Virus infection-induced bronchial asthma exacerbation

Bronchoconstriction damages airway epithelia by crowding-induced excess cell extrusion

Asthma is deemed an inflammatory disease, yet the defining diagnostic feature is mechanical bronchoconstriction. We previously discovered a conserved process called cell extrusion that drives homeostatic epithelial cell death when cells become too crowded. In this work, we show that the pathological crowding of a bronchoconstrictive attack causes so much epithelial cell extrusion that it damages the airways, resulting in inflammation and mucus secretion in both mice and humans. Although relaxing the airways with the rescue treatment albuterol did not affect these responses, inhibiting live cell extrusion signaling during bronchoconstriction prevented all these features. Our findings show that bronchoconstriction causes epithelial damage and inflammation by excess crowding-induced cell extrusion and suggest that blocking epithelial extrusion, instead of the ensuing downstream inflammation, could prevent the feed-forward asthma inflammatory cycle.

Interplay between hypoxia and inflammation contributes to the progression and severity of respiratory viral diseases

History of pandemics is dominated by viral infections and specifically respiratory viral diseases like influenza and COVID-19. Lower respiratory tract infection is the fourth leading cause of death worldwide. Crosstalk between resultant inflammation and hypoxic microenvironment may impair ventilatory response of lungs. This reduces arterial partial pressure of oxygen, termed as hypoxemia, which is observed in a section of patients with respiratory virus infections including SARS-CoV-2 (COVID-19). In this review, we describe the interplay between inflammation and hypoxic microenvironment in respiratory viral infection and its contribution to disease pathogenesis.

Immunological Aspects Related to Viral Infections in Severe Asthma and the Role of Omalizumab

Viral respiratory infections are recognized risk factors for the loss of control of allergic asthma and the induction of exacerbations, both in adults and children. Severe asthma is more susceptible to virus-induced asthma exacerbations, especially in the presence of high IgE levels. In the course of immune responses to viruses, an initial activation of innate immunity typically occurs and the production of type I and III interferons is essential in the control of viral spread. However, the Th2 inflammatory environment still appears to be protective against viral infections in general and in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections as well. As for now, literature data, although extremely limited and preliminary, show that severe asthma patients treated with biologics don't have an increased risk of SARS-CoV-2 infection or progression to severe forms compared to the non-asthmatic population. Omalizumab, an anti-IgE monoclonal antibody, exerts a profound cellular effect, which can stabilize the effector cells, and is becoming much more efficient from the point of view of innate immunity in contrasting respiratory viral infections. In addition to the antiviral effect, clinical efficacy and safety of this biological allow a great improvement in the management of asthma.

The Effect of Unconventional Cytokine Combinations on NK-Cell Responses to Viral Infection

Cytokines are soluble and membrane-bound factors that dictate immune responses. Dogmatically, cytokines are divided into families that promote type 1 cell-mediated immune responses (e.g., IL-12) or type 2 humoral responses (e.g., IL-4), each capable of antagonizing the opposing family of cytokines. The discovery of additional families of cytokines (e.g., IL-17) has added complexity to this model, but it was the realization that immune responses frequently comprise mixtures of different types of cytokines that dismantled this black-and-white paradigm. In some cases, one type of response may dominate these mixed milieus in disease pathogenesis and thereby present a clear therapeutic target. Alternatively, synergistic or blended cytokine responses may obfuscate the origins of disease and perplex clinical decision making. Most immune cells express receptors for many types of cytokines and can mediate a myriad of functions important for tolerance, immunity, tissue damage, and repair. In this review, we will describe the unconventional effects of a variety of cytokines on the activity of a prototypical type 1 effector, the natural killer (NK) cell, and discuss how this may impact the contributions of these cells to health and disease.

Enhanced airway hyperresponsiveness in asthmatic children and mice with A(H1N1)pdm09 infection

BACKGROUND

Severe asthma exacerbation is an important comorbidity of the 2009 HIN1 pandemic (A(H1N1)pdm09) in asthmatic patients. However, the mechanisms underlying severe asthma exacerbation remain unknown. In this study, airway hyperresponsiveness (AHR) was measured in pediatric asthma patients infected with A(H1N1)pdm09. We also evaluated AHR in asthmatic mice with A(H1N1)pdm09 infection and those with seasonal influenza for comparison.

METHODS

AHRs in asthmatic children were defined as the provocative acetylcholine concentration causing a 20% reduction in forced expiratory volume in 1 s (PC₂₀ ). To investigate the pathophysiology using animal models, BALB/c mice aged 6-8 weeks were sensitized and challenged with ovalbumin. Either mouse-adapted A(H1N1)pdm09, seasonal H1N1 virus (1 × 10⁵ pfu/20 μl), or mock treatment as a control was administered intranasally. At 3, 7, and 10 days after infection, each group of mice was evaluated for AHR by methacholine challenge using an animal ventilator, flexiVent. Lung samples were resected and observed using light microscopy to assess the degree of airway inflammation.

RESULTS

AHRs in the children with bronchial asthma were temporarily increased, and alleviated by 3 months after discharge. AHR was significantly enhanced in A(H1N1)pdm09-infected asthmatic mice compared to that in seasonal H1N1-infected mice (p < .001), peaking at 7 days postinfection and then becoming similar to control levels by 10 days postinfection. Histopathological examination of lung tissues showed more intense infiltration of inflammatory cells and severe tissue destruction in A(H1N1)pdm09-infected mice at 7 days postinfection than at 10 days postinfection.

CONCLUSION

Our results suggest that enhanced AHR could contribute to severe exacerbation in human asthmatic patients with A(H1N1)pdm09 infection.

Effect of peramivir on respiratory symptom improvement in patients with influenza virus infection and pre-existing chronic respiratory disease: Findings of a randomized, open-label study

Background

The efficacy of neuraminidase inhibitors on improvement of respiratory symptoms triggered by influenza in patients with pre‐existing chronic respiratory diseases is unknown.

Methods

This 2‐week, randomized, open‐label study evaluated intravenous peramivir 600 mg on two consecutive days (peramivir‐repeat), peramivir 300 mg single dose (peramivir‐single), and oral oseltamivir 75 mg twice daily for 5 days in patients with confirmed influenza and chronic respiratory diseases. Patients recorded symptom scores daily. The primary endpoint of cumulative area of time vs symptoms (CATVS) was expressed as an index value of area under the curve vs time of the total score of cough, sore throat, and nasal congestion from baseline to 2 weeks.

Results

Of 214 randomized patients, 209 (56% female, 77% aged <65 years, 94% outpatients, 91% bronchial asthma, 62% influenza A) received ≥1 dose of study drug. Mean (standard deviation) CATVS was similar for peramivir‐repeat (782.78 [487.17]) vs peramivir‐single (717.35 [347.55]; P = .4371), and for peramivir‐repeat vs oseltamivir (856.34 [404.99]; P = 1.00). However, CATVS was significantly shorter for peramivir‐single vs oseltamivir, with an estimated treatment difference (TD) of −145.07 (95% confidence interval: −284.57, −5.56; P = .0416). In subgroup analyses, CATVS was significantly shorter for peramivir‐single vs oseltamivir among patients with influenza A (TD: −206.31 [−383.86, −28.76]; P = .0231), bronchial asthma (TD: −156.57 [−300.22, −12.92]; P = .0328), baseline respiratory severity score <5 (TD: −265.32 [−470.42, −60.21]; P = .0120), and age <65 (TD: −184.30 [−345.08, −23.52]; P = .0249).

Conclusions

In patients with chronic respiratory diseases, peramivir‐single was not significantly different from peramivir‐repeat and was more effective than oseltamivir at alleviating respiratory symptoms.

Dietary Fatty Acids Amplify Inflammatory Responses to Infection through p38 MAPK Signaling

Obesity is an important risk factor for severe asthma exacerbations, which are mainly caused by respiratory infections. Dietary fatty acids, which are increased systemically in obese patients and are further increased after high-fat meals, affect the innate immune system and may contribute to dysfunctional immune responses to respiratory infection. In this study we investigated the effects of dietary fatty acids on immune responses to respiratory infection in pulmonary fibroblasts and a bronchial epithelial cell line (BEAS-2B). Cells were challenged with BSA-conjugated fatty acids (ω-6 polyunsaturated fatty acids [PUFAs], ω-3 PUFAs, or saturated fatty acids [SFAs]) +/- the viral mimic polyinosinic:polycytidylic acid (poly[I:C]) or bacterial compound lipoteichoic acid (LTA), and release of proinflammatory cytokines was measured. In both cell types, challenge with arachidonic acid (AA) (ω-6 PUFA) and poly(I:C) or LTA led to substantially greater IL-6 and CXCL8 release than either challenge alone, demonstrating synergy. In epithelial cells, palmitic acid (SFA) combined with poly(I:C) also led to greater IL-6 release. The underlying signaling pathways of AA and poly(I:C)- or LTA-induced cytokine release were examined using specific signaling inhibitors and IB. Cytokine production in pulmonary fibroblasts was prostaglandin dependent, and synergistic upregulation occurred via p38 mitogen-activated protein kinase signaling, whereas cytokine production in bronchial epithelial cell lines was mainly mediated through JNK and p38 mitogen-activated protein kinase signaling. We confirmed these findings using rhinovirus infection, demonstrating that AA enhances rhinovirus-induced cytokine release. This study suggests that during respiratory infection, increased levels of dietary ω-6 PUFAs and SFAs may lead to more severe airway inflammation and may contribute to and/or increase the severity of asthma exacerbations.

Viruses and non-allergen environmental triggers in asthma

Asthma is a complex inflammatory disease with many triggers. The best understood asthma inflammatory pathways involve signals characterized by peripheral eosinophilia and elevated immunoglobulin E levels (called T2-high or allergic asthma), though other asthma phenotypes exist (eg, T2-low or non-allergic asthma, eosinophilic or neutrophilic-predominant). Common triggers that lead to poor asthma control and exacerbations include respiratory viruses, aeroallergens, house dust, molds, and other organic and inorganic substances. Increasingly recognized non-allergen triggers include tobacco smoke, small particulate matter (eg, PM2.5), and volatile organic compounds. The interaction between respiratory viruses and non-allergen asthma triggers is not well understood, though it is likely a connection exists which may lead to asthma development and/or exacerbations. In this paper we describe common respiratory viruses and non-allergen triggers associated with asthma. In addition, we aim to show the possible interactions, and potential synergy, between viruses and non-allergen triggers. Finally, we introduce a new clinical approach that collects exhaled breath condensates to identify metabolomics associated with viruses and non-allergen triggers that may promote the early management of asthma symptoms.

Low-Dose Carbon Monoxide Inhibits Rhinovirus Replication in Human Alveolar and Airway Epithelial Cells

Carbon monoxide (CO) and nitric oxide (NO) exhibit physiological properties that include the activation of guanylate cyclase. NO inhibits replication of rhinovirus (RV), a major cause of the common cold and exacerbation of bronchial asthma and chronic obstructive pulmonary disease. However, the anti-rhinoviral effects of CO remain unclear. This study investigated whether the exogenous application of low-dose CO could inhibit RV replication in human alveolar and airway epithelial cells. A549 human lung carcinoma cells with alveolar epithelial features and primary cultures of human tracheal epithelial (HTE) cells were pretreated with CO (100 ppm) and infected with a major group RV, type 14 RV (RV14). CO exposure reduced RV14 titers in the supernatants and RV RNA levels in A549 and HTE cells. The treatment with a guanylate cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, reversed the inhibitory effects of CO exposure on RV14 replication in A549 cells. Pretreatment of A549 cells with 8-Br-cGMP, a cell-permeable cGMP analog, caused the decrease in RV14 replication, while CO exposure increased cGMP production. CO exposure also increased the expression levels of interferon (IFN)-γ mRNA and protein. In contrast, pretreatment with CO did not increase DNA fragmentation and did not reduce the expression of intercellular adhesion molecule-1, the RV14 receptor, or the number of acidic endosomes, through which RV RNA enters the cytoplasm. These findings suggest that low-dose CO may decrease RV14 replication in alveolar and airway epithelial cells. IFN-γ production, which is induced by CO exposure via guanylate cyclase activation-mediated cGMP production, may be involved in RV14 replication inhibition.

Distal respiratory tract viral infections in young children trigger a marked increase in alveolar mast cells

Viral infections predispose to the development of childhood asthma, a disease associated with increased lung mast cells (MCs). This study investigated whether viral lower respiratory tract infections (LRTIs) can already evoke a MC response during childhood.

Lung tissue from young children who died following LRTIs were processed for immunohistochemical identification of MCs. Children who died from nonrespiratory causes served as controls. MCs were examined in relation to sensitisation in infant mice exposed to allergen during influenza A infection.

Increased numbers of MCs were observed in the alveolar parenchyma of children infected with LRTIs (median (range) 12.5 (0–78) MCs per mm²) compared to controls (0.63 (0–4) MCs per mm², p=0.0005). The alveolar MC expansion was associated with a higher proportion of CD34⁺ tryptase⁺ progenitors (controls: 0% (0–1%); LRTIs: 0.9% (0–3%) CD34⁺ MCs (p=0.01)) and an increased expression of the vascular cell adhesion molecule (VCAM)-1 (controls: 0.2 (0.07–0.3); LRTIs: 0.3 (0.02–2) VCAM-1 per mm² (p=0.04)). Similarly, infant mice infected with H1N1 alone or together with house dust mite (HDM) developed an increase in alveolar MCs (saline: 0.4 (0.3–0.5); HDM: 0.6 (0.4–0.9); H1N1: 1.4 (0.4–2.0); HDM+H1N1: 2.2 (1.2–4.4) MCs per mm² (p<0.0001)). Alveolar MCs continued to increase and remained significantly higher into adulthood when exposed to H1N1+HDM (day 36: 2.2 (1.2–4.4); day 57: 4.6 (1.6–15) MCs per mm² (p=0.01)) but not when infected with H1N1 alone.

Our data demonstrate that distal viral infections in young children evoke a rapid accumulation of alveolar MCs. Apart from revealing a novel immune response to distal infections, our data may have important implications for the link between viral infections during early childhood and subsequent asthma development.

Viral infections in children evokes a rapid recruitment and accumulation of mast cells in the alveolar parenchymahttp://ow.ly/i9eN30meNM7

Temporal and spatial associations between influenza and asthma hospitalisations in New York City from 2002 to 2012: a longitudinal ecological study

OBJECTIVES

To determine whether asthma hospitalisations of children and adults in the five boroughs of New York City are correlated with influenza hospitalisations temporally and spatially.

DESIGN

A longitudinal ecological study.

INCLUSION CRITERIA

We reviewed the Statewide Planning and Research Cooperative System's records of hospitalisations in Manhattan, Bronx, Queens, Brooklyn and Staten Island from 2002 to 2012. All hospitalisations with a primary diagnosis of either asthma or influenza were identified using the International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes.

METHODS

A time-series regression analysis was performed using aggregate monthly counts of influenza hospitalisations as predictors of asthma hospitalisations. Time-series regression models were also applied to different age groups and boroughs to examine the magnitude of influenza and asthma correlations across strata. The per cent excess risk was also calculated across age groups and boroughs.

RESULTS

Time-series analysis of the overall population revealed a significant positive correlation between influenza and asthma hospitalisations (p=0.011). When stratifying by age, there was a significant positive correlation between asthma and influenza hospitalisations for individuals 18 and older (p<0.01), and no significant correlation found for age groups younger than 18. Percentages of excess risk of influenza-related asthma hospitalisations also increased with increasing age with adults 18-44, 45-64 and 65+ having excess risk percentages of 2.9%, 3.4% and 4%, respectively. Time-series analysis by location revealed positive significant correlations between asthma and influenza hospitalisations in Brooklyn (p=0.03) and Manhattan (p<0.01). Manhattan and Brooklyn had a 2.5% and 1.6%, respectively, percentage of excess risk of influenza-related asthma hospitalisations.

CONCLUSION

Influenza and asthma hospitalisations are significantly associated at the population level among adults. These associations vary by age and geographical location. Influenza prevention strategies targeting adult populations, particularly individuals living in Manhattan and Brooklyn, have the potential for meaningful reduction of influenza-related asthma hospitalisations.

Mast cells contribute to Enterovirus 71 infection-induced pulmonary edema in neonatal mice

Enterovirus (EV) 71 infection has been widely acknowledged as the leading cause of severe hand, foot and mouth disease (HFMD), which may rapidly lead to fatal pulmonary edema. In this study, we established a mouse model for EV71 infection exhibiting high incidence of severe symptoms with pulmonary edema. Mast cells (MCs) accumulation, activation and allergic inflammation were found in the brains, lungs and skeletal muscle of mice after EV71 infection, especially in the lungs of mice. Levels of histamine, platelet-activating factor (PAF), interleukin (IL)-4, IL-5, IL-13, tumor necrosis factor-α (TNF-α), nitric oxide (NO), endocrine gland-derived vascular endothelial growth factor (EG-VEGF) and noradrenaline (NA) were increased in EV71-infected lungs. In addition, EV71 infection reduced the number of pulmonary T cells, dendritic cells (DCs) and monocytes, and increased the number of lung eosinophils, Tregs and MCs. MCs number and tryptase expression in target organs or tissues posed a trend towards an increase from control to severe mice. There were positive correlations between MCs number in the brains (r = 0.701, P = 0.003), lungs (r = 0.802, P < 0.0001), skeletal muscles (r = 0.737, P = 0.001) and mean clinical score. Thus, our results suggested that MCs contributed to the pulmonary edema during EV71 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.

Clarithromycin decreases rhinovirus replication and cytokine production in nasal epithelial cells from subjects with bronchial asthma: effects on IL-6, IL-8 and IL-33

Rhinoviral infection is associated with an increased risk of asthma attacks. The macrolide clarithromycin decreases cytokine production in nasopharyngeal aspirates from patients with wheezing, but the effects of macrolides on cytokine production in nasal epithelial cells obtained from asthmatic subjects remain unclear. Here, human nasal epithelial cells were infected with type-14 rhinovirus (RV14), a major RV group. Titers and RNA of RV14 and cytokine concentrations, including IL-1β and IL-6, were higher in the supernatants of the cells obtained from subjects with bronchial asthma (asthmatic group) than in those from the non-asthmatic group. Pretreatment with clarithromycin decreased RV14 titers, viral RNA and cytokine concentrations, and susceptibility to RV14 infection. Pretreatment with clarithromycin also decreased IL-33 production, which was detected after infection. Pretreatment with clarithromycin decreased the expression of intercellular adhesion molecule-1, the receptor for RV14, after infection, the number and fluorescence intensity of the acidic endosomes through which RV RNA enters the cytoplasm, and the activation of nuclear factor kappa-B proteins in nuclear extracts. These findings suggested that RV replication and cytokine production may be enhanced in nasal epithelial cells obtained from subjects with bronchial asthma and may be modulated by clarithromycin.

Infection in severe asthma exacerbations and critical asthma syndrome

In chronic persistent asthma and severe acute exacerbations of bronchial asthma, infectious agents are the predominant triggers that drive disease and airway pathobiology. In acute exacerbations of bronchial asthma (AEBA) including near fatal and fatal asthma, viral agents, particularly human rhinovirus-C, respiratory syncytial virus and influenza A appear to be the more prevalent and recurring threats. Both viral, and to a lesser extent bacterial agents, can play a role, and co-infection may also be present and worsen prognosis in hospitalized patients, placing a portion at risk for critical asthma syndrome. During severe acute exacerbations, infectious agents must be treated empirically, but the initial treatment regimens can vary and viral coverage may also vary based on seasonality and patient age. Early treatment with ceftriaxone and azithromycin, along with oseltamivir in winter months, should be initiated with all cases of severe exacerbations where infection is suspected, and definitely in critical asthma syndrome until infection is excluded by appropriate diagnostic testing. In this manuscript we will outline the impact of the major viral agents on severe asthma including the data from the 2009 H1N1 influenza pandemic. The role of bacterial infections in acute exacerbations of asthma will also be reviewed as well as the benefit of empiric antibiotics and the role of macrolides in both acute and chronic asthma.

Temporal trends and factors associated with pediatric hospitalizations with respiratory infection

OBJECTIVES

Asthma is the leading cause of emergency room visits in children, and those with asthma tend to suffer from more severe consequences of respiratory tract infections. The aims of this study were among children who required hospitalization, compare differences between those admitted with or without respiratory infection, describe changes in yearly proportion of asthma among the children admitted with a respiratory infection in New York City from 2006 to 2012 and ascertain how asthma affected the average length of hospital stay for those with respiratory infection.

METHODS

We conducted an historical prospective study using data obtained from multiple electronic sources of patients discharged from a 200-bed pediatric hospital in a major metropolitan healthcare system between 2006 and 2012. Patient characteristics were obtained from electronic health records and billing codes.

RESULTS

Among 83,348 patient discharges, there were 5057 (6.1%) with a respiratory infection. In the multivariable model, children with the following characteristics were significantly more likely to be admitted with a respiratory infection as compared with other diagnoses: asthma [odds ratio (OR) 4.68 (95% confidence limits (CL): 4.31, 5.08], male sex [OR:1.11 (1.05, 1.18)], prior hospitalization [OR: 3.65 (3.43, 3.89)], renal failure [(OR: 2.14 (1.70, 2.70)] and Medicaid coverage [OR: 1.93 (1.81, 2.05)]. Children aged ≥ 5 years (OR: 0.44 (0.41, 0.47) and those with diabetes (OR: 0.32 (0.21, 0.51) were less likely to be admitted with a respiratory infection. Hospitalized patients with respiratory infection and asthma, identified by ICD-9 codes, had significantly shorter lengths of stay than patients without asthma, 5.3 and 9.0 days, respectively, p < 0.001. Asthma in patients admitted with a respiratory infection increased from 19.2% in 2006 to 28.2% in 2012, peaking at 34.1% in 2010 (p < 0.001).

CONCLUSION

This study suggests that asthma is a significant risk factor for hospitalization of children with respiratory infection, and suggests that the prevalence of asthma is increasing over time among children hospitalized with respiratory infection in this urban setting.

Mast cells and influenza a virus: association with allergic responses and beyond

Influenza A virus (IAV) is a widespread infectious agent commonly found in mammalian and avian species. In humans, IAV is a respiratory pathogen that causes seasonal infections associated with significant morbidity in young and elderly populations, and has a large economic impact. Moreover, IAV has the potential to cause both zoonotic spillover infection and global pandemics, which have significantly greater morbidity and mortality across all ages. The pathology associated with these pandemic and spillover infections appear to be the result of an excessive inflammatory response leading to severe lung damage, which likely predisposes the lungs for secondary bacterial infections. The lung is protected from pathogens by alveolar epithelial cells, endothelial cells, tissue resident alveolar macrophages, dendritic cells, and mast cells. The importance of mast cells during bacterial and parasitic infections has been extensively studied; yet, the role of these hematopoietic cells during viral infections is only beginning to emerge. Recently, it has been shown that mast cells can be directly activated in response to IAV, releasing mediators such histamine, proteases, leukotrienes, inflammatory cytokines, and antiviral chemokines, which participate in the excessive inflammatory and pathological response observed during IAV infections. In this review, we will examine the relationship between mast cells and IAV, and discuss the role of mast cells as a potential drug target during highly pathological IAV infections. Finally, we proposed an emerging role for mast cells in other viral infections associated with significant host pathology.

Screening and functional pathway analysis of genes associated with pediatric allergic asthma using a DNA microarray

The present study aimed to identify differentially expressed genes (DEGs) associated with pediatric allergic asthma, and to analyze the functional pathways of the selected target genes, in order to explore the pathogenesis of the disease. The GSE18965 gene expression profile was downloaded from the Gene Expression Omnibus database and was preprocessed. This gene expression profile consisted of seven normal samples and nine samples from patients with pediatric allergic asthma. The DEGs between the normal and pediatric allergic asthma samples were screened using limma package in R, and the cut‑off value was set at false discovery rate <0.05 and log fold change >1. Following hierarchical clustering of the DEGs based on the expression profiles, the up‑ and downregulated genes underwent a functional enrichment analysis by topological approach (P<0.05), using the Database for Annotation, Visualization and Integrated Discovery. A total of 127 DEGs were identified between the normal and pediatric allergic asthma samples. The up‑ and downregulated genes were significantly enriched in the actin filament‑based process and the monosaccharide metabolic process, respectively. Seven downregulated DEGs (M6PR, TPP1, GLB1, NEU1, ACP2, LAMP1 and HGSNAT) were identified in the lysosomal pathway, with P=6.4x10(‑9). These results suggested that variation in lysosomal function, triggered by the seven downregulated genes, may lead to aberrant functioning of the T lymphocytes, resulting in asthma. Further research regarding the treatment of pediatric allergic asthma through targeting lysosomal function is required.

Natural antibody repertoires: development and functional role in inhibiting allergic airway disease

In this review we discuss the effects of microbial exposure on the B cell repertoire. Neonatal exposure to conserved bacterial carbohydrates and phospholipids permanently reprograms the natural antibody repertoire directed toward these antigens by clonal expansion, alterations in clonal dominance, and increased serum antibody levels. These epitopes are present not only in bacterial cell walls, but also in common environmental allergens. Neonatal immunization with bacterial polysaccharide vaccines results in attenuated allergic airway responses to fungi-, house dust mite-, and cockroach-associated allergens in mouse models. The similarities between mouse and human natural antibody repertoires suggest that reduced microbial exposure in children may have the opposite effect, providing a potential mechanistic explanation for the hygiene hypothesis. We propose that understanding the effects of childhood infections on the natural antibody repertoire and the mechanisms of antibody-mediated immunoregulation observed in allergy models will lead to the development of prevention/interventional strategies for treatment of allergic asthma.

Acute effects of viral respiratory tract infections on sputum bacterial density during CF pulmonary exacerbations

Background

Airway proliferation of Pseudomonas aeruginosa bacteria is thought to trigger CF exacerbations and may be affected by the presence of viral infections.

Methods

A 2-year prospective study was conducted on 35 adults with CF. P. aeruginosa sputum density was analyzed during stable, exacerbation and post exacerbation assessments. Upon exacerbation, samples were sent for PCR detection of respiratory viruses and the sputum density of P. aeruginosa in patients with a viral infection versus those without was compared.

Results

Twenty-two patients experienced 30 exacerbations during the study period; 50% were associated with a viral infection. There was no change in sputum density of P. aeruginosa from the stable to exacerbation state when measured by quantitative culture or by PCR. Virus-associated exacerbations did not result in significant increases in P. aeruginosa sputum density compared to non-viral exacerbations.

Conclusion

Sputum density of P. aeruginosa was not increased at the time of CF exacerbation and was not influenced by the presence of viral infection.

Respiratory viral infection, epithelial cytokines, and innate lymphoid cells in asthma exacerbations

Exacerbations of asthma are most commonly triggered by viral infections, which amplify allergic inflammation. Cytokines released by virus-infected AECs may be important in driving this response. This review focuses on accumulating evidence in support of a role for epithelial cytokines, including IL-33, IL-25, and TSLP, as well as their targets, type 2 innate lymphoid cells (ILC2s), in the pathogenesis of virus-induced asthma exacerbations. Production and release of these cytokines lead to recruitment and activation of ILC2s, which secrete mediators, including IL-5 and IL-13, which augment allergic inflammation. However, little information is currently available about the induction of these responses by the respiratory viruses that are strongly associated with exacerbations of asthma, such as rhinoviruses. Further human studies, as well as improved animal experimental models, are needed to investigate appropriately the pathogenetic mechanisms in virus-induced exacerbations of asthma, including the role of ILCs.

Epidemiology of virus-induced asthma exacerbations: with special reference to the role of human rhinovirus

Viral respiratory infections may be associated with the virus-induced asthma in adults as well as children. Particularly, human rhinovirus is strongly suggested a major candidate for the associations of the virus-induced asthma. Thus, in this review, we reviewed and focused on the epidemiology, pathophysiology, and treatment of virus-induced asthma with special reference on human rhinovirus. Furthermore, we added our preliminary data regarding the clinical and virological findings in the present review.

Deficiency of melanoma differentiation-associated protein 5 results in exacerbated chronic postviral lung inflammation

RATIONALE

Respiratory viral infections can result in the establishment of chronic lung diseases. Understanding the early innate immune mechanisms that participate in the development of chronic postviral lung disease may reveal new targets for therapeutic intervention. The intracellular viral sensor protein melanoma differentiation-associated protein 5 (MDA5) sustains the acute immune response to Sendai virus, a mouse pathogen that causes chronic lung inflammation, but its role in the development of postviral chronic lung disease is unknown.

OBJECTIVES

To establish the role of MDA5 in the development of chronic lung disease.

METHODS

MDA5-deficient or control mice were infected with Sendai virus. The acute inflammatory response was evaluated by profiling chemokine and cytokine expression and by characterizing the composition of the cellular infiltrate. The impact of MDA5 on chronic lung pathology and function was evaluated through histological studies, degree of oxygen saturation, and responsiveness to carbachol.

MEASUREMENTS AND MAIN RESULTS

MDA5 deficiency resulted in normal virus replication and in a distinct profile of chemokines and cytokines that associated with acute lung neutropenia and enhanced accumulation of alternatively activated macrophages. Diminished expression of neutrophil-recruiting chemokines was also observed in cells infected with influenza virus, suggesting a key role of MDA5 in driving the early accumulation of neutrophils at the infection site. The biased acute inflammatory response of MDA5-deficient mice led to an enhanced chronic lung inflammation, epithelial cell hyperplasia, airway hyperreactivity, and diminished blood oxygen saturation.

CONCLUSIONS

MDA5 modulates the development of chronic lung inflammation by regulating the early inflammatory response in the lung.

A GM-CSF/IL-33 pathway facilitates allergic airway responses to sub-threshold house dust mite exposure

Allergic asthma is a chronic immune-inflammatory disease of the airways. Despite aeroallergen exposure being universal, allergic asthma affects only a fraction of individuals. This is likely related, at least in part, to the extent of allergen exposure. Regarding house dust mite (HDM), we previously identified the threshold required to elicit allergic responses in BALB/c mice. Here, we investigated the impact of an initial immune perturbation on the response to sub-threshold HDM exposure. We show that transient GM-CSF expression in the lung facilitated robust eosinophilic inflammation, long-lasting antigen-specific Th2 responses, mucus production and airway hyperresponsiveness. This was associated with increased IL-33 levels and activated CD11b⁺ DCs expressing OX40L. GM-CSF-driven allergic responses were significantly blunted in IL-33-deficient mice. IL-33 was localized on alveolar type II cells and in vitro stimulation of human epithelial cells with GM-CSF enhanced intracellular IL-33 independently of IL-1α. Likewise, GM-CSF administration in vivo resulted in increased levels of IL-33 but not IL-1α. These findings suggest that exposures to environmental agents associated with GM-CSF production, including airway infections and pollutants, may decrease the threshold of allergen responsiveness and, hence, increase the susceptibility to develop allergic asthma through a GM-CSF/IL-33/OX40L pathway.

Influenza A(H1N1)pdm09 virus and asthma

Respiratory viral infection is a major cause of asthma exacerbations in both children and adults. Among the respiratory viruses, influenza virus is a particularly important pathogen due to its enormous morbidity and mortality in annual epidemics. The swine-origin influenza A virus, designated as A(H1N1)pdm09, emerged in the spring of 2009 and caused the first influenza pandemic in the 21st century. With the emergence of the novel A(H1N1)pdm09 virus, numerous epidemiologic studies detected asthma as a frequent comorbid condition in patients infected with this virus. Here we review recent reports regarding asthma in patients infected with influenza A(H1N1)pdm09 virus, and we discuss the utility of influenza vaccines and antivirals.

Cytokine production and signaling pathways in respiratory virus infection

It has been confirmed that respiratory virus infections can induce abberant cytokine production in the host. These cytokines may be associated with both elimination of the virus and complications in the host, such as virus-induced asthma. Representative host defense mechanisms against pathogens, including bacteria and viruses, are mediated by the innate immune system. Cells of the innate immune system express essential molecules, namely pattern recognition receptors (PRRs), such as Toll-like receptors, nucleotide-binding oligomerization domain-like receptors, and retinoic acid-inducible gene-I-like receptors. These PRRs can recognize components of pathogens such as bacterial lipopolysaccharide, viral antigens, and their genomes (DNA and RNA). Furthermore, PRRs activate various signaling pathways resulting in cytokine production against pathogen infection. However, the exact mechanisms remain unknown. In this review, we mainly focus on the representative mechanisms of cytokine production through PRRs and signaling pathways due to virus infections, including respiratory virus infections. In addition, we describe the relationships between respiratory infections and virus-induced asthma.

Activation of basophils by the double-stranded RNA poly(A:U) exacerbates allergic inflammation

BACKGROUND

It is commonly acknowledged that asthma is exacerbated by viral infections. On the other hand, basophil infiltration of lung tissues has been evidenced postmortem in cases of fatal disease, raising the question of a possible link between these two observations.

OBJECTIVES

Herein, we addressed the relationship between asthma exacerbation by viral infection and basophil activation and expansion by investigating how stimulation with the dsRNA polyadenylic/polyuridylic acid [poly(A:U)] affected basophil activities and recruitment in an allergic airway inflammation model.

METHODS

The effect of dsRNA on basophils was assessed by measuring the cytokine levels produced upon stimulation. We used an OVA-induced experimental model of allergic asthma. Airway hyperreactivity, recruitment of infiltrating cells, and cytokine production were determined in the lung of mice having received poly(A:U), as compared with untreated controls. The exacerbating effect of basophils was assessed both by adoptive transfer of poly(A:U)-treated basophils and by their in vivo depletion with Ba103 antibody.

RESULTS

We found that in vitro treatment with poly(A:U) increased basophil functions by inducing TH 2-type cytokine and histamine production, whereas in vivo treatment increased peripheral basophil recruitment. Furthermore, we provide the first demonstration for increased infiltration of basophils in the lung of mice suffering from airway inflammation. In this model, disease symptoms were clearly exacerbated upon adoptive transfer of basophils exposed to poly(A:U), relative to their unstimulated counterpart. Conversely, in vivo basophil depletion alleviated disease syndromes, thus validating the transfer data.

CONCLUSIONS

Our findings provide the first evidence for airway inflammation exacerbation by basophils following dsRNA stimulation.