Autocrine regulation and experimental modulation of interleukin-6 expression by human pulmonary epithelial cells infected with respiratory syncytial virus

Cytokines in oncolytic virotherapy

Tumors represent a hostile environment for the effector cells of cancer immunosurveillance. Immunosuppressive receptors and soluble or membrane-bound ligands are abundantly exposed and released by malignant entities and their stromal accomplices. As a consequence, executioners of antitumor immunity inefficiently navigate across cancer tissues and fail to eliminate malignant targets. By inducing immunogenic cancer cell death, oncolytic viruses profoundly reshape the tumor microenvironment. They trigger the local spread of danger signals and tumor-associated (as well as viral) antigens, thus attracting antigen-presenting cells, promoting the activation and expansion of lymphocytic populations, facilitating their infiltration in the tumor bed, and reinvigorating cytotoxic immune activity. The present review recapitulates key chemokines, growth factors and other cytokines that orchestrate this ballet of antitumoral leukocytes upon oncolytic virotherapy.

Airway Epithelial Derived Cytokines and Chemokines and Their Role in the Immune Response to Respiratory Syncytial Virus Infection

The airway epithelium is the primary target of respiratory syncytial virus infection. It is an important component of the antiviral immune response. It contributes to the recruitment and activation of innate immune cells from the periphery through the secretion of cytokines and chemokines. This paper provides a broad review of the cytokines and chemokines secreted from human airway epithelial cell models during respiratory syncytial virus (RSV) infection based on a comprehensive literature review. Epithelium-derived chemokines constitute most inflammatory mediators secreted from the epithelium during RSV infection. This suggests chemo-attraction of peripheral immune cells, such as monocytes, neutrophils, eosinophils, and natural killer cells as a key function of the epithelium. The reports of epithelium-derived cytokines are limited. Recent research has started to identify novel cytokines, the functions of which remain largely unknown in the wider context of the RSV immune response. It is argued that the correct choice of in vitro models used for investigations of epithelial immune functions during RSV infection could facilitate greater progress in this field.

Early IL-6 signalling promotes IL-27 dependent maturation of regulatory T cells in the lungs and resolution of viral immunopathology

Interleukin-6 is a pleiotropic, pro-inflammatory cytokine that can promote both innate and adaptive immune responses. In humans with respiratory virus infections, such as Respiratory Syncytial Virus (RSV), elevated concentrations of IL-6 are associated with more severe disease. In contrast the polymorphisms in the Il6 promoter which favour lower IL-6 production are associated with increased risk of both RSV and Rhinovirus infections. To determine the precise contribution of IL-6 to protection and pathology we used murine models of respiratory virus infection. RSV infection resulted in increased IL-6 production both in the airways and systemically which remained heightened for at least 2 weeks. IL-6 depletion early, but not late, during RSV or Influenza A virus infection resulted in significantly increased disease associated with an influx of virus specific T_H1 and cytotoxic CD8⁺ T cells, whilst not affecting viral clearance. IL-6 acted by driving production of the immunoregulatory cytokine IL-27 by macrophages and monocytes, which in turn promoted the local maturation of regulatory T cells. Concordantly IL-27 was necessary to regulate T_H1 responses in the lungs, and sufficient to limit RSV induced disease. Overall we found that during respiratory virus infection the prototypic inflammatory cytokine IL-6 is a critical anti-inflammatory regulator of viral induced immunopathology in the respiratory tract through its induction of IL-27.

In clearing a respiratory virus, the host must strike a careful balance between the need to clear the infection and the potential of the immune response to damage the delicate structure of the lungs. Here we show that Interleukin-6, a soluble mediator commonly associated with inflammation and seen in humans with severe respiratory infection, is actually critical in promoting the resolution of the host response to respiratory virus infection and limiting disease. We have found that the early production of IL-6 after infection promotes the production of the regulatory mediator Interleukin-27 by lung resident immune cells, which in turn drives suppression of otherwise damaging inflammation. Removal of either IL-6 or IL-27 enhances disease during viral infection, while restoration of IL-27 is sufficient to allow faster recovery. Thus we have identified a novel immunological network within the respiratory tract which accelerates recovery after respiratory virus infection.

Activation of Proinflammatory Responses in Cells of the Airway Mucosa by Particulate Matter: Oxidant- and Non-Oxidant-Mediated Triggering Mechanisms

Inflammation is considered to play a central role in a diverse range of disease outcomes associated with exposure to various types of inhalable particulates. The initial mechanisms through which particles trigger cellular responses leading to activation of inflammatory responses are crucial to clarify in order to understand what physico-chemical characteristics govern the inflammogenic activity of particulate matter and why some particles are more harmful than others. Recent research suggests that molecular triggering mechanisms involved in activation of proinflammatory genes and onset of inflammatory reactions by particles or soluble particle components can be categorized into direct formation of reactive oxygen species (ROS) with subsequent oxidative stress, interaction with the lipid layer of cellular membranes, activation of cell surface receptors, and direct interactions with intracellular molecular targets. The present review focuses on the immediate effects and responses in cells exposed to particles and central down-stream signaling mechanisms involved in regulation of proinflammatory genes, with special emphasis on the role of oxidant and non-oxidant triggering mechanisms. Importantly, ROS act as a central second-messenger in a variety of signaling pathways. Even non-oxidant mediated triggering mechanisms are therefore also likely to activate downstream redox-regulated events.

Ginseng protects against respiratory syncytial virus by modulating multiple immune cells and inhibiting viral replication

Ginseng has been used in humans for thousands of years but its effects on viral infection have not been well understood. We investigated the effects of red ginseng extract (RGE) on respiratory syncytial virus (RSV) infection using in vitro cell culture and in vivo mouse models. RGE partially protected human epithelial (HEp2) cells from RSV-induced cell death and viral replication. In addition, RGE significantly inhibited the production of RSV-induced pro-inflammatory cytokine (TNF-α) in murine dendritic and macrophage-like cells. More importantly, RGE intranasal pre-treatment prevented loss of mouse body weight after RSV infection. RGE treatment improved lung viral clearance and enhanced the production of interferon (IFN-γ) in bronchoalveolar lavage cells upon RSV infection of mice. Analysis of cellular phenotypes in bronchoalveolar lavage fluids showed that RGE treatment increased the populations of CD8⁺ T cells and CD11c⁺ dendritic cells upon RSV infection of mice. Taken together, these results provide evidence that ginseng has protective effects against RSV infection through multiple mechanisms, which include improving cell survival, partial inhibition of viral replication and modulation of cytokine production and types of immune cells migrating into the lung.

Antiviral activity of ginseng extract against respiratory syncytial virus infection

Panax ginseng has been known to have a number of immuno-modulatory effects. In this study, we investigated whether Panax Korean red ginseng extract (KRGE) has in vitro and in vivo antiviral effects on respiratory syncytial virus (RSV) infection. KRGE improved the survival of human lung epithelial cells against RSV infection and inhibited RSV replication. In addition, KRGE treatment suppressed the expression of RSV-induced inflammatory cytokine genes (IL-6 and IL-8) and the formation of reactive oxygen species in epithelial cell cultures. Oral administration of mice with KRGE resulted in lowering lung viral loads after RSV infection. Additionally, the in vivo effects of KRGE showed an enhanced level of interferon-γ (IFN-γ) producing dendritic cells subsequent to RSV infection. Taken together, these results suggested that KRGE has antiviral activity against RSV infection.

The respiratory syncytial virus (RSV) nonstructural proteins mediate RSV suppression of glucocorticoid receptor transactivation

Respiratory syncytial virus (RSV)-induced bronchiolitis in infants is not responsive to glucocorticoids. We have shown that RSV infection impairs glucocorticoid receptor (GR) function. In this study, we have investigated the mechanism by which RSV impairs GR function. We have shown that RSV repression of GR-induced transactivation is not mediated through a soluble autocrine factor. Knock-down of mitochondrial antiviral signaling protein (MAVS), but not retinoic acid-inducible gene 1 (RIG-I) or myeloid differentiation primary response gene 88 (MyD88), impairs GR-mediated gene activation even in mock-infected cells. Over-expression of the RSV nonstructural protein NS1, but not NS2, impairs glucocorticoid-induced transactivation and viruses deleted in NS1 and/or NS2 are unable to repress glucocorticoid-induction of the known GR regulated gene glucocorticoid-inducible leucine zipper (GILZ). These data suggest that the RSV nonstructural proteins mediate RSV repression of GR-induced transactivation and that inhibition of the nonstructural proteins may be a viable target for therapy against RSV-related disease.

Respiratory syncytial virus induced type I IFN production by pDC is regulated by RSV-infected airway epithelial cells, RSV-exposed monocytes and virus specific antibodies

Innate immune responses elicited upon virus exposure are crucial for the effective eradication of viruses, the onset of adaptive immune responses and for establishing proper immune memory. Respiratory syncytial virus (RSV) is responsible for a high disease burden in neonates and immune compromised individuals, causing severe lower respiratory tract infections. During primary infections exuberant innate immune responses may contribute to disease severity. Furthermore, immune memory is often insufficient to protect during RSV re-exposure, which results in frequent symptomatic reinfections. Therefore, identifying the cell types and pattern recognition receptors (PRRs) involved in RSV-specific innate immune responses is necessary to understand incomplete immunity against RSV. We investigated the innate cellular response triggered upon infection of epithelial cells and peripheral blood mononuclear cells. We show that CD14⁺ myeloid cells and epithelial cells are the major source of IL-8 and inflammatory cytokines, IL-6 and TNF-α, when exposed to live RSV Three routes of RSV-induced IFN-α production can be distinguished that depend on the cross-talk of different cell types and the presence or absence of virus specific antibodies, whereby pDC are the ultimate source of IFN-α. RSV-specific antibodies facilitate direct TLR7 access into endosomal compartments, while in the absence of antibodies, infection of monocytes or epithelial cells is necessary to provide an early source of type I interferons, required to engage the IFN-α,β receptor (IFNAR)-mediated pathway of IFN-α production by pDC. However, at high pDC density infection with RSV causes IFN-α production without the need for a second party cell. Our study shows that cellular context and immune status are factors affecting innate immune responses to RSV. These issues should therefore be addressed during the process of vaccine development and other interventions for RSV disease.

Resveratrol Inhibits respiratory syncytial virus-induced IL-6 production, decreases viral replication, and downregulates TRIF expression in airway epithelial cells

Respiratory syncytial virus (RSV) is the most common pathogen responsible for lower respiratory diseases in children. So far, there is no effective treatment or preventative vaccine available for RSV infection, although ribavirin and dexamethasone are commonly prescribed. Resveratrol has been shown to inhibit the replication of several other viruses, thus the effect of resveratrol on RSV-induced inflammatory mediators in 9HTEo cell cultures was evaluated, and possible mechanisms of action were explored and compared with dexamethasone and ribavirin. Incubation with resveratrol resulted in decreased IL-6 production and partial inhibition of RSV replication. Resveratrol treatment also inhibited virus-induced TIR-domain-containing adapter-inducing interferon-β (TRIF) and TANK binding kinase 1 (TBK1) protein expression. These data demonstrate the ability of resveratrol to inhibit cytokine production by RSV in airway epithelial cells, indicating that it might be a therapeutic agent with both anti-inflammatory and antiviral potential for the treatment of RSV infection.

Andes-virus-induced cytokine storm is partially suppressed by ribavirin

BACKGROUND

Microbe-induced over-activation of cytokines, especially tumour necrosis factor (TNF)-α, is key to the pathogenesis of hantavirus infection leading to severe inflammation with high mortality rate. Although ribavirin showed promise in inhibiting viral replication in vitro, its clinical efficacy remains controversial.

METHODS

Various concentrations of ribavirin were used to determine its effect on cytokine activation in our infectious model system.

RESULTS

Ribavirin decreased the virus load and dose-dependently inhibited the accumulation of RANTES messenger RNA in Andes-virus (ANDV)-infected human endothelial cells, but failed to suppress TNF-α-induced activation of RANTES and interleukin-6 in ANDV-inoculated cultures. This report also shows, for the first time, that the deleterious over-stimulation by TNF-α is mediated by nuclear factor-κB, and describes the effect of ribavirin on cytokine production following ANDV infection.

CONCLUSIONS

Although highly effective in preventing ANDV replication and suppressing activation of select inflammatory mediators, the therapeutic efficacy of ribavirin is limited due to its inability to fully inhibit cytokine outburst triggered by hantavirus infection.

Induction of IL-6 and CCL5 (RANTES) in human respiratory epithelial (A549) cells by clinical isolates of respiratory syncytial virus is strain specific

BACKGROUND

Respiratory syncytial virus (RSV) is the major respiratory pathogen of infants and young children. During each seasonal epidemic, multiple strains of both subgroup A and B viruses circulate in the community. Like other RNA viruses, RSV genome replication is prone to errors that results in a heterogeneous population of viral strains some of which may possess differences in virulence. We sought to determine whether clinical isolates of RSV differ in their capacity to induce inflammatory cytokines IL-6 and CCL5 (previously known as RANTES [regulated upon activation, normal T-cell expressed and secreted protein]), which are known to be induced in vitro and in vivo in response to RSV, during infection of A549 cells.

RESULTS

Screening of subgroup A and B isolates revealed heterogeneity among strains to induce IL-6 and CCL5. We chose two subgroup B strains, New Haven (NH)1067 and NH1125, for further analysis because of their marked differences in cytokine inducing properties and because subgroup B strains, in general, are less genetically heterogeneous as compared to subgroup A strains. At 12 and 24 hours post infection RSV strains, NH1067 and NH1125 differed in their capacity to induce IL-6 by an order of magnitude or more. The concentrations of IL-6 and CCL5 were dependent on the dose of infectious virus and the concentration of these cytokines induced by NH1125 was greater than that of those induced by NH1067 when the multiplicity of infection of NH1067 used was as much as 10-fold higher than that of NH1125. The induction of IL-6 was dependent on viable virus as infection with UV-inactivated virus did not induce IL-6. The difference in IL-6 induction most likely could not be explained by differences in viral replication kinetics. The intracellular level of RSV RNA, as determined by quantitative RT-PCR, was indistinguishable between the 2 strains though the titer of progeny virus produced by NH1125 was greater than that produced by NH1067 at 16, 24 and 36 hours but essentially equal at 48 and 72 hours. Full genome sequencing of the 2 strains revealed 193 polymorphisms and 4 insertions in NH1067 when compared to NH1125 (2 single base insertions in non-coding regions and 2 duplications of 3 and 60 bases in the RSV G gene). Of the polymorphisms, 147 occurred in coding regions and only 30 resulted in amino acid changes in 7 of the RSV genes.

CONCLUSIONS

These data suggest that RSV strains may not be homogeneous with regard to pathogenesis or virulence. Identification of the genetic polymorphisms associated with variations in cytokine induction may lead to insights into RSV disease and to the development of effective antiviral agents and vaccines.

A new mouse-adapted strain of SARS-CoV as a lethal model for evaluating antiviral agents in vitro and in vivo

Severe acute respiratory syndrome (SARS) is a highly lethal emerging disease caused by coronavirus SARS-CoV. New lethal animal models for SARS were needed to facilitate antiviral research. We adapted and characterized a new strain of SARS-CoV (strain v2163) that was highly lethal in 5- to 6-week-old BALB/c mice. It had nine mutations affecting 10 amino acid residues. Strain v2163 increased IL-1alpha, IL-6, MIP-1alpha, MCP-1, and RANTES in mice, and high IL-6 expression correlated with mortality. The infection largely mimicked human disease, but lung pathology lacked hyaline membrane formation. In vitro efficacy against v2163 was shown with known inhibitors of SARS-CoV replication. In v2163-infected mice, Ampligen was fully protective, stinging nettle lectin (UDA) was partially protective, ribavirin was disputable and possibly exacerbated disease, and EP128533 was inactive. Ribavirin, UDA, and Ampligen decreased IL-6 expression. Strain v2163 provided a valuable model for anti-SARS research.

Amplification of lipopolysaccharide-induced cytokine synthesis in non-small cell lung cancer/neutrophil cocultures

Proinflammatory cytokines are centrally involved in tumor progression and survival in non-small cell lung cancer, and both the presence of infiltrating neutrophils and bacterial infection in the lung may indicate a poor prognosis. Against this background, we investigated the effect of the bacterial cell wall component lipopolysaccharide (LPS) on interleukin (IL)-6 and IL-8 synthesis in the non-small cell lung cancer line A549 and in A549-neutrophil cocultures. The LPS induced a dose-dependent and time-dependent release of IL-8 from A549 cells, whereas IL-6 could not be detected. Interestingly, in A549-neutrophil cocultures, IL-8 synthesis was massively amplified and IL-6 was also released, compared with the respective monocultures. The A549 cells were identified as the primary cellular source of these cytokines, as enhanced cytokine mRNA transcription was detected in this cell type, although not in neutrophils in the coculture system. Experiments done in transwells indicated that direct cell-cell contact was a prerequisite for the increased cytokine generation. Inhibition of tumor necrosis factor-alpha bioactivity by neutralizing antibodies and blocking cyclooxygenase-2 activity blunted the enhanced cytokine generation in the coculture system. Amplification of LPS-induced cytokine secretion could be reproduced when the small cell lung cancer cell line H69 was cocultured with neutrophils. When the Gram-positive cell wall component lipoteichoic acid was used instead of LPS, cytokine synthesis was also amplified in A549-neutrophil cocultures, to a similar extent to that observed with LPS. These data indicate that interaction between bacterial pathogens, neutrophils, and tumor cells might amplify the release of proinflammatory cytokines which may promote tumor growth in vivo.

Anticancer oncolytic activity of respiratory syncytial virus

Oncolytic virotherapy is an emerging bio-therapeutic platform for cancer treatment, which is based on selective infection/killing of cancer cells by viruses. Herein we identify the human respiratory syncytial virus (RSV) as an oncolytic virus. Using prostate cancer models, we show dramatic enhancement of RSV infectivity in vitro in the androgen-independent, highly metastatic PC-3 human prostate cancer cells compared to the non-tumorigenic RWPE-1 human prostate cells. The oncolytic efficiency of RSV was established in vivo using human prostate tumor xenografts in nude mice. Intra-tumoral and intra-peritoneal injections of RSV led to a significant regression of prostate tumors. Furthermore, enhanced viral burden in PC-3 cells led to selective destruction of PC-3 cancer cells in vitro and in xenograft tumors in vivo due to apoptosis triggered by the down-regulation of NF-κB activity (and the resulting loss of anti-apoptotic function of NF-κB) in RSV-infected PC-3 cells. The intrinsic (mitochondrial) pathway constitutes the major apoptotic pathway; however, the death-receptor-dependent extrinsic pathway, mediated by the paracrine/autocrine action of tumor necrosis factor-α produced from infected cells, also partly contributed to apoptosis. Thus, the oncolytic property of RSV can potentially be exploited to develop targeted therapeutics for the clinical management of prostate tumors.

Functionally competent eosinophils differentiated ex vivo in high purity from normal mouse bone marrow

We have devised an ex vivo culture system which generates large numbers of eosinophils at high purity (>90%) from unselected mouse bone marrow progenitors. In response to 4 days of culture with recombinant mouse FLT3-L and recombinant mouse stem cell factor followed by recombinant mouse IL-5 alone thereafter, the resulting bone marrow-derived eosinophils (bmEos) express immunoreactive major basic protein, Siglec F, IL-5R alpha-chain, and transcripts encoding mouse eosinophil peroxidase, CCR3, the IL-3/IL-5/GM-CSF receptor common beta-chain, and the transcription factor GATA-1. BmEos are functionally competent: they undergo chemotaxis toward mouse eotaxin-1 and produce characteristic cytokines, including IFN-gamma, IL-4, MIP-1alpha, and IL-6. The rodent pathogen pneumonia virus of mice replicates in bmEos and elevated levels of IL-6 are detected in supernatants of bmEos cultures in response to active infection. Finally, differentiating bmEos are readily transfected with lentiviral vectors, suggesting a means for rapid production of genetically manipulated cells.

Involvement of NADPH oxidase and iNOS in rodent pulmonary cytokine responses to urban air and mineral particles

We have investigated the potential of two complex mineral particles (feldspar and mylonite), quartz (Min-U-Sil), and suspended particulate matter (SRM-1648) (SPM) from urban air to induce inflammatory cytokine responses in primary rat alveolar type 2 cells and alveolar macrophages, and the involvement of cellular formation of free radicals in these responses. All particle types induced an increased release of interleukin (IL)-6 and macrophage inflammatory protein (MIP)-2 from type 2 cells. Diphenyleneiodonium chloride (DPI), a selective inhibitor of NADPH-oxidase, reduced the IL-6 and MIP-2 responses to quartz, SPM and mylonite. N-(3-[Aminomethyl] benzyl) acetamidine (1400W), a selective inhibitor of inducible nitric oxide synthase (iNOS), significantly reduced the Il-6 response to SPM and feldspar in the type 2 cells. The macrophages displayed significantly increased TNF-alpha and MIP-2 release upon exposure to quartz or SPM. Here, DPI significantly reduced the tumor necrosis factor (TNF)-alpha and MIP-2 responses to quartz, and the MIP-2 response to SPM. No significant effect of 1400 W was detected in the alveolar macrophages. The role of particle-induced cellular generation of free radicals in lung cytokine responses was further elucidated in mice that lacked either NADPH-oxidase or iNOS as well as in wild-type (wt) mice. All particles were able to elicit increased cytokine levels in the bronchoalveolar lavage (BAL) fluid of the mice, although the levels depended on particle type. The NADPH-oxidase knockout (KO) mice demonstrated a significantly lower IL-6 and MIP-2 responses to SPM compared to their respective wt mice. The iNOS KO mice displayed significantly reduced IL-6, TNF-alpha, and MIP-2 responses to SPM. The overall results indicate the involvement of cellular free-radical formation in the pulmonary cytokine responses to particles of varying composition.

Diminished inflammatory responses to natural pneumovirus infection among older mice

Immune responses to virus infection undergo significant change as part of the aging process. Here we examine the inflammatory responses of older, but otherwise immunologically naive mice to infection with pneumonia virus of mice (PVM). Although we see no changes in the extent or kinetics of virus replication, we observe diminished local production of inflammatory mediators, including MIP-1alpha, JE/MCP-1, IFN-gamma and IFN-gamma-induced MIG and IP-10, and interleukins (IL)-6 and IL-17. Levels of KC and IL-1alpha remained unchanged. Age-dependent diminished production of proinflammatory mediators was associated with diminished recruitment of granulocytes and reduced severity of clinical responses, including weight loss and respiratory dysfunction. The differences observed when comparing these results to those reported among elderly human subjects may be related to the specific extent of aging and its impact on biochemical and cellular inflammatory responses and/or the role of lifetime virus re-exposure on the clinical outcome from acute pneumovirus disease.

RSV-infected airway epithelial cells cause biphasic up-regulation of CCR1 expression on human monocytes

Respiratory syncytial virus (RSV) infection can cause extensive airway inflammation, which is orchestrated by chemokines and their receptors. RSV-infected epithelial cells secrete many cytokines and chemokines, but little is known about regulation of chemokine receptors on target cells. We investigated the effects of conditioned media (CM) from RSV-infected epithelial cells on monocyte CCR1, CCR2, and CCR5 expression. RSV-CM but not control-CM stimulated a biphasic increase in cell-surface CCR1, and levels peaked at 36 h and 96 h poststimulation. Similar CCR1 up-regulation occurred on monocyte-derived macrophages. Cytochlasin D and colchicine blocked both peaks of expression, demonstrating requirement of a functional cytoskeleton. Intracellular staining revealed little internal sequestration of CCR1 protein, and CCR1 up-regulation was inhibited by actinomycin D and cycloheximide, indicating that both waves of RSV-CM-induced surface CCR1 expression were dependent on de novo transcription and protein synthesis. Cytokine-neutralizing experiments showed that the effects of RSV-CM were decreased by blocking TNF-alpha (percent inhibition=51+/-2.3% at 36 h peak and 42+/-7.7% at 96 h peak) and to a lesser extent, IL-1 (percent inhibition=32+/-7.2% at 36 h and 23+/-2.9% at 96 h). In summary, RSV-CM causes a biphasic up-regulation of surface CCR1 on monocytes, which is dependent on an intact cytoskeleton, requires new gene transcription and protein synthesis, and is mediated in part by the proinflammatory cytokines TNF-alpha and IL-1.

T helper 1/T helper 2 cytokine imbalance in respiratory syncytial virus infection is associated with increased endogenous plasma cortisol

OBJECTIVE

Cellular immunity has classically been described as the defense mechanism for viral infections. The development of cellular or humoral immune responses will depend on a repertoire of cytokines produced by numerous cells, including CD4+ and CD8+ T cells. These lymphocytes can be subdivided into 2 subsets, T helper 1 (Th1) and Th2, on the basis of the cytokine profiles they synthesize. Type 1 T cells produce interferon gamma (IFN-gamma), an essential cytokine in the viral cell-mediated immune response. Th2 cells selectively produce interleukin 4 (IL-4) and IL-5 that participate in the development of humoral immunity and have a prominent role in immediate-type hypersensitivity. An imbalance in the Th1/Th2 cytokine immune response has been related to pathogenesis of the respiratory syncytial virus (RSV) bronchiolitis and to the severity of the infection. Glucocorticosteroids have a role in inhibiting the IFN-gamma response, acting directly on T cells or indirectly through IL-12. In this way, an increase in plasma cortisol would induce a decrease in the Th1 products with the imbalance between Th1/Th2 cytokines and a shift to Th2 response. We hypothesized that there is a relationship among endogenous cortisol response in acute RSV infection, severity of illness, and decreased Th1 cytokine response.

METHODS

We studied 42 infants under 12 months of age during an acute RSV infection. Twenty-one infants with a median age of 6 months had a severe illness and required hospitalization, whereas 21 with mild diseases with a median age of 7 months were under ambulatory control. All of them had bronchial obstruction evidenced by wheezing and/or hyperinflation on chest radiograph and positive RSV antigen detected by indirect immunofluorescence in nasopharyngeal aspirates. The control group included 21 infants in good health matched by age and gender with median age of 6 months that required blood tests for minor surgery. They were evaluated during a non-RSV epidemic period. Heparinized blood was collected on enrollment from all participating children at 9 am for total leukocyte and differential cell count, determination of lymphocyte subsets, and for intracellular detection of cytokines in single cells; mononuclear cells were cultured to determine in the supernatant cytokine production. In addition, 1 mL of plasma was separated and kept frozen at -20 degrees C for cortisol assay. In the supernatant of the cultured peripheral blood mononuclear cells (PBMCs), we quantified IL-12, IFN-gamma, IL-4, IL-5, and IL-10. Lymphocyte phenotypes and CD4+ and CD8+ T cells with intracellular IL-4, IL-10, and IFN-gamma were analyzed by triple-color immunofluorescence of single cells on a FACScan flow cytometer.

RESULTS

Infants with severe illness had significantly higher plasma cortisol levels than infants with mild disease, and in both groups of infected infants, those were higher than in the control group. A significantly decreased IL-12 and IFN-gamma production by PBMCs and a fall in the percentage of CD4+ T cells expressing IFN-gamma were observed only in the severely affected infants. IL-12 concentrations were 2 pg/mL in severe illness versus 13 pg/mL in mildly infected infants and 12 pg/mL in controls. PBMCs from infants with severe illness produced less IFN-gamma than mildly infected infants and than controls when compared with severe illness. No differences between the 3 groups of infants were observed during the acute phase of the disease for IL-4, IL-5, and IL-10. IL-12 and IFN-gamma production had an inverse correlation with plasma cortisol levels. During severe RSV bronchiolitis, infants developed lymphopenia, and significantly lower eosinophil counts and percentages and absolute counts of CD4+ and CD8+ T cells. Eighty days postinfection, all values had returned to normal levels.

CONCLUSIONS

In this study, we demonstrate that during the acute phase of RSV infection, there is an increase in the level of plasma cortisol that is parallel to the decrease in IL-12 and IFN-gamma production. These findings suggest an association between increased plasma cortisol and a decreased Th1-type response. The increase in plasma cortisol was greater in infants with the more severe symptomatology in association with a lower level of IL-12 and IFN-gamma production. The potential causative role of endogenous cortisol in the imbalance of the Th1/Th2 response observed during severe RSV infection requires additional investigation. Our results suggest that the immunologic changes observed in the more severely ill patients may be partially explained by the increased levels of plasma cortisol. This finding should be taken into consideration when systemic steroids are prescribed to infants infected with the RSV because there is still controversy regarding the efficacy of systemic steroid use in severe bronchiolitis.

Modulation of respiratory syncytial virus-induced prostaglandin E2 production by n-3 long-chain polyunsaturated fatty acids in human respiratory epithelium

Infection with respiratory syncytial virus (RSV) results in substantial infant morbidity and has been associated with the subsequent development of childhood asthma. Inflammatory mediators produced by both the epithelium and tissue leukocytes during RSV infection stimulate the release of chemotactic factors by the respiratory epithelium and the subsequent influx of inflammatory cells, predominantly neutrophils. We investigated the production of inflammatory mediators [prostaglandin E2 (PGE2), interleukin (IL)-1beta, tumor necrosis factor alpha] and chemokines [IL-8, RANTES (regulation on activation, normal T cell expressed and secreted)] by alveolar epithelial cells in response to RSV infection. Infection of a human alveolar epithelial transformed cell line (A549 cells) with live RSV substantially increased production of PGE2, IL-8, and RANTES. By altering cell membrane FA through incorporation of the long-chain PUFA (LCPUFA) arachidonic acid, EPA, and DHA, we were subsequently able to significantly modulate PGE2 production by the infected epithelium. Because of the dynamic nature of the effects of PGE2 on lung function, regulation of this prostaglandin during RSV infection by n-3 LCPUFA has the potential to significantly alter the disease process.

Peroxisome-proliferator-activated receptor-gamma agonists inhibit the release of proinflammatory cytokines from RSV-infected epithelial cells

The epithelial cells of the airways are the target cells for respiratory syncytial virus (RSV) infection and the site of the majority of the inflammation associated with the disease. Recently, peroxisome-proliferator-activated receptor gamma (PPARgamma), a member of the nuclear hormone receptor superfamily, has been shown to possess anti-inflammatory properties. Therefore, we investigated the role of PPARgamma agonists (15d-PGJ(2), ciglitazone and troglitazone) on the synthesis of RSV-induced cytokine release from RSV-infected human lung epithelial cells (A549). We observed that all PPARgamma ligands inhibited dose-dependently the release of TNF-alpha, GM-CSF, IL-1alpha, IL-6 and the chemokines CXCL8 (IL-8) and CCL5 (RANTES) from RSV-infected A549 cells. Concomitantly, the PPARgamma ligands diminished the cellular amount of mRNA encoding for IL-6, CXCL8 and CCL5 and the RSV-induced binding activity of the transcription factors NF-kappaB (p65/p50) and AP-1 (c-fos), respectively. Our data presented herein suggest a potential application of PPARgamma ligands in the anti-inflammatory treatment of RSV infection.

Hepatitis C virus-specific cytolytic T cell responses after antiviral therapy

Antigen-specific T cells are likely to provide a critical defense against hepatitis C virus (HCV) infection. However, their detection in blood is uncommon except in persons who undergo spontaneous recovery after acute HCV infection. We postulated that virological responses after antiviral interferon-alpha therapy may be associated with enhanced cytolytic T cell immunity. Peripheral blood memory CTL responses were quantified using short term limiting dilution culture, with cytolytic function detected by standard chromium release assay. In this cross-sectional study, 5 of 11 interferon-alpha or interferon-alpha plus ribavirin-treated subjects exhibited cytolytic T cell responses after therapy completion; 4 of these 5 subjects were HCV RNA negative at the time of assay. In contrast, only 1 of 9 untreated chronically viremic subjects had detectable HCV-specific cytolytic T cell responses. Although the requisite factors necessary to achieve sustained virologic response after therapy remain largely undefined, the findings presented here suggest that antiviral therapy-induced virological clearance may be associated with the induction, expansion, and/or recirculation of HCV antigen-specific cytolytic T cells, and may play a role in the maintenance of a nonviremic state.

Ribavirin treatment up-regulates antiviral gene expression via the interferon-stimulated response element in respiratory syncytial virus-infected epithelial cells

Respiratory syncytial virus (RSV) is a mucosa-restricted virus that is a leading cause of epidemic respiratory tract infections in children. RSV replication is a potent activator of the epithelial-cell genomic response, influencing the expression of a spectrum of cellular pathways, including proinflammatory chemokines of the CC, CXC, and CX(3)C subclasses. Ribavirin (1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) is a nontoxic antiviral agent currently licensed for the treatment of severe RSV lower respiratory tract infections. Because ribavirin treatment reduces the cytopathic effect in infected cells, we used high-density microarrays to investigate the hypothesis that ribavirin modifies the virus-induced epithelial genomic response to replicating virus. Ribavirin treatment administered in concentrations of 10 to 100 micro g/ml potently inhibited RSV transcription, thereby reducing the level of RSV N transcripts to approximately 13% of levels in nontreated cells. We observed that in both the absence and the presence of ribavirin, RSV infection induced global alterations in the host epithelial cell, affecting approximately 49% of the approximately 6,650 expressed genes detectable by the microarray. Ribavirin influences the expression of only 7.5% of the RSV-inducible genes (total number of genes, 272), suggesting that the epithelial-cell genetic program initiated by viral infection is independent of high-level RSV replication. Hierarchical clustering of the ribavirin-regulated genes identified four expression patterns. In one group, ribavirin inhibited the expression of the RSV-inducible CC chemokines MIP-1 alpha and -1 beta, which are important in RSV-induced pulmonary pathology, and interferon (IFN), a cytokine important in the mucosal immune response. In a second group, ribavirin further up-regulated a set of RSV- and IFN-stimulated response genes (ISGs) encoding antiviral proteins (MxA and p56), complement products, acute-phase response factors, and the STAT and IRF transcription factors. Because IFN-beta expression itself was reduced in the ribavirin-treated cells, we further investigated the mechanism for up-regulation of the IFN-signaling pathway. Enhanced expression of IFI 6-16, IFI 9-27, MxA/p78, STAT-1 alpha, STAT-1 beta, IRF-7B, and TAP-1-LMP2 transcripts were independently reproduced by Northern blot analysis. Ribavirin-enhanced TAP-1-LMP2 expression was a transcriptional event where site mutations of the IFN-stimulated response element (ISRE) blocked RSV and ribavirin-inducible promoter activity. Furthermore, ribavirin up-regulated the transcriptional activity of a reporter gene selectively driven by the ISRE. In specific DNA pull-down assays, we observed that ribavirin enhanced RSV-induced STAT-1 binding to the ISRE. We conclude that ribavirin potentiates virus-induced ISRE signaling to enhance the expression of antiviral ISGs, suggesting a mechanism for the efficacy of combined treatment with ribavirin and IFN in other chronic viral diseases.

Role of p38 mitogen-activated protein kinase in rhinovirus-induced cytokine production by bronchial epithelial cells

The stress-activated protein kinase p38 plays a central role in the regulation of cytokine biosynthesis by various cell types in response to a wide range of stimuli. Because the local inflammatory response and the infiltration of neutrophils is thought to contribute to the symptoms and sequelae of rhinovirus infection, we investigated the role of p38 kinase in cytokine and chemokine elaboration in airway epithelial cells infected with human rhinovirus. Rhinovirus-39 infection of BEAS-2B cells resulted in synthesis of cytokines (IL-1, IL-6, G-CSF, and GM-CSF) and CXC chemokines (IL-8, epithelial neutrophil-activating protein-78, and growth-related oncogene-alpha), evident 24-72 h postinfection. Rhinovirus infection induced a time- and dose-dependent increase in tyrosine phosphorylation of p38 kinase, which peaked 30 min postinfection and remained elevated for 1 h. Treatment of infected cells with SB 239063, a potent pyridinyl imidazole inhibitor of p38 kinase, resulted in up to 100% inhibition of mediator production and partially reduced levels of IL-8 mRNA as determined by quantitative RT-PCR. Treatment with SB 239063 had no effect on virus replication and was not cytotoxic at concentrations </= 70 microM. These studies provide the first evidence that early activation of p38 kinase by rhinovirus infection is a key event in regulation of virus-induced cytokine transcription, and may provide a new target for inhibition of symptoms and airway inflammation associated with rhinovirus infection.

Ribavirin enhancement of hepatitis C virus core antigen-specific type 1 T helper cell response correlates with the increased IL-12 level

BACKGROUNDS/AIMS

Combination IFN-a and ribavirin therapy for hepatitis C virus-infected patients has been reported to improve the response rate up to 50%. In this study, we aimed to study further the role of ribavirin in hepatitis C virus-specific immune responses.

METHODS

We immunized mice with hepatitis C virus core protein with or without different concentrations of ribavirin. Forty days after immunization, hepatitis C virus-specific immune responses were followed in these mice.

RESULTS

We found that the mice immunized with core antigen once every 2 weeks and 0.5 mg ribavirin every day showed higher levels of core-specific IgG2 compared with those mice immunized with core antigen only. In addition, core antigen-stimulated spleen cells produced higher levels of T helper type 1 cytokines and the core-specific cytotoxic T cell activity also increased significantly. Furthermore, lipopolysaccharide-stimulated peritoneal cells produced higher levels of IL-12 in ribavirin-treated mice, and peritoneal cells isolated from naive mice also produced significantly higher level of IL-12 when cultured with ribavirin.

CONCLUSIONS

Ribavirin may significantly promote the T helper type 1 immune response in vivo, and, furthermore, the effect of ribavirin on IL-12 level produced by accessory cells may contribute to the T helper type 1 enhancing effect.

Increased pulmonary secretion of tumor necrosis factor-alpha in calves experimentally infected with bovine respiratory syncytial virus

Bovine respiratory syncytial virus (BRSV) is an important cause of respiratory disease among calves in the Danish cattle industry. An experimental BRSV infection model was used to study the pathogenesis of the disease in calves. Broncho alveolar lung lavage (BAL) was performed on 28 Jersey calves, of which 23 were experimentally infected with BRSV and five were given a mock inoculum. The presence of the cytokine tumor necrosis factor alpha (TNF-alpha) in the BAL fluids was detected and quantified by a capture ELISA. TNF-alpha was detected in 21 of the infected animals. The amount of TNF-alpha in the BAL fluid of calves killed post inoculation day (PID) 2 and 4 was at the same very low level as in the uninfected control animals. Large amounts of TNF-alpha were detected on PID 6, maximum levels of TNF-alpha were reached on PID 7, and smaller amounts of TNF-alpha were seen on PID 8. The high levels of TNF-alpha appeared on the days where severe lung lesions and clinical signs were obvious and the amounts of BRSV-antigen were at their greatest. Although Pasteurellaceae were isolated from some of the BRSV-infected calves, calves treated with antibiotics before and through the whole period of the infection, as well as BRSV-infected calves free of bacteria reached the same level of TNF-alpha as animals from which bacteria were isolated from the lungs. It is concluded that significant quantities of TNF-alpha are produced in the lungs of the calves on PID 6-7 of BRSV infection. The involvement of TNF-alpha in the pathogenesis of, as well as the anti-viral immune response against, BRSV infection is discussed.

Tumor necrosis factor (TNF)-alpha and TNF receptors in viral pathogenesis

Tumor necrosis factor-alpha (TNF-alpha) and TNF receptors (TNFR) are members of the growing TNF ligand and receptor families that are involved in immune regulation. The present report will focus on the role of the prototypic ligand TNF and its two receptors, TNFR1 and TNFR2, in viral pathogenesis. Although TNF was reported years ago to modulate viral infections, recent findings on the molecular pathways involved in TNFR signaling have allowed a better understanding of the molecular interactions between cellular and viral factors within the infected cell. The interactions of viral proteins with intracellular components downstream of the TNFR have highlighted at the molecular level how viruses can manipulate the cellular machinery to escape the immune response and to favor the spread of the infection. We will review here the role of TNF and TNFR in immune response and the role of TNF and TNFR signaling in viral pathogenesis.

Viral-Bacterial Synergy in Otitis Media: Implications for Management

Despite the extensive use of broad-spectrum antibiotics, poor clinical response to the treatment of acute otitis media is common. Evidence derived from numerous studies during the past two decades supports a crucial role for respiratory viruses in the etiology and pathogenesis of acute otitis media, and recent studies indicate that viruses may also have a profound adverse effect on the resolution of this disease. Viruses seem to interact with bacteria and enhance the local inflammatory process in the middle ear. Effective adjuvant therapies are needed to improve outcome in children with otitis media. Increasing knowledge of the role of viruses, viral-bacterial interaction, and host inflammatory mechanisms in otitis media may lead to major improvements in the management of this disease.

Elevated cytokine concentrations in the nasopharyngeal and tracheal secretions of children with respiratory syncytial virus disease

BACKGROUND

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract disease in infants. The role of inflammatory mediators in the pathogenesis of RSV disease is not well-understood. The present study was designed (1) to determine whether RANTES (regulated on activation, normal T cell expressed and presumably secreted), macrophage-inflammatory protein-1-alpha (MIP-1-alpha), interleukin (IL)-6, IL-8 and IL-10 can be detected in respiratory secretions of children with RSV infection and (2) to assess whether the concentrations of these cytokines in respiratory secretions correlate with white blood cell (WBC) counts and RSV concentrations and with disease severity.

METHODS

During the 1996 to 1997 RSV season, we studied prospectively 14 intubated and 14 nonintubated children hospitalized with RSV disease. Nasal wash (NW) and tracheal aspirate (TA) samples were obtained from intubated patients on Hospital Days 1, 3 and 5. NW samples were obtained from nonintubated patients on hospital days 1 and 3. Seven healthy children undergoing elective surgery served as controls. All samples were analyzed for: (1) WBC and differential counts; (2) concentrations of RANTES, MIP-1-alpha, IL-6, IL-8 and IL-10; and (3) quantitative RSV cultures, except in control patients.

RESULTS

RANTES, MIP-1-alpha, IL-6, IL-8 and IL-10 were detected in NW and TA samples from all children with RSV infection. The concentrations of these cytokines in samples obtained from children with RSV infection were significantly greater than those in samples obtained from control children. NW WBC counts significantly correlated with NW RANTES, IL-6, IL-8 and IL-10 concentrations, whereas TA WBC counts significantly correlated with TA IL-6, IL-8, IL-10 and MIP-1-alpha concentrations. NW RSV concentrations correlated with NW WBC counts and with NW cytokine concentrations. Among children with RSV infection nonintubated patients had greater NW WBC counts and NW RANTES concentrations than intubated patients. TA RANTES, IL-8 and IL-10 concentrations inversely correlated with clinical markers of RSV disease severity.

CONCLUSION

The presence of cytokines in NW and TA samples of children with RSV infection suggests that they have a role in mediating the respiratory tract inflammation induced by RSV. These observations could have implications for designing new therapeutic strategies directed at immunomodulation of RSV disease.