West Nile virus neuroinvasive disease associated with rituximab therapy.

West Nile virus neuroinvasive disease (WNVND) manifests with meningitis, encephalitis, and/or acute flaccid paralysis. It represents less than 1% of the clinical syndromes associated with West Nile virus (WNV) infection in immunocompetent patients. Immunosuppressive therapy is associated with increased risk of WNVND and worse prognosis. We present a patient with WNVND during therapy with rituximab, and a review of the literature for previous similar cases with the goal to describe the clinical spectrum of WNVND in patients treated specifically with rituximab. Our review indicates that the most common initial complaints are fever and altered mental status, brain magnetic resonance imaging often shows bilateral thalamic hyperintensities, and cerebrospinal analysis consistently reveals mild lymphocytic pleocytosis with elevated protein, positive WNV polymerase chain reaction, and negative WNV antibodies. Treatment is usually supportive care, with intravenous immunoglobulins (IVIG) plus corticosteroids and WNV-specific IVIG also used. The disease is usually fatal despite intervention. Our patient's presentation was very similar to prior reports, however demonstrated spontaneous improvement with supportive management only. WNVND is a rare and serious infection with poor prognosis when associated with rituximab therapy. Diagnosis is complicated by absent or delayed development of antibodies. The presence of bilateral thalamic involvement is a diagnostic clue for WNVND. There is insufficient evidence to recommend the use of corticosteroids or IVIG.

Microglia in post-mortem brain tissue of patients with bipolar disorder are not immune activated.

Genetic, epidemiological, and biomarker studies suggest that the immune system is involved in the pathogenesis of bipolar disorder (BD). It has therefore been hypothesized that immune activation of microglia, the resident immune cells of the brain, is associated with the disease. Only a few studies have addressed the involvement of microglia in BD so far and a more detailed immune profiling of microglial activation is lacking. Here, we applied a multi-level approach to determine the activation state of microglia in BD post-mortem brain tissue. We did not find differences in microglial density, and mRNA expression of microglial markers in the medial frontal gyrus (MFG) of patients with BD. Furthermore, we performed in-depth characterization of human primary microglia isolated from fresh brain tissue of the MFG, superior temporal gyrus (STG), and thalamus (THA). Similarly, these ex vivo isolated microglia did not show elevated expression of inflammatory markers. Finally, challenging the isolated microglia with LPS did not result in an increased immune response in patients with BD compared to controls. In conclusion, our study shows that microglia in post-mortem brain tissue of patients with BD are not immune activated.

Clinical characteristics of autoimmune GFAP astrocytopathy.

The clinical features of autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy remain to be elucidated. We describe here the clinical features of 14 patients with GFAP astrocytopathy confirmed by detection of GFAP-IgG in cerebrospinal fluid (CSF). The novel findings of this study are as follows. First, over half of the patients presented with movement disorders (tremor, myoclonus, and ataxia), autonomic dysfunction (mainly urinary dysfunction), and hyponatremia. Second, most patients showed transient elevation of adenosine deaminase activity levels in CSF. Finally, some patients showed bilateral hyperintensities in the posterior part of the thalamus on brain magnetic resonance imaging.

Cerebellar fastigial nuclear glutamatergic neurons regulate immune function via hypothalamic and sympathetic pathways.

We previously have shown that cerebellar fastigial nucleus (FN) modulates immune function, but pathways or mechanisms underlying this immunomodulation require clarification. Herein, an anterograde and retrograde tracing of nerve tracts between the cerebellar FN and hypothalamus/thalamus was performed in rats. After demonstrating a direct cerebellar FN-hypothalamic/thalamic glutamatergic projection, 6-diazo-5-oxo-L-norleucine (DON), an inhibitor of glutaminase that catalyzes glutamate synthesis, was injected bilaterally in the cerebellar FN and simultaneously, D,L-threo-ß-hydroxyaspartic acid (THA), an inhibitor of glutamate transporters on cell membrane, was bilaterally injected in the lateral hypothalamic area (LHA) or the ventrolateral (VL) thalamic nucleus. DON treatment in the FN alone decreased number of glutamatergic neurons that projected axons to the LHA and also diminished glutamate content in both the hypothalamus and the thalamus. These effects of DON were reduced by combined treatment with THA in the LHA or in the VL. Importantly, DON treatment in the FN alone attenuated percentage and cytotoxicity of natural killer (NK) cells and also lowered percentage and cytokine production of T lymphocytes. These DON-caused immune effects were reduced or abolished by combined treatment with THA in the LHA, but not in the VL. Simultaneously, DON treatment elevated level of norepinephrine (NE) in the spleen and mesenteric lymphoid nodes, and THA treatment in the LHA, rather than in the VL, antagonized the DON-caused NE elevation. These findings suggest that glutamatergic neurons in the cerebellar FN regulate innate and adaptive immune functions and the immunomodulation is conveyed by FN-hypothalamic glutamatergic projections and sympathetic nerves that innervate lymphoid tissues.

Temporary upregulation of anti-inflammatory cytokine IL-13 expression in the brains of CD14 deficient mice in the early stage of prion infection.

CD14 deficient (CD14(-/-)) mice survived longer than wild-type (WT) C57BL/6J mice when inoculated with prions intracerebrally, accompanied by increased expression of anti-inflammatory cytokine IL-10 by microglia in the early stage of infection. To assess the immune regulatory effects of CD14 in detail, we compared the gene expression of pro- and anti-inflammatory cytokines in the brains of WT and CD14(-/-) mice infected with the Chandler strain. Gene expression of the anti-inflammatory cytokine IL-13 in prion-infected CD14(-/-) mice was temporarily upregulated at 75dpi, whereas IL-13 gene expression was not upregulated in prion-infected WT mice. Immunofluorescence staining showed that IL-13 was mainly expressed in neurons of the thalamus at 75dpi. These results suggest that CD14 can suppress IL-13 expression in neurons during the early stage of prion infection.

Nociceptive thresholds in rats in response to lipopolysaccharide injection into the specific nuclei of the thalamus of the brain.

Microinjections of LPS into the specific nuclei of rat thalamus (ventrobasal thalamic nuclei VPL and VPM) slightly increased perceptual component and significantly decreased emotional component of systemic nociceptive response.

Aquaporin-4 autoantibody: a neurogenic cause of anorexia and weight loss.

Neuromyelitis optica (NMO) is a severe inflammatory demyelinating disease often associated with a highly specific autoantibody, aquaporin-4 antibody. Although the classic syndrome involves the optic nerves and spinal cord, aquaporin-4 antibody has been important in defining the true spectrum of NMO, which now includes brain lesions in areas of high aquaporin-4 expression. Brainstem involvement, specifically area postrema involvement in the medulla, has been associated with intractable vomiting in some patients with NMO. We describe a 14-year-old female with positive aquaporin-4 antibody whose clinical course was dominated by severe anorexia with associated weight loss (from 68-41kg; body mass index 25.2-15.6). Magnetic resonance imaging showed lesions in the medulla, pons, and thalami. Although she had asymptomatic radiological longitudinally extensive transverse myelitis, she never had symptoms or signs referable to the spinal cord or the optic nerves. We propose that anorexia and weight loss should be considered part of the NMO spectrum, probably related to area postrema involvement.

Neuron-immune interactions in the sensitized thalamus induced by mustard oil application to rat molar pulp.

We have reported that mustard oil application to the rat dental pulp induces neuronal activation in the thalamus. To address the mechanisms involved in the thalamic changes, we performed neuronal responsiveness recording, immunohistochemistry, and molecular biological analysis. After mustard oil application, neuronal responsiveness was increased in the mediodorsal nucleus. When MK801 (an N-methyl-D-aspartate receptor antagonist) was applied to the mediodorsal nucleus, the enhanced responsiveness was decreased. N-methyl-D-aspartate receptor 2D, glial fibrillary acidic protein, and antigen-presenting cell-related gene mRNAs in the contralateral thalamus were up-regulated at 10 minutes after mustard oil application, but were down-regulated within 10 minutes after the antagonist application. OX6-expressing microglia and glial fibrillary acidic protein-expressing astrocytes did not increase until 60 minutes after mustard oil application. These results suggested that the thalamic neurons play some roles in regulating the glial cell activation in the mediodorsal nucleus via N-methyl-D-aspartate receptor 2D during pulp inflammation-induced central sensitization.

Artificial dental pulp exposure injury up-regulates antigen-presenting cell-related molecules in rat central nervous system.

INTRODUCTION: Bacterial infection and resulting inflammation of the dental pulp might not only trigger neuroimmune interactions in this tissue but also sensitize the central nervous system (CNS) such as the thalamus via nociceptive neurons. Thus, immunopathologic changes in the rat thalamus that take place after pulp inflammation were investigated. METHODS: Pulp exposure was made in mandibular right first molars of 5-week-old Wistar rats. After 24 hours, the thalamus was retrieved and subjected to either immunohistochemistry for class II major histocompatibility complex (MHC) molecules and glial fibrillary acidic protein (GFAP) or mRNA expression analysis of antigen-presenting cell-related molecules and N-methyl-D-aspartate receptor 2D subunit (NR2D) by means of reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR. RESULTS: At 24 hours after pulp exposure, the density of class II MHC molecule-expressing and GFAP-expressing cells was increased in the contralateral thalamus. Gene expression analysis revealed the up-regulation of class II MHC molecules, CD80, CD83, CD86, and NR2D in the contralateral thalamus, as compared with the ipsilateral thalamus. CONCLUSIONS: These results suggest the signal of pulp inflammation induces neuronal activation in the CNS.

Anti-brain autoantibodies and altered excitatory neurotransmitters in obsessive-compulsive disorder.

Although serum autoantibodies directed against basal ganglia (BG) implicate autoimmunity in the pathogenesis of obsessive-compulsive disorder (OCD), it is unclear whether these antibodies can cross the blood-brain barrier to bind against BG or other components of the OCD circuit. It is also unclear how they might lead to hyperactivity in the OCD circuit. We examined this by investigating the presence of autoantibodies directed against the BG or thalamus in the serum as well as CSF of 23 OCD patients compared with 23 matched psychiatrically normal controls using western blot. We further investigated CSF amino acid (glutamate, GABA, taurine, and glycine) levels and also examined the extent to which these levels were related to the presence of autoantibodies. There was evidence of significantly more binding of CSF autoantibodies to homogenate of BG as well as to homogenate of thalamus among OCD patients compared with controls. There was no significant difference in binding between patient and control sera except for a trend toward more bands to BG and thalamic protein corresponding to 43 kD among OCD patients compared with controls. CSF glutamate and glycine levels were also significantly higher in OCD patients compared with controls, and further multivariate analysis of variance showed that CSF glycine levels were higher in those OCD patients who had autoantibodies compared with those without. The results of our study implicate autoimmune mechanisms in the pathogenesis of OCD and also provide preliminary evidence that autoantibodies against BG and thalamus may cause OCD by modulating excitatory neurotransmission.

Double step paraneoplastic brainstem encephalitis: a clinicopathological study.

A case of brainstem encephalitis in a man positive for both anti-Hu and anti-Ri antibodies is reported. This case had an unusual double step evolution and progressive involvement of different CNS subdivisions at MRI. Brainstem encephalitis developed abruptly, mimicking a posterior vascular deficit with vertigo and dizziness. These symptoms transiently remitted completely after a few days to relapse acutely 1 month later with sudden loss of consciousness, followed by confusion, disorientation, dysarthria, dysphagia and reduced thermic sensation on the right side. Within another few days, the patient developed acute respiratory failure and died some weeks later. MRI was negative at the beginning but later showed a progressive ascending involvement of the brainstem and thalamus. At autopsy, this picture corresponded to lymphocytic infiltration, preferentially B cells into the perivascular spaces and T cells in the brainstem parenchyma, confirming that T cells could be the effector of cytotoxicity, probably in the presence of cooperation with B cells that were well represented in this setting.

Altered neuronal expression of TASK1 and TASK3 potassium channels in rodent and human autoimmune CNS inflammation.

Multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) are characterized by T cell-mediated autoimmune inflammation of the central nervous system (CNS) leading to oligodendrocyte loss and demyelination accompanied by neuronal cell death. Neuronal TWIK-related acid-sensitive potassium (TASK) channels allow the regulated efflux of potassium ions. These channels might either protect neurons in the inflamed CNS by modulating electrical excitability or even contribute to inflammatory neurodegeneration mediating intracellular potassium depletion. Using a combination of in-situ-hybridisation and immunofluorescence staining, we found increased neuronal expression of TASK1 and TASK3 channels in the optic nerve and decreased expression in the spinal cord and thalamus of rats undergoing MOG-induced EAE. Inflammatory plaques of human MS patients displayed profoundly lowered expression of both TASK isoforms. Thus, regulated expression of TASK channels might contribute to a molecular switch between death and survival of neurons in autoimmune CNS inflammation.

The effects of viscero-somatic interactions on thalamic mast cell recruitment in cystitic rats.

Mast cells accessing the brain parenchyma through the blood-brain barrier in healthy animals are limited to pre-cortical sensory relays - the olfactory bulb and the thalamus. We have demonstrated that unilateral repetitive stimulation of the abdominal wall generates asymmetry in midline thalamic mast cell (TMC) distribution in cyclophosphamide-injected rats, consisting of contralateral side-prevalence with respect to the abdominal wall stimulation. TMC asymmetry 1) was generated in strict relation with cystitis, and was absent in disease-free and mesna-treated animals, 2) was restricted to the anterior portion of the paraventricular pars anterior and reuniens nuclei subregion, i.e., the rostralmost part of the paraventricular thalamic nucleus, the only thalamic area associated with viscero-vagal and somatic inputs, via the nucleus of the solitary tract, and via the medial contingent of the spinothalamic tract, respectively, and 3) originated from somatic tissues, i.e., the abdominal wall where bladder inflammation generates secondary somatic hyperesthesia leading to referred pain in humans. Present data suggest that TMCs may be involved in thalamic sensory processes, including some aspects of visceral pain and abnormal visceral/somatic interactions.

A murine model for neuropsychiatric disorders associated with group A beta-hemolytic streptococcal infection.

A syndrome of motoric and neuropsychiatric symptoms comprising various elements, including chorea, hyperactivity, tics, emotional lability, and obsessive-compulsive symptoms, can occur in association with group A beta-hemolytic streptococcal (GABHS) infection. We tested the hypothesis that an immune response to GABHS can result in behavioral abnormalities. Female SJL/J mice were immunized and boosted with a GABHS homogenate in Freund's adjuvant, whereas controls received Freund's adjuvant alone. When sera from GABHS-immunized mice were tested for immunoreactivity to mouse brain, a subset was found to be immunoreactive to several brain regions, including deep cerebellar nuclei (DCN), globus pallidus, and thalamus. GABHS-immunized mice having serum immunoreactivity to DCN also had increased IgG deposits in DCN and exhibited increased rearing behavior in open-field and hole-board tests compared with controls and with GABHS-immunized mice lacking serum anti-DCN antibodies. Rearing and ambulatory behavior were correlated with IgG deposits in the DCN and with serum immunoreactivity to GABHS proteins in Western blot. In addition, serum from a GABHS mouse reacted with normal mouse cerebellum in nondenaturing Western blots and immunoprecipitated C4 complement protein and alpha-2-macroglobulin. These results are consistent with the hypothesis that immune response to GABHS can result in motoric and behavioral disturbances and suggest that anti-GABHS antibodies cross-reactive with brain components may play a role in their pathophysiology.

Aberrant transcription of unrearranged T-cell receptor beta gene in mouse brain.

The nervous system and the immune system share several functional molecules involved in various cell-cell interaction events. In this study, we used in situ hybridization to identify immune molecules that are expressed by a restricted population of neurons in the mouse brain and found that mRNA for the beta subunit of T-cell receptor (TCRbeta) was predominantly and strongly localized to neurons in deep layers of the cerebral neocortex and weakly expressed in the thalamus. Developmentally, TCRbeta mRNA expression started at embryonic day 15 in the thalamic nuclei and at postnatal day 1 in the cerebral neocortex. The level of TCRbeta mRNA in the neocortex subsequently increased until postnatal day 21, and it remained high in the adult. Detailed analysis revealed that only the Cbeta2 segment of TCRbeta, not the Cbeta1 or Vbeta segments, was expressed by the brain neurons. By the 5' rapid amplification of cDNA ends method, we determined a brain-specific transcription start site in the Jbeta2 region locus, not in the Vbeta region locus. Furthermore, we confirmed that the aberrant transcription around the Jbeta2 region took place only in neurons and lymphocytes in transgenic mice. These results demonstrate that the transcriptional machinery for unrearranged TCRbeta expression is shared by the nervous and immune systems and raise a possibility of gene rearrangement in neurons under certain circumstances.

Expression of T cell receptor beta locus in central nervous system neurons.

MHC class I proteins are cell-surface ligands that bind to T cell receptors and other immunoreceptors and act to regulate the activation state of immune cells. Recent work has shown that MHC class I genes and CD3zeta, an obligate component of T cell receptors, are expressed in neurons, are regulated by neuronal activity, and function in neuronal development and plasticity. A search for additional neuronally expressed T cell receptor components has revealed that the T cell antigen receptor beta (TCRbeta) locus is expressed in neurons of the murine central nervous system and that this expression is dynamically regulated over development. In neonates, expression is most abundant in various thalamic nuclei. At later ages and in adults, thalamic expression fades and cortical expression is robust, particularly in layer 6. In T cells, protein-encoding transcripts are produced only after recombination of the TCRbeta genomic locus, which joins variable, diversity, and joining regions, a process that creates much of the diversity of the immune system. We detect no genomic recombination in neurons. Rather, transcripts begin in regions upstream of several joining regions, and are spliced to constant region segments. One of the transcripts encodes a hypothetical 207-aa, 23-kDa protein, which includes the TCRbeta J2.7 region, and the entire C region. These observations suggest that TCRbeta may function in neurons.

Chronic electrical stimulation of the lateral hypothalamus increases natural killer cell cytotoxicity in rats.

Previously, we found that in rats coagulation of the lateral hypothalamus (LH) caused depression of the peripheral blood natural killer cell cytotoxicity (NKCC) and the number of large granular lymphocytes (LGL). In the present work, we have tested the effects on both spleen and blood NKCC of acute (1 day) and chronic (21 days) electrical stimulation of LH, and LGL number in conscious, freely behaving animals. Five groups of male Wistar rats were used: LH stimulated (n=22), thalamic (Thal) stimulated control (n=4), operated but non-stimulated LH sham controls (n=7), non-operated normal control group (n=8) and spleen baseline group (n=10). Chronic stimulation of LH caused significant augmentation of NKCC (51Cr-release assay) and LGL number (a morphological method), more pronounced in the spleen than in the peripheral blood. Rats responding to LH stimulation with feeding showed a slightly greater effect than those responding with a locomotor reaction. The observed effects were anatomically specific as no influence of Thal stimulation or the sham procedure was found. The results are discussed in terms of the involvement of LH in reward phenomena and the hormonal control of the immune system.

Neuropathological study of the role of mast cells and histamine-positive neurons in selective vulnerability of the thalamus and inferior colliculus in thiamine-deficient encephalopathy.

The purpose of the present study was to examine the role of histamine in the pathogenesis of experimental thiamine-deficient encephalopathy. By studying sagittal serial sections the authors were able to examine the topographical relationship between histamine-positive neurons and fibers, the number of mast cells, and localized lesions in the thalamus (TH) and inferior colliculus (IC). Adult rats were given a thiamine-deficient diet and pyrithiamine was given intraperitoneally (30 microg/100 g bodyweight per day), and the distribution of vulnerable regions and petechial bleeding was histologically examined by reconstruction of the sagittal serial sections. The distribution of mast cells and histamine-positive neurons and fibers was examined immunohistochemically in control rats, and compared between the vulnerable and non-vulnerable regions of the TH and tectum. Changes in the aforementioned measures during the thiamine-deficient state were also examined. The blood-brain barrier was examined using antibodies against rat endothelial barrier antigen (EBA) and albumin. The density of histamine-positive fibers in the vulnerable regions of the TH and IC was very low and not different from the non-vulnerable regions, and the number of mast cells was significantly higher in the lateral portion of the TH than the medial portion of the TH. The numbers of mast cells increased on days 7-10 after the start of the experiment, and significantly decreased on days 14-21. Histamine-positive neurons and fibers in the TH and IC also had the same changes. Bleeding of the IC occurred exclusively around arteries, and perivenous bleeding was absent. Albumin exudation and suppression of EBA expression of capillaries were found in the spongy lesions of the TH and IC. The role of histamine in selective vulnerability of the TH and IC in experimental thiamine-deficient encephalopathy was not supported. Findings in the present study suggest that the spongy change is a primary event, and vascular changes are secondary.

Degranulation of mast cells in the rat thalamus.

Brain mast cells are selectively concentrated in the thalamus of many mammalian species. We here describe by light and electron microscopy in the normal thalamus of adult rats the features of mast cell degranulation, which indicate an active release of the mediators stored in their intracellular granules. The state of activity of thalamic mast cells in basal conditions was found to range from the release of a few granules to a massive degranulation, and the latter process was much less frequent than a partial degranulation. Mast cells were subdivided in three categories (fully granulated, partially or massively degranulated) on the basis of their cytoplasmic features revealed by acidic toluidine blue staining; the fully granulated cells were found to represent only 23 % of thalamic mast cells. This strategy of evaluation could be of help in the comparison of the functional correlates of mast cells in different conditions and experimental paradigms. However, we also demonstrated with image analysis a continuum of the variation of staining intensity of granulated and degranulating mast cells, without a sharp subdivision into different categories. Therefore our results reveal that the vast majority of mast cells are active in the thalamus in basal conditions, and that image analysis can provide an objective index of the activity of these cells.