Interleukin-6 production by brain tissue and cultured astrocytes infected with Theiler's murine encephalomyelitis virus

Complement Components Are Expressed by Infiltrating Macrophages/Activated Microglia Early Following Viral Infection

The individual innate immune components, interleukin-6 and complement component C3, play a role in the development of acute seizures in the Theiler's murine encephalomyelitis virus-induced seizure model. We examined the mRNA expression of various other complement components, cytokines, chemokines, and major histocompatibility complex antigens both within brain and in isolated ramified microglial and infiltrating macrophage/activated microglial cell populations over a time course covering the first 3 days postinfection. We found that complement component C3 showed the greatest increase in expression in brain of all of the complement components assayed and its level of expression was higher in infiltrating macrophages/activated microglia than in ramified microglial cells.

Social disruption induced priming of CNS inflammatory response to Theiler's virus is dependent upon stress induced IL-6 release

Chronic social disruption stress (SDR) exacerbates acute and chronic phase Theiler's murine encephalomyelitis virus (TMEV) infection, a mouse model of multiple sclerosis. However, the precise mechanism by which this occurs remains unknown. The present study suggests that SDR exacerbates TMEV disease course by priming virus-induced neuroinflammation. It was demonstrated that IL-1β mRNA expression increases following acute SDR; however, IL-6 mRNA expression, but not IL-1β, is upregulated in response to chronic SDR. Furthermore, this study demonstrated SDR prior to infection increases infection related central IL-6 and IL-1β mRNA expression, and administration of IL-6 neutralizing antibody during SDR reverses this increase in neuroinflammation.

Interleukin-6, produced by resident cells of the central nervous system and infiltrating cells, contributes to the development of seizures following viral infection

Cells that can participate in an innate immune response within the central nervous system (CNS) include infiltrating cells (polymorphonuclear leukocytes [PMNs], macrophages, and natural killer [NK] cells) and resident cells (microglia and sometimes astrocytes). The proinflammatory cytokine interleukin-6 (IL-6) is produced by all of these cells and has been implicated in the development of behavioral seizures in the Theiler's murine encephalomyelitis virus (TMEV)-induced seizure model. The assessment, via PCR arrays, of the mRNA expression levels of a large number of chemokines (ligands and receptors) in TMEV-infected and mock-infected C57BL/6 mice both with and without seizures did not clearly demonstrate the involvement of PMNs, monocytes/macrophages, or NK cells in the development of seizures, possibly due to overlapping function of the chemokines. Additionally, C57BL/6 mice unable to recruit or depleted of infiltrating PMNs and NK cells had seizure rates comparable to those of controls following TMEV infection, and therefore PMNs and NK cells do not significantly contribute to seizure development. In contrast, C57BL/6 mice treated with minocycline, which affects monocytes/macrophages, microglial cells, and PMNs, had significantly fewer seizures than controls following TMEV infection, indicating monocytes/macrophages and resident microglial cells are important in seizure development. Irradiated bone marrow chimeric mice that were either IL-6-deficient mice reconstituted with wild-type bone marrow cells or wild-type mice reconstituted with IL-6-deficient bone marrow cells developed significantly fewer behavioral seizures following TMEV infection. Therefore, both resident CNS cells and infiltrating cells are necessary for seizure development.

Up-regulation of the vascular cell adhesion molecule-1 (VCAM-1) induced by Theiler's murine encephalomyelitis virus infection of murine brain astrocytes

The present article reports the up-regulation of the expression of the vascular cell adhesion molecule-1 (VCAM-1) by SJL/J mouse brain astrocytes infected with Theiler's murine encephalomyelitis virus (TMEV). Complementary RNA (cRNA) from mock- and TMEV-infected cells was hybridized to the Affymetrix whole murine genome U74v2 DNA microarray. Hybridization data analysis revealed background expression in untreated cells and the up-regulation of three sequences coding for VCAM-1, as described by the SCOP (Structural Classification Of Proteins) database. The authors further studied its regulation, confirming and validating their mRNA increase by reverse transcriptase-polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR. The presence of the 100-kDa VCAM-1 protein in mock- and TMEV-infected cells was demonstrated in the cell membrane by a specific cell-based enzyme-linked immunosorbent assay (ELISA), in addition to flow cytometry and confocal immunohistochemistry. Further, Western blots were used to quantify the amount of VCAM-1 molecules in cell extracts. All these data demonstrated a mean 75% increase in the expression of VCAM-1 on the surface of TMEV-infected cells. Three inflammatory cytokines, interleukin-1alpha (IL-1alpha), interferon gamma (IFNgumma), and specially tumor necrosis factor alpha (TNF-α), some of which are also induced by TMEV in astrocytes (IL-1alpha and TNF-alpha), were potent inducers of VCAM-1 expression. To demonstrate whether the VCAM-1 molecules were biologically active, mediating adhesion to other cells as the integrin alpha4-expressing CD4+ T lymphocytes, the authors used a cell adhesion test. It was also demonstrated by immunohistochemistry that in vivo VCAM-1 expression is enhanced after TMEV intracraneal infection. The present data show a small but statistically significant overexpression of VCAM-1 after astrocyte infection with TMEV that could play a significant role in vivo.

Interferon-alpha/beta genes are up-regulated in murine brain astrocytes after infection with Theiler's murine encephalomyelitis virus

This article reports the production of interferon alpha/beta (IFN-alpha/beta) by SJL/J mouse brain astrocyte cultures infected with Theiler's murine encephalomyelitis virus (TMEV). cRNA from mock- and TMEV-infected SJL/J astrocytes was hybridized to the Affymetrix whole murine genome DNA microarray. Analysis revealed the up-regulation of 3 sequences coding for the IFN-alpha/beta domain. Increased expression of mRNA coding for IFN-alpha was shown by conventional RT-PCR and quantitative real-time RT-PCR. According to ELISA, the concentration of IFN-alpha in the supernatants of infected astrocyte cultures varied with the multiplicity of infection and post-infection time. The IFN-alpha/beta secreted was biologically active, as shown by a virus-based IFN bioassay involving Cocal virus and TMEV infection. The contribution to total interferon activity was 29% +/- 3.0% for IFN-alpha and 52% +/- 3.6% for IFN-beta. IFN-alpha/beta was induced by whole TMEV virions; induction was not achieved with either purified isolated virion capsid proteins or UV-inactivated virus. Further, induction was inhibited by specific anti-TMEV antibodies. The receptor for IFN-alpha/beta, which is absent in uninfected astrocytes, was up-regulated after infection, as suggested by DNA hybridization analysis. The brains of infected mice contained IFN-alpha/beta mRNA during the acute encephalitis phase, peaking at day 5 post-infection. Our findings could have significance for human diseases such as viral encephalitis and multiple sclerosis.

Innate but not adaptive immune responses contribute to behavioral seizures following viral infection

PURPOSE

To examine the role of innate immunity in a novel viral infection-induced seizure model.

METHODS

C57BL/6 mice, mouse strains deficient in interleukin (IL)-1RI, IL-6, tumor necrosis factor (TNF)-RI, or myeloid differentiation primary response gene 88 (MyD88), or transgenic mice (OT-I) were infected with Theiler's murine encephalomyelitis virus (TMEV) or were mock infected. Mice were followed for acute seizures. Tissues were examined for neuron loss, the presence of virus (viral RNA and antigen), perivascular cuffs, macrophages/microglia, and gliosis, and mRNA expression of IL-1, TNF-alpha, and IL-6.

RESULTS

IL-1 does not play a major role in seizures, as IL-1RI- and MyD88-deficient mice displayed a comparable seizure frequency relative to controls. In contrast, TNF-alpha and IL-6 appear to be important in the development of seizures, as only 10% and 15% of TNF-RI- and IL-6-deficient mice, respectively, showed signs of seizure activity. TNF-alpha and IL-6 mRNA levels also increased in mice with seizures. Inflammation (perivascular cuffs, macrophages/microglia, and gliosis) was greater in mice with seizures. OT-I mice (virus persists) had a seizure rate that was comparable to controls (no viral persistence), thereby discounting a role for TMEV-specific T cells in seizures.

DISCUSSION

We have implicated the innate immune response to viral infection, specifically TNF-alpha and IL-6, and concomitant inflammatory changes in the brain as contributing to the development of acute seizures. This model is a potential infection-driven model of mesial temporal lobe epilepsy with hippocampal sclerosis.

Interleukin-6 as a mechanism for the adverse effects of social stress on acute Theiler's virus infection

Prior exposure to social disruption stress (SDR) exacerbates both the acute and chronic phase of Theiler's murine encephalomyelitis virus infection (TMEV; [Johnson, R.R., Storts, R., Welsh, T.H., Jr., Welsh, C.J., Meagher, M.W., 2004. Social stress alters the severity of acute Theiler's virus infection. J. Neuroimmunol. 148, 74--85; Johnson, R.R., Prentice, T.W., Bridegam, P., Young, C.R., Steelman, A.J., Welsh, T.H., Welsh, C.J.R., Meagher, M.W., 2006. Social stress alters the severity and onset of the chronic phase of Theiler's virus infection. J. Neuroimmunol. 175, 39--51]). However, the neuroimmune mechanism(s) mediating this effect have not been determined. The present study examined whether stress-induced increases in the proinflammatory cytokine interleukin-6 (IL-6) contributes to the adverse effects of SDR on acute TMEV infection. Experiment 1 demonstrated that SDR increases central and peripheral levels of IL-6 and that this effect is reversed by intracerebral ventricular infusion of neutralizing antibody to IL-6 prior to each of six SDR sessions. Although SDR reduced the sensitivity of spleen cells to the anti-inflammatory effects of corticosterone, the neutralizing antibody to IL-6 did not alter this effect. To investigate whether stress-induced increases in IL-6 contribute to the exacerbation of acute TMEV infection, Experiment 2 examined whether intracerebral administration of neutralizing antibody to IL-6 during SDR would prevent the subsequent exacerbation of acute TMEV infection. Experiment 3 then replaced the social stress with intracerebral infusion of IL-6 to assess sufficiency. As expected, prior exposure to SDR subsequently increased infection-related sickness behaviors, motor impairment, CNS viral titers, and CNS inflammation. These deleterious effects of SDR were either prevented or significantly attenuated by intracerebral infusion of neutralizing antibody to IL-6 during the stress exposure period. However, infusion of IL-6 alone did not mimic the adverse effects of SDR. We conclude that IL-6 is necessary but not sufficient to exacerbate acute TMEV infection.

Consequences of CXCL10 and IL-6 induction by the murine IFN-alpha1 transgene in ocular herpes simplex virus type 1 infection

Herpes simplex virus type 1 infection of the mouse eye results in an impressive inflammatory response culminating in the death of the animal or the establishment of a "latent" infection depending on a number of ill-defined variables that include components of the innate and adaptive immune system. The application of type I interferon transgenes has been found to antagonize viral replication and spread from the eye to the nervous system. Associated with the in situ transfection of the cornea is the upregulation of two inflammatory molecules, interleukin-6 and CXCL10. In this article, we will further examine the contribution these molecules may have in the host response to ocular infection with herpes simplex virus type 1.

Theiler's virus infection: a model for multiple sclerosis

Both genetic background and environmental factors, very probably viruses, appear to play a role in the etiology of multiple sclerosis (MS). Lessons from viral experimental models suggest that many different viruses may trigger inflammatory demyelinating diseases resembling MS. Theiler's virus, a picornavirus, induces in susceptible strains of mice early acute disease resembling encephalomyelitis followed by late chronic demyelinating disease, which is one of the best, if not the best, animal model for MS. During early acute disease the virus replicates in gray matter of the central nervous system but is eliminated to very low titers 2 weeks postinfection. Late chronic demyelinating disease becomes clinically apparent approximately 2 weeks later and is characterized by extensive demyelinating lesions and mononuclear cell infiltrates, progressive spinal cord atrophy, and axonal loss. Myelin damage is immunologically mediated, but it is not clear whether it is due to molecular mimicry or epitope spreading. Cytokines, nitric oxide/reactive nitrogen species, and costimulatory molecules are involved in the pathogenesis of both diseases. Close similarities between Theiler's virus-induced demyelinating disease in mice and MS in humans, include the following: major histocompatibility complex-dependent susceptibility; substantial similarities in neuropathology, including axonal damage and remyelination; and paucity of T-cell apoptosis in demyelinating disease. Both diseases are immunologically mediated. These common features emphasize the close similarities of Theiler's virus-induced demyelinating disease in mice and MS in humans.

Differential expression of TGF-beta, IL-2, and other cytokines in the CNS of Theiler's murine encephalomyelitis virus-infected susceptible and resistant strains of mice

Intracranial inoculation of susceptible SJL mice with Theiler's murine encephalomyelitis virus (TMEV) results in biphasic disease consisting of early acute disease, followed by late chronic demyelinating disease, associated with mononuclear infiltrates and demyelinating lesions. In contrast, resistant C57BL/6 (B6) mice develop only early acute disease. We employed cytokine-specific RT-PCR to determine the expression of cytokine transcripts in the CNS of TMEV-infected SJL and B6 mice. During early acute disease, we have found a strong proinflammatory (Th1) cytokine response in the CNS of both TMEV-infected SJL and B6 mice, demonstrated by the expression of transcripts for IFN-gamma, IL-1, IL-6, IL-12p40, and TNF-alpha. At 8 days postinfection (p.i.), TGF-beta1 and TNF-alpha transcripts were present at significantly higher levels (P < 0.01) in the CNS of SJL susceptible mice in comparison to those found in the CNS of B6 mice. Immunohistochemical staining revealed that TGF-beta protein was expressed in leptomeningeal mononuclear inflammatory cell infiltrates in the brain of SJL mice but not in B6 mice, at 8 days p.i. TGF-beta may be responsible for the failure of SJL mice to develop an effective anti-TMEV CTL response. During late chronic demyelinating disease, high levels of proinflammatory Th1 cytokines were found in the CNS of SJL mice, but not B6 mice. Significantly higher levels (P < 0.01) of anti-inflammatory cytokine transcripts (IL-4, IL-5, and IL-10 (Th2 cytokines) and TGF-beta) were found in the spinal cord of TMEV-infected SJL mice with chronic demyelinating disease than in the spinal cord of B6 mice during the same time period (39 or 60 days p.i.). These anti-inflammatory cytokines may contribute to the downregulation of the proinflammatory response in SJL mice. High levels of IL-2 transcripts and protein appeared transiently in the spinal cord of TMEV-infected SJL mice before the onset of demyelinating disease and coincided with an influx of new T cells into the CNS and/or expansion of remaining T cells that have not been eliminated after viral clearance.

The relationship between interleukin-6 and herpes simplex virus type 1: implications for behavior and immunopathology

Cytokines are hormones once thought to be restricted to the immune system produced solely by hematopoietic-derived cells and acting on receptors expressed by cells of the immune system. However, it is now clear that many cytokines are produced not only by lymphocytes, monocytes, granulocytes, and dendritic cells but are also synthesized by cells outside the realm of the immune system in response to stimuli that may not be associated with immune homeostasis. In fact, there is evidence supporting a role of selected cytokines modifying behavior and neuroendocrine function. Recently, a potential relationship between the cytokine interleukin (IL)-6 and herpes simplex virus type 1 (HSV-1) reactivation has been found. This article discusses the relevance of these findings and considers the potential impact that HSV-1 infection has on behavior and chronic inflammatory processes that can occur in the nervous system during "latent" virus infection as a result of chronic IL-6 expression.

Theiler's murine encephalomyelitis virus infection induces early expression of c-fos in astrocytes

We have determined whether Theiler's murine encephalomyelitis virus (TMEV), a picornavirus that produces demyelination in genetically susceptible strains of mice, induces c-fos in pure quiescent cultures of mouse brain astrocytes. As observed in Northern blots, the expression of this immediate early gene increases in a dose-dependent manner, with its expression peaking at a multiplicity of infection of 100. The expression of c-fos is transient, peaking after 30 min and disappearing 2 h after infection. The virus is quickly internalized at 37 degrees C upon binding to its specific receptor located at the cell surface and is actively replicated in the cytoplasm of the astrocytes, as demonstrated by FACS flow cytometry. Using the same technique, nuclear translation of c-fos mRNA is also shown. The specificity of viral induction is demonstrated by its neutralization with TMEV-specific antibodies and by the fact that only viral particles and not purified protein components VP1, VP2, and VP3 induced proto-oncogene expression. This rapid induction of c-fos in astrocytes could be the first stage in the infection of these central nervous system cell populations by TMEV. The biological relevance of these findings is assessed by the demonstration of c-fos activation after viral infection in vivo.

Cytokine actions in the central nervous system

Cytokines and chemokines have been implicated in contributing to the initiation, propagation and regulation of immune and inflammatory responses. Also, these soluble mediators have important roles in contributing to a wide array of neurological diseases such as multiple sclerosis, AIDS Dementia Complex, stroke and Alzheimer's disease. Cytokines and chemokines are synthesized within the central nervous system by glial cells and neurons, and have modulatory functions on these same cells via interactions with specific cell-surface receptors. In this article, I will discuss the ability of glial cells and neurons to both respond to, and synthesize, a variety of cytokines. The emphasize will be on three select cytokines; interferon-gamma (IFN-gamma), a cytokine with predominantly proinflammatory effects; interleukin-6 (IL-6), a cytokine with both pro- and anti-inflammatory properties; and transforming growth factor-beta (TGF-beta), a cytokine with predominantly immunosuppressive actions. The significance of these cytokines to neurological diseases with an immunological component will be discussed.

The endogenous cannabinoid anandamide potentiates interleukin-6 production by astrocytes infected with Theiler's murine encephalomyelitis virus by a receptor-mediated pathway

Theiler's murine encephalomyelitis virus (TMEV) infection of a susceptible strain of mice results in virus persistence in the brain and chronic primary immune-mediated demyelination, which resembles multiple sclerosis. Recent attention has focused on the anti-inflammatory and immunosuppressive properties of interleukin-6, a pleiotropic cytokine involved in the regulation of immunological responses, acute phase protein production and hematopoiesis. Anandamide (arachidonoyl ethanolamine) is a natural brain constituent that binds a specific brain cannabinoid receptor. In this study we investigated whether anandamide can modify interleukin-6 production by primary cultures of murine brain cortical astrocytes infected with TMEV. Astrocytes from susceptible (SJL/J) and resistant (BALB/c) strains of mice infected with TMEV (10(5)PFU/well) increased IL-6 release over a period of 24 h. Anandamide caused an enhancement of the release of IL-6 by TMEV-infected astrocytes in a concentration-dependent manner (1-25 microM). Treatment of TMEV-infected astrocytes with 10 microM arachidonyl trifluoromethyl ketone, a potent inhibitor of the amidase that degrades anandamide, was found to potentiate the effects of anandamide on IL-6 release. A novel and selective cannabinoid receptor antagonist, SR 141617A, blocked the enhancing effects of anandamide on IL-6 release by TMEV-infected astrocytes, suggesting a cannabinoid receptor-mediated pathway. The physiological implications of these results are unknown, but may be related to the hypothesis of the protective effects of cannabinoids on neurological disorders like multiple sclerosis.

Physiological and pathological roles of interleukin-6 in the central nervous system

The cytokine interleukin-6 (IL-6) is an important mediator of inflammatory and immune responses in the periphery. IL-6 is produced in the periphery and acts systemically to induce growth and differentiation of cells in the immune and hematopoietic systems and to induce and coordinate the different elements of the acute-phase response. In addition to these peripheral actions, recent studies indicate that IL-6 is also produced within the central nervous system (CNS) and may play an important role in a variety of CNS functions such as cell-to-cell signaling, coordination of neuroimmune responses, protection of neurons from insult, as well as neuronal differentiation, growth and survival. IL-6 may also contribute to the etiology of neuropathological disorders. Elevated levels of IL-6 in the CNS are found in several neurological disorders including AIDS dementia complex, Alzheimer's disease, multiple sclerosis, systemic lupus erythematosus, CNS trauma, and viral and bacterial meningitis. Moreover, several studies have shown that chronic overexpression of IL-6 in transgenic mice can lead to significant neuroanatomical and neurophysiological changes in the CNS similar to that commonly observed in various neurological diseases. Thus, it appears that IL-6 may play a role in both physiological and pathophysiological processes in the CNS.

Interleukin-6 (IL-6)--a molecule with both beneficial and destructive potentials

Interleukin-6 (IL-6), a member of the neuropoietic cytokine family, initially was described in terms of its activities in the immune system and during inflammation. Accumulating evidence supports an essential role of IL-6 in the development, differentiation, regeneration and degeneration of neurons in the peripheral and central nervous system. Major sites of IL-6 synthesis are neurons and glial cells. Interleukin-6 functions are mediated by a specific receptor system composed of a binding site and a signal transducer. This receptor system can be modulated by a complex of IL-6 and soluble IL-6 receptor acting as agonist. The IL-6 can exert completely opposite actions on neurons, triggering either neuronal survival after injury or causing neuronal degeneration and cell death in disorders such as Alzheimer's disease. Development of selective IL-6 agonists and antagonists, as well as the usage of soluble IL-6 receptors, offers new possibilities for the treatment of neurodegenerative disorders. Furthermore, optimized genetic mouse models, including transgenic and knockout animals, should help to define the physiological and pathophysiological role of IL-6 in the nervous system.

Central nervous system cytokine mRNA expression following Theiler's murine encephalomyelitis virus infection

DA strain of Theiler's murine encephalomyelitis virus (TMEV) produces a biphasic disease with an initial self-limited acute gray matter polioencephalomyelitis in all strains of mice followed by, in the case of certain susceptible strains of mice, a chronic inflammatory demyelination of the spinal cord with a persistent virus infection. A pathogenic role for T-helper 1 (Th1) cells during the demyelinating phase of disease has been proposed. We characterized the cytokine mRNA expression in the brain and spinal cord of susceptible and resistant strains of mice during the early encephalomyelitic disease and the late demyelination, using a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay. At the time of the encephalomyelitis, both resistant and susceptible mice expressed proinflammatory cytokine mRNAs followed by T-cell derived mRNAs; susceptible mice expressed more IL-12 p40 mRNA than resistant mice. During this early disease, there was no significant difference in Th1 cytokine mRNA expression in the brain and spinal cord among the four strains and relatively little Th2 type cytokine upregulation above levels seen in mock-infected controls. During the late demyelinating disease, susceptible but not resistant mice had evidence of viral genome and a continuous expression of Th1 type cytokine mRNAs. The expression of Th2 cytokine mRNAs varied among the different strains and did not correlate with susceptibility or resistance. The results indicate the complexity of cytokine mRNA expression following TMEV infection and the dependence of the expression on disease pathology, the time following infection and the genetics of the host.

Selective upregulation of cytokine receptor subchain and their intracellular signalling molecules after peripheral nerve injury

Numerous studies have suggested that growth factors and cytokines play an important role in the survival of injured neurons and in neurite elongation. Therefore, intracellular signalling pathways activated by growth factors and cytokine receptors play an important role in neuronal survival or for the re-establishment of connection. Since the JAK (janus kinase)-STAT (signal transducers and activators of transcription) signal transduction pathway is known to play a major role in cytokine receptor signalling, we first examined regulation of JAK gene expression following peripheral nerve injury by in situ hybridization histochemistry. The rat hypoglossal nerve was axotomized unilaterally and the mRNA levels for JAK1, JAK2. JAK3 and TYK2 were examined in the hypoglossal nucleus at postoperative times ranging from 1 to 35 days. Among the JAK family members, JAK2 and JAK3 were substantially increased in injured hypoglossal motoneurons, whereas no significant increases were observed for JAK1 and TYK2. These changes were further confirmed by immunohistochemistry using antibodies specific to JAK2 and JAK3. In addition, we examined the JAK2 and JAK3 associated cytokine receptor components, IL-2R gamma and gp130, which are common to various cytokine receptors. Among these, gp130 immunostaining was upregulated after nerve injury. This was also confirmed by in situ hybridization. These results suggest that the injured neuron prepares the molecular machinery involved in certain cytokine receptor signalling pathways at an early phase of the regenerative process, accelerating for the neuron to respond to cytokines that may regulate survival and/or neurite elongation.

Granulocyte macrophage colony stimulating factor stimulates in vitro proliferation of astrocytes derived from simian mature brains

In the brain, granulocyte-macrophage colony stimulating factor (GM-CSF) may be released by infiltrated cells of the immune system including T and B lymphocytes and mononuclear phagocytes, but also by nervous system resident cells such as microglia and astrocytes. Astrocyte-secreted GM-CSF may play an important role in enhancing the local inflammatory response to central nervous system (CNS) injury and in recruting microglia and activated macrophages. In this study, we demonstrated that GM-CSF, as TNF alpha and IL 6, stimulates in vitro proliferation of simian astrocytes in primary cultures. Results were confirmed by blocking experiments performed with a specific neutralizing mAb directed against GM-CSF. Furthermore, we demonstrated that GM-CSF mediates its effect on these cells through the alpha subunit of the GM-CSF receptor which is constitutively expressed at the membrane of the cultured simian astrocytes as assessed by immunofluorescence. GM-CSF effects on astrocytes could be involved in astrocytosis, a hallmark of various neurological injuries and in inflammatory processes in an autocrine manner.

Immunology of Theiler's murine encephalomyelitis virus infection

Theiler's murine encephalomyelitis virus (TMEV) is a single-stranded RNA virus that belongs to the family of picornaviruses. Intracranial inoculation of susceptible mouse strains with TMEV results in biphasic disease, consisting of early acute disease that resembles poliomyelitis, followed by late chronic demyelinating disease that is characterized by the appearance of chronic inflammatory demyelinating lesions. Susceptibility to TMEV infection is genetically controlled by three loci: one that maps to the H-2D region of the major histocompatibility complex, one to the beta-chain constant region of the T-cell antigen receptor, and one located on chromosome 3. Both early acute and chronic late demyelinating diseases are immunologically mediated. T cells appear to play an important role in the pathogenesis of the disease. TMEV-induced demyelinating disease in mice has extensive similarities with multiple sclerosis, and it is considered one of the best experimental animal models for multiple sclerosis.