Respiratory syncytial virus persistent infection causes acquired CFTR dysfunction in human bronchial epithelial cells

OBJECTIVES

Many studies have shown that respiratory syncytial virus persistent infection may be the main cause of chronic respiratory pathology.However, the mechanism is unclear. Cystic fibrosis transmembrane conduction regulator (CFTR) is an apical membrane chloride channel, which is very important for the regulation of epithelial fluid, chloride ion, and bicarbonate transport. CFTR dysfunction will lead to changes in bronchial secretions and impair mucus clearance, which is related to airway inflammation. In our previous study, we observed the down-regulation of CFTR in airway epithelial cells in respiratory syncytial virus (RSV) infected mouse model. In this study, we further investigated the expression and function of CFTR by constructing an airway epithelial cell model of RSV persistent infection.

METHODS

16HBE14o- cells were infected with RSV at 0.01 multiplicity of infection (MOI). The expression of CFTR was detected by real-time RT-PCR, immunofluorescence, and Western blotting. The intracellular chloride concentration was measured by N-(ethoxycarbonylmethyl)-6-methoxyquinolium bromide (MQAE) and the chloride current was measured by whole-cell patch clamp recording.

RESULTS

16HBE14o- cells infected with RSV were survived to successive passages of the third generation (G3), while the expression and function of CFTR was progressively decreased upon RSV infection from the first generation (G1) to G3. Exposure of 16HBE14o- cells to RSV led to the gradual increase of TGF-β1 as well as phosphorylation of Smad2 following progressive RSV infection. Disruption of TGF-β1 signaling by SB431542 prevented Smad2 phosphorylation and rescued the expression of CFTR.

CONCLUSIONS

RSV infection can lead to defective CFTR function in airway epithelial cells, which may be mediated via activation of TGF-β1 signaling pathway.

Pulmonary function analysis in cotton rats after respiratory syncytial virus infection

The cotton rat (Sigmodon hispidus) is an excellent small animal model for human respiratory viral infections such as human respiratory syncytial virus (RSV) and human metapneumovirus (HMPV). These respiratory viral infections, as well as other pulmonary inflammatory diseases such as asthma, are associated with lung mechanic disturbances. So far, the pathophysiological effects of viral infection and allergy on cotton rat lungs have not been measured, although this information might be an important tool to determine the efficacy of vaccine and drug candidates. To characterize pulmonary function in the cotton rat, we established forced oscillation technique in uninfected, RSV infected and HDM sensitized cotton rats, and characterized pulmonary inflammation, mucus production, pulmonary edema, and oxygenation. There was a gender difference after RSV infection, with females demonstrating airway hyper-responsiveness while males did not. Female cotton rats 2dpi had a mild increase in pulmonary edema (wet: dry weight ratios). At day 4 post infection, female cotton rats demonstrated mild pulmonary inflammation, no increase in mucus production or reduction in oxygenation. Pulmonary function was not significantly impaired after RSV infection. In contrast, cotton rats sensitized to HDM demonstrated airway hyper-responsiveness with a significant increase in pulmonary inflammation, increase in baseline tissue damping, and a decrease in baseline pulmonary compliance. In summary, we established baseline data for forced oscillation technique and other respiratory measures in the cotton rat and used it to analyze respiratory diseases in cotton rats.

Respiratory Virus Infections in Asthma: Research Developments and Therapeutic Advances

In this review, we discuss the latest developments in research pertaining to virus-induced asthma exacerbations and consider recent advances in treatment options. Asthma is a chronic disease of the airways that continues to impose a substantial clinical burden worldwide. Asthma exacerbations, characterised by an acute deterioration in respiratory symptoms and airflow obstruction, are associated with significant morbidity and mortality. These episodes are most commonly triggered by respiratory virus infections. The mechanisms underlying the pathogenesis of virus-induced exacerbations have been the focus of extensive biomedical research. Developing a robust understanding of the interplay between respiratory viruses and the host immune response will be critical for developing more efficacious, targeted therapies for exacerbations. CONCLUSION: There has been significant recent progress in our understanding of the mechanisms underlying virus-induced airway inflammation in asthma and these advances will underpin the development of future clinical therapies.

The impact of viral bronchiolitis phenotyping: Is it time to consider phenotype-specific responses to individualize pharmacological management?

Although recent guidelines recommend a minimalist approach to bronchiolitis, there are several issues with this posture. First, there are concerns about the definition of the disease, the quality of the guidelines, the method of administration of bronchodilators, and the availability of tools to evaluate the response to therapies. Second, for decades it has been assumed that all cases of viral bronchiolitis are the same, but recent evidence has shown that this is not the case. Distinct bronchiolitis phenotypes have been described, with heterogeneity in clinical presentation, molecular immune signatures and clinically relevant outcomes such as respiratory failure and recurrent wheezing. New research is critically needed to refine viral bronchiolitis phenotyping at the molecular and clinical levels as well as to define phenotype-specific responses to different therapeutic options.

Pathogenesis of Respiratory Syncytial Virus Infection in BALB/c Mice Differs Between Intratracheal and Intranasal Inoculation

Human respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract disease requiring hospitalization in infants. There are no market-approved vaccines or antiviral agents available, but a growing number of vaccines and therapeutics are in (pre)clinical stages of development. Reliable animal models are crucial to evaluate new vaccine concepts, but in vivo RSV research is hampered by the lack of well-characterized animal models that faithfully mimic the pathogenesis of RSV infection in humans. Mice are frequently used in RSV infection and vaccination studies. However, differences in the use of mouse strains, RSV subtypes, and methodology often lead to divergent study outcomes. To our knowledge, a comparison between different RSV inoculation methods in mice has not been described in the literature, even though multiple methods are being used across different studies. In this study, we evaluated various pathological and immunological parameters in BALB/c mice after intratracheal or intranasal inoculation with RSV-A2. Our study reveals that intranasal inoculation induces robust pathology and inflammation, whereas this is not the case for intratracheal inoculation. As immunopathology is an important characteristic of RSV disease in infants, these data suggest that in mice intranasal inoculation is a more appropriate method to study RSV infection than intratracheal inoculation. These findings will contribute to the rational experimental design of future in vivo RSV experiments.

The ABCs of RSV

Respiratory syncytial virus (RSV) is a common viral infection affecting many children in the United States. This seasonal virus is the leading cause of hospitalization of infants and neonates. This article reviews the current recommendations for diagnostic testing, treatment options, and prevention of RSV.

The human viral challenge model: accelerating the evaluation of respiratory antivirals, vaccines and novel diagnostics

The Human Viral Challenge (HVC) model has, for many decades, helped in the understanding of respiratory viruses and their role in disease pathogenesis. In a controlled setting using small numbers of volunteers removed from community exposure to other infections, this experimental model enables proof of concept work to be undertaken on novel therapeutics, including vaccines, immunomodulators and antivirals, as well as new diagnostics.Crucially, unlike conventional phase 1 studies, challenge studies include evaluable efficacy endpoints that then guide decisions on how to optimise subsequent field studies, as recommended by the FDA and thus licensing studies that follow. Such a strategy optimises the benefit of the studies and identifies possible threats early on, minimising the risk to subsequent volunteers but also maximising the benefit of scarce resources available to the research group investing in the research. Inspired by the principles of the 3Rs (Replacement, Reduction and Refinement) now commonly applied in the preclinical phase, HVC studies allow refinement and reduction of the subsequent development phase, accelerating progress towards further statistically powered phase 2b studies. The breadth of data generated from challenge studies allows for exploration of a wide range of variables and endpoints that can then be taken through to pivotal phase 3 studies.We describe the disease burden for acute respiratory viral infections for which current conventional development strategies have failed to produce therapeutics that meet clinical need. The Authors describe the HVC model's utility in increasing scientific understanding and in progressing promising therapeutics through development.The contribution of the model to the elucidation of the virus-host interaction, both regarding viral pathogenicity and the body's immunological response is discussed, along with its utility to assist in the development of novel diagnostics.Future applications of the model are also explored.

IL-17 Plays a Role in Respiratory Syncytial Virus-induced Lung Inflammation and Emphysema in Elastase and LPS-injured Mice

Respiratory syncytial virus (RSV) is associated with enhanced progression of chronic obstructive pulmonary disease (COPD) and COPD exacerbations. However, little is known about the role of IL-17 in RSV-induced lung injury. We first investigated the role of RSV infection in enhancing mucous cell hyperplasia (MCH) and airspace enlargement in the lungs of mice injured with elastase and LPS (E/LPS). Mice injured with E/LPS had an enhanced and prolonged neutrophilic response to RSV that was associated with decreased levels of type I IFN and increased levels of IL-17, IL-23, CXCL-1, granulocyte colony stimulating factor (GCSF), CXCL-5, and matrix metalloproteinase (MMP)-9. In addition, extent of MCH and mean weighted alveolar space were increased significantly in the lungs of E/LPS-injured mice infected with RSV compared with E/LPS-only or RSV-only controls. Interestingly, immunodepletion of IL-17 before viral infection diminished the RSV-driven MCH and airspace enlargement in the E/LPS-injured animals, suggesting that IL-17 may be a therapeutic target for MCH and airspace enlargement when enhanced by RSV infection.

Respiratory syncytial virus prolifically infects N2a neuronal cells, leading to TLR4 and nucleolin protein modulations and RSV F protein co-localization with TLR4 and nucleolin

BACKGROUND

Respiratory syncytial virus (RSV) infects the central nervous system, resulting in neurological symptoms. However, the precise underlying pathogenic mechanisms have not been elucidated. In the present study, the infectivity of RSV on N2a neuronal cells and the possible roles of Toll-like receptor 4 (TLR4) and nucleolin (C23) during RSV infection were investigated.

METHODS

We compared two experimental groups (infected and non-infected) and monitored the RSV viral titers in the culture supernatant by a viral plaque assay. We also inspected the morphology of the nucleus in infected N2a cells. We measured the level of RSV F protein and studied its co-localization with TLR4 and nucleolin using immunofluorescence assays and laser confocal microscopy. The potential interaction of RSV F protein with TLR4 and nucleolin was examined by coimmunoprecipitation. The expression changes of TLR4, nucleolin, TLR3 and TLR7 proteins in N2a cells and IL-6 and TNF-α in the culture supernatant were investigated by Western Blot analysis and ELISA assay. Changes in neuronal cell apoptosis status was examined by flow cytometry.

RESULTS

The results demonstrated prolific RSV infection of N2a cells, which triggered a decrease of NeuN protein expression, coinciding with an increase of nuclear lesions, F protein expression, RSV viral titers, and late apoptotic levels of N2a cells. RSV infection induced co-localization of RSV F protein with TLR4 and nucleolin, which could potentially lead to a direct interaction. Furthermore, it was found that TLR4 and nucleolin levels increased early after infection and decreased subsequently, whereas TLR3 and TLR7 expression increased throughout RSV infection.

CONCLUSION

The RSV Long strain can prolifically infect N2a neuronal cells, modulating the expression of TLR4 and nucleolin, as well as TLR3, TLR7 and their downstream inflammatory factors, and inducing the co-localization of the RSV F protein with TLR4 and nucleolin.

Acute necrotising encephalopathy of childhood: A review of two cases

Acute necrotising encephalopathy of childhood (ANEC) is an uncommon disease with characteristic clinical and imaging findings. We present two cases of ANEC secondary to Respiratory Syncytial Virus (RSV) and mycoplasma infections. An eight-month-old boy presented with features of gastroenteritis but soon developed multiple episodes of seizures. Blood and CSF cultures were negative but nasopharyngeal aspirate immunofluorescence was positive for RSV. A nine-year-old girl presented with abnormal behaviour following two days of prodromal symptoms. Her serological markers implicated mycoplasma (IgM titre 1: 640). CT brain of both patients showed bilateral symmetrical thalamic hypodensities, while MRI revealed more extensive white matter involvements.

Prenatal Exposure to Respiratory Syncytial Virus Alters Postnatal Immunity and Airway Smooth Muscle Contractility during Early-Life Reinfections

Maternal viral infections can have pathological effects on the developing fetus which last long after birth. Recently, maternal-fetal transmission of respiratory syncytial virus (RSV) was shown to cause postnatal airway hyperreactivity (AHR) during primary early-life reinfection; however, the influence of prenatal exposure to RSV on offspring airway immunity and smooth muscle contractility during recurrent postnatal reinfections remains unknown. Therefore, we sought to determine whether maternal RSV infection impairs specific aspects of cell-mediated offspring immunity during early-life reinfections and the mechanisms leading to AHR. Red fluorescent protein-expressing recombinant RSV (rrRSV) was inoculated into pregnant rat dams at midterm, followed by primary and secondary postnatal rrRSV inoculations of their offspring at early-life time points. Pups and weanlings were tested for specific lower airway leukocyte populations by flow cytometry; serum cytokine/chemokine concentrations by multiplex ELISA and neurotrophins concentrations by standard ELISA; and ex vivo lower airway smooth muscle (ASM) contraction by physiological tissue bath. Pups born to RSV-infected mothers displayed elevated total CD3+ T cells largely lacking CD4+ and CD8+ surface expression after both primary and secondary postnatal rrRSV infection. Cytokine/chemokine analyses revealed reduced IFN-γ, IL-2, IL-12, IL-17A, IL-18, and TNF-α, as well as elevated nerve growth factor (NGF) expression. Prenatal exposure to RSV also increased ASM reactivity and contractility during early-life rrRSV infection compared to non-exposed controls. We conclude that maternal RSV infection can predispose offspring to postnatal lower airways dysfunction by altering immunity development, NGF signaling, and ASM contraction during early-life RSV reinfections.

Gu-Ben-Fang-Xiao decoction attenuates sustained airway inflammation by suppressing ER stress response in a murine asthma remission model of respiratory syncytial virus infection

ETHNOPHARMACOLOGICAL RELEVANCE

In recent years, asthma has increased dramatically in prevalence with a considerable economic burden all over the world. Long-term remission should be regarded as the promising and meaningful therapeutic goal in asthma management. However, the precise definition criteria and rational therapies for asthma remission have not been well-established. In academia, there is a consensus that even in those who develop asymptomatic remission of asthma, persistent airway inflammation is ubiquitous. Gubenfangxiao decoction (GBFXD) has been widely used in treating asthma remission stage for decades in the Jiangsu Province Hospital of Chinese Medicine, China. We previously demonstrated that GBFXD could downregulate the asthma susceptibility gene ORMDL3, a trigger of Endoplasmic reticulum (ER) stress and unfolded protein response (UPR).

AIM THIS STUDY

To investigate the involvement of ER stress and UPR in the anti-inflammatory effects of GBFXD in Respiratory Syncytial Virus (RSV)-OVA-induced asthma remission mice.

MATERIALS AND METHODS

Mice were orally administered GBFXD at three doses for 30 days after an RSV-OVA challenge. The levels of inflammation mediators in serum were measured using a Luminex assay and the amount of IFN-γ in lung homogenates was detected using ELISA. The splenic CD4+ and CD8+ T lymphocytes were counted using flow cytometric analysis. The mRNA and protein levels of asthma susceptibility gene ORMDL3, ER stress markers (BIP, CHOP), and three canonical UPR branches (PERK-eIF2a-ATF4, IRE1α-XBP1/IRE1α-JNK-AP1 and ATF6-SERCA2b signal pathways) were detected using real-time RT-PCR and western blot.

RESULTS

Histopathological analysis showed that the model group mice still exhibited a sustained airway inflammation even after suspending the OVA-challenge and RSV infections for 30 days. H&E staining results indicated that GBFXD could attenuate sustained airway inflammation. Decreased serum CXCL1 level and increased IFN-γ level in lung homogenate were observed after GBFXD treatment. Reductions in the number of splenic CD4+/CD8+ T lymphocytes were found after DEX treatment. We further confirmed the previous finding that GBFXD could downregulate the expression of ORMDL3. As a result of suppressed UPR, decreased ER stress markers and inhibited UPR branches (PERK and IRE1α signal pathway) were also observed through the significant reduction of signature mRNA and protein expressions after GBFXD treatment.

CONCLUSION

GBFXD can significantly attenuate RSV-OVA-induced persistent airway inflammation in murine asthma remission model. These effects may be mediated, at least partially, by inhibiting the activation of ER stress responses.

Long-Term Burden and Respiratory Effects of Respiratory Syncytial Virus Hospitalization in Preterm Infants-The SPRING Study

The health status of premature infants born 32¹-35⁰ weeks’ gestational age (wGA) hospitalized for RSV infection in the first year of life (cases; n = 125) was compared to that of premature infants not hospitalized for RSV (controls; n = 362) through 6 years. The primary endpoints were the percentage of children with wheezing between 2-6 years and lung function at 6 years of age. Secondary endpoints included quality of life, healthcare resource use, and allergic sensitization. A significantly higher proportion of cases than controls experienced recurrent wheezing through 6 years of age (46.7% vs. 27.4%; p = 0.001). The vast majority of lung function tests appeared normal at 6 years of age in both cohorts. In children with pulmonary function in the lower limit of normality (FEV₁ Z-score [-2; -1]), wheezing was increased, particularly for cases vs. controls (72.7% vs. 18.9%, p = 0.002). Multivariate analysis revealed the most important factor for wheezing was RSV hospitalization. Quality of life on the respiratory subscale of the TAPQOL was significantly lower (p = 0.001) and healthcare resource utilization was significantly higher (p<0.001) in cases than controls. This study confirms RSV disease is associated with wheezing in 32-35 wGA infants through 6 years of age.

Recent evidence on the management of bronchiolitis

PURPOSE OF REVIEW

Bronchiolitis is a common condition in children less than 2  years of age and is a leading cause of infant hospitalization. Although there is significant variability in testing and treatment of children with bronchiolitis, diagnostic testing rarely improves care, and no currently available pharmacologic options have been proven to provide meaningful benefits or improve outcomes.

RECENT FINDINGS

Beta-agonists continue to be used frequently despite evidence that they do not reduce hospital admissions or length of stay. In general, therapies initially considered promising were subsequently proven ineffective, a pattern seen in studies on corticosteroids, and more recently with nebulized racemic epinephrine and hypertonic saline. Recent research has improved our understanding of the viral epidemiology of bronchiolitis, with increasing recognition of viruses other than respiratory syncytial virus and better awareness of the role of viral coinfections. How these findings will translate into improved outcomes remains uncertain.

SUMMARY

Much of the emphasis of the last few decades of bronchiolitis clinical care and research has centered on the identification and testing of novel therapies. Future quality improvement efforts should focus more on the limitation of unnecessary testing and treatments. Future research should include identification of subgroups of children with bronchiolitis that may benefit from focused clinical interventions.

[Expression of heparanase in kidney of rats with respiratory syncytial virus nephropathy and its relationship with proteinurina]

OBJECTIVE

To explore the role of heparanase in the pathogenesis of respiratory syncytial virus (RSV) nephropathy in rats model.

METHODS

Twenty 150-200 g Sprague-Dawley (SD) rats (n = 5 per group) were inoculated with 6 x 10(6) PFU RSV and sacrificed on days 4, 8, 14 and 28 postinoculation (RSV4, RSV8, RSV14 and RSV29). Five SD rats inoculated with Dulbecco's minimum essential medium were served as normal control. The expression levels of heparanase protein and mRNA in the rat renal tissue of each group were determined by immunohistochemical staining and real-time quantitative RT-PCR respectively. The proteinurina was also measured and then the relationship between the expression level of heparanase and the 24-hour urinary protein was studied.

RESULTS

The rats with RSV nephropathy exhibited higher proteinuria in comparison with normal rats, and the 24-hour urinary protein level was significantly different between each RSV nephropathy group (RSV14 > RSV8 > RSV28 > RSV4, P < 0.05). Compared with normal control, the rats with RSV nephropathy showed up-regulated expression of heparanase protein in glomeruli. The expression levels of heparanase protein in RSV8 and RSV14 group were higher than those in RSV4 and RSV28 group (P < 0.05). There was a linear positive correlation between the expression level of glomerular heparanase protein and the quantity of 24-hour urinary protein (r = 0.783, P < 0.05). Compared with normal control group, the expression levels of heparanase mRNA in the kidney from RSV4, RSV8, RSV14, and RSV28 group were elevated (RSV14 > RSV8 > RSV4 > RSV28 , P < 0.05). There was a linear positive correlation between the expression level of renal heparanase mRNA and the quantity of 24-hour urinary protein (r = 0.725, P < 0.05).

CONCLUSION

The increased expression of heparanase in kidney may be important to the loss of glomerular negative charge in glomerular basement membrane which is involved in the pathogenesis of RSV nephropathy in rats.

Respiratory syncytial virus infections enhance cigarette smoke induced COPD in mice

Respiratory syncytial viral (RSV) infections are a frequent cause of chronic obstructive pulmonary disease (COPD) exacerbations, which are a major factor in disease progression and mortality. RSV is able to evade antiviral defenses to persist in the lungs of COPD patients. Though RSV infection has been identified in COPD, its contribution to cigarette smoke-induced airway inflammation and lung tissue destruction has not been established. Here we examine the long-term effects of cigarette smoke exposure, in combination with monthly RSV infections, on pulmonary inflammation, protease production and remodeling in mice. RSV exposures enhanced the influx of macrophages, neutrophils and lymphocytes to the airways of cigarette smoke exposed C57BL/6J mice. This infiltration of cells was most pronounced around the vasculature and bronchial airways. By itself, RSV caused significant airspace enlargement and fibrosis in mice and these effects were accentuated with concomitant smoke exposure. Combined stimulation with both smoke and RSV synergistically induced cytokine (IL-1α, IL-17, IFN-γ, KC, IL-13, CXCL9, RANTES, MIF and GM-CSF) and protease (MMP-2, -8, -12, -13, -16 and cathepsins E, S, W and Z) expression. In addition, RSV exposure caused marked apoptosis within the airways of infected mice, which was augmented by cigarette smoke exposure. RSV and smoke exposure also reduced protein phosphatase 2A (PP2A) and protein tyrosine phosphates (PTP1B) expression and activity. This is significant as these phosphatases counter smoke-induced inflammation and protease expression. Together, these findings show for the first time that recurrent RSV infection markedly enhances inflammation, apoptosis and tissue destruction in smoke-exposed mice. Indeed, these results indicate that preventing RSV transmission and infection has the potential to significantly impact on COPD severity and progression.

Respiratory syncytial virus (RSV) infection in elderly mice results in altered antiviral gene expression and enhanced pathology

Elderly persons are more susceptible to RSV-induced pneumonia than young people, but the molecular mechanism underlying this susceptibility is not well understood. In this study, we used an aged mouse model of RSV-induced pneumonia to examine how aging alters the lung pathology, modulates antiviral gene expressions, and the production of inflammatory cytokines in response to RSV infection. Young (2-3 months) and aged (19-21 months) mice were intranasally infected with mucogenic or non-mucogenic RSV strains, lung histology was examined, and gene expression was analyzed. Upon infection with mucogenic strains of RSV, leukocyte infiltration in the airways was elevated and prolonged in aged mice compared to young mice. Minitab factorial analysis identified several antiviral genes that are influenced by age, infection, and a combination of both factors. The expression of five antiviral genes, including pro-inflammatory cytokines IL-1β and osteopontin (OPN), was altered by both age and infection, while age was associated with the expression of 15 antiviral genes. Both kinetics and magnitude of antiviral gene expression were diminished as a result of older age. In addition to delays in cytokine signaling and pattern recognition receptor induction, we found TLR7/8 signaling to be impaired in alveolar macrophages in aged mice. In vivo, induction of IL-1β and OPN were delayed but prolonged in aged mice upon RSV infection compared to young. In conclusion, this study demonstrates inherent differences in response to RSV infection in young vs. aged mice, accompanied by delayed antiviral gene induction and cytokine signaling.

Increased risk of wheeze and decreased lung function after respiratory syncytial virus infection

Background

A relationship between hospitalization for respiratory syncytial virus (RSV) bronchiolitis and asthma development has been suggested in case-control studies.

Objective

The aim of this study was to assess the risk of current wheeze, asthma, and lung function at school age in infants previously hospitalized for RSV bronchiolitis compared to non-hospitalized children.

Methods

For this study, data from a prospective birth cohort of unselected, term-born infants (n = 553), of whom 4 (0.7%) were hospitalized for RSV bronchiolitis, and a prospective patient cohort of 155 term infants hospitalized for RSV bronchiolitis were used. Respiratory outcomes at age 6 in children hospitalized for RSV bronchiolitis were compared to non-hospitalized children.

Results

The risk of current wheeze was higher in hospitalized patients (n = 159) compared to non-hospitalized children (n = 549) (adjusted odds ratio (OR) 3.2 (95% CI 1.2–8.1). Similarly, the risk of current asthma, defined as a doctor’s diagnosis of asthma plus current symptoms or medication use, was higher in hospitalized patients (adjusted OR 3.1 (95% CI 1.3–7.5). Compared to non-hospitalized children, RSV bronchiolitis hospitalization was associated with lower lung function (mean difference FEV1% predicted −6.8 l (95% CI (−10.2 to −3.4).

Conclusions and Clinical Relevance

This is the first study showing that hospitalization for RSV bronchiolitis during infancy is associated with increased risk of wheezing, current asthma, and impaired lung function as compared to an unselected birth cohort at age 6.

A passive quantitative measurement of airway resistance using depth data

The Respiratory Syncytial Virus (RSV) is the most common cause of serious lower respiratory tract infections in infants and young children. RSV often causes increased airway resistance, clinically detected as wheezing by chest auscultation. In this disease, expiratory flows are significantly reduced due to the high resistance in patient's airway passages. A quantitative method for measuring resistance can have a great benefit to diagnosis and management of children with RSV infections as well as with other lung diseases. Airway resistance is defined as the lung pressure divided by the airflow. In this paper, we propose a method to quantify resistance through a simple, non-contact measurement of chest volume that can act as a surrogate measure of the lung pressure and volumetric airflow. We used depth data collected by a Microsoft Kinect camera for the measurement of the lung volume over time. In our experimentation, breathing through a number of plastic straws induced different airway resistances. For a standard spirometry test, our volume/flow estimation using Kinect showed strong correlation with the flow data collected by a commercially-available spirometer (five subjects, each performing 20 breathing trials, correlation coefficient = 0.88, with 95% confidence interval). As the number of straws decreased, emulating a higher airway obstruction, our algorithm was sufficient to distinguish between several levels of airway resistance.

Measurement of the innate immune response in the airway

Asthma is an idiopathic disease associated with episodic inflammation and reversible airway obstruction that is triggered by environmental agents. Allergic and infectious agents trigger asthmatic exacerbations through the innate immune response (IIR). The IIR is activated by sentinel cells in the airways to elaborate inflammatory cytokines and protective mucosal interferons whose actions are designed to limit the spread of the organism, as well as to activate the adaptive immune response. We address the structure of the IIR pathway in sentinel cells of the airway and describe observations on its dysregulation. The IIR is triggered in a cell-type specific manner by germline-encoded pathogen recognition receptors (PPRs) including plasma membrane Toll-like receptors (TLRs) and the cytoplasmic Retinoic Acid-inducible Gene (RIG)-I-like RNA helicases, and protein kinase R (PKR). Although their mechanisms of intracellular signaling differ, both pathways converge on a small group of transcriptional effectors, nuclear factor-κB (NF-κB), IFN regulatory factor (IRF), and signal transducer and activator of transcription (STAT). We describe several distinct techniques to quantitate the IIR including assays based on quantitative real-time PCR (Q-RT-PCR) of NF-κB and IRF3-regulated genes, multiplex bead-based analysis of secreted proteins/cytokines and more recent developments in targeted, quantitative selected reaction monitoring (SRM)-mass spectrometry (MS). Application of these methods for quantitation of the IIR will further our understanding of the role of the IIR in asthma and its contribution to disease heterogeneity.

Lamb model of respiratory syncytial virus-associated lung disease: insights to pathogenesis and novel treatments

Preterm birth is a risk factor for respiratory syncytial virus (RSV) bronchiolitis and hospitalization. The pathogenesis underlying this is not fully understood, and in vivo studies are needed to better clarify essential cellular features and molecular mechanisms. Such studies include analysis of lung tissue from affected human infants and various animal models. The preterm and newborn lamb lung has developmental, structural, cellular, physiologic, and immunologic features similar to that of human infants. Also, the lamb lung is susceptible to various strains of RSV that infect infants and cause similar bronchiolar lesions. Studies in lambs suggest that viral replication in airways (especially bronchioles) is extensive by 4 days after infection, along with bronchiolitis characterized by degeneration and necrosis of epithelial cells, syncytial cell formation, neutrophil infiltration, epithelial cell hypertrophy and hyperplasia, and innate and adaptive immune responses. RSV bronchiolitis greatly affects airflow and gaseous exchange. RSV disease severity is increased in preterm lambs compared with full-term lambs; similar to human infants. The lamb is conducive to experimental assessment of novel, mechanistic therapeutic interventions such as delivery of vascular endothelial growth factor and enhancement of airway epithelial oxidative responses, Club (Clara) cell protein 10, and synthesized compounds such as nanobodies. In contrast, exposure of the fetal ovine lung in vivo to ethanol, a risk factor for preterm birth, reduces pulmonary alveolar development and surfactant protein A expression. Because the formalin-inactivated RSV vaccination enhances some inflammatory responses to RSV infection in lambs, this model has the potential to assess mechanisms of formalin-inactivated RSV enhanced disease as well as newly developed vaccines.

Mechanical ventilation drives inflammation in severe viral bronchiolitis

Introduction

Respiratory insufficiency due to severe respiratory syncytial virus (RSV) infection is the most frequent cause of paediatric intensive care unit admission in infants during the winter season. Previous studies have shown increased levels of inflammatory mediators in airways of mechanically ventilated children compared to spontaneous breathing children with viral bronchiolitis. In this prospective observational multi-center study we aimed to investigate whether this increase was related to disease severity or caused by mechanical ventilation.

Materials and Methods

Nasopharyngeal aspirates were collected <1 hour before intubation and 24 hours later in RSV bronchiolitis patients with respiratory failure (n = 18) and non-ventilated RSV bronchiolitis controls (n = 18). Concentrations of the following cytokines were measured: interleukin (IL)-1α, IL-1β, IL-6, monocyte chemotactic protein (MCP)-1 and macrophage inflammatory protein (MIP)-1α.

Results

Baseline cytokine levels were comparable between ventilated and non-ventilated infants. After 24 hours of mechanical ventilation mean cytokine levels, except for MIP-1α, were elevated compared to non-ventilated infected controls: IL-1α (159 versus 4 pg/ml, p<0.01), IL-1β (1068 versus 99 pg/ml, p<0.01), IL-6 (2343 versus 958 pg/ml, p<0.05) and MCP-1 (174 versus 26 pg/ml, p<0.05).

Conclusions

Using pre- and post-intubation observations, this study suggests that endotracheal intubation and subsequent mechanical ventilation cause a robust pulmonary inflammation in infants with RSV bronchiolitis.

Hospitalization for respiratory syncytial virus bronchiolitis and disease severity in twins

BACKGROUND

Respiratory syncytial virus (RSV) is a common cause of lower respiratory tract disease and hospitalization in infants and young children. Infants of multiple births, who are often premature, might be more susceptible to developing a more severe RSV infection than singletons.

OBJECTIVE

To assess the impact of multiple births on the severity of RSV infection and define risk factors for acquiring RSV infection in infants of multiple birth.

METHODS

Clinical data on infants hospitalized with RSV infection between 2008 and 2010 were retrospectively collected.

RESULTS

Twins comprised 7.6% (66/875) of hospitalized infants with RSV bronchiolitis during the study period. Infants in the twin group were younger (122.4 +/- 131.7 vs. 204.5 +/- 278.8 days, P = 0.014), had a lower mean gestational age (35.3 +/- 2.6 vs. 38.6 +/- 2.5 weeks, P < 0.001), and were more likely to have been born prematurely compared with singleton infants (65.6% vs. 13%, P < 0.001). On a multivariable logistic regression analysis, young age, early gestational age and male gender were the only variables identified as risk factors for pediatric intensive care unit admission (P < 0.001, P < 0.001 and P = 0.03, respectively). In contrast, the mere fact of a child being a twin was not found to be a significant risk factor for disease severity. In addition, if one twin is hospitalized due to RSV infection, the other has a 34% chance of also being hospitalized with bronchiolitis. Young age was a significant risk factor for hospitalization of the second twin (P < 0.001) CONCLUSIONS: Our findings suggest that twins hospitalized with RSV bronchiolitis do not have an increased risk for severe infection as compared to singletons. However, a twin of an infant hospitalized with RSV infection has a considerable risk of also being hospitalized with bronchiolitis, thus close monitoring is recommended.

Vertical transmission of respiratory syncytial virus modulates pre- and postnatal innervation and reactivity of rat airways

Background

Environmental exposure to respiratory syncytial virus (RSV) is a leading cause of respiratory infections in infants, but it remains unknown whether this infection is transmitted transplacentally from the lungs of infected mothers to the offspring. We sought to test the hypothesis that RSV travels from the respiratory tract during pregnancy, crosses the placenta to the fetus, persists in the lung tissues of the offspring, and modulates pre- and postnatal expression of growth factors, thereby predisposing to airway hyperreactivity.

Methodology

Pregnant rats were inoculated intratracheally at midterm using recombinant RSV expressing red fluorescent protein (RFP). Viral RNA was amplified by RT-PCR and confirmed by sequencing. RFP expression was analyzed by flow cytometry and viral culture. Developmental and pathophysiologic implications of prenatal infection were determined by analyzing the expression of genes encoding critical growth factors, particularly neurotrophic factors and receptors. We also measured the expression of key neurotransmitters and postnatal bronchial reactivity in vertically infected lungs, and assessed their dependence on neurotrophic signaling using selective biological or chemical inhibition.

Principal Findings

RSV genome was found in 30% of fetuses, as well as in the lungs of 40% of newborns and 25% of adults. RFP expression was also shown by flow cytometry and replicating virus was cultured from exposed fetuses. Nerve growth factor and its TrkA receptor were upregulated in RSV- infected fetal lungs and co-localized with increased cholinergic innervation. Acetylcholine expression and smooth muscle response to cholinergic stimulation increased in lungs exposed to RSV in utero and reinfected after birth, and blocking TrkA signaling inhibited both effects.

Conclusions/Significance

Our data show transplacental transmission of RSV from mother to offspring and persistence of vertically transmitted virus in lungs after birth. Exposure to RSV in utero is followed by dysregulation of neurotrophic pathways predisposing to postnatal airway hyperreactivity upon reinfection with the virus.

Clinical and epidemiologic features of respiratory syncytial virus

Since its discovery in 1955, respiratory syncytial virus (RSV) has consistently been noted to be the single most important cause of lower respiratory tract illness in infants <1 year of age. RSV also causes repeat infections and significant disease throughout life. In addition to the young child, persons with compromised immune, pulmonary or cardiac systems, and the elderly have significant risk from infection. Though RSV causes the full spectrum of acute respiratory illnesses, it is most notably associated with signs and symptoms of increased airway resistance manifested as wheezing and, in the young child, diagnosed as bronchiolitis. In temperate climates, RSV occurs as yearly outbreaks usually between late fall and early spring lasting 3-4 months in a community. The timing of outbreaks varies between years and in the same year between regions and even between nearby communities. RSV can be a serious nosocomial pathogen in high risk individuals but nosocomial transmission that can often be prevented with meticulous attention to good infection control practices. High risk groups include the premature infants and persons of any age with compromised cardiac, pulmonary, or immune systems. Risk factors for infection include increased number of children in the household and day care center attendance. There are reasonable estimates of the sizable burden of RSV disease in infants and young children and the elderly but less data on disease in older children, the role of RSV in later reactive airway disease (see chapter by M.T. Lotz et al. , this volume), and RSV-associated mortality in developing countries. The available data on burden of disease suggests there are at least four potential target populations for a vaccine, the young infant, young children >4-6 months of age, pregnant women, and the elderly. A link between infection in the young infant and later reactive airway disease and mortality in developing countries is needed. Each target population has different vaccine safety and efficacy concerns and may warrant a different type of vaccine.

Respiratory syncytial virus reverses airway hyperresponsiveness to methacholine in ovalbumin-sensitized mice

Each year, approximately 20% of asthmatics in the United States experience acute symptom exacerbations, which commonly result from pulmonary viral infections. The majority of asthma exacerbations in very young children follow infection with respiratory syncytial virus (RSV). However, pathogenic mechanisms underlying induction of asthma exacerbations by RSV are not well understood. We therefore investigated the effect of post-sensitization RSV infection on lung function in ovalbumin (OVA)-sensitized BALB/c mice as a model of RSV asthma exacerbations. OVA sensitization of uninfected female BALB/c mice increased bronchoalveolar lavage fluid (BALF) eosinophil levels and induced airway hyperresponsiveness to the muscarinic agonist methacholine, as measured by the forced-oscillation technique. In contrast, intranasal infection with replication-competent RSV strain A2 for 2–8 days reduced BALF eosinophil counts and reversed airway hyperresponsiveness in a pertussis toxin-sensitive manner. BALF levels of the chemokine keratinocyte cytokine (KC; a murine homolog of interleukin-8) were elevated in OVA-sensitized, RSV-infected mice and reversal of methacholine hyperresponsiveness in these animals was rapidly inhibited by KC neutralization. Hyporesponsiveness could be induced in OVA-sensitized, uninfected mice by recombinant KC or the Gαi agonist melittin. These data suggest that respiratory syncytial virus induces KC-mediated activation of Gαi, resulting in cross-inhibition of Gαq-mediated M₃-muscarinic receptor signaling and reversal of airway hyperresponsiveness. As in unsensitized mice, KC therefore appears to play a significant role in induction of airway dysfunction by respiratory syncytial virus. Hence, interleukin-8 may be a promising therapeutic target to normalize lung function in both asthmatics and non-asthmatics with bronchiolitis. However, the OVA-sensitized, RSV-infected mouse may not be an appropriate model for investigating the pathogenesis of viral asthma exacerbations.

Evidence for a causal relationship between respiratory syncytial virus infection and asthma

Respiratory syncytial virus (RSV) infects all children early in life, is the most common cause of infant lower respiratory tract infections, and causes disease exacerbations in children with asthma. Episodes of lower respiratory tract infection in early life are associated with asthma development. Whether RSV infection early in life directly causes asthma or simply identifies infants who are genetically predisposed to develop subsequent wheezing is debatable. Recent studies suggest that these two explanations are not mutually exclusive, and are likely both important in asthma development. An open-label study of RSV immunoprophylaxis administered to preterm infants reduced recurrent wheezing by 50%. Clinical trials of infant RSV prevention, delay or severity reduction on the outcome of childhood asthma would confirm the causal relationship between RSV infection and asthma, and offer a primary prevention strategy.

Effect of glucocorticoid in mice of asthma induced by ovalbumin sensitisation and RSV infection

OBJECTIVE

To investigate the inflammatory changes and the airway hyper-responsiveness in the asthma mouse model infected by respiratory syncytial virus and elucidate the relationship between the infection and the effect of glucocorticoid.

METHODS

60 BALB/c mice were randomly divided into 6 groups. One of these is the control group; the others are the OVA/sham group, the OVA/sham +Dex group, the PBS/RSV group, the OVA/RSV group and the OVA/RSV+Dex group. The airway resistance was measured using a sealed body plethysmograph. Pathological slides were stained with hematoxylin-eosin, and the peribronchial inflammation was observed microscopically. The concentrations of IL-4, IFN-gamma, TGF-beta1 in lung tissues were detected by ELISA.

RESULTS

Compared with the control group, the degree of the airway inflammation and hyperresponsiveness and the concentrations of IL-4/IFN-gamma, TGF-beta1 in all four OVA groups increased significantly. And there was a statistically significant difference between the OVA/sham group and the OVA/sham+Dex group, and between the OVA/RSV group and the OVA/RSV+Dex group respectively. Compared with the OVA/RSV group, there was an obvious aggravation of airway inflammation and hyper-responsiveness in the OVA/RSV+Dex group.

CONCLUSIONS

Glucocorticoid significantly reduces airway inflammation and hyper-responsiveness induced by repetitive OVA challenge in the mouse model of asthma. However, the significant decrease in Th1 and increase in Th2 inflammation and aggravation of airway hyper-responsiveness in the mice in OVA/RSV group show that they are not sensitive to glucocorticoid. The effects of infection with RSV on the mouse model of asthma could be the cause of the glucocorticoid resistance during the therapy.

Prevention of serious respiratory syncytial virus-related illness. I: Disease pathogenesis and early attempts at prevention

Respiratory syncytial virus (RSV) was first described 160 years ago but was not officially recognized as a cause of serious illness in children until the late 1950s. It has been estimated that virtually all children have had at least one RSV infection by their second birthday. RSV is responsible for annual disease outbreaks, usually during a defined winter seasonal period that can vary by community and year. RSV is recognized as the leading cause of hospitalization among young children worldwide. Infants of young chronologic age and children with predisposing factors, such as premature birth, pulmonary disease, or congenital heart disease, are most susceptible to serious illness. Unlike other viruses, immunity to RSV infection is incomplete and short lived, and reinfection is common throughout life. Initial attempts to develop a vaccine in the 1960s met with unexpected and tragic results; many children vaccinated with a formalin-inactivated wild-type virus developed serious pulmonary disease upon subsequent natural infection. Numerous other vaccine technologies have since been studied, including vectored approaches, virus-like particles, DNA vaccines, and live attenuated virus vaccine. As of early 2010, only two companies or institutions had RSV vaccine candidates in early clinical trials, and no vaccine is likely to be licensed for marketing in the immediate future.

Right ventricular function in children with severe respiratory syncytial virus (RSV) bronchiolitis

BACKGROUND

Previous studies have demonstrated the development of myocardial damage and hepatitis in children with severe respiratory syncytial virus (RSV) infection. The aim of this study was to assess right ventricular function in children with severe RSV disease and to investigate an association with disease severity, myocardial damage, and hepatitis.

METHODS

This was a prospective observational study performed at a 20-bed regional multidisciplinary tertiary pediatric intensive care unit (PICU) in a university-affiliated children's hospital. Pulse wave Doppler echocardiographic assessments with a calculation of the right ventricular function (Tei index), left ventricular ejection fraction and diameters, cardiac troponin T levels, transaminase and C-reactive protein levels were performed at admission on consecutive children who were ventilated and diagnosed with a severe RSV infection and without congenital heart disease.

RESULTS

Thirty-four ventilated children with confirmed RSV bronchiolitis were enrolled. The median age was 1.4 months (range 0.4-11.7), and the median length of ventilation was 5 days (range 2-10). Seven (20%) infants had an elevated right ventricular Tei index indicating reduced right ventricular function. Left ventricular function as well as C-reactive protein and transaminase levels were not different between patients with and without an elevated right ventricular Tei index. Cardiac troponin T was elevated in 14 patients (41%): 3/7 with an elevated and 11/27 with a normal Tei index (P=1). Ventilation and oxygenation indices and the duration of mechanical ventilation were not different between the two groups.

CONCLUSION

A raised right ventricular Tei index, consistent with reduced right ventricular function, was observed in severe RSV disease, but the degree of dysfunction was not related to the level of biochemical myocardial or hepatic damage or level of respiratory support.

Creola bodies in infancy with respiratory syncytial virus bronchiolitis predict the development of asthma

BACKGROUND

Creola bodies (CrBs) in the sputum are an indicator of respiratory epithelial damage and appear specifically in bronchial asthma. We studied the presence and clinical significance of CrBs in infants with respiratory syncytial virus (RSV) bronchiolitis contributing to the development of asthma.

METHODS

Aspirated sputum samples were collected from 33 infants admitted with acute RSV bronchiolitis. The samples were then examined for the presence (or absence) of CrBs and classified into the RSV-CrB group and RSV-non-CrB group. Eosinophil cationic protein (ECP) and neutrophil elastase (NE) concentrations in the sputum were compared between the two groups. History of wheeze and asthma was collected at 2 years and 5 years after their discharge from hospital.

RESULTS

CrBs were detected in 23 of the 33 subjects (69.7%). No significant difference in the ECP and the NE concentration were observed between the RSV-CrB group and RSV-non-CrB group. A significant relationship was observed between CrBs detected with RSV bronchiolitis and the development of recurrent wheezing and asthma (after 2 years: relative risk [RR], 3.09; p = 0.002; after 5 years: RR 7.00; p = 0.019).

CONCLUSIONS

These findings suggest that a high rate of CrBs in the sputum is present in infants with RSV bronchiolitis, and notably the CrBs are associated with the progression to recurrent wheezing and asthma.

The role of cytokines and chemokines in severe respiratory syncytial virus infection and subsequent asthma

Respiratory syncytial virus (RSV) is the primary cause of serious lower respiratory tract illness in infants and young children worldwide. The mechanism is largely unknown. RSV stimulates airway epithelial cells and resident leukocytes to release cytokines. Cytokines and chemokines involved in host response to RSV infection are thought to play a central role in the pathogenesis. In addition, RSV infection early in life has been associated with the development of asthma in later childhood. It is likely that the persistence of cytokines and chemokines in fully recovered patients with RSV in the long term can provide a substratum for the development of subsequent asthma. This review describes the genetic factors in cytokines and chemokines associated with severity of RSV disease, cytokines and chemokines synthesis in RSV infection, and the role of these innate immune components in RSV-associated asthma.

Do early-life viral infections cause asthma?

Epidemiologic associations between viral lower respiratory infections (LRIs) and asthma in later childhood are well known. However, the question of whether such infections cause asthma or unmask asthma in a susceptible host has still not been settled. Most early evidence centered on the role of the respiratory syncytial virus; however, recent studies highlight a potential role for human rhinovirus as a risk factor for asthma. The links between early-life viral LRI and subsequent asthma are generally via wheeze; however, the presence of wheeze does not give any information about why the child is wheezing. Wheeze in early life is, at best, a fuzzy phenotype and not specific for subsequent asthma. The risk of asthma after viral LRI is increased in the presence of allergic sensitization in early life and if the infection is more severe. Atopy-associated mechanisms also appear to be involved in viral-induced acute exacerbations of asthma, especially in prolonging symptomatology after the virus has been cleared from the lungs. Breaking the nexus between viral respiratory infections and asthma may be possible with interventions designed to inhibit atopy-related effectors mechanisms from participating in the host response to respiratory viral infections.

Inhibitory effect of melatonin on lung oxidative stress induced by respiratory syncytial virus infection in mice

Previous research has shown that antioxidant (butylated hydroxyanisole) treatment ameliorates respiratory syncytial virus (RSV)-induced disease and lung inflammation. Melatonin has been reported to exhibit a wide varieties of biological effects, including antioxidant and anti-inflammation, and has no evident toxicity and side effect. But it is not known whether melatonin would modify RSV-induced lung disease and oxidative stress. The present study was to establish the involvement of oxidative stress in the pathogenesis of RSV-induced lung inflammation, and to investigate the protective effect of administration of melatonin in mice with RSV-induced oxidative pulmonary injury for 4 days. Malondialdehyde (MDA), an end product of lipid peroxidation, and glutathione (GSH) and superoxide dismutase (SOD) and nitric oxide (NO) levels were evaluated in lung tissue homogenates by spectrophotometry. Hydroxyl radical (.-OH), one of the indicators of free radical formation, was also detected in lung homogenates by Fenton reaction. Tumor necrosis factor-a (TNF-a) concentrations in mouse serum were measured with ELISA assay. The results demonstrated that the mice intranasally inoculated with RSV resulted in oxidative stress changes by increasing NO, MDA and .-OH levels, and decreasing GSH and SOD activities, whereas administration of melatonin significantly reversed all these effects. Furthermore, melatonin inhibited production of proinflammatory cytokines such as TNF-a in serum of RSV-infected mice. These results suggest that melatonin ameliorates RSV-induced lung inflammatory injury in mice via inhibition of oxidative stress and proinflammatory cytokine production and may be as a novel therapeutic agent in virus-induced pulmonary infection.

Low incidence of severe respiratory syncytial virus infections in lung transplant recipients despite the absence of specific therapy

BACKGROUND

Respiratory syncytial virus (RSV) infections in lung transplant recipients (LTRs) have been associated with significant morbidity and mortality. Immunoglobulins, ribavirin, and palivizumab are suggested treatments for both pre-emptive and therapeutic purposes. However, in the absence of randomized, placebo-controlled trials, efficacy is controversial and there is toxicity as well as cost concerns.

METHODS

We retrospectively reviewed cases of lower respiratory tract RSV infections in adult LTRs. Diagnosis was based on clinical history, combined with a positive polymerase chain reaction (PCR) and/or viral cultures of bronchoalveolar lavage (BAL) specimens.

RESULTS

Ten symptomatic patients were identified (7 men and 3 women, age range 28 to 64 years). All were hospitalized for community-acquired respiratory tract infections. Two patients had a concomitant acute Grade A3 graft rejection, and 1 patient had a concomitant bacterial pneumonia. Eight patients did not receive a specific anti-RSV treatment because of clinical stability and/or improvement at the time of RSV diagnosis. Only 2 patients (1 with Grade A3 allograft rejection and 1 requiring mechanical ventilation) received ribavirin and palivizumab. All patients recovered without complications and with no persistent RSV infection. However, bronchiolitis obliterans (BOS) staging worsened in 6 patients during the mean follow-up of 45 months.

CONCLUSIONS

Our data suggest that mild RSV infections in LTRs might evolve favorably in the absence of specific anti-viral therapy. However, this observation needs confirmation in a large clinical trial specifically investigating the development of BOS in untreated vs treated patients.

A systemic neutrophil response precedes robust CD8(+) T-cell activation during natural respiratory syncytial virus infection in infants

Severe primary respiratory syncytial virus (RSV) infections are characterized by bronchiolitis accompanied by wheezing. Controversy exists as to whether infants suffer from virus-induced lung pathology or from excessive immune responses. Furthermore, detailed knowledge about the development of primary T-cell responses to viral infections in infants is lacking. We studied the dynamics of innate neutrophil and adaptive T-cell responses in peripheral blood in relation to the viral load and parameters of disease in infants admitted to the intensive care unit with severe RSV infection. Analysis of primary T-cell responses showed substantial CD8(+) T-cell activation, which peaked during convalescence. A strong neutrophil response, characterized by mobilization of bone marrow-derived neutrophil precursors, preceded the peak in T-cell activation. The kinetics of this neutrophil response followed the peak of clinical symptoms and the viral load with a 2- to 3-day delay. From the sequence of events, we conclude that CD8(+) T-cell responses, initiated during primary RSV infections, are unlikely to contribute to disease when it is most severe. The mobilization of precursor neutrophils might reflect the strong neutrophil influx into the airways, which is a characteristic feature during RSV infections and might be an integral pathogenic process in the disease.

Clinical and epidemiological comparison of human metapneumovirus and respiratory syncytial virus in seoul, Korea, 2003-2008

Human metapneumovirus (HMPV) shares clinical and epidemiological characteristics with well-known respiratory syncytial virus (RSV). The aim of this study was to investigate the clinical and epidemiological differences between HMPV- and RSV-induced wheezing illnesses. A total of 1,008 nasopharyngeal aspirate specimens was collected from 1,008 pediatric patients hospitalized with acute respiratory tract infection at Inje University Sanggye Paik Hospital from December 2003 to April 2008, and tested for seven common respiratory viruses. Conditions classified as wheezing illness were bronchiolitis, reactive airways disease, and bronchial asthma. HMPV caused a significantly lower proportion of wheezing illness when compared to RSV (48.1% vs. 82.2%, P<0.05). HMPV-induced wheezing illness occurred predominantly in older patients when compared to RSV patients (P<0.001). RSV infections peaked in the fall and winter followed by peaks of HMPV infection in winter and spring. Eosinophil counts were significantly higher (P<0.01) in RSV patients when compared to HMPV patients. These results show that human metapneumovirus patients exhibit several different clinical and epidemiological characteristics, such as higher proportion of wheezing illness, age and seasonal incidence, and eosinophil counts, when compared to RSV patients.

The impact of respiratory syncytial virus infection on endothelin receptor function and release in sheep bronchial explants

We investigated the impact of respiratory syncytial virus (RSV) infection, an important asthma precipitant, on endothelin receptor function and release in sheep bronchial explants. RSV infection was confirmed using polymerase chain reaction and immunohistochemistry. Since sheep airway smooth muscle contains only endothelin-A receptors, sarafotoxin (Stx) S6c did not cause airway contraction. In contrast, sarafotoxin S6c (300 nM) caused contraction in RSV-infected bronchial explants (8 +/- 3% carbachol Emax). However, we could not detect airway smooth muscle endothelin-B receptors in explants using autoradiography. RSV infection per se did not alter the release of immunoreactive endothelin from sheep bronchial explants (control = 11.6 +/- 0.9 pg versus RSV = 12.1 +/- 0.9 pg). Interestingly, dexamethasone (1 microM) alone increased endothelin release in both control (17.9 +/- 2.0 pg) and RSV-infected tissue (18.3 +/- 3.1 pg). The combined presence of protease-activated receptor-2 (PAR-2) ligand (100 microM) and dexamethasone (1 microM) also increased endothelin release from control tissue (17.3 +/- 1.4 pg), but endothelin release was suppressed by PAR-2 ligand in RSV-infected tissue (10.3 +/- 0.8 pg), probably because PAR-2 expression was increased by RSV. In summary, the novel expression of endothelin-B receptors triggered by RSV might be relevant to RSV-associated asthma. Furthermore, activation of airway PAR-2 may be protective in asthma where endothelin levels are elevated in part via endothelin release suppression.

[Toll-like receptor 4 expression and function of respiratory syncytial virus-infected airway epithelial cells]

OBJECTIVE

To observe the epithelial Toll like receptor (TLR)4 expression changes and the signaling pathway function after respiratory syncytial virus (RSV) infection and to explore the mechanisms of RSV-induced airway inflammation.

METHODS

9HTEo-human tracheal epithelial cell line was infected by RSV (MOI = 10), and TLR1-10 mRNA were detected by RT-PCR assay at 3 h post RSV infection. TLR4 mRNA was detected by real time Q-PCR assay at 3 h, 6 h and 9 h post RSV infection, and TLR4 protein expression and cell apoptosis were determined by flow cytometry at 24 h post RSV infection. IL-8 in supernatant was detected by ELISA after RSV-infected cells exposed to lipopolysaccharide (LPS). A normal control group and a RSV infection group were set up for the RT-PCR and flow cytometry experiments, and the data were analyzed by paired t test using GraphPad 4.0 software. A normal group, a RSV group and a UV-inactivated RSV group were set up for the real time Q-PCR, experiments, and the data were analyzed by Kruskal-Wallis test. The ELISA experiments were divided into 4 groups including a normal control, a RSV, a LPS stimulation, and a RSV plus LPS co-stimulation groups, and the data were analyzed by One-way ANOVA test.

RESULTS

(1) TLR2-10 mRNA level was significantly up-regulated (t value of TLR2-10: 3.49 -14.47, P < 0.05), especially TLR-2, 6 enhanced expression, compared with the normal epithelial cells. Real time Q-PCR assay showed that TLR4 mRNA started to increase at 3hr (Kruskal-Wallis test value = 8.82, P < 0.05, n = 6) and significantly elevated at 9 hour (Kruskal-Wallis test value = 6.62, P < 0.05, n = 6). UV inactivated-RSV had no effect on the TLR4 mRNA level. (2) Flow cytometry showed that membrane TLR4 mean fluorescence intensity (MFI) increased (RSV: 1.27 +/- 0.48, normal: 0.97 +/- 0.25; t = 2.39, P > 0.05, n = 10) while cytoplasmic TLR4 MFI simultaneously decreased (RSV: 3.08 +/- 1.38, normal: 3.36 +/- 1.31, t = 2.92, P = 0.225, n = 10). Percentage of membrane TLR4-positive cells was higher in RSV infected population [RSV: (11.99 +/- 7.74)%, normal: (1.16 +/- 0.47)%, Mann-Whitney t value = 0.001, P < 0.01, n = 8], most (93.32 +/- 1.7)% of which were Annexin V positive. IL-8 was significantly induced in the RSV plus LPS costimulation group compared with RSV group (F = 59.29, P < 0.01, n = 3).

CONCLUSIONS

RSV induced epithelial TLR4 up-regulation, localization changes from cytoplasm to membrane, IL-8 secretion through TLR4 signaling pathway and epithelial cell apoptosis in membrane TLR4 positive population. These results indicate TLR4 is involved in RSV-induced acute or chronic epithelial-dependent inflammation, which might contribute to acute or chronic airway inflammation.

Viral infection in asthma

In bronchial asthma, respiratory virus infection involves several issues: 1) respiratory virus infection in infancy is a risk factor for, and may predispose to, the development of asthma later in life; 2) respiratory virus infection is associated with the acute exacerbation of bronchial asthma; and, 3) glucocorticosteroids (GC) are not adequate for controlling asthma-related symptoms upon respiratory virus infection. Various cells, inflammatory mediators and cytokines participate in the production of airway inflammation upon respiratory virus infection. Bronchial epithelial cells are a site of infection and replication of respiratory virus. They actively participate in the production of airway inflammation: 1) they produce various proinflammatory cytokines, chemokines and mediators; and, 2) they undergo apoptosis, thereby impairing the repair process. It is therefore important to understand the role of bronchial epithelial cells in the pathophysiology of bronchial asthma. In this review, the interaction between viral infection and asthma is discussed to elucidate the role of bronchial epithelial cells in viral infection.

Influenza and respiratory syncytial virus in infants and children: relationship with attendance at a paediatric emergency unit and characteristics of the circulating strains

A study was carried out on 2,696 Italian children, aged 0-14 years. The goals were: (1) to define the age-related impact of acute respiratory infections (ARI), measured as the risk of attendance at the Paediatric Emergency Room, (2) to better define the importance and proportion of influenza and respiratory syncytial virus (RSV) infections and (3) to acquire deeper knowledge of the influenza strains circulating in infants and children. A standardised emergency unit attendance risk (EUAR) was calculated, by age group for ARI. Specific EUARs were also calculated for the two pathogens. Pharyngeal swabs were tested by polymerase chain reaction (PCR) for influenza and RSVs. Isolation in Madine-Darby canine kidney cells (MDCK) and Hep cells, haemagglutination inhibition (HI) testing and HA1 gene sequence analysis were performed for influenza viruses. Most of the patients enrolled were aged 0-5 years, 1,139 (84.6%) and 1,061 (78.5%) in the two seasons, respectively. The most represented age class was that of 1 year olds (331 cases in 2001-2002 and 301 in 2002-2003). The highest EUAR for ARI was in patients aged 0-3 years (16.8 and 12.9 during the two seasons). The same was observed on calculating this risk by specific pathogens: 17.4 and 5.5 for influenza and 13.0 and 12.7 for RSV. Virological analysis was performed on 2,696 samples, 595 of which proved positive (22%). The highest number of isolates (326) came from patients aged 1-3 years. RSVs were more often identified than influenza viruses in infants aged up to 1 year (32 vs. 20 isolates). Of 265 strains isolated in 2001-2002, 103 were RSVs (87 type A, 16 B) and 162 were influenza (90 type A, 72 B). HI showed that influenza B viruses were related to two lineages, B/Victoria/2/87 (32%) and B/Yamagata/16/88 (68%). Of 330 strains isolated in 2002-2003, 102 were RSVs (91 type A, 11 B) and 228 were influenza viruses (220 type A, 8 B). A/H3N2 strains belonged to two clusters, A/Panama/2007/99-like and A/Fujian/411/02-like, a new variant. This paper discusses the possible role of the identified flu strains in determining EUARs among the population by age class.

[Clinical characteristics of 12 persistently wheezing children with human bocavirus infection]

OBJECTIVE

The impact of human bocavirus (HBoV), a newly identified human parvovirus, on childhood persistent wheezing has not been identified. In this study, the clinical features of infantile persistent wheezing induced by HBoV was analyzed.

METHODS

Tracheal aspirates were collected by bronchofibroscope or nasopharyngeal (NP) aspirates from April, 2006 to January, 2007. HBoV DNA in the tracheal aspirates of 33 children with persistent wheezing and in NP aspirates of 6 children with persistent wheezing, who had at least or more than four weeks wheezing. RSV was identified by virus isolation in Hep-2 cells and antigen detetion by direct immunofluorescence assay (DIFA) which was also used for diagnosis of adenovirus, influenza A and B, parainfluenza 1, 2, 3 infection.

RESULTS

Of the 39 children with persistent wheezing, 12 cases (31%) were positive for HBoV DNA. Age of HBoV-positive patients ranged from 2 month to 1 year. The results of sequencing of PCR products proved that sequences of HBoV DNA from these 12 samples were exactly identical to the those of HBoV stored in GeneBank (accession numbers DQ000495 and DQ000496). Two cases with HBoV infection were found to be co-infected with RSV. Ten of the 12 HBoV-positive samples were collected during the period from winter to spring (1 in November, 4 in December, 2 in January and 3 in April), the other two HBoV-positive samples were collected during the period from summer to autumn (1 in May and the other in July). Seven of the 12 HBoV DNA-positive patients had fever, 5 of them had high fever. Significantly more patients with HBoV infection had fever as compared to patients with RSV infection. All the HBoV positive patients showed abnormal findings on chest X ray such as interstitial infiltrates, lung infiltration and hyperinflation. Abnormal findings on chest X ray were found in higher proportion of HBoV positive patients as compared with RSV positive patients. And other manifestations such as wheezing, cough and respiratory distress had no significant difference between HBoV and RSV infected patients.

CONCLUSIONS

This study further demonstrated that HBoV probably is a common pathogen of lower respiratory infection in children and might particularly be associated with persistent wheezing.