Hemophagocytic Lymphohistiocytosis Gene Mutations in Adult Patients Presenting With CLIPPERS-Like Syndrome.

OBJECTIVE: To determine whether adult cases of Chronic Lymphocytic Inflammation with Pontine Perivascular Enhancement Responsive to Steroids (CLIPPERS) may be related to familial hemophagocytic lymphohistiocytosis (HLH) causes, we have screened patients with adult-onset CLIPPERS for mutations in primary HLH-associated genes. METHODS: In our cohort of 36 patients fulfilling the criteria for probable or definite CLIPPERS according to the CLIPPERS-2017 criteria, we conducted a first study on 12 patients who consented to genetic testing. In these 12 patients, systemic HLH criteria were searched, and genetic analysis of 8 genes involved in primary HLH was performed. RESULTS: Four definite and 8 probable CLIPPERS were enrolled (n = 12). Mutations involved in HLH were identified in 2 definite and 2 probable CLIPPERS (4/12). Three of them had biallelic PRF1 mutations with reduced perforin expression in natural killer cells. The remaining patient had biallelic UNC13D mutations with cytotoxic lymphocyte impaired degranulation. None of the mutated patients reached the criteria for systemic HLH. During follow-up, 3 of them displayed atypical findings for CLIPPERS, including emergence of systemic non-Hodgkin lymphoma (1/3) and confluent gadolinium-enhancing lesions on brain MRI (3/3). CONCLUSIONS: In our patients presenting with adult-onset CLIPPERS, one-third have HLH gene mutations. This genetic treatable condition should be searched in patients with CLIPPERS, especially in those presenting with atypical findings.

A murine model of Lyme disease demonstrates that Borrelia burgdorferi colonizes the dura mater and induces inflammation in the central nervous system.

Lyme disease, which is caused by infection with Borrelia burgdorferi and related species, can lead to inflammatory pathologies affecting the joints, heart, and nervous systems including the central nervous system (CNS). Inbred laboratory mice have been used to define the kinetics of B. burgdorferi infection and host immune responses in joints and heart, however similar studies are lacking in the CNS of these animals. A tractable animal model for investigating host-Borrelia interactions in the CNS is key to understanding the mechanisms of CNS pathogenesis. Therefore, we characterized the kinetics of B. burgdorferi colonization and associated immune responses in the CNS of mice during early and subacute infection. Using fluorescence-immunohistochemistry, intravital microscopy, bacterial culture, and quantitative PCR, we found B. burgdorferi routinely colonized the dura mater of C3H mice, with peak spirochete burden at day 7 post-infection. Dura mater colonization was observed for several Lyme disease agents including B. burgdorferi, B. garinii, and B. mayonii. RNA-sequencing and quantitative RT-PCR showed that B. burgdorferi infection was associated with increased expression of inflammatory cytokines and a robust interferon (IFN) response in the dura mater. Histopathologic changes including leukocytic infiltrates and vascular changes were also observed in the meninges of infected animals. In contrast to the meninges, we did not detect B. burgdorferi, infiltrating leukocytes, or large-scale changes in cytokine profiles in the cerebral cortex or hippocampus during infection; however, both brain regions demonstrated similar changes in expression of IFN-stimulated genes as observed in peripheral tissues and meninges. Taken together, B. burgdorferi is capable of colonizing the meninges in laboratory mice, and induces localized inflammation similar to peripheral tissues. A sterile IFN response in the absence of B. burgdorferi or inflammatory cytokines is unique to the brain parenchyma, and provides insight into the potential mechanisms of CNS pathology associated with this important pathogen.

Encephalomyelitis Caused by Balamuthia mandrillaris in a Woman With Breast Cancer: A Case Report and Review of the Literature.

Balamuthia mandrillaris is one cause of a rare and severe brain infection called granulomatous amoebic encephalitis (GAE), which has a mortality rate of >90%. Diagnosis of Balamuthia GAE is difficult because symptoms are non-specific. Here, we report a case of Balamuthia amoebic encephalomyelitis (encephalitis and myelitis) in a woman with breast cancer. She sustained trauma near a garbage dump 2 years ago and subsequently developed a skin lesion with a Mycobacterium abscessus infection. She experienced dizziness, lethargy, nausea and vomiting, inability to walk, and deterioration of consciousness. Next-generation sequencing of cerebrospinal fluid (CSF) samples revealed B. mandrillaris, and MRI of both brain and spinal cord showed abnormal signals. T-cell receptor (TCR) sequencing of the CSF identified the Top1 TCR. A combination of amphotericin B, flucytosine, fluconazole, sulfamethoxazole, trimethoprim, clarithromycin, pentamidine, and miltefosine was administrated, but she deteriorated gradually and died on day 27 post-admission.

Archeological neuroimmunology: resurrection of a pathogenic immune response from a historical case sheds light on human autoimmune encephalomyelitis and multiple sclerosis.

Aim of our study was to identify the target auto-antigen in the central nervous system recognized by the immune system of a unique patient, who died more than 60 years ago from a disease with pathological changes closely resembling multiple sclerosis (MS), following a misguided immunization with lyophilized calf brain tissue. Total mRNA was isolated from formaldehyde fixed and paraffin embedded archival brain tissue containing chronic active inflammatory demyelinating lesions with inflammatory infiltrates rich in B-lymphocytes and plasma cells. Analysis of the transcriptome by next generation sequencing and reconstruction of the dominant antibody by bioinformatic tools revealed the presence of one strongly expanded B-cell clone, producing an autoantibody against a conformational epitope of myelin oligodendrocytes glycoprotein (MOG), similar to that recognized by the well characterized monoclonal anti-MOG antibody 8-18C5. The reconstructed antibody induced demyelination after systemic or intrathecal injection into animals with T-cell mediated encephalomyelitis. Our study suggests that immunization with bovine brain tissue in humans may-in a small subset of patients-induce a disease with an intermediate clinical and pathological presentation between MS and MOG-antibody associated inflammatory demyelinating disease (MOGAD).

Single-Cell RNA Sequencing Reveals the Diversity of the Immunological Landscape following Central Nervous System Infection by a Murine Coronavirus.

Intracranial (i.c.) infection of susceptible C57BL/6 mice with the neurotropic JHM strain of mouse hepatitis virus (JHMV) (a member of the Coronaviridae family) results in acute encephalomyelitis and viral persistence associated with an immune-mediated demyelinating disease. The present study was undertaken to better understand the molecular pathways evoked during innate and adaptive immune responses as well as the chronic demyelinating stage of disease in response to JHMV infection of the central nervous system (CNS). Using single-cell RNA sequencing analysis (scRNAseq) on flow-sorted CD45-positive (CD45+) cells enriched from brains and spinal cords of experimental mice, we demonstrate the heterogeneity of the immune response as determined by the presence of unique molecular signatures and pathways involved in effective antiviral host defense. Furthermore, we identify potential genes involved in contributing to demyelination as well as remyelination being expressed by both microglia and macrophages. Collectively, these findings emphasize the diversity of the immune responses and molecular networks at defined stages following viral infection of the CNS.IMPORTANCE Understanding the immunological mechanisms contributing to both host defense and disease following viral infection of the CNS is of critical importance given the increasing number of viruses that are capable of infecting and replicating within the nervous system. With this in mind, the present study was undertaken to evaluate the molecular signatures of immune cells within the CNS at defined times following infection with a neuroadapted murine coronavirus using scRNAseq. This approach has revealed that the immunological landscape is diverse, with numerous immune cell subsets expressing distinct mRNA expression profiles that are, in part, dictated by the stage of infection. In addition, these findings reveal new insight into cellular pathways contributing to control of viral replication as well as to neurologic disease.

Fatal Enteroviral Encephalitis in a Patient with Common Variable Immunodeficiency Harbouring a Novel Mutation in NFKB2.

Common variable immunodeficiency is the most prevalent of the primary immunodeficiency diseases, yet its pathogenesis is largely poorly understood. Of the cases that are monogenic, many arise due to pathogenic variants in NFKB1 and NFKB2. Here, we report enteroviral encephalomyelitis as the cause of a fatal neurodegenerative condition in a patient with a novel heterozygous mutation in NFKB2 (c.2543insG, p.P850Sfs36*) that disrupts non-canonical NF-κB signaling. Investigations of primary and secondary lymphoid tissue demonstrated a complete absence of B cells and germinal centers. Despite multiple negative viral PCR testing of cerebrospinal fluid during her disease progression, post-mortem analysis of cerebral tissue revealed a chronic lymphocytic meningoencephalitis, in the presence of Cocksackie A16 virus, as the cause of death. The clinical features, and progression of disease reported here, demonstrate divergent clinical and immunological phenotypes of individuals within a single family. This is the first reported case of fatal enteroviral encephalomyelitis in a patient with NF-κB2 deficiency and mandates a low threshold for early brain biopsy and the administration of increased immunoglobulin replacement in any patient with a defect in this pathway and deterioration of neurological status.

Antibody neutralization of microbiota-derived circulating peptidoglycan dampens inflammation and ameliorates autoimmunity.

The human microbiota provides tonic signals that calibrate the host immune response1,2, but their identity is unknown. Bacterial peptidoglycan (PGN) subunits are likely candidates since they are well-known immunity-enhancing adjuvants, released by most bacteria during growth, and have been found in the blood of healthy people3-7. We developed a monoclonal antibody (mAb), 2E7, that targets muramyl-L-alanyl-D-isoglutamine (MDP), a conserved and minimal immunostimulatory structure of PGN. Using 2E7-based assays, we detected PGN ubiquitously in human blood at a broad range of concentrations that is relatively stable in each individual. We also detected PGN in the serum of several warm-blooded animals. However, PGN is barely detectable in the serum of germ-free mice, indicating that its origin is the host microbiota. Neutralization of circulating PGN via intraperitoneal administration of 2E7 suppressed the development of autoimmune arthritis and experimental autoimmune encephalomyelitis in mice. Arthritic NOD2-/- mice lacking the MDP sensor did not respond to 2E7, indicating that 2E7 dampens inflammation by blocking nucleotide-binding oligomerization domain-containing protein 2 (NOD2)-mediated pathways. We propose that circulating PGN acts as a natural immune potentiator that tunes the host immune response; altering its level is a promising therapeutic strategy for immune-mediated diseases.

DGAT1 inhibits retinol-dependent regulatory T cell formation and mediates autoimmune encephalomyelitis.

The balance of effector versus regulatory T cells (Tregs) controls inflammation in numerous settings, including multiple sclerosis (MS). Here we show that memory phenotype CD4+ T cells infiltrating the central nervous system during experimental autoimmune encephalomyelitis (EAE), a widely studied animal model of MS, expressed high levels of mRNA for Dgat1 encoding diacylglycerol-O-acyltransferase-1 (DGAT1), an enzyme that catalyzes triglyceride synthesis and retinyl ester formation. DGAT1 inhibition or deficiency attenuated EAE, with associated enhanced Treg frequency; and encephalitogenic, DGAT1-/- in vitro-polarized Th17 cells were poor inducers of EAE in adoptive recipients. DGAT1 acyltransferase activity sequesters retinol in ester form, preventing synthesis of retinoic acid, a cofactor for Treg generation. In cultures with T cell-depleted lymphoid tissues, retinol enhanced Treg induction from DGAT1-/- but not from WT T cells. The WT Treg induction defect was reversed by DGAT1 inhibition. These results demonstrate that DGAT1 suppresses retinol-dependent Treg formation and suggest its potential as a therapeutic target for autoimmune inflammation.

Interleukin-10 Modulation of Virus Clearance and Disease in Mice with Alphaviral Encephalomyelitis.

Alphaviruses are an important cause of mosquito-borne outbreaks of arthritis, rash, and encephalomyelitis. Previous studies in mice with a virulent strain (neuroadapted SINV [NSV]) of the alphavirus Sindbis virus (SINV) identified a role for Th17 cells and regulation by interleukin-10 (IL-10) in the pathogenesis of fatal encephalomyelitis (K. A. Kulcsar, V. K. Baxter, I. P. Greene, and D. E. Griffin, Proc Natl Acad Sci U S A 111:16053-16058, 2014, https://doi.org/10.1073/pnas.1418966111). To determine the role of virus virulence in generation of immune responses, we analyzed the modulatory effects of IL-10 on disease severity, virus clearance, and the CD4+ T cell response to infection with a recombinant strain of SINV of intermediate virulence (TE12). The absence of IL-10 during TE12 infection led to longer morbidity, more weight loss, higher mortality, and slower viral clearance than in wild-type mice. More severe disease and impaired virus clearance in IL-10-/- mice were associated with more Th1 cells, fewer Th2 cells, innate lymphoid type 2 cells, regulatory cells, and B cells, and delayed production of antiviral antibody in the central nervous system (CNS) without an effect on Th17 cells. Therefore, IL-10 deficiency led to more severe disease in TE12-infected mice by increasing Th1 cells and by hampering development of the local B cell responses necessary for rapid production of antiviral antibody and virus clearance from the CNS. In addition, the shift from Th17 to Th1 responses with decreased virus virulence indicates that the effects of IL-10 deficiency on immunopathologic responses in the CNS during alphavirus infection are influenced by virus strain.IMPORTANCE Alphaviruses cause mosquito-borne outbreaks of encephalomyelitis, but determinants of outcome are incompletely understood. We analyzed the effects of the anti-inflammatory cytokine IL-10 on disease severity and virus clearance after infection with an alphavirus strain of intermediate virulence. The absence of IL-10 led to longer illness, more weight loss, more death, and slower viral clearance than in mice that produced IL-10. IL-10 influenced development of disease-causing T cells and entry into the brain of B cells producing antiviral antibody. The Th1 pathogenic cell subtype that developed in IL-10-deficient mice infected with a less virulent virus was distinct from the Th17 subtype that developed in response to a more virulent virus, indicating a role for virus strain in determining the immune response. Slow production of antibody in the nervous system led to delayed virus clearance. Therefore, both the virus strain and the host response to infection are important determinants of outcome.

Expression of microRNAs miR-21 and miR-181c in cerebrospinal fluid and serum in canine meningoencephalomyelitis of unknown origin.

The potential of microRNAs (miRNAs) as biomarkers for canine meningoencephalomyelitis of unknown origin (MUO) was investigated by using quantitative real-time (qRT)-PCR to determine the expression of microRNA-21 (miR-21) and microRNA-181c (miR-181c) in the cerebrospinal fluid (CSF) of dogs. Dogs with MUO (n = 10) had higher levels of expression of miR-21 and miR-181c in the CSF than dogs with non-inflammatory neurological diseases (n = 8). There was a positive correlation between CSF cellularity and expression of miRNAs in the CSF, particularly for miR-21 in the MUO group.

Japanese Macaque Rhadinovirus Encodes a Viral MicroRNA Mimic of the miR-17 Family.

UNLABELLED: Japanese macaque (JM) rhadinovirus (JMRV) is a novel, gamma-2 herpesvirus that was recently isolated from JM with inflammatory demyelinating encephalomyelitis (JME). JME is a spontaneous and chronic disease with clinical characteristics and immunohistopathology comparable to those of multiple sclerosis in humans. Little is known about the molecular biology of JMRV. Here, we sought to identify and characterize the small RNAs expressed during lytic JMRV infection using deep sequencing. Fifteen novel viral microRNAs (miRNAs) were identified in JMRV-infected fibroblasts, all of which were readily detectable by 24 h postinfection and accumulated to high levels by 72 h. Sequence comparisons to human Kaposi's sarcoma-associated herpesvirus (KSHV) miRNAs revealed several viral miRNA homologs. To functionally characterize JMRV miRNAs, we screened for their effects on nuclear factor kappa B (NF-κB) signaling in the presence of two proinflammatory cytokines, tumor necrosis factor alpha (TNF-α) and interleukin-1ß (IL-1ß). Multiple JMRV miRNAs suppressed cytokine-induced NF-κB activation. One of these miRNAs, miR-J8, has seed sequence homology to members of the cellular miR-17/20/106 and miR-373 families, which are key players in cell cycle regulation as well as inflammation. Using reporters, we show that miR-J8 can target 3' untranslated regions (UTRs) with miR-17-5p or miR-20a cognate sites. Our studies implicate JMRV miRNAs in the suppression of innate antiviral immune responses, which is an emerging feature of many viral miRNAs. IMPORTANCE: Gammaherpesviruses are associated with multiple diseases linked to immunosuppression and inflammation, including AIDS-related cancers and autoimmune diseases. JMRV is a recently identified herpesvirus that has been linked to JME, an inflammatory demyelinating disease in Japanese macaques that mimics multiple sclerosis. There are few large-animal models for gammaherpesvirus-associated pathogenesis. Here, we provide the first experimental evidence of JMRV miRNAs in vitro and demonstrate that one of these viral miRNAs can mimic the activity of the cellular miR-17/20/106 family. Our work provides unique insight into the roles of viral miRNAs during rhadinovirus infection and provides an important step toward understanding viral miRNA function in a nonhuman primate model system.

T cell-derived interleukin-10 is an important regulator of the Th17 response during lethal alphavirus encephalomyelitis.

Neuroadapted Sindbis virus infection of mice causes T cell-mediated fatal encephalomyelitis. In the absence of IL-10, pathogenic Th17 cells are increased and disease is accelerated. Lymphoid and myeloid cell contributions to IL-10 production were determined using VertX IL-10 transcriptional eGFP reporter mice. Effector and regulatory CD4(+) and CD8(+) T cells in the brain, but not the cervical lymph nodes, were the primary producers of IL-10. Th17 and Th1/Th17 cells were increased in mice that lacked T cell IL-10 production, although less than in the absence of IL-10. Morbidity and mortality were not affected suggesting an IL-10 threshold for disease exacerbation.

Confirmation of a non-synonymous SNP in PNPLA8 as a candidate causal mutation for Weaver syndrome in Brown Swiss cattle.

BACKGROUND: Bovine progressive degenerative myeloencephalopathy (Weaver syndrome) is a neurodegenerative disorder in Brown Swiss cattle that is characterized by progressive hind leg weakness and ataxia, while sensorium and spinal reflexes remain unaffected. Although the causal mutation has not been identified yet, an indirect genetic test based on six microsatellite markers and consequent exclusion of Weaver carriers from breeding have led to the complete absence of new cases for over two decades. Evaluation of disease status by imputation of 41 diagnostic single nucleotide polymorphisms (SNPs) and a common haplotype published in 2013 identified several suspected carriers in the current breeding population, which suggests a higher frequency of the Weaver allele than anticipated. In order to prevent the reemergence of the disease, this study aimed at mapping the gene that underlies Weaver syndrome and thus at providing the basis for direct genetic testing and monitoring of today's Braunvieh/Brown Swiss herds. RESULTS: Combined linkage/linkage disequilibrium mapping on Bos taurus chromosome (BTA) 4 based on Illumina Bovine SNP50 genotypes of 43 Weaver-affected, 31 Weaver carrier and 86 Weaver-free animals resulted in a maximum likelihood ratio test statistic value at position 49,812,384 bp. The confidence interval (0.853 Mb) determined by the 2-LOD drop-off method was contained within a 1.72-Mb segment of extended homozygosity. Exploitation of whole-genome sequence data from two official Weaver carriers and 1145 other bulls that were sequenced in Run4 of the 1000 bull genomes project showed that only a non-synonymous SNP (rs800397662) within the PNPLA8 gene at position 49,878,773 bp was concordant with the Weaver carrier status. Targeted SNP genotyping confirmed this SNP as a candidate causal mutation for Weaver syndrome. Genotyping for the candidate causal mutation in a random sample of 2334 current Braunvieh animals suggested a frequency of the Weaver allele of 0.26 %. CONCLUSIONS: Through combined use of exhaustive sequencing data and SNP genotyping results, we were able to provide evidence that supports the non-synonymous mutation at position 49,878,773 bp as the most likely causal mutation for Weaver syndrome. Further studies are needed to uncover the exact mechanisms that underlie this syndrome.

Increased concentration of interferon lambda-3, interferon beta and interleukin-10 in the cerebrospinal fluid of patients with tick-borne encephalitis.

Tick-borne encephalitis (TBE) has a wide clinical spectrum, from asymptomatic to severe encephalitis, and host-dependent factors determining the outcome remain elusive. We have measured concentrations of pro-inflammatory/Th1 interferon-γ (IFNγ), immunomodulatory/Th2 interleukin-10 (IL-10), anti-viral type I (IFNß) and type III (IFNλ3) interferons in cerebrospinal fluid (csf) and serum of 18 TBE patients, simultaneously genotyped for polymorphisms associated with the expression of genes IFNL3 (coding IFNλ3), IL10, CD209 and CCR5. IL-10, IFNß and IFNλ3 were up-regulated in csf, with IFNλ3 level higher in patients with the milder clinical presentation (meningitis) than in meningoencephalitis. There was an increased serum IFNß and a tendency for increased serum IL-10 in meningitis patients. Genotype in rs12979860 locus upstream of IFNL3 was associated with IFNλ3 expression and in rs287886 (CD209) - IL-10 expression. IL-10, IFNß and IFNλ3 are expressed and play a protective role in TBE and their expression in TBE patients is associated with genetic polymorphisms.

Interleukin 10 modulation of pathogenic Th17 cells during fatal alphavirus encephalomyelitis.

Mosquito-borne alphaviruses are important causes of epidemic encephalomyelitis. Neuronal cell death during fatal alphavirus encephalomyelitis is immune-mediated; however, the types of cells involved and their regulation have not been determined. We show that the virus-induced inflammatory response was accompanied by production of the regulatory cytokine IL-10, and in the absence of IL-10, paralytic disease occurred earlier and mice died faster. To determine the reason for accelerated disease in the absence of IL-10, immune responses in the CNS of IL-10(-/-) and wild-type (WT) mice were compared. There were no differences in the amounts of brain inflammation or peak virus replication; however, IL-10(-/-) animals had accelerated and increased infiltration of CD4(+)IL-17A(+) and CD4(+)IL-17A(+)IFNγ(+) cells compared with WT animals. Th17 cells infiltrating the brain demonstrated a pathogenic phenotype with the expression of the transcription factor, Tbet, and the production of granzyme B, IL-22, and GM-CSF, with greater production of GM-CSF in IL-10(-/-) mice. Therefore, in fatal alphavirus encephalomyelitis, pathogenic Th17 cells enter the CNS at the onset of neurologic disease and, in the absence of IL-10, appear earlier, develop into Th1/Th17 cells more often, and have greater production of GM-CSF. This study demonstrates a role for pathogenic Th17 cells in fatal viral encephalitis.

Mice deficient in interferon-gamma or interferon-gamma receptor 1 have distinct inflammatory responses to acute viral encephalomyelitis.

Interferon (IFN)-gamma is an important component of the immune response to viral infections that can have a role both in controlling virus replication and inducing inflammatory damage. To determine the role of IFN-gamma in fatal alphavirus encephalitis, we have compared the responses of wild type C57BL/6 (WTB6) mice with mice deficient in either IFN-gamma (GKO) or the alpha-chain of the IFN-gamma receptor (GRKO) after intranasal infection with a neuroadapted strain of sindbis virus. Mortalities of GKO and GRKO mice were similar to WTB6 mice. Both GKO and GRKO mice had delayed virus clearance from the brain and spinal cord, more infiltrating perforin(+) cells and lower levels of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 mRNAs than WTB6 mice. However, inflammation was more intense in GRKO mice than WTB6 or GKO mice with more infiltrating CD3(+) T cells, greater expression of major histocompatibility complex-II and higher levels of interleukin-17A mRNA. Fibroblasts from GRKO embryos did not develop an antiviral response after treatment with IFN-gamma, but showed increases in TNF-alpha, IL-6, CXCL9 and CXCL10 mRNAs although these increases developed more slowly and were less intense than those of WTB6 fibroblasts. These data indicate that both GKO and GRKO mice fail to develop an IFN-gamma-mediated antiviral response, but differ in regulation of the inflammatory response to infection. Therefore, GKO and GRKO cannot be considered equivalent when assessing the role of IFN-gamma in CNS viral infections.

Evaluation of metaphylactic RNA interference to prevent equine herpesvirus type 1 infection in experimental herpesvirus myeloencephalopathy in horses.

OBJECTIVE: To evaluate metaphylactic RNA interference to prevent equine herpesvirus type 1 (EHV-1) infection in experimental herpesvirus myeloencephalopathy in horses and to determine whether horses infected with a neuropathogenic strain of the virus that develop equine herpesvirus myeloencephalopathy (EHM) have differences in viremia. ANIMALS: 13 seronegative horses. PROCEDURES: EHV-1 strain Ab4 was administered intranasally on day 0, and small interfering RNAs (siRNAs [EHV-1 specific siRNAs {n = 7} or an irrelevant siRNA {6}]) were administered intranasally 24 hours before and 12, 24, 36, and 48 hours after infection. Physical and neurologic examinations, nasal swab specimens, and blood samples were collected for virus isolation and quantitative PCR assay. Data from the study were combined with data from a previous study of 14 horses. RESULTS: No significant difference was detected in clinical variables, viremia, or detection of EHV-1 in nasal swab specimens of horses treated with the EHV-1 targeted siRNAs (sigB3-siOri2) versus controls. No significant differences in viremia were detected between horses that developed EHM and those that did not. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of siRNAs targeted against EHV-1 around the time of EHV-1 infection was not protective with this experimental design. Horses infected with the neuropathogenic EHV-1 strain Ab4 that developed EHM did not have a more pronounced viremia.

Oligodendroglia are limited in type I interferon induction and responsiveness in vivo.

Type I interferons (IFNα/ß) provide a primary defense against infection. Nevertheless, the dynamics of IFNα/ß induction and responsiveness by central nervous system (CNS) resident cells in vivo in response to viral infections are poorly understood. Mice were infected with a neurotropic coronavirus with tropism for oligodendroglia and microglia to probe innate antiviral responses during acute encephalomyelitis. Expression of genes associated with the IFNα/ß pathways was monitored in microglia and oligodendroglia purified from naïve and infected mice by fluorescent activated cell sorting. Compared with microglia, oligodendroglia were characterized by low basal expression of mRNA encoding viral RNA sensing pattern recognition receptors (PRRs), IFNα/ß receptor chains, interferon sensitive genes (ISG), as well as kinases and transcription factors critical in IFNα/ß signaling. Although PRRs and ISGs were upregulated by infection in both cell types, the repertoire and absolute mRNA levels were more limited in oligodendroglia. Furthermore, although oligodendroglia harbored higher levels of viral RNA compared with microglia, Ifnα/ß was only induced in microglia. Stimulation with the double stranded RNA analogue poly I:C also failed to induce Ifnα/ß in oligodendroglia, and resulted in reduced and delayed induction of ISGs compared with microglia. The limited antiviral response by oligodendroglia was associated with a high threshold for upregulation of Ikkε and Irf7 transcripts, both central to amplifying IFNα/ß responses. Overall, these data reveal that oligodendroglia from the adult CNS are poor sensors of viral infection and suggest they require exogenous IFNα/ß to establish an antiviral state.

Cutting edge: neuronal recognition by CD8 T cells elicits central diabetes insipidus.

An increasing number of neurologic diseases is associated with autoimmunity. The immune effectors contributing to the pathogenesis of such diseases are often unclear. To explore whether self-reactive CD8 T cells could attack CNS neurons in vivo, we generated a mouse model in which the influenza virus hemagglutinin (HA) is expressed specifically in CNS neurons. Transfer of cytotoxic anti-HA CD8 T cells induced an acute but reversible encephalomyelitis in HA-expressing recipient mice. Unexpectedly, diabetes insipidus developed in surviving animals. This robust phenotype was associated with preferential accumulation of cytotoxic CD8 T cells in the hypothalamus, upregulation of MHC class I molecules, and destruction of vasopressin-expressing neurons. IFN-γ production by the pathogenic CD8 T cells was necessary for MHC class I upregulation by hypothalamic neurons and their destruction. This novel mouse model, in combination with related human data, supports the concept that autoreactive CD8 T cells can trigger central diabetes insipidus.

Genetic and pathogenic characterization of Akabane viruses isolated from cattle with encephalomyelitis in Korea.

A large-scale outbreak of Akabane viral encephalomyelitis in cattle was reported in the southern part of Korea in 2010. Fifteen Akabane virus (AKAV) strains were isolated from the brain and spinal cord samples by using BHK-21 and/or HmLu-1 cells. To examine the genetic relationships and characteristics of the isolates, nucleotide sequences of the S, M, and L segments of the 15 isolates were determined and analyzed. Complete sequence analysis of the 15 AKAV isolates showed 99.9-100% amino acid identities, indicating that the 15 isolates originated from a single strain. The S and M RNA segments of a representative isolate (AKAV-7/SKR/2010) were also compared with the segments of representative reference sequences. This AKAV-7/SKR/2010 strain showed the highest identity with the Iriki and KM-1/Br/06 strains. Neighbor-joining phylogenetic trees of S and M RNA segments were constructed. Four representative AKAV isolates were classified into subgroup Ia, which contains the Iriki and KM-1/Br/06 strains recognized to cause encephalomyelitis in calves and adult cattle in Japan. Moreover, experimental intraperitoneal infection was performed using the AKAV-7/SKR/2010 and AKAV-17/SKR/2010 strains to assess pathogenesis in suckling mice. The 2 isolates, genetically related to the Iriki strain, were neurovirulent and caused neurological signs in suckling mice. In contrast, the 93FMX strain and the K0505 strain, related to the OBE-1 strain, were avirulent in mice. The present results indicate that these isolates most likely had originated from the Iriki strain and are closely related to the Iriki strain both genetically and pathogenically.