 1.589). Plasma sPD-1 and sPD-L1 levels reflected current disease severity and activity, and predicted future relapses in AQP4-IgG (+) NMOSD, suggesting that they hold the potential to guide timely and targeted treatment.

Frequency of new asymptomatic MRI lesions during attacks and follow-up of patients with NMOSD in a real-world setting.

We aimed to assess the frequency of new asymptomatic lesions on brain and spinal imaging (magnetic resonance imaging (MRI)) and their association with subsequent relapses in a large cohort of neuromyelitis optica spectrum disorder (NMOSD) patients in Argentina. We retrospectively reviewed 675 MRI (225 performed during an attack and 450 during the relapse-free period (performed at least 3 months from the last attack)) of NMOSD patients who had at least 2 years of clinical and MRI follow-up since disease onset. Kaplan-Meier (KM) curves were used for depicting time from remission MRI to subsequent relapse. We included 135 NMOSD patients (64.4% were aquaporin-4-immunoglobulin G (AQP4-IgG)-positive). We found that 26 (19.26%) and 66 (48.88%) of patients experienced at least one new asymptomatic MRI lesion during both the relapse-free period and attacks, respectively. The most frequent asymptomatic MRI lesions were optic nerves followed by short-segment myelitis during the relapse-free period and attacks. KM curves did not show differences in the time taken to develop a new relapse. Our findings showed that new asymptomatic lesions are relatively frequent. However, the presence of new asymptomatic MRI lesions during the relapse-free period and at relapses was not associated with a shorter time to developing subsequent relapses.

International Delphi Consensus on the Management of AQP4-IgG+ NMOSD: Recommendations for Eculizumab, Inebilizumab, and Satralizumab.

Neuromyelitis optica spectrum disorder (NMOSD) is a rare debilitating autoimmune disease of the CNS. Three monoclonal antibodies were recently approved as maintenance therapies for aquaporin-4 immunoglobulin G (AQP4-IgG)-seropositive NMOSD (eculizumab, inebilizumab, and satralizumab), prompting the need to consider best practice therapeutic decision-making for this indication. Our objective was to develop validated statements for the management of AQP4-IgG-seropositive NMOSD, through an evidence-based Delphi consensus process, with a focus on recommendations for eculizumab, inebilizumab, and satralizumab. We recruited an international panel of clinical experts in NMOSD and asked them to complete a questionnaire on NMOSD management. Panel members received a summary of evidence identified through a targeted literature review and provided free-text responses to the questionnaire based on both the data provided and their clinical experience. Responses were used to generate draft statements on NMOSD-related themes. Statements were voted on over a maximum of 3 rounds; participation in at least 1 of the first 2 rounds was mandatory. Panel members anonymously provided their level of agreement (6-point Likert scale) on each statement. Statements that failed to reach a predefined consensus threshold (≥67%) were revised based on feedback and then voted on in the next round. Final statements were those that met the consensus threshold (≥67%). The Delphi panel comprised 24 experts, who completed the Delphi process in November 2021 after 2 voting rounds. In round 1, 23/25 statements reached consensus and were accepted as final. The 2 statements that failed to reach consensus were revised. In round 2, both revised statements reached consensus. Twenty-five statements were agreed in total: 11 on initiation of or switching between eculizumab, inebilizumab, and satralizumab; 3 on monotherapy/combination therapy; 7 on safety and patient population considerations; 3 on biomarkers/patient-reported outcomes; and 1 on research gaps. An established consensus method was used to develop statements relevant to the management of AQP4-IgG-seropositive NMOSD. These international statements will be valuable for informing individualized therapeutic decision-making and could form the basis for standardized practice guidelines.

Targeting chemoattractant chemokine (C-C motif) ligand 2 derived from astrocytes is a promising therapeutic approach in the treatment of neuromyelitis optica spectrum disorders.

Aquaporin-4 immunoglobulin G (AQP4-IgG)-induced astrocytes injury is a key mechanism in the pathogenesis of neuromyelitis spectrum disorder (NMOSD), and although CCL2 is involved, its specific role has not been reported. We aimed to further investigate the role and potential mechanisms of CCL2 in AQP4-IgG-induced astrocyte injury. First, we evaluated CCL2 levels in paired samples of subject patients by automated microfluidic platform, Ella®. Second, we knock down astrocyte's CCL2 gene in vitro and in vivo to define the function of CCL2 in AQP4-IgG-induced astrocyte injury. Third, astrocyte injury and brain injury in live mice were assessed by immunofluorescence staining and 7.0T MRI, respectively. Western blotting and high-content screening were conducted to clarify the activation of inflammatory signaling pathways, and changes in CCL2 mRNA and cytokine/chemokines were measured by qPCR technique and flow cytometry, respectively. There were greatly higher CSF-CCL2 levels in NMOSD patients than that in other non-inflammatory neurological diseases (OND) groups. Blocking astrocyte CCL2 gene expression can efficiently mitigate AQP4-IgG-induced damage in vitro and in vivo. Interestingly, prevention of CCL2 expression could decrease other inflammatory cytokines released, including IL-6 and IL-1β. Our data suggest that CCL2 involves in the initiation and plays a pivotal role in AQP4-IgG-damaged astrocytes. Our results indicate that CCL2 may serve as a promising candidate target for inflammatory disorder therapy, including NMOSD.

Characterization of Disease Severity and Stability in NMOSD: A Global Clinical Record Review with Patient Interviews.

We sought insights into the classification of and factors associated with relapse severity and disease stability in neuromyelitis optica spectrum disorder (NMOSD) clinical practice worldwide. Neurologists recruited from six countries (the USA, Germany, Italy, Brazil, South Korea, and China) participated in a 30-60minute online survey and submitted two to four clinical records for aquaporin-4-immunoglobulin G (AQP4-IgG)-seropositive adults with NMOSD, which included patient demographics, diagnosis, maintenance treatment history, relapse occurrence, and severity. Separately, patients with NMOSD receiving maintenance therapy were interviewed over the telephone about their treatment journey, as well as perceptions of relapse severity and disease stability, and their potential influence on treatment decisions. Clinical records for 1185 patients with AQP4-IgG-seropositive NMOSD were provided by 389 neurologists (July-August 2020); 33 patients were interviewed (October-November 2020). There was no clear consensus on how relapse severity was defined in clinical practice, with geographical variations in relapse classification also found. Neurologists tended to rely on clinical assessments when determining severity, viewing each relapse in isolation, whereas patients had a more subjective view based on the changes in their daily lives and comparisons with prior relapses. Similarly, there was a disconnect in the definition of disease stability: the complete absence of relapses was more important for patients than for neurologists. A clear consensus on how to assess relapse severity and disease stability is needed to ensure that patients receive appropriate and timely treatment. In the future, clinical measures should be combined with patient-focused assessments.

Overlapping anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis with neuromyelitis optica spectrum disorders: a case report

BackgroundAnti-N-methyl-d-aspartate receptor (NMDAR) encephalitis can coexist with neuromyelitis optica spectrum disorder (NMOSD). Patients with overlapping anti-NMDAR encephalitis with positive NMDAR antibodies and aquaporin 4 immunoglobulin G (AQP4-IgG)-seropositive NMOSD are rare but should not be ignored.Case presentationThis report describes a unique case of anti-NMDAR encephalitis coexisting with NMOSD. A 27-year-old male presented with blurred vision, cognitive impairment, psychosis, dysphagia, gait instability and urinary incontinence. Brain magnetic resonance imaging (MRI) showed abnormal signals in the right cerebellar hemisphere, temporal lobe, and corpus callosum. NMDAR antibodies were positive in the CSF. AQP4-IgG antibodies were positive in the serum. The patient's condition was stable following intravenous gamma globulin, corticosteroids, immunosuppressants and symptomatic treatments.ConclusionsThis case provides further evidence for the occurrence of anti-NMDAR encephalitis overlapping NMOSD with AQP4-IgG-seropositive in a Chinese patient. However, the mechanisms underlying the occurrence of double-positive antibodies remain elusive.

Progress in treatment of neuromyelitis optica spectrum disorders (NMOSD): Novel insights into therapeutic possibilities in NMOSD.

Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune inflammatory demyelinating disorder of the central nervous system (CNS), which is a severely disabling disorder leading to devastating sequelae or even death. Repeated acute attacks and the presence of aquaporin‐4 immunoglobulin G (AQP4‐IgG) antibody are the typical characteristics of NMOSD. Recently, the phase III trials of the newly developed biologicals therapies have shown their effectiveness and good tolerance to a certain extent when compared with the traditional therapy with the first‐ and second‐line drugs. However, there is still a lack of large sample, double‐blind, randomized, clinical studies to confirm their efficacy, safety, and tolerability. Especially, these drugs have no clear effect on NMOSD patients without AQP4‐IgG and refractory patients. Therefore, it is of strong demand to further conduct large sample, double‐blind, randomized, clinical trials, and novel therapeutic possibilities in NMOSD are discussed briefly here.

Longitudinally Extensive Transverse Myelitis: One Disease, Variable Outcomes-A Case Series.

Longitudinal extensive transverse myelitis (LETM) is a rare form of widespread inflammation of the spinal cord causing T2 hyperintensity in spinal magnetic resonance imaging (MRI) extending across three or more vertebral segments. It is an acute onset of sensory, motor, and autonomic dysfunction of variable etiology with a likely poor outcome. We present a case series of three cases wherein children between the ages of 4 and 13 years had diverse symptoms from gradual painless loss of vision in both eyes with headache, vomiting and seizure, and a normal central nervous system examination except involvement of the optic nerve to another child with abdominal pain, urinary retention and constipation for 3 days with exaggerated DTR, and patchy sensory loss without any definite sensory level, and to the third child with fever and weakness of lower limbs, hypotonia and grade 1–2/5 power in lower limbs and normal upper limb power. Contrast-enhanced MRI spine of all children showed long segment T2 hyperintensity with variable involvement of the brain. The first two children were treated with pulsed dose methylprednisolone, and the last child received intravenous immunoglobulin followed by methylprednisolone. All were followed with oral prednisolone. LETM has a varied presentation with different etiologies. Antineuromyelitis optica immunoglobulin G (IgG) antibody (Aquaporin-4 IgG) and antimyelin oligodendrocyte glycoprotein antibody are strongly recommended though they may not be locally available or not affordable. Early and aggressive immunomodulatory therapy may help faster recovery, as did with two of our three children.

Disease Course and Outcomes in Patients With the Limited Form of Neuromyelitis Optica Spectrum Disorders and Negative AQP4-IgG Serology at Disease Onset: A Prospective Cohort Study

Background and PurposePatients presenting with clinical characteristics that are strongly suggestive of neuromyelitis optica spectrum disorders (NMOSD) have a high risk of developing definite NMOSD in the future. Little is known about the clinical course, treatment, and prognosis of these patients with likely NMOSD at disease onset.MethodsThis study prospectively recruited and visited 24 patients with the limited form of NMOSD (LF-NMOSD) at disease onset from November 2012 to June 2021. Their demographics, clinical course, longitudinal aquaporin-4 immunoglobulin G (AQP4-IgG) serology, MRI, therapeutic management, and outcome data were collected and analyzed.ResultsThe onset age of the cohort was 38.1±12.0 years (mean±standard deviation). The median disease duration was 73.5 months (interquartile range=44.3–117.0 months), and the follow-up period was 54.2±23.8 months. At the end of the last visit, the final diagnosis was categorized into AQP4-IgG-seronegative NMOSD (n=16, 66.7%), AQP4-IgG-seropositive NMOSD (n=7, 29.2%), or multiple sclerosis (n=1, 4.2%). Seven of the 24 patients (29.2%) experienced conversion to AQP4-IgG seropositivity, and the interval from onset to this serological conversion was 37.9±21.9 months. Isolated/mixed area postrema syndrome (APS) was the predominant onset phenotype (37.5%). The patients with isolated/mixed APS onset showed a predilection for conversion to AQP4-IgG seropositivity. All patients experienced a multiphasic disease course, with immunosuppressive therapy reducing the incidence rates of clinical relapse and residual functional disability.ConclusionsDefinite NMOSD may be preceded by LF-NMOSD, particularly isolated/mixed APS. Intensive long-term follow-up and attack-prevention immunotherapeutic management is recommended in patients with LF-NMOSD.

AQP4-IgG-seronegative patient outcomes in the N-MOmentum trial of inebilizumab in neuromyelitis optica spectrum disorder

BackgroundThe N-MOmentum trial, a double-blind, randomized, placebo-controlled, phase 2/3 study of inebilizumab in neuromyelitis optica spectrum disorder (NMOSD), enrolled participants who were aquaporin-4-immunoglobulin G (AQP4-IgG)-seropositive (AQP4+) or -seronegative (AQP4−). This article reports AQP4− participant outcomes. MethodsAQP4-IgG serostatus was determined for all screened participants by a central laboratory, using a validated, fluorescence-observation cell-binding assay. Medical histories and screening data for AQP4− participants were assessed independently by an eligibility committee of three clinical experts during screening. Diagnosis of NMOSD was confirmed by majority decision using the 2006 neuromyelitis optica criteria. Myelin oligodendrocyte glycoprotein-immunoglobulin G (MOG-IgG) serology (using a clinically validated, flow cytometry assay) and annualized attack rates (AARs) were evaluated post hoc. Efficacy outcomes were assessed by comparing pre-study and on-study AARs in treated participants. ResultsOnly 18/50 AQP4− screened participants (36%) were initially considered eligible for randomization; 16 were randomized and received full treatment, 4 to placebo (1 MOG-IgG-seropositive [MOG+]) and 12 to inebilizumab (6 MOG+). The most common reason for failure to pass screening among prospective AQP4− participants was failure to fulfill the 2006 NMO MRI criteria. In inebilizumab-treated AQP4− participants, on-study AARs (95% confidence interval [CI]) calculated from treatment initiation (whether from randomization or when received at the start of the open-label period) to the end of study were lower than pre-study rates: for all AQP4− participants (n = 16), mean (95% CI) AAR was 0.048 (0.02–0.15) versus 1.70 (0.74–2.66), respectively. For the subset of AQP4−/MOG+ participants (n = 7), AAR was 0.043 (0.006–0.302) after treatment versus 1.93 (1.10–3.14) before the study. For the subset of AQP4−/MOG− participants (n = 9), post-treatment AAR was 0.051 (0.013–0.204) versus 1.60 (1.02–2.38). Three attacks occurred during the randomized controlled period in the AQP4− inebilizumab group and were of mild severity; no attacks occurred in the AQP4− placebo group. The low number of participants receiving placebo (n = 4) confounds direct comparison with the inebilizumab group. No attacks were seen in any AQP4− participant after the second infusion of inebilizumab. Inebilizumab was generally well tolerated by AQP4− participants and the adverse event profile observed was similar to that of AQP4+ participants. ConclusionThe high rate of rejection of AQP4− participants from enrollment into the study highlights the challenges of implementing the diagnostic criteria of AQP4− NMOSD. An apparent reduction of AAR in participants with AQP4− NMOSD who received inebilizumab warrants further investigation.

An Experimental Model of Neuromyelitis Optica Spectrum Disorder-Optic Neuritis: Insights Into Disease Mechanisms.

Background: Optic neuritis (ON) is a common inflammatory optic neuropathy, which often occurs in neuromyelitis optica spectrum disease (NMOSD). An experimental model of NMOSD-ON may provide insight into disease mechanisms.Objective: To examine the pathogenicity of autoantibodies targeting the astrocyte water channel aquaporin-4 [aquaporin-4 (AQP4)-immunoglobulin G (AQP4-IgG)] in the optic nerve.Materials and Methods: Purified IgG from an AQP4-IgG-positive NMOSD-ON patient was together with human complement (C) given to wild-type (WT) and type I interferon (IFN) receptor-deficient mice (IFNAR1-KO) as two consecutive intrathecal injections into cerebrospinal fluid via cisterna magna. The optic nerves were isolated, embedded in paraffin, cut for histological examination, and scored semi-quantitatively in a blinded fashion. In addition, optic nerves were processed to determine selected gene expression by quantitative real-time PCR.Results: Intrathecal injection of AQP4-IgG+C induced astrocyte pathology in the optic nerve with loss of staining for AQP4 and glial fibrillary acidic protein (GFAP), deposition of C, and demyelination, as well as upregulation of gene expression for interferon regulatory factor-7 (IRF7) and CXCL10. Such pathology was not seen in IFNAR1-KO mice nor in control mice.Conclusion: We describe induction of ON in an animal model for NMOSD and show a requirement for type I IFN signaling in the disease process.

Sera from Patients with NMOSD Reduce the Differentiation Capacity of Precursor Cells in the Central Nervous System.

Introduction: AQP4 (aquaporin-4)–immunoglobulin G (IgG)-mediated neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory demyelinating disease that affects the central nervous system, particularly the spinal cord and optic nerve; remyelination capacity in neuromyelitis optica is yet to be determined, as is the role of AQP4–IgG in cell differentiation. Material and Methods: We included three groups—a group of patients with AQP4–IgG-positive neuromyelitis optica, a healthy group, and a sham group. We analyzed differentiation capacity in cultures of neurospheres from the subventricular zone of mice by adding serum at two different times: early and advanced stages of differentiation. We also analyzed differentiation into different cell lines. Results and Conclusions: The effect of sera from patients with NMOSD on precursor cells differs according to the degree of differentiation, and probably affects oligodendrocyte progenitor cells from NG2 cells to a lesser extent than cells from the subventricular zone; however, the resulting oligodendrocytes may be compromised in terms of maturation and possibly limited in their ability to generate myelin. Furthermore, these cells decrease in number with age. It is very unlikely that the use of drugs favoring the migration and differentiation of oligodendrocyte progenitor cells in multiple sclerosis would be effective in the context of neuromyelitis optica, but cell therapy with oligodendrocyte progenitor cells seems to be a potential alternative.

Optic chiasm involvement in AQP-4 antibody–positive NMO and MOG antibody–associated disorder

Background: Optic neuritis (ON) is often the presenting symptom in inflammatory central nervous system demyelinating disorders. Objective: To compare the frequency and pattern of optic chiasm involvement in patients with aquaporin-4-immunoglobulin G (AQP4-IgG)-associated ON to patients with myelin oligodendrocyte glycoprotein-immunoglobulin G (MOG-IgG)-associated ON. Methods: Retrospective review of all patients evaluated at Mayo Clinic, Stanford University and Ramathibodi Hospital who were found to have: (1) ON, (2) either MOG-IgG or AQP4-IgG by cell-based assay, and (3) magnetic resonance imaging (MRI) at the time of ON. MRI was reviewed for contrast enhancement of the optic chiasm and the pattern of involvement. Results: One hundred and fifty-four patients (74 AQP4-IgG and 80 MOG-IgG) were included. Among patients with AQP4-IgG-ON, 20% had chiasmal involvement, compared with 16% of patients with MOG-IgG-ON (p = 0.66). In patients with chiasmal involvement, longitudinally extensive optic nerve enhancement (from orbit extending to chiasm) was identified in 54% of MOG-IgG-ON patients, compared with 7% of AQP4-IgG-ON patients (p = 0.01). Conclusion: Chiasmal involvement of MOG-IgG-ON and AQP4-IgG-ON occur at more similar frequencies than previously reported. Furthermore, MOG-IgG-ON chiasmal involvement is more likely to be part of a longitudinally extensive optic nerve lesion.

Unbe‐leaf‐able! Aquaporin‐4's Connection to Neuromyelitis Optica

Neuromyelitis optica (NMO) is an incurable disease with debilitating symptoms that occurs when autoantibodies attack and destroy the water channel protein Aquaporin-4 (AQP4), located in the endfeet of astrocytes in the optic nerve, spinal cord, and brain. Our research on AQP4's role in NMO focused on the AQP-M23 isoform. The autoantibody Immunoglobulin G (IgG) can bind to epitopes on AQP4; this interaction is linked to neuroautoimmune disorders, specifically NMO. We hypothesized that structural similarities between certain plant AQPs and human AQP4 could be a trigger for neurological disorders. Individuals may develop an antigenic reaction to AQP by consuming plants high in AQP; the dietary antibodies produced could mistake human AQP4 for a particular plant AQP and attack it by crossing a compromised blood-brain barrier, leading to a neuroautoimmune response. It is essential to understand the relationship between AQP4's structure and IgG to better understand the cause for NMO and other neuroautoimmune disorders so that we can find more effective forms of treatment and propose potential cures. Additionally, it is important to know if there is a link between the consumption of plants high in AQP and the development of neuroautimmune disorders; if so, at-risk individuals with a damaged blood-brain barrier can avoid consuming AQP-rich foods. To identify possible binding sites between AQP4 and IgG, we examined the properties of extracellular loops A, C, and E in AQP4, focusing on amino acid residues 207-232 located on loop E. This segment of AQP4 has portions of its sequence that are identical to the corresponding portions on spinach, corn, soybean, and tomato AQP. We hypothesized that there might be a possible epitope for IgG binding within these residues on loop E. We used our research to then identify other possible locations for epitopes on AQP4 by analyzing the hydrophobicity and size of potential binding residues. To do this, we used the human AQP4 Protein Data Bank file, 3GD8, and Jmol molecular modeling software to highlight possible epitope locations and examine the structural changes that will occur when IgG binds to AQP4. We also highlighted variations between human AQP4 and plant AQP, specifically spinach AQP, which is the most commonly reactive. The Mahtomedi MSOE Center for BioMolecular Modeling MAPS Team used 3-D modeling and printing technology to examine the structure-function relationships of AQP4 in autoantibody binding. The visual model was a valuable tool in developing our story.

Clinical Features of Neuromyelitis Optica Spectrum Disorders with Connective Tissue Diseases

Objective To investigate the clinical features of neuromyelitis optica spectrum disorders(NMOSD)with connective tissue diseases(CTD). Methods Clinical data of 16 NMOSD-CTD patients and 54 NMOSD patients admitted to the Second Affiliated Hospital of Fujian Medical University from January 2015 to February 2020 were collected.The initial symptom,intracranial lesion,spinal cord lesion,laboratory examination and treatment response were compared between the two groups. Results The incidence of Sjögren's syndrome(SS)was the highest(10/16,62.5%)in NMOSD-CTD group.The NMOSD-CTD group had significantly higher positive rate of aquaporin-4 immunoglobulin G(AQP4-IgG)in serum or cerebrospinal fluid(100% vs. 70.2%,P=0.009),higher positive rates of serum anti-nuclear antibodies,anti Sjögren's syndrome A antibodies and anti-Ro52 autoantibodies(P<0.001),as well as higher proportion of patients with the expanded disability status scale score ≥ 6(50.0% vs. 22.2%,P=0.035)than the NMOSD group.There was no significant difference between the two groups in the age of onset,visiting age,recurrence frequency,disease course,distribution of intracranial lesions,spinal cord involvement,or the effective rate of glucocorticoid pulse therapy(all P>0.05).Conclusions NMOSD is often complicated with CTD,and SS is the most common one.The positive rate of serum or cerebrospinal AQP4-IgG and the seropositivity of several other autoantibodies in NMOSD-CTD patients were higher than those in NMOSD patients.Neurological impairment in NMOSD-CTD patients were severer,which should arouse attention of clinicians.

AQP4-IgG autoimmunity in Japan and Germany: Differences in clinical profiles and prognosis in seropositive neuromyelitis optica spectrum disorders.

BackgroundClinical outcomes in neuromyelitis optica spectrum disorders (NMOSD) vary across different regions.ObjectiveTo describe clinical profiles in Japanese and German NMOSD patients.MethodsMedical records of aquaporin-4-immunoglobulin G (AQP4-IgG) positive NMOSD patients from Japan (n = 54) and Germany (n = 38) were retrospectively analyzed.ResultsThe disability status was similar between both cohorts, although Japanese patients had a longer disease duration (13.3 ± 11.1 vs. 8.1 ± 6.9 years, p = 0.018) but similar relapse rates. Optic neuritis and myelitis were the most frequent attacks in both cohorts. Brain attacks occurred more frequently in Japanese patients (40.7% vs. 15.8%, p = 0.020). The time from disease onset (median [interquartile range] 2.3 [0.3-10.1] vs. 0.6 [0.2-1.9] years, p = 0.009) and the number of attacks (2.5 [1-7] vs. 2 [1-3], p = 0.047) until start of the first immunotherapy were higher in the Japanese cohort. Rituximab was the most common drug in the German cohort (52.6%) and not given in the Japanese cohort (p < 0.001), where oral prednisolone was the most common drug (92.6% vs. 15.8%, p < 0.001). The frequency of autoimmune comorbidities was higher in the German cohort (39.5% vs. 18.5%, p = 0.047).ConclusionCompared with Japanese NMOSD patients, German patients presented with similar disability despite shorter disease duration and earlier and more frequent immunosuppressive therapy.