Clinical characteristics of autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy in children: A case series of 16 patients

PURPOSE

To investigate the clinical characteristics of autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy in children.

METHODS

We reviewed the medical records of Children's Hospital of Chongqing Medical University from January 2020 to September 2021 and retrospectively analysed the clinical features, magnetic resonance imaging (MRI) findings, laboratory findings, treatment and outcome of children with autoimmune GFAP astrocytopathy.

RESULTS

Sixteen patients were included: 6 and 10 tested positive for GFAP-IgG in cerebrospinal fluid (CSF) and both CSF and serum, respectively. The median patient age was 115 months (range: 36-180 months), and 7 patients (43.8%) were male. All patients had the clinical syndrome of encephalitis/meningoencephalitis with or without myelitis: encephalitis (8), meningoencephalitis (3), encephalomyelitis (1) and meningoencephalomyelitis (4). The most common clinical symptoms were fever (11), altered consciousness (11), headache (10) and seizure (9). Four patients developed central respiratory failure for which mechanical ventilation was needed. All patients showed hyperintense T2-weighted lesions on brain MRI in the cerebral white matter (13), brainstem (11), basal ganglia (11), thalamus (9), and cerebellum (3). Nine patients (56%) had abnormal hyperintense lesions in the bilateral basal ganglia and thalamus. Six of 12 patients who underwent gadolinium-enhanced brain MRI showed abnormal enhancement images, and five of them showed linear perivascular radial enhancement. The modified Rankin scale (mRS) score decreased significantly in most patients after immunotherapy. Two patients with coexisting neural autoantibodies relapsed; however, 15 patients who were followed up successfully had favorable outcomes at the last follow-up.

CONCLUSION

Children with autoimmune GFAP astrocytopathy usually have a clinical syndrome of encephalitis/meningoencephalitis with or without myelitis. Except for the linear perivascular radial gadolinium enhancement pattern, hyperintense lesions in the bilateral basal ganglia and thalamus might be another characteristic brain MRI finding of autoimmune GFAP astrocytopathy in children. Although a few patients with coexisting neural autoantibodies might relapse, children with autoimmune GFAP astrocytopathy usually have favorable outcomes after immunotherapy.

A novel classification model based on cerebral 18F-FDG uptake pattern facilitates the diagnosis of acute/subacute seropositive autoimmune encephalitis

PURPOSE

To explore the intrinsic alteration of cerebral 18F-FDG metabolism in acute/subacute seropositive autoimmune encephalitis (AE) and to propose a universal classification model based on 18F-FDG metabolic patterns to predict AE.

METHODS

Cerebral 18F-FDG PET images of 42 acute/subacute seropositive AE patients and 45 healthy controls (HCs) were compared using voxelwise and region of interest (ROI)-based schemes. The mean standardized uptake value ratios (SUVRs) of 59 subregions according to a modified Automated Anatomical Labeling (AAL) atlas were compared using a t-test. Subjects were randomly divided into a training set (70%) and a testing set (30%). Logistic regression models were built based on the SUVRs and the models were evaluated by determining their predictive value in the training and testing sets.

RESULTS

The 18F-FDG uptake pattern in the AE group was characterized by increased SUVRs in the brainstem, cerebellum, basal ganglia, and temporal lobe, and decreased SUVRs in the occipital, and frontal regions with voxelwise analysis (false discovery rate [FDR] p<0.05). Utilizing ROI-based analysis, we identified 15 subareas that exhibited statistically significant changes in SUVRs among AE patients compared to HC (FDR p<0.05). Further, a logistic regression model incorporating SUVRs from the calcarine cortex, putamen, supramarginal gyrus, cerebelum_10, and hippocampus successfully enhanced the positive predictive value from 0.76 to 0.86 when compared to visual assessments. This model also demonstrated potent predictive ability, with AUC values of 0.94 and 0.91 observed for the training and testing sets, respectively.

CONCLUSIONS

During the acute/subacute stages of seropositive AE, alterations in SUVRs appear to be concentrated within physiologically significant regions, ultimately defining the general cerebral metabolic pattern. By incorporating these key regions into a new classification model, we have improved the overall diagnostic efficiency of AE.

Characterization of a mutant samhd1 zebrafish model implicates dysregulation of cholesterol biosynthesis in Aicardi-Goutières syndrome

Aicardi-Goutières syndrome (AGS1-9) is a genetically determined encephalopathy that falls under the type I interferonopathy disease class, characterized by excessive type I interferon (IFN-I) activity, coupled with upregulation of IFN-stimulated genes (ISGs), which can be explained by the vital role these proteins play in self-non-self-discrimination. To date, few mouse models fully replicate the vast clinical phenotypes observed in AGS patients. Therefore, we investigated the use of zebrafish as an alternative species for generating a clinically relevant model of AGS. Using CRISPR-cas9 technology, we generated a stable mutant zebrafish line recapitulating AGS5, which arises from recessive mutations in SAMHD1. The resulting homozygous mutant zebrafish larvae possess a number of neurological phenotypes, exemplified by variable, but increased expression of several ISGs in the head region, a significant increase in brain cell death, microcephaly and locomotion deficits. A link between IFN-I signaling and cholesterol biosynthesis has been highlighted by others, but not previously implicated in the type I interferonopathies. Through assessment of neurovascular integrity and qPCR analysis we identified a significant dysregulation of cholesterol biosynthesis in the zebrafish model. Furthermore, dysregulation of cholesterol biosynthesis gene expression was also observed through RNA sequencing analysis of AGS patient whole blood. From this novel finding, we hypothesize that cholesterol dysregulation may play a role in AGS disease pathophysiology. Further experimentation will lend critical insight into the molecular pathophysiology of AGS and the potential links involving aberrant type I IFN signaling and cholesterol dysregulation.

Clinical and Radiological Characteristics of Children and Adults With First-Attack Myelin Oligodendrocyte Glycoprotein Antibody Disease and Analysis of Risk Factors for Predicting the Severity at Disease Onset in Central China

Objective

To analyze and compare different clinical, laboratory, and magnetic resonance imaging characteristics between pediatric and adult patients with first-attack myelin oligodendrocyte glycoprotein antibody disease (MOGAD) and to explore predictive factors for severity at disease onset.

Methods

Patients diagnosed with MOGAD at the First Affiliated Hospital of Zhengzhou University from January 2013 to August 2021 were enrolled in this retrospective study. Age at disease onset, sex, comorbidities, laboratory tests, magnetic resonance imaging (MRI) characteristics, and Expanded Disability Status Scale (EDSS) scores were collected and analyzed. The association between risk factors and initial EDSS scores at disease onset was analyzed using logistic regression models and Spearman correlation analyses. A receiver-operating characteristic (ROC) curve analysis was used to evaluate the predictive ability of the uric acid and homocysteine (Hcy) levels for the severity of neurological dysfunction at the onset of MOGAD.

Results

Sixty-seven patients (female, n=34; male, n=33) with first-attack MOGAD were included in this study. The mean age at onset was 26.43 ± 18.22 years (range: 3–79 years). Among patients &lt;18 years of age, the most common presenting symptoms were loss of vision (36.0%), and nausea and vomiting (24.0%), and the most common disease spectrum was acute disseminated encephalomyelitis (ADEM) (40.0%). Among patients aged ≥18 years, the most common presenting symptoms were loss of vision (35.7%), paresthesia (33.3%), and paralysis (26.2%), and the most common disease spectrum was optic neuritis (35.7%). The most common lesions were cortical gray matter/paracortical white matter lesions in both pediatric and adult patients. Uric acid [odds ratio (OR)=1.014; 95% confidence interval (CI)=1.006–1.022; P=0.000] and serum Hcy (OR=1.125; 95% CI=1.017–1.246; P=0.023) levels were significantly associated with the severity of neurological dysfunction at disease onset. Uric acid levels (r=0.2583; P=0.035) and Hcy levels (r=0.3971; P=0.0009) were positively correlated with initial EDSS scores. The areas under the ROC curve were 0.7775 (95% CI= 0.6617‒0.8933; P&lt;0.001) and 0.6767 (95% CI=0.5433‒0.8102, P=0.014) for uric acid and Hcy levels, respectively.

Conclusion

The clinical phenotype of MOGAD varies in patients of different ages. The most common disease spectrum was ADEM in patients aged&lt;18 years, while optic neuritis was commonly found in patients aged ≥18 years. The uric acid and Hcy levels are risk factors for the severity of neurological dysfunction at disease onset in patients with first-attack MOGAD.

Therapeutic Attributes of Endocannabinoid System against Neuro-Inflammatory Autoimmune Disorders

In humans, various sites like cannabinoid receptors (CBR) having a binding affinity with cannabinoids are distributed on the surface of different cell types, where endocannabinoids (ECs) and derivatives of fatty acid can bind. The binding of these substance(s) triggers the activation of specific receptors required for various physiological functions, including pain sensation, memory, and appetite. The ECs and CBR perform multiple functions via the cannabinoid receptor 1 (CB1); cannabinoid receptor 2 (CB2), having a key effect in restraining neurotransmitters and the arrangement of cytokines. The role of cannabinoids in the immune system is illustrated because of their immunosuppressive characteristics. These characteristics include inhibition of leucocyte proliferation, T cells apoptosis, and induction of macrophages along with reduced pro-inflammatory cytokines secretion. The review seeks to discuss the functional relationship between the endocannabinoid system (ECS) and anti-tumor characteristics of cannabinoids in various cancers. The therapeutic potential of cannabinoids for cancer-both in vivo and in vitro clinical trials-has also been highlighted and reported to be effective in mice models in arthritis for the inflammation reduction, neuropathic pain, positive effect in multiple sclerosis and type-1 diabetes mellitus, and found beneficial for treating in various cancers. In human models, such studies are limited; thereby, further research is indispensable in this field to get a conclusive outcome. Therefore, in autoimmune disorders, therapeutic cannabinoids can serve as promising immunosuppressive and anti-fibrotic agents.

Anti-inflammatory and immune-modulatory impacts of berberine on activation of autoreactive T cells in autoimmune inflammation

Autoreactive inflammatory CD4+ T cells, such as T helper (Th)1 and Th17 subtypes, have been found to associate with the pathogenesis of autoimmune disorders. On the other hand, CD4+ Foxp3+ T regulatory (Treg) cells are crucial for the immune tolerance and have a critical role in the suppression of the excessive immune and inflammatory response promoted by these Th cells. In contrast, dendritic cells (DCs) and macrophages are immune cells that through their inflammatory functions promote autoreactive T-cell responses in autoimmune conditions. In recent years, there has been increasing attention to exploring effective immunomodulatory or anti-inflammatory agents from the herbal collection of traditional medicine. Berberine, an isoquinoline alkaloid, is one of the main active ingredients extracted from medicinal herbs and has been shown to exert various biological and pharmacological effects that are suggested to be mainly attributed to its anti-inflammatory and immunomodulatory properties. Several lines of experimental study have recently investigated the therapeutic potential of berberine for treating autoimmune conditions in animal models of human autoimmune diseases. Here, we aimed to seek mechanisms underlying immunomodulatory and anti-inflammatory effects of berberine on autoreactive inflammatory responses in autoimmune conditions. Reported data reveal that berberine can directly suppress functions and differentiation of pro-inflammatory Th1 and Th17 cells, and indirectly decrease Th cell-mediated inflammation through modulating or suppressing other cells assisting autoreactive inflammation, such as Tregs, DCs and macrophages.

Aicardi-Goutières Syndrome associated mutations of RNase H2B impair its interaction with ZMYM3 and the CoREST histone-modifying complex

DNA-RNA hybrids arise in all cell types, and are removed by multiple enzymes, including the trimeric ribonuclease, RNase H2. Mutations in human RNase H2 result in Aicardi–Goutières syndrome (AGS), an inflammatory brain disorder notable for being a Mendelian mimic of congenital viral infection. Previous studies have shown that several AGS-associated mutations of the RNase H2B subunit do not affect trimer stability or catalytic activity and are clustered on the surface of the complex, leading us to speculate that these mutations might impair important interactions of RNase H2 with so far unidentified proteins. In this study, we show that AGS mutations in this cluster impair the interaction of RNase H2 with several members of the CoREST chromatin-silencing complex that include the histone deacetylase HDAC2 and the demethylase KDM1A, the transcriptional regulators RCOR1 and GTFII-I as well as ZMYM3, an MYM-type zinc finger protein. We also show that the interaction is mediated by the zinc finger protein ZMYM3, suggesting that ZMYM3 acts as a novel type of scaffold protein coordinating interactions between deacetylase, demethylase and RNase H type enzymes, raising the question of whether coordination between histone modifications and the degradation of RNA-DNA hybrids may be required to prevent inflammation in humans.

Impacts of microbiome metabolites on immune regulation and autoimmunity

A vast number of studies have demonstrated a remarkable role for the gut microbiota and their metabolites in the pathogenesis of inflammatory diseases, including multiple sclerosis (MS). Recent studies in experimental autoimmune encephalomyelitis, an animal model of MS, have revealed that modifying certain intestinal bacterial populations may influence immune cell priming in the periphery, resulting in dysregulation of immune responses and neuroinflammatory processes in the central nervous system (CNS). Conversely, some commensal bacteria and their antigenic products can protect against inflammation within the CNS. Specific components of the gut microbiome have been implicated in the production of pro-inflammatory cytokines and subsequent generation of Th17 cells. Similarly, commensal bacteria and their metabolites can also promote the generation of regulatory T-cells (Treg), contributing to immune suppression. Short-chain fatty acids may induce Treg either by G-protein-coupled receptors or inhibition of histone deacetylases. Tryptophan metabolites may suppress inflammatory responses by acting on the aryl hydrocarbon receptor in T-cells or astrocytes. Interestingly, secretion of these metabolites can be impaired by excess consumption of dietary components, such as long-chain fatty acids or salt, indicating that the diet represents an environmental factor affecting the complex crosstalk between the gut microbiota and the immune system. This review discusses new aspects of host-microbiota interaction and the immune system with a special focus on MS as a prototype T-cell-mediated autoimmune disease of the CNS.

Dysfunction of neuronal calcium signalling in neuroinflammation and neurodegeneration

Neurodegeneration has been increasingly recognised as the leading structural correlate of disability progression in autoimmune diseases such as multiple sclerosis. Since calcium signalling is known to regulate the development of degenerative processes in many cell types, it is believed to play significant roles in mediating neurodegeneration. Because of its function as a major juncture linking various insults and injuries associated with inflammatory attack on neuronal cell bodies and axons, it provides potential for the development of neuroprotective strategies. This is of great significance because of the lack of neuroprotective agents presently available to supplement the current array of immunomodulatory treatments. In this review, we summarise the role that various calcium channels and pumps have been shown to play in the development of neurodegeneration under inflammatory autoimmune conditions. The identification of suitable targets might also provide insights into applications in non-inflammatory neurodegenerative diseases.

Assessment of interferon-related biomarkers in Aicardi-Goutières syndrome associated with mutations in TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, and ADAR: a case-control study

BACKGROUND

Aicardi-Goutières syndrome (AGS) is an inflammatory disorder caused by mutations in any of six genes (TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, and ADAR). The disease is severe and effective treatments are urgently needed. We investigated the status of interferon-related biomarkers in patients with AGS with a view to future use in diagnosis and clinical trials.

METHODS

In this case-control study, samples were collected prospectively from patients with mutation-proven AGS. The expression of six interferon-stimulated genes (ISGs) was measured by quantitative PCR, and the median fold change, when compared with the median of healthy controls, was used to create an interferon score for each patient. Scores higher than the mean of controls plus two SD (>2·466) were designated as positive. Additionally, we collated historical data for interferon activity, measured with a viral cytopathic assay, in CSF and serum from mutation-positive patients with AGS. We also undertook neutralisation assays of interferon activity in serum, and looked for the presence of autoantibodies against a panel of interferon proteins.

FINDINGS

74 (90%) of 82 patients had a positive interferon score (median 12·90, IQR 6·14-20·41) compared with two (7%) of 29 controls (median 0·93, IQR 0·57-1·30). Of the eight patients with a negative interferon score, seven had mutations in RNASEH2B (seven [27%] of all 26 patients with mutations in this gene). Repeat sampling in 16 patients was consistent for the presence or absence of an interferon signature on 39 of 41 occasions. Interferon activity (tested in 147 patients) was negatively correlated with age (CSF, r=-0·604; serum, r=-0·289), and was higher in CSF than in serum in 104 of 136 paired samples. Neutralisation assays suggested that measurable antiviral activity was related to interferon α production. We did not record significantly increased concentrations of autoantibodies to interferon subtypes in patients with AGS, or an association between the presence of autoantibodies and interferon score or serum interferon activity.

INTERPRETATION

AGS is consistently associated with an interferon signature, which is apparently sustained over time and can thus be used to differentiate patients with AGS from controls. If future studies show that interferon status is a reactive biomarker, the measurement of an interferon score might prove useful in the assessment of treatment efficacy in clinical trials.

FUNDING

European Union's Seventh Framework Programme; European Research Council.

SAMHD1-dependent retroviral control and escape in mice

SAMHD1 is a host restriction factor for human immunodeficiency virus 1 (HIV-1) in cultured human cells. SAMHD1 mutations cause autoimmune Aicardi-Goutières syndrome and are found in cancers including chronic lymphocytic leukaemia. SAMHD1 is a triphosphohydrolase that depletes the cellular pool of deoxynucleoside triphosphates, thereby preventing reverse transcription of retroviral genomes. However, in vivo evidence for SAMHD1's antiviral activity has been lacking. We generated Samhd1 null mice that do not develop autoimmune disease despite displaying a type I interferon signature in spleen, macrophages and fibroblasts. Samhd1(-/-) cells have elevated deoxynucleoside triphosphate (dNTP) levels but, surprisingly, SAMHD1 deficiency did not lead to increased infection with VSV-G-pseudotyped HIV-1 vectors. The lack of restriction is likely attributable to the fact that dNTP concentrations in SAMHD1-sufficient mouse cells are higher than the KM of HIV-1 reverse transcriptase (RT). Consistent with this notion, an HIV-1 vector mutant bearing an RT with lower affinity for dNTPs was sensitive to SAMHD1-dependent restriction in cultured cells and in mice. This shows that SAMHD1 can restrict lentiviruses in vivo and that nucleotide starvation is an evolutionarily conserved antiviral mechanism.

TRPM2 cation channels modulate T cell effector functions and contribute to autoimmune CNS inflammation

TRPM2, a highly Ca²⁺-permeable member of the transient receptor potential melastatin-related (TRPM) family of cation channels, is expressed in cells of the immune system. We demonstrate firstly that TRPM2 cation channels on T cells critically influence T cell proliferation and proinflammatory cytokine secretion following polyclonal T cell receptor stimulation. Consistently, trpm2-deficient mice exhibited an attenuated clincal phenotype of experimental autoimmune encephalomyelitis (EAE) with reduced inflammatory and demyelinating spinal cord lesions. Importantly, trmp2-deficient T cells were as susceptible as wildtype T cells to oxidative stress-induced cell death as it occurs in inflammatory CNS lesions. This supports the notion that the attenuated EAE phenotype is mainly due to reduced T cell effector functions but unaffected by potential modulation of T cell survival at the site of inflammation. Our findings suggest TRPM2 cation channels as a potential target for treating autoimmune CNS inflammation.

The role of T cell apoptosis in nervous system autoimmunity

Fas is a transmembrane receptor involved in the death program of several cell lines, including T lymphocytes. Deleterious mutations hitting genes involved in the Fas pathway cause the autoimmune lymphoprolipherative syndrome (ALPS). Moreover, defective Fas function is involved in the development of common autoimmune diseases, including autoimmune syndromes hitting the nervous system, such as multiple sclerosis (MS) and chronic inflammatory demyelinating polyneuropathy (CIDP). In this review, we first explore some peculiar aspects of Fas mediated apoptosis in the central versus peripheral nervous system (CNS, PNS); thereafter, we analyze what is currently known on the role of T cell apoptosis in both MS and CIDP, which, in this regard, may be seen as two faces of the same coin. In fact, we show that, in both diseases, defective Fas mediated apoptosis plays a crucial role favoring disease development and its chronic evolution.

Central hypothyroidism in a patient with pituitary autoimmunity: evidence for TSH-independent thyroid hormone synthesis

CONTEXT

Acquired central hypothyroidism is rare, especially when isolated, and is typically associated with detectable, although biologically inactive, serum TSH.

OBJECTIVE

We describe a 56-yr-old woman with profound central hypothyroidism and partial central hypoadrenalism, in the absence of other endocrine abnormalities. In contrast to most cases of central hypothyroidism, serum TSH remained undetectable for 9 months before the initiation of thyroid hormone and hydrocortisone treatment. A test for pituitary autoantibody was moderately positive. Serum free T(4), serum T(3), and neck radioiodine uptake were low but detectable. The thyroid and pituitary glands appeared morphologically normal on neck ultrasound and head magnetic resonance imaging, respectively.

SETTINGS

The study was conducted in a tertiary academic medical center.

CONCLUSIONS

This case illustrates the variable clinical presentation of pituitary autoimmunity. The persistence of low but detectable thyroid hormone levels and radioiodine neck uptake in the absence of TSH suggests that significant TSH-independent thyroid hormone synthesis may occur in the normal thyroid.

SAMHD1-deficient CD14+ cells from individuals with Aicardi-Goutières syndrome are highly susceptible to HIV-1 infection

Myeloid blood cells are largely resistant to infection with human immunodeficiency virus type 1 (HIV-1). Recently, it was reported that Vpx from HIV-2/SIVsm facilitates infection of these cells by counteracting the host restriction factor SAMHD1. Here, we independently confirmed that Vpx interacts with SAMHD1 and targets it for ubiquitin-mediated degradation. We found that Vpx-mediated SAMHD1 degradation rendered primary monocytes highly susceptible to HIV-1 infection; Vpx with a T17A mutation, defective for SAMHD1 binding and degradation, did not show this activity. Several single nucleotide polymorphisms in the SAMHD1 gene have been associated with Aicardi-Goutières syndrome (AGS), a very rare and severe autoimmune disease. Primary peripheral blood mononuclear cells (PBMC) from AGS patients homozygous for a nonsense mutation in SAMHD1 (R164X) lacked endogenous SAMHD1 expression and support HIV-1 replication in the absence of exogenous activation. Our results indicate that within PBMC from AGS patients, CD14+ cells were the subpopulation susceptible to HIV-1 infection, whereas cells from healthy donors did not support infection. The monocytic lineage of the infected SAMHD1 -/- cells, in conjunction with mostly undetectable levels of cytokines, chemokines and type I interferon measured prior to infection, indicate that aberrant cellular activation is not the cause for the observed phenotype. Taken together, we propose that SAMHD1 protects primary CD14+ monocytes from HIV-1 infection confirming SAMHD1 as a potent lentiviral restriction factor.

Lentiviral accessory proteins play important roles in antagonizing host proteins aimed at suppressing HIV-1 replication at a cellular level. The SIV/HIV-2 protein Vpx counteracts SAMHD1, a previously unknown antiviral factor within myeloid blood cells, rendering these cells permissive to primate immunodeficiency viruses. We confirm in this study that Vpx interacts with SAMHD1 leading to ubiquitin-mediated degradation of SAMHD1, and renders CD14 positive monocytes susceptible to HIV-1 infection. We provide new insights into the ability of SAMHD1 to protect monocytic cells from HIV-1 infection by using primary cells from patients with Aicardi-Goutières syndrome (AGS) lacking endogenous SAMHD1 expression. We show that peripheral monocytic cells of AGS patients are highly permissive to HIV-1. Thus, our study demonstrates that SAMHD1 is critical for restriction of HIV-1 infection in monocytes adding SAMHD1 as a novel innate defense factor.

Anti-N-methyl-D-aspartate receptor encephalitis: early treatment is beneficial

Anti-N-methyl-D-aspartate receptor antibody has been associated with a severe stereotypic form of subacute encephalitis, often found in women with ovarian teratoma. Reported here is the diagnosis of anti-N-methyl-D-aspartate receptor encephalitis in a 5-year-old girl who presented with subacute encephalopathy and movement disorder without evidence of malignancy. Early diagnosis and treatment with immune globulin and steroids resulted in near-complete recovery.

Tolerogenic dendritic cells in the control of autoimmune neuroinflammation: an emerging role of protein-glycan interactions

During the past decade, a great deal of information has contributed to our understanding of the immunosuppressive pathways that operate during the resolution of autoimmune pathology, including central nervous system (CNS) inflammation. Activation of these pathways is accomplished through the integration of an intricate network of inhibitory signals and immune suppressive cells, including regulatory T cells, myeloid-derived suppressor cells, 'alternatively activated' macrophages and tolerogenic dendritic cells (DCs). During the course of inflammatory diseases, immature or mature DCs may be licensed by different stimuli (e.g. cytokines, neuropeptides and growth factors) to become tolerogenic and suppress pathogenic T cell responses, thus emphasizing the outstanding plasticity of these cells. Recent findings have shed light to an immunoregulatory circuit by which galectin-1, an endogenous glycan-binding protein, favors the differentiation of regulatory DCs which promote T cell tolerance and contribute to resolution of autoimmune pathology through mechanisms involving IL-27 and IL-10. Together with the ability of galectin-1-glycan interactions to selectively blunt T helper (Th)1 and Th17 responses, this effect provides a rational explanation for the broad immunosuppressive effects of this glycan-binding protein in several experimental models of chronic inflammation and cancer. In this mini review, we will summarize the regulatory signals leading to the differentiation of tolerogenic DCs and their participation in CNS inflammation. In addition, we will underscore recent findings on the emerging role of galectin-glycan interactions in the establishment of immunosuppressive networks during the resolution of chronic inflammation.

Antibodies to the GABA(B) receptor in limbic encephalitis with seizures: case series and characterisation of the antigen

BACKGROUND

Some encephalitides or seizure disorders once thought idiopathic now seem to be immune mediated. We aimed to describe the clinical features of one such disorder and to identify the autoantigen involved.

METHODS

15 patients who were suspected to have paraneoplastic or immune-mediated limbic encephalitis were clinically assessed. Confocal microscopy, immunoprecipitation, and mass spectrometry were used to characterise the autoantigen. An assay of HEK293 cells transfected with rodent GABA(B1) or GABA(B2) receptor subunits was used as a serological test. 91 patients with encephalitis suspected to be paraneoplastic or immune mediated and 13 individuals with syndromes associated with antibodies to glutamic acid decarboxylase 65 were used as controls.

FINDINGS

All patients presented with early or prominent seizures; other symptoms, MRI, and electroencephalography findings were consistent with predominant limbic dysfunction. All patients had antibodies (mainly IgG1) against a neuronal cell-surface antigen; in three patients antibodies were detected only in CSF. Immunoprecipitation and mass spectrometry showed that the antibodies recognise the B1 subunit of the GABA(B) receptor, an inhibitory receptor that has been associated with seizures and memory dysfunction when disrupted. Confocal microscopy showed colocalisation of the antibody with GABA(B) receptors. Seven of 15 patients had tumours, five of which were small-cell lung cancer, and seven patients had non-neuronal autoantibodies. Although nine of ten patients who received immunotherapy and cancer treatment (when a tumour was found) showed neurological improvement, none of the four patients who were not similarly treated improved (p=0.005). Low levels of GABA(B1) receptor antibodies were identified in two of 104 controls (p<0.0001).

INTERPRETATION

GABA(B) receptor autoimmune encephalitis is a potentially treatable disorder characterised by seizures and, in some patients, associated with small-cell lung cancer and with other autoantibodies.

FUNDING

National Institutes of Health.

Markers of mRNA stabilization and degradation, and RNAi within astrocytoma GW bodies

GW bodies (GWBs) are unique cytoplasmic structures that contain the mRNA binding protein GW182 and other proteins involved in mRNA processing pathways. The rationale for this study arose from clinical studies indicating that 33% of patients with GWB autoantibodies have a motor/sensory neuropathy and/or ataxia. The novelty of this study is the identification of GWBs in astrocytes and astrocytoma cells within cell bodies and cytoplasmic projections. Astrocytoma GWBs exhibit complex heterogeneity with combinations of LSm4 and XRN1 as well as Ago2 and Dicer, key proteins involved in mRNA degradation and RNA interference, respectively. GWB subsets contained the mRNA transport and stabilization proteins SYNCRIP, hnRNPA1, and FMRP, not previously described as part of the GWB complex. Immunoprecipitation of astrocytoma GWBs suggested that Dicer, hDcp, LSm4, XRN1, SYNCRIP, and FMRP form a multiprotein complex. GWBs are likely involved in a number of regulatory mRNA pathways in astrocytes and astrocytoma cells.

[Lipids and caplain in guinea pig tissues in the process of development of experimental autoimmune encephalomyelitis]

The character of some lipids level change--cholesterol and phospholipids--as basic lipid components of cell membranes in the guinea-pig brain and liver tissue, and in serum in conditions of development of experimental autoimmune encephalomyelitis (EAE) have been investigated on the 11th, 21st, 27th day after inoculation. It has been detected, that the level of the investigated lipids changes wavely and indifferent-direction in the brain tissue on the 21st day of EAE. Similar variability observed in the activity of proteolytic ferment calpain, which is authentically reduced in the brain tissue by the 11th hour and increases up to the test objective level in the subsequent periods of EAE development. In the liver the level of alpha-tocopherol is reduced, while the content of studied lipids does not change. The investigated parameters can be attributed to the factors, which play an essential role in structural stability of cell membranes and their variability in conditions of EAE development is related to the processes of nervous cells demyelinisation and, hence to occurrence of such pathology as multiple sclerosis in people.

Human autoantibodies against early endosome antigen-1 enhance excitatory synaptic transmission

Early endosome antigen 1 (EEA1), a peripheral membrane protein associated with the cytoplasmic face of early endosomes, controls vesicle fusion during endocytosis, as extensively studied in non-neuronal cells. In neurons, early endosomes are involved in recycling of synaptic vesicles and neurotransmitter receptors. Since certain patients bearing autoantibodies that target EEA1 develop neurological disease, we studied the subcellular distribution of EEA1 in neurons and the effect on neurotransmission of purified immunoglobulins from the serum of a patient bearing EEA1 autoantibodies. EEA1 was localized in the soma and in the postsynaptic nerve terminals. Electrophysiological recordings in hippocampal slices including purified EEA1 antibodies in the patch pipette solution, revealed a run-up of AMPA, N-methyl-D-aspartate and kainate receptor-mediated excitatory post-synaptic currents recorded from CA3 pyramidal neurons, which was absent in the recordings obtained in the presence of control human immunoglobulin G. Inclusion of human EEA1 antibodies had no effect on inhibitory post-synaptic responses. Recordings in the presence of a dominant-negative C-terminal EEA1 deletion mutant produced a similar effect as observed with human anti-EEA1 antibodies. This specific effect on the excitatory synaptic transmission may be due to the impairment of internalization of specific glutamate receptors and their subsequent accumulation in the synapse. These results may account for the neurological deficits observed in some patients developing EEA1 autoantibodies.

From cannabis to endocannabinoids in multiple sclerosis: a paradigm of central nervous system autoimmune diseases

An increasing body of evidence suggests that cannabinoids have beneficial effects on the symptoms of multiple sclerosis, including spasticity and pain. Endogenous molecules with cannabinoid-like activity, such as the "endocannabinoids", have been shown to mimic the anti-inflammatory properties of cannabinoids through the cannabinoid receptors. Several studies suggest that cannabinoids and endocannabinoids may have a key role in the pathogenesis and therapy of multiple sclerosis. Indeed, they can down regulate the production of pathogenic T helper 1-associated cytokines enhancing the production of T helper 2-associated protective cytokines. A shift towards T helper 2 has been associated with therapeutic benefit in multiple sclerosis. In addition, cannabinoids exert a neuromodulatory effect on neurotransmitters and hormones involved in the neurodegenerative phase of the disease. In vivo studies using mice with experimental allergic encephalomyelitis, an animal model of multiple sclerosis, suggest that the increase of the circulating levels of endocannabinoids might have a therapeutic effect, and that agonists of endocannabinoids with low psychoactive effects could open new strategies for the treatment of multiple sclerosis.

Activins, myostatin and related TGF-beta family members as novel therapeutic targets for endocrine, metabolic and immune disorders

Activins and inhibins were first identified by virtue of their ability to regulate follicle-stimulating hormone (FSH) secretion from the anterior pituitary. Activins are also powerful regulators of gonadal functions. However, the physiological functions of activins are not restricted to reproductive tissues. Activins are involved in apoptosis of hepatocytes and B cells, fibrosis, inflammation and neurogenesis. Activins are regarded as novel drug targets since blocking activins would provide benefits by preventing apoptosis, fibrosis, inflammation and growth of several cancers. Activins are members of the transforming growth factor-beta (TGF-beta) family, which has numerous peptide growth and differentiation factors including activins, bone morphogenetic proteins (BMPs), growth and differentiation factors (GDFs) and TGF-betas. Among them, GDF8 is also known as myostatin and is structurally related to activins. Myostatin is specifically expressed in the skeletal muscle lineage and is a candidate for muscle chalone negatively regulating the growth of myoblasts. Myostatin is regarded as a good drug target since therapeutics that modulate skeletal muscle growth would be useful for disease conditions such as muscular dystrophy, sarcopenia, cachexia and even diabetes. Recent studies have revealed that activins and myostatin signal through activin type II receptors (ActRIIA and ActRIIB) and their activities are regulated by extracellular binding proteins, follistatins and follistatin-related gene (FLRG). Furthermore, signaling of activins, myostatin and related ligands is also controlled by intracellular receptor-interacting proteins by novel mechanisms. In this review, I would like to show the current progress in the field emphasizing the importance of activins and myostatin as novel drug targets for immune, endocrine and metabolic disorders.

Lovastatin and mevastatin reduce basal and cytokine-stimulated production of prostaglandins from rat microglial cells in vitro: evidence for a mechanism unrelated to the inhibition of hydroxy-methyl-glutaryl CoA reductase

Statins were recently shown to possess anti-inflammatory activities, which might be responsible for their favourable effects in cardiovascular or CNS disorders independently from the inhibition of hydroxy-methyl-glutaryl CoA reductase. Here we investigated the effects of the statins lovastatin and mevastatin on prostanoid production in primary cultures of rat cortical microglia and astrocytes. We found that both statins significantly reduce prostaglandin E2 (PGE2) release from microglia, either under basal conditions or after stimulation by interleukin-1beta. Lovastatin also tends to reduce, although not in a significant manner, basal and interleukin-1beta-stimulated PGE2 release from astrocytes. Precursors and intermediates in cholesterol biosynthesis--mevalonic acid and geranyl and farnesyl pyrophosphate--also reduce PGE2 production, and potentiate the inhibitory effects of statins, suggesting that the latter might not depend on the inhibition of hydroxy-methyl-glutaryl CoA reductase.

The brain as an immune privileged site: dendritic cells of the central nervous system inhibit T cell activation

Dendritic cells (DC) are unique in their ability to prime naive T cells and initiate adaptive immunity. In recent years, DC were identified in the inflamed central nervous system (CNS), but their role in the initiation or regulation of the tissue specific immune response is unknown. As shown here, DC isolated from mice with experimental autoimmune encephalomyelitis (EAE) exhibit a maturational phenotype similar to immature bone marrow-derived DC or splenic DC as characterized by intermediate surface MHC class II and low expression of the costimulatory molecule CD80. However, they are unable to prime naive T cells. Moreover, they inhibit T cell proliferation stimulated by mature bone marrow-derived DC. TGFbeta, IL-10 and TRAIL were found to significantly contribute to the CNS-DC-mediated inhibition of allo-T cell proliferation. Thus CNS-DC may be the key responsibles for maintaining immune privilege within the inflamed CNS.

Autoimmunity in the peripheral nervous system

Autoimmune disorders of the peripheral nervous system (PNS) comprise a heterogeneous group of diseases that result from an aberrant immune response. Most of these disorders present severe morbidity and, in some cases, mortality. Even those conditions that are self-limited may display severe disability and necessitate hospitalization. Although their etiology remains elusive, there is increasing knowledge of the pathophysiological mechanisms causing tissue dysfunction and structural damage. The discovery of several mediators that constitute the molecular mechanisms of cell-cell and cell-extracellular-matrix interactions has revealed insight into various aspects of the neuroimmune interaction. Classic animal models associated with new genetic approaches have further increased our comprehension of the molecular pathways that regulate inflammatory disorders of the nervous system. The aim of this review is to describe various types and functions of the principal molecular components of the neuroimmune interaction and their importance in the principal autoimmune disorders of the PNS. We also provide an extensive description of clinical and pathological features of autoimmune disorders of the PNS, along with diagnostic and therapeutic implications.

Molecular mechanisms of axonal damage in inflammatory central nervous system diseases

PURPOSE OF REVIEW

Axonal dysfunction and damage is an early pathological sign of autoimmune central nervous system disease, viral and bacterial infections, and brain trauma. Axonal injury has attracted considerable interest during the past few years because the degree of axonal damage appears to determine long-term clinical outcome.

RECENT FINDINGS

Advanced magnetic resonance spectroscopic imaging techniques have suggested that axonal loss and dysfunction is responsible for the persistent neurological deficits that occur in patients with multiple sclerosis. Histopathological methods have shown that axonal damage is defined primarily by dysfunction of axonal transport, and finally by complete transection and degeneration of axons. Recent studies have demonstrated that the extent of axonal damage in the primary demyelinating lesion of multiple sclerosis patients is associated with the number of activated microglia/macrophages and cytotoxic CD8+ T lymphocytes. In addition, diffuse axonal dysfunction independent of demyelination develops in normal appearing white matter, possibly due to indirect effects of inflammation.

SUMMARY

The fact that axonal damage in response to overt inflammatory reactions may occur gradually, leaving a window for therapeutical intervention, has important clinical implications. Determination of the exact molecular mechanism might help in finding new therapies for inflammatory axonal damage.

Junctional complexes of the blood-brain barrier: permeability changes in neuroinflammation

A wide range of central nervous system (CNS) disorders include neuroinflammatory events that perturb blood-brain barrier (BBB) integrity. Mechanisms by which the BBB responds to physiological and pathological stimuli involve signaling systems in the tight and adherens junctions of the cerebral endothelium. In this review, we examine the molecular composition and regulatory mediators that control BBB permeability and assess how these mediators may be dysregulated in stroke, multiple sclerosis, brain tumors, and meningioencephalitis. An understanding of these molecular substrates in BBB regulation may lead to new approaches for enhancing CNS drug delivery and ameliorating brain edema after injury and inflammation.

Apoptosis of inflammatory cells in immune control of the nervous system: role of glia

The elimination of inflammatory cells within the central nervous system (CNS) by apoptosis plays an important role in protecting the CNS from immune-mediated damage. T cells, B cells, macrophages, and microglia all undergo apoptosis in the CNS. The apoptotic elimination of CNS-reactive T cells is particularly important, as these cells can recruit and activate other inflammatory cells. T-cell apoptosis contributes to the resolution of CNS inflammation and clinical recovery from attacks of experimental autoimmune encephalomyelitis (EAE), an animal model of the demyelinating disease multiple sclerosis (MS). T-cell apoptosis in the CNS in EAE occurs in both an antigen-specific and an antigen-nonspecific manner. In antigen-specific T-cell apoptosis, it is proposed that T cells that recognize their antigen in the CNS, such as CNS-reactive T cells, are deleted by the process of activation-induced apoptosis after activation of the T-cell receptor. This may result from the ligation of T-cell death receptors (such as CD95 (Fas) or tumor necrosis factor (TNF) receptor 1) by CD95 ligand (CD95L) or TNF expressed by the same T cell or possibly by microglia, astrocytes or neurons. Inadequate costimulation of the T cell by antigen-presenting glial cells may render T cells susceptible to activation-induced apoptosis. T cells expressing CD95 may also die in an antigen-nonspecific manner after interacting with glial cells expressing CD95L. Other mechanisms for antigen-nonspecific T-cell apoptosis include the endogenous release of glucocorticosteroids, deprivation of interleukin-2, and the release of nitric oxide by macrophages or glia. Apoptosis of autoreactive T cells in the CNS is likely to be important in preventing the development of autoimmune CNS diseases such as MS.

Failure of memory (CD44 high) CD4 T cells to recognize their target antigen in retina

Activated T cells recognize Ag in the retina, an immune privileged tissue, and may mediate autoimmune disease. In contrast, this report asks if resting, Ag-specific CD4(+) CD44(+) T cells can recognize Ag expressed in the retina. As a probe for Ag, 3E9 T cells specific for an immunodominant epitope of beta-galactosidase (beta-gal) were transferred to transgenic (Tg) mice expressing beta-gal in retinal photoreceptor cells, or to ROSA26 mice which express beta-gal widely. The survival, phenotype, and responsiveness of transferred 3E9 T cells were unaffected by the presence of retinal beta-gal, but altered by recognition of beta-gal in the ROSA26 mice. Inoculation or induction of activated T cells with specificity for this epitope produced autoimmune uveoretinitis, showing that the retinal beta-gal is expressed at immunologically significant levels. We conclude that sequestration provides a substantial barrier to recognition of Ag in quiet retina, and that insufficient Ag leaves the retina for detectable immune recognition outside of the retina.

Fas/Fas ligand-associated apoptosis in experimental autoimmune uveoretinitis in rodents: role of proinflammatory corticotropin-releasing hormone

We have previously shown that corticotropin-releasing hormone plays an important proinflammatory role in the induction of experimental autoimmune uveoretinitis. In this study, we examined the role of apoptosis in the destruction of the retina during experimental autoimmune uveoretinitis, and the role of corticotropin-releasing hormone as a local regulator of Fas and Fas Ligand expression in this condition. We evaluated apoptosis by the terminal deoxynucleotidyl transferase dUTP nick end labeling method and Fas and Fas Ligand presence by immunohistochemistry. We examined formalin-fixed, paraffin-embedded eye sections from female Lewis rats or B10.A mice immunized with the major pathogenetic epitope (R16 peptide) of the interphotoreceptor retinoid-binding protein. Female B10.A mice similarly immunized were treated with intraperitoneal injections of the rabbit anti-corticotropin-releasing hormone antibody TS-2 or nonimmune rabbit serum. The percentage of retinal cells undergoing apoptosis and the expression of Fas and Fas Ligand were increased in inflamed retinas in immunized Lewis rats and B10.A mice, compared to controls. Retinas from immunized B10.A mice treated with anti-corticotropin-releasing hormone antibody showed significantly lower apoptosis and Fas and Fas Ligand expression than placebo-treated animals. In conclusion, retinal cells in experimental autoimmune uveoretinitis undergo apoptosis associated with concurrent upregulation of Fas and Fas Ligand. The local presence of corticotropin-releasing hormone appears to be of pivotal importance in this process.