Enhanced pulmonary histopathology induced by respiratory syncytial virus (RSV) challenge of formalin-inactivated RSV-immunized BALB/c mice is abrogated by depletion of interleukin-4 (IL-4) and IL-10.

In previous studies, children immunized with a formalin-inactivated respiratory syncytial virus vaccine (FI-RSV) developed severe pulmonary disease with greater frequency than did controls during subsequent natural RSV infection. In earlier efforts to develop an animal model for this phenomenon, extensive pulmonary histopathology developed in FI-RSV-immunized cotton rats and mice subsequently challenged with RSV. In mice, depletion of CD4+ T cells at the time of RSV challenge completely abrogated this histopathology. Furthermore, the predominant cytokine mRNA present in lungs of FI-RSV-immunized mice during subsequent infection with RSV was that characteristically secreted by Th2 T cells, namely interleukin-4 (IL-4). In the present studies, we sought to determine the relative contributions of gamma interferon (IFN-gamma), IL-2, IL-4, and IL-10 to the lymphocytic infiltration into the lungs observed following RSV challenge of mice previously immunized with FI-RSV. Mice previously immunized with FI-RSV or infected with RSV were depleted of IFN-gamma, IL-2, IL-4, or IL-10 immediately before RSV challenge, and the magnitude of inflammatory cell infiltration around bronchioles and pulmonary blood vessels was quantified. The phenomenon of pulmonary-histopathology potentiation by FI-RSV was reproduced in the present study, thereby allowing us to investigate the effect of cytokine depletion on the process. Simultaneous depletion of both IL-4 and IL-10 completely abrogated pulmonary histopathology in FI-RSV-immunized mice. Depletion of IL-4 alone significantly reduced bronchiolar, though not perivascular, histopathology. Depletion of IL-10 alone had no effect. Depletion of IFN-gamma, IL-2, or both together had no effect on the observed histopathology. These data indicate that FI-RSV immunization primes for a Th2-, IL-4-, and IL-10-dependent inflammatory response to subsequent RSV infection. It is possible that this process played a role in enhanced disease observed in infants and children immunized with FI-RSV.     

The cotton rat (Sigmodon hispidus) is a permissive small animal model of human metapneumovirus infection, pathogenesis, and protective immunity

Human metapneumovirus (hMPV) is a newly described paramyxovirus that is an important cause of acute respiratory tract disease. We undertook to develop a small animal model of hMPV infection, pathogenesis, and protection. Hamsters, guinea pigs, cotton rats, and nine inbred strains of mice were inoculated intranasally with hMPV. The animals were sacrificed, and nasal and lung tissue virus yields were determined by plaque titration. None of the animals exhibited respiratory symptoms. The quantity of virus present in the nasal tissue ranged from 4.6 x 10(2) PFU/gram tissue (C3H mice) to greater than 10(5) PFU/gram (hamster). The amount of virus in the lungs was considerably less than in nasal tissue in each species tested, ranging from undetectable (<5 PFU/g; guinea pigs) to 1.8 x 10(5) PFU/gram (cotton rat). The peak virus titer in cotton rat lungs occurred on day 4 postinfection. hMPV-infected cotton rat lungs examined on day 4 postinfection exhibited histopathological changes consisting of peribronchial inflammatory infiltrates. Immunohistochemical staining detected virus only at the luminal surfaces of respiratory epithelial cells throughout the respiratory tract. hMPV-infected cotton rats mounted virus-neutralizing antibody responses and were partially protected against virus shedding and lung pathology on subsequent rechallenge with hMPV. Viral antigen was undetectable in the lungs on challenge of previously infected animals. This study demonstrates that the cotton rat is a permissive small animal model of hMPV infection that exhibits lung histopathology associated with infection and that primary infection protected animals against subsequent infection. This model will allow further in vivo studies of hMPV pathogenesis and evaluation of vaccine candidates.     

Recombinant Influenza Virus Carrying the Respiratory Syncytial Virus (RSV) F85-93 CTL Epitope Reduces RSV Replication in Mice

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in infants worldwide. Despite decades of research, there is still no registered vaccine available for this major pathogen. We investigated the protective efficacy of a recombinant influenza virus, PR8/NA-F_85–93, that carries the RSV CD8⁺ T cell epitope F_85–93 in its neuraminidase stalk. F_85–93-specific cytotoxic T lymphocytes (CTLs) were induced in mice after a single intranasal immunization with PR8/NA-F_85-93 virus, and these CTLs provided a significant reduction in the lung viral load upon a subsequent challenge with RSV. To avoid influenza-induced morbidity, we treated mice with matrix protein 2 (M2e)-specific monoclonal antibodies before PR8/NA-F_85-93 virus infection. Treatment with anti-M2e antibodies reduced the infiltration of immune cells in the lungs upon PR8/NA-F_85-93 infection, whereas the formation of inducible bronchus-associated lymphoid tissue was not affected. Moreover, this treatment prevented body weight loss yet still permitted the induction of RSV F-specific T cell responses and significantly reduced RSV replication upon challenge. These results demonstrate that it is possible to take advantage of the infection-permissive protection of M2e-specific antibodies against influenza A virus to induce heterologous CD8⁺ T cell-mediated immunity by an influenza A virus vector expressing the RSV F_85-93 epitope.     

Local IL-17A Potentiates Early Neutrophil Recruitment to the Respiratory Tract during Severe RSV Infection

Respiratory syncytial virus (RSV) bronchiolitis triggers a strong innate immune response characterized by excessive neutrophil infiltration which contributes to RSV induced pathology. The cytokine IL-17A enhances neutrophil infiltration into virus infected lungs. IL-17A is however best known as an effector of adaptive immune responses. The role of IL-17A in early immune modulation in RSV infection is unknown. We aimed to elucidate whether local IL-17A facilitates the innate neutrophil infiltration into RSV infected lungs prior to adaptive immunity. To this end, we studied IL-17A production in newborns that were hospitalized for severe RSV bronchiolitis. In tracheal aspirates we measured IL-17A concentration and neutrophil counts. We utilized cultured human epithelial cells to test if IL-17A regulates RSV infection-induced IL-8 release as mediator of neutrophil recruitment. In mice we investigated the cell types that are responsible for early innate IL-17A production during RSV infection. Using IL-17A neutralizing antibodies we tested if IL-17A is responsible for innate neutrophil infiltration in mice. Our data show that increased IL-17A production in newborn RSV patient lungs correlates with subsequent neutrophil counts recruited to the lungs. IL-17A potentiates RSV-induced production of the neutrophil-attracting chemokine IL-8 by airway epithelial cells in vitro. Various lung-resident lymphocytes produced IL-17A during early RSV infection in Balb/c mice, of which a local population of CD4 T cells stood out as the predominant RSV-induced cell type. By removing IL-17A during early RSV infection in mice we showed that IL-17A is responsible for enhanced innate neutrophil infiltration in vivo. Using patient material, in vitro studies, and an animal model of RSV infection, we thus show that early local IL-17A production in the airways during RSV bronchiolitis facilitates neutrophil recruitment with pathologic consequences to infant lungs.     

Passive transfer of respiratory syncytial virus (RSV) antiserum suppresses the immune response to the RSV fusion (F) and large (G) glycoproteins expressed by recombinant vaccinia viruses.

In young infants who possess maternally derived respiratory syncytial virus (RSV) antibodies, the antibody response to RSV glycoproteins is relatively poor, despite extensive replication of RSV. In the present study, it was found that cotton rat RSV hyperimmune antiserum suppressed the antibody response to the RSV glycoproteins but not the response to vaccinia virus antigens when the antiserum was passively transferred to cotton rats prior to infection with vaccinia recombinant viruses expressing the RSV envelope glycoproteins. The cotton rats which had their immune responses suppressed by passively transferred antibodies were more susceptible to infection with RSV than were animals inoculated with control serum lacking RSV antibodies. Furthermore, many of the immunosuppressed animals infected with the vaccinia recombinant viruses developed RSV glycoprotein antibodies which had abnormally low neutralizing activities. Thus, preexisting serum RSV antibodies had dramatic quantitative and qualitative effects on the immune response to RSV glycoproteins, which may explain, in part, the poor RSV antibody response of young human infants to infection with RSV. Our observations also suggest that immunosuppression by preexisting, passively acquired RSV antibodies may constitute a major obstacle to RSV immunoprophylaxis during early infancy, when immunization is most needed.     

Quantitative aspects of passive immunity to respiratory syncytial virus infection in infant cotton rats

The amount of passively acquired serum respiratory syncytial virus (RSV)-neutralizing antibodies required to protect the respiratory tract of cotton rats against infection was studied. Infant cotton rats were inoculated intraperitoneally with various dilutions of a single pool of sera derived from cotton rats convalescent from RSV infection. After 24 h, these animals were inoculated with RSV intranasally. Virus replication in the respiratory tract was suppressed in cotton rats which had a serum neutralizing antibody titer of 1:100 or greater. Resistance was greater in the lungs than in the nose. Complete or almost complete resistance in the lungs was observed in cotton rats with a serum neutralizing antibody titer of 1:380 or greater. The level of serum RSV-neutralizing antibodies required to confer significant resistance to infection in the cotton rat was similar to the level of maternally derived serum antibodies possessed by human infants less than 2 months of age, who as a group exhibit relative resistance to RSV disease compared with infants 2 to 6 months of age.     

Pulmonary histopathology induced by respiratory syncytial virus (RSV) challenge of formalin-inactivated RSV-immunized BALB/c mice is abrogated by depletion of CD4+ T cells.

In previous studies, it was observed that children immunized with a formalin-inactivated respiratory syncytial virus vaccine (FI-RSV) developed severe pulmonary disease with greater frequency during subsequent natural RSV infection than did controls. During earlier efforts to develop an animal model of this phenomenon, enhanced pulmonary histopathology was observed after intranasal RSV challenge of FI-RSV-immunized cotton rats. Progress in understanding the immunologic basis for these observations has been hampered by the lack of reagents useful in manipulating the immune response of the cotton rat. This problem prompted us to reinvestigate the characteristics of immunity to RSV in the mouse. In the present studies, extensive pulmonary histopathology was observed in FI-RSV-immunized or RSV-infected BALB/c mice upon RSV challenge, and studies to determine the relative contributions of CD4+ or CD8+ T cells to this process were undertaken. Mice previously immunized with FI-RSV or infected with RSV were depleted of CD4+, CD8+, or both T-cell subsets immediately prior to RSV challenge, and the magnitude of inflammatory cell infiltration around bronchioles and pulmonary blood vessels and into alveolar spaces was quantified. The magnitude of infiltration at each anatomic site in previously FI-RSV-immunized or RSV-infected, nondepleted animals was similar, indicating that this is not a relevant model for enhanced disease. However, the effect of T-cell subset depletion on pulmonary histopathology following RSV challenge was very different between the two groups. Depletion of CD4+ T cells completely abrogated pulmonary histopathology in FI-RSV-immunized mice, whereas it had a much smaller effect on mice previously infected with RSV. FI-RSV-immunized or RSV-infected animals depleted of CD8+ T cells had only a modest reduction of pulmonary histopathology. In addition, RSV infection induced high levels of major histocompatibility complex class I-restricted cytotoxic T-cell activity, whereas FI-RSV immunization induced a low level. These data indicate that immunization with FI-RSV induces a cellular immune response different from that induced by RSV infection, which likely played a role in enhanced disease observed in infants and children.     

Cutting Edge: Oseltamivir decreases T cell GM1 expression and inhibits clearance of respiratory syncytial virus: potential role of endogenous sialidase in antiviral immunity

The sialoglycosphingolipid GM1 is important for lipid rafts and immune cell signaling. T cell activation in vitro increases GM1 expression and increases endogenous sialidase activity. GM1 expression has been hypothesized to be regulated by endogenous sialidase. We tested this hypothesis in vivo using a mouse model of respiratory syncytial virus (RSV) infection. RSV infection increased endogenous sialidase activity in lung mononuclear cells. RSV infection increased lung CD8+ T cell surface GM1 expression. Activated CD8+ T cells in the lungs of RSV-infected mice were GM1(high). Treatment of RSV-infected mice with the sialidase/neuraminidase inhibitor oseltamivir decreased T cell surface GM1 levels. Oseltamivir treatment decreased RSV-induced weight loss and inhibited RSV clearance. Our data indicate a novel role for an endogenous sialidase in regulating T cell GM1 expression and antiviral immunity. Also, oseltamivir, an important anti-influenza drug, inhibits the clearance of a respiratory virus that lacks a neuraminidase gene, RSV.     

Effects of lysine clonixinate on cyclooxygenase I and II in rat lung and stomach preparations

Lysine clonixinate (LC) is a drug of antiinflammatory antipyretic and analgesic activity that produces minor digestive side-effects. This fact induced us to think that LC is possibly a weak COX-1 inhibitor. In order to investigate our hypothesis we inhibited cyclooxygenase activity with LC or indomethacin (INDO) in rat lung and stomach obtained from rats treated with lipopolysacharide (LPS) and control rats. Rat lung preparations incubated with 14C-arachidonic acid synthesise mainly PGE2. LC at 2.5 and 4.1 x 10(-5) M does not modify the basal production of PGE2 (probably COX-1) but at 6.8 x 10(-5) M significantly inhibited PGE2 production (approximately 48.5% inhibition, P<0.001). On the other hand, INDO at 10(-6) inhibited the basal production of PGE2 by around 73%. In LPS-treated rats, the production of PGE2 was significantly higher than in the lungs of control rats, probably due to the induction of COX-2. The addition of LC at 2.7 and 4.1 x 10(-5) M recovered the control values of PGE2 inhibiting, probably only from COX-2 activity. LC at higher concentrations (6.8 x 10(-5) M) and INDO 10(-6) M inhibited PGE2 formed by COX-2 and also partly by COX-1 activity.     

Venezuelan equine encephalitis virus replicon particles encoding respiratory syncytial virus surface glycoproteins induce protective mucosal responses in mice and cotton rats

Respiratory syncytial virus (RSV) is an important viral pathogen that causes severe lower respiratory tract infection in infants, the elderly, and immunocompromised individuals. There are no licensed RSV vaccines to date. To prevent RSV infection, immune responses in both the upper and lower respiratory tracts are required. Previously, immunization with Venezuelan equine encephalitis virus replicon particles (VRPs) demonstrated effectiveness in inducing mucosal protection against various pathogens. In this study, we developed VRPs encoding RSV fusion (F) or attachment (G) glycoproteins and evaluated the immunogenicity and efficacy of these vaccine candidates in mice and cotton rats. VRPs, when administered intranasally, induced surface glycoprotein-specific virus neutralizing antibodies in serum and immunoglobulin A (IgA) antibodies in secretions at the respiratory mucosa. In addition, fusion protein-encoding VRPs induced gamma interferon (IFN-γ)-secreting T cells in the lungs and spleen, as measured by reaction with an H-2K^d-restricted CD8⁺ T-cell epitope. In animals vaccinated with F protein VRPs, challenge virus replication was reduced below the level of detection in both the upper and lower respiratory tracts following intranasal RSV challenge, while in those vaccinated with G protein VRPs, challenge virus was detected in the upper but not the lower respiratory tract. Close examination of histopathology of the lungs of vaccinated animals following RSV challenge revealed no enhanced inflammation. Immunization with VRPs induced balanced Th1/Th2 immune responses, as measured by the cytokine profile in the lungs and antibody isotype of the humoral immune response. These results represent an important first step toward the use of VRPs encoding RSV proteins as a prophylactic vaccine for RSV.     

Differential Histopathology and Chemokine Gene Expression in Lung Tissues following Respiratory Syncytial Virus (RSV) Challenge of Formalin-Inactivated RSV- or BBG2Na-Immunized Mice

A BALB/c mouse model of enhanced pulmonary pathology following vaccination with formalin-inactivated alum-adsorbed respiratory syncytial virus (FI-RSV) and live RSV challenge was used to determine the type and kinetics of histopathologic lesions induced and chemokine gene expression profiles in lung tissues. These data were compared and contrasted with data generated following primary and/or secondary RSV infection or RSV challenge following vaccination with a promising subunit vaccine, BBG2Na. Severe peribronchiolitis and perivascularitis coupled with alveolitis and interstitial inflammation were the hallmarks of lesions in the lungs of FI-RSV-primed mice, with peak histopathology evident on days 5 and 9. In contrast, primary RSV infection resulted in no discernible lesions, while challenge of RSV-primed mice resulted in rare but mild peribronchiolitis and perivascularitis, with no evidence of alveolitis or interstitial inflammation. Importantly, mice vaccinated with a broad dose range (20 to 0.02 microg) of a clinical formulation of BBG2Na in aluminium phosphate demonstrated histopathology similar to that observed in secondary RSV infection. At the molecular level, FI-RSV priming was characterized by a rapid and strong up-regulation of eotaxin and monocyte chemotactic protein 3 (MCP-3) relative gene expression (potent lymphocyte and eosinophil chemoattractants) that was sustained through late time points, early but intermittent up-regulation of GRO/melanoma growth stimulatory activity gene and inducible protein 10 gene expression, while macrophage inflammatory protein 2 (MIP-2) and especially MCP-1 were up-regulated only at late time points. By comparison, primary RSV infection or BBG2Na priming resulted in considerably lower eotaxin and MCP-3 gene expression increases postchallenge, while expression of lymphocyte or monocyte chemoattractant chemokine genes (MIP-1beta, MCP-1, and MIP-2) were of higher magnitude and kinetics at early, but not late, time points. Our combined histopathologic and chemokine gene expression data provide a basis for differentiating between aberrant FI-RSV-induced immune responses and normal responses associated with RSV infection in the mouse model. Consequently, our data suggest that BBG2Na may constitute a safe RSV subunit vaccine for use in seronegative infants.     

Anti-inflammatory effect of two isoforms of COX in H. pylori-induced gastritis in mice: possible involvement of PGE2

Neutrophil infiltration mediated by TNF-alpha is associated with various types of gastric injury, whereas PGs play a crucial role in gastric defense. We examined roles of two isoforms of cyclooxygenase (COX) and PGE2 in Helicobacter pylori-induced gastritis in mice. Mice infected with H. pylori were given selective COX-1 inhibitor SC-560 (10 mg/kg), selective COX-2 inhibitor NS-398 (10 mg/kg), or nonselective COX inhibitor indomethacin (2 mg/kg) with or without 16,16-dimethyl PGE2 for 1 wk. H. pylori infection increased levels of mRNA for COX-1 and -2 in gastric tissue by 1.2-fold and 3.3-fold, respectively, accompanied by a significant increase in PGE2 production by gastric tissue. H. pylori infection significantly elevated MPO activity, a marker of neutrophil infiltration, and epithelial cell apoptosis in the stomach. SC-560 augmented MPO activity and epithelial cell apoptosis with associated reduction in PGE2 production, whereas NS-398 had the same effects without affecting PGE2 production. Inhibition of both COX-1 and -2 by indomethacin or concurrent treatment with SC-560 and NS-398 resulted in a stronger increase in MPO activity and apoptosis than inhibition of either COX-1 or -2 alone. H. pylori infection elevated TNF-alpha mRNA expression in the stomach, which was further increased by indomethacin. Effects of COX inhibitors on neutrophil infiltration, apoptosis, and TNF-alpha expression in H. pylori-infected mice were abolished by exogenous 16,16-dimethyl PGE2. In conclusion, PGE2 derived from either COX-1 or -2 is involved in regulation of gastric mucosal inflammation and contributes to maintenance of mucosal integrity during H. pylori infection via inhibition of TNF-alpha expression.     

Respiratory syncytial virus infection is associated with an altered innate immunity and a heightened pro-inflammatory response in the lungs of preterm lambs

Introduction

Factors explaining the greater susceptibility of preterm infants to severe lower respiratory infections with respiratory syncytial virus (RSV) remain poorly understood. Fetal/newborn lambs are increasingly appreciated as a model to study key elements of RSV infection in newborn infants due to similarities in lung alveolar development, immune response, and susceptibility to RSV. Previously, our laboratory demonstrated that preterm lambs had elevated viral antigen and developed more severe lesions compared to full-term lambs at seven days post-infection. Here, we compared the pathogenesis and immunological response to RSV infection in lungs of preterm and full-term lambs.

Methods

Lambs were delivered preterm by Caesarian section or full-term by natural birth, then inoculated with bovine RSV (bRSV) via the intratracheal route. Seven days post-infection, lungs were collected for evaluation of cytokine production, histopathology and cellular infiltration.

Results

Compared to full-term lambs, lungs of preterm lambs had a heightened pro-inflammatory response after infection, with significantly increased MCP-1, MIP-1α, IFN-γ, TNF-α and PD-L1 mRNA. RSV infection in the preterm lung was characterized by increased epithelial thickening and periodic acid-Schiff staining, indicative of glycogen retention. Nitric oxide levels were decreased in lungs of infected preterm lambs compared to full-term lambs, indicating alternative macrophage activation. Although infection induced significant neutrophil recruitment into the lungs of preterm lambs, neutrophils produced less myeloperoxidase than those of full-term lambs, suggesting decreased functional activation.

Conclusions

Taken together, our data suggest that increased RSV load and inadequate immune response may contribute to the enhanced disease severity observed in the lungs of preterm lambs.     

Visualization and characterization of respiratory syncytial virus F-specific CD8(+) T cells during experimental virus infection

CTL play a major role in the clearance of respiratory syncytial virus (RSV) during experimental pulmonary infection. The fusion (F) glycoprotein of RSV is a protective Ag that elicits CTL and Ab response against RSV infection in BALB/c mice. We used the strategy of screening a panel of overlapping synthetic peptides corresponding to the RSV F protein and identified an immunodominant H-2K(d)-restricted epitope (F(85-93); KYKNAVTEL) recognized by CD8(+) T cells from BALB/c mice. We enumerated the F-specific CD8(+) T cell response in the lungs of infected mice by flow cytometry using tetramer staining and intracellular cytokine synthesis. During primary infection, F(85-93)-specific effector CD8(+) T cells constitute approximately 4.8% of pulmonary CD8(+) T cells at the peak of the primary response (day 8), whereas matrix 2-specific CD8(+) T cells constituted approximately 50% of the responding CD8(+) T cell population in the lungs. When RSV F-immune mice undergo a challenge RSV infection, the F-specific CD8(+) T cell response is accelerated and dominates, whereas the primary response to the matrix 2 epitope in the lungs is reduced by approximately 20-fold. In addition, we found that activated F-specific effector CD8(+) T cells isolated from the lungs of RSV-infected mice exhibited a lower than expected frequency of IFN-gamma-producing CD8(+) T cells and were significantly impaired in ex vivo cytolytic activity compared with competent F-specific effector CD8(+) T cells generated in vitro. The significance of these results for the regulation of the CD8(+) T cell response to RSV is discussed.     

抗生素诱导的呼吸道菌群缺失对小鼠RSV感染的影响

目的 探究抗生素雾化暴露引起的呼吸道菌群缺失对小鼠呼吸道合胞病毒(RSV)感染的影响,为临床合理使用抗生素提供指导意见.方法32只BALB/c小鼠分为2组:雾化ddH2O对照组和雾化ABX组合抗生素组,处理6 d后,进行细菌16S rRNA基因PCR检测,构建呼吸道菌群缺失小鼠模型.上述2组组内再随机分为2小组,即PB...     

Low-molecular-weight heparin reduces hyperoxia-augmented ventilator-induced lung injury via serine/threonine kinase-protein kinase B

Introduction

Factors explaining the greater susceptibility of preterm infants to severe lower respiratory infections with respiratory syncytial virus (RSV) remain poorly understood. Fetal/newborn lambs are increasingly appreciated as a model to study key elements of RSV infection in newborn infants due to similarities in lung alveolar development, immune response, and susceptibility to RSV. Previously, our laboratory demonstrated that preterm lambs had elevated viral antigen and developed more severe lesions compared to full-term lambs at seven days post-infection. Here, we compared the pathogenesis and immunological response to RSV infection in lungs of preterm and full-term lambs.

Methods

Lambs were delivered preterm by Caesarian section or full-term by natural birth, then inoculated with bovine RSV (bRSV) via the intratracheal route. Seven days post-infection, lungs were collected for evaluation of cytokine production, histopathology and cellular infiltration.

Results

Compared to full-term lambs, lungs of preterm lambs had a heightened pro-inflammatory response after infection, with significantly increased MCP-1, MIP-1α, IFN-γ, TNF-α and PD-L1 mRNA. RSV infection in the preterm lung was characterized by increased epithelial thickening and periodic acid-Schiff staining, indicative of glycogen retention. Nitric oxide levels were decreased in lungs of infected preterm lambs compared to full-term lambs, indicating alternative macrophage activation. Although infection induced significant neutrophil recruitment into the lungs of preterm lambs, neutrophils produced less myeloperoxidase than those of full-term lambs, suggesting decreased functional activation.

Conclusions

Taken together, our data suggest that increased RSV load and inadequate immune response may contribute to the enhanced disease severity observed in the lungs of preterm lambs.     

COX-2 induction during murine gammaherpesvirus 68 infection leads to enhancement of viral gene expression

The murine gammaherpesvirus 68 (MHV-68 or gammaHV-68) model provides many advantages for studying virus-host interactions involved in gammaherpesvirus replication, including the role of cellular responses to infection. We examined the effects of cellular cyclooxygenase-2 (COX-2) and its by-product prostaglandin E(2) (PGE(2)) on MHV-68 gene expression and protein production following de novo infection of cultured cells. Western blot analyses revealed an induction of COX-2 protein in MHV-68-infected cells but not in cells infected with UV-irradiated MHV-68. Luciferase reporter assays demonstrated activation of the COX-2 promoter during MHV-68 replication. Two nonsteroidal anti-inflammatory drugs, a COX-2-specific inhibitor (NS-398) and a COX-1-COX-2 inhibitor (indomethacin), substantially reduced MHV-68 protein production in infected cells. Inhibition of viral protein expression and virion production by NS-398 was reversed in the presence of exogenous PGE(2). Global gene expression analysis using an MHV-68 DNA array showed that PGE(2) increased production of multiple viral gene products, and NS-398 inhibited production of many of the same genes. These studies suggest that COX-2 activity and PGE(2) production may play significant roles during MHV-68 de novo infection.