Interferon (IFN) beta acts downstream of IFN-gamma-induced class II transactivator messenger RNA accumulation to block major histocompatibility complex class II gene expression and requires the 48-kD DNA-binding protein, ISGF3-gamma

IFNh and IRF9 influence the transcription of MHCII mediated by IFNγ to maintain immune balance in sea perch lateolabrax japonicus

The major histocompatibility complex class II (MHCII) molecules are crucial elements of the adaptive immune system, essential for orchestrating immune responses against foreign pathogens. However, excessive expression of MHCII can disrupt normal physiological functions. Therefore, the host employs various mechanisms to regulate MHCII expression and maintain immune homeostasis. Despite this importance, limited studies have explored the negative regulation of MHCII transcription in bony fish. In this study, we found that interferon h (IFNh), a subtype of type I IFN in sea perch Lateolabrax japonicus, could inhibit the activation of IFNγ induced-MHCII expression by modulating the transcription of the class II major histocompatibility complex transactivator (CIITA). Transcriptome analysis revealed 57 up-regulated and 69 down-regulated genes in cells treated with both IFNγ and IFNh compared to those treated with IFNγ alone. To maintain cellular homeostasis, interferon regulatory factor 9 (IRF9) was up-regulated following IFNγ stimulation, thereby preventing MHCII overexpression. Mechanistically, IRF9 bound to the CIITA promoter and suppressed its expression activated by IRF1. Furthermore, IRF9 inhibited the promoter activity of both MHCII-α and MHCII-β induced by CIITA. Our findings highlight the roles of IFNh and IRF9 as suppressors regulating MHCII expression at different hierarchical levels. This study provides insights into the intricate regulation of antigen presentation and the foundation for further exploration of the interaction mechanisms between aquatic virus and fish.

Pharmacological modulation of inflammatory oligodendrocyte progenitor cells using three multiple sclerosis disease modifying therapies in vitro

Preclinical studies of pro-remyelinating therapies for multiple sclerosis tend to neglect the effect of the disease-relevant inflammatory milieu. Interferon-gamma (IFN-γ) is known to suppress oligodendrocyte progenitor cell (OPC) differentiation and induce a recently described immune OPC (iOPC) phenotype characterized by expression of major histocompatibility complex (MHC) molecules. We tested the effects of cladribine (CDB), dimethylfumarate (DMF), and interferon-beta (IFN-β), existing anti-inflammatory therapies for MS, on the IFN-γ-induced iOPC formation and OPC differentiation block. In line with previous reports, we demonstrate that IFN-β and DMF inhibit OPC proliferation, while CDB had no effect. None of the drugs exhibited cytotoxic effects at the physiological concentrations tested in vitro. In a differentiation assay, none of the drugs were able to promote differentiation, under inflammatory or basal conditions. To study drug effects on iOPCs, we monitored MHC expression in vitro with live cell imaging using cells isolated from MHC reporter mice. IFN-β suppressed induction of MHC class II, and DMF led to suppression of both class I and II. CDB had no effect on MHC induction. We conclude that promoting proliferation and differentiation and suppressing iOPC induction under inflammatory conditions may require separate therapeutic strategies and must be balanced for maximal repair. Our in vitro MHC screening assay can be leveraged across cell types to test the effects of drug candidates and disease-related stimuli.

Monocytic HLA-DR Expression in Immune Responses of Acute Pancreatitis and COVID-19

Acute pancreatitis is a common gastrointestinal disease with increasing incidence worldwide. COVID-19 is a potentially life-threatening contagious disease spread throughout the world, caused by severe acute respiratory syndrome coronavirus 2. More severe forms of both diseases exhibit commonalities with dysregulated immune responses resulting in amplified inflammation and susceptibility to infection. Human leucocyte antigen (HLA)-DR, expressed on antigen-presenting cells, acts as an indicator of immune function. Research advances have highlighted the predictive values of monocytic HLA-DR (mHLA-DR) expression for disease severity and infectious complications in both acute pancreatitis and COVID-19 patients. While the regulatory mechanism of altered mHLA-DR expression remains unclear, HLA-DR-/low monocytic myeloid-derived suppressor cells are potent drivers of immunosuppression and poor outcomes in these diseases. Future studies with mHLA-DR-guided enrollment or targeted immunotherapy are warranted in more severe cases of patients with acute pancreatitis and COVID-19.

A genetic screen in macrophages identifies new regulators of IFNγ-inducible MHCII that contribute to T cell activation

Cytokine-mediated activation of host immunity is central to the control of pathogens. Interferon-gamma (IFNγ) is a key cytokine in protective immunity that induces major histocompatibility complex class II molecules (MHCII) to amplify CD4⁺ T cell activation and effector function. Despite its central role, the dynamic regulation of IFNγ-induced MHCII is not well understood. Using a genome-wide CRISPR-Cas9 screen in murine macrophages, we identified genes that control MHCII surface expression. Mechanistic studies uncovered two parallel pathways of IFNγ-mediated MHCII control that require the multifunctional glycogen synthase kinase three beta (GSK3β) or the mediator complex subunit 16 (MED16). Both pathways control distinct aspects of the IFNγ response and are necessary for IFNγ-mediated induction of the MHCII transactivator Ciita, MHCII expression, and CD4⁺ T cell activation. Our results define previously unappreciated regulation of MHCII expression that is required to control CD4⁺ T cell responses.

Interferon β, an enhancer of the innate immune response against SARS-CoV-2 infection

COVID-19 exhibits a global health threat among the elderly and the population with underlying health conditions. During infection, the host's innate immune response acts as a frontline of defense by releasing cytokines such as type I interferon (IFN α and β) thereby initiating antiviral activity. However, this particular interferon response is interrupted by factors such as SARS-CoV-2 non-structural proteins, aging, diabetes, and germ-line errors eventually making the host more susceptible to illness. Therefore, enhancing the host's innate immune response by administering type I IFN could be an effective treatment against COVID-19. Here, we highlight the importance of innate immune response and the role of IFN β monotherapy against COVID-19.

IFNs Drive Development of Novel IL-15-Responsive Macrophages

Disruption in homeostasis of IL-15 is linked to poor maternal and fetal outcomes during pregnancy. The only cells described to respond to IL-15 at the early maternal-fetal interface have been NK cells. We now show a novel population of macrophages, evident in several organs but enriched in the uterus of mice and humans, expressing the β-chain of the IL-15R complex (CD122) and responding to IL-15. CD122+ macrophages (CD122+Macs) are morphologic, phenotypic, and transcriptomic macrophages that can derive from bone marrow monocytes. CD122+Macs develop in the uterus and placenta with kinetics that mirror IFN activity at the maternal-fetal interface. M-CSF permits macrophages to express CD122, and IFNs are sufficient to drive expression of CD122 on macrophages. Neither type I nor type II IFNs are required to generate CD122+Macs, however. In response to IL-15, CD122+Macs activate the ERK signaling cascade and enhance production of proinflammatory cytokines after stimulation with the TLR9 agonist CpG. Finally, we provide evidence of human cells that phenocopy murine CD122+Macs in secretory phase endometrium during the implantation window and in first-trimester uterine decidua. Our data support a model wherein IFNs local to the maternal-fetal interface direct novel IL-15-responsive macrophages with the potential to mediate IL-15 signals critical for optimal outcomes of pregnancy.

Potential pharmacological approaches for the treatment of HIV-1 associated neurocognitive disorders

HIV associated neurocognitive disorders (HAND) are the spectrum of cognitive impairments present in patients infected with human immunodeficiency virus type 1 (HIV-1). The number of patients affected with HAND ranges from 30 to 50% of HIV infected individuals and although the development of combinational antiretroviral therapy (cART) has improved longevity, HAND continues to pose a significant clinical problem as the current standard of care does not alleviate or prevent HAND symptoms. At present, the pathological mechanisms contributing to HAND remain unclear, but evidence suggests that it stems from neuronal injury due to chronic release of neurotoxins, chemokines, viral proteins, and proinflammatory cytokines secreted by HIV-1 activated microglia, macrophages and astrocytes in the central nervous system (CNS). Furthermore, the blood-brain barrier (BBB) not only serves as a route for HIV-1 entry into the brain but also prevents cART therapy from reaching HIV-1 brain reservoirs, and therefore could play an important role in HAND. The goal of this review is to discuss the current data on the epidemiology, pathology and research models of HAND as well as address the potential pharmacological treatment approaches that are being investigated.

Interferon beta-1a induces expression of brain-derived neurotrophic factor in human T lymphocytes in vitro and not in vivo

Aim: To detect IFN β-1a-induced expression of brain-derived neurotrophic factor (BDNF) to undermine the hypothesis of IFN β-1a-associated neuroprotection in multiple sclerosis (MS). Methods: The influence of IFN β-1a on in vitro activated peripheral blood lymphocytes from healthy donors was tested. Proliferation analyses were made to detect T-cell growth. BDNF expression was measured by standard ELISA. To assess the influence of IFN β-1a on BDNF expression in vivo, BDNF serum levels of MS patients treated with IFN β-1a were compared with those of untreated patients. Results: IFN β-1a inhibited T-cell proliferation dose dependently. It induced BDNF expression at middle concentrations. MS patients treated with IFN β-1a exhibited significantly lower BDNF serum levels than untreated patients. Conclusion: IFN β-1a may promote neuroprotection by inducing BDNF expression, but its importance in vivo remains open.

Type I Interferons in NeuroHIV

Infection with Human Immunodeficiency Virus (HIV)-1 continues to cause HIV-associated neurocognitive disorders despite combined antiretroviral therapy. Interferons (IFNs) are important for any antiviral immune response, but the lasting production of IFNα causes exhaustive activation leading eventually to progression to AIDS. Expression of IFNα in the HIV-exposed central nervous system has been linked to cognitive impairment and inflammatory neuropathology. In contrast, IFNβ exerts anti-inflammatory effects, appears to control, at least temporarily, lentiviral infection in the brain and provides neuroprotection. The dichotomy of type I IFN effects on HIV-1 infection and the associated brain injury will be discussed in this review, because the underlying mechanisms require further investigation to allow harnessing these innate immune factors for therapeutic purposes.

Comprehensive Antiretroviral Restriction Factor Profiling Reveals the Evolutionary Imprint of the ex Vivo and in Vivo IFN-β Response in HTLV-1-Associated Neuroinflammation

HTLV-1-Associated Myelopathy (HAM/TSP) is a progressive neuroinflammatory disorder for which no disease-modifying treatment exists. Modest clinical benefit from type I interferons (IFN-α/β) in HAM/TSP contrasts with its recently identified IFN-inducible gene signature. In addition, IFN-α treatment in vivo decreases proviral load and immune activation in HAM/TSP, whereas IFN-β therapy decreases tax mRNA and lymphoproliferation. We hypothesize this "IFN paradox" in HAM/TSP might be explained by both cell type- and gene-specific effects of type I IFN in HTLV-1-associated pathogenesis. Therefore, we analyzed ex vivo transcriptomes of CD4⁺ T cells, PBMCs and whole blood in healthy controls, HTLV-1-infected individuals, and HAM/TSP patients. First, we used a targeted approach, simultaneously quantifying HTLV-1 mRNA (HBZ, Tax), proviral load and 42 host genes with known antiretroviral (anti-HIV) activity in purified CD4⁺ T cells. This revealed two major clusters ("antiviral/protective" vs. "proviral/deleterious"), as evidenced by significant negative (TRIM5/TRIM22/BST2) vs. positive correlation (ISG15/PAF1/CDKN1A) with HTLV-1 viral markers and clinical status. Surprisingly, we found a significant inversion of antiretroviral activity of host restriction factors, as evidenced by opposite correlation to in vivo HIV-1 vs. HTLV-1 RNA levels. The anti-HTLV-1 effect of antiviral cluster genes was significantly correlated to their adaptive chimp/human evolution score, for both Tax mRNA and PVL. Six genes of the proposed antiviral cluster underwent lentivirus-driven purifying selection during primate evolution (TRIM5/TRIM22/BST2/APOBEC3F-G-H), underscoring the cross-retroviral evolutionary imprint. Secondly, we examined the genome-wide type I IFN response in HAM/TSP patients, following short-term ex vivo culture of PBMCs with either IFN-α or IFN-β. Microarray analysis evidenced 12 antiretroviral genes (including TRIM5α/TRIM22/BST2) were significantly up-regulated by IFN-β, but not IFN-α, in HAM/TSP. This was paralleled by a significant decrease in lymphoproliferation by IFN-β, but not IFN-α treatment. Finally, using published ex vivo whole blood transcriptomic data of independent cohorts, we validated the significant positive correlation between TRIM5, TRIM22, and BST2 in HTLV-1-infected individuals and HAM/TSP patients, which was independent of the HAM/TSP disease signature. In conclusion, our results provide ex vivo mechanistic evidence for the observed immunovirological effect of in vivo IFN-β treatment in HAM/TSP, reconcile an apparent IFN paradox in HTLV-1 research and identify biomarkers/targets for a precision medicine approach.

IFNβ Protects Neurons from Damage in a Murine Model of HIV-1 Associated Brain Injury

Infection with human immunodeficiency virus-1 (HIV-1) causes brain injury. Type I interferons (IFNα/β) are critical mediators of any anti-viral immune response and IFNβ has been implicated in the temporary control of lentiviral infection in the brain. Here we show that transgenic mice expressing HIV-1 envelope glycoprotein 120 in their central nervous system (HIVgp120tg) mount a transient IFNβ response and provide evidence that IFNβ confers neuronal protection against HIVgp120 toxicity. In cerebrocortical cell cultures, neuroprotection by IFNβ against gp120 toxicity is dependent on IFNα receptor 1 (IFNAR1) and the β-chemokine CCL4, as IFNAR1 deficiency and neutralizing antibodies against CCL4, respectively, abolish the neuroprotective effects. We find in vivo that IFNβ mRNA is significantly increased in HIVgp120tg brains at 1.5, but not 3 or 6 months of age. However, a four-week intranasal IFNβ treatment of HIVgp120tg mice starting at 3.5 months of age increases expression of CCL4 and concomitantly protects neuronal dendrites and pre-synaptic terminals in cortex and hippocampus from gp120-induced damage. Moreover, in vivo and in vitro data suggests astrocytes are a major source of IFNβ-induced CCL4. Altogether, our results suggest exogenous IFNβ as a neuroprotective factor that has potential to ameliorate in vivo HIVgp120-induced brain injury.

Giving CD4+ T cells the slip: viral interference with MHC class II-restricted antigen processing and presentation

Activation of CD4+ T cells through interactions with peptides bound to Major Histocompatibility Complex Class II (MHC-II) molecules is a crucial step in clearance of most pathogens. Consequently, many viruses have evolved ways of blocking this aspect of adaptive immunity, from specific targeting of processing and presentation components to modulation of signaling pathways that regulate peptide presentation in addition to many other host defense mechanisms. Such cases of interference are far less common compared to what has been elucidated in MHC-I processing and presentation. This may be attributable in part to the complexity of MHC-II antigen processing, the scope of which is only now coming to light.

Relapsing-remitting multiple sclerosis and chronic idiopathic neutropenia: a challenging combination

We report the challenges of treating relapsing-remitting multiple sclerosis (MS) in a 31-year-old woman with long-standing chronic idiopathic neutropenia. The treatment with the disease-modifying therapy interferon-β was significantly complicated by a further fall in her generally low neutrophil count, to values below 0.5×10(9)/l, although this recovered rapidly when the treatment was stopped. We discuss the difficulties of balancing the risk of neutropenia with a risk of MS relapse.

Contrasting effects of IFNα on MHC class II expression in professional vs. nonprofessional APCs: Role of CIITA type IV promoter

We previously demonstrated that, in ex vivo cultures, IFNα downregulates the expression of MHC class II (MHCII) genes in human non-professional APCs associated with pancreatic islets. IFNα has an opposing effect on MHCII expression in professional APCs. In this study, we found that the mechanism responsible for the IFNα-mediated MHCII's downregulation in human MHCII-positive non-professional antigen presenting human non-hematopoietic cell lines is the result of the negative feedback system that regulates cytokine signal transduction, which eventually inhibits promoters III and IV of CIITA gene. Because the CIITA-PIV isoform is mostly responsible for the constitutive expression of MHCII genes in non-professional APCs, we pursued and achieved the specific knockdown of CIITA-PIV mRNA in our in vitro system, obtaining a partial silencing of MHCII molecules similar to that obtained by IFNα. We believe that our results offer a new understanding of the potential significance of CIITA-PIV as a therapeutic target for interventional strategies that can manage autoimmune disease and allograft rejection with little interference on the function of professional APCs of the immune system.

PEGylated interferon beta-1a: meeting an unmet medical need in the treatment of relapsing multiple sclerosis

Multiple sclerosis is a chronic autoimmune disease of the central nervous system for which a number of disease-modifying therapies are available, including interferon beta (Avonex®, Rebif®, and Betaseron/Betaferon®), glatiramer acetate (Copaxone®), and an anti-VLA4 monoclonal antibody (Tysabri®). Despite the availability and efficacy of these protein and peptide drugs, there remains a significant number of patients who are untreated, including those with relatively mild disease who choose not to initiate therapy, those wary of injections or potential adverse events associated with therapy, and those who have stopped therapy due to perceived lack of efficacy. Since these drugs have side effects that may affect a patient's decision to initiate and to remain on treatment, there is a need to provide a therapy that is safe and efficacious but that requires a reduced dosing frequency and hence a concomitant reduction in the frequency of side effects. Here we describe the development of a PEGylated form of interferon beta-1a that is currently being tested in a multicenter, randomized, double-blind, parallel-group, placebo-controlled study in relapsing multiple sclerosis patients, with the aim of determining the safety and efficacy of 125 microg administered via the subcutaneous route every 2 or 4 weeks.

Cooperative contributions of interferon regulatory factor 1 (IRF1) and IRF8 to interferon-γ-mediated cytotoxic effects on oligodendroglial progenitor cells

Background

Administration of exogenous interferon-γ (IFNγ) aggravates the symptoms of multiple sclerosis (MS), whereas interferon-β (IFNβ) is used for treatment of MS patients. We previously demonstrated that IFNγ induces apoptosis of oligodendroglial progenitor cells (OPCs), suggesting that IFNγ is more toxic to OPCs than IFNβ. Thus we hypothesized that a difference in expression profiles between IFNγ-inducible and IFNβ-inducible genes in OPCs would predict the genes responsible for IFNγ-mediated cytotoxic effects on OPCs. We have tested this hypothesis particularly focusing on the interferon regulatory factors (IRFs) well-known transcription factors up-regulated by IFNs.

Methods

Highly pure primary rat OPC cultures were treated with IFNγ and IFNβ. Cell death and proliferation were assessed by MTT reduction, caspse-3-like proteinase activity, Annexin-V binding, mitochondrial membrane potential, and BrdU-incorporation. Induction of all nine IRFs was comprehensively compared by quantitative PCR between IFNγ-treated and IFNβ-treated OPCs. IRFs more strongly induced by IFNγ than by IFNβ were selected, and tested for their ability to induce OPC apoptosis by overexpression and by inhibition by dominant-negative proteins or small interference RNA either in the presence or absence of IFNγ.

Results

Unlike IFNγ, IFNβ did not induce apoptosis of OPCs. Among nine IRFs, IRF1 and IRF8 were preferentially up-regulated by IFNγ. In contrast, IRF7 was more robustly induced by IFNβ than by IFNγ. Overexpressed IRF1 elicited apoptosis of OPCs, and a dominant negative IRF1 protein partially protected OPCs from IFNγ-induced apoptosis, indicating a substantial contribution of IRF1 to IFNγ-induced OPC apoptosis. On the other hand, overexpression of IRF8 itself had only marginal proapoptotic effects. However, overexpressed IRF8 enhanced the IFNγ-induced cytotoxicity and the proapoptotic effect of overexpressed IRF1, and down-regulation of IRF8 by siRNA partially but significantly reduced preapoptotic cells after treatment with IFNγ, suggesting that IRF8 cooperatively enhances IFNγ-induced OPC apoptosis.

Conclusions

This study has identified that IRF1 and IRF8 mediate IFNγ-signaling leading to OPC apoptosis. Therapies targeting at these transcription factors and their target genes could reduce IFNγ-induced OPC loss and thereby enhance remyelination in MS patients.

Induction and function of IFNβ during viral and bacterial infection

Since the discovery of the protein "interferon" over 50 years ago, IFNβ, an antiviral cytokine, has been well studied. In particular, the pathways inducing this cytokine during viral infection have been characterized, leading to the discovery of a multitude of pattern recognition receptors. IFNβ is also induced during bacterial infection, following recognition of bacterial ligands by the host viral and DNA sensors. However, the function of IFNβ during bacterial infection is variable and sometimes detrimental to the host. This review discusses the currently identified receptors and pathways engaged in IFNβ induction during infection, with emphasis on the role of IFNβ during bacterial infection.

Chlamydia muridarum-specific CD4 T-cell clones recognize infected reproductive tract epithelial cells in an interferon-dependent fashion

During natural infections Chlamydia trachomatis urogenital serovars replicate predominantly in the epithelial cells lining the reproductive tract. This tissue tropism poses a unique challenge to host cellar immunity and future vaccine development. In the experimental mouse model, CD4 T cells are necessary and sufficient to clear Chlamydia muridarum genital tract infections. This implies that resolution of genital tract infection depends on CD4 T-cell interactions with infected epithelial cells. However, no laboratory has shown that Chlamydia-specific CD4 T cells can recognize Chlamydia antigens presented by major histocompatibility complex class II (MHC-I) molecules on epithelial cells. In this report we show that MHC-II-restricted Chlamydia-specific CD4 T-cell clones recognize infected upper reproductive tract epithelial cells as early as 12 h postinfection. The timing of recognition and degree of T-cell activation are dependent on the interferon (IFN) milieu. Beta IFN (IFN-beta) and IFN-gamma have different effects on T-cell activation, with IFN-beta blunting IFN-gamma-induced upregulation of epithelial cell surface MHC-II and T-cell activation. Individual CD4 T-cell clones differed in their degrees of dependence on IFN-gamma-regulated MHC-II for controlling Chlamydia replication in epithelial cells in vitro. We discuss our data as they relate to published studies with IFN knockout mice, proposing a straightforward interpretation of the existing literature based on CD4 T-cell interactions with the infected reproductive tract epithelium.

Interferon-triggered transcriptional cascades in the oligodendroglial lineage: a comparison of induction of MHC class II antigen between oligodendroglial progenitor cells and mature oligodendrocytes

Interferon-gamma induces major histocompatibility complex class II (MHC-II) in proliferating oligodendroglial progenitor cells (OPC), but to a much lesser extent in mature oligodendrocytes. Interferon-beta has virtually no effects on MHC-II induction even in OPC. Interferon-gamma-mediated transcriptional induction of CIITA, a critical regulator of MHC-II induction, was 6-fold lower in mature oligodendrocytes than in OPC, and entirely dependent on promoter IV, suggesting that the transcriptional activity of promoter IV is down-regulated after differentiation. The distinct difference in MHC-II induction between interferon-gamma and interferon-beta is attributed to transient interferon-beta-mediated activation of STAT1-IRF1 signaling compared to the sustained interferon-gamma-mediated activation.

IFN-beta impairs superoxide-dependent parasite killing in human macrophages: evidence for a deleterious role of SOD1 in cutaneous leishmaniasis

Type I IFNs (IFN-alpha/beta) have only recently gained considerable attention as immunomodulators in nonviral infectious diseases. IFN-beta has been shown to protect, in a NO-dependent manner, against murine Old World leishmaniasis caused by Leishmania major, but data in New World leishmaniasis are lacking. We found that IFN-beta dose-dependently increases parasite burden in Leishmania amazonensis- as well as Leishmania braziliensis-infected human macrophages, independent of endogenous or exogenous NO. However, IFN-beta significantly reduced superoxide release in Leishmania-infected as well as uninfected human macrophages. This decrease in superoxide production was paralleled by a significant IFN-beta-mediated increase in superoxide dismutase 1 (SOD1) protein levels. Additionally, IFN-beta inhibition of leishmanicidal activity was mimicked by SOD1 and antagonized by either pharmacological or small interfering RNA-mediated inhibition of SOD1. Finally, pronounced SOD1 expression in situ was demonstrated in biopsies from New World cutaneous leishmaniasis patients. These findings reveal a hitherto unknown IFN-beta/SOD1 axis in Leishmania infection and suggest that inhibition of SOD-associated pathways could serve as strategy in the treatment of L. amazonensis as well as L. braziliensis infection, major human pathogens.

Review of interferon beta-1b in the treatment of early and relapsing multiple sclerosis

Multiple sclerosis (MS) is the most common autoimmune illness of the central nervous system. For many years the inflammatory manifestations of MS were treated using only corticosteroids. Since the 1990s the results of several clinical trials with immunomodulatory agents have changed the therapeutic approach to this disease. Interferon beta (IFNbeta)-1b represents the pioneer of those therapies. There is growing evidence from clinical trials on relapsing-remitting MS and clinically isolated syndromes suggestive of MS that IFNbeta-1b reduces the frequency and severity of relapses and the development of new and active brain lesions as assessed by magnetic resonance imaging. Long-term data suggest a persistent efficacy of IFNbeta-1b on disease activity and a positive effect in slowing disability worsening. Furthermore a reduction of relapse rate and a slight positive effect on the progression were demonstrated when IFNbeta-1b was administered to still-active secondary progressive MS. IFNbeta-1b therapy is well tolerated and relatively free of long-term side effects. In spite of the emergence of new agents for the treatment of MS, IFNbeta-1b still remains a first-line therapy with a fundamental role in all stages of the disease.

Flupirtine as neuroprotective add-on therapy in autoimmune optic neuritis

Multiple sclerosis (MS) is a common inflammatory disease of the central nervous system that results in persistent impairment in young adults. During chronic progressive disease stages, there is a strong correlation between neurodegeneration and disability. Current therapies fail to prevent progression of neurological impairment during these disease stages. Flupirtine, a drug approved for oral use in patients suffering from chronic pain, was used in a rat model of autoimmune optic neuritis and significantly increased the survival of retinal ganglion cells, the neurons that form the axons of the optic nerve. When flupirtine was combined with interferon-beta, an established immunomodulatory therapy for MS, visual functions of the animals were improved during the acute phase of optic neuritis. Furthermore, flupirtine protected retinal ganglion cells from degeneration in a noninflammatory animal model of optic nerve transection. Although flupirtine was shown previously to increase neuronal survival by Bcl-2 up-regulation, this mechanism does not appear to play a role in flupirtine-mediated protection of retinal ganglion cells either in vitro or in vivo. Instead, we showed through patch-clamp investigations that the activation of inwardly rectifying potassium channels is involved in flupirtine-mediated neuroprotection. Considering the few side effects reported in patients who receive long-term flupirtine treatment for chronic pain, our results indicate that this drug is an interesting candidate for further evaluation of its neuroprotective potential in MS.

Expression and functional significance of SOCS-1 and SOCS-3 in astrocytes

Astrocytes play a number of important physiological roles in CNS homeostasis. Inflammation stimulates astrocytes to secrete cytokines and chemokines that guide macrophages/microglia and T cells to sites of injury/inflammation. Herein, we describe how these processes are controlled by the suppressor of cytokine signaling (SOCS) proteins, a family of proteins that negatively regulate adaptive and innate immune responses. In this study, we describe that the immunomodulatory cytokine IFN-beta induces SOCS-1 and SOCS-3 expression in primary astrocytes at the transcriptional level. SOCS-1 and SOCS-3 transcriptional activity is induced by IFN-beta through IFN-gamma activation site (GAS) elements within their promoters. Studies in STAT-1alpha-deficient astrocytes indicate that STAT-1alpha is required for IFN-beta-induced SOCS-1 expression, while STAT-3 small interfering RNA studies demonstrate that IFN-beta-induced SOCS-3 expression relies on STAT-3 activation. Specific small interfering RNA inhibition of IFN-beta-inducible SOCS-1 and SOCS-3 in astrocytes enhances their proinflammatory responses to IFN-beta stimulation, such as heightened expression of the chemokines CCL2 (MCP-1), CCL3 (MIP-1alpha), CCL4 (MIP-1beta), CCL5 (RANTES), and CXCL10 (IP-10), and promoting chemotaxis of macrophages and CD4(+) T cells. These results indicate that IFN-beta induces SOCS-1 and SOCS-3 in primary astrocytes to attenuate its own chemokine-related inflammation in the CNS.

Distinct regulation of MHC molecule expression on astrocytes and microglia during viral encephalomyelitis

The potential interplay of glial cells with T cells during viral induced inflammation was assessed by comparing major histocompatibility complex molecule upregulation and retention on astrocytes and microglia. Transgenic mice expressing green fluorescent protein under control of the astrocyte‐specific glial fibrillary acidic protein promoter were infected with a neurotropic coronavirus to facilitate phenotypic characterization of astrocytes and microglia using flow cytometry. Astrocytes in the adult central nervous system up‐regulated class I surface expression, albeit delayed compared with microglia. Class II was barely detectable on astrocytes, in contrast to potent up‐regulation on microglia. Maximal MHC expression in both glial cell types correlated with IFN‐γ levels and lymphocyte accumulation. Despite a decline of IFN‐γ concomitant to virus clearance, MHC molecule expression on glia was sustained. These data demonstrate distinct regulation of both class I and class II expression by microglia and astrocytes in vivo following viral induced inflammation. Furthermore, prolonged MHC expression subsequent to viral clearance implies a potential for ongoing presentation. © 2007 Wiley‐Liss, Inc.

Vaccinia virus infection induces dendritic cell maturation but inhibits antigen presentation by MHC class II

Vaccinia virus (VV) infection is known to inhibit dendritic cells (DC) functions in vitro. Paradoxically, VV is also highly immunogenic and thus has been used as a vaccine. In the present study, we investigated the effects of an in vivo VV infection on DC function by focusing on early innate immunity. Our data indicated that DC are activated upon in vivo VV infection of mice. Splenic DC from VV-infected mice expressed elevated levels of MHC class I and co-stimulatory molecules on their cell surface and exhibited the enhanced potential to produce cytokines upon LPS stimulation. DC from VV-infected mice also expressed a high level of interferon-beta. However, a VV infection resulted in the down-regulation of MHC class II expression and the impairment of antigen presentation to CD4 T cells by DC. Thus, during the early stage of a VV infection, although DC are impaired in some of the critical antigen presentation functions, they can promote innate immune defenses against viral infection.

Pharmacokinetics and pharmacodynamics of the interferon-betas, glatiramer acetate, and mitoxantrone in multiple sclerosis

Five disease-modifying agents are currently approved for long-term treatment of multiple sclerosis (MS), namely three interferon-beta preparations, glatiramer acetate, and mitoxantrone(1). Pharmacokinetics describes the fate of drugs in the human body by studying their absorption, distribution, metabolism and excretion. Pharmacodynamics is dedicated to the mechanisms of action of drugs. The understanding of the pharmacokinetics and pharmacodynamics of the approved disease-modifying agents against MS is of importance as it might contribute to the development of future derivatives with a potentially higher efficacy and a more favourable safety profile. This article reviews data thus far present both on the pharmacokinetics as well as on the putative mechanisms of action of the interferon-betas, glatiramer acetate, and mitoxantrone in the immunopathogenesis of MS.

IL-10 Inhibits Lipopolysaccharide-Induced CD40 Gene Expression through Induction of Suppressor of Cytokine Signaling-3

Costimulation between T cells and APCs is required for adaptive immune responses. CD40, an important costimulatory molecule, is expressed on a variety of cell types, including macrophages and microglia. The aberrant expression of CD40 is implicated in diseases including multiple sclerosis, rheumatoid arthritis, and Alzheimer's disease, and inhibition of CD40 signaling has beneficial effects in a number of animal models of autoimmune diseases. In this study, we discovered that IL-10, a cytokine with anti-inflammatory properties, inhibits LPS-induced CD40 gene expression. We previously demonstrated that LPS induction of CD40 in macrophages/microglia involves both NF-kappaB activation and LPS-induced production of IFN-beta, which subsequently activates STAT-1alpha. IL-10 inhibits LPS-induced IFN-beta gene expression and subsequent STAT-1alpha activation, but does not affect NF-kappaB activation. Our results also demonstrate that IL-10 inhibits LPS-induced recruitment of STAT-1alpha, RNA polymerase II, and the coactivators CREB binding protein and p300 to the CD40 promoter, as well as inhibiting permissive histone H3 acetylation (AcH3). IL-10 and LPS synergize to induce suppressor of cytokine signaling (SOCS)-3 gene expression in macrophages and microglia. Ectopic expression of SOCS-3 attenuates LPS-induced STAT activation, and inhibits LPS-induced CD40 gene expression, comparable to that seen by IL-10. These results indicate that SOCS-3 plays an important role in the negative regulation of LPS-induced CD40 gene expression by IL-10.

Effects of interferon-beta-1a on neuronal survival under autoimmune inflammatory conditions

Interferon-beta-1a (IFN-beta-1a) is an approved treatment for multiple sclerosis (MS). It improves the disease course by reducing the relapse rate as well as the persistent neurological deficits. Recent MRI and post-mortem studies revealed that neuronal and axonal damage are most relevant for chronic disability in MS patients. We have characterized previously time course and mechanisms of neuronal apoptosis in a rat model of myelin oligodendrocyte glycoprotein (MOG)-induced optic neuritis. In this animal model, application of IFN-beta-1a three times per week slightly decreases the loss of retinal ganglion cells (RGCs), the neurons that form the axons within the optic nerve. In contrast to neurotrophic factors, this cytokine does not directly protect cultured RGCs from apoptosis. We conclude that IFN-beta-1a is a suitable candidate to be combined with a directly neuroprotective agent in order to further decrease axonal and neuronal degeneration in MS patients.

Effect of interferon alpha on MHC class II gene expression in ex vivo human islet tissue

Type 1 diabetes (T1D) is caused by autoimmune destruction of the insulin-producing beta-cells of the islets of Langerhans. One still open question is where naive islet-reactive T cells encounter antigens and become stimulated. In this report we have re-examined the expression of MHC class II (MHCII) genes in human islets to further explore the possibility that non-professional antigen presenting cells (APCs) within islets contribute to autoimmunity. Since development of T1D has been linked to viral infections, we also studied ex-vivo MHCII expression in response to interferon-alpha (IFNalpha) in islet tissue and in different APCs. The findings are: first, MHCII genes expression in human islets is linked with the expression of the class II transactivator isoform transcribed from the promoter IV, similar to that described in non-professional APCs. Second, there is IFNalpha-mediated lineage-specific regulation of MHCII genes expression, seen as a decrease in the accumulation of MHCII transcripts in pancreatic islets opposite to an increase in dendritic cells and B-lymphoblastoid cell lines. Third, there is allele-specific regulation of the HLA-DQA1 gene by IFNalpha in islet tissue. These findings may begin to explain the molecular events that create favorable conditions for organ-specific autoimmunity and explain the incomplete penetrance of T1D susceptibility alleles.

IFN‐β‐induced SOCS‐1 negatively regulates CD40 gene expression in macrophages and microglia

Costimulation between T cells and antigen-presenting cells is required for adaptive immune responses. CD40, a costimulatory molecule, is expressed in macrophages and microglia. The aberrant expression of CD40 is involved in human diseases including multiple sclerosis, rheumatoid arthritis, and Alzheimer's disease. CD40 expression is induced by a variety of stimuli, including IFN-gamma and lipopolysaccharide (LPS). In this study, we describe the molecular basis by which IFN-beta, a cytokine with immunomodulatory properties, regulates CD40 gene expression. IFN-beta induces CD40 expression in macrophages and microglia at the transcriptional level, and GAS elements in the CD40 promoter are required for IFN-beta-induced CD40 promoter activity. The critical role of signal transducers and activators of transcription-1alpha (STAT-1alpha) in this response was confirmed by utilizing primary microglia from STAT-1alpha deficient mice. IFN-beta induces suppressor of cytokine signaling-1 (SOCS-1) gene expression, which inhibits cytokine signaling by inhibiting activation of STAT proteins. The ectopic expression of SOCS-1 abrogates IFN-beta-mediated STAT-1alpha activation and inhibits IFN-beta-induced CD40 expression. IFN-beta-induced recruitment of STAT-1alpha and RNA Pol II and permissive histone modifications on the CD40 promoter are also inhibited by SOCS-1 overexpression. These novel results indicate that IFN-beta-induced SOCS-1 plays an important role in the negative regulation of IFN-beta-induced CD40 gene expression.

Immunomodulatory synergy by combination of atorvastatin and glatiramer acetate in treatment of CNS autoimmunity

One approach to improving efficacy in MS therapy is to identify medications that provide additive or synergistic benefit in combination. Orally administered cholesterol-lowering HMG-CoA reductase inhibitors (known as statins), which exhibit immunomodulatory properties and are effective in treatment of the MS model EAE, are being tested in MS. As atorvastatin can enhance protective Th2 responses and has a different mechanism of action than glatiramer acetate (GA), a parenterally administered immunomodulatory agent approved for MS treatment, we tested whether the combination of these agents could be beneficial in EAE. Combination therapy using suboptimal doses of atorvastatin and GA prevented or reversed clinical and histologic EAE. Secretion of proinflammatory Th1 cytokines was reduced--and conversely Th2 cytokine secretion was increased--in these mice, but not in mice treated with each drug alone at the same doses. Monocytes treated with the combination of suboptimal doses of atorvastatin and GA secreted an antiinflammatory type II cytokine pattern and, when used as APCs, promoted Th2 differentiation of naive myelin-specific T cells. Our results demonstrate that agents with different mechanisms of immune modulation can combine in a synergistic manner for the treatment of CNS autoimmunity and provide rationale for testing the combination of atorvastatin and GA in MS.

Effects of cytokines on microglial phenotypes and astroglial coupling in an inflammatory coculture model

Cytokines play an important role in the onset, regulation, and propagation of immune and inflammatory responses within the central nervous system (CNS). The main source of cytokines in the CNS are microglial cells. Under inflammatory conditions, microglial cells are capable of producing pro- and antiinflammatory cytokines, which convey essential impact on the glial and neuronal environment. One paramount functional feature of astrocytes is their ability to form a functionally coupled syncytium. The structural link, which is responsible for the syncytial behavior of astrocytes, is provided by gap junctions. The present study was performed to evaluate the influence of inflammation related cytokines on an astroglial/microglial inflammatory model. Primary astrocytic cultures of newborn rats were cocultured with either 5% (M5) or 30% (M30) microglial cells and were incubated with the following proinflammatory cytokines: tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interferon-gamma (IFN-gamma), and the antiinflammatory cytokines transforming growth factor-beta1 (TGF-beta1) and IFN-beta. Under these conditions, i.e., incubation with the inflammatory cytokines and the high fraction of microglia (M30), microglial cells revealed a significant increase of activated round phagocytotic cells accompanied by a reduction of astroglial connexin 43 (Cx43) expression, a reduced functional coupling together with depolarization of the membrane resting potential (MRP). When the antiinflammatory mediator TGF-beta1 was added to proinflammatory altered M30 cocultures, a reversion of microglial activation and reconstitution of functional coupling together with recovery of the astroglial MRP was achieved. Finally IFN-beta, added to M5 cocultures was able to prevent the effects of the proinflammatory cytokines TNF-alpha, IL-1beta, and IFN-gamma.

The cytokine IL-1beta activates IFN response factor 3 in human fetal astrocytes in culture

The cytokine IL-1beta is a major activator of primary human fetal astrocytes in culture, leading to the production of a wide range of cytokines and chemokines important in the host defense against pathogens. IL-1beta, like TLR4, signals via the MyD88/IL-1betaR-associated kinase-1 pathway linked to activation of NF-kappaB and AP-1. Recent studies have shown that TLR4 also signals independently of MyD88, resulting in the activation of IFN regulatory factor 3 (IRF3), a transcription factor required for the production of primary antiviral response genes such as IFN-beta. Using a functional genomics approach, we observed that IL-1beta induced in astrocytes a group of genes considered to be IFN-stimulated genes (ISG), suggesting that IL-1beta may also signal via IRF3 in these cells. We now show, using real-time PCR, that in astrocytes IL-1beta induces the expression of IFN-beta, IRF7, CXCL10/IFN-gamma-inducible protein-10, and CCL5/RANTES. Chemokine expression was confirmed by ELISA. We also show that IL-1beta induces phosphorylation and nuclear translocation of IRF3 and delayed phosphorylation of STAT1. The dependency of IFN-beta, IRF7, and CXCL10/IFN-gamma-inducible protein-10 gene expression on IRF3 was confirmed using a dominant negative IRF3-expressing adenovirus. The robust induction by IL-1beta of additional ISG noted on the microarrays, such as STAT1, 2'5'-oligoadenylate synthetase 2, and ISG15, also supports an active signaling role for IL-1beta via this pathway in human fetal astrocytes. These data are the first to show that IL-1beta, in addition to TLRs, can stimulate IRF3, implicating this cytokine as an activator of genes involved in innate antiviral responses in astrocytes.

Identification of tissue-restricted transcripts in human islets

The purpose of our study was to identify transcripts specific for tissue-restricted, membrane-associated proteins in human islets that, in turn, might serve as markers of healthy or diseased islet cell masses. Using oligonucleotide chips, we obtained gene expression profiles of human islets for comparison with the profiles of exocrine pancreas, liver, and kidney tissue. As periislet presence of type 1 interferon is associated with the development of type 1 diabetes, the expression profile of human islets treated ex vivo with interferon-alpha2beta (IFNalpha2beta) was also determined. A set of genes encoding transmembrane- or membrane-associated proteins with novel islet-restricted expression was resolved by determining the intersection of the islet set with the complement of datasets obtained from other tissues. Under the influence of IFNalpha2beta, the expression levels of transcripts for several of the identified gene products were up- or down-regulated. One of the islet-restricted gene products identified in this study, vesicular monoamine transporter type 2, was shown to bind [3H]dihydrotetrabenazine, a ligand with derivatives suitable for positron emission tomography imaging. We report here the first comparison of gene expression profiles of human islets with other tissues and the identification of a target molecule with possible use in determining islet cell masses.

CpG DNA induces a class II transactivator-independent increase in class II MHC by stabilizing class II MHC mRNA in B lymphocytes

Microbial products, such as CpG DNA and LPS, enhance class II MHC (MHC-II) expression and Ag presentation by dendritic cells, but this effect does not occur with macrophages and is largely unexplored in B cells. Although MHC-II expression is influenced by transcriptional regulation, which is governed by class II transactivator (CIITA) in all cells, microbial products enhance MHC-II expression by dendritic cells in part by increasing MHC-II protein stability. In this study, we show that the CpG-induced increase in MHC-II expression by B lymphocytes is not due to protein stabilization or changes in CIITA expression or activity, but instead is due to increased stability of MHC-II mRNA. This CIITA-independent mechanism adds a new layer of complexity to regulation of MHC-II and may increase T cell help for B cell Ab responses to microbial or vaccine Ags.

Edmonston measles virus prevents increased cell surface expression of peptide-loaded major histocompatibility complex class II proteins in human peripheral monocytes

Gamma interferon (IFN-gamma) induces expression of the gene products of the major histocompatibility complex (MHC), whereas IFN-alpha/beta can interfere with or suppress class II protein expression. In separate studies, measles virus (MV) was reported to induce IFN-alpha/beta and to up-regulate MHC class II proteins. In an attempt to resolve this paradox, we examined the surface expression of MHC class I and class II proteins in MV-infected peripheral monocytes in the presence and absence of IFN-alpha/beta. Infection of purified monocytes with Edmonston B MV resulted in an apparent increase in cell surface expression of HLA-A, -B, and -C class I proteins, but it had no effect on the expression of HLA-DR class II proteins. MV-infected purified monocytes expressed IFN-alpha/beta, but no measurable IFN-gamma expression was detected in supernatant fluids. Class II protein expression could be enhanced by coculture of purified monocytes with uninfected peripheral blood mononuclear cell (PBMC) supernatant. MV infection of PBMCs also did not affect expression of class II proteins, but the expression of HLA-A, -B, and -C class I proteins was increased two- to threefold in most donor cells. A direct role for IFN-alpha/beta suppression of MHC class II protein expression was not evident in monocytes since MV suppressed class II protein expression in the absence of IFN-alpha/beta. Taken together, these data suggest that MV interferes with the expression of peptide-loaded class II complexes, an effect that may potentially alter CD4(+)-T-cell proliferation and the cell-mediated immune responses that they help to regulate.

Regulation and function of class II major histocompatibility complex, CD40, and B7 expression in macrophages and microglia: Implications in neurological diseases

The ability of microglia, the brain's resident macrophage, to present antigen through the class II major histocompatibility complex (MHC) to T cells allows these normally quiescent cells to play a critical role in shaping the outcome of many neurological diseases. The expression of class II MHC antigens and the costimulatory molecules CD40 and B7 on microglia and infiltrating macrophages is regulated through a complex network of cytokines in the inflamed brain. In this review, we describe the molecular mechanisms underlying class II MHC, CD40 and B7 regulation in microglia and macrophages. Our focus is on the cis-elements in the promoters of their genes and the transcription factors activated by cytokines that bind them. The functional implications of aberrant class II MHC, CD40 and B7 expression by microglia and macrophages as related to the diseases of Multiple Sclerosis and Alzheimer's Disease are discussed.

Modulation of astrocyte inducible nitric oxide synthase and cytokine expression by interferon beta is associated with induction and inhibition of interferon gamma-activated sequence binding activity

Although interferon (IFN)-beta is firmly established as a therapeutic agent for multiple sclerosis, information regarding its role in astrocyte cytokine production is limited. In primary cultures of human astrocytes, we determined the effects of IFN-beta on astrocyte cytokine [tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-6] and inducible nitric oxide synthase (iNOS) expression by ribonuclease protection assay and ELISA. We found that IFN-beta inhibited astrocyte cytokine/iNOS induced by IL-1 plus IFN-gamma, but in the absence of IFN-gamma, IFN-beta enhanced IL-1-induced cytokine/iNOS expression. Electrophoretic mobility shift analysis (EMSA) demonstrated that IFN-gamma induced sustained IFN-gamma-activated sequence (GAS) binding, while IFN-beta induced transient GAS binding. When used together, IFN-beta inhibited IFN-gamma-induced GAS binding activity. Nuclear factor-kappa B (NF-kappaB) activation was not altered by either IFNs, whereas IFN stimulated response element (ISRE) was only activated by IFN-beta and not IFN-gamma. These results suggest that IFN-beta can both mimic and antagonize the effect of IFN-gamma by modulating induction of nuclear GAS binding activity. Our results demonstrating differential regulation of astrocyte cytokine/iNOS induction by IFN-beta are novel and have implications for inflammatory diseases of the human CNS.

Interferon type I downregulates human parainfluenza virus type 3-induced major histocompatibility complex class II expression

Human parainfluenza virus type 3 (HPIV3) induces major histocompatibility complex (MHC) class II expression in a signal transducer and activator of transcription-1 (STAT1)- and class II transactivator (CIITA)-independent manner. Interferon (IFN)-gamma, the potent inducer of MHC class II, on the other hand, requires both STAT1 and CIITA in the induction process. IFN-alpha/beta has been shown to inhibit the IFN-y-induced expression of MHC class II by targeting a step(s) downstream of CIITA. Here we report that IFN-alpha/beta also inhibits the CIITA-independent expression of HPIV3-induced MHC class II. The inhibitory role of IFN-alpha/beta on HPIV3-induced MHC class II was confirmed by using anti-IFN-alpha/beta antibody and mutant cell lines defective in the IFN signaling components STAT1 and STAT2. IFN-alpha/beta inhibits virus-induced MHC class II expression just as it does IFN-gamma-induced MHC class II. The inhibition by IFN-alpha/beta of MHC class II expression may play a regulatory role in virus induced autoimmune disease mediated by MHC class II aberrant expression.

Cutting edge: oral type I IFN-tau promotes a Th2 bias and enhances suppression of autoimmune encephalomyelitis by oral glatiramer acetate

IFN-tau, a novel type I IFN that possesses immunomodulatory properties, lacks toxicity normally associated with other type I IFNs. We examined the effects of oral IFN-tau alone and in combination with oral glatiramer acetate in experimental allergic encephalomyelitis (EAE). By comparison of oral administration of IFN-alpha, -beta, and -tau to myelin basic protein-specific TCR-transgenic mice, we demonstrate these type I IFNs promote secretion of the Th2 cytokine IL-10 with similar efficiency. Whereas IFN-alpha and -beta induced IFN-gamma secretion, a Th1 cytokine, IFN-tau did not. Oral IFN-tau alone suppressed EAE. When suboptimal doses were administered orally in combination to wild-type mice, IFN-tau and glatiramer acetate had a synergistic beneficial effect in suppression of EAE. This combination was associated with TGF-beta secretion and enhanced IL-10 production. Thus, IFN-tau is a potential candidate for use as a single agent or in combination therapy for multiple sclerosis.

Interferon-beta activates multiple signaling cascades in primary human microglia

Microglia, the resident brain macrophages, are the principal cells involved in the regulation of inflammatory and antimicrobial responses in the CNS. Interferon-beta (IFNbeta) is an antiviral cytokine induced by viral infection or following non-specific inflammatory challenges of the CNS. Because of the well-known anti-inflammatory properties of IFNbeta, it is also used to treat multiple sclerosis, an inflammatory CNS disease. Despite the importance of IFNbeta signaling in CNS cells, little has been studied, particularly in microglia. In this report, we investigated the molecular mechanisms underlying IFNbeta-induced beta-chemokine expression in primary human fetal microglia. Multiple signaling cascades are activated in microglia by IFNbeta, including nuclear factor-kappaB (NF-kappaB), activator protein-1 (AP-1) and Jak/Stat. IFNbeta induced IkappaBalpha degradation and NF-kappaB (p65:p50) DNA binding. Inhibition of NF-kappaB by either adenoviral transduction of a super repressor IkappaBalpha, or an antioxidant inhibitor of NF-kappaB reduced expression of the beta-chemokines, regulated upon activation, normal T-cell expressed and secreted (RANTES) and macrophage inflammatory protein (MIP)-1beta. IFNbeta also induced phosphorylation of extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase, and the MAP kinase kinase 1 (MEK1) inhibitor PD98059 dose-dependently inhibited beta-chemokine mRNA and protein expression. PD98059 did not inhibit NF-kappaB binding, demonstrating that ERK was not responsible for NF-kappaB activation. Two downstream targets of ERK were identified in microglia: AP-1 and Stat1. IFNbeta induced AP-1 nuclear binding activity in microglia and this was suppressed by PD98059. Additionally, IFNbeta induced Stat1 phosphorylation at both tyrosine 701 (Y701) and serine 727 (S727) residues. S727 phosphorylation of Stat1, which is known to be required for maximal transcriptional activation, was inhibited by PD98059. Our results demonstrating multiple signaling cascades initiated by IFNbeta in primary human microglia are novel and have implications for inflammatory and infectious diseases of the CNS.

Interferon-beta directly influences monocyte infiltration into the central nervous system

Interferon-beta (IFN-beta) has beneficial effects on the clinical symptoms of multiple sclerosis (MS) patients, but its exact mechanism of action is yet unknown. We here suggest that IFN-beta directly modulates inflammatory events at the level of cerebral endothelium. IFN-beta treatment resulted in a marked reduction of perivascular infiltrates in acute experimental allergic encephalomyelitis (EAE), the rat model for MS, which was coupled to a major decrease in the expression of the adhesion molecules ICAM-1 and VCAM-1 on brain capillaries. In vitro, IFN-beta reduced the mRNA levels and protein expression of adhesion molecules of brain endothelial cell cultures and diminished monocyte transendothelial migration. Monocyte adhesion and subsequent migration was found to be predominantly regulated by VCAM-1. These data indicate that IFN-beta exerts direct antiinflammatory effects on brain endothelial cells thereby contributing to reduced lesion formation as observed in MS patients.

Treatment of autoimmune diabetes recurrence in non-obese diabetic mice by mouse interferon-beta in combination with an analogue of 1alpha,25-dihydroxyvitamin-D3

Autoimmune diabetes recurrence is in part responsible for islet graft destruction in type 1 diabetic individuals. The aim of the present study was to design treatment modalities able to prevent autoimmune diabetes recurrence after islet transplantation in spontaneously diabetic NOD mice. In order to avoid confusion between autoimmune diabetes recurrence and allograft rejection, we performed syngeneic islet transplantations in spontaneously diabetic NOD mice. Mice were treated with mouse interferon-beta (IFN-beta, 1 x 105 IU/day), a new 14-epi-1,25-(OH)2D3-analogue (TX 527, 5 microg/kg/day) and cyclosporin A (CsA, 7.5 mg/kg/day) as single substances and in combinations. Treatment was stopped either 20 days (IFN-beta and CsA) or 30 days (TX 527) after transplantation. Autoimmune diabetes recurred in 100% of control mice (MST 11 days). None of the mono-therapies significantly prolonged islet graft survival. Combining CsA with TX 527 maintained graft function in 67% of recipients as long as treatment was given (MST 31 days, P < 0.01 versus controls). Interestingly, 100% of the IFN-beta plus TX 527-treated mice had normal blood glucose levels during treatment, and even had a more pronounced prolongation of graft survival (MST 62 days, P < 0.005 versus controls). Cytokine mRNA analysis of the grafts 6 days after transplantation revealed a significant decrease in IL-2, IFN-gamma and IL-12 messages in both IFN-beta plus TX 527- and CsA plus TX 527-treated mice, while only in the IFN-beta with TX 527 group were higher levels of IL-10 transcripts observed. Therefore, we conclude that a combination of IFN-beta and TX 527 delays autoimmune diabetes recurrence in islet grafts in spontaneously diabetic NOD mice.

Human cytomegalovirus inhibition of major histocompatibility complex transcription and interferon signal transduction

Pathogens have evolved diverse mechanisms for escaping host innate and adaptive immunity. Viruses that maintain a persistent infection are particularly effective at disabling key arms of the host immune response. For example, the herpesviruses establish a persistent infection in human and animal hosts, in part through critical immunoevasive strategies. Cytomegalovirus, a beta-herpesvirus, impairs major histocompatibility complex (MHC) class I and class II antigen presentation by decreasing MHC expression on the surface of the infected cell, thus enabling infected cells to escape CD8+ and CD4+ T lymphocyte immunosurveillance. Moreover, cytomegalovirus blocks the interferon signal transduction pathway, thereby limiting the direct and indirect antiviral effects of the interferons. In this review, we focus on an emerging paradigm in which the effectiveness of viruses, particularly human cytomegalovirus, to escape antiviral immune responses is significantly enhanced by their ability to inhibit MHC transcription and interferon (IFN)-stimulated (JAK/STAT) signal transduction.

Contemporary immunomodulatory therapy for multiple sclerosis

Multiple sclerosis (MS) is no longer considered an unmanageable disease. Five drugs have obtained regulatory approval to safely and effectively modify the course of MS. Three preparations of interferon beta-Avonex (interferon beta-1a), Betaseron (interferon beta-1b), and Rebif (interferon beta 1a)-have shown efficacy in relapsing-remitting MS and show promise in slowing the course of secondary progressive MS. Glatiramir acetate (Copaxone) has demonstrated efficacy in relapsing-remitting MS, and is being tested for the management of primary progressive disease. Mitoxantrone (Novantrone) has been approved for secondary progressive and progressive relapsing MS. There is a tendency toward early diagnosis and treatment based on the hypothesis that treatment effectiveness declines with advancing disease.

Immune function of astrocytes

Astrocytes are the major glial cell within the central nervous system (CNS) and have a number of important physiological properties related to CNS homeostasis. The aspect of astrocyte biology addressed in this review article is the astrocyte as an immunocompetent cell within the brain. The capacity of astrocytes to express class II major histocompatibility complex (MHC) antigens and costimulatory molecules (B7 and CD40) that are critical for antigen presentation and T-cell activation are discussed. The functional role of astrocytes as immune effector cells and how this may influence aspects of inflammation and immune reactivity within the brain follows, emphasizing the involvement of astrocytes in promoting Th2 responses. The ability of astrocytes to produce a wide array of chemokines and cytokines is discussed, with an emphasis on the immunological properties of these mediators. The significance of astrocytic antigen presentation and chemokine/cytokine production to neurological diseases with an immunological component is described.

The bare lymphocyte syndrome and the regulation of MHC expression

The bare lymphocyte syndrome (BLS) is a hereditary immunodeficiency resulting from the absence of major histocompatibility complex class II (MHCII) expression. Considering the central role of MHCII molecules in the development and activation of CD4(+) T cells, it is not surprising that the immune system of the patients is severely impaired. BLS is the prototype of a "disease of gene regulation." The affected genes encode RFXANK, RFX5, RFXAP, and CIITA, four regulatory factors that are highly specific and essential for MHCII genes. The first three are subunits of RFX, a trimeric complex that binds to all MHCII promoters. CIITA is a non-DNA-binding coactivator that functions as the master control factor for MHCII expression. The study of RFX and CIITA has made major contributions to our comprehension of the molecular mechanisms controlling MHCII genes and has made this system into a textbook model for the regulation of gene expression.