IP-10 gene transcription by virus in astrocytes requires cooperation of ISRE with adjacent kappaB site but not IRF-1 or viral transcription

CXCL10 Chemokine: A Critical Player in RNA and DNA Viral Infections

Chemokines constitute a group of small, secreted proteins that regulate leukocyte migration and contribute to their activation. Chemokines are crucial inflammatory mediators that play a key role in managing viral infections, during which the profile of chemokine expression helps shape the immune response and regulate viral clearance, improving clinical outcome. In particular, the chemokine ligand CXCL10 and its receptor CXCR3 were explored in a plethora of RNA and DNA viral infections. In this review, we highlight the expression profile and role of the CXCL10/CXCR3 axis in the host defense against a variety of RNA and DNA viral infections. We also discuss the interactions among viruses and host cells that trigger CXCL10 expression, as well as the signaling cascades induced in CXCR3 positive cells.

Higher Cerebrospinal Fluid Soluble Urokinase-type Plasminogen Activator Receptor, But Not Interferon γ-inducible Protein 10, Correlate With Higher Working Memory Deficits

BACKGROUND

We hypothesized that the induction of monocyte activation biomarkers, especially soluble urokinase-type plasminogen activator receptor (suPAR) and interferon γ-inducible protein 10 (IP-10), is lower in HIV-1C than HIV-1B, owing to a defective Tat cysteine dimotif (C30S).

METHODS

A total of 68 paired cerebrospinal fluid (CSF) and blood samples from people with HIV (PWH), free of CNS opportunistic infections, from a Southern Brazil outpatient HIV clinic were evaluated such as HIV-1B subtype (n = 27), HIV-1C (n = 26), other (n = 15), and 19 HIV-negative controls. The levels of suPAR, IP-10, neopterin, and β2 microglobulin (β2m) in the CSF and serum were quantified using different immunoassays.

RESULTS

Overall, in PWH, increases in CSF suPAR, CSF/serum suPAR, and CSF/serum β2m correlated with worse working memory deficits (r = 0.303, 0.353, and 0.289, respectively, all P < 0.05). The medians of IP-10, suPAR, neopterin, and β2m in CSF and serum and the CSF/serum ratio and suPAR index were comparable between the HIV-1B and HIV-1C subtypes. CSF IP-10 and neopterin and serum IP-10 and suPAR levels were higher in PWH than the HIV-negative controls (P = 0.015, P = 0.001, P < 0.0001, and P < 0.001, respectively). The serum β2m level was higher in HIV-associated dementia than neuropsychologically normal or asymptomatic (P = 0.024).

DISCUSSION

We observed that higher levels of CSF suPAR and the suPAR quotient correlated with worse working memory deficit. Elevated levels of monocyte activation were similar in both HIV-1 B and C subtypes, providing no evidence of reduced neuropathogenicity of HIV-1 subtype C Tat compared with subtype B.

Surface Toll-like receptor 3 expression in metastatic intestinal epithelial cells induces inflammatory cytokine production and promotes invasiveness

Toll-like receptors (TLRs) are innate immune receptors for sensing microbial molecules and damage-associated molecular patterns released from host cells. Double-stranded RNA and the synthetic analog polyinosinic:polycytidylic acid (poly(I:C)) bind and activate TLR3. This stimulation leads to recruitment of the adaptor molecule TRIF (Toll/IL-1 resistance (TIR) domain-containing adapter-inducing interferon β) and activation of the transcription factors nuclear factor κB (NF-κB) and interferon regulatory factor 3 (IRF-3), classically inducing IFNβ production. Here we report that, unlike non-metastatic intestinal epithelial cells (IECs), metastatic IECs express TLR3 and that TLR3 promotes invasiveness of these cells. In response to poly(I:C) addition, the metastatic IECs also induced the chemokine CXCL10 in a TLR3-, TRIF-, and IRF3-dependent manner but failed to produce IFNβ. This was in contrast to healthy and non-metastatic IECs, which did not respond to poly(I:C) stimulation. Endolysosomal acidification and the endosomal transporter protein UNC93B1 was required for poly(I:C)-induced CXCL10 production. However, TLR3-induced CXCL10 was triggered by immobilized poly(I:C), was only modestly affected by inhibition of endocytosis, and could be blocked with an anti-TLR3 antibody, indicating that TLR3 can still signal from the cell surface of these cells. Furthermore, plasma membrane fractions from metastatic IECs contained both full-length and cleaved TLR3, demonstrating surface expression of both forms of TLR3. Our results imply that metastatic IECs express surface TLR3, allowing it to sense extracellular stimuli that trigger chemokine responses and promote invasiveness in these cells. We conclude that altered TLR3 expression and localization may have implications for cancer progression.

The role of CXCL10 in the pathogenesis of experimental septic shock

Introduction

The chemokine CXCL10 is produced during infection and inflammation to activate the chemokine receptor CXCR3, an important regulator of lymphocyte trafficking and activation. The goal of this study was to assess the contributions of CXCL10 to the pathogenesis of experimental septic shock in mice.

Methods

Septic shock was induced by cecal ligation and puncture (CLP) in mice resuscitated with lactated Ringer’s solution and, in some cases, the broad spectrum antibiotic Primaxin. Studies were performed in CXCL10 knockout mice and mice treated with anti-CXCL10 immunoglobulin G (IgG). Endpoints included leukocyte trafficking and activation, core body temperature, plasma cytokine concentrations, bacterial clearance and survival.

Results

CXCL10 was present at high concentrations in plasma and peritoneal cavity during CLP-induced septic shock. Survival was significantly improved in CXCL10 knockout (CXCL10KO) mice and mice treated with anti-CXCL10 IgG compared to controls. CXCL10KO mice and mice treated with anti-CXCL10 IgG showed attenuated hypothermia, lower concentrations of interleukin-6 (IL-6) and macrophage inhibitory protein-2 (MIP-2) in plasma and lessened natural killer (NK) cell activation compared to control mice. Compared to control mice, bacterial burden in blood and lungs was lower in CXCL10-deficient mice but not in mice treated with anti-CXCL10 IgG. Treatment of mice with anti-CXCL10 IgG plus fluids and Primaxin at 2 or 6 hours after CLP significantly improved survival compared to mice treated with non-specific IgG under the same conditions.

Conclusions

CXCL10 plays a role in the pathogenesis of CLP-induced septic shock and could serve as a therapeutic target during the acute phase of septic shock.

Characterization of the antiviral and inflammatory responses against Nipah virus in endothelial cells and neurons

Nipah virus (NiV) is a highly pathogenic paramyxovirus which causes fatal encephalitis in up to 75% of infected humans. Endothelial cells and neurons are important cellular targets in the pathogenesis of this disease. In this study, viral replication and the innate immune responses to NiV in these cell types were measured. NiV infected endothelial cells generated a functionally robust IFN-beta response, which correlated with localization of the NiV W protein to the cytoplasm. There was no antiviral response detected in infected neuronal cells. NiV infection of endothelial cells induced a significant increase in secreted inflammatory chemokines, which corresponded with the increased ability of infected cell supernatants to induce monocyte and T-lymphocyte chemotaxis. These results suggest that pro-inflammatory chemokines produced by NiV infected primary endothelial cells in vitro is consistent with the prominent vasculitis observed in infections, and provide initial molecular insights into the pathogenesis of NiV in physiologically relevant cells types.

Phenylmethimazole decreases Toll-like receptor 3 and noncanonical Wnt5a expression in pancreatic cancer and melanoma together with tumor cell growth and migration

PURPOSE

To evaluate whether (a) Wnt5a expression in pancreatic cancer and malignant melanoma cells might be associated with constitutive levels of Toll-like receptor 3 (TLR3) and/or TLR3 signaling; (b) phenylmethimazole (C10), a novel TLR signaling inhibitor, could decrease constitutive Wnt5a and TLR3 levels together with cell growth and migration; and (c) the efficacy of C10 as a potential inhibitor of pancreatic cancer and malignant melanoma cell growth in vivo.

EXPERIMENTAL DESIGN

We used a variety of molecular biology techniques including but not limited to PCR, Western blotting, and ELISA to evaluate the presence of constitutively activated TLR3/Wnt5a expression and signaling. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide-based technology and scratch assays were used to evaluate inhibition of cell growth and migration, respectively. TLR3 regulation of cell growth was confirmed using small interfering RNA technology. Nude and severe combined immunodeficient mice were implanted with human pancreatic cancer and/or melanoma cells and the effects of C10 on tumor growth were evaluated.

RESULTS

We show that constitutive TLR3 expression is associated with constitutive Wnt5a in human pancreatic cancer and malignant melanoma cell lines, that C10 can decrease constitutive TLR3/Wnt5a expression and signaling, suggesting that they are interrelated signal systems, and that C10 inhibits growth and migration in both of these cancer cell lines. We also report that C10 is effective at inhibiting human pancreatic cancer and malignant melanoma tumor growth in vivo in nude or severe combined immunodeficient mice and associate this with inhibition of signal transducers and activators of transcription 3 activation.

CONCLUSIONS

C10 may have potential therapeutic applicability in pancreatic cancer and malignant melanoma.

Innate resistance to flavivirus infections and the functions of 2'-5' oligoadenylate synthetases

Mouse susceptibility to experimental infections with flaviviruses is significantly influenced by a cluster of genes on chromosome 5 encoding a family of proteins with enzymatic properties, the 2'-5' oligoadenylate synthetases (OAS). Positional cloning of the locus in question has revealed that susceptibility of laboratory inbred strains to this class of virus is associated with a nonsense mutation in the gene encoding the OAS1B isoform. Analysis of the molecular structure of the cluster in different mammalian species including human indicates that the cluster is extremely polymorphic with a highly variable number of genes and pseudogenes whose functions are not yet completely established. Although still preliminary, a few recent observations also substantiate a possible role for OAS1 in human susceptibility to viral infections (West Nile virus, SARS, etc.) and its possible involvement in some other diseases such as type 1 diabetes and multiple sclerosis. Finally, convergent observations indicate that the molecules encoded by the 2 '-5' OAS cluster might be involved in other fundamental cellular functions such as cell growth and differentiation, gene regulation, and apoptosis.

CXCL10/CXCR3-mediated responses promote immunity to respiratory syncytial virus infection by augmenting dendritic cell and CD8(+) T cell efficacy

The induction of inflammatory cytokines during respiratory viral infections contributes to both disease pathogenesis and resolution. The present studies investigated the role of the chemokine CXCL10 and its specific receptor, CXCR3, in the host response to pulmonary respiratory syncytial virus (RSV) infection. Antibody-mediated neutralization of CXCL10 resulted in a significant increase in disease pathogenesis, including airway hyperresponsiveness (AHR), mucus gene expression, and impaired viral clearance. When the pulmonary cytokine levels were examined, only type I IFN and IL-12p70 were significantly reduced. These latter observations were reflected in reduced dendritic cell (DC) numbers and DC maturation in the lungs of RSV-infected mice treated with anti-CXCL10. Neutralization of the only known receptor for CXCL10, CXCR3, resulted in similar increases in pathogenic responses. When bone marrow-derived DC were incubated with CXCL10 and RSV, an up-regulation of type I IFN was observed. In addition, T lymphocytes were also examined and a significant decrease in the number of RSV M2 peptide-specific CD8(+) T cells was identified. These findings highlight a previously unappreciated role for the CXCL10:CXCR3 signaling axis in RSV-infected animals by recruiting virus-specific T cells into the lung and promoting viral clearance.

CXCL10/IP-10: a missing link between inflammation and anti-angiogenesis in preeclampsia?

OBJECTIVE

Interferon (IFN)-gamma inducible protein, CXCL10/IP-10, is a member of the CXC chemokine family with pro-inflammatory and anti-angiogenic properties. This chemokine has been proposed to be a key link between inflammation and angiogenesis. The aim of this study was to determine whether preeclampsia and delivery of a small for gestational age (SGA) neonate are associated with changes in maternal serum concentration of CXCL10/IP-10.

STUDY DESIGN

This cross-sectional study included patients in the following groups: (1) non-pregnant women (N = 49); (2) women with normal pregnancies (N = 89); (3) patients with preeclampsia (N = 100); and (4) patients who delivered an SGA neonate (N = 78). SGA was defined as birth weight below the 10th percentile. Maternal serum concentrations of CXCL10/IP-10 were measured by sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) Patients with normal pregnancies had a significantly higher median serum concentration of CXCL10/IP-10 than non-pregnant women (median 116.1 pg/mL, range 40.7-1314.3 vs. median 90.3 pg/mL, range 49.2-214.7, respectively; p = 0.002); (2) no significant correlation was found between maternal serum concentration of CXCL10/IP-10 and gestational age (between 19 and 38 weeks); (3) there were no differences in median serum CXCL10/IP-10 concentrations between patients who delivered an SGA neonate and those with normal pregnancies (median 122.4 pg/mL, range 37.3-693.5 vs. median 116.1 pg/mL, range 40.7-1314.3, respectively; p > 0.05); (4) patients with preeclampsia had a higher median serum concentration of CXCL10/IP-10 than normal pregnant women (median 156.4 pg/mL, range 47.4-645.9 vs. median 116.1 pg/mL, range 40.7-1314.3, respectively; p < 0.05); (5) patients with preeclampsia had a higher median concentration of CXCL10/IP-10 than those who delivered an SGA neonate (median 156.4 pg/mL, range 47.4-645.9 vs. median 122.4 pg/mL, range 37.3-693.5, respectively; p < 0.05).

CONCLUSIONS

Patients with preeclampsia have significantly higher serum concentrations of CXCL10/IP-10 than both normal pregnant women and mothers who have SGA neonates. These results are likely to reflect an anti-angiogenic state as well as an enhanced systemic inflammatory response in patients with preeclampsia. Alternatively, since preeclampsia and SGA share several mechanisms of disease, it is possible that a higher concentration of this chemokine may contribute to the clinical presentation of preeclampsia in patients with a similar intrauterine insult.

Maternal serum concentrations of the chemokine CXCL10/IP-10 are elevated in acute pyelonephritis during pregnancy

OBJECTIVE

Acute pyelonephritis is one of the most frequent medical complications of pregnancy, as well as a common cause of antepartum hospitalization. Interferon (IFN)-gamma inducible protein, CXCL10/IP-10, is a member of the CXC chemokine family with pro-inflammatory and anti-angiogenic properties. The purpose of this study was to determine whether maternal serum concentrations of CXCL10/IP-10 change in patients with acute pyelonephritis during pregnancy.

STUDY DESIGN

This cross-sectional study was conducted to determine the difference in maternal serum concentrations of CXCL10/IP-10 in pregnant women with acute pyelonephritis (N = 41) and normal pregnant women (N = 89). Pyelonephritis was defined in the presence of a positive urine culture, fever, and maternal clinical signs; blood cultures were performed in 36 cases. Maternal serum concentrations of CXCL10/IP-10 were measured by a sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) The median serum concentration of CXCL10/IP-10 in pregnant patients with pyelonephritis was significantly higher than in normal pregnant women (median 318.5 pg/mL, range 78.8-2459.2 vs. median 116.1 pg/mL, range 40.7-1314.3, respectively; p < 0.001); (2) maternal median serum concentrations of CXCL10/IP-10 did not differ significantly among patients with acute pyelonephritis with and without bacteremia (positive blood cultures: median 362.6 pg/mL, range 100.2-2459.2 vs. negative blood cultures: median 298.9 pg/mL, range 108.5-1148.7, respectively; p = 0.3).

CONCLUSIONS

Pyelonephritis in pregnant women is associated with an increased maternal serum concentration of the chemokine CXCL10/IP-10.

Transcriptional networks in plasmacytoid dendritic cells stimulated with synthetic TLR 7 agonists

Background

Plasmacytoid Dendritic Cells (pDC) comprise approximately 0.2 to 0.8% of the blood mononuclear cells and are the primary type 1 interferon (IFN), producing cells, secreting high levels of IFN in response to viral infections. Plasmacytoid dendritic cells express predominantly TLRs 7 & 9, making them responsive to ssRNA and CpG DNA. The objective of this study was to evaluate the molecular and cellular processes altered upon stimulation of pDC with synthetic TLR 7 and TLR 7/8 agonists. To this end, we evaluated changes in global gene expression upon stimulation of 99.9% pure human pDC with the TLR7 selective agonists 3M-852A, and the TLR7/8 agonist 3M-011.

Results

Global gene expression was evaluated using the Affymetrix U133A GeneChip^® and selected genes were confirmed using real time TaqMan^® RTPCR. The gene expression profiles of the two agonists were similar indicating that changes in gene expression were solely due to stimulation through TLR7. Type 1 interferons were among the highest induced genes and included IFNB and multiple IFNα subtypes, IFNα2, α5, α6, α8, α1/13, α10, α14, α16, α17, α21. A large number of chemokines and co-stimulatory molecules as well as the chemokine receptor CCR7 were increased in expression indicating maturation and change in the migratory ability of pDC. Induction of an antiviral state was shown by the expression of several IFN-inducible genes with known anti-viral activity. Further analysis of the data using the pathway analysis tool MetaCore gave insight into molecular and cellular processes impacted. The analysis revealed transcription networks that show increased expression of signaling components in TLR7 and TLR3 pathways, and the cytosolic anti-viral pathway regulated by RIG1 and MDA5, suggestive of optimization of an antiviral state targeted towards RNA viruses. The analysis also revealed increased expression of a network of genes important for protein ISGylation as well as an anti-apoptotic and pro-survival gene expression program.

Conclusion

Thus this study demonstrates that as early as 4 hr post stimulation, synthetic TLR7 agonists induce a complex transcription network responsible for activating pDC for innate anti-viral immune responses with optimized responses towards RNA viruses, increased co-stimulatory capacity, and increased survival.

High basal levels of functional toll-like receptor 3 (TLR3) and noncanonical Wnt5a are expressed in papillary thyroid cancer and are coordinately decreased by phenylmethimazole together with cell proliferation and migration

High basal levels of TLR3 and Wnt5a RNA are present in papillary thyroid carcinoma (PTC) cell lines consistent with their overexpression and colocalization in PTC cells in vivo. This is not the case in thyrocytes from normal tissue and in follicular carcinoma (FC) or anaplastic carcinoma (AC) cells or tissues. The basally expressed TLR3 are functional in PTC cells as evidenced by the ability of double-strand RNA (polyinosine-polycytidylic acid) to significantly increase the activity of transfected NF-kappaB and IFN-beta luciferase reporter genes and the levels of two end products of TLR3 signaling, IFN-beta and CXCL10. Phenylmethimazole (C10), a drug that decreases TLR3 expression and signaling in FRTL-5 thyrocytes, decreases TLR3 levels and signaling in PTC cells in a concentration-dependent manner. C10 also decreased Wnt5a RNA levels coordinate with decreases in TLR3. E-cadherin RNA levels, whose suppression may be associated with high Wnt5a, increased with C10 treatment. C10 simultaneously decreased PTC proliferation and cell migration but had no effect on the growth and migration of FC, AC, or FRTL-5 cells. C10 decreases high basal phosphorylation of Tyr705 and Ser727 on Stat3 in PTC cells and inhibits IL-6-induced Stat3 phosphorylation. IL-6-induced Stat3 phosphorylation is important both in up-regulating Wnt5a levels and in cell growth. In sum, high Wnt5a levels in PTC cells may be related to high TLR3 levels and signaling; and the ability of phenylmethimazole (C10) to decrease growth and migration of PTC cells may be related to its suppressive effect on TLR3 and Wnt5a signaling, particularly Stat3 activation.

REFINEMENT: A search framework for the identification of interferon-responsive elements in DNA sequences – a case study with ISRE and GAS

Interferons (IFN) are a family of pleiotropic secreted proteins that play a key role in mediating antiviral and apoptotic responses, and in immune modulation. Interferons induce a large number of genes through activating the janus tyrosine kinase (JAK)-signal transducers and activators of transcription proteins (STAT) pathway, and the binding of transcription factors to upstream regions of the inducible genes (interferon-stimulated gene, ISG) at specific DNA regulatory elements known as interferon-stimulated response element (ISRE) and gamma-activated sequence (GAS). We have previously performed DNA micro-arrays on peripheral blood mononuclear cells (PBMC) treated with interferon-alpha in culture and showed that approximately 700 genes are significantly modulated (P < or = 0.001). In order to search for ISRE and GAS we have developed a framework called regulatory element finding with iteration and effective model refinement (REFINEMENT) using an existing program (HMMER) and a standard discriminating scoring technique. Although REFINEMENT uses existing programs, our framework itself is novel as it effectively discriminates occurrences using an iterative model refinement technique. REFINEMENT has detected either ISRE or GAS sequence in all of the genes shown to be induced at a P-value < or = 0.001. There were far more functional occurrences in ISRE than in GAS, suggesting that ISRE plays a greater role in response to interferon-alpha than GAS sequences. This method can be used to identify such sequences in any set of genes. REFINEMENT is non-commercial and is accessible at .

Activation of innate defense against a paramyxovirus is mediated by RIG-I and TLR7 and TLR8 in a cell-type-specific manner

Recognition of pathogens by the innate immune system is mediated by pattern recognition receptors (PRRs), which recognize specific molecular structures of the infectious agents and subsequently trigger expression of genes involved in host defense. Toll-like receptors (TLRs) represent a well-characterized class of membrane-bound PRRs, and the RNA helicase retinoic acid inducible gene I (RIG-I) has recently been described as a novel cytoplasmic PRR recognizing double-stranded RNA (dsRNA). Here we show that activation of signal transduction and induction of cytokine expression by the paramyxovirus Sendai virus is dependent on virus replication and involves PRRs in a cell-type-dependent manner. While nonimmune cells relied entirely on recognition of dsRNA through RIG-I for activation of an antiviral response, myeloid cells utilized both the single-stranded RNA sensing TLR7 and TLR8 and dsRNA-dependent mechanisms independent of RIG-I, TLR3, and dsRNA-activated protein kinase R to trigger this response. Therefore, there appears to be a large degree of cell-type specificity in the mechanisms used by the host to recognize infecting viruses.

15-Deoxy-Δ12,14-Prostaglandin J2 Inhibits IFN-Inducible Protein 10/CXC Chemokine Ligand 10 Expression in Human Microglia: Mechanisms and Implications

Regulation of cytokine and chemokine expression in microglia may have implications for CNS inflammatory disorders. In this study we examined the role of the cyclopentenone PG 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) in microglial inflammatory activation in primary cultures of human fetal microglia. 15d-PGJ(2) potently inhibited the expression of microglial cytokines (IL-1, TNF-alpha, and IL-6). We found that 15d-PGJ(2) had differential effects on the expression of two alpha-chemokines; whereas the Glu-Lys-Arg (ELR)(-) chemokine IFN-inducible protein-10/CXCL10 was inhibited, the ELR(+) chemokine IL-8/CXCL8 was not inhibited. These findings were shown in primary human microglia and the human monocytic cells line THP-1 cells, using diverse cell stimuli such as bacterial endotoxin, proinflammatory cytokines (IL-1 and TNF-alpha), IFN-beta, and HIV-1. Furthermore, IL-8/CXCL8 expression was induced by 15d-PGJ(2) alone or in combination with TNF-alpha or HIV-1. Combined results from EMSA, Western blot analysis, and immunocytochemistry showed that 15d-PGJ(2) inhibited NF-kappaB, Stat1, and p38 MAPK activation in microglia. Adenoviral transduction of super-repressor IkappaBalpha, dominant negative MKK6, and dominant negative Ras demonstrated that NF-kappaB and p38 MAPK were involved in LPS-induced IFN-inducible protein 10/CXCL10 production. Interestingly, although LPS-induced IL-8/CXCL8 was dependent on NF-kappaB, the baseline or 15d-PGJ(2)-mediated IL-8/CXCL8 production was NF-kappaB independent. Our results demonstrate that 15d-PGJ(2) has opposing effects on the expression of two alpha-chemokines. These data may have implications for CNS inflammatory diseases.

15-Deoxy-Δ (12,14)-PGJ2 inhibits astrocyte IL-1 signaling: inhibition of NF-κB and MAP kinase pathways and suppression of cytokine and chemokine expression

We studied the role of 15-deoxy-delta (12,14)-PGJ2 (15d-PGJ2), a macrophage inhibitor with reported therapeutic effects on experimental allergic encephalomyelitis, in human astrocyte activation in vitro. 15d-PGJ2 inhibited a broad range of astrocyte inflammatory gene expression induced by IL-1, including cytokines (TNFalpha and IL-6), chemokines (RANTES/CCL5 and IP-10/CXCL10) and inducible nitric oxide synthase. 15d-PGJ2 inhibited transactivation of NF-kappaB-dependent promoters, as well as p38 and JNK MAPK phosphorylation induced by IL-1, while having no inhibitory effect on IFN-induced Stat signaling pathways. Our results demonstrating 15d-PGJ2-mediated astrocyte deactivation through inhibition of NF-kappaB are similar to those described for macrophages, and add astrocytes as additional targets for this prostaglandin (PG).

Chronic ethanol inhibits CXC chemokine ligand 10 production in human A172 astroglia and astroglial-mediated leukocyte chemotaxis

Astroglia are the most prevalent cell type in the human central nervous system (CNS) and perform important roles in normal tissue homeostasis, during pathological events and following trauma. Astroglial-derived chemokines have important neurotrophic effects and are important to CNS immunocompetence and response to injury, in part, due to their direct role in leukocyte and microglial cell recruitment. However, while ethanol is known to induce CNS pathologies and to be peripherally immunosuppressive, ethanol effects on chemokine expression in human astroglia are essentially unknown. We have demonstrated that chemotaxis of human U937 leukocytic cells, across a 0.5 microm pore polycarbonate transmembrane insert, is induced in response to culture media collected from 10 microg/ml lipopolysaccharide (LPS) + 10 ng/ml interleukin (IL)-1beta-stimulated A172 human astroglia cells. The involvement of the chemokine CXCL10 (also known as interferon-gamma inducible protein or IP-10) in astroglial-induced chemotaxis of U937 cells has been indicated, as chemotaxis can be reduced by an anti-CXCL10 neutralizing antibody. Interestingly, chemotaxis of U937 cells, in response to astroglial-exposed media, is reduced when astroglia are chronically (9 days) exposed to 50 mM ethanol before stimulation with LPS + IL-1beta. Furthermore, we observed that LPS + IL-1beta-stimulated CXCL10 production is inhibited in human A172 astroglia exposed to chronic 50 mM ethanol. Thus, alterations in astroglial CXCL10 expression may disrupt CNS immunocompetence and play an important role in ethanol-induced CNS pathologies.

Structural and functional genomics and evolutionary relationships in the cluster of genes encoding murine 2′,5′-oligoadenylate synthetases

2',5'-Oligoadenylate synthetases (2',5'-OASs) are interferon-inducible enzymes. Some of these proteins play an important role in cellular physiology, in particular, in the innate defense mechanisms against RNA virus infections. In the present publication we report the complete genomic structure of the cluster of genes encoding mouse 2',5'-OAS, with all its transcription units, their predicted functions, and their evolutionary relationships. We found that mouse Oas2/Oas3 genes have a genomic structure similar to that of human OAS2/OAS3, while the mouse equivalent of human OAS1 is composed of eight (Oas1a to Oas1h) tandemly arranged transcription units. For all these eight genes a specific inducible promoter controls transcription. The possible functions of this family of proteins are discussed.

Expression and function of chemokines during viral infections: from molecular mechanisms to in vivo function

Recruitment and activation of leukocytes are important for elimination of microbes, including viruses, from infected areas. Chemokines constitute a group of bioactive peptides that regulate leukocyte migration and also contribute to activation of these cells. Chemokines are essential mediators of inflammation and important for control of viral infections. The profile of chemokine expression contributes to shaping the immune response during viral infection, whereas viral subversion of the chemokine system allows the virus to evade antiviral activities of the host. In this review, we discuss the role of chemokines in host-defense against virus infections, and we also look deeper into the virus-cell interactions that trigger chemokine expression as well as the cellular signaling cascades involved.

Infection of mouse neurones by West Nile virus is modulated by the interferon-inducible 2'-5' oligoadenylate synthetase 1b protein

Over the past 7 years, West Nile zoonosis has been an emerging concern for public health in Europe, Middle East and more recently in North America. West Nile virus causes epidemic outbreaks in humans and infected patients may exhibit severe neurological symptoms. Because susceptibility and sensitivity to West Nile virus infections may depend on host genetic factors, a mouse model has been established to investigate the genetic determinism of host susceptibility to West Nile virus. A nonsense mutation in gene encoding the 1b isoform of the 2'-5'oligoadenylate synthetase (OAS1b) was constantly associated with the susceptibility of mouse strains to experimental West Nile virus infection. Oligoadenylate synthetase are interferon-inducible proteins playing a role in the endogeneous antiviral pathway. It was of interest to establish whether interferon-alpha and OAS 1B were sufficient to mediate resistance to West Nile virus infection. In the present study, we showed that interferon-alpha had the ability to modulate West Nile virus infection in mouse. In vitro, interferon-alpha protected mouse neuroblastoma cells against West Nile virus infection if cells have been pretreated with the cytokine for several hours. As a consequence of the presence of a stop codon, the Oas1b gene of the susceptible mice encodes a truncated and presumably inactive form, while resistant mice have a normal copy of the gene. Stable mouse neuroblastoma cell clones overexpressing mutant or wild-type OAS 1B were established. Replication of West Nile virus was less efficient in cells that produce the normal copy of OAS 1B as compared to those expressing the truncated form. Our data illustrate the notion that interferon-alpha and Oas genes may be critical for West Nile virus pathogenesis.

CXCL10 production from cytomegalovirus-stimulated microglia is regulated by both human and viral interleukin-10

Glial cells orchestrate immunocyte recruitment to focal areas of viral infection within the brain and synchronize immune cell functions through a regulated network of cytokines and chemokines. Since recruitment of T lymphocytes plays a critical role in resolving cytomegalovirus (CMV) infection, we investigated the production of a T-cell chemoattractant, CXCL10 (gamma interferon-inducible protein 10) in response to viral infection of human glial cells. Infection with CMV was found to elicit the production of CXCL10 from primary microglial cells but not from astrocytes. This CXCL10 expression was not dependent on secondary protein synthesis but did require the phosphorylation of p38 mitogen-activated protein (MAP) kinase. In addition, migration of activated lymphocytes toward supernatants from CMV-stimulated microglial cells was partially suppressed by anti-CXCL10 antibodies. Since regulation of central nervous system inflammation is essential to allow viral clearance without immunopathology, microglial cells were then treated with anti-inflammatory cytokines. CMV-induced CXCL10 production from microglial cells was suppressed following treatment with interleukin-10 (IL-10) and IL-4 but not following treatment with transforming growth factor beta. The IL-10-mediated inhibition of CXCL10 production was associated with decreased CMV-induced NF-kappa B activation but not decreased p38 MAP kinase phosphorylation. Finally, CMV infection of fully permissive astrocytes resulted in mRNA expression for the viral homologue to human IL-10 (i.e., cmvIL-10 [UL111a]) in its spliced form and conditioned medium from CMV-infected astrocytes inhibited virus-induced CXCL10 production from microglial cells through the IL-10 receptor. These findings present yet another mechanism through which CMV may subvert host immune responses.

Transcription factor IRF-1 in kidney transplants mediates resistance to graft necrosis during rejection

In many circumstances kidney transplants remain viable despite extensive inflammation, permitting rejection episodes to be reversed. The mechanisms by which the kidney resists host effector mechanisms are not known. In mouse kidney transplants, resistance requires interferon-gamma (IFN-gamma), which acts on the graft to protect the graft from necrosis during the first days of rejection as well as inducing major histocompatibility complex (MHC) expression. Because some effects of IFN-gamma are mediated by transcription factor IRF-1, the role of IRF-1 in the donor tissue early phases of rejection of mouse kidney allografts was studied. H-2(b) kidneys were transplanted from mice with wild-type IRF-1 genes (WT) or mice with disrupted IRF-1 genes (IRF-1KO) into CBA (H-2(k)) recipients. At day 5 and day 7, IRF-1KO and WT kidneys were functioning despite typical rejection pathology: interstitial infiltration and tubulitis. However, function deteriorated rapidly in rejecting IRF-1KO allografts, associated with widespread epithelial necrosis, peritubular capillary congestion, glomerulitis, and fibrin thrombi in small veins by day 7. At day 21, WT kidneys were viable despite severe tubulitis and arteritis, whereas IRF-1KO kidneys showed massive necrosis of the epithelium despite patent large vessels. Compared with WT kidneys, rejecting IRF-1KO kidneys showed less induction of donor MHC yet had similar mRNA levels of perforin, granzyme B, and Fas ligand and evoked host alloantibody responses. Thus in rejecting kidney transplants, IRF-1 in the graft mediates MHC induction, but it also mediates resistance to necrosis, an effect that could be crucial to permit success in interventions against rejection.

Production of the chemokines monocyte chemotactic protein-1, regulated on activation normal T cell expressed and secreted protein, growth-related oncogene, and interferon-gamma-inducible protein-10 is induced by the Sendai virus in human and rat testicular cells

Several viruses infect the testis, inducing inflammation, which may lead to infertility. In this study we investigated the production in rat and human testicular cells exposed to the Sendai virus of several chemokines that play a major role in inflammatory processes. Exposure of rat testicular macrophages and Sertoli, Leydig, and peritubular cells to the Sendai virus led to the production of mRNA and protein for monocyte chemotactic protein-1 (MCP-1), regulated on activation normal T cell expressed and secreted protein, growth-related oncogene-alpha, and interferon-gamma-inducible protein-10. In rat peritubular cells exposed to the Sendai virus, MCP-1 production was time and dose dependent. In contrast, rat germ cells did not produce these chemokines. Chemokine synthesis was detected in human Leydig cells exposed to the Sendai virus, but not in human total germ cells, suggesting that rats and humans display similar responses in terms of chemokine production. MCP-1, regulated on activation normal T cell expressed and secreted protein, growth-related oncogene-alpha, and interferon-gamma-inducible protein-10 have been reported to be chemoattractants for a large variety of leukocytes. The ability of the Sendai virus to induce chemokine production in somatic cells (mostly peritubular and Leydig cells) may therefore increase the recruitment of leukocytes to sites of infection.

Chemokine expression in the central nervous system of mice with a viral disease resembling multiple sclerosis: roles of CD4+ and CD8+ T cells and viral persistence

During the first 45 days after intracerebral infection with Theiler's murine encephalomyelitis virus (TMEV), the levels of mRNAs encoding chemokines MCP-1/CCL2, RANTES/CCL5, and IP-10/CXCL10 in the central nervous system (CNS) are closely related to the sites of virus gene expression and tissue inflammation. In the present study, these chemokines were monitored during the latter 135 days of a 6-month course of TMEV-induced disease in susceptible (PLJ) or resistant (C57BL/6) mice that possessed or lacked either CD4+ or CD8+ T cells. These data were additionally correlated to mouse genotype, virus persistence in the CNS, antiviral antibody titers, mortality, and the severity of neurological disease. Surprisingly, the major determinant of chemokine expression was virus persistence: the factors of susceptible or resistant genotype, severity of neuropathology, and presence or absence of regulatory T cells exerted minimal effects. Our observations indicated that chemokine expression in the CNS in this chronic viral disorder was intrinsic to the CNS innate immune response to infection and was not governed by elements of the adaptive immune system.

Pulmonary inflammation induced by Pseudomonas aeruginosa lipopolysaccharide, phospholipase C, and exotoxin A: role of interferon regulatory factor 1

Chronic pulmonary infection with Pseudomonas aeruginosa is common in cystic fibrosis (CF) patients. P. aeruginosa lipopolysaccharide (LPS), phosholipase C (PLC), and exotoxin A (ETA) were evaluated for their ability to induce pulmonary inflammation in mice following intranasal inoculation. Both LPS and PLC induced high levels of tumor necrosis factor alpha (TNF-alpha), interleukin 1 beta (IL-1 beta-6, gamma interferon (IFN-gamma), MIP-1 alpha MIP-2 in the lungs but did not affect IL-18 levels. ETA did not induce TNF-alpha and was a weak inducer of IL-1 beta, IL-6, macrophage inflammatory protein 1 alpha (MIP-1 alpha), and MIP-2. Remarkably, ETA reduced constitutive lung IL-18 levels. LPS was the only factor inducing IFN-gamma. LPS, PLC, and ETA all induced cell infiltration in the lungs. The role of interferon regulatory factor-1 (IRF-1) in pulmonary inflammation induced by LPS, PLC, and ETA was evaluated. When inoculated with LPS, IRF-1 gene knockout (IRF-1 KO) mice produced lower levels of TNF-alpha, IL-1 beta, and IFN-gamma than did wild-type (WT) mice. Similarly, a milder effect of ETA on IL-1 beta and IL-18 was observed for IRF-1 KO than for WT mice. In contrast, the cytokine response to PLC did not differ between WT and IRF-1 KO mice. Accordingly, LPS and ETA, but not PLC, induced expression of IRF-1 mRNA. IRF-1 deficiency had no effect on MIP-1 alpha and MIP-2 levels and on cell infiltration induced by LPS, PLC, or ETA. Flow cytometric evaluation of lung mononuclear cells revealed strongly reduced percentages of CD8(+) and NK cells in IRF-1 KO mice compared to percentages observed for WT mice. These data indicate that different virulence factors from P. aeruginosa induce pulmonary inflammation in vivo and that IRF-1 is involved in some of the cytokine responses to LPS and ETA.

The role of IRF-4 in transcriptional regulation

Gene expression is a tightly regulated process involving multiple levels of control spanning histone acetylation to protein turnover. One of the first events in this cascade is transcription, which itself is a multistep process involving protein-protein interaction and macromolecular assembly. Here we review the role of the interferon (IFN) regulatory factor (IRF) transcription factor family member IRF-4 in transcriptional regulation. IRF-4 was initially characterized in lymphocytes and was shown to function as both a transcriptional repressor and activator. More recently, IRF-4 expression and function have been reported in macrophages. The ability of IRF-4 to serve as both a transcriptional activator and repressor is determined, in part, by binding to distinct DNA-binding motifs and through interaction with various additional transcription factors, most notably with the Ets family member PU.1. The details governing these functional differences are the focus of this review. Importantly, the role of posttranslational modification and nuclear translocation of IRF-4 in transcriptional regulation are addressed. Several possible paradigms of transcriptional regulation by IRF-4 are proposed, where these paradigms may describe regulatory mechanisms common to many distinct transcription factor families.

Lipopolysaccharide stimulates the MyD88-independent pathway and results in activation of IFN-regulatory factor 3 and the expression of a subset of lipopolysaccharide-inducible genes

Bacterial lipopolysaccharide (LPS) triggers innate immune responses through Toll-like receptor (TLR) 4, a member of the TLR family that participates in pathogen recognition. TLRs recruit a cytoplasmic protein, MyD88, upon pathogen recognition, mediating its function for immune responses. Two major pathways for LPS have been suggested in recent studies, which are referred to as MyD88-dependent and -independent pathways. We report in this study the characterization of the MyD88-independent pathway via TLR4. MyD88-deficient cells failed to produce inflammatory cytokines in response to LPS, whereas they responded to LPS by activating IFN-regulatory factor 3 as well as inducing the genes containing IFN-stimulated regulatory elements such as IP-10. In contrast, a lipopeptide that activates TLR2 had no ability to activate IFN-regulatory factor 3. The MyD88-independent pathway was also activated in cells lacking both MyD88 and TNFR-associated factor 6. Thus, TLR4 signaling is composed of at least two distinct pathways, a MyD88-dependent pathway that is critical to the induction of inflammatory cytokines and a MyD88/TNFR-associated factor 6-independent pathway that regulates induction of IP-10.

Role for p53 in gene induction by double-stranded RNA

Cross talk between p53 and interferon-regulated pathways is implicated in the induction of gene expression by biologic and genotoxic stresses. We demonstrate that the interferon-stimulated gene ISG15 is induced by p53 and that p53 is required for optimal gene induction by double-stranded RNA (dsRNA), but not interferon. Interestingly, virus induces ISG15 in the absence of p53, suggesting that virus and dsRNA employ distinct signaling pathways.

Hantavirus infection induces the expression of RANTES and IP-10 without causing increased permeability in human lung microvascular endothelial cells

Sin Nombre virus (SNV) and Hantaan virus (HTN) infect endothelial cells and are associated with different patterns of increased vascular permeability during human disease. It is thought that such patterns of increased vascular permeability are a consequence of endothelial activation and subsequent dysfunction mediated by differential immune responses to hantavirus infection. In this study, the ability of hantavirus to directly induce activation of human lung microvascular endothelial cells (HMVEC-Ls) was examined. No virus-specific modulation in the constitutive or cytokine-induced expression of cellular adhesion molecules (CD40, CD54, CD61, CD62E, CD62P, CD106, and major histocompatibility complex classes I and II) or in cytokines and chemokines (eotaxin, tumor necrosis factor alpha, interleukin 1beta [IL-1beta], IL-6, IL-8, MCP-1, MIP-1alpha, and MIP-1beta) was detected at either the protein or message level in hantavirus-infected HMVEC-Ls. Furthermore, no virus-specific enhancement of paracellular or transcellular permeability or changes in the organization and distribution of endothelial intercellular junctional proteins was observed. However, infection with either HTN or SNV resulted in detectable levels of the chemokines RANTES and IP-10 (the 10-kDa interferon-inducible protein) in HMVEC-Ls within 72 h and was associated with nuclear translocation of interferon regulatory factor 3 (IRF-3) and IRF-7. Gamma interferon (IFN-gamma)-induced expression of RANTES and IP-10 could also be detected in uninfected HMVEC-Ls and was associated with nuclear translocation of IRF-1 and IRF-3. Treatment of hantavirus-infected HMVEC-Ls with IFN-gamma for 24 h resulted in a synergistic enhancement in the expression of both RANTES and IP-10 and was associated with nuclear translocation of IRF-1, IRF-3, IRF-7, and NF-kappaB p65. These results reveal a possible mechanism by which hantavirus infection and a TH1 immune response can cooperate to synergistically enhance chemokine expression by HMVEC-Ls and trigger immune-mediated increases in vascular permeability.

Influenza A and sendai viruses induce differential chemokine gene expression and transcription factor activation in human macrophages

Chemokines regulate leukocyte traffic and extravasation into the site of inflammation. Here we show that influenza A- or Sendai virus-infected human macrophages produce MIP-1alpha, MIP-1beta, RANTES, MCP-1, MCP-3, MIP-3alpha, IP-10, and IL-8, whereas no upregulation of MIP-3beta, eotaxin, or MDC production was detected. Influenza A virus was a better inducer of MCP-1 and MCP-3 production than Sendai virus, whereas MIP-1alpha, MIP-1beta, RANTES, MIP-3alpha, and IL-8 were induced preferentially by Sendai virus. Infection in the presence of protein synthesis inhibitor indicated that ongoing protein synthesis was required for influenza A virus-induced expression of MCP-1, MCP-3, and IP-10 genes, whereas Sendai virus-induced chemokine mRNA expression took place in the absence of de novo protein synthesis. Neutralization of virus-induced IFN-alpha/beta resulted in downregulation of virus-induced IP-10, MCP-1, and MCP-3 mRNA expression. IFN-alpha or IFN-gamma were found to directly enhance MCP-1, MCP-3, and IP-10 mRNA expression. Both influenza A and Sendai viruses similarly activated transcription factor NF-kappaB. In contrast to NF-kappaB, IRFs and STATs, the other transcription factors involved in the regulation of chemokine gene expression, were differentially activated by these viruses. Influenza A virus more efficiently activated ISGF3 complex formation and Stat1 DNA-binding compared to Sendai virus, which in turn was a more potent activator of IRF-1. Our results show that during viral infections macrophages predominantly produce monocyte and Th1 cell attracting chemokines. Furthermore, virus-induced IFN-alpha/beta enhanced chemokine gene expression in macrophages emphasizing the role of IFN-alpha/beta in the development of Th1 immune responses.

Regulation of RANTES chemokine gene expression requires cooperativity between NF-kappa B and IFN-regulatory factor transcription factors

Virus infection of host cells activates a set of cellular genes, including cytokines, IFNs, and chemokines, involved in antiviral defense and immune activation. Previous studies demonstrated that virus-induced transcriptional activation of a member of the human CC-chemokine RANTES required activation of the latent transcription factors IFN-regulatory factor (IRF)-3 and NF-kappa B via posttranslational phosphorylation. In the present study, we further characterized the regulatory control of RANTES transcription during virus infection using in vivo genomic footprinting analyses. IRF-3, the related IRF-7, and NF-kappa B are identified as important in vivo binding factors required for the cooperative induction of RANTES transcription after virus infection. Using fibroblastic or myeloid cells, we demonstrate that the kinetics and strength of RANTES virus-induced transcription are highly dependent on the preexistence of IRFs and NF-kappa B. Use of dominant negative mutants of either I kappa B-alpha or IRF-3 demonstrate that disruption of either pathway dramatically abolishes the ability of the other to bind and activate RANTES expression. Furthermore, coexpression of IRF-3, IRF-7, and p65/p50 leads to synergistic activation of RANTES promoter transcription. These studies reveal a model of virus-mediated RANTES promoter activation that involves cooperative synergism between IRF-3/IRF-7 and NF-kappa B factors.

Secretion of CXC chemokine IP-10 by peripheral blood mononuclear cells from healthy donors and breast cancer patients stimulated with HER-2 peptides

CXC chemokines play an important role in recruitment of T cells to the site of activation and regulation of angiogenesis. CXC chemokines are secreted by T cells stimulated with cytokines or by established cytotoxic T lymphocyte (CTL) lines at recognition of conventional antigen (Ag), but the activation requirements and the relationship of interferon-gamma (IFN-gamma) inducible protein (IP-10) secretion with IFN-gamma induction in lymphocytes are still unclear. We studied the induction of IP-10 from nonadherent peripheral blood mononuclear cells (PBMC) by IFN-gamma, interleukin-12 (IL-12), and the HER-2 peptide E75, which forms a CTL-defined antigen. We found that IFN-gamma alone was a weak inducer of IP-10 in these cells, whereas IL-12 was a significantly stronger inducer of IP-10. In the presence of IL-12, the tumor peptide E75 (HER-2, 369-377) was a stronger inducer of IP-10 than was IL-12 alone. E75 and its variants mutated at position 5 could also induce IP-10 in the absence of exogenous IL-12 or IFN-gamma. IP-10 induction by E75 required HLA-A2 presentation and B7-CD28 interactions and was partially inhibited by blocking of CD40-CD40L interactions. These results indicate that presentation of tumor peptides to peripheral T cells can induce a fast chemokine response, which in its early phase may be higher than the IFN-gamma response. This shows that the IP-10 response was independent of any early-phase IFN-gamma response in peripheral T cells. This may be important for understanding the regulation of the balance between chemoattractant chemokines (CC) and CXC chemokines by tumor Ag and may have implications for understanding the mechanisms of polarization of T cells and conditioning of antigen-presenting cells (APC) by tumor antigens.

Distinct patterns of stimulus-inducible chemokine mRNA accumulation in human fetal astrocytes and microglia

Interferon-gamma-inducible 10 kd protein (IP-10) is an ELR (Glu-Leu-Arg)(-) alpha chemokine with known chemotactic effects on T cells and monocytes, as well as anti-viral, anti-angiogenic, and anti-tumor effects. Previous studies have demonstrated that in cultured rat astrocytes and microglia, stimulation with LPS or virus can induce the expression of IP-10. In this study, we determined the pattern of IP-10 gene induction in primary human microglia and astrocytes by cytokines and LPS using ribonuclease protection assay. The expression of IP-10 mRNA was compared with that of other alpha (IL-8) and beta chemokines. The results showed that in human microglia, IP-10 expression was induced equally potently by LPS, IFNbeta or IFNgamma. "Proinflammatory" cytokines IL-1beta or TNFalpha also induced small amounts of IP-10 mRNA. "Anti-inflammatory" cytokines IL-4, IL-10 and TGFbeta were ineffective in inducing IP-10 in microglia. In human astrocytes, induction of IP-10 mRNA by cytokines was similar to that in microglia. LPS, however, was ineffective in inducing IP-10 in human astrocytes. The monocyte chemoattractant beta-chemokine I-309 mRNA was induced in human astrocytes and microglia by IFNbeta or IFNgamma, or by LPS in microglia, showing a tight co-regulation with IP-10 mRNA expression. In contrast to the potent induction of IP-10 and I-309 by IFNs in human glia, the ELR(+) alpha chemokine IL-8 mRNA was induced by IL-1beta and TNFalpha, and to a lesser extent by IFNbeta in microglia. IFNbeta but not IFNgamma was effective in inducing the expression of beta chemokines MIP-1alpha and MIP-1beta in human microglia, with the levels of mRNA similar to those induced by IL-1beta or TNFalpha. Neither MIP-1alpha nor MIP-1beta mRNAs were induced by any stimulation in human astrocytes. The induction of RANTES mRNA in microglia by IFNbeta, IL-1beta or TNFalpha was variable, showing no to low level expression depending on the case, whereas LPS provided a consistent inducing signal. In astrocytes, only cytokine combinations (IFN + IL-1beta) effectively induced the RANTES mRNA. These results demonstrate that distinct sets of chemokine genes are induced in human glial cells by cytokines and interferons. These results may have wide implications for inflammatory, vascular and neoplastic diseases of the CNS.

Requirements for measles virus induction of RANTES chemokine in human astrocytoma-derived U373 cells

Interferons and chemokines play a critical role in regulating the host response to viral infection. Measles virus, a member of the Paramyxoviridae family, induces RANTES expression by astrocytes. We have examined the mechanism of this induction in U373 cells derived from a human astrocytoma. RANTES was induced in a dose- and time-dependent manner by measles virus infection. Inhibition of receptor binding by the anti-CD46 antibody TRA-2.10 and of virus-membrane fusion by the tripeptide X-Phe-Phe-Gly reduced RANTES expression. Formalin-inactivated virus, which can bind but not fuse, and extensively UV-irradiated virus, which can bind and fuse, were both ineffective. Therefore, virus binding to the cellular receptor CD46 and subsequent membrane fusion were necessary, but not sufficient, to induce RANTES. UV irradiation of virus for less than 10 min proportionally inhibited viral transcription and RANTES expression. RANTES induction was decreased in infected cells treated with ribavirin, which inhibits measles virus transcription. However, RANTES mRNA was superinduced by measles virus in the presence of cycloheximide. These data suggest that partial transcription of the viral genome is sufficient and necessary for RANTES induction, whereas viral protein synthesis and replication are not required. This hypothesis was supported by the fact that RANTES was induced through transient expression of the measles virus nucleocapsid gene but not by measles genes encoding P or L proteins or by leader RNA in A549 cells. Thus, transcription of specific portions of measles virus RNA, such as the nucleocapsid gene, appears able to generate the specific signaling required to induce RANTES gene expression.