Cytokines and biological markers in autoimmune GFAP astrocytopathy: The potential role for pathogenesis and therapeutic implications

Glial Fibrillary Acidic Protein Astrocytopathy: Review of Pathogenesis, Imaging Features, and Radiographic Mimics

Glial fibrillary acidic protein (GFAP) astrocytopathy is a recently described autoimmune inflammatory disorder of the CNS characterized by the presence of specific antibodies targeting the intracellular filament protein in mature astrocytes. The pathogenesis is heterogeneous and poorly understood, with around 20%-34% of cases occurring as a paraneoplastic syndrome, most frequently associated with ovarian teratomas. It presents clinically as acute or subacute encephalomyelitis, and the diagnosis relies on imaging and detection of GFAP-Immunoglobulin (GFAP-IgG) in the CSF. Characteristic imaging findings include linear perivascular enhancement in the white matter extending in a radial pattern. Other imaging findings include periependymal enhancement, longitudinally extensive cord signal changes, intramedullary enhancement, optic neuritis, and papillitis. There is significant imaging overlap with other neuroinflammatory diseases like neuromyelitis optica spectrum disorder and lymphoproliferative conditions. GFAP astrocytopathy is characteristically responsive to steroids with, however, a significant rate of relapse. Currently, literature on this novel entity is limited with no established diagnostic criteria or standard treatment regimen. This comprehensive review explores the clinical, radiographic, and histopathologic aspects of GFAP astrocytopathy, shedding light on its complex nature and potential diagnostic challenges. The paper highlights the neuroimaging findings with a focus on differentiating GFAP astrocytopathy from other neuroinflammatory disorders.

Clinical characteristics of overlapping syndrome in patients with GFAP-IgG and MOG-IgG: a case series of 8 patients and literature review

OBJECTIVE

The overlapping syndrome of anti-GFAP and anti-MOG antibodies is extremely rare. This retrospective study reports 8 adult cases of the GFAP-MOG overlapping syndrome.

METHODS

We reviewed the clinical characteristics of 8 adult patients with the GFAP-MOG overlapping syndrome from Jan 2019 and Sep 2023 at the Third Affiliated Hospital, Sun Yat-sen University. Moreover, we searched the literature and included all case reports with this overlapping syndrome since 2018 on PubMed.

RESULTS

The predominant clinical syndrome was meningoencephalomyelitis (5/8), followed by meningoencephalitis (2/8), and myelitis (1/8). Five patients had a flu-like prodromal symptom or diarrhea. No neoplasms were found in these patients. Regarding brain MRI, T2-weighted/fluid-attenuated inversion recovery hyperintensities were in 7 patients and leptomeningeal enhancement was in 4 patients. However, only one patient had periventricular radial linear enhancement. Besides, two patients had large space-occupying lesions. For spinal MRI, T2-hyperintensities were observed in 4 patients, in which 3 patients had longitudinally extensive lesions. All patients were treated with immunotherapy, the median follow-up period was 18 months (range, 3-36 months). Three patients presented relapses during the follow-up, but all cases recovered to mRS scores ≤ 2 at last follow-up. In addition, we also reviewed 14 cases (including 7 adults and 7 children) with this overlapping syndrome by literature review.

CONCLUSION

Our findings provide data to understand the clinical features and prognosis of the GFAP-MOG overlapping syndrome. Recognizing this overlapping syndrome will expand our knowledge, allowing for better management of these patients.

[Clinical features and pathogenesis of Glial fibrillary acidic protein (GFAP) antibody-associated disorders]

Glial fibrillary acidic protein (GFAP) antibody-associated disorders (AD) were recently proposed to be immune-mediated neurological disorders. The pathogenesis of GFAP antibody-AD is poorly understood. Pathologically, there is a marked infiltration of large numbers of lymphocytes, including CD8+ and CD4+ T cells, into the meningeal and brain parenchyma, especially around the perivascular areas. GFAP-specific cytotoxic T cells are considered to be the effector cells of GFAP antibody-AD. The common phenotype of GFAP antibody-AD includes meningoencephalitis with or without myelitis. During the clinical disease course, patients present with consciousness disturbances, urinary dysfunction, movement disorders, meningeal irritation, and cognitive dysfunction. The detection of GFAP antibodies in the cerebrospinal fluid (CSF) by cell-based assay is essential for a diagnosis of GFAP antibody-AD. The CSF can be examined for lymphocyte-predominant pleocytosis and elevated protein levels. Brain linear perivascular radial enhancement patterns are observed in about half of GFAP antibody-AD patients. Spinal cord magnetic resonance imaging is used to detect longitudinal extensive spinal cord lesions. Although corticosteroid therapy is generally effective, some patients have a poor prognosis and relapse.

Serum neurofilament and glial fibrillary acidic protein in idiopathic and seropositive transverse myelitis

BACKGROUND

Serum levels of neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) reflect the disease activity and disability in central nervous system (CNS) demyelinating diseases. However, the clinical significance of NfL and GFAP in idiopathic transverse myelitis (iTM), an inflammatory spinal cord disease with unknown underlying causes, remains unclear. This study aimed to investigate NfL and GFAP levels in iTM and their association with the clinical parameters compared with those in TM with disease-specific antibodies such as anti-aquaporin 4 or myelin oligodendrocyte glycoprotein antibodies (sTM).

METHODS

We collected serum and clinical data of 365 patients with CNS inflammatory diseases from 12 hospitals. The serum NfL and GFAP levels were measured in patients with iTM (n = 37) and sTM (n = 39) using ultrasensitive single-molecule array assays. Regression analysis was performed to investigate the associations between serum levels of NfL and GFAP and the clinical parameters such as higher EDSS scores (EDSS ≥ 4.0).

RESULTS

Mean NfL levels were not significantly different between iTM (50.29 pg/ml) and sTM (63.18 pg/ml) (p = 0.824). GFAP levels were significantly lower in iTM (112.34 pg/ml) than in sTM (3814.20 pg/ml) (p = 0.006). NfL levels correlated with expanded disability status scale (EDSS) scores in sTM (p = 0.001) but not in iTM (p = 0.824). Disease duration also correlated with higher EDSS scores in sTM (p = 0.017).

CONCLUSION

NfL levels and disease duration correlated with EDSS scores in sTM, and GFAP levels could be a promising biomarker to differentiate iTM from sTM.

Clinical characteristics of patient with GFAP-IgG: a review of 31 patients from two tertiary referral centers in China

OBJECTIVE

This study presents a comprehensive analysis of the clinical characteristics of 31 patients exhibiting cerebrospinal fluid (CSF) and/or serum positivity for GFAP-IgG, with a specific emphasis on 24 cases demonstrating only GFAP-IgG positivity. The investigation thoroughly evaluates their clinical, radiological, and laboratory features, as well as treatment responses, with the objective of offering clinicians potential diagnostic and therapeutic approaches.

METHODS

A total of 31 patients with GFAP-IgG in the CSF and/or serum were registered between August 2016 and August 2021 at the General Hospital of Ningxia Medical University and Huashan Hospital of Fudan University. We retrospectively reviewed their clinical records.

RESULTS

Overall, the patients were positive with GFAP-IgG in their CSF (15/31), in serum (6/31), and both CSF and serum (10/31). Among them, two were eventually diagnosed with astroglioma and primary central nervous system lymphoma, respectively; one patient had typical multiple sclerosis; three exhibited overlapping GFAP-IgG and aquaporin-4-IgG (AQP4-IgG); and one patient was coexisting N-methyl-D-aspartate receptor IgG. The remaining 24 patients were only GFAP-IgG positive. In total, 22 out of the 24 patients had abnormal MRI outcomes, involving the brain, meninges, and spinal cord. Besides, seven of the 24 patients developed optic neuritis. The CSF protein levels positively correlated with the Expanded Disability Status Scale score (EDSSs). Significantly decreased EDSSs, modified Rankin Scale score, GFAP-IgG titer, CSF protein level, and CSF white blood cell counts were observed after immunomodulatory therapy.

CONCLUSION

The clinical manifestations of GFAP-IgG exhibit a wide range of phenotypes that lack specificity. These findings emphasize the significance of not exclusively relying on the presence of antibodies to diagnose GFAP-A, but rather integrating them with the clinical phenotypes. GFAP-IgG testing enables the diagnosis of autoimmune GFAP astrocytopathy, a treatable autoimmune disease affecting the central nervous system. This condition provides opportunities for investigating innovative mechanisms of CNS autoimmunity and inflammation.

A pediatric case of autoimmune glial fibrillary acidic protein astrocytopathy with unique brain imaging patterns and increased cytokines/chemokines

BACKGROUND

Autoimmune anti-glial fibrillary acidic protein (GFAP) astrocytopathy represents a new spectrum of autoimmune inflammatory central nervous system disorders. In recent years, there have been an increasing number of reports on pediatric patients with this disease other than those in Japan.

CASE REPORT

A 6-year-old previously healthy boy presented with fever persisting for approximately 10 days, consciousness disturbance, anorexia, and hyponatremia (Na, 121 mEq/L). Even after appropriate correction of hyponatremia, consciousness disturbance was prolonged and was accompanied by gait disturbance, visual hallucinations, and autonomic dysfunction (bradycardia and urinary dysfunction). On a plain MRI, T2-weighted and fluid-attenuated inversion recovery images showed abnormal hyperintense lesions in the bilateral basal ganglia, thalamus, and periventricular white matter. The cerebrospinal fluid was positive for anti-GFAP antibody before treatment, and cytokines/chemokines were increased. He received three courses of intravenous methylprednisolone, followed by gradually tapered oral prednisolone for 6 months, without relapse after 1 year of observation.

CONCLUSION

In cases of autoimmune encephalitis with prolonged consciousness disturbance, hyponatremia, urinary dysfunction, and MRI findings with hyperintensities in the bilateral basal ganglia, thalamus, and periventricular white matter, anti-glial fibrillary acidic protein antibodies should be examined.

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.

Clinical and imaging analysis to evaluate the response of patients with anti-DPPX encephalitis to immunotherapy

BACKGROUND

To report the main spectrum and new clinical and imaging characteristics of dipeptidyl-peptidase-like protein 6 (DPPX) antibody-associated encephalitis, and to evaluate the effect of immunotherapy.

METHODS

A retrospective analysis of nine patients with anti-DPPX encephalitis was performed, and all previously reported cases in the literature were reviewed. A cell-based indirect immunofluorescence assay using human embryonic kidney 293 cells transfected with DPPX was used.

RESULTS

Nine patients were identified (median age, 51 years; range, 14-65 years) with prodromal fever, diarrhea, or weight loss, followed by rapid progressive encephalopathy characterized by cognitive disorder. One patient who received methylprednisolone therapy and a trial of tacrolimus showed substantial improvement and had no relapse by the 6-month follow-up. Our comprehensive literature review demonstrated that 53 cases were reported, of which more than half had prodromal weight loss (52.8%) and gastrointestinal disorders (58.5%). Cognitive disorders (74.6%) and brainstem/spinal cord disorders (75.5%) were the most common major symptoms. A greater proportion of Chinese patients than non-Chinese patients had abnormalities on brain magnetic resonance imaging specific for encephalitis (70.0% vs. 23.3%, P < 0.001). Our study is the first to report three patients with anti-DPPX encephalitis who had sleep disorders with rapid eye movement sleep behavior disorder, limb paralysis (two), severe pleocytosis, elevated protein levels (two) in the cerebrospinal fluid, and increased T2/FLAIR signal abnormalities in the bilateral hippocampus, temporal lobe, amygdala, basal ganglia, thalamus, centrum semiovale, and frontal and parietal lobes in seven patients (77.8%).

CONCLUSION

Our study expands the clinical and imaging phenotypes of anti-DPPX encephalitis. Further studies elucidating the entire clinical spectrum of anti-DPPX encephalitis, its pathogenic mechanisms, and prognosis under long-term immunosuppressive therapy are warranted.

Overlapping syndrome mimicking infectious meningoencephalitis in a patient with MOG and GFAP IgG

Background

Central nervous system overlapping autoimmune syndromes are uncommon, especially with the coexistence of MOG-IgG and GFAP-IgG.

Case presentation

A 23-year-old woman presented with transient convulsions, a loss of consciousness, persistent fever, headache, and vomiting. Cerebrospinal fluid (CSF) analysis revealed elevated cellularity, and magnetic resonance imaging (MRI) showed diffuse leptomeningeal enhancement. She had fever and headache with antiviral and antibiotic treatment for 2 weeks, and she had empirical anti-tuberculosis treatment and oral prednisolone therapy. She was followed for 3 months after presentation with improved symptoms and normal CSF analysis. A 3-month follow-up MRI showed asymmetric lesions in the cerebellum, corona radiata, and white matter with enhancement. The anti-tuberculosis treatment was continued, and steroid therapy was discontinued. After she stopped taking prednisolone, an interrupted headache gradually appeared. MRI at 4 months after presentation revealed a partial reduction in lesions but enlarged areas in the left cerebellum and right parietal white matter and a new lesion in the region of the right ependyma with linear enhancement. Her CSF was positive for anti-myelin oligodendrocyte glycoprotein (MOG) and anti-glial fibrillary acidic protein (GFAP) antibodies using a transfected cell-based assay. She was diagnosed with overlapping syndrome of MOG‑IgG‑associated disease and GFAP astrocytopathy. She received steroid pulse therapy (methylprednisolone, 1 g for 5 days), followed by a gradual tapering of oral prednisolone and the addition of an immunosuppressant (tacrolimus, 3 mg per day). Six months after the initial presentation, she had no symptoms. An MRI showed that the lesions had diminished, and no enhancement was found.

Conclusions

We report a case that was positive for double antibodies, which was initially misdiagnosed as infectious meningoencephalitis. This case broadens the clinical and phenotypic presentation of the overlapping syndrome spectrum.

Altered neuroaxonal integrity in schizophrenia and major depressive disorder assessed with neurofilament light chain in serum

BACKGROUND

Schizophrenia (SZ) and major depressive disorders (MDD) have been frequently linked to anatomical brain alterations. However, the relationship between brain pathology, inflammation and clinical symptoms in these disorders is still unclear. Thus, by applying novel blood markers of neuroaxonal integrity such as neurofilament light chain (NfL), we can now address main issues in psychiatric research and potentially offer innovative diagnostic tools toward better clinical characterizations and monitoring in both SZ and MDD.

METHODS

NfL levels were measured in serum of 44 patients with SZ and in 41 patients with MDD applying single molecule array technology and compared to a healthy norm population. Main inflammatory markers (C- reactive protein, interleukins IL-6 and IL-10) were measured to define patients with inflammatory phenotype. The Digit Symbol Substitution Task (DSST) and the Letter-Number-Sequencing Task were performed to estimate cognitive function in both groups.

RESULTS

NfL levels in MDD group (but not in SZ group) were significantly higher than reference values of healthy norm population. A higher than expected proportion of patients with NfL levels above age-specific cut-off values was observed in both SZ and MDD groups. No correlation was observed between NfL and inflammatory markers. A negative correlation between DSST and NfL-values was observed in patients with MDD.

CONCLUSIONS

Both SZ and MDD showed elevated serum levels of NfL, which were independent from inflammatory markers but associated with cognitive performance.

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.

Cytokine profile and glial activation following brachial plexus roots avulsion injury in mice

Inflammation and tissue infiltration by various immune cells play a significant role in the pathogenesis of neurons suffering the central nervous systems diseases. Although brachial plexus root avulsion (BPRA) leads to dramatic motoneurons (MNs) death and permanent loss of function, however, the knowledge gap on cytokines and glial reaction in the spinal cord injury is still existing. The current study is sought to investigate the alteration of specific cytokine expression patterns of the BPRA injured spinal cord during an acute and subacute period. The cytokine assay, transmission electron microscopy, and histological staining were utilized to assess cytokine network alteration, ultrastructure morphology, and glial activation and MNs loss within two weeks post-injury on a mouse unilateral BPRA model. The BPRA injury caused a progressively spinal MNs loss, reduced the alpha-(α) MNs synaptic inputs, whereas enhanced glial fibrillary acidic protein (GFAP), ionized calcium-binding adaptor molecule-1 (IBA-1), F4/80 expression in ipsilateral but not the contralateral spinal segments. Additionally, cytokine assays revealed BPRA significantly altered the level of CXCL1, ICAM1, IP10, MCP-5, MIP1-α, and CD93. Notably, the elevated MIP1-α was mainly expressed in the injured spinal MNs. While the re-distribution of CD93 expression, from the cytoplasm to the nucleus, occasionally occurred at neurons of the ipsilateral spinal segment after injury. Overall, these findings suggest that the inflammatory cytokines associated with glial cell activation might contribute to the pathophysiology of the MNs death caused by nerve roots injury.

Protein A Immunoadsorption Relieves Autoimmune Glial Fibrillary Acidic Protein Astrocytopathy after Unsuccessful Methylprednisolone Treatment

BACKGROUND

Autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy (GFAP-A) is a recently defined autoimmune inflammatory disease of the central nervous system in which GFAP IgG is present in the cerebrospinal fluid (CSF). Its primary clinical manifestation is meningoencephalitis, and it usually responds well to corticosteroids. Herein, we report a case of a patient with GFAP-A with initial symptoms of psychological and cognitive impairment, which did not respond to high-dose methylprednisolone therapy but was successfully treated with protein A immunoadsorption (PAIA) therapy.

METHODS

GFAP IgG was detected by indirect immunofluorescence assay. The patient's data were analyzed retrospectively.

RESULTS

A 48-year-old man presented with anxiety, depression, cognitive decline, tremor, gait disturbance, and fecal and urine incontinence. Autoimmune GFAP-A was diagnosed based on the following: (1) T2-weighted and fluid-attenuated inversion recovery MRI findings of hypersensitive lesions in the subcortical and deep white matter of the brain, with multiple longitudinally extensive lesions in the cervical and chest regions of the spinal cord, and (2) high levels of GFAP IgG in the CSF. Clinical symptoms and abnormalities detected on neuroimaging worsened after administration of high-dose intravenous methylprednisolone (IVMP) and intravenous immunoglobulin (IVIG) but improved significantly after PAIA therapy.

CONCLUSION

Psychological impairment can be the first sign of autoimmune GFAP-A. PAIA might be an effective treatment for patients with GFAP-A who respond poorly to conventional IVMP and IVIG therapy.

Black holes and high levels of neurofilaments in glial fibrillary acidic protein - astrocytopathy: a case report

BACKGROUND AND PURPOSE

Glial fibrillary acidic protein (GFAP) is an intracellular protein of the astrocytic cytoskeleton. Recently, autoantibodies to GFAP detected by cell-based assay in cerebrospinal fluid (CSF) or serum have been implicated in cerebral astrocytopathy, presenting predominantly with autoimmune meningoencephalomyelitis. However, the phenotypic spectrum, prognosis and therapeutics of this new entity remain to be elucidated.

METHODS

Herein, we report radiological, CSF and serological findings during disease exacerbation and remission, from a patient with autoimmune GFAP astrocytopathy, presenting as an immunotherapy responsive GFAP IgG-associated meningoencephalomyelitis.

RESULTS

Brain and spine magnetic resonance imaging revealed meningeal enhancement, T2 hyperintensities, black holes, significant sulci widening and spinal atrophy. In addition, high levels of neurofilaments (NfL) and GFAP were also identified during disease exacerbation, consistent with the appearance of the black holes.

CONCLUSIONS

To date, black holes and atrophy have never been reported before in autoimmune GFAP astrocytopathy. These findings, combined with the high levels of GFAP and NfL, suggest the existence of an underlying neurodegenerative mechanism in addition to the known inflammatory response. Further studies are needed to elucidate the pathomechanism of GFAP-astrocytopathies.

Abnormal evoked potentials in autoimmune glial fibrillary acidic protein astrocytopathy

Autoimmune GFAP astrocytopathy is a new clinical entity and only a limited number of cases have been reported. Here we report the results of multimodal central conduction studies performed in a case of this disorder.

A 72-year-old woman developed gradual cognitive decline and gait disturbance. A neurological examination revealed moderate amnesia, papilloedema, and pyramidal tract impairment of the bilateral lower limbs. The diagnosis of autoimmune GFAP astrocytopathy was made based on the typical MRI findings of periventricular radial linear gadolinium enhancement in the brain and longitudinally extensive lesions in the spinal cord, and anti-GFAP antibody detected in the cerebrospinal fluid. Somatosensory evoked potentials and transcranial magnetic stimulation studies revealed prolongation of conduction times. Visual evoked potentials showed an unusual W-shaped pattern. To our knowledge, this is the first neurophysiological demonstration of prolonged central conduction times in the autoimmune GFAP astrocytopathy. Further investigations are needed to establish the clinical value the neurophysiological examinations in this disorder.

•

A typical case of autoimmune GFAP astrocytopathy showed abnormal evoked potentials.

•

Prolonged central conduction times suggest central motor and sensory involvement.

•

Abnormal VEPs suggest the involvement of the visual pathway.