Autoantibodies against Glial Fibrillary Acidic Protein (GFAP) in Cerebrospinal Fluids from Pug Dogs with Necrotizing Meningoencephalitis

Astroglial Dysfunction, Demyelination and Nodular inflammation in Necrotizing Meningoencephalitis

Necrotizing Meningoencephalitis (NME), a form of Meningoencephalitis of Unknown Origin (MUO), is a progressive neuroinflammatory disease that primarily affects young, small-breed dogs. Due to limited understanding of its pathophysiology, early detection and the development of targeted therapies remain challenging. Definitive ante-mortem diagnosis is often unfeasible, and dogs with NME are frequently grouped under the broader MUO category. Our long-term objective is to identify distinct disease mechanisms within each MUO subtype to improve diagnostic accuracy, therapeutic approaches, and prognostic outcomes. To establish unique inflammatory patterns as they relate to neuropathologic changes in NME, we studied we studied the degree of immune cell infiltration, astrogliosis, demyelination, and microglial activation, comparing these factors with granulomatous meningoencephalomyelitis (GME), a closely related MUO subtype. We found that in the leptomeninges, NME is characterized by mild immune cell infiltration, in contrast to the prominent, B cell-rich aggregates seen in GME. In the neuroparenchyma, both diseases exhibit a comparable degree of lymphocyte infiltration; however, demyelination is more pronounced in NME, particularly within the subcortical white matter. Notably, areas of the brain affected by NME display a reduction in astrogliosis, which is associated with a marked decrease in the expression of the water channel protein aquaporin-4 (AQP4), a reduction not observed in GME. Additionally, we found that AQP4 expression levels correlate with the extent of microglial and macrophage activation. These findings suggest that astrocyte dysfunction in regions of microglial inflammation is a driver of NME and with adaptive immune responses likely playing a supportive role.

Canine idiopathic generalized tremor syndrome, immune-mediated?

Idiopathic generalized tremor syndrome is a disorder characterized by an acute onset of full-body tremors, sometimes accompanied by vestibulo-cerebellar signs, that is responsive to treatment with corticosteroids. Although considered to have an overall good outcome, relapsing and persistent mild clinical signs have been described. So far, little is known about the etiopathology of this syndrome, but it is believed to have an immune-mediated origin. In human medicine, description of numerous autoantibodies involved in certain non-infectious neurologic disorders has revolutionized understanding of their pathophysiology, diagnosis and treatment. In this multicenter retrospective study, we aimed to describe the clinical signs, course, and outcome of dogs with idiopathic generalized tremor syndrome and correlate potential findings with the presence or absence of autoantibodies associated with autoimmune cerebellar syndromes in humans. Information regarding signalment, history, clinical signs, laboratory findings, diagnostic imaging and testing for regional infectious diseases was gathered and the remaining serum and CSF samples were then analyzed for neural antibodies against targets associated with autoimmune encephalitic diseases of humans. Thirty-three dogs were included, and screening for neural antibodies was performed in 30 of those dogs. The analysis showed an increased titer of mGluR1 antibodies in two dogs, GFAP and later in the course of disease mGluR1 antibodies in one dog and an increase in unspecific autoantibodies which could not be further classified in two dogs. Dogs with detectable neural autoantibodies always had cerebrospinal fluid abnormalities in the form of a pleocytosis, with or without increased protein concentration, and tended to present with hyperthermia, potentially indicating a more severe clinical form of idiopathic generalized tremor syndrome in these cases. In conclusion, idiopathic generalized tremor syndrome is proposed to be an immune-mediated disorder potentially mediated by neural autoantibodies in a subgroup of dogs.

Lipid metabolites and nitric oxide production in the cerebrospinal fluid and plasma of dogs with meningoencephalitis of unknown origin and idiopathic epilepsy: a pilot study

Introduction

Idiopathic epilepsy (IE) and meningoencephalomyelitis of unknown origin (MUO) are common causes of brain diseases leading to seizures in dogs. In this study, the concentrations of 196 lipid metabolites and nitrogen oxide (NO) production in the cerebrospinal fluid (CSF) and plasma of dogs with MUO or IE were measured using a LC-MS/MS and a NOx analyzer, respectively.

Methods

Nine clinically healthy dogs and 11 and 12 dogs with IE and MUO, respectively, were included in the study.

Results

Lipid analysis revealed variations in the levels of four and six lipid metabolites in CSF and plasma, respectively, between the groups. The levels of 6-keto-prostaglandin (PG) F1α (PGF1α), 20-carboxy arachidonic acid (20-carboxy-AA), 9-hydroxyoctadecadienoic acid, and lyso-platelet-activating factor were high in the CSF of dogs with MUO. In addition, the plasma levels of 11,12-dihydroxyeicosatrienoic acid, 20-carboxy-AA, and oleoylethanolamide were high in dogs with IE, and those of PGF1α were high in dogs with MUO. NO production levels were high in CSF but not in plasma in dogs with MUO or IE.

Discussion

It remains unknown whether these changes represent the cause or effect of diseases of the central nervous system; however, lipid metabolites and NO production in CSF and plasma may be used as diagnostic biomarkers and could be exploited for treating idiopathic or inflammatory epilepsy in dogs.

Assessment of glial fibrillary acidic protein and anti-glial fibrillary acidic protein autoantibody concentrations and necrotising meningoencephalitis risk genotype in dogs with pug dog myelopathy

BACKGROUND

Pugs commonly present with thoracolumbar myelopathy, also known as pug dog myelopathy (PDM), which is clinically characterised by progressive signs involving the pelvic limbs, no apparent signs of pain and, often, incontinence. In addition to meningeal fibrosis and focal spinal cord destruction, histopathology has confirmed lymphohistiocytic infiltrates in the central nervous system (CNS) in a considerable number of pugs with PDM. Lymphohistiocytic CNS inflammation also characterises necrotising meningoencephalitis (NME) in pugs. This study aimed to investigate the potential contribution of an immunological aetiology to the development of PDM.

METHODS

The concentrations of glial fibrillary acidic protein (GFAP) in serum and CSF and of anti-GFAP autoantibodies in CSF were measured with an ELISA. In addition, a commercial test was used for genetic characterisation of the dog leukocyte antigen class II haplotype, which is associated with NME susceptibility.

RESULTS

This study included 87 dogs: 52 PDM pugs, 14 control pugs, four NME pugs and 17 dogs of breeds other than pugs that were investigated for neurological disease (neuro controls). Anti-GFAP autoantibodies were present in 15 of 19 (79%) of the PDM pugs tested versus six of 16 (38%) of the neuro controls tested (p = 0.018). All 18 PDM pugs evaluated had detectable CSF GFAP. Serum GFAP was detected in two of three (67%) of the NME pugs and in two of 11 (18%) of the control pugs but not in any of the 40 tested PDM pugs. Male pugs heterozygous for the NME risk haplotype had an earlier onset of clinical signs (70 months) compared to male pugs without the risk haplotype (78 months) (p = 0.036).

LIMITATIONS

The study was limited by the lack of healthy dogs of breeds other than pugs and the small numbers of control pugs and pugs with NME.

CONCLUSIONS

The high proportion of PDM pugs with anti-GFAP autoantibodies and high CSF GFAP concentrations provide support for a potential immunological contribution to the development of PDM.

Allele frequency of a genetic risk variant for necrotizing meningoencephalitis in pug dogs from Europe and association with the clinical phenotype

Introduction

Necrotizing meningoencephalitis (NME) in pugs is a potentially fatal disease, which needs lifelong treatment with immunosuppressive or immunomodulatory drugs and shares parallels with acute fulminating multiple sclerosis. Genetic variants of the DLA class II gene are associated with an increased risk for NME. Genetic testing is recommended prior to breeding. The aim of this study was to describe the current allele frequency of a previously identified NME risk variant in the European pug population. A secondary aim was to investigate the association of the NME risk variant with the clinical phenotype in pugs.

Methods

Results of genetic testing for the CFA12:2605517delC variant in European pugs between 2012 and 2020 were retrieved (n = 5,974). A validated questionnaire was mailed to all submitters of samples for further information on neurological signs, diagnostic tests, and disease course.

Results

The allele frequency of the CFA12 NME risk variant was 25.7% in the European pug population dogs; 7.4% of the dogs were homozygous and 36.7% were heterozygous for the NME risk variant on CFA12. Completed questionnaires were available in 203 dogs including 25 dogs with epileptic seizures or other neurological signs. The clinical phenotype was consistent with NME in 3.9% with a median age of onset of 1.0 years, and indicative of idiopathic epilepsy in 2.9% with a median onset of 2.5 years. Eleven dogs remained unclassified. Pugs with the NME phenotype were significantly more frequently homozygous for the NME risk variant on CFA12 compared to pugs ≥6 years without neurological signs or seizures (p = 0.008).

Discussion

The CFA12:2605517delC genetic risk variant is widely distributed in the European pug population and frequently homozygous in pugs with a NME phenotype. The data support the clinical relevance of the CFA12:2605517delC genetic risk variant.

New insights into neuropathology and pathogenesis of autoimmune glial fibrillary acidic protein meningoencephalomyelitis

Anti-glial fibrillary acidic protein (GFAP) meningoencephalomyelitis (autoimmune GFAP astrocytopathy) is a new autoimmune central nervous system (CNS) disease diagnosable by the presence of anti-GFAP autoantibodies in the cerebrospinal fluid and presents as meningoencephalomyelitis in the majority of patients. Only few neuropathological reports are available and little is known about the pathogenic mechanisms. We performed a histopathological study of two autopsies and nine CNS biopsies of patients with anti-GFAP autoantibodies and found predominantly a lymphocytic and in one autopsy case a granulomatous inflammatory phenotype. Inflammatory infiltrates were composed of B and T cells, including tissue-resident memory T cells. Although obvious astrocytic damage was absent in the GFAP-staining, we found cytotoxic T cell-mediated reactions reflected by the presence of CD8+/perforin+/granzyme A/B+ cells, polarized towards astrocytes. MHC-class-I was upregulated in reactive astrocytes of all biopsies and two autopsies but not in healthy controls. Importantly, we observed a prominent immunoreactivity of astrocytes with the complement factor C4d. Finally, we provided insight into an early phase of GFAP autoimmunity in an autopsy of a pug dog encephalitis that was characterized by marked meningoencephalitis with selective astrocytic damage with loss of GFAP and AQP4 in the lesions.Our histopathological findings indicate that a cytotoxic T cell-mediated immune reaction is present in GFAP autoimmunity. Complement C4d deposition on astrocytes could either represent the cause or consequence of astrocytic reactivity. Selective astrocytic damage is prominent in the early phase of GFAP autoimmunity in a canine autopsy case, but mild or absent in subacute and chronic stages in human disease, probably due to the high regeneration potential of astrocytes. The lymphocytic and granulomatous phenotypes might reflect different stages of lesion development or patient-specific modifications of the immune response. Future studies will be necessary to investigate possible implications of pathological subtypes for clinical disease course and therapeutic strategies.

Idiopathic generalised tremor syndrome in dogs

BACKGROUND

Idiopathic generalised tremor syndrome (IGTS) causes tremor and often vestibulocerebellar signs. Previous publications on IGTS in dogs are restricted to case reports or lack exclusion of structural causes.

METHODS

Medical records of 75 dogs diagnosed with IGTS that had undergone magnetic resonance imaging (MRI) of the brain were collected retrospectively.

RESULTS

Crossbreeds were affected most commonly (41.3%), followed by West Highland white terriers (14.7%) and cocker spaniels (10.7%). A higher proportion of females were affected than males (68.0%). Median age of the affected dogs was 17 months (range 6-121 months), and median bodyweight was 9.15 kg (range 2.9-26 kg). All dogs presented with tremors and most experienced concomitant neurological signs (93.3%). Seventeen (22.7%) were hyperthermic and 31 (41.3%) had gastrointestinal signs. MRI of the brain was normal in most of the cases, and cerebrospinal fluid analysis frequently revealed mild pleocytosis. All animals were treated with prednisolone, and 39 (51.3%) also received diazepam. Median follow-up time was 13 months (range 0-134 months). The overall outcome was good, although 16 (21.3%) patients were reported to have relapsing clinical signs and 10 (13.2%) patients experienced persistent mild clinical signs.

CONCLUSIONS

IGTS should be suspected in any dog with generalised tremor and vestibulocerebellar signs with younger and smaller dogs more commonly affected.

A scoping review of autoantibodies as biomarkers for canine autoimmune disease

BACKGROUND

Autoantibody biomarkers are valuable tools used to diagnose and manage autoimmune diseases in dogs. However, prior publications have raised concerns over a lack of standardization and sufficient validation for the use of biomarkers in veterinary medicine.

OBJECTIVES

Systematically compile primary research on autoantibody biomarkers for autoimmune disease in dogs, summarize their methodological features, and evaluate their quality; synthesize data supporting their use into a resource for veterinarians and researchers.

ANIMALS

Not used.

METHODS

Five indices were searched to identify studies for evaluation: PubMed, CAB Abstracts, Web of Science, Agricola, and SCOPUS. Two independent reviewers (AET and ELC) screened titles and abstracts for exclusion criteria followed by full-text review of remaining articles. Relevant studies were classified based on study objectives (biomarker, epitope, technique). Data on study characteristics and outcomes were synthesized in independent data tables for each classification.

RESULTS

Ninety-two studies qualified for final analysis (n = 49 biomarker, n = 9 epitope, and n = 34 technique studies). A high degree of heterogeneity in study characteristics and outcomes reporting was observed. Opportunities to strengthen future studies could include: (1) routine use of negative controls, (2) power analyses to inform sample sizes, (3) statistical analyses when appropriate, and (4) multiple detection techniques to confirm results.

CONCLUSIONS

These findings provide a resource that will allow veterinary clinicians to efficiently evaluate the evidence supporting the use of autoantibody biomarkers, along with the varied methodological approaches used in their development.

GFAP at 50

Fifty years have passed since the discovery of glial fibrillary acidic protein (GFAP) by Lawrence Eng and colleagues. Now recognized as a member of the intermediate filament family of proteins, it has become a subject for study in fields as diverse as structural biology, cell biology, gene expression, basic neuroscience, clinical genetics and gene therapy. This review covers each of these areas, presenting an overview of current understanding and controversies regarding GFAP with the goal of stimulating continued study of this fascinating protein.

Biomarkers of non-infectious inflammatory CNS diseases in dogs - Where are we now? Part I: Meningoencephalitis of unknown origin

Meningoencephalitides of Unknown Origin (MUO) comprises a group of non-infectious inflammatory brain conditions, which frequently cause severe neurological disease and death in dogs. Although multiple diagnostic markers have been investigated, a conclusive diagnosis, at present, essentially relies on postmortem histopathology. However, different groups of biomarkers, e.g. acute phase proteins, antibodies, cytokines, and neuro-imaging markers may prove useful in the diagnostic investigation of dogs with MUO. It appears from the current literature that acute phase proteins such as C-reactive protein are often normal in MUO, but may be useful to rule out steroid responsive meningitis-arteritis as well as other systemic inflammatory conditions. In antibody research, anti-glial fibrillary acidic protein (GFAP) may play a role, but further research is needed to establish this as a consistent marker of particularly Pug dog encephalitis. The proposed diagnostic markers often lack specificity to distinguish between the subtypes of MUO, but an increased expression of interferon-γ (IFN-γ) in necrotizing meningoencephalitis (NME) and interleukin-17 (IL-17) in granulomatous meningoencephalitis (GME) in tissue biopsies may indicate their potential as specific markers of NME and GME, respectively, suggesting further investigations of these in serum and CSF. While neuro-imaging is already an important part of the diagnostic work-up in MUO, further promising results have been shown with Positron Emission Tomography (PET) as well as proton resonance spectroscopy (¹H MRS), which may be able to detect areas of necrosis and granulomas, respectively, with relatively high specificity. This review presents different groups of established and potential diagnostic markers of MUO assessing current results and future potential.

Evaluation of cell-based and tissue-based immunofluorescent assays for detection of glial fibrillary acidic protein autoantibodies in the cerebrospinal fluid of dogs with meningoencephalitis of unknown origin and other central nervous system disorders

OBJECTIVE

To evaluate whether cell-based and tissue-based immunofluorescent assays (IFAs) run in parallel could be used to detect glial fibrillary acidic protein (GFAP) autoantibodies in the CSF of dogs with meningoencephalitis of unknown origin (MUO) and other CNS disorders.

ANIMALS

15 CSF samples obtained from dogs with presumed MUO (n = 5), CNS disease other than MUO (5), and idiopathic epilepsy (5).

PROCEDURES

All CSF samples underwent parallel analysis with a cell-based IFA that targeted the α isoform of human GFAP and a tissue-based IFA that involved mouse brain cryosections. Descriptive data were generated.

RESULTS

Only 1 CSF sample yielded mildly positive results on the cell-based IFA; that sample was from 1 of the dogs with presumed MUO. The remaining 14 CSF samples tested negative on the cell-based IFA. All 15 CSF samples yielded negative results on the tissue-based IFA.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that concurrent use of a cell-based IFA designed to target the human GFAP-α isoform and a tissue-based IFA that involved mouse tissue cryosections was inadequate for detection of GFAP autoantibodies in canine CSF samples. Given that GFAP autoantibodies were likely present in the CSF samples analyzed, these findings suggested that epitopes differ substantially between canine and human GFAP and that canine GFAP autoantibody does not bind to mouse GFAP. Without a positive control, absence of GFAP autoantibody in this cohort cannot be ruled out. Further research is necessary to develop a noninvasive and sensitive method for diagnosis of MUO in dogs.

Autoimmune glial fibrillary acidic protein astrocytopathy

Purpose of review

To describe a recently characterized autoimmune, inflammatory central nervous system (CNS) disorder known as autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy.

Recent findings

Affected patients present with symptoms of one or more of meningitis (headache and neck ache), encephalitis (delirium, tremor, seizures, or psychiatric symptoms), and myelitis (sensory symptoms and weakness). Optic disc papillitis (blurred vision) is common. CNS inflammation is evident in characteristic T1 postgadolinium enhancement of GFAP-enriched CNS regions, and lymphocytic cerebrospinal fluid (CSF) white cell count elevation. CSF is more reliable than serum for GFAP-immunoglobulin G (IgG) testing. Ovarian teratoma commonly coexists, particularly among patients with accompanying N-methyl-D-aspartate receptor or aquaporin-4 autoimmunity. Parainfectious autoimmunity is suspected in some other patients, though the culprit organism is rarely verified. Pathophysiologic relevance of T cells is underscored by neuropathology and cases of dysregulated T-cell function (HIV or checkpoint inhibitor cancer therapy). Corticosteroid-responsiveness is a hallmark of the disease. Relapses occur in approximately 20% of patients, necessitating transition to a steroid-sparing drug. Reported outcomes vary, though in the authors’ experience, early and sustained intervention usually portends recovery.

Summary

Autoimmune GFAP astrocytopathy is a treatable autoimmune CNS disease diagnosable by GFAP-IgG testing in CSF. This disease presents opportunities to explore novel mechanisms of CNS autoimmunity and inflammation.

Thoracolumbar meningeal fibrosis in pugs

Background

Thoracolumbar myelopathies associated with spinal cord and vertebral column lesions, with a similar clinical phenotype, but different underlying etiologies, occur in pugs.

Objectives

To further characterize the clinical and neuropathological characteristics of pugs with longstanding thoracolumbar myelopathy.

Animals

Thirty client‐owned pure‐bred pugs with a history of more than a month of ataxia and paresis of the pelvic limbs, suggesting a myelopathy localized to the thoracolumbar spinal cord, were included in the study.

Methods

Prospective clinicopathological study. Included pugs underwent a complete neurological examination and gross and histopathologic postmortem studies with focus on the spinal cord. Computed tomography (n = 18), magnetic resonance imaging (n = 17), and cerebrospinal fluid analysis (n = 27) were performed before or immediately after death.

Results

Twenty male and 10 female pugs had a median age at clinical onset of 84 months (interquartile range, 66‐96). Affected pugs presented with a progressive clinical course and 80% were incontinent. There was circumferential meningeal fibrosis with concomitant focal, malacic, destruction of the neuroparenchyma in the thoracolumbar spinal cord in 24/30 pugs. Vertebral lesions accompanied the focal spinal cord lesion, and there was lympho‐histiocytic inflammation associated or not to the parenchymal lesion in 43% of the pugs.

Conclusions and Clinical Importance

Meningeal fibrosis with associated focal spinal cord destruction and neighboring vertebral column lesions were common findings in pugs with long‐standing thoracolumbar myelopathy.

Glial fibrillary acidic protein immunoglobulin G as biomarker of autoimmune astrocytopathy: Analysis of 102 patients

OBJECTIVE

A novel autoimmune central nervous system (CNS) disorder with glial fibrillary acidic protein (GFAP)-IgG as biomarker was recently characterized. Here, 102 patients with GFAP-IgG positivity are described.

METHODS

The 102 included patients had: (1) serum, cerebrospinal fluid (CSF), or both that yielded a characteristic astrocytic pattern of mouse tissue immunostaining; (2) confirmation of IgG reactive with specific GFAP isoforms (α, ɛ, or κ) by cell-based assays; and (3) clinical data available. Control specimens (n = 865) were evaluated by tissue (n = 542) and cell-based (n = 323) assays.

RESULTS

Median symptom onset age was 44 years (range = 8-103), and 54% were women. The predominant phenotype (83 patients; 81%) was inflammation of meninges, brain, spinal cord, or all 3 (meningoencephalomyelitis). Among patients, highest specificity for those phenotypes was observed for CSF testing (94%), and highest sensitivity was for the GFAPα isoform (100%). Rare GFAP-IgG positivity was encountered in serum controls by tissue-based assay (0.5%) or cell-based assay (1.5%), and in CSF controls by cell-based assay (0.9%). Among patients, striking perivascular radial enhancement was found on brain magnetic resonance imaging in 53%. Although cases frequently mimicked vasculitis, angiography was uniformly negative, and spinal imaging frequently demonstrated longitudinally extensive myelitic lesions. Diverse neoplasms encountered were found prospectively in 22%. Ovarian teratoma was most common and was predicted best when both N-methyl-D-aspartate receptor-IgG and aquaporin-4-IgG coexisted (71%). Six patients with prolonged follow-up had brisk corticosteroid response, but required additional immunosuppression to overcome steroid dependency.

INTERPRETATION

GFAPα-IgG, when detected in CSF, is highly specific for an immunotherapy-responsive autoimmune CNS disorder, sometimes with paraneoplastic cause. Ann Neurol 2017;81:298-309.

Biomarkers of injury to neural tissue in veterinary medicine

There are numerous biomarkers of central and peripheral nervous system damage described in human and veterinary medicine. Many of these are already used as tools in the diagnosis of human neurological disorders, and many are investigated in regard to their use in small and large animal veterinary medicine. The following review presents the current knowledge about the application of cell-type (glial fibrillary acidic protein, neurofilament subunit NF-H, myelin basic protein) and central nervous system specific proteins (S100B, neuron specific enolase, tau protein, alpha II spectrin, ubiquitin carboxy-terminal hydrolase L1, creatine kinase BB) present in the cerebrospinal fluid and/or serum of animals in the diagnosis of central or peripheral nervous system damage in veterinary medicine.

Cellular Microbiology of Mycoplasma canis

Mycoplasma canis can infect many mammalian hosts but is best known as a commensal or opportunistic pathogen of dogs. The unexpected presence of M. canis in brains of dogs with idiopathic meningoencephalitis prompted new in vitro studies to help fill the void of basic knowledge about the organism's candidate virulence factors, the host responses that it elicits, and its potential roles in pathogenesis. Secretion of reactive oxygen species and sialidase varied quantitatively (P < 0.01) among strains of M. canis isolated from canine brain tissue or mucosal surfaces. All strains colonized the surface of canine MDCK epithelial and DH82 histiocyte cells and murine C8-D1A astrocytes. Transit through MDCK and DH82 cells was demonstrated by gentamicin protection assays and three-dimensional immunofluorescence imaging. Strains further varied (P < 0.01) in the extents to which they influenced the secretion of tumor necrosis factor alpha (TNF-α) and the neuroendocrine regulatory peptide endothelin-1 by DH82 cells. Inoculation with M. canis also decreased major histocompatibility complex class II (MHC-II) antigen expression by DH82 cells (P < 0.01), while secretion of gamma interferon (IFN-γ), interleukin-6 (IL-6), interleukin-10 (IL-10), and complement factor H was unaffected. The basis for differences in the responses elicited by these strains was not obvious in their genome sequences. No acute cytopathic effects on any homogeneous cell line, or consistent patterns of M. canis polyvalent antigen distribution in canine meningoencephalitis case brain tissues, were apparent. Thus, while it is not likely a primary neuropathogen, M. canis has the capacity to influence meningoencephalitis through complex interactions within the multicellular and neurochemical in vivo milieu.

MIP-3β/CCL19 is associated with the intrathecal invasion of mononuclear cells in neuroinflammatory and non-neuroinflammatory CNS diseases in dogs

Background

Chemokines such as MIP-3β/CCL19 are important factors in the mechanism of cell migration and pathogenesis of central nervous system (CNS) inflammatory reactions. The hypothesis of this study is that CCL19, also known as MIP-3β, is involved in the pathogenesis of inflammatory and non-inflammatory CNS diseases of dogs. Experiments were performed on cerebrospinal fluid (CSF) and serum samples of dogs affected with steroid responsive meningitis-arteritis (SRMA) during the acute phase as well as during treatment. Dogs with SRMA were compared to dogs with presumed meningoencephalomyelitis of unknown origin (MUO), and both groups sub-categorized into dogs receiving no therapy and with patients receiving prednisolone therapy. Idiopathic epilepsy (IE), a group with normal CSF cell count, was used as a control. Additionally, dogs with intervertebral disc disease (IVDD) of varying severity were analyzed. Chemokine concentrations were determined by enzyme linked immunosorbent assay. Migration assays were performed on seven selected CSF samples using a disposable 96-well chemotaxis chamber.

Results

CCL19 was detectable in CSF samples of all dogs. Dogs with untreated SRMA and MUO displayed pronounced CCL19 elevations compared to the control group and patients receiving glucocorticosteroid treatment. CSF cell counts of untreated SRMA and MUO patients were significantly positively correlated with the CCL19 CSF concentration. IVDD patients also had elevated CCL19 concentration compared to controls, but values were considerably lower than in inflammatory CNS diseases. Selected CSF samples displayed chemotactic activity for mononuclear cells in the migration assay.

Conclusions

CCL19 CSF concentrations were markedly elevated in patients affected with the neuroinflammatory diseases SRMA and MUO and showed a strong correlation with the CSF cell count. This chemokine may play an important role in the pathogenesis of SRMA and MUO. The elevation of CSF CCL19 in IVDD suggests that it may also be involved in the secondary wave of spinal cord injuries.

Unsuccessful cyclosporine plus prednisolone therapy for autoimmune meningoencephalitis in three dogs

A 4-year-old female Maltese (case 1), a 9-year-old castrated male shih tzu (case 2) and 2-year-old female Pomeranian (case 3) presented with neurological signs, such as head tilt, ataxia, circling and paresis. The three cases were tentatively diagnosed as having meningoencephalitis of unknown etiology based on computed tomography scan and cerebrospinal fluid analysis. All patients were managed with cyclosporine plus prednisolone therapy. The survival times of the three patients were 170, 70 and 21 days, respectively. After the cases died, we performed necropsy and histopathological examination for definitive diagnosis. Based on the necropsy, histopathological and immunohistochemical examinations, cases 1, 2 and 3 were definitely diagnosed as having necrotizing meningoencephalitis, necrotizing leukoencephalitis and granulomatous meningoencephalitis, respectively. This case report demonstrated the clinical findings, brain CT characteristics and histopathological and immunohistochemical features of NME, NLE and GME in dogs and discussed the reason for the relatively short survival times under cyclosporine plus prednisolone therapy.

Comprehensive Immunohistochemical Studies on Canine Necrotizing Meningoencephalitis (NME), Necrotizing Leukoencephalitis (NLE), and Granulomatous Meningoencephalomyelitis (GME)

In dogs, there are several idiopathic meningoencephalitides, such as necrotizing meningoencephalitis (NME), necrotizing leukoencephalitis (NLE), and granulomatous meningoencephalomyelitis (GME). Although they are often assumed to be immune mediated, the etiology of these diseases remains elusive. In this study, the histopathology of the lesions caused by these conditions and the inflammatory cell populations produced in response to them were examined among dogs affected with GME, NME, or NLE to understand their pathogeneses. The brain tissues of dogs with NME (n = 25), NLE (n = 5), or GME (n = 9) were used. The inflammatory cells were identified by immunohistochemistry using antibodies against CD3, IgG, CD20, CD79acy, and CD163. In NME and NLE, malacic changes were located in the cerebral cortex, as well as the cerebral white matter and thalamus, respectively. The distribution of the brain lesions in NME and NLE was breed specific. In GME, granulomatous lesions that were mostly composed of epithelioid macrophages were observed in the cerebral white matter, cerebellum, and brainstem. Although the proportions of IgG-, CD20-, and CD79acy-positive cells (B cells) were not significantly different among the GME, NME, and NLE lesions, that of CD3-positive cells (T cells) was increased in GME. In NME and NLE, CD163-positive cells (macrophages) had diffusely infiltrated the cerebral cortex and white matter, respectively. However, in GME, CD163-positive cells accumulated around the blood vessels in the cerebral and cerebellar white matter. The distributions of these lesions were quite different among GME, NME, and NLE, whereas there were no marked differences in the proportions of inflammatory cells.

Immunohistochemical characterization of inflammatory and glial responses in a case of necrotizing leucoencephalitis in a French bulldog

A 3-year-old male French bulldog was presented with blindness, staggering and ataxia and was humanely destroyed due to worsening of the neurological signs. At post-mortem examination a non-suppurative leucoencephalitis with extensive malacia within the forebrain was found. In addition, a bilateral necrotizing optic neuritis and focal retinitis was detected. Immunohistochemistry revealed a CD3(+) T-cell dominated inflammatory response with intralesional reactive astrocytes expressing glial fibrillary acidic protein. Astroglia-like cells expressing vimentin, which is characteristic of immature astrocytes, were found within the malacic lesions. The pathological findings are similar to those described in idiopathic necrotizing leucoencephalitis (NLE) of Yorkshire terriers and substantiate the hypothesis that NLE is not a breed-specific disorder that exclusively affects Yorkshire terriers, but also the French bulldog.

Changes in glial fibrillary acidic protein immunoreactivity in the dentate gyrus and hippocampus proper of adult and aged dogs

Astrocytes perform neuron-supportive tasks, repair and scarring process in the central nervous system. In this study, we observed glial fibrillary acidic protein (GFAP), a marker for astrocytes, immunoreactivity in the dentate gyrus and hippocampus proper (CA1-3 region) of adult (2-3 years of age) and aged (10-12 years of age) dogs. In the adult group, GFAP immunoreactive astrocytes were distributed in all layers of the dentate gyrus and CA1-3 region, except in the stratum pyramidale of the CA1-3 region. In the aged group, GFAP immunoreactivity decreased markedly in the molecular layer of the dentate gyrus. However, GFAP immunoreactivity in the CA1-3 region increased in all layers, and the cytoplasm of GFAP immunoreactive astrocytes was hypertrophied. GFAP protein levels in the aged dentate gyrus decreased; however, GFAP levels in the CA1-3 region increased. These results suggest that the morphology of astrocytes and GFAP protein levels in the hippocampal dentate gyrus and CA1 region are changed, respectively, with age.

Epidemiology of necrotizing meningoencephalitis in Pug dogs

Background: Although the histopathologic features of necrotizing meningoencephalitis (NME) have been described previously, little information is available concerning the signalment, geographic distribution, seasonal onset, treatment, and survival of affected dogs.

Animals: Sixty Pugs with NME and 14 contemporaneous control Pugs with other intracranial diseases (non‐NME group).

Methods: Pugs that were euthanized or died because of intracranial disease were prospectively obtained. All dogs had necropsy, histopathology, and testing for various infectious diseases and were subsequently divided into NME and non‐NME groups. Signalment, geographic distribution, seasonal onset, treatment, and survival were compared between groups.

Results: In Pugs with NME, median age at onset of clinical signs was 18 months (range, 4–113 months). A greater proportion of female dogs were present in the NME group (40/60) compared with the control group (6/14). Pugs with NME had a significantly lower mean weight (7.81 kg) than control Pugs (9.79 kg) (P= .012). Mean survival in Pugs with NME was 93 days (range, 1–680 days), with dogs receiving any form of treatment living significantly longer than those that were not treated (P= .003). Anticonvulsive drugs were the only treatment significantly associated with longer survival (P= .003).

Conclusions and Clinical Importance: NME appears to be a common cause of intracranial signs in Pugs, based on the high proportion of NME dogs reported in this population. Pugs with NME are most commonly young adult female dogs. Although further investigation is needed to determine the optimal treatment of NME, anticonvulsive drugs appear to beneficially affect duration of survival.

Necrotizing Meningoencephalitis in Five Chihuahua Dogs

An acute to chronic idiopathic necrotizing meningoencephalitis was diagnosed in 5 Chihuahua dogs aged between 1.5 and 10 years. Presenting neurologic signs included seizures, blindness, mentation changes, and postural deficits occurring from 5 days to 5.5 months prior to presentation. Cerebrospinal fluid analyses from 2 of 3 dogs sampled were consistent with an inflammatory disease. Magnetic resonance imaging of the brain of 2 dogs demonstrated multifocal loss or collapse of cortical gray/white matter demarcation hypointense on T1-weighted images, with T2-weighted hyperintensity and slight postcontrast enhancement. Multifocal asymmetrical areas of necrosis or collapse in both gray and white matter of the cerebral hemispheres was seen grossly in 4 brains. Microscopically in all dogs, there was a severe, asymmetrical, intensely cellular, nonsuppurative meningoencephalitis usually with cystic necrosis in subcortical white matter. There were no lesions in the mesencephalon or metencephalon except in 1 dog. Immunophenotyping defined populations of CD3, CD11d, CD18, CD20, CD45, CD45 RA, and CD79a immunoreactive inflammatory cells varying in density and location but common to acute and chronic lesions. In fresh frozen lesions, both CD1b,c and CD11c immunoreactive dendritic antigen-presenting cells were also identified. Immunoreactivity for canine distemper viral (CDV) antigen was negative in all dogs. The clinical signs, distribution pattern, and histologic type of lesions bear close similarities to necrotizing meningoencephalitis as described in series of both Pug and Maltese breed dogs and less commonly in other breeds.

Sera of glaucoma patients show autoantibodies against myelin basic protein and complex autoantibody profiles against human optic nerve antigens

BACKGROUND

The aim of this study was to gain more information about the possible immunological mechanisms in glaucoma. We analyzed the complex autoantibody patterns against human optic nerve antigens in sera of patients with glaucoma and tried to identify important antigens.

METHODS

Sera of 133 patients were included: healthy control subjects (n = 44), primary open-angle glaucoma (n = 44), and normal tension glaucoma patients (n = 45). The sera were tested against Western blots of human optic nerve, and antibody bands were visualized with chloronaphthol. IgG antibody patterns were analyzed by multivariate statistical techniques, and the most significant antigens were identified by mass spectrometry (Maldi-TOFTOF).

RESULTS

All subjects, even healthy ones, showed different and complex antibody patterns. Glaucoma groups showed specific up- and down-regulations of antibody reactivities compared to the control group. The multivariate analysis of discriminance found significant differences (P < 0.05) in IgG antibody profiles against human optic nerve antigens between both glaucoma groups and healthy subjects. The identified antigens include: myelin basic protein (up-regulated in the POAG group), glial fibrillary acidic protein (down-regulated in the glaucoma groups), and vimentin (down-regulated in the glaucoma groups in comparison to controls).

CONCLUSIONS

Using human optic nerve antigen, we were able to demonstrate that complex IgG autoantibody patterns exist in sera of patients with glaucoma. Large correlations between the given and our previous studies using bovine optic nerve antigens could be seen. Furthermore, anti-myelin basic protein antibodies, which can also be detected in patients with multiple sclerosis, were found in sera of glaucoma patients.