Intrathecal synthesis of major immunoglobulin classes in inflammatory diseases of the canine CNS

Neutrophil extracellular traps in CSF and serum of dogs with steroid-responsive meningitis-arteritis

In steroid-responsive meningitis-arteritis (SRMA), inflammatory dysregulation is driven by neutrophilic granulocytes resulting in purulent leptomeningitis. Neutrophils can generate neutrophil extracellular traps (NET). Uncontrolled NET-formation or impaired NET-clearance evidently cause tissue and organ damage resulting in immune-mediated diseases. The aim of the study was to verify that NET-formation is detectable in ex vivo samples of acute diseased dogs with SRMA by visualizing and measuring NET-markers in serum and cerebrospinal fluid (CSF) samples. CSF-samples of dogs with acute SRMA (n = 5) and in remission (n = 4) were examined using immunofluorescence (IF)-staining of DNA-histone-1-complexes, myeloperoxidase and citrullinated Histone H3 (H3Cit). Immunogold-labeling of H3Cit and neutrophil elastase followed by transmission electron microscopy (TEM) were used to determine ultrastructural NET-formation in the CSF of one exemplary dog. H3Cit-levels and DNase-activity were measured in CSF and serum samples using an H3Cit-ELISA and a DNase-activity-assay, respectively in patients with the following diseases: acute SRMA (n = 34), SRMA in remission (n = 4), bacterial encephalitis (n = 3), meningioma with neutrophilic inflammation (n = 4), healthy dogs (n = 6). NET-formation was detectable with IF-staining in n = 3/5 CSF samples of dogs with acute SRMA but were not detectable during remission. Vesicular NET-formation was detectable in one exemplary dog using TEM. DNase-activity was significantly reduced in dogs suffering from acute SRMA compared to healthy control group (p < 0.0001). There were no statistical differences of H3Cit levels in CSF or serum samples of acute diseased dogs compared to dogs under treatment, dogs suffering from meningioma or bacterial encephalitis or the healthy control group. Our findings demonstrate that NET-formation and insufficient NET-clearance possibly drive the immunologic dysregulation and complement the pathogenesis of SRMA. The detection of NETs in SRMA offers many possibilities to explore the aetiopathogenetic influence of this defence mechanism of the innate immune system in infectious and non-infectious canine neuropathies.

Steroid-responsive meningitis-arteritis: What have we learned since 2010? A narrative review

Steroid-responsive meningitis-arteritis (SRMA) occurs as an immune-mediated, inflammatory, and non-infectious disorder of juvenile and young-adult dogs. In principle, SRMA is divided into two clinical courses: during the typical acute form, dogs are presented with fever, cervical hyperaesthesia, and reluctance to move. The more protracted form most probably emerges after insufficient immunosuppressive treatment or relapses, with additional neurologic deficits localized in the cervical and thoracolumbar spinal cord or multifocally. The trigger leading to SRMA still remains an unsolved riddle for immunologists and clinical neurologists. In the past, many attempts have been made to clarify the etiology of this disease without success. The purpose of writing this narrative review about SRMA is to summarize new insights on the pathogenesis of SRMA with a focus on immunologic dysregulation. Furthermore, unusual manifestations of the disease, new diagnostic approaches using possible laboratory biomarkers or diagnostic imaging tools, and potential innovative treatment strategies are discussed.

Predictive Value of Acute Phase Proteins for the Short-Term Outcome of Meningoencephalitis of Unknown Origin in Dogs

Meningoencephalitis of unknown origin (MUO) is one of the most common inflammatory diseases of the central nervous system (CNS). The study evaluates the possible increase and the potential role of acute phase proteins (APPs) and other inflammatory serum parameters as biomarkers predicting the short-term outcome of dogs with meningoencephalitis of unknown origin (MUO). A retrospective cohort study was designed. The APP profile and other markers of systemic inflammation of forty-eight client-owned dogs with a new diagnosis of MUO were compared between 7-day survival and non-survival dogs diagnosed with MUO. Thirty-nine (81%) dogs were alive at the end of the 7-day follow-up period, while 9 (19%) dogs died or were euthanized because of MUO. None of the 11 markers of inflammation studied were different between the survived and non-survived dogs; for this reason, none of them could be used as a predictor of the short-term outcome based on the results of the present study. This confirms that even though MUO is often associated with a severe inflammatory status of the central nervous system (CNS), this condition is probably isolated exclusively to the CNS.

The Reibergram for immunoglobulin A in dogs: Evaluation of intrathecal IgA synthesis using a quotient graph in dogs with neurological diseases

BACKGROUND

Increased cerebrospinal fluid (CSF) protein concentration is a common finding in neurological diseases of dogs. Distinguishing between intrathecally-produced proteins and proteins that have passed the blood-CSF barrier because of barrier disruption facilitates diagnosis. Albumin is a microprotein mainly produced extrathecally that can be used as a reference marker for blood-CSF barrier dysfunction.

OBJECTIVES

Develop a quotient graph based on the CSF/serum quotient of albumin and immunoglobulin A (IgA; Reibergram) to visualize intrathecal IgA synthesis and blood-CSF barrier dysfunction.

ANIMALS AND METHODS

Retrospective single-center cohort study. A hyperbolic function was developed using data from 6 healthy Beagles and 38 dogs with neurological diseases in which an isolated blood-CSF barrier dysfunction was expected. The function was validated using data from 10 dogs with expected intrathecal IgA synthesis and was visualized as a quotient graph. Finally, the graph was used to evaluate data of 118 dogs with various neurological diseases.

RESULTS

Within the Reibergram, the function QLim IgA = 0.13 QAlb 2 + 11.9 · 10 - 6 - 1.01 · 10 - 3 describes the upper values of physiological IgA quotients. It detects diseases with expected intrathecal IgA synthesis with higher sensitivity (85%) and specificity (89%) than the IgA index. The upper value of the physiological albumin quotient is 2.22 and detects diseases with expected blood-CSF barrier dysfunction (sensitivity: 81%; specificity: 88%).

CONCLUSION AND CLINICAL IMPORTANCE

The canine Reibergram can detect blood-CSF barrier dysfunction and intrathecal IgA synthesis in the majority of cases. The graphical visualization simplifies data evaluation and makes it a feasible tool in routine CSF diagnostic testing.

The utility of Coccidioides antigen and antibody detection in cerebrospinal fluid in the diagnosis of canine central nervous system coccidioidomycosis

OBJECTIVE

To evaluate the utility of enzyme immunoassays (EIAs) for the detection of Coccidioides antigen and antibody in CSF in the diagnosis of CNS coccidioidomycosis in dogs.

ANIMALS

51 dogs evaluated for CNS disease in a single specialty center in Tucson in 2016.

PROCEDURES

Excess CSF after routine analysis was banked after collection from dogs presented to the neurology service. Samples were tested by EIA for presence of Coccidioides antigen and antibody. Clinical data were collected from medical records retrospectively.

RESULTS

22 dogs were diagnosed with CNS coccidioidomycosis (CCM) or another neurologic disease (non-CCM). These groups of dogs overlapped in the presenting complaints, MRI results, and routine CSF analysis results. Four dogs, all with CCM, had positive antigen EIA results. With clinical diagnosis used as the reference standard, CSF antigen testing had low sensitivity (20%) but high specificity (100%) for diagnosis of CCM. Ten dogs with CCM and 4 dogs with other diagnoses had antibody detected in CSF by EIA. Sensitivity of CSF antibody testing was 46%, specificity was 86%, and positive and negative predictive values for the study population were 71% and 68%, respectively.

Clinical Relevance

Diagnosis of CNS coccidioidomycosis in dogs in an endemic region was hampered by overlap of clinical signs with other neurologic disorders and the low sensitivity of confirmatory diagnostics. The evaluated Coccidioides-specific EIAs performed on CSF can aid in the diagnosis. A prospective study is warranted to corroborate and refine these preliminary findings.

Biomarkers of non-infectious inflammatory CNS diseases in dogs: Where are we now? Part 2 - Steroid responsive meningitis-arteritis

Steroid responsive meningitis-arteritis (SRMA) in dogs causes severe inflammation of meningeal arteries leading to generalized meningitis with possible neurological signs, as well as a systemic inflammatory response. The etiology and exact pathogenesis are unknown, but an immune-mediated origin has been suggested and is supported by a positive response to immunosuppressive treatment with corticosteroids. A collection of clinical and paraclinical characteristics may be highly indicative of SRMA, but a single and conclusive diagnostic test or biomarker is currently not available. The aim of this review is to provide an overview of the current understanding and knowledge on SRMA, with special emphasis on potential biomarkers and their applicability in the diagnostic work-up. Though no specific markers for SRMA currently exist, clinically useful markers include IgA and several acute phase proteins e.g. C-reactive protein. A frequent problem of both acknowledged and proposed biomarkers, is, however, their inability to effectively differentiate SRMA from other systemic inflammatory conditions. Other proposed diagnostic markers include genetic markers, acute phase proteins such as serum amyloid A, cytokines such as interleukin-17 and CC-motif ligand 19, endocannabinoid receptors and heat shock protein 70; these suggestions however either lack specificity or need further investigation.

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.

Measurement of Neutrophil Gelatinase-Associated Lipocalin Concentration in Canine Cerebrospinal Fluid and Serum and Its Involvement in Neuroinflammation

Neutrophil gelatinase-associated Lipocalin (NGAL) is a glycoprotein involved in inflammation acting as an acute phase protein and chemokine as well as a regulator of iron homeostasis. NGAL has been shown to be upregulated in experimental autoimmune encephalomyelitis (EAE) in mice. Increased NGAL concentration in cerebrospinal fluid (CSF) and expression in central nervous system (CNS) has been described in human neuroinflammatory disease such as multiple sclerosis and neuropsychiatric lupus as well as in bacterial meningitis. We aimed to investigate involvement of NGAL in spontaneous canine neuroinflammation as a potential large animal model for immune- mediated neurological disorders. A commercially available Enzyme-linked Immunosorbent Assay (ELISA) for detection of canine NGAL was validated for use in canine CSF. Concentration in CSF and serum of canine patients suffering from steroid- responsive meningitis- arteriitis (SRMA), Meningoencephalitis of unknown origin (MUO), different non- inflammatory CNS disease and control dogs were compared. Relationship between NGAL concentration in CSF and serum and inflammatory parameters in CSF and blood (IgA concentration, total nucleated cell count (TNCC), protein content) as well as association with erythrocytes in CSF, duration of illness, plasma creatinine and urinary leucocytes were evaluated. In dogs with SRMA and MUO, CSF concentration of NGAL was significantly higher than in dogs with idiopathic epilepsy, compressive myelopathy, intracranial neoplasia and SRMA in remission (p < 0.0001). Patients with acute SRMA had significantly higher levels of NGAL in CSF than neurologically normal controls (p < 0.0001). Serum NGAL concentrations were significantly higher in dogs with SRMA than in patients with myelopathy and intracranial neoplasia (p < 0.0001). NGAL levels in CSF were strongly positively associated with IgA concentration (rSpear= 0.60116, p < 0.0001), TNCC (rSpear= 0.65746, p < 0.0001) and protein content (rSpear= 0.73353, p < 0.0001) in CSF. It can be measured in CSF of healthy and diseased dogs. Higher concentrations in canine patients with SRMA as well as positive association with TNCC in CSF suggest an involvement in pro-inflammatory pathways and chemotaxis in SRMA. High serum levels of NGAL in serum of SRMA patients in different stages of disease might reflect the systemic character of the disease.

Neurological manifestations in dogs naturally infected by Leishmania infantum: descriptions of 10 cases and a review of the literature

In order to evaluate possible nervous system involvement in canine leishmaniasis, retrospective evaluation of all medical records of leishmaniotic dogs exhibiting neurological signs referred to our hospital over a 5-year period was performed. The records of 10 dogs were reviewed. Depending on the neuroanatomical localisation, the dogs underwent advanced diagnostic imaging, cerebrospinal fluid analysis, electrodiagnostic testing and histopathologic evaluations. The final neurological diagnosis was: meningoencephalitis (n=2), brain haemorrhagic stroke (n=1), haemorrhagic choroiditis (n=1), meningomyelitis (n=2), ischaemic myelopathy (n=1), polymyositis (n=2) and peripheral neuropathy (n=1). This study confirms that both central and peripheral nervous systems can be affected by leishmaniasis and provides an overview on the possible etiopathogenetic mechanisms. In addition, clinical and diagnostic findings, therapy and follow-up of affected dogs are described.

Th17-skewed immune response and cluster of differentiation 40 ligand expression in canine steroid-responsive meningitis-arteritis, a large animal model for neutrophilic meningitis

Background

Steroid-responsive meningitis-arteritis (SRMA) is an immune-mediated disorder characterized by neutrophilic pleocytosis and an arteritis particularly in the cervical leptomeninges. Previous studies of the disease have shown increased levels of IL-6 and TGF-ß₁ in cerebrospinal fluid (CSF). In the presence of these cytokines, naive CD4+ cells differentiate into Th17 lymphocytes which synthesize interleukin 17 (IL-17). It has been shown that IL-17 plays an active role in autoimmune diseases, it induces and mediates inflammatory responses and has an important role in recruitment of neutrophils. The hypothesis of a Th17-skewed immune response in SRMA should be supported by evaluating IL-17 and CD40L, inducing the vasculitis.

Methods

An enzyme-linked immunosorbent assay (ELISA) was performed to measure IL-17 and CD40L in serum and CSF from a total of 79 dogs. Measurements of patients suffering from SRMA in the acute state (SRMA A) were compared with levels of patients under treatment with steroids (SRMA T), recurrence of the disease (SRMA R), other neurological disorders, and healthy dogs, using the two-part test. Additionally, secretion of IL-17 and interferon gamma (IFN-γ) from the peripheral blood mononuclear cells (PBMCs) was confirmed by an enzyme-linked immunospot (ELISpot) assay.

Results

Significant higher levels of IL-17 were found in CSF of dogs with SRMA A compared with SRMA T, other neurological disorders and healthy dogs (p < 0.0001). In addition, levels of CD40L in CSF in dogs with SRMA A and SRMA R were significantly higher than in those with SRMA T (p = 0.0004) and healthy controls (p = 0.014). Furthermore, CSF concentrations of IL-17 and CD40L showed a strong positive correlation among each other (rSpear = 0.6601; p < 0.0001) and with the degree of pleocytosis (rSpear = 0.8842; p < 0.0001 and rSpear = 0.6649; p < 0.0001, respectively). IL-17 synthesis from PBMCs in SRMA patients was confirmed; however, IL-17 is mainly intrathecally produced.

Conclusions

These results imply that Th17 cells are inducing the autoimmune response in SRMA and are involved in the severe neutrophilic pleocytosis and disruption of the blood-brain barrier (BBB). CD-40L intrathecal synthesis might be involved in the striking vasculitis. The investigation of the role of IL-17 in SRMA might elucidate important pathomechanism and open new therapeutic strategies.

Interleukin-6, vascular endothelial growth factor and transforming growth factor beta 1 in canine steroid responsive meningitis-arteritis

Background

Steroid Responsive Meningitis-Arteritis (SRMA) is a common cause of inflammation of the canine central nervous system (CNS). To investigate if transforming growth factor beta 1 (TGF-β₁), interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) are involved in the production of excessive immunoglobulin A (IgA), the induction of acute phase proteins and in the development of a systemic necrotizing vasculitis, characteristic of SRMA, these three signalling proteins were evaluated.

Results

Cerebrospinal fluid (CSF) and serum samples of dogs during the acute phase of SRMA (SRMA) were tested for IL-6, VEGF and TGF- β₁. Results were compared to those of dogs affected with SRMA during treatment (SRMA Th) and during relapse (SRMA R), to dogs with other meningoencephalomyelitides (ME), with miscellaneous non-inflammatory diseases of the CNS (CNS-Mix), with idiopathic epilepsy (IE), with systemic inflammatory diseases (Syst. Infl.) and with healthy dogs (Healthy). Concentrations of IL-6 and VEGF in CSF were significantly elevated in the SRMA group compared to the other disease categories (p < 0.05). The CSF concentrations of TGF-β₁ were increased in SRMA group, but statistically significant differences were found only in comparison with Healthy and CNS-Mix groups. No differences were detected in the serum concentrations of TGF-β₁ between the different groups. In untreated SRMA patients, a positive correlation (r_Spear = 0.3549; P = 0.0337) between concentrations of TGF-β₁ and IgA concentration was found in CSF, while concentrations of IL-6 and VEGF in CSF positively correlated with the degree of pleocytosis (r_Spear = 0.8323; P < 0.0001 and r_Spear = 0.5711; P = 0.0166, respectively).

Conclusions

Our results suggest that these three signalling proteins are biomarkers of disease activity in SRMA. VEGF might play an important role in the development of a systemic arteritis. TGF-β₁ is considered to be involved in the excessive IgA production, while IL-6 in the pleocytosis. The combined intrathecal increase of TGF-β₁ and IL-6 detected in SRMA could possibly force CD4 progenitors to differentiate towards the newly described Th17 lymphocyte subset and enhance the autoimmune response.

Evaluation of a microsphere-based immunofluorescence assay for the determination of Immunoglobulin A concentrations in cerebrospinal fluid of dogs

The simultaneous increase of immunoglobulin A (IgA) in serum and cerebrospinal fluid (CSF) is a characteristic finding in dogs suffering from canine steroid-responsive meningitis-arteritis (SRMA). The study aimed at developing and evaluating a microsphere-based immunofluorescence assay (MIA) for the measurement of IgA, trying to fulfill the need of a quicker method using only small volumes of CSF. Microsphere beads were coated with goat-anti-dog IgA antibodies and bound IgA was detected by a mouse-anti-dog IgA antibody in combination with a PE-labeled goat-anti-mouse IgG. CSF from 44 dogs were tested for IgA and compared with an in-house utilized ELISA. Using clinical relevant reference ranges, the new method showed a good agreement (84.17%) with the ELISA. A method comparison revealed a moderate agreement only. These findings indicate that the MIA will not replace the ELISA, but it opens the possibility for further research with microsphere-based assays.

The role of pro- and anti-inflammatory cytokines in the pathogenesis of spontaneous canine CNS diseases

Dogs are comparatively frequently affected by various spontaneously occurring inflammatory and degenerative central nervous system (CNS) conditions, and immunopathological processes are a hallmark of the associated neuropathology. Due to the low regenerative capacity of the CNS a sophisticated understanding of the underlying molecular basis for disease initiation, progression and remission in canine CNS diseases represents a prerequisite for the development of novel therapeutical approaches. In addition, as many spontaneous canine CNS diseases share striking similarities with their human counterpart, knowledge about the immune pathogenesis may in part be translated for a better understanding of certain human diseases. In addition to cytokine-driven differentiation of peripheral leukocytes including different subsets of T cells recent research suggests a pivotal role of these mediators also in phenotype polarization of resident glial cells. Cytokines thus represent the key mediators of the local and systemic immune response in CNS diseases and their orchestration significantly decides on either lesion progression or remission. The aim of the present review is to summarize the growing number of data focusing on the molecular basis of the immune response during spontaneous canine CNS diseases and to detail the effect of cytokines on the immune pathogenesis of selected idiopathic, infectious, and traumatic canine CNS diseases. Steroid-responsive meningitis arteritis (SRMA) represents a unique idiopathic disease of leptomeningeal blood vessels characterized by excessive IgA secretion into the cerebrospinal fluid. Recent reports have given sophisticated insights into the cytokine-driven, immune-mediated pathogenesis of SRMA that is characterized by a biased T helper 2 cell response. Canine distemper associated leukoencephalitis represents an important spontaneously occurring disease that allows investigations on the basic pathogenesis of immune-mediated myelin loss. It is characterized by an early virus-induced up-regulation of pro-inflammatory cytokines with chronic bystander immune-mediated demyelinating processes. Lastly, canine spinal cord injury (SCI) shares many similarities with the human counterpart and most commonly results from intervertebral disk disease. The knowledge of its pathogenesis is largely restricted to experimental studies in rodents, and the impact of immune processes that accompany secondary injury is discussed controversially. Recent investigations on canine SCI highlight the pivotal role of pro-inflammatory cytokine expression that is paralleled by a dominating reaction of microglia/macrophages potentially indicating a polarization of these immune cells into a neurotoxic and harmful phenotype. This report will review the role of cytokines in the immune processes of the mentioned representative canine CNS diseases and highlight the importance of cytokine/cytokine interaction as a useful therapeutic target in canine CNS diseases.

Extracellular hsp70 release in canine Steroid Responsive Meningitis-Arteritis

The role of extracellular 70 kDa heat shock protein 70 (ehsp70) in central nervous system inflammation is vastly understudied, despite evidence supporting the ability to drive a pro-inflammatory state. We investigated the presence of ehsp70 in cerebrospinal fluid (CSF) and serum of dogs with Steroid Responsive Meningitis-Arteritis (SRMA), with the hypothesis that an ehsp70 response would occur, and might play a role in the pathogenesis of this disease. Samples from 30 dogs acutely affected with SRMA, and 30 dogs treated with corticosteroids and currently in clinical remission from SRMA were compared with normal dogs. Serum and CSF concentrations of ehsp70 were quantified using an enzyme-linked immunosorbent assay. An ehsp70 response occurred in the CSF of dogs with SRMA and this response was attenuated by corticosteroid treatment. There was no correlation between serum and CSF concentrations of ehsp70, supporting local production and release of ehsp70 and not simply leakage from serum. Dogs with SRMA thus represent a powerful spontaneous model by which to study the role of ehsp70 in CNS inflammation.

Conventional and molecular diagnostic testing for the acute neurologic patient

OBJECTIVE

The aim of this review is to describe and evaluate both conventional and molecular diagnostic testing utilized in dogs and cats with acute neurologic diseases. Various types of polymerase chain reaction (PCR) are explored along with novel molecular diagnostic testing that ultimately may prove useful in the critical care setting.

DATA SOURCES

PUBMED was searched to obtain relevant references material using keywords: 'canine OR feline meningitis AND meningoencephalitis,''feline infectious peritonitis,''canine distemper,''canine OR feline AND toxoplasma,''canine neospora,''canine OR feline AND rickettsia,''granulomatous meningoencephalitis,''steroid responsive meningitis arteritis,''necrotizing encephalitis,''novel neurodiagnostics,''canine OR feline AND CNS borrelia,''canine OR feline AND CNS bartonella,''canine OR feline AND CNS fungal,''nested OR multiplex OR degenerate OR consensus OR CODEHOP AND PCR.' Research findings from the authors' laboratory and current veterinary textbooks also were utilized.

HUMAN DATA SYNTHESIS

Molecular diagnostic testing including conventional, real-time, and consensus and degenerate PCR and microarray analysis are utilized routinely for the antemortem diagnosis of infectious meningoencephalitis (ME) in humans. Recently, PCR using consensus degenerate hybrid primers (CODEHOP) has been used to identify and characterize a number of novel human viruses.

VETERINARY DATA SYNTHESIS

Molecular diagnostic testing such as conventional and real-time PCR aid in the diagnosis of several important central nervous system infectious agents including canine distemper virus, Toxoplasma gondii, Neospora caninum, rickettsial species, and others. Recently, broadly reactive consensus and degenerate PCR reactions have been applied to canine ME including assays for rickettsial organisms, Borrelia spp. and Bartonella spp., and various viral families.

CONCLUSIONS

In the acute neurologic patient, there are several key infectious diseases that can be pursued by a combination of conventional and molecular diagnostic testing. It is important that the clinician understands the utility, as well as the limitations, of the various neurodiagnostic tests that are available.

An update on steroid responsive meningitis-arteritis

Steroid responsive meningitis-arteriitis (SRMA) is an immunemediated disorder commonly recognised in dogs in small animal practice. Two different forms of SRMA may occur. The typical, acute form of SRMA is characterised by cervical rigidity, pain, pyrexia and a polymorphonuclear pleocytosis of the cerebrospinal fluid (CSF). In a less common, chronic form of SRMA, additional neurological deficits consistent with a spinal cord or a multi-focal neurological disorder may be present, often accompanied by a mononuclear CSF pleocytosis. The prognosis for young dogs in the acute stage of SRMA is relatively good with early and aggressive anti-inflammatory or immunosuppressive therapy. In more protracted, relapsing cases of SRMA the prognosis is guarded, and therapy requires more aggressive, long term immunosuppression. The complete etiopathogenesis of SRMA is unknown; however, an aberrant immune response directed against the central nervous system (CNS) is most likely. Neutrophilic pleocytosis in SRMA seems to be facilitated by chemotactic factors in the CSF and upregulation of integrins and metalloproteinases that disrupt the blood brain barrier. Upregulation of IgA, induced by a Th2 immune response, also plays a central role in the pathogenesis of SRMA.

Marked MMP-2 transcriptional up-regulation in mononuclear leukocytes invading the subarachnoidal space in aseptic suppurative steroid-responsive meningitis-arteritis in dogs

Canine Steroid-Responsive Meningitis-Arteritis (SRMA) is a suitable animal model for studies on the development of neutrophilic pleocytosis in aseptic meningitis. Samples of dogs in the acute phase of SRMA (n=16) were examined for gene expression of matrix metalloproteinases (MMP)-2 and -9 and tissue inhibitors of metalloproteinases (TIMP)-1 and -2. Results were compared to those of dogs under glucocorticosteroid treatment for SRMA (n=16) and dogs with other inflammatory and neoplastic diseases of the central nervous system (CNS) (n=19). Samples included mononuclear (PBMCs) and polymorphonuclear cells (PBPMNs) of peripheral blood and cerebrospinal fluid white blood cells (CSF WBCs). In the acute phase of SRMA CSF WBCs showed mRNA expression for MMP-2 and -9 and TIMP-1 and -2, highlighting a contribution of these cells to the overall content of MMPs and TIMPs in CSF. MMP-2 mRNA levels in CSF WBCs were significantly up-regulated in comparison to PBMC expression levels, suggesting that MMP-2 is relevant for PBMC invasion into the subarachnoidal space and that the expression is influenced by migratory activity through the blood-CSF-barrier.

Disproportionally strong increase of B cells in inflammatory cerebrospinal fluid of dogs with Steroid-responsive Meningitis-Arteritis

Steroid-responsive Meningitis-Arteritis (SRMA) is a systemic inflammatory disease of juvenile to young adult dogs with a relapsing course and most prominent manifestation in the cervical meninges. Immunophenotyping and flow cytometric measurement of lymphocytes in peripheral blood (PB) and CSF was performed in the acute phase of SRMA (n=12) and during glucocorticosteroid treatment (n=10). Values were compared to those from dogs with other neurologic diseases (n=63) and healthy individuals (n=7). Dogs with SRMA had high CD4:CD8alpha ratios in PB and low T:B cell ratios in PB and CSF suggesting that a T(H)2-mediated immune response occurs. The T:B cell ratio in CSF was markedly lower than that in PB indicating that either a selective recruitment of B cells or, alternatively, their strong intrathecal proliferation takes place. SRMA appears to be a valuable animal model for the investigation of compartmentalization of immune responses and for studies on differences in local central nervous system and systemic immune responses.

Cerebrospinal Fluid

This chapter discusses the anatomy, functions, and biochemistry of cerebrospinal fluid (CSF). CSF has four major functions: physical support of neural structures, excretion and “sink” action, intracerebral transport, and control of the chemical environment of the central nervous system. CSF provides a “water jacket” of physical support and buoyancy. The CSF is protective because its volume changes reciprocally with changes in the volume of intracranial contents, particularly blood. Thus, the CSF protects the brain from changes in arterial and central venous pressure associated with posture, respiration, and exertion. Acute or chronic pathological changes in intracranial contents can be accommodated, to a point, by changes in the CSF volume. The direct transfer of brain metabolites into the CSF provides excretory function. This capacity is important because the brain lacks a lymphatic system. The lymphatic function of the CSF is also manifested in the removal of large proteins and cells, such as bacteria or blood cells, by bulk CSF absorption. The “sink” action of the CSF arises from the restricted access of water-soluble substances to the CSF and the low concentration of these solutes in the CSF.

Aseptic Suppurative Meningitis in Juvenile Boxer Dogs: Retrospective Study of 12 Cases

Immune-mediated central nervous system inflammation is described in a series of 12 juvenile boxer dogs. A diagnosis of steroid-responsive meningitis-arteritis was made based on the clinical presentation and on diagnostic findings. The boxer breed was at a higher risk for this inflammatory condition than other breeds. Long-term follow-up (&gt;2 years) confirmed a better prognosis in this breed than in the beagle and the Bernese mountain dog. Complete resolution of clinical signs without significant deficits or recurrences was obtained in all cases. Early clinical recognition and immunosuppressive treatment resulted in a better response and complete resolution of the disorder.

Long-term treatment of dogs with steroid-responsive meningitis-arteritis: clinical, laboratory and therapeutic results

Steroid-responsive meningitis-arteritis is an immunopathological disease in dogs characterised by neck pain, pleocytosis of the cerebrospinal fluid (CSF) and increased serum and CSF immunoglobulin (Ig) A levels. A long-term treatment protocol (four to 20 months) with prednisolone was applied in 10 dogs with the condition. Clinical side effects, changes in blood and CSF values and long-term outcome were evaluated retrospectively. Eight of the 10 dogs were without clinical signs up to 29 months after the treatment was terminated. Long-term glucocorticosteroid treatment appears to result only in mild clinical side effects, such as polyuria/polydipsia, polyphagia and weight gain. All clinical and laboratory changes were reversible after the therapy was discontinued. Elevated serum and CSF IgA levels did not decrease to normal values during prednisolone treatment and were still slightly increased after the therapy was discontinued. A marked decrease in the cell count of the CSF was observed after therapy was initiated, although pleocytosis increased again during relapses of the disease. Monitoring of CSF cell count in dogs with this condition seems to be a sensitive indicator of success of treatment. In addition, older dogs with high IgA levels in the CSF and frequent relapses seem to require a longer duration of therapy and have a less favourable prognosis long term. The reason for high systemic and intrathecally produced IgA levels remains unknown, but seems not to be influenced by prednisolone treatment.

Total serum IgE and IgA antibody levels in healthy dogs of different breeds and exposed to different environments

Total serum immunoglobulin (Ig) E and A levels were analysed in 233 healthy dogs as basis for comparison with atopic dogs in future studies. They were measured by ELISA in a group of non- colonised dogs of various breeds (group A) and three groups of colonised dogs including one German Shepherd and two Beagle kennels (groups B-D). IgE levels from non-colonised dogs were significantly higher than the ones of German Shepherds and Beagles C (P<0.05). IgA levels were alike in all groups except for the German Shepherds which displayed the lowest levels. Age and sex were not identified as common significant cofactors for IgE and IgA levels in all groups and IgE levels correlated negatively with IgA only in non-colonised dogs. In conclusion, IgE and IgA levels seem to be mainly influenced by genetic background. Thus use of total serum IgE as a diagnostic tool in the atopic dogs required extensive family data and therefore appears most suitable for research purposes within specific, well defined dog populations.

Chemotactic activity and IL-8 levels in the cerebrospinal fluid in canine steroid responsive meningitis-arteriitis

Steroid responsive meningitis-arteriitis (SRMA) is a systemic immune disorder, characterized by inflammatory-stenosing lesions of the meningeal arteries and meningitis. The predilection of the disease for the central nervous system (CNS) remains unexplained. In this study, chemotactic activity and chemotactic factors were measured in the cerebrospinal fluid (CSF) of dogs with SRMA. CSF of dogs with SRMA exerted a marked chemotactic activity for leukocytes. Neutrophils were attracted to a similar degree as by CSF from animals with bacterial encephalitis. Chemotactic activity was also noted for mononuclear cells, however, by far weaker than in CSF from animals with viral encephalitis. While the inflammatory process could be suppressed with glucocorticoid treatment, the chemotactic activity of CSF persisted. We could identify IL-8-like activities using a desensitization assay in the CSF of animals with SRMA and also found increased IgA levels. Increased chemotactic activity for polymorphonuclear leukocytes correlated positively with the levels of IL-8-like activity in CSF. Our observations clearly suggest that in SRMA chemotactic factors are generated in the CNS. These include IL-8, but probably also others. The intensity of this production appears to correlate with IgA levels in the CSF suggesting either a causal link or reflecting the severity of the inflammation.

Inflammatory diseases of the central nervous system in dogs

Inflammatory diseases of the central nervous system (CNS) are important causes of seizures in dogs. Specific diseases include canine distemper, rabies, cryptococcosis, coccidioidomycosis, toxoplasmosis, neosporosis, Rocky Mountain spotted fever, ehrlichiosis, granulomatous meningoencephalomyelitis, and pug dog encephalitis. Inflammatory disorders should be considered when a dog with seizures has persistent neurological deficits, suffers an onset of seizures at less than 1 or greater than 5 years of age, or exhibits signs of systemic illness. A thorough history, examination, and analysis of cerebrospinal fluid are important in the diagnosis of inflammatory diseases. However, even with extensive diagnostic testing, a specific etiology is identified in less than two thirds of dogs with inflammatory diseases of the CNS.

Lymphocyte subsets and CD45RA positive T-cells in normal canine cerebrospinal fluid

In order to evaluate changes in lymphocyte subpopulations of cerebrospinal fluid (CSF) cells in neurological diseases, normal control data have to be established. In this study we evaluated CSF samples from 65 dogs of both sexes and various breeds with an age range between 5 months and 6 years, and 20 one-year-old healthy inbred Beagles. For comparison, blood samples from 10 healthy dogs were examined. 14 different antibodies against leukocyte surface markers were used. The subpopulations were evaluated using flow cytometry (FACS) and immunocytochemistry. It could be shown that lymphocyte populations in CSF differ from peripheral blood in a few subsets. A relatively high degree of individual variation was found, not only in dogs of different breeds and ages, but also in the inbred Beagle population. These large individual variations suggest that repeated paired CSF-blood samples during the course of neurological disease should be examined within the same individual to obtain meaningful results. CD3+ and CD4+ T-cells were significantly lower in normal CSF. Of great interest is the fact, that T-cells, characterized by double staining CD3/CD45RA are present in variable numbers in normal CSF. In other species they are known to be naive or resting T-cells. CD4/CD45RA positive cells seem to be an important subpopulation of these CD45RA positive T-cells. Furthermore, by far more CD11b positive lymphocytes were observed in the CSF than in the peripheral blood and these are not large granular lymphocytes. The present study shows that systematic FACS analysis of CSF is feasible in larger animals such as dogs.

Diagnosis of inflammatory and infectious diseases of the central nervous system in dogs: a retrospective study

The medical records of 220 dogs with inflammatory/infectious diseases of the central nervous system (CNS) were retrospectively examined. The aims of the study were to determine if clinical and clinicopathologic data (not including biopsy or necropsy examination) could distinguish inflammatory CNS diseases from diseases of other types, and to search for criteria allowing differentiation of specific inflammatory diseases. The signalment, historical findings, extraneural and neurological signs, and the lesion site contributed marginally to a specific diagnosis. Multifocal signs were only noticed in one third of the dogs with inflammatory/infectious diseases. Particular neurological abnormalities were more frequent in certain diseases than in others (eg, myoclonus was frequent in dogs with distemper, but it was also found in those with other meningoencephalomyelitides). Hematologic findings contributed to the diagnosis in certain conditions (eg, canine distemper encephalitis, protozoal encephalomyelitis, steroid-responsive meningitis-arteritis). Cerebrospinal fluid examinations, including immunoglobulin G index and cytology were useful to separate meningoencephalomyelitides from the other CNS diseases and to distinguish certain conditions from others. In most cases a specific diagnosis depended on a combination of clinical signs and ancillary diagnostic aids. Still, a specific diagnosis remained very difficult, if not impossible, in at least one third of the dogs.

Neuroimmunological studies in steroid-responsive meningitis-arteritis in dogs

The clinical and pathological expression of steroid-responsive meningitis-arteritis (SRMA) is predominantly neurological and the present study was therefore mostly concerned with the intrathecal humoral immune responses of 13 dogs suffering from the disease. All the dogs synthesised IgG intrathecally, indicating that the immune response in SRMA is in part specifically directed towards the central nervous system (CNS). Half of the dogs also had high levels of IgM only in the cerebrospinal fluid (CSF) and nearly all of them had high levels of IgA in the CSF as well as in the serum. Six of the dogs had circulating immune complexes in the serum, but not in the CSF. Neither IgM nor IgA rheumatoid factors were found. A chemotaxis assay revealed enhanced migration of neutrophils into the CSF in three cases. All the dogs had marked meningeal inflammation and arterial lesions of the meningeal blood vessels. Only one dog had arterial involvement outside the CNS. The acute vascular lesions consisted mostly of degenerative changes of the media and periarterial inflammation, and there was no evidence of immune complex deposition. Chronic lesions were mostly characterised by stenosis, adventitial thickening and periarteritis. Focal deposits of IgA were found in the vascular wall of one chronic case. It was concluded that the meningeal lesions in SRMA are a primary event, rather than the result of a generalised immune complex disease. These lesions are associated with an intrathecal humoral immune response, in which IgA appears to play a central role.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoreactivity of the central nervous system in cats with a Borna disease-like meningoencephalomyelitis (staggering disease)

The inflammatory cell composition and the expression of major histocompatibility complex (MHC) antigens in the central nervous system (CNS) of 13 cats with a spontaneous, Borna disease-like meningoencephalomyelitis (staggering disease) was investigated by immunohistochemistry with a panel of monoclonal and polyclonal antibodies. T lymphocytes were the predominating inflammatory cells within the adventitial space. CD4+ T cells were more abundant than CD8+ T cells. Scattered IgG-, IgA- and IgM-containing cells were found in the adventitial space and surrounding neuropil, often adjacent to neurons. There was a markedly increased MHC class II expression in cells morphologically resembling microglia. In several cats, Borna disease virus specific antigen was detected, but only in a few cells, mainly of macrophage character. Our findings indicate a long-standing inflammatory reaction in the CNS of cats with staggering disease, possibly triggered and sustained by a persistent viral infection.