Increased production of IFN-gamma and cysteinyl leukotrienes in virus-induced wheezing

The Role of Interferons in Driving Susceptibility to Asthma Following Bronchiolitis: Controversies and Research Gaps

Bronchiolitis is the most common cause of hospitalization in infancy and is associated with a higher risk for the development of childhood asthma. However, not all children hospitalized with bronchiolitis will develop asthma. The mechanisms underlying asthma development following bronchiolitis hospitalization are complex. Immune responses to respiratory viruses may underlie both bronchiolitis severity and long-term sequela (such as asthma). Interferons (IFNs) are important components of innate immune responses to respiratory viruses and could influence both asthma development and asthma exacerbations. However, the nature of the relationship between interferon production and wheezing illnesses is controversial. For example, low peripheral blood IFN responses at birth have been linked with recurrent wheeze and asthma development. In contrast, there is evidence that severe illnesses (e.g., hospitalization for bronchiolitis) are associated with increased IFN responses during acute infection (bronchiolitis hospitalization) and a higher risk for subsequent asthma diagnosis. Furthermore, mechanistic studies suggest that bronchial epithelial cells from asthmatic children have impaired IFN responses to respiratory viruses, which may enable increased viral replication followed by exaggerated secondary IFN responses. This review aims to discuss controversies around the role of IFNs as drivers of susceptibility to asthma development following bronchiolitis hospitalization. Past evidence from both mechanistic and cohort studies are discussed. We will highlight knowledge gaps that can inform future research study design.

The role of 5-lipoxygenase in the pathophysiology of COVID-19 and its therapeutic implications

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, known as coronavirus disease 2019 (COVID-19) causes cytokine release syndrome (CRS), leading to acute respiratory distress syndrome (ARDS), acute kidney and cardiac injury, liver dysfunction, and multiorgan failure. Although several studies have discussed the role of 5-lipoxygenase (5-LOX) in viral infections, such as influenzae and SARS, it remains unexplored in the pathophysiology of COVID-19. 5-LOX acts on free arachidonic acid (AA) to form proinflammatory leukotrienes (LTs). Of note, numerous cells involved with COVID-19 (e.g., inflammatory and smooth muscle cells, platelets, and vascular endothelium) widely express leukotriene receptors. Moreover, 5-LOX metabolites induce the release of cytokines (e.g., tumour necrosis factor-α [TNF-α], interleukin-1α [IL-1α], and interleukin-1β [IL-1β]) and express tissue factor on cell membranes and activate plasmin. Since macrophages, monocytes, neutrophils, and eosinophils can express lipoxygenases, activation of 5-LOX and the subsequent release of LTs may contribute to the severity of COVID-19. This review sheds light on the potential implications of 5-LOX in SARS-CoV-2-mediated infection and the anticipated therapeutic role of 5-LOX inhibitors.

Airway immune mediator levels during asthma-like symptoms in young children and their possible role in response to azithromycin

BACKGROUND

Asthma-like symptoms in young children are orchestrated by the local airway immune response, but current knowledge largely relies on in vitro airway models. Azithromycin has been shown to reduce the duration of episodes with asthma-like symptoms, but efficacy may depend on the individual child's immune response.

OBJECTIVES

To investigate in vivo upper airway immune mediator levels during episodes with asthma-like symptoms in young children and their ability to predict the clinical response to azithromycin treatment.

METHODS

A total of 535 children aged 0-3 years from the Copenhagen Prospective Studies of Asthma in Childhood-2010 mother-child cohort were examined for immune mediator levels in samples of nasal epithelial lining fluid during episodes with asthma-like symptoms as well as in the asymptomatic state. In a sub-study, children with recurrent asthma-like symptoms were randomized to either a 3-day course of oral azithromycin (10 mg/kg; n = 32) or placebo (n = 38). In the current study, we compared the pretreatment immune mediator levels with the clinical response to treatment with azithromycin in an exploratory post hoc analysis.

RESULTS

The immune mediator concentrations during vs outside episodes were significantly upregulated for IFN-ɣ (ratio 1.73), TNF-α (ratio 2.05), IL-1β (ratio 1.45), IL-10 (ratio 1.97), while CCL22 (ratio 0.65) was downregulated. Low levels of TNF-α and IL-10 and high levels of CCL22 predicted better treatment response to azithromycin (P-values < .05).

CONCLUSION

Upper airway immune mediator levels were altered during episodes of asthma-like symptoms, and levels of TNF-α, CCL22, and IL-10 may predict the response to azithromycin treatment.

Serum metabolomic profiling reveals important difference between infants with and without subsequent recurrent wheezing in later childhood after RSV bronchiolitis

We aimed to use serum metabolomics to discriminate infants with severe respiratory syncytial virus (RSV) bronchiolitis who later developed subsequent recurrent wheezing from those who did not and to investigate the relationship between serum metabolome and host immune responses with regard to the subsequent development of recurrent wheezing. Fifty-one infants who were hospitalized during an initial episode of severe RSV bronchiolitis at 6 months of age or less were included and followed for up to the age of 3 years. Of them, 24 developed subsequent recurrent wheezing and 27 did not. Untargeted serum metabolomics was performed by ultraperformance liquid chromatography coupled with high-resolution mass spectrometry (UPLC-MS/MS). Cytokines were measured by multiplex immunoassay. Difference in serum metabolomic profiles was observed between infants who developed recurrent wheezing and those who did not. L-lactic acid level was significantly higher in infants with recurrent wheezing than those without. Pyrimidine metabolism, glycerophospholipid metabolism, and arginine biosynthesis were identified as the most significant changed pathways between the two groups. Moreover, L-lactic acid level was positively associated with serum CXCL8 level. This exploratory study showed that differential serum metabolic signatures during severe RSV bronchiolitis in early infancy were associated with the development of subsequent recurrent wheezing in later childhood.

Airway brush cells generate cysteinyl leukotrienes through the ATP sensor P2Y2

Chemosensory epithelial cells (EpCs) are specialized cells that promote innate type 2 immunity and protective neurally mediated reflexes in the airway. Their effector programs and modes of activation are not fully understood. Here, we define the transcriptional signature of two choline acetyltransferase-expressing nasal EpC populations. They are found in the respiratory and olfactory mucosa and express key chemosensory cell genes including the transcription factor Pou2f3, the cation channel Trpm5, and the cytokine Il25 Moreover, these cells share a core transcriptional signature with chemosensory cells from intestine, trachea and thymus, and cluster with tracheal brush cells (BrCs) independently from other respiratory EpCs, indicating that they are part of the brush/tuft cell family. Both nasal BrC subsets express high levels of transcripts encoding cysteinyl leukotriene (CysLT) biosynthetic enzymes. In response to ionophore, unfractionated nasal BrCs generate CysLTs at levels exceeding that of the adjacent hematopoietic cells isolated from naïve mucosa. Among activating receptors, BrCs express the purinergic receptor P2Y2. Accordingly, the epithelial stress signal ATP and aeroallergens that elicit ATP release trigger BrC CysLT generation, which is mediated by the P2Y2 receptor. ATP- and aeroallergen-elicited CysLT generation in the nasal lavage is reduced in mice lacking Pou2f3, a requisite transcription factor for BrC development. Last, aeroallergen-induced airway eosinophilia is reduced in BrC-deficient mice. These results identify a previously undescribed BrC sensor and effector pathway leading to generation of lipid mediators in response to luminal signals. Further, they suggest that BrC sensing of local damage may provide an important sentinel immune function.

Immune recovery following bronchiolitis is linked to a drop in cytokine and LTC4 levels

BACKGROUND

Bronchiolitis is the main cause of hospitalization of children younger than 1 year; however, the immune mechanism of bronchiolitis is not completely understood. The aim of this study was to analyze the recovery of immune response after a bronchiolitis episode.

METHODS

Forty-nine infants hospitalized with bronchiolitis diagnosis were enrolled. Nasopharyngeal aspirates (NPAs) were processed. Twenty-seven pro-inflammatory biomarkers linked to innate immunity, inflammation, and epithelial damage, as well as nitrites and lipid mediators, were evaluated in the NPA supernatant by ELISA (enzyme-linked immunosorbent assay) and Luminex. Also, 11 genes were analyzed in NPA cells by quantitative PCR.

RESULTS

A widespread statistically significant decline of multiple pro-inflammatory parameters and cytokines were detected in the recovery period after respiratory infection: interferon-α2 (IFNα2), IFNγ, interleukin-10 (IL-10), IL-1β, IL-8, IFN-γ-inducible protein-10, vascular endothelial growth factor, monocyte chemoattractant protein-1, macrophage inflammatory protein-1α (MIP-1α), and MIP-1β. Supporting these results, a decreased nuclear factor-κB gene expression was observed (P = 0.0116). A significant diminution of cysteinyl leukotriene C4 (LTC4) soluble levels (P = 0.0319) and cyclooxygenase-2 (COX-2) gene expression were observed in the recovery sample. In children classified by post-bronchiolitis wheezing, LTC4 remains elevated in the NPA supernatant.

CONCLUSIONS

After bronchiolitis, cytokines and biomarkers linked to innate immune response in NPA decrease significantly in the recovery period accompanied by a drop in LTC4 levels; however, this reduction was lower in infants with post-bronchiolitis wheezing.

Respiratory Syncytial Virus Infects Primary Neonatal and Adult Natural Killer Cells and Affects Their Antiviral Effector Function

Background

Respiratory syncytial virus (RSV) is a major cause of severe acute lower respiratory tract infections in infants. Natural killer (NK) cells are important antiviral effector cells that likely encounter RSV in the presence of virus-specific (maternal) antibodies. As NK cells potentially contribute to immunopathology, we investigated whether RSV affects their antiviral effector functions.

Methods

We assessed the phenotype and functionality of primary neonatal and adult NK cells by flow cytometry after stimulation with RSV or RSV-antibody complexes.

Results

We demonstrate for the first time that RSV infects neonatal and adult NK cells in vitro. Preincubation of virus with subneutralizing concentrations of RSV-specific antibodies significantly increased the percentage of infected NK cells. Upon infection, NK cells were significantly more prone to produce interferon-γ, while secretion of the cytotoxicity molecule perforin was not enhanced.

Conclusions

Our findings suggest that (antibody-enhanced) RSV infection of NK cells induces a proinflammatory rather than a cytotoxic response, which may contribute to immunopathology. Considering that most RSV vaccines currently being developed aim at inducing (maternal) antibodies, these results highlight the importance of understanding the interactions between innate effector cells and virus-specific antibodies.

The cysteinyl leukotriene 3 receptor regulates expansion of IL-25-producing airway brush cells leading to type 2 inflammation

Respiratory epithelial cells (EpCs) orchestrate airway mucosal inflammation in response to diverse environmental stimuli, but how distinct EpC programs are regulated remains poorly understood. Here, we report that inhalation of aeroallergens leads to expansion of airway brush cells (BrCs), specialized chemosensory EpCs and the dominant epithelial source of interleukin-25 (IL-25). BrC expansion was attenuated in mice lacking either LTC₄ synthase, the biosynthetic enzyme required for cysteinyl leukotriene (CysLT) generation, or the EpC receptor for leukotriene E₄ (LTE₄), CysLT₃R. LTE₄ inhalation was sufficient to elicit CysLT₃R-dependent BrC expansion in the murine airway through an IL-25-dependent but STAT6-independent signaling pathway. Last, blockade of IL-25 attenuated both aeroallergen and LTE₄-elicited CysLT₃R-dependent type 2 lung inflammation. These results demonstrate that CysLT₃R senses the endogenously generated lipid ligand LTE₄ and regulates airway BrC number and function.

Infant Immune Response to Respiratory Viral Infections

Of all respiratory viruses that affect infants, respiratory syncytial virus (RSV) and rhinovirus (RV) represent the leading pathogens causing acute disease (bronchiolitis) and are associated with the development of recurrent wheezing and asthma. The immune system in infants is still developing, and several factors contribute to their increased susceptibility to viral infections. These factors include differences in pathogen detection, weaker interferon responses, lack of immunologic memory toward the invading pathogen, and T-cell responses that are balanced to promote tolerance and restrain inflammation. These aspects are reviewed here with a focus on RSV and RV infections.

Involvement and Possible Role of Eosinophils in Asthma Exacerbation

Eosinophils are involved in the development of asthma exacerbation. Recent studies have suggested that sputum and blood eosinophil counts are important factors for predicting asthma exacerbation. In severe eosinophilic asthma, anti-interleukin (IL)-5 monoclonal antibody decreases blood eosinophil count and asthma exacerbation frequency. However, even in the absence of IL-5, eosinophilic airway inflammation can be sufficiently maintained by the T helper (Th) 2 network, which comprises a cascade of vascular cell adhesion molecule-1/CC chemokines/eosinophil growth factors, including granulocyte-macrophage colony-stimulating factor (GM-CSF). Periostin, an extracellular matrix protein and a biomarker of the Th2 immune response in asthma, directly activates eosinophils in vitro. A major cause of asthma exacerbation is viral infection, especially rhinovirus (RV) infection. The expression of intercellular adhesion molecule (ICAM)-1, a cellular receptor for the majority of RVs, on epithelial cells is increased after RV infection, and adhesion of eosinophils to ICAM-1 can upregulate the functions of eosinophils. The expressions of cysteinyl leukotrienes (cysLTs) and CXCL10 are upregulated in virus-induced asthma. CysLTs can directly provoke eosinophilic infiltration in vivo and activate eosinophils in vitro. Furthermore, eosinophils express the CXC chemokine receptor 3, and CXCL10 activates eosinophils in vitro. Both eosinophils and neutrophils contribute to the development of severe asthma or asthma exacerbation. IL-8, which is an important chemoattractant for neutrophils, is upregulated in some cases of severe asthma. Lipopolysaccharide (LPS), which induces IL-8 from epithelial cells, is also increased in the lower airways of corticosteroid-resistant asthma. IL-8 or LPS-stimulated neutrophils increase the transbasement membrane migration of eosinophils, even in the absence of chemoattractants for eosinophils. Therefore, eosinophils are likely to contribute to the development of asthma exacerbation through several mechanisms, including activation by Th2 cytokines, such as IL-5 or GM-CSF or by virus infection-related proteins, such as CXCL10, and interaction with other cells, such as neutrophils.

Activation of mast cells in skin abscess induced by Staphylococcus aureus (S. aureus) infection in mice

The skin abscess is a common inflammatory disease that occurs following the ubiquitous S. aureus infection. In our study, a skin abscess murine model was established and the dynamics of mast cells chemotaxing was evaluated. In the S. aureus-infected mice, severe infiltration of inflammatory cells in the dermis were observed, and mast cells were markedly accumulated in the skins. Besides, tryptase, the marker for mast cells activation, has a positive correlation with mast cell activity. The mast cells identified in the tissues were likely to be activated since they were associated with cell degranulation and the presence of tryptase. Our results suggested that mast cells and its mediator tryptase contribute to the inflammation of skin abscess induced by S. aureus infection.

Leukotriene receptor antagonist attenuated airway inflammation and hyperresponsiveness in a double-stranded RNA-induced asthma exacerbation model

BACKGROUND

Viral infections are the most common triggers of asthma exacerbation, but the key molecules involved in this process have not been fully identified. Although cysteinyl leukotrienes (cysLTs) have been postulated as the key mediators, their precise roles remain largely unclear. To investigate the roles of cysLTs in virus-induced asthma exacerbation, we developed a murine model using a viral double-stranded RNA analog, polyinosinic-polycytidylic acid (poly I:C), and analyzed the effect of leukotriene receptor antagonist (LTRA) administration.

METHODS

A/J mice were immunized with ovalbumin (OVA) + alum (days 0, 28, 42, and 49), followed by intranasal challenge with OVA (phase 1: days 50-52) and poly I:C (phase 2: days 53-55). Montelukast was administered during poly I:C challenge (phase 2) in the reliever model or throughout the OVA and poly I:C challenges (phases 1 and 2) in the controller model. Airway responsiveness to acetylcholine chloride was assessed, and bronchoalveolar lavage (BAL) was performed on day 56.

RESULTS

Administration of poly I:C to OVA-sensitized and -challenged mice increased the number of eosinophils and levels of IL-13, IL-9, CCL3, and CXCL1 in BAL fluid (BALF) and tended to increase airway responsiveness. Montelukast significantly attenuated the poly I:C-induced increase in the number of eosinophils and levels of IL-13, IL-9, and CCL3 in BALF and airway hyperresponsiveness in both the reliever and controller models.

CONCLUSIONS

This is the first report showing that LTRA functionally suppressed the pathophysiology of a virus-induced asthma exacerbation model, suggesting the importance of cysLTs as a potential treatment target.

Nasopharyngeal aspirate & blood cytokine profile in infants hospitalized for respiratory syncytial virus bronchiolitis: A pilot study from south India

Background & objectives:

Following a respiratory syncytial virus (RSV) bronchiolitis, only some infants develop serious illness, and a proportion of them develop recurrent wheeze subsequently. Studies have revealed that cytokine expression following RSV infection may influence the severity and also the risk for subsequent reactive airway disease. This present study was conducted to determine the blood, and nasopharyngeal aspirate (NPA) cytokine profile among infants admitted for RSV bronchiolitis.

Methods:

In this prospective pilot study, a sample size of 15 cases and 15 controls was included. Detailed history, physical examination, blood sample and NPA collection were done. Cytokines (IFNγ and IL-4) estimation was done in the blood and NPA samples of cases and blood samples of controls.

Results:

The mean levels of interferon gamma in controls (blood) and cases (NPA and blood) were 5.95, 9.54 and 32.02 pg/ml, respectively. The mean levels of interleukin-4 in controls (blood), and cases (NPA and blood) were 1280.77, 956.08 and 692.37 pg/ml, respectively (P<0.05).

Interpretation & conclusions:

Our study showed that infants with RSV bronchiolitis evoked a Th1 response in both blood and NPA. Large multicentre studies are needed to validate our findings.

Respiratory syncytial virus: an overview of infection biology and vaccination strategies

Respiratory syncytial virus (RSV) is the foremost cause of lower respiratory tract infections, especially in infants and young children. To date, there is no licensed vaccine available for RSV. Only option to restrain RSV is a prophylactic treatment in the form of monoclonal antibody (palivizumab). However, it is quite expensive and used in few patients with co-morbidities. In ongoing research, virologists contemplate about various vaccine candidates to control RSV infection. This review will help in understating the RSV pathobiology and encompass the advancement on various vaccine candidates that would lead to reduce the incidence, mortality and morbidity. Furthermore, it will lighten up the different avenues which might be useful for the development of novel vaccination approaches.

[Seasonality in asthma: Impact and treatments]

The role of seasons should be taken into account in the management of asthma. The environment varies between seasons and it is well documented that asthma is modulated by environment. Viruses cause asthma exacerbations peak, in winter, in adults while the peak is present in September in children. Allergens are probably a less powerful source of asthma exacerbation than viruses but pollen involvement in spring and summer and dust mites in autumn are indisputable. Air pollutants, present in summer during the hottest periods, are also highly involved in asthma exacerbations. Indoor air pollution, in winter, is also implicated in asthma disease. All these environmental factors are synergistic and increase the risk of asthma exacerbation. Therapies should be adapted to each season depending on environmental factors potentially involved in the asthma disease.

Biomarkers of respiratory syncytial virus (RSV) infection: specific neutrophil and cytokine levels provide increased accuracy in predicting disease severity

Despite fundamental advances in the research on respiratory syncytial virus (RSV) since its initial identification almost 60 years ago, recurring failures in developing vaccines and pharmacologic strategies effective in controlling the infection have allowed RSV to become a leading cause of global infant morbidity and mortality. Indeed, the burden of this infection on families and health care organizations worldwide continues to escalate and its financial costs are growing. Furthermore, strong epidemiologic evidence indicates that early-life lower respiratory tract infections caused by RSV lead to the development of recurrent wheezing and childhood asthma. While some progress has been made in the identification of reliable biomarkers for RSV bronchiolitis, a "one size fits all" biomarker capable of accurately and consistently predicting disease severity and post-acute outcomes has yet to be discovered. Therefore, it is of great importance on a global scale to identify useful biomarkers for this infection that will allow pediatricians to cost-effectively predict the clinical course of the disease, as well as monitor the efficacy of new therapeutic strategies.

Effect of beta2-adrenergic agonists on eosinophil adhesion, superoxide anion generation, and degranulation

BACKGROUND

Eosinophils play important roles in the development of asthma exacerbation. Viral infection is a major cause of asthma exacerbation, and the expression of IFN-γ-inducible protein of 10 kDa (IP-10) and cysteinyl leukotrienes (cysLTs) is up-regulated in virus-induced asthma. As β2-adrenergic agonists, such as formoterol or salbutamol, are used to treat asthma exacerbation, we examined whether formoterol or salbutamol could modify eosinophil functions such as adhesiveness, particularly those activated by cysLTs or IP-10.

METHODS

Eosinophils were isolated from the blood of healthy subjects and were pre-incubated with either formoterol or salbutamol, and subsequently stimulated with IL-5, LTD4, or IP-10. Adhesion of eosinophils to intercellular cell adhesion molecule (ICAM)-1 was measured using eosinophil peroxidase assays. The generation of eosinophil superoxide anion (O2(-)) was examined based on the superoxide dismutase-inhibitable reduction of cytochrome C. Eosinophil-derived neurotoxin (EDN) release was evaluated by ELISA as a marker of degranulation.

RESULTS

Neither formoterol nor salbutamol suppressed the spontaneous adhesion of eosinophils to ICAM-1. However, when eosinophils were activated by IL-5, LTD4, or IP-10, formoterol, but not salbutamol, suppressed the adhesion to ICAM-1. Formoterol also suppressed IL-5, LTD4, or IP-10 induced eosinophil O2(-) generation or EDN release.

CONCLUSIONS

These findings suggest that formoterol, but not salbutamol, suppresses eosinophil functions enhanced by IL-5, LTD4, or IP-10. As these factors are involved in the development of asthma exacerbation, our results strongly support the hypothesis that administration of formoterol is a novel strategy for treating asthma exacerbation.

Analysis of the local and systemic inflammatory response in hospitalized infants with respiratory syncitial virus bronchiolitis

BACKGROUND

Respiratory syncytial virus acute bronchiolitis (RSV-AB) is a major cause of hospital admission among our infants. The immune and inflammatory mechanisms involved in the RSV-AB and factors influencing severity have not been clearly established, although an imbalanced Th1 and Th2 response seems to be crucial.

OBJECTIVES

To assess the local and systemic inflammatory response in RSV-AB. To find a possible marker of clinical severity and/or oxygen requirements.

PATIENTS AND METHODS

Levels of nine cytokines were measured in nasopharyngeal aspirate (NPA) and peripheral blood (PB) of 45 infants with RSV-AB and 27 peer controls, including IFNγ, TNFα, VEGF, interleukins 4, 6 and 10, and chemokines (IL-8 and macrophage inflammatory proteins 1-α and 1-β).

RESULTS

The levels of the analyzed cytokines and chemokines were significantly higher in the NPA of RSV-AB group, with a decrease in IL-4/IFNγ ratio. IL-6 and MIP-1β levels in NPA were directly correlated to oxygen therapy. PB showed an increase in IL-8 and a decrease in MIP-1α and MIP-1β in the RSV-AB group (only MIP-1β associated to the need for oxygen therapy). No correlation was found between cytokines and chemokines levels in NPA and PB.

CONCLUSIONS

This study shows that RSV triggers an inflammatory response fundamentally at the respiratory level, with scant systemic repercussion. This local response is characterized by an increase in Th1 and Th2 cytokines, although with a relative predominance of Th1. The determination upon patient admission of IL-6 and MIP-1β levels in NPA, and of MIP-1β in PB could help predict severe forms and the need for oxygenotherapy.

Respiratory syncytial virus--a comprehensive review

Respiratory syncytial virus (RSV) is amongst the most important pathogenic infections of childhood and is associated with significant morbidity and mortality. Although there have been extensive studies of epidemiology, clinical manifestations, diagnostic techniques, animal models and the immunobiology of infection, there is not yet a convincing and safe vaccine available. The major histopathologic characteristics of RSV infection are acute bronchiolitis, mucosal and submucosal edema, and luminal occlusion by cellular debris of sloughed epithelial cells mixed with macrophages, strands of fibrin, and some mucin. There is a single RSV serotype with two major antigenic subgroups, A and B. Strains of both subtypes often co-circulate, but usually one subtype predominates. In temperate climates, RSV infections reflect a distinct seasonality with onset in late fall or early winter. It is believed that most children will experience at least one RSV infection by the age of 2 years. There are several key animal models of RSV. These include a model in mice and, more importantly, a bovine model; the latter reflects distinct similarity to the human disease. Importantly, the prevalence of asthma is significantly higher amongst children who are hospitalized with RSV in infancy or early childhood. However, there have been only limited investigations of candidate genes that have the potential to explain this increase in susceptibility. An atopic predisposition appears to predispose to subsequent development of asthma and it is likely that subsequent development of asthma is secondary to the pathogenic inflammatory response involving cytokines, chemokines and their cognate receptors. Numerous approaches to the development of RSV vaccines are being evaluated, as are the use of newer antiviral agents to mitigate disease. There is also significant attention being placed on the potential impact of co-infection and defining the natural history of RSV. Clearly, more research is required to define the relationships between RSV bronchiolitis, other viral induced inflammatory responses, and asthma.

Montelukast suppresses epithelial to mesenchymal transition of bronchial epithelial cells induced by eosinophils

Epithelial to mesenchymal transition (EMT) is a mechanism by which eosinophils can induce airway remodeling. Montelukast, an antagonist of the cysteinyl leukotriene receptor, can suppress airway remodeling in asthma. The purpose of this study was to evaluate whether montelukast can ameliorate airway remodeling by blocking EMT induced by eosinophils. EMT induced was assessed using a co-culture system of human bronchial epithelial cells and human eosinophils or the eosinophilic leukemia cell lines, Eol-1. Montelukast inhibited co-culture associated morphological changes of BEAS-2b cells, decreased the expression of vimentin and collagen I, and increased the expression of E-cadherin. Montelukast mitigated the rise of TGF-β1 production and Smad3 phosphorylation. Co-culture of human eosinophils with BEAS-2B cells significantly enhanced the production of CysLTs compared with BEAS-2B cells or eosinophils alone. The increase of CysLTs was abolished by montelukast pre-treatment. Montelukast had similar effects when co-culture system of Eol-1 and BEAS-2B was used. This study showed that montelukast suppresses eosinophils-induced EMT of airway epithelial cells. This finding may explain the mechanism of montelukast-mediated amelioration of airway remodeling in bronchial asthma.

Systematic review of montelukast's efficacy for preventing post-bronchiolitis wheezing

Infants often develop reactive airway diseases subsequent to respiratory syncytial virus (RSV) bronchiolitis. Cysteinyl leukotrienes (cysLTs), a class of lipid mediators that have been implicated in the pathogenesis of allergic rhinitis and asthma, are released during RSV infection, thereby contributing to the pathogenic changes in airway inflammation. Many pediatric patients, especially those of very young age, continue to have recurrent episodes of lower airway obstruction after bronchiolitis treatment. This study was to systematically review and assessed the efficacy of montelukast for preventing wheezing in patients with post-bronchiolitis. The Cochrane library, PubMed, China National Knowledge Infrastructure (CNKI) periodical databases were screened for studies related to use of montelukast for preventing post-bronchiolitis wheezing published up to 31 December 2012. Randomized controlled trials (RCTs) and quasi-RCTs using montelukast alone as an active intervention in infants up to 24 months of age with post-bronchiolitis were selected. Two authors independently extracted data and assessed trial quality using the recommendations published by the Cochrane Collaboration. The meta-analyses were performed using the Cochrane statistical package RevMan5.0.0. Four trials, containing 1430 infants with confirmed diagnosis of acute bronchiolitis, were analyzed. Patients were administered montelukast at post-bronchiolitis. Three trials showed no effects of montelukast on reducing the incidence of recurrent wheezing risk ratios (RR = 0.78, 95% CI: 0.55-1.12, p = 0.17), while two trials found that montelukast did reduce the frequency of recurrent wheezing and another two trials demonstrated no effects of montelukast on symptom-free days. The pooled montelukast treatment group showed no significant effect on reducing the usage of corticosteroids, as compared to the placebo group (RR = 1.11, 95% CI: 0.85-1.44, p = 0.45). Two trials showed that montelukast significantly decreased serum eosinophil-derived neurotoxin levels, as compared to the control group. In general, the side effects of rash, vomiting, and insomnia caused by montelukast occurred in 1.5% of patients analyzed. The recent evidences indicate that montelukast may reduce the frequency of post-bronchiolitic wheezing without causing significant side effects but that it has no effects on decreasing incidences of recurrent wheezing, symptom-free days, or the associated usage of corticosteroid in post-bronchiolitis patients. The small number of enrolled participants and the inability to pool all clinical outcomes precludes us from making solid recommendations.

Lower number of plasmacytoid dendritic cells in peripheral blood of children with bronchiolitis following respiratory syncytial virus infection

OBJECTIVES

Dendritic cells (DCs) are key mediators of allergic airway inflammation. Thus, it is important to understand the relationship between respiratory syncytial virus (RSV) infection and DCs, especially in children with RSV bronchiolitis.

METHODS

We collected peripheral blood from 71 children with RSV bronchiolitis at the time of admission and 28 children who were followed up 3 months following admission. Flow cytometry was performed to detect dendritic cell immunophenotypes.

RESULTS

Patients with RSV bronchiolitis exhibited significantly higher number of myeloid DCs and lower number of plasmacytoid DCs at the time of admission and 3 months following discharge, compared with healthy controls. These children had a significantly higher myeloid/plasmacytoid ratio 3 months after discharge compared with healthy controls.

CONCLUSIONS

Among children with RSV bronchiolitis, there is an imbalance in peripheral blood myeloid/plasmacytoid ratio. The low number of plasmacytoid DCs in peripheral blood indicates the development of bronchiolitis due to RSV infection.

Montelukast for postinfectious cough in adults: a double-blind randomised placebo-controlled trial

BACKGROUND

Postinfectious cough is common in primary care, but has no proven effective treatments. Cysteinyl leukotrienes are involved in the pathogenesis of postinfectious cough and whooping cough (pertussis). We investigated the effectiveness of montelukast, a cysteinyl leukotriene receptor antagonist, in the treatment of postinfectious cough.

METHODS

In this randomised, placebo-controlled trial, non-smoking adults aged 16-49 years with postinfectious cough of 2-8 weeks' duration were recruited from 25 general practices in England. Patients were tested for pertussis (oral fluid anti-pertussis toxin IgG) and randomly assigned (1:1) to montelukast 10 mg daily or image-matched placebo for 2 weeks. Patients chose whether to continue study drug for another 2 weeks. The randomisation sequence was computer-generated and stratified by general practice. Patients, health-care professionals, and researchers were masked to treatment allocation. Effectiveness was assessed with the Leicester Cough Questionnaire to measure changes in cough-specific quality of life; the primary outcomes were changes in total score between baseline and two follow-up stages (2 weeks and 4 weeks). The primary analysis was by intention to treat with imputation by last observation carried forward. Recruitment closed on Sept 21, 2012, and follow-up has been completed. This trial is registered with EudraCT (2010-019647-19), UKCRN Portfolio (ID 8360), and ClinicalTrials.gov (NCT01279668).

FINDINGS

From April 13, 2011, to Sept 21, 2012, we randomly assigned 276 patients to montelukast (n=137) or placebo (n=139). 70 (25%) patients had laboratory-confirmed pertussis. Improvements in cough-specific quality of life occurred in both groups after 2 weeks (montelukast: mean 2·7, 95% CI 2·2-3·3; placebo: 3·6, 2·9-4·3), but the difference between groups did not meet the minimum clinically important difference of 1·3 (mean difference -0·9, -1·7 to -0·04, p=0·04). This difference was not statistically significant in any sensitivity analyses. After 2 weeks, 192 of 259 participants from whom data were available elected to continue study drug (99 [77%] of 129 participants on montelukast; 93 [72%] of 130 on placebo). After 4 weeks, there were no significant between-group differences in cough-specific quality of life improvement (montelukast: 5·2, 4·5-5·9; placebo: 5·9, 5·1-6·7; mean difference -0·5, -1·5 to 0·6, p=0·38) or adverse event rates (21 (15%) of 137 patients on montelukast reported one or more adverse events; 31 (22%) of 139 on placebo; p=0·14). The most common adverse events reported were increased mucus production (montelukast, n=6; placebo, n=2), gastrointestinal disturbance (montelukast, n=3; placebo, n=5), and headache (montelukast, n=2; placebo, n=6). One serious adverse event was reported (placebo, n=1), which was unrelated to study drug (shortness of breath and throat tightness after severe coughing bouts).

INTERPRETATION

Montelukast is not an effective treatment for postinfectious cough. However, the burden of postinfectious cough in primary care is high, making it an ideal setting for future antitussive treatment trials.

FUNDING

National Institute for Health Research School for Primary Care Research, UK.

Respiratory syncytial virus infection: mechanisms of redox control and novel therapeutic opportunities

Respiratory syncytial virus (RSV) is one of the most important causes of upper and lower respiratory tract infections in infants and young children, for which no effective treatment is currently available. Although the mechanisms of RSV-induced airway disease remain incompletely defined, the lung inflammatory response is thought to play a central pathogenetic role. In the past few years, we and others have provided increasing evidence of a role of reactive oxygen species (ROS) as important regulators of RSV-induced cellular signaling leading to the expression of key proinflammatory mediators, such as cytokines and chemokines. In addition, RSV-induced oxidative stress, which results from an imbalance between ROS production and airway antioxidant defenses, due to a widespread inhibition of antioxidant enzyme expression, is likely to play a fundamental role in the pathogenesis of RSV-associated lung inflammatory disease, as demonstrated by a significant increase in markers of oxidative injury, which correlate with the severity of clinical illness, in children with RSV infection. Modulation of ROS production and oxidative stress therefore represents a potential novel pharmacological approach to ameliorate RSV-induced lung inflammation and its long-term consequences.

Lung dendritic cell developmental programming, environmental stimuli, and asthma in early periods of life

Dendritic cells (DCs) are important cells of our innate immune system. Their role is critical in inducing adaptive immunity, tolerance, or allergic response in peripheral organs—lung and skin. The lung DCs are not developed prenatally before birth. The DCs develop after birth presumably during the first year of life; exposures to any foreign antigen or infectious organisms during this period can significantly affect DC developmental programming and generation of distinct DC phenotypes and functions. These changes can have both short-term and long-term health effects which may be very relevant in childhood asthma and predisposition for a persistent response in adulthood. An understanding of DC development at molecular and cellular levels can help in protecting neonates and infants against problematic environmental exposures and developmental immunotoxicity. This knowledge can eventually help in designing novel pharmacological modulators to skew the DC characteristics and immune responses to benefit the host across a lifetime.

Rhinovirus load and disease severity in children with lower respiratory tract infections

It has not been clarified if there is a correlation between rhinovirus (RV) load and disease severity in the lower respiratory tract infections of hospitalized children. This study was undertaken to elucidate the contribution of the viral load to the development of disease severity in 412 children ≤3 years of age who were hospitalized with lower respiratory tract infections. The RV load in nasopharyngeal aspirates obtained from the patients at the time of admission was measured by real-time quantitative reverse-transcription polymerase chain reaction (PCR), and the clinical symptoms of the patients were assessed using a severity scoring system. Of the 412 patients, 43 (10.4%) were diagnosed with RV infections only, and 15 were determined to have high severity scores. When all patients infected with RV were assessed, there was no correlation between the viral load and the disease severity. However, there was a significant negative correlation between the disease severity and age among children <11 months of age (n = 15, ρ = -0.677, P = 0.006) and a significant positive correlation between the viral load and the disease severity among children ≥11 months of age (n = 28, ρ = 0.407, P = 0.032). Among the patients infected with RV <11 months of age, the disease severity may be associated with an immature immune response and the small diameter of their airways rather than viral load. By contrast, in the patients ≥11 months of age, viral load may contribute to the development of disease severity.

Eicosanoids and respiratory viral infection: coordinators of inflammation and potential therapeutic targets

Viruses are frequent causes of respiratory infection, and viral respiratory infections are significant causes of hospitalization, morbidity, and sometimes mortality in a variety of patient populations. Lung inflammation induced by infection with common respiratory pathogens such as influenza and respiratory syncytial virus is accompanied by increased lung production of prostaglandins and leukotrienes, lipid mediators with a wide range of effects on host immune function. Deficiency or pharmacologic inhibition of prostaglandin and leukotriene production often results in a dampened inflammatory response to acute infection with a respiratory virus. These mediators may, therefore, serve as appealing therapeutic targets for disease caused by respiratory viral infection.

Airway IFN-γ production during RSV bronchiolitis is associated with eosinophilic inflammation

STUDY OBJECTIVE

This study was designed to investigate the possible role of IFN-γ in eosinophil degranulation that occurs during respiratory syncytial virus (RSV) bronchiolitis.

METHODS

Sixty-seven infants, 2-24 months old and hospitalized with their first episode of acute RSV bronchiolitis, were selected for this study. Eosinophil-active cytokine and chemokine profiles in nasal lavage supernatants taken within the first 48 h of admission were determined by a multiplex bead array system (Luminex). Comparisons were made with control (Control group) subjects (n = 20).

RESULTS

Nasal IFN-γ levels were significantly higher (P < 0.0001) in RSV bronchiolitis (median = 4.4 pg/ml) infants compared to controls (0.0 pg/ml). IFN-γ levels correlated significantly with the levels of nasal eotaxin (r = 0.566, P < 0.0001), RANTES (r = 0.627, P < 0.0001), GM-CSF (r = 0.849, P < 0.0001), and EDN (r = 0.693, P < 0.001). Nasal interleukin (IL)-4, IL-5, and IL-13 were below sensitivity levels in most RSV bronchiolitis and control subjects.

CONCLUSION

These results suggest that IFN-γ may play an important role in eosinophilic inflammation in RSV bronchiolitis.

Respiratory syncytial virus prevention and therapy: past, present, and future

Respiratory syncytial virus (RSV) is the most common respiratory pathogen in infants and young children worldwide. More than 50 years after its discovery, and despite relentless attempts to identify pharmacological therapies to improve the clinical course and outcomes of this disease, the most effective therapy remains supportive care. Although the quest for a safe and effective vaccine remains unsuccessful, pediatricians practicing during the past decade have been able to protect at least the more vulnerable patients with safe and effective passive prophylaxis. This review summarizes the history, microbiology, epidemiology, pathophysiology, and clinical manifestations of this infection in order to provide the reader with the background information necessary to fully appreciate the many challenges presented by the clinical management of young children with bronchiolitis. The last part of this article attempts an evidence-based review of the pharmacologic strategies currently available and those being evaluated, intentionally omitting highly experimental approaches not yet tested in clinical trials and, therefore, not likely to become available in the foreseeable future.

Efficient lung recruitment of respiratory syncytial virus-specific Th1 cells induced by recombinant bacillus Calmette-Guérin promotes virus clearance and protects from infection

Infection by the respiratory syncytial virus (RSV) can cause extensive inflammation and lung damage in susceptible hosts due to a Th2-biased immune response. Such a deleterious inflammatory response can be enhanced by immunization with formalin- or UV-inactivated RSV, as well as with vaccinia virus expressing the RSV-G protein. Recently, we have shown that vaccination with rBCG-expressing RSV Ags can prevent the disease in the mouse. To further understand the immunological mechanisms responsible for protection against RSV, we have characterized the T cell populations contributing to virus clearance in mice immunized with this BCG-based vaccine. We found that both CD4(+) and CD8(+) T cells were recruited significantly earlier to the lungs of infected mice that were previously vaccinated. Furthermore, we observed that simultaneous adoptive transfer of CD8(+) and CD4(+) RSV-specific T cells from vaccinated mice was required to confer protection against virus infection in naive recipients. In addition, CD4(+) T cells induced by vaccination released IFN-γ after RSV challenge, indicating that protection is mediated by a Th1 immune response. These data suggest that vaccination with rBCG-expressing RSV Ags can induce a specific effector/memory Th1 immune response consisting on CD4(+) and CD8(+) T cells, both necessary for a fully protective response against RSV. These results support the notion that an effective induction of Th1 T cell immunity against RSV during childhood could counteract the unbalanced Th2-like immune response triggered by the natural RSV infection.

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.

Breastfeeding is associated with the production of type I interferon in infants infected with influenza virus

BACKGROUND

Breast milk-mediated protection against respiratory viruses is well established. However, protective mechanisms are unclear. Type I interferons (IFN) mediate host defence against respiratory viruses, particularly influenza virus. The relationship among type I IFN, respiratory viral infections and breastfeeding has not been explored.

METHODS

Type I IFN responses were studied by ELISA and real time PCR in nasal secretions of infants experiencing their first respiratory infection. Modulation of IFN by breastfeeding and other variables affecting severity during viral infection was explored.

RESULTS

One hundred and twenty infants were positive by RT-PCR for influenza virus (n = 24), human metapneumovirus (hMPV) (n = 30) or respiratory syncytial virus (RSV) (n = 66). Type I IFNs were detected more frequently in infants infected with influenza virus than in those infected with RSV or hMPV. Breastfeeding promoted higher rates and levels of type I IFN only in infants infected with influenza virus. No effect on IFN production was observed for age, gender or smoking.

CONCLUSION

Our study confirms that type I IFN production is detected more frequently in infants infected with influenza virus. Importantly, higher rates and levels of type I IFN in these infants are associated with breastfeeding. These observations suggest that breast milk can protect against respiratory viruses by activating innate antiviral mechanisms in the host.

Montelukast during primary infection prevents airway hyperresponsiveness and inflammation after reinfection with respiratory syncytial virus

RATIONALE

Respiratory syncytial virus (RSV) bronchiolitis in infants may be followed by the development of asthma-like symptoms. Age at first infection dictates consequences upon reinfection. Reinfection of mice initially exposed as neonates to RSV enhanced development of airway hyperresponsiveness (AHR), eosinophilic inflammation, and mucus hyperproduction. RSV lower respiratory tract disease is associated with activation of the leukotriene pathway.

OBJECTIVES

To determine the effects of montelukast (MK), a cysteinyl leukotriene (cysLT) receptor antagonist, in primary and secondary RSV-infected newborn and adult mice.

METHODS

BALB/c mice were infected with RSV at 1 week (neonate) or 6 to 8 weeks (adult) of age and reinfected 5 weeks later. MK was administered 1 day before the initial infection and through Day 6 after infection. Seven days after primary or secondary infection, airway function was assessed by lung resistance to increasing doses of inhaled methacholine; lung inflammation, goblet cell metaplasia, and cytokine levels in bronchoalveolar lavage fluid were monitored.

MEASUREMENTS AND MAIN RESULTS

RSV infection induced cysLT release in bronchoalveolar lavage fluid. MK decreased RSV-induced AHR, airway inflammation, and increased IFN-gamma production in primary infected adult and neonatal mice. MK, administered during initial infection of neonates but not during secondary infection, prevented subsequent enhancement of AHR, airway eosinophilia, and mucus hyperproduction upon reinfection.

CONCLUSIONS

MK attenuated the initial responses to primary RSV infection in both age groups and altered the consequences of RSV reinfection in mice initially infected as neonates. These data support an important role for cysLT in RSV-induced AHR and inflammation.

Concentrations of IL-15, IL-18, IFN-γ and activity of CD4+, CD8+ and NK cells at admission in children with viral bronchiolitis

The pathogenesis of viral bronchiolitis is poorly understood. The aim of this study was to analyze interleukin (IL)-15, IL-18 and interferon (IFN)-γ concentrations and the activity of NK cells and CD4⁺ and CD8⁺ lymphocytes in 23 children not older than 30 months of age with acute viral bronchiolitis using blood samples drawn within the first 24 h of their hospital admission, in comparison to a healthy group. In children with bronchiolitis, the mean concentrations of IL-15, IL-18 and IFN-γ were 9.39±11.55, 884.03±645.44 and 17.92±27.14 pg/ml, respectively, and were significantly higher than those in the control group [2.34±0.61 pg/ml (p<0.05), 248.69±98.73 pg/ml (p<0.001) and 2.75±1.72 pg/ml (p<0.005), respectively]. In the bronchiolitis group, mean z-scores were -1.15±1.9 for CD4⁺ cells and -0.9±1.23 for CD8⁺ cells; these scores were significantly lower than those of the general Polish population (p<0.001 and <0.01, respectively). However, the mean z-score of the ratio of CD4⁺/CD8⁺ and the NK cell count in children with bronchiolitis did not differ significantly from those of the controls. In conclusion, cytokines such as IL-15, IL-18 and IFN-γ play a role in the pathogenesis of bronchiolitis in children.

Dendritic cells in viral bronchiolitis

Dendritic cells (DCs) are major antigen-presenting cells that constitute a link between innate and adaptive immune responses, and are critical in the processes of control and elimination of viral infections. On the other hand, there is a large body of data strongly implicating respiratory viruses in morbidity during infancy through the induction of lower respiratory tract infections, such as bronchiolitis, and later on in childhood and adult life, mainly due to their association with asthma exacerbations. Little is known, however, about the precise role of DCs in human respiratory tract infections. This review focuses on current data, both from in vivo and in vitro studies, that highlight the interplay between DCs and the viral causes of bronchiolitis.

Cooperative activation of CCL5 expression by TLR3 and tumor necrosis factor-alpha or interferon-gamma through nuclear factor-kappaB or STAT-1 in airway epithelial cells

BACKGROUND

CCL5/RANTES contributes to prolonged eosinophilic inflammation and asthma exacerbation after a viral infection. We studied the mechanism of CCL5 expression using viral product double-stranded RNA (dsRNA), a ligand of Toll-like receptor 3 (TLR3), and inflammatory cytokines in airway epithelial cells.

METHODS

The airway epithelial cell line BEAS-2B was used in our in vitro study, and the levels of CCL5 mRNA and CCL5 protein expression were determined using real-time PCR and ELISA. The activity of the CCL5 promoter region and nuclear factor (NF)-kappaB was assessed by dual luciferase assay using specific luciferase reporter plasmids. We used actinomycin D to assess the stability of mRNA. Phosphorylation of signal transducer and activator of transcription 1 (STAT-1) was analyzed by Western blot.

RESULTS

Synthetic dsRNA up-regulated the expression of CCL5 mRNA and CCL5 protein. Adding TNF-alpha or IFN-gamma to dsRNA further increased the expression of CCL5. The combination of TNF-alpha and dsRNA cooperatively activated the CCL5 promoter region and the NF-kappaB-specific reporter. IFN-gamma did not activate these reporters. However, it increased the stability of CCL5 mRNA induced by dsRNA. IFN-gamma phosphorylated STAT-1, but dsRNA did not. The effects of IFN-gamma were not evident in the cells transfected with short interfering RNA for STAT-1.

CONCLUSIONS

Cross-talk between TLR3 signaling and inflammatory cytokines regulates the expression of CCL5 in airway epithelial cells. In this mechanism, TNF-alpha may activate NF-kappaB, in cooperation with TLR3 signaling. IFN-gamma may stabilize CCL5 mRNA up-regulated by TLR3. This mechanism may depend on STAT-1.

Asthma: clinical expression and molecular mechanisms

Asthma is a complex disorder that displays heterogeneity and variability in its clinical expression both acutely and chronically. This heterogeneity is influenced by multiple factors including age, sex, socioeconomic status, race and/or ethnicity, and gene by environment interactions. Presently, no precise physiologic, immunologic, or histologic characteristics can be used to definitively make a diagnosis of asthma, and therefore the diagnosis is often made on a clinical basis related to symptom patterns (airways obstruction and hyperresponsiveness) and responses to therapy (partial or complete reversibility) over time. Although current treatment modalities are capable of producing control of symptoms and improvements in pulmonary function in the majority of patients, acute and often severe exacerbations still occur and contribute significantly to both the morbidity and mortality of asthma in all age groups. This review will highlight some of the important clinical features of asthma and emphasize recent advances in both pathophysiology and treatment.

Montelukast does not prevent reactive airway disease in young children hospitalized for RSV bronchiolitis

AIM

To evaluate the long-term effect of montelukast on symptoms of cough and wheeze following RSV bronchiolitis.

METHODS

Fifty eight patients (aged < or = 24 months) hospitalized with a first episode of RSV bronchiolitis were enrolled in this double blind prospective randomized trial comparing montelukast (n = 31) vs placebo (n = 27).

RESULTS

During the 3-month treatment period, there were no statistical significant differences between the two groups for symptom-free days and nights (48.5 [interquartile range 33.0.0-66.0] for montelukast vs 57.0 [29.0-71.0] for placebo p = 0.415) nor disease-free days and nights (44.5 days [26.0-54.0] vs 53.0 [22.3-71.0]; p = 0.266). During the 1 year follow-up, there were 41 exacerbations in the montelukast group vs 54 exacerbations in the placebo group (p = 0.57). Time to first exacerbation was not different. Number of unscheduled visits and need to start inhaled steroids were comparable in the two groups.

CONCLUSION

Treatment with montelukast after hospital admission for RSV bronchiolitis in children younger than 2 years of age did not reduce symptoms of cough and wheeze. We cannot exclude that a subgroup of children may, however, benefit from this treatment.

The severity-dependent relationship of infant bronchiolitis on the risk and morbidity of early childhood asthma

BACKGROUND

Infants hospitalized for bronchiolitis have a high rate of early childhood asthma. It is not known whether bronchiolitis severity correlates with the risk of early childhood asthma or with asthma-specific morbidity.

OBJECTIVES

We sought to determine whether a dose-response relationship exists between severity of infant bronchiolitis and both the odds of early childhood asthma and asthma-specific morbidity.

METHODS

We conducted a population-based retrospective birth cohort study of term healthy infants born from 1995-2000 and enrolled in a statewide Medicaid program. We defined bronchiolitis severity by categorizing infants into mutually exclusive groups based on the most advanced level of health care for bronchiolitis. Health care visits, asthma-specific medications, and demographics were identified entirely from Medicaid and linked vital records files. Asthma was ascertained at between 4 and 5.5 years of age, and 1-year asthma morbidity (hospitalization, emergency department visit, or oral corticosteroid course) was determined between 4.5 and 5.5 years among children with prevalent asthma.

RESULTS

Among 90,341 children, 18% had an infant bronchiolitis visit, and these infants contributed to 31% of early childhood asthma diagnoses. Relative to children with no infant bronchiolitis visit, the adjusted odds ratios for asthma were 1.86 (95% CI, 1.74-1.99), 2.41 (95% CI, 2.21-2.62), and 2.82 (95% CI, 2.61-3.03) in the outpatient, emergency department, and hospitalization groups, respectively. Children hospitalized with bronchiolitis during infancy had increased early childhood asthma morbidity compared with that seen in children with no bronchiolitis visit.

CONCLUSION

To our knowledge, this is the first study to demonstrate the dose-response relationship between the severity of infant bronchiolitis and the increased odds of both early childhood asthma and asthma-specific morbidity.

Mast cell degranulation is induced by A549 airway epithelial cell infected with respiratory syncytial virus

Respiratory syncytial virus (RSV), a major causative agent of respiratory tract infections, influences allergic diseases. Mast cells, important effector cells in allergic disease, also express chemokine (C-X(3)-C motif) receptor 1 (CX(3)CR1). The RSV attachment glycoprotein (G protein) is structurally similar to CX(3)C ligand 1 (CX(3)CL1), the CX(3)CR1 ligand, suggesting that RSV directly interacts with and affects mast cell function, including degranulation. In this paper, the effect of RSV infection on mast cell function was studied using the human mast cell line (HMC-1). The results showed that RSV infection and replication was inefficient in HMC-1 cells than in human epithelial A549 cells. Additionally, HMC-1 degranulation occurred only in coculture with RSV-infected A549 cells, with up-regulation of TNFalpha secretion. However, direct RSV inoculation and incubation with RSV-infected A549 cell culture medium failed to induce HMC-1 degranulation, suggesting that virus-infected cells are critical for degranulation during RSV infection; however, degranulation does not occur by direct RSV infection into mast cells.

Increased mast cell density during the infection with velogenic Newcastle disease virus in chickens

In addition to their well-characterized role in allergic inflammation, recent data confirm that mast cells play a more extensive role in a variety of viral infections. The contribution of mast cells to Newcastle disease pathogenesis has not been investigated. We evaluated mast cell activity after Newcastle disease virus (NDV) infection in specific pathogen free chickens using cytochemical and immunocytochemical analyses. The results were as follows. Severe tissue damage was observed in the proventriculus, duodenum, jejunum and caecal tonsil, and NDV antigens were detected and presented extensively in these tissues. Second, in the NDV-infected group, the mast cell population was increased markedly in the proventriculus, duodenum, jejunum and caecal tonsil at 24, 48, 72 and 96 h after infection (P<0.01). However, very few mast cells were observed in those same tissues in the control. More intriguingly, the greatest number of mast cells was found in the proventriculus, which also showed the greatest level of NDV antigens. Third, the content of tryptase was significantly higher (P<0.01) in the NDV-infected group compared with the control from 24 to 96 h post infection). Furthermore, as an important protease released by mast cells, tryptase had a positive correlation with mast cell distribution. These data indicated that mast cells were involved in the response to NDV. Our results also suggested that the broad range of mast cell mediators might have a role in the pathology of Newcastle disease.

A double-blind, placebo-controlled, randomized trial of montelukast for acute bronchiolitis

BACKGROUND

Cysteinyl leukotrienes are implicated in the inflammation of bronchiolitis. Recently, a specific cysteinyl leukotriene receptor antagonist, montelukast (Singulair [MSD, Haarlem, Netherlands]), has been approved for infants in granule sachets.

OBJECTIVE

Our goal was to evaluate the effect of montelukast on clinical progress and on cytokines in acute bronchiolitis.

METHODS

This was a randomized, placebo-controlled, double-blind, parallel-group study in 2 medical centers. Fifty-three infants (mean age: 3.8+/-3.5 months) with a first episode of acute bronchiolitis were randomly assigned to receive either 4-mg montelukast sachets or placebo, every day, from hospital admission until discharge. The primary outcome was length of stay, and secondary outcomes included clinical severity score (maximum of 12) and changes in type 1 and 2 cytokine levels (including interleukin4/IFN-gamma ratio as a surrogate for the T-helper 2/T-helper 1 ratio) in nasal lavage.

RESULTS

Both groups were comparable at baseline, and cytokine levels correlated positively with disease severity. There were neither differences in length of stay (4.63+/-1.88 [placebo group] vs 4.65+/-1.97 days [montelukast group]) nor in clinical severity score and cytokine levels between the 2 groups. No differences in interleukin 4/IFN-gamma ratio between the 2 groups were seen. There was a slight tendency for infants in the montelukast group to recover more slowly than those in the placebo group (clinical severity score at discharge: 6.1+/-2.4 vs 4.8+/-2.2, respectively).

CONCLUSIONS

Montelukast did not improve the clinical course in acute bronchiolitis. No significant effect of montelukast on the T-helper 2/T-helper 1 cytokine ratio when given in the early acute phase could be demonstrated.

Viral respiratory infection and the link to asthma

Viral respiratory infections are closely associated with wheezing illnesses and exacerbations of asthma throughout childhood, and yet there are a number of remaining questions pertaining to the specific nature of this relationship. Infection with an expanding list of respiratory viruses is an important cause of acute wheezing in infancy, and viruses are detected in most exacerbations of asthma throughout childhood. Furthermore, infants who develop severe viral respiratory infections are more likely to have asthma later in childhood. There has been progress in understanding the pathogenesis of viral respiratory illnesses, and this has led to new insights into how these processes might differ in asthma. Several host factors, including respiratory allergy and virus-induced interferon responses, modify the risk of virus-induced wheezing. In the absence of effective antiviral therapies, treatment of virus-induced wheezing and exacerbations of asthma can be challenging, and studies evaluating current treatment strategies are reviewed. Understanding the host-pathogen interactions that determine the severity of respiratory illnesses and long-term sequelae is likely to be of great help in identifying at-risk individuals, and in designing new and more effective treatments.

A single versus multiple doses of dexamethasone in infants wheezing for the first time

RATIONALE

Corticosteroid therapy is not routinely recommended in true bronchiolitis. However, since bronchiolitis and the first asthma attack are impossible to distinguish, some infants with the first wheezing episode receive corticosteroids. Optimal duration of corticosteroid therapy in this scenario is unknown. This study compared efficacy of multiple administrations and a single dose of dexamethasone in bronchiolitis.

METHODS

In this randomized double blind trial, previously healthy outpatients 2-23 months of age with bronchiolitis and Respiratory Disease Assessment Instrument (RDAI) score 6 or more received 1 mg/kg of oral dexamethasone in the Emergency Department. Prior to discharge at 4 hr they were randomized to either 4 daily doses of dexamethasone 0.15 mg/kg or placebo equivalent. Primary outcome was the proportion of subsequent hospitalizations or prescribed trials of bronchodilator/corticosteroid therapy for dyspnea by day 6 in the groups. Secondary outcomes were changes in the RDAI to day 6, and proportions with unscheduled visits by days 6 and 28.

RESULTS

The rate of primary outcome in the single dose group (SDG, N = 64) was 9/64 or 14.1% versus 7/61 or 11.5% in the multiple dose group (MDG, N = 61) [95% CI 0.09; 0.14]. Twelve (18.8%) children in the SDG had unscheduled medical visits by day 6 versus 11 (18.0%) children in the MDG [95% CI 0.13; 0.14]. On day 6 the RDAI decreased from 9.5 +/- 2.1 to 2.1 +/- 2.4 in the SDG and from 9.8 +/- 2.2 to 1.6 +/- 2.3 in the MDG [95% CI 0.36; 2.06]. Between days 7-28, 24/64 (37.5%) SDG infants returned for care versus 20/61 (32.8%) of the MDG [95% CI 0.12; 0.21].

CONCLUSIONS

Our study suggests that, in outpatients with bronchiolitis who receive dexamethasone, continuation of this agent beyond the initial dose does not provide significant benefit.

The immune response to respiratory syncytial virus infection: friend or foe?

The immune response to respiratory syncytial virus (RSV) infection has fascinated and frustrated investigators for decades. After adverse responses to early attempts at vaccination, it became popularly held that disease following infection was related to overly aggressive immune responses. However, recent data illustrate that severe forms of disease are related to inadequate, rather than hyperresponsive, adaptive immune reactions. Thus, recovery from primary (and perhaps later) RSV infection is dependent on the quality of innate immune responses. These findings should have enormous significance to the development of vaccines and antiviral compounds.

Effect of secondhand cigarette smoke, RSV bronchiolitis and parental asthma on urinary cysteinyl LTE4

Cysteinyl leukotrienes promote airway inflammation, bronchoconstriction and mucus hypersecretion. Cigarette smoking and respiratory syncytial virus (RSV) bronchiolitis are known to increase urinary cysteinyl leukotriene E4 (uLTE4), the end product of the cysteinyl leukotriene biosynthetic pathway. We tested the following hypotheses: (1) Secondhand smoke (SHS) exposure increases uLTE4 in well infants and in those hospitalized for RSV bronchiolitis; (2) Length of hospital stay for those with RSV bronchiolitis correlates with uLTE4; and (3) Infants with parent(s) with asthma will have higher uLTE4. Parental asthma for infants hospitalized with RSV bronchiolitis (n = 79) and Well babies (n = 31) was determined by questionnaire. Urine was analyzed for LTE4, cotinine, and creatinine. SHS exposure was determined by cotinine to creatinine ratio. Chi square, or t-tests were used to determine significant differences between two groups. A three-way analysis of variance compared the effects of SHS exposure and parental asthma on uLTE4 in Well versus RSV babies. Independent variables predicting length of hospital stay were determined by stepwise multiple regression. High SHS exposure and RSV significantly increased uLTE4. The SHS induced increase in uLTE4 was seen in infants with no parental asthma but not in those with parental asthma. Length of hospital stay positively correlated with uLTE4. We concluded that SHS exposure may increase the severity of bronchiolitis in RSV-infected infants by enhancing production of cysLTs in infants with no parental asthma.