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

Magnetic resonance imaging findings in dogs with steroid-responsive meningitis-arteritis in the UK and their clinical significance: 53 cases (2013-2021)

OBJECTIVES

To describe the MRI findings in a UK referral population of dogs with steroid-responsive meningitis-arteritis and to determine if they were associated with any specific clinical features or outcomes.

MATERIALS AND METHODS

We performed a multi-centre retrospective case series of dogs diagnosed with steroid-responsive meningitis-arteritis in the UK that underwent MRI. Blinded consensus review of the MRI studies was performed and the findings described. The presence or absence of specific MRI abnormalities were analysed for significant associations with presenting signs, results of investigations or case outcomes.

RESULTS

Fifty-three dogs were included. The most common MRI findings were paravertebral muscle changes (30/53; 56.6%), meningeal contrast enhancement (13/41; 31.7%) and spinal cord parenchymal T2-W hyperintensity (15/53; 28.3%). Haemorrhage was observed in five of 53 (9.4%) cases - three intradural-extramedullary, one intramedullary and one extradural. Following binary logistic regressions, T2-W spinal cord parenchymal hyperintensity had a significant positive association with paresis/paralysis (odds ratio 14.86, 95% confidence interval 1.42 to 154.99) as did haemorrhage (odds ratio 16.12, confidence interval 2.05 to 126.73). Fifty-two (98.1%) dogs survived to discharge. Relapse occurred in nine of 29 (31.0%) dogs with sufficient follow-up, and no MRI finding had a significant relationship with its occurrence.

CLINICAL SIGNIFICANCE

Magnetic resonance imaging findings for steroid-responsive meningitis-arteritis can be severe and extensive, as can the clinical presentation. The presence of paresis/paralysis should raise concern for haemorrhage, though most dogs still have a good prognosis.

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.

Elevated Interleukin-31 Levels in Serum, but Not CSF of Dogs with Steroid-Responsive Meningitis-Arteritis Suggest an Involvement in Its Pathogenesis

Steroid-responsive meningitis-arteritis (SRMA) is a predominantly Th-2 immune-mediated disease, but the exact pathomechanism remains unclear. Interleukin-31 (IL-31) is predominantly produced by T cells with a Th-2 phenotype during proinflammatory conditions. We hypothesize that IL-31 might be involved in the pathogenesis of SRMA. IL-31 was measured in archived samples (49 serum and 52 CSF samples) of dogs with SRMA, meningoencephalitis of unknown origin (MUO), infectious meningoencephalitis, and atopic dermatitis, and of healthy control dogs using a competitive canine IL-31 ELISA. The mean serum IL-31 level in dogs with SRMA (n = 18) was mildly higher compared to dogs with atopic dermatitis (n = 3, p = 0.8135) and MUO (n = 15, p = 0.7618) and markedly higher than in healthy controls (n = 10, p = 0.1327) and dogs with infectious meningoencephalitis (n = 3, no statistics). Dogs with SRMA in the acute stage of the disease and without any pre-treatment had the highest IL-31 levels. The mean CSF IL-31 value for dogs with SRMA (n = 23) was quite similar to that for healthy controls (n = 8, p = 0.4454) and did not differ markedly from dogs with MUO (n = 19, p = 0.8724) and infectious meningoencephalitis. Based on this study, an involvement of IL-31 in the pathogenesis of the systemic Th-2 immune-mediated immune response in SRMA can be assumed as a further component leading to an aberrant immune reaction.

Successful surgical and medical treatment of a severe, acute epidural bleed in a young dog due to steroid responsive meningitis-arteritis

Background

Steroid responsive meningitis-arteritis (SRMA) is an immune-mediated disease of the leptomeninges and its associated blood vessels, typically responsive to corticosteroids. Clinically relevant haemorrhage is a rare finding in such patients and for this reason surgical decompression of the spinal cord is normally not considered. The diagnosis of SRMA is supported by serum C-reactive protein (CRP) increase, cerebrospinal fluid (CSF) examination, including cytology (polymorphonuclear pleocytosis in the acute form), nucleated cell-, red blood cell- and protein count, as well as by evaluating CSF and serum IgA concentrations. D-dimer concentrations in serum and CSF should be elevated as well and therefore can be also evaluated as a further diagnostic tool.

Case presentation

A 1.5-year-old mixed breed dog was presented with pyrexia, cervical pain and acute tetraparesis. Magnetic resonance imaging revealed an extradural mass lesion at the level of the sixth cervical vertebra, consistent with a subacute epidural haemorrhage, causing severe compression of the spinal cord. Based on the dog’s signalment, clinical history and results of the blood and CSF analyses (incl. D-dimer determination), SRMA with secondary epidural haemorrhage was suspected. Decompressive surgery was performed through a right sided partial dorsal laminectomy. Post-surgical immunosuppressive treatment was started with cytarabine and then continued with prednisolone after completion of wound healing.

Conclusions

This is the first report in which medical and surgical treatment were combined in a patient with SRMA and it highlights the possibility of performing a successful surgical intervention despite the need for immunosuppressive therapy. Moreover, while SRMA diagnosis is normally based on CSF analysis and CSF and serum IgA concentrations, D-dimer concentrations in serum and CSF were also useful in this patient.

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.

Clinical characteristics, breed differences, and quality of life in North American dogs with acute steroid-responsive meningitis-arteritis

Background

Steroid‐responsive meningitis‐arteritis (SRMA) is a common inflammatory neurologic disorder of dogs for which certain breeds are predisposed.

Objectives

To determine whether breed differences exist in clinical features, treatment response, and relapse in a population of North American dogs with SRMA, and to evaluate the effect of disease on dogs' quality of life (QoL).

Animals

Sixty‐one client‐owned dogs with SRMA: 29 dogs identified through an American Kennel Club‐Canine Health Foundation survey and 32 dogs from North Carolina (NC) State Veterinary Hospital.

Methods

Retrospective case series. Caregivers completed an online survey to assess QoL.

Results

Breeds represented most often included the Golden Retriever (n = 12), Bernese Mountain Dog (10), Wirehaired Pointing Griffon (9), Boxer (9), and Beagle (6). No breed differences were identified with respect to clinical severity, diagnostic findings, or outcome. Twenty‐nine dogs (48%) had ≥1 disease relapse. There was a significant effect of cerebrospinal fluid nucleated cell count on the frequency of disease relapse (P = .003), but no relationship was identified between treatment protocol and relapse. Dogs' QoL was associated with the severity of corticosteroid‐related adverse effects (P = .03), which were dose‐related (r = .24, P = .02) and more prevalent in Wirehaired Pointing Griffons than in other breeds (P = .04).

Conclusion and Clinical Importance

Golden Retrievers and Wirehaired Pointing Griffons should be considered among the breeds recognized to develop SRMA. Treatment with higher corticosteroid dosages is correlated with more severe adverse effects and worse QoL, but it may not improve clinical outcome.

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.

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.

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.

Toll-like receptors 4 and 9 are responsible for the maintenance of the inflammatory reaction in canine steroid-responsive meningitis-arteritis, a large animal model for neutrophilic meningitis

BACKGROUND

Steroid-responsive meningitis-arteritis (SRMA) is a systemic inflammatory disease affecting young adult dogs and a potential large animal model for neutrophilic meningitis. Similarities between SRMA and infectious central nervous system (CNS) diseases in lymphocyte subsets suggest an infectious origin.Toll-like receptors (TLRs) are pattern recognition receptors playing an important role in innate immunity. Due to their ability to recognize both self and non-self antigens, we hypothesize that TLRs are among the key factors for the induction of the inflammatory process in SRMA and provide an indirect hint on the etiology of the disease.

METHODS

The expression profile of cell surface TLRs (TLR2, TLR4 and TLR5) and intracellular TLRs (TLR3 and TLR9) of canine leukocytes was analyzed by immunophenotyping and subsequent flow cytometric measurements. Experiments were performed on cerebrospinal fluid (CSF) and peripheral blood (PB) samples of dogs affected with SRMA during the acute phase (n = 14) as well as during treatment (n = 23) and compared with those of dogs with bacterial meningitis (n = 3), meningoencephalitis of unknown etiology (n = 6), neoplasia of the central nervous system (n = 6) and a group of dogs with miscellaneous neurological diseases (n = 9). Two additional control groups consisted of dogs with pyogenic infections (n = 13) and of healthy dogs (n = 6).

RESULTS

All examined groups showed a high percentage of TLR2, TLR4 and TLR5 positive PB polymorphonuclear cells (PMNs) in comparison to healthy dogs. Very high values of TLR9 positive PB PMNs were detected in acute SRMA. Only a few similarities were found between SRMA patients and dogs with pyogenic infections, both groups were characterized by high expression of TLR4 positive PB monocytes. Glucocorticosteroid therapy reduced TLR2, TLR4 and TLR9 expression in PB monocytes.

CONCLUSIONS

A relatively high expression of TLR4 and TLR9 in acute SRMA suggests that these two receptors might be involved in the inflammatory process in SRMA, enhancing the autoimmune reaction. Systematic CSF cell analysis for TLRs can be performed in future treatment studies in larger animals, such as dogs.

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.

Evaluation of brain tissue or cerebrospinal fluid with broadly reactive polymerase chain reaction for Ehrlichia, Anaplasma, spotted fever group Rickettsia, Bartonella, and Borrelia species in canine neurological diseases (109 cases)

BACKGROUND

Vector-transmitted microorganisms in the genera Ehrlichia, Anaplasma, Rickettsia, Bartonella, and Borrelia are commonly suspected in dogs with meningoencephalomyelitis (MEM), but the prevalence of these pathogens in brain tissue and cerebrospinal fluid (CSF) of dogs with MEM is unknown.

HYPOTHESIS/OBJECTIVES

To determine if DNA from these genera is present in brain tissue and CSF of dogs with MEM, including those with meningoencephalitis of unknown etiology (MUE) and histopathologically confirmed cases of granulomatous (GME) and necrotizing meningoencephalomyelitis (NME).

ANIMALS

Hundred and nine dogs examined for neurological signs at 3 university referral hospitals.

METHODS

Brain tissue and CSF were collected prospectively from dogs with neurological disease and evaluated by broadly reactive polymerase chain reaction (PCR) for Ehrlichia, Anaplasma, Spotted Fever Group Rickettsia, Bartonella, and Borrelia species. Medical records were evaluated retrospectively to identify MEM and control cases.

RESULTS

Seventy-five cases of MUE, GME, or NME, including brain tissue from 31 and CSF from 44 cases, were evaluated. Brain tissue from 4 cases and inflammatory CSF from 30 cases with infectious, neoplastic, compressive, vascular, or malformative disease were evaluated as controls. Pathogen nucleic acids were detected in 1 of 109 cases evaluated. Specifically, Bartonella vinsonii subsp. berkhoffii DNA was amplified from 1/6 dogs with histopathologically confirmed GME.

CONCLUSION AND CLINICAL IMPORTANCE

The results of this investigation suggest that microorganisms in the genera Ehrlichia, Anaplasma, Rickettsia, and Borrelia are unlikely to be directly associated with canine MEM in the geographic regions evaluated. The role of Bartonella in the pathogenesis of GME warrants further investigation.

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.