Autoimmune Glial Fibrillary Acidic Protein Astrocytopathy Is Associated with HLA-A*3303 and HLA-DPB1*0501.

We determined the genetic association between specific human leucocyte antigen (HLA) loci and autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy. Our results showed that autoimmune GFAP astrocytopathy was associated with HLA-A*3303 (odds ratio [OR] = 2.02, 95% confidence interval [CI] = 1.32-3.06, p = 0.00072, padj. = 0.046) and HLA-DBP1*0501 (OR = 0.51, 95% CI = 0.36-0.71, p = 0.000048, padj. = 0.0062). Moreover, HLA-A*3303 carriers with the disease had a longer hospital stay (p = 0.0005) than non-carriers. This study for the first time provides evidence for a role of genetic factor in the development of autoimmune GFAP astrocytopathy. ANN NEUROL 2024;95:901-906.

Cerebrospinal fluid uric acid levels associated with disease severity in patients with anti-N-methyl-d-aspartate receptor encephalitis.

INTRODUCTION: Uric acid (UA) is an important natural antioxidant and strong peroxynitrite scavenger, but little is known about central nervous system (CNS) levels of UA in patients with anti-N-methyl-d-aspartate receptor encephalitis (NMDARE). METHODS: Cerebrospinal fluid (CSF) and serum levels of UA were determined in 72 patients with anti-NMDARE and 111 controls with non-inflammatory neurological diseases (NINDs). Serum UA levels were also evaluated in 132 healthy controls (HCs). CSF neuron-specific enolase (NSE) and blood-brain barrier (BBB) index were evaluated in patients with anti-NMDARE. The association of CSF UA levels with anti-NMDARE and its clinical parameters were evaluated in the patients. RESULTS: CSF UA levels were lower in patients with anti-NMDARE than in patients with NINDs, especially in patients with severe impairments (modified Rankin Scale [mRS] scores >3 vs. ≤ 3, p = 0.006). Furthermore, serum UA levels in patients with anti-NMDARE were significantly lower than in patients with NINDs and HCs. CSF UA levels were significantly associated with mRS scores, and serum UA levels in patients with anti-NMDARE. Furthermore, CSF/serum UA ratio was significantly associated with BBB index. CONCLUSIONS: CSF UA levels associated with disease severity and serum UA levels in patients with anti-NMDARE. And CSF/serum UA ratio correlated with BBB index, indicating that CSF and serum UA levels change similarly with BBB permeability in anti-NMDARE patients.

CHI3L1 signaling impairs hippocampal neurogenesis and cognitive function in autoimmune-mediated neuroinflammation.

Chitinase-3-like protein 1 (CHI3L1) is primarily secreted by activated astrocytes in the brain and is known as a reliable biomarker for inflammatory central nervous system (CNS) conditions such as neurodegeneration and autoimmune disorders like neuromyelitis optica (NMO). NMO is an astrocyte disease caused by autoantibodies targeting the astroglial protein aquaporin 4 (AQP4) and leads to vision loss, motor deficits, and cognitive decline. In this study examining CHI3L1's biological function in neuroinflammation, we found that CHI3L1 expression correlates with cognitive impairment in our NMO patient cohort. Activated astrocytes secrete CHI3L1 in response to AQP4 autoantibodies, and this inhibits the proliferation and neuronal differentiation of neural stem cells. Mouse models showed decreased hippocampal neurogenesis and impaired learning behaviors, which could be rescued by depleting CHI3L1 in astrocytes. The molecular mechanism involves CHI3L1 engaging the CRTH2 receptor and dampening ß-catenin signaling for neurogenesis. Blocking this CHI3L1/CRTH2/ß-catenin cascade restores neurogenesis and improves cognitive deficits, suggesting the potential for therapeutic development in neuroinflammatory disorders.

Transfer of patient's peripheral blood mononuclear cells (PBMCs) disrupts blood-brain barrier and induces anti-NMDAR encephalitis: a study of novel humanized PBMC mouse model.

BACKGROUND: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a severe autoimmune neuropsychiatric disease. Brain access of anti-NMDAR autoantibody through the blood-brain barrier (BBB) is essential for pathogenesis. Most previous animal models limit the investigation of etiologies of BBB damage in patients. METHODS: In this study, we established a novel humanized mouse model of anti-NMDAR encephalitis by intraperitoneal injection of patients' peripheral blood mononuclear cells (PBMCs) into BALB/c Rag2-/-Il2rg-/-SirpαNODFlk2-/- mice. RESULTS: We found that engraftment of patients' PBMCs not only produced potent anti-GluN1 autoantibodies, but also disrupted BBB integrity to allow brain access of autoantibodies, resulting in a hyperactive locomotor phenotype, anxiety- and depressive-like behaviors, cognitive deficits, as well as functional changes in corresponding brain regions. Transcriptome analysis suggested an exaggerated immune response and impaired neurotransmission in the mouse model and highlighted Il-1ß as a hub gene implicated in pathological changes. We further demonstrated that Il-1ß was produced by endothelial cells and disrupted BBB by repressing tight junction proteins. Treatment with Anakinra, an Il-1 receptor antagonist, ameliorated BBB damage and neuropsychiatric behaviors. CONCLUSIONS: Our study provided a novel and clinically more relevant humanized mouse model of anti-NMDAR encephalitis and revealed an intrinsic pathogenic property of the patient's lymphocytes.

Early autoimmunity and outcome in virus encephalitis: a retrospective study based on tissue-based assay.

To explore the autoimmune response and outcome in the central nervous system (CNS) at the onset of viral infection and correlation between autoantibodies and viruses. METHODS: A retrospective observational study was conducted in 121 patients (2016-2021) with a CNS viral infection confirmed via cerebrospinal fluid (CSF) next-generation sequencing (cohort A). Their clinical information was analysed and CSF samples were screened for autoantibodies against monkey cerebellum by tissue-based assay. In situ hybridisation was used to detect Epstein-Barr virus (EBV) in brain tissue of 8 patients with glial fibrillar acidic protein (GFAP)-IgG and nasopharyngeal carcinoma tissue of 2 patients with GFAP-IgG as control (cohort B). RESULTS: Among cohort A (male:female=79:42; median age: 42 (14-78) years old), 61 (50.4%) participants had detectable autoantibodies in CSF. Compared with other viruses, EBV increased the odds of having GFAP-IgG (OR 18.22, 95% CI 6.54 to 50.77, p<0.001). In cohort B, EBV was found in the brain tissue from two of eight (25.0%) patients with GFAP-IgG. Autoantibody-positive patients had a higher CSF protein level (median: 1126.00 (281.00-5352.00) vs 700.00 (76.70-2899.00), p<0.001), lower CSF chloride level (mean: 119.80±6.24 vs 122.84±5.26, p=0.005), lower ratios of CSF-glucose/serum-glucose (median: 0.50[0.13-0.94] vs 0.60[0.26-1.23], p=0.003), more meningitis (26/61 (42.6%) vs 12/60 (20.0%), p=0.007) and higher follow-up modified Rankin Scale scores (1 (0-6) vs 0 (0-3), p=0.037) compared with antibody-negative patients. A Kaplan-Meier analysis revealed that autoantibody-positive patients experienced significantly worse outcomes (p=0.031). CONCLUSIONS: Autoimmune responses are found at the onset of viral encephalitis. EBV in the CNS increases the risk for autoimmunity to GFAP.

Serological biomarkers in autoimmune GFAP astrocytopathy.

Autoimmune glial fibrillary acidic protein astrocytopathy (GFAP-A) is a newly defined meningoencephalomyelitis. The pathogenesis of GFAP-A is not well understood. The present study measured the expression levels of 200 serological cytokines in GFAP-A patients, NMOSD patients and healthy controls (HCs). The correlations between serum cytokine levels and clinical information in GFAP-A patients were analyzed. A total of 147 serological proteins were differentially expressed in GFAP-A patients compared to HCs, and 33 of these proteins were not observed in NMOSD patients. Serum levels of EG-VEGF negatively correlated with GFAP antibody titers, MIP-3 alpha positively correlated with clinical severity in GFAP-A patients, and LIGHT positively correlated with WBC counts and protein levels in the CSF of GFAP-A patients. These results suggest that GFAP and AQP4 astrocytopathy share some common pathology related to TNF signaling. Serum MIP 3 alpha may be a biomarker to assess clinical severity and a potential target for therapy of autoimmune GFAP astrocytopathy.

CD8+ T-cell predominance in autoimmune glial fibrillary acidic protein astrocytopathy.

BACKGROUND AND OBJECTIVE: We aimed to report the pathological features of T lymphocytes in autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy (GFAP-A). METHODS: A retrospective pathological analysis of patients with GFAP-A was performed. RESULTS: Eight patients with GFAP-immunoglobulin G (IgG) and pathological data were included. Their biopsy findings were similar, and all showed marked lymphocytic infiltration in the white matter, with perivascular predominance. The lymphocytic infiltration was predominantly composed of CD8+ T lymphocytes rather than CD4+ T lymphocytes, except in one patient who had overlapping positive myelin oligodendrocyte glycoprotein-IgG. Unlike CD4+ T cells, CD8+ T cells were frequently observed adjacent to dystrophic neurons and astrocytes. There was also diffuse infiltration by CD68+ and CD163+ macrophages. CD8+ astrocytes were identified in two samples, but no CD4+ astrocytes were observed. CONCLUSIONS: A predominance of CD8+ T cells may be an important pathological and diagnostic feature in GFAP-A.

Autoimmune glial fibrillary acidic protein astrocytopathy mimics infectious meningitis: Two case reports.

BACKGROUND: Autoimmune glial fibrillary acidic protein astrocytopathy (A-GFAP-A) has been recently characterized as a novel autoimmune central nervous system (CNS) disorder with GFAP antibody as the biomarker. However, nonspecific symptoms of A-GFAP-A contribute to misdiagnosis. CASE PRESENTATION: The patients presented with initial symptoms of fever, headache, and nuchal rigidity. Case 1 exhibited mild signs of irritability, active tendon reflexes, and dysuria; case 2 had transient loss of consciousness. Cerebrospinal fluid (CSF) revealed lymphocytosis, elevated protein level, and decreased glucose level. Magnetic resonance imaging (MRI) revealed radial gadolinium enhancement perpendicular to the lateral ventricle. Viral meningitis or tubercular meningitis was suspected. However, their inflammatory and pathogenic indicators showed no abnormal changes, and empirical antibiotic and antiviral drugs did not result in remarkable recovery. Subsequently, cases were detected with a strongly positive expression of GFAP antibody in CSF and the symptoms improved dramatically after high-dose methylprednisolone pulse treatment. CONCLUSION: A-GFAP-A with meningitis-like symptoms could initially masquerade as intracranial infection, and prompt detection of GFAP antibody is essential for differentiation.

Clinical Heterogeneity in Patients with Glutamate Decarboxylase Antibody.

OBJECTIVE: To explore the diversity and clinical features of anti-glutamate decarboxylase (GAD) antibody-associated neurological diseases. METHODS: Clinical data of a series of 5 patients positive for anti-GAD antibodies were retrospectively analyzed. RESULTS: All 5 patients were female, with a median age of 41.5 years (range 19-60 years). Their neurological symptoms included stiff-person syndrome (SPS), encephalitis, myelitis, cramp, visual loss, and paresthesia. Three patients (60%) were diagnosed with tumors, 2 cases of thymic tumor and 1 of breast cancer. On immunohistochemistry for tumor pathology, expression of GAD65 was found only in 1 patient. Four patients (80%) had abnormal brain MRI findings. All patients received immunotherapy and improved significantly after treatment, but 4 (80%) then experienced a relapse. CONCLUSIONS: Neurological manifestations in anti-GAD-positive patients are diverse and include SPS, encephalitis, myelitis, cramp, visual loss, and paresthesia.

Silencing the NR2B gene in rat ACC neurons by lentivirus-delivered shRNA alleviates pain-related aversion.

The N-methyl-D-aspartate (NMDA) receptor NR2B subunit on neurons in the anterior cingulate cortex (ACC) is implicated in the affective response to noxious stimuli. Selectively silencing this NR2B subunit in ACC neurons could therefore alleviate pain-related aversion. However, to date, there is no optimal approach to selectively silence the NR2B gene in ACC neurons. In the present study, we constructed lentiviral vectors and delivered shRNA (NR2B-RNAi-LV) to effectively silence the NR2B gene in ACC neurons. The use of lentivirus resulted in 95% transfection efficiency and 83% silencing of the NR2B gene in ACC neurons. Electrophysiological experiments showed that the total INMDA was similarly reduced by 48% in lentivirus-transfected ACC neurons. The biochemical and functional data demonstrated that lentiviral shRNA delivery produced a high transfection and silencing efficiency in the ACC neurons. SNI rats weighting 220-250 g were randomly divided into three groups: normal saline group (NS), lenti-siRNA/NC (LV-NC) group, and lenti-siRNA/NR2B (LV-NR2B) group, and conditioned place avoidance was conducted. The results indicated that NR2B-RNAi-LV decreased greatly the conditioning scores of F-CPA while NC-GFP-LV has no effects. NR2B mRNA expression in the NR2B-RNAi-LV group was significantly lower than that in the control group and NC-GFP-LV group. This novel approach of silencing the NR2B gene in ACC neuron could potentially be used to alleviate pain-related aversion.