Experimental rhinovirus 16 infection causes variable airway obstruction in subjects with atopic asthma

Myeloid-associated differentiation marker is associated with type 2 asthma and is upregulated by human rhinovirus infection

Background

Human rhinoviruses are known to predispose infants to asthma development during childhood and are often associated with exacerbations in asthma patients. MYADM epithelial expression has been shown to associate with asthma severity. The goal of this study was to determine if MYADM expression patterns were altered in asthma and/or rhinovirus infection and if increased MYADM expression is associated with increased asthma-associated factors.

Methods

Utilizing H1HeLa cells and differentiated primary human airway epithelial cells (AECs), we measured the expression of MYADM and inflammatory genes by qRT-PCR in the presence or absence of RV-1B infection or poly I:C treatment and with siRNA knockdown of MYADM. Expression of MYADM in the asthmatic lung was determined in the ovalbumin (ova)-challenged murine model.

Results

MYADM expression was upregulated in the lungs from ova-treated mice and in particular on the subsurface vesicle membrane in airway epithelial cells. Upon infection with RV-1B, human AECs grown at an air-liquid interface had increased the MYADM expression predominantly detected in ciliated cells. We found that the presence of MYADM was required for expression of several inflammatory genes both in a resting state and after RV-1B or poly I:C treatments.

Conclusions

Our studies show that in a mouse model of asthma and during RV-1B infection of primary human AECs, increased MYADM expression is observed. In the mouse model of asthma, MYADM expression was predominantly on the luminal side of airway epithelial cells. Additionally, MYADM expression was strongly associated with increases in inflammatory genes, which may contribute to more severe asthma and RV-linked asthma exacerbations.

Quality over quantity; eosinophil activation status will deepen the insight into eosinophilic diseases

Eosinophil associated diseases have gained much attention recently because of the introduction of specific eosinophil targeted therapies. These diseases range from acute parasitic infections to chronic inflammatory diseases such as eosinophilic asthma. In eosinophilic asthma an increased eosinophil cell count in peripheral blood is the gold standard for determination of the pheno-/endotype and severity of disease. Despite a broad consensus there is concern on validity of this simple measurement, because the eosinophil compartment is far from homogenous. Multiple tissues harbour non-activated cells under homeostatic conditions and other tissues, normally devoid of eosinophils, become infested with these cells under inflammatory conditions. It will, therefore, be clear that eosinophils become differentially (pre)-activated at different tissue sites in homeostatic and inflammatory conditions. This complexity should be investigated in detail as it is 1) far from clear what the long-term side effects are that are caused by application of eosinophil targeted therapies in a "one size fits all" concept and 2) real-world data of eosinophil targeted therapies in asthma shows a broad variety in the treatment response. This review will focus on complex mechanisms of eosinophil activation in vivo to create a better view on the dynamics of the eosinophil compartment in health and disease both to prevent collateral damage caused by aberrant activation of eosinophils ánd to improve effectiveness of eosinophil targeted treatments.

Rhinovirus-Induced Cytokine Alterations With Potential Implications in Asthma Exacerbations: A Systematic Review and Meta-Analysis

Background

Rhinovirus (RV) infections are a major cause of asthma exacerbations. Unlike other respiratory viruses, RV causes minimal cytotoxic effects on airway epithelial cells and cytokines play a critical role in its pathogenesis. However, previous findings on RV-induced cytokine responses were largely inconsistent. Thus, this study sought to identify the cytokine/chemokine profiles induced by RV infection and their correlations with airway inflammatory responses and/or respiratory symptoms using systematic review, and to determine whether a quantitative difference exists in cytokine levels between asthmatic and healthy individuals via meta-analysis.

Methods

Relevant articles were obtained from PubMed, Scopus, and ScienceDirect databases. Studies that compared RV-induced cytokine responses between asthmatic and healthy individuals were included in the systematic review, and their findings were categorized based on the study designs, which were ex vivo primary bronchial epithelial cells (PBECs), ex vivo peripheral blood mononuclear cells (PBMCs), and human experimental studies. Data on cytokine levels were also extracted and analyzed using Review Manager 5.4.

Results

Thirty-four articles were included in the systematic review, with 18 of these further subjected to meta-analysis. Several studies reported the correlations between the levels of cytokines, such as IL-8, IL-4, IL-5, and IL-13, and respiratory symptoms. Evidence suggests that IL-25 and IL-33 may be the cytokines that promote type 2 inflammation in asthmatics after RV infection. Besides that, a meta-analysis revealed that PBECs from children with atopic asthma produced significantly lower levels of IFN-β [Effect size (ES): -0.84, p = 0.030] and IFN-λ (ES: -1.00, p = 0.002), and PBECs from adult atopic asthmatics produced significantly lower levels of IFN-β (ES: -0.68, p = 0.009), compared to healthy subjects after RV infection. A trend towards a deficient production of IFN-γ (ES: -0.56, p = 0.060) in PBMCs from adult atopic asthmatics was observed. In lower airways, asthmatics also had significantly lower baseline IL-15 (ES: -0.69, p = 0.020) levels.

Conclusion

Overall, RV-induced asthma exacerbations are potentially caused by an imbalance between Th1 and Th2 cytokines, which may be contributed by defective innate immune responses at cellular levels. Exogenous IFNs delivery may be beneficial as a prophylactic approach for RV-induced asthma exacerbations.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=184119, identifier CRD42020184119.

Impaired interferon-α expression in plasmacytoid dendritic cells in asthma

Background

Toll‐like receptor (TLR)‐7‐associated rhinovirus (RV) activation is involved in the pathogenesis of asthma. Plasmacytoid dendritic cells (pDCs) are the main interferon‐α‐producing cells against viruses.

Objective

To determine whether asthmatic patients and control subjects differ in terms of interferon‐α expression in pDCs under TLR‐7 or RV stimulation.

Methods

pDCs were identified in BDCA‐2+ and HLA‐DR+ peripheral blood mononuclear cells. Interferon‐α expression of pDCs was analyzed after TLR‐7 stimulation with or without interleukin 4 (IL‐4)/IL‐13 pretreatment. Interferon‐α expression was also analyzed after RV stimulation over periods of 24, 48, or 96 h with or without IL‐4 pretreatment. RV detection and molecular typing were assayed from throat swabs.

Results

Following TLR‐7 stimulation, the expression of intracellular interferon‐α was higher in the pDCs of normal subjects than those of asthmatic patients; however, pretreatment with IL‐4 was shown to reduce this effect. After 48‐ and 96‐h RV stimulation, we observed a notable increase in the production of interferon‐α of pDCs in normal subjects but not in asthmatic patients. Baseline interferon‐α expression in pDCs and the incidence of asthma exacerbation to emergency was higher among the 13% of patients identified as rhinovirus+ than among their RV counterparts.

Conclusion

Our study discovered the response to TLR‐7 stimulation in pDCs was compromised and the sustainability of interferon‐α expression to RV stimulation was reduced in pDCs of asthmatic patients, which provide further evidence of defective innate response and subspeciality to RV infection in asthma. The high exacerbation history founded in RV+ patients agrees with these findings. Further research is required for the modulatory effect of IL‐4 on TLR‐7 stimulated pDCs.

Rhinovirus C15 Induces Airway Hyperresponsiveness via Calcium Mobilization in Airway Smooth Muscle

Rhinovirus (RV) exposure evokes exacerbations of asthma that markedly impact morbidity and mortality worldwide. The mechanisms by which RV induces airway hyperresponsiveness (AHR) or by which specific RV serotypes differentially evoke AHR remain unknown. We posit that RV infection evokes AHR and inflammatory mediator release, which correlate with degrees of RV infection. Furthermore, we posit that rhinovirus C-induced AHR requires paracrine or autocrine mediator release from epithelium that modulates agonist-induced calcium mobilization in human airway smooth muscle. In these studies, we used an ex vivo model to measure bronchoconstriction and mediator release from infected airways in human precision cut lung slices to understand how RV exposure alters airway constriction. We found that rhinovirus C15 (RV-C15) infection augmented carbachol-induced airway narrowing and significantly increased release of IP-10 (IFN-γ-induced protein 10) and MIP-1β (macrophage inflammatory protein-1β) but not IL-6. RV-C15 infection of human airway epithelial cells augmented agonist-induced intracellular calcium flux and phosphorylation of myosin light chain in co-cultured human airway smooth muscle to carbachol, but not after histamine stimulation. Our data suggest that RV-C15-induced structural cell inflammatory responses are associated with viral load but that inflammatory responses and alterations in agonist-mediated constriction of human small airways are uncoupled from viral load of the tissue.

Understanding the asthmatic response to an experimental rhinovirus infection: Exploring the effects of blocking IgE

BACKGROUND

Rhinovirus frequently causes asthma exacerbations among children and young adults who are allergic. The interaction between allergen and rhinovirus-induced symptoms and inflammation over time is unclear.

OBJECTIVE

Our aim was to compare the response to an experimental inoculation with rhinovirus-16 in allergic asthmatics with the response in healthy controls and to evaluate the effects of administrating omalizumab before and during the infection.

METHODS

Two clinical trials were run in parallel. In one of these trials, the response to an experimental inoculation with rhinovirus-16 among asthmatics with high levels of total IgE was compared to the response in healthy controls. The other trial compared the effects of administering omalizumab versus placebo to asthmatics in a randomized, double-blind placebo-controlled investigation. The primary outcome for both trials compared lower respiratory tract symptoms (LRTSs) between study groups over the first 4 days of infection.

RESULTS

Frequent comparisons of symptoms, lung function, and blood eosinophil counts revealed differences that were more pronounced among allergic asthmatics than among controls by days 2 and 3 after virus inoculation. Additionally, an augmentation of upper respiratory tract symptom scores and LRTS scores occurred among the atopic asthmatics versus the controls during the resolution of symptoms (P < .01 for upper respiratory symptom tract scores and P < .001 for LRTS scores). The beneficial effects of administering omalizumab on reducing LRTSs and improving lung function were strongest over the first 4 days.

CONCLUSIONS

LRTSs and blood eosinophil counts were augmented and lung function was reduced among allergic asthmatics early after rhinovirus inoculation but increased late in the infection during symptom resolution. The effect of administering omalizumab on the response to rhinovirus was most pronounced during the early/innate phase of the infection.

Loss of adaptive capacity in asthmatic patients revealed by biomarker fluctuation dynamics after rhinovirus challenge

Asthma is a dynamic disease, in which lung mechanical and inflammatory processes interact in a complex manner, often resulting in exaggerated physiological, in particular, inflammatory responses to exogenous triggers. We hypothesize that this may be explained by respiratory disease-related systems instability and loss of adaptability to changing environmental conditions, manifested in highly fluctuating biomarkers and symptoms. Using time series of inflammatory (eosinophils, neutrophils, FeNO), clinical and lung function biomarkers (PEF, FVC,FEV₁), we estimated this loss of adaptive capacity (AC) during an experimental rhinovirus infection in 24 healthy and asthmatic human volunteers. Loss of AC was estimated by comparing similarities between pre- and post-challenge time series. Unlike healthy participants, the asthmatic’s post-viral-challenge state resembled more other rhinovirus-infected asthmatics than their own pre-viral-challenge state (hypergeometric-test: p=0.029). This reveals loss of AC and supports the concept that in asthma, biological processes underlying inflammatory and physiological responses are unstable, contributing to loss of control.

Increased type 2 inflammation post rhinovirus infection in patients with moderate asthma

Rhinovirus (RV) infections are a major cause of exacerbations in patients with asthma. Experimental RV challenges can provide insight into the pathophysiology of viral exacerbations. Previous reports, investigating mild or moderate asthma patients, have shown an upregulation in type 2 inflammation post RV infection, however, studies specifically involving asthma patients taking inhaled corticosteroids have concentrated on symptoms and lung function, rather than the inflammatory response. Eleven moderate asthma patients were inoculated with RV. Cold symptoms and asthma control were assessed at baseline and post infection. Nasal epithelial lining fluid and bronchial alveolar lavage (BAL) fluid were collected at baseline and 4 days post infection for assessment of inflammatory proteins. Patients suffered increased cold symptoms and decreased asthma control within 7 days of infection. Antiviral mechanisms were induced following inoculation, with increases in interferon -α, β, γ and λ, as well as CXCL10 and CXCL11. Type 2 inflammatory cytokines were also significantly elevated post RV infection in both nasal and bronchial samples. In BAL, epithelial derived IL-25 and IL-33 levels strongly correlated with Th2 cytokines, IL-4, IL-5 and IL-13. We show how experimental rhinovirus challenge regulates lung and nasal biomarkers in asthma patients taking inhaled corticosteroids. These biomarkers could be used to evaluate the effects of novel drugs for asthma.

Bronchial mucosal IFN-α/β and pattern recognition receptor expression in patients with experimental rhinovirus-induced asthma exacerbations

BACKGROUND

The innate immune system senses viral infection through pattern recognition receptors (PRRs), leading to type I interferon production. The role of type I interferon and PPRs in rhinovirus-induced asthma exacerbations in vivo are uncertain.

OBJECTIVES

We sought to compare bronchial mucosal type I interferon and PRR expression at baseline and after rhinovirus infection in atopic asthmatic patients and control subjects.

METHODS

Immunohistochemistry was used to detect expression of IFN-α, IFN-β, and the PRRs: Toll-like receptor 3, melanoma differentiation-associated gene 5, and retinoic acid-inducible protein I in bronchial biopsy specimens from 10 atopic asthmatic patients and 15 nonasthmatic nonatopic control subjects at baseline and on day 4 and 6 weeks after rhinovirus infection.

RESULTS

We observed IFN-α/β deficiency in the bronchial epithelium at 3 time points in asthmatic patients in vivo. Lower epithelial IFN-α/β expression was related to greater viral load, worse airway symptoms, airway hyperresponsiveness, and reductions in lung function during rhinovirus infection. We found lower frequencies of bronchial subepithelial monocytes/macrophages expressing IFN-α/β in asthmatic patients during infection. Interferon deficiency at baseline was not accompanied by deficient PRR expression in asthmatic patients. Both epithelial and subepithelial PRR expression were induced during rhinovirus infection. Rhinovirus infection-increased numbers of subepithelial interferon/PRR-expressing inflammatory cells were related to greater viral load, airway hyperresponsiveness, and reductions in lung function.

CONCLUSIONS

Bronchial epithelial IFN-α/β expression and numbers of subepithelial IFN-α/β-expressing monocytes/macrophages during infection were both deficient in asthmatic patients. Lower epithelial IFN-α/β expression was associated with adverse clinical outcomes after rhinovirus infection in vivo. Increases in numbers of subepithelial cells expressing interferon/PRRs during infection were also related to greater viral load/illness severity.

In vivo experimental models of infection and disease

Human and animal models continue to play a crucial role in research to understand host immunity to rhinovirus (RV) and identify disease mechanisms. Human models have provided direct evidence that RV infection is capable of exacerbating chronic respiratory diseases and identified immunological processes that correlate with clinical disease outcomes. Mice are the most commonly used nonhuman experimental RV infection model. Although semipermissive, under defined experimental conditions sufficient replication occurs to induce host immune responses that recapitulate immunity and disease during human infection. The capacity to use genetically modified mouse strains and drug interventions has shown the mouse model to be an invaluable research tool defining causal relationships between host immunity and disease and supporting development of new treatments. Used in combination the insights achieved from human and animal experimental infection models provide complementary insights into RV biology and yield novel therapeutic options to reduce the burden of RV-induced disease.

Study of Clinical Characteristics and Cytokine Profiles of Asthmatic Children with Rhinovirus Infection during Acute Asthma Exacerbation at National Hospital of Pediatrics

Background

In children with asthma, the viral infection of airways is usually a main cause of acute asthma exacerbation and hospitalization. However, few studies on clinical and biomolecular characteristics of asthmatic children in this field have been done, especially in emergent countries.

Objective

This study described the clinical and biological characteristics of asthmatic children who had acute asthma exacerbation and rhinovirus (RV) infection.

Methods

Children under 15 years of age hospitalized for acute asthma exacerbation were included. They underwent clinical examination and peripheral blood analyses for the cytokine profile. The severity of acute asthma exacerbation was evaluated by Pediatric Asthma Score (PAS). Healthy children under 15 years of age were also invited in this study.

Results

One hundred fifteen asthmatic children were included in this study. There were 18.2% of mild PAS, 37.4% of moderate PAS, and 44.4% of severe PSA. Among them, 63/115 (54.8%) asthmatic children had positive RV infection (RV⁺). The percentages of asthmatic children with RV⁺ had increased polymorphonuclear leucocytes were significantly higher than asthmatic children with RV⁻. There were no significant differences of the concentrations of non-Th2-related cytokines in asthmatic children with RV⁻ and RV⁺. The concentration of Th2-related cytokines (IL-5 and IL-13) in asthmatic children with RV⁺ was significantly higher than those with RV⁻. However, there was no significant difference for the cytokine profile between mild, moderate, and severe asthma.

Conclusion

RV infection is a main cause of acute asthma exacerbation in children with asthma. The increase of Th2-related cytokines, especially IL-5 and IL-13, is a relevant biomarker for RV infection in asthmatic children with severe exacerbation.

Does atopy affect the course of viral pneumonia?

Background

The presence of atopy is considered as a risk factor for severe respiratory symptoms in children. The objective of this study was to examine the effect of atopy on the course of disease in children hospitalised with viral pneumonia.

Methods

Children between the ages of 1 and 6 years hospitalised due to viral pneumonia between the years of 2013 and 2016 were included to this multicentre study. Patients were classified into two groups as mild–moderate and severe according to the course of pneumonia. Presence of atopy was evaluated with skin prick tests. Groups were compared to evaluate the risk factors associated with severe viral pneumonia.

Results

A total of 280 patients from nine centres were included in the study. Of these patients, 163 (58.2%) were male. Respiratory syncytial virus (29.7%), Influenza A (20.5%), rhinovirus (18.9%), adenovirus (10%), human metapneumovirus (8%), parainfluenza (5.2%), coronavirus (6%), and bocavirus (1.6%) were isolated from respiratory samples. Eighty-five (30.4%) children had severe pneumonia. Atopic sensitisation was found in 21.4% of the patients. Ever wheezing (RR: 1.6, 95% CI: 1.1–2.4), parental asthma (RR: 1.5, 95% CI: 1.1–2.2), other allergic diseases in the family (RR: 1.8, 95% CI: 1.2–2.9) and environmental tobacco smoke (RR: 1.6, 95% CI: 1.1–3.5) were more common in the severe pneumonia group.

Conclusions

When patients with mild–moderate pneumonia were compared to patients with severe pneumonia, frequency of atopy was not different between the two groups. However, parental asthma, ever wheezing and environmental tobacco smoke exposure are risk factors for severe viral pneumonia in children.

Prevalence of Respiratory Viral Infections in Korean Adult Asthmatics With Acute Exacerbations: Comparison With Those With Stable State

PURPOSE

Viral infections are involved in ~50% of exacerbations among Caucasian adult asthmatics. However, there have been few reports on the causative virus of exacerbations in Korean adult asthmatics. Thus, we compared frequencies and types of viruses between lower respiratory tract illnesses (LRTIs) with exacerbations (exacerbated LRTIs) and those without exacerbations (stable LRTIs) to evaluate contribution of respiratory viruses to exacerbations.

METHODS

Viral RNA was extracted from sputum using the Viral Gene-spin™ Kit. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to detect adenovirus (ADV), metapneumovirus (MPV), parainfluenza virus (PIV) 1/2/3, influenza virus (IFV) A, IFV B, respiratory syncytial virus (RSV) A/B, and rhinovirus (RV) A.

RESULTS

Among the 259 patients, 210 underwent a single sputum examination, and the remaining 49 underwent 2 to 4 sputum examinations. Virus was detected in 68 of the 259 exacerbated episodes and in 11 of the 64 stable episodes. Among the exacerbated episodes, RV was the most frequently detected virus, followed by influenza A, parainfluenza, RSV A/B, and ADV. Among the 11 stable episodes, RV was most frequently detected. Detection rates of these viruses did not differ between the 2 groups (P>0.05). Thirty-five patients underwent the virus examination at 2 episodes of exacerbation, while 14 patients underwent at each time of exacerbated and stable episodes. Virus detection rate at the second examination was significantly higher in cases with 2 exacerbation episodes than in those with initial exacerbation and sequential stable episodes (P=0.003). A seasonal pattern was noted in the detection rates of RV (September to December), IFV (January to April), PIV (May to September), and RSV A/B (September to April).

CONCLUSIONS

Respiratory viruses were identified in approximately 20% of LRTI irrespective of the presence of asthma exacerbation. RV and IFV A/B were most frequently detected. A group of patients experienced frequent viral infections followed by asthma exacerbations.

Update on Human Rhinovirus and Coronavirus Infections

Human rhinovirus (HRV) and coronavirus (HCoV) infections are associated with both upper respiratory tract illness (“the common cold”) and lower respiratory tract illness (pneumonia). New species of HRVs and HCoVs have been diagnosed in the past decade. More sensitive diagnostic tests such as reverse transcription-polymerase chain reaction have expanded our understanding of the role these viruses play in both immunocompetent and immunosuppressed hosts. Recent identification of severe acute respiratory syndrome and Middle East respiratory syndrome viruses causing serious respiratory illnesses has led to renewed efforts for vaccine development. The role these viruses play in patients with chronic lung disease such as asthma makes the search for antiviral agents of increased importance.

Utility of animal and in vivo experimental infection of humans with rhinoviruses in the development of therapeutic agents for viral exacerbations of asthma and chronic obstructive pulmonary disease

There is an association with acute viral infection of the respiratory tract and exacerbations of asthma and chronic obstructive pulmonary disease (COPD). Although these exacerbations are associated with several types of viruses, human rhinoviruses (HRVs) are associated with the vast majority of disease exacerbations. Due to the lack of an animal species that is naturally permissive for HRVs to use as a facile model system, and the limitations associated with animal models of asthma and COPD, studies of controlled experimental infection of humans with HRVs have been used and conducted safely for decades. This review discusses how these experimental infection studies with HRVs have provided a means of understanding the pathophysiology underlying virus-induced exacerbations of asthma and COPD with the goal of developing agents for their prevention and treatment.

Airway inflammation and illness severity in response to experimental rhinovirus infection in asthma

Background:

The nature of bronchial mucosal inflammation and its physiologic and clinical significance in rhinovirus-induced asthma exacerbations is unclear. We investigated bronchial mucosal inflammatory response and its association with physiologic and clinical outcomes in an experimental model of rhinovirus-induced asthma exacerbations.

Methods:

We used immunohistochemistry methods to detect phenotypes of inflammatory cells infiltrating the bronchial mucosa before and after experimental rhinovirus infection in 10 subjects with asthma and 15 normal subjects.

Results:

Compared with baseline, rhinovirus infection significantly increased the number of epithelial (P = .005) and subepithelial (P = .017) neutrophils in subjects with asthma only and subepithelial CD68⁺ macrophages in both subjects with asthma (P = .009) and normal subjects (P = .018) but more so in those with asthma (P = .021). Numbers of CD45⁺, CD68⁺, and CD20⁺ cells; neutrophils; and eosinophils at day 4 postinfection were positively associated with virus load (r = 0.50-0.72, P = .016-0.03). At acute infection in subjects with asthma, CD4⁺ cells correlated with chest symptom scores (r = 0.69, P = .029), the fall in the 10% fall in FEV₁ (PC₁₀) correlated with neutrophils (r = −0.89, P = .029), the PC₁₀ correlated inversely with CD4⁺ (r = −0.67, P = .023) and CD8⁺ cells (r = −0.65, P = .03), the 20% fall in FEV₁ was inversely associated with CD20⁺ cells (r = −0.65, P = .03), and higher epithelial CD8⁺ cell counts were significantly associated with a greater maximum fall in FEV₁ (r = −0.72, P = .03), whereas higher subepithelial mast cell counts were significantly associated with a lower maximum percent fall in peak expiratory flow (r = 0.8, P = .024).

Conclusions:

In subjects with asthma, rhinovirus infection induces bronchial mucosal neutrophilia and more severe monocyte/macrophage infiltration than in normal subjects. Airway neutrophils, eosinophils, and T and B lymphocytes during infection are related to virus load and physiologic and clinical severity, whereas mast cells are related to greater lung function.

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.

Sinusitis, Rhinitis, Asthma, and the Single Airway Hypothesis

The one airway, one disease hypothesis proposes that the upper and lower airways share the same physiology and histomorphology. Epidemiological clinical studies support a link between rhinosinusitis and asthma. The relationship can occur in both directions, with nasal allergen challenge leading to inflammatory changes in the lower airway and bronchoprovocation studies of the lower airway leading to inflammatory changes in the upper airway. In addition, both similarities and differences exist in the pathogenesis of nasal polyps and asthma. The mechanism for the connection between the upper and lower airways is a matter of great debate. It has been proposed that inflammatory changes in the lower airway may lead to systemic inflammatory effects that play a role in increased bronchial hyperresponsiveness. Similarly, lower airway inflammatory changes may affect nasal airway patency via systemic effects. Moreover, nasopharyngeal-bronchial reflexes may play a non-immunologic role in the interaction between the lower and upper airways. An example of the connection between the upper and lower airways is found in aspirin-exacerbated respiratory disease whereby leukotrienes play a role in the pathology of chronic rhinosinusitis with polyps and asthma. It is also been observed that the treatment of asthma is hindered by untreated rhinosinusitis.

Vitamin C and common cold-induced asthma: a systematic review and statistical analysis

BACKGROUND

Asthma exacerbations are often induced by the common cold, which, in turn, can be alleviated by vitamin C.

OBJECTIVE

To investigate whether vitamin C administration influences common cold-induced asthma.

METHODS

Systematic review and statistical analysis of the identified trials. Medline, Scopus and Cochrane Central were searched for studies that give information on the effects of vitamin C on common cold-induced asthma. All clinically relevant outcomes related to asthma were included in this review. The estimates of vitamin C effect and their confidence intervals [CI] were calculated for the included studies.

RESULTS

Three studies that were relevant for examining the role of vitamin C on common cold-induced asthma were identified. The three studies had a total of 79 participants. Two studies were randomized double-blind placebo-controlled trials. A study in Nigeria on asthmatics whose asthma attacks were precipitated by respiratory infections found that 1 g/day vitamin C decreased the occurrence of asthma attacks by 78% (95% CI: 19% to 94%). A cross-over study in former East-Germany on patients who had infection-related asthma found that 5 g/day vitamin C decreased the proportion of participants who had bronchial hypersensitivity to histamine by 52 percentage points (95% CI: 25 to 71). The third study did not use a placebo. Administration of a single dose of 1 gram of vitamin C to Italian non-asthmatic common cold patients increased the provocative concentration of histamine (PC20) 3.2-fold (95% CI: 2.0 to 5.1), but the vitamin C effect was significantly less when the same participants did not suffer from the common cold.

CONCLUSIONS

The three reviewed studies differed substantially in their methods, settings and outcomes. Each of them found benefits from the administration of vitamin C; either against asthma attacks or against bronchial hypersensitivity, the latter of which is a characteristic of asthma. Given the evidence suggesting that vitamin C alleviates common cold symptoms and the findings of this systematic review, it may be reasonable for asthmatic patients to test vitamin C on an individual basis, if they have exacerbations of asthma caused by respiratory infections. More research on the role of vitamin C on common cold-induced asthma is needed.

γδT cells suppress inflammation and disease during rhinovirus-induced asthma exacerbations

Most asthma exacerbations are triggered by virus infections, the majority being caused by human rhinoviruses (RV). In mouse models, γδT cells have been previously demonstrated to influence allergen-driven airways hyper-reactivity (AHR) and can have antiviral activity, implicating them as prime candidates in the pathogenesis of asthma exacerbations. To explore this, we have used human and mouse models of experimental RV-induced asthma exacerbations to examine γδT-cell responses and determine their role in the immune response and associated airways disease. In humans, airway γδT-cell numbers were increased in asthmatic vs. healthy control subjects during experimental infection. Airway and blood γδT-cell numbers were associated with increased airways obstruction and AHR. Airway γδT-cell number was also positively correlated with bronchoalveolar lavage (BAL) virus load and BAL eosinophils and lymphocytes during RV infection. Consistent with our observations of RV-induced asthma exacerbations in humans, infection of mice with allergic airways inflammation increased lung γδT-cell number and activation. Inhibiting γδT-cell responses using anti-γδTCR (anti-γδT-cell receptor) antibody treatment in the mouse asthma exacerbation model increased AHR and airway T helper type 2 cell recruitment and eosinophilia, providing evidence that γδT cells are negative regulators of airways inflammation and disease in RV-induced asthma exacerbations.

Human challenge studies: a review of adequacy of reporting methods and results

Since the 1940s, researchers have purposefully infected healthy adult humans with pathogenic organisms to study how these pathogens cause disease and can be treated and prevented. 'Challenge studies' can be safe, ethical, extremely informative and an efficient use of resources during the clinical development of vaccines, but knowledge of this form of clinical research trial is not widespread. A review of the human challenge literature was performed to determine whether common elements of challenge studies can be identified in the articles published to date. The review demonstrated incomplete reporting of study characteristics deemed necessary for the correct interpretation and application of human challenge study results and for the accurate replication of study methodology. An unofficial extension of the Consolidated Standards of Reporting Trials (CONSORT) statement is proposed.

The Clinical Definitions of Asthma

It is believed that the term “asthma” was coined by Hippocrates around 450 bc. The term literally means “panting,” from the Greek. Descriptions of the clinical presentation of those affected with asthma appear in medical literature throughout history.

Enterovirus 68 among children with severe acute respiratory infection, the Philippines

Enterovirus 68 (EV68) is a rare enterovirus associated with respiratory illness that, unlike other enteroviruses, has been identified only from respiratory specimens. We identified EV68 from respiratory specimens of children hospitalized with a diagnosis of severe pneumonia in Leyte, Republic of the Philippines. Twenty-one samples showed high similarity with EV68 by sequencing of 5' nontranslated region; 17 of these samples were confirmed as EV68 by sequencing of viral protein 1 capsid coding region. Most previously reported EV68 cases had been identified as sporadic cases. All 21 patients we identified had severe illness, and 2 died, possibly the first reported fatal cases associated with EV68 infection. Our study suggests that EV68 may be a possible causative agent of severe respiratory illnesses.

Risk factors for asthma onset between the ages of 12 and 40. Results of the FENASMA study

OBJECTIVES

To describe the clinical profile of patients with asthma and to identify possible risk factors for its development in subjects over the age of 12.

PATIENTS AND METHODS

A multicenter study of cases and controls. Recruited for inclusion were case subjects between the ages of 12 and 40 diagnosed with asthma, with an onset of symptoms after the age of 12. Control subjects were selected, with ages between 12 and 40, who did not have childhood asthma and did not present symptoms of asthma at the time of the study.

RESULTS

We evaluated 923 subjects: 247 cases and 671 controls. 54.9% were women. Mean age of the cases was 28.3 ± 8.2; mean age of controls was 30.8 ± 7.1 (p<0.001). In the logistic regression analysis, it was observed that the determining factors for the of the presence of asthma were hypersensitivity to animals or other allergens, presence of rhinitis, family history of asthma, occupational risk/exposure to irritants and the hypersensitivity/intolerance to NSAIDs. In said analysis, it was also demonstrated that age was a protection factor, as well as level of education.

CONCLUSIONS

The risk factors for the development of asthma at an adult age are hypersensitivity to animals or other allergens, rhinitis, family history of asthma, occupational risk/exposure to irritants and the hypersensitivity/intolerance to NSAIDs, while age and level of education are protection factors.

Global airway disease beyond allergy

Besides the anatomic continuity of the upper and lower airways, inflammation in one part of the airway influences the homeostasis of the other. The mechanisms underlying this interaction have been studied primarily in allergic disease, showing systemic immune activation, induction of inflammation at a distance, and a negative impact of nasal inflammation on bronchial homeostasis. In addition to allergy, other inflammatory conditions of the upper airways are associated with lower airway disease. Rhinosinusitis is frequently associated with asthma and chronic obstructive pulmonary disease. The impairment of purification, humidification, and warming up of the inspired air by the nose in rhinosinusitis may be responsible in part for bronchial pathology. The resolution of sinonasal inflammation via medical and/or surgical treatment is responsible for the beneficial effect of the treatment on bronchial disease. This article provides a comprehensive overview of the current knowledge of upper and lower airway communication beyond allergic disease.

Rhinosinusitis and the lower airways

The interaction between upper and lower airway disease has been recognized for centuries, with recent studies showing a direct link between upper and airway inflammation in allergic patients. The mechanisms underlying the interaction between nasal and bronchial inflammation have primarily been studied in allergic disease, showing systemic immune activation after allergen inhalation, induction of inflammation at a distance, and a negative impact of nasal inflammation on bronchial homeostasis. Therefore, allergic rhinitis and asthma are considered part of the global airway allergy syndrome. Besides allergy, other inflammatory conditions such as the common cold, acute rhinosinusitis, and chronic rhinosinusitis are associated with lower airway disease. Chronic sinus disease with or without nasal polyps are frequently found in patients with asthma and chronic obstructive pulmonary disease with improvement of bronchial symptoms and respiratory function by adequate medical and surgical therapy for rhinosinusitis. The resolution of sinonasal inflammation and hence sinonasal functions by medical or surgical treatment is considered responsible for the beneficial effect of treatment on bronchial disease. This article aims at providing a comprehensive overview of the current knowledge on the interaction between common cold, acute and chronic rhinosinusitis, and lower airway biology.

Common cold decreases lung function in infants with recurrent wheezing

Background

Common acute viral respiratory infections (colds) are the most frequent cause of exacerbations in infants with recurrent wheezing (RW). However, there is no quantitative information about the effect of colds on the lung function of infants with RW. This study was undertaken to determine the effect of common cold on forced expiratory parameters measured from raised lung volume in infants with RW.

Methods

Spirometric lung function (expiratory flows from raised lung volume) was randomly assessed in 28 infants with RW while they had a common cold and when asymptomatic.

Results

It was found that during colds there was a significant decrease in all forced expiratory parameters and this was much more evident for flows (FEF_50%, FEF_75% and FEF_25–75%) which were definitively abnormal (less than −1.65 z-score) in the majority of infants. There was not association between family asthma, tobacco exposure, and other factors, with the extent of lung function decrease during colds. Tobacco during pregnancy but not a history of family asthma was significantly associated to lower expiratory flows; however, the association was significant only when infants were asymptomatic.

Conclusion

This study shows that common colds cause a marked reduction of lung function in infants with RW.

Bugs and asthma: a different disease?

The prevalence of asthma has dramatically increased in recent decades. Exacerbations of asthma are a large contributor to asthma-related costs, and are primarily caused by viral and atypical bacterial infections. Rhinoviruses (RVs) are the most common viruses detected after an asthma exacerbation. RVs, respiratory syncytial virus (RSV), and human metapneumovirus (hMPV) viral infections early in life can induce wheezing and are associated with the development of asthma later in life. Atypical bacterial infections from Mycoplasma pneumoniae and Chlamydia pneumoniae have also been linked to chronic asthma and potential asthma exacerbations. In this article, we will discuss recent developments in viral infections, specifically RV, RSV, and hMPV, and atypical bacterial infections as causes of asthma exacerbations, including new data focusing on the host immune response in airway epithelial cells and animal models of infection.

Managing childhood asthma: challenge of preventing exacerbations

Acute episodes of airway obstruction followed by periods of apparent wellness are the main clinical manifestations of the disease for many children with persistent asthma. Although currently available asthma controllers decrease the risk for acute asthma exacerbations, 30% of children taking these medicines still have >or=1 episode requiring oral corticosteroid treatment per year. There is increasing evidence that neutrophilic inflammation, against which inhaled corticosteroids are not very effective, plays a major role in the pathogenesis of asthma exacerbations. New therapeutic approaches are needed for this frequent cause of consultation in pediatric practice. One approach could be the development of drugs that target neutrophilic inflammation specifically. Studies in adults have shown that use of inhaled corticosteroids every time a bronchodilator is needed may decrease the frequency of asthma exacerbations. This strategy is currently being tested in a large clinical trial involving children with mild persistent asthma.

Diversity in the bronchial epithelial cell response to infection with different rhinovirus strains

BACKGROUND AND OBJECTIVE

Infection with rhinovirus (RV) is the most common trigger for acute asthma and COPD. The aim of this study was to characterize the variability in the response of primary bronchial epithelial cells to infection with several strains of RV.

METHODS

RV strains, RV-43, RV-48 (major group RV), RV-47 (minor) and EV-68 (enterovirus), were cultured from subjects with acute asthma and compared with the laboratory RV strains, RV-16, RV-14 (major) and RV-1B (minor). Primary bronchial epithelial cells were obtained from healthy control and asthmatic subjects by endobronchial brushing. Response to infection was assessed by the release of IL-6, interferon (IFN)-gamma induced protein (IP)-10 and IFN-beta, as measured by ELISA. Viral replication was assessed by serial titration assays and cell viability by flow cytometry.

RESULTS

Major group RV strains and EV-68 all efficiently infected and replicated in epithelial cells causing little cell death. The clinical major group RV strains caused greater release of IL-6 and IP-10 compared with laboratory major group RV strains. Infection with minor group RV resulted in greater release of IP-10, IL-6 and IFN-beta that was associated with induction of apoptosis and less efficient viral replication. Asthmatic bronchial epithelial cells were less able to respond by releasing IFN-beta following infection with RV-1B.

CONCLUSIONS

Considerable diversity exists in the response to RV strains, especially between minor and major group RV. The impaired IFN-beta response in asthmatic bronchial epithelial cells may make them particularly susceptible to minor group RV.

[Infections and asthma]

Asthma is a chronic inflammatory disorder of the airways. Allergen-induced airway inflammation plays a central role in the pathogenesis of the disease whereas infections are known to be important triggers of acute exacerbations. Chronic or latent infections may also influence and enhance the local inflammation. The aim of this review is to give an overview of the different pathogens and to present the current understanding of the role of respiratory viruses and atypical bacteria in the pathogenesis of the disease.

Infections

This chapter reviews the epidemiological evidence implicating infectious pathogens as triggers and will discuss the mechanisms of interaction between the host–pathogen response and preexisting airway pathology that result in an exacerbation. Asthma is a multifaceted syndrome involving atopy, bronchial hyperreactivity, and IgE and non-IgE-mediated acute and chronic immune responses. The asthmatic airway is characterized by an infiltrate of eosinophils and of T-lymphocytes expressing the type 2 cytokines IL-4, IL-5, and IL-13. Trigger factors associated with acute exacerbations of asthma include exposure to environmental allergens, especially animals, molds, pollens and mites, cold, exercise, and drugs. The frequency of exacerbations is a major factor in the quality of life of patients with COPD. The typical clinical features of an exacerbation include increased dyspnea, wheezing, cough, sputum production, and worsened gas exchange. Although noninfectious causes of exacerbations such as allergy, air pollution, or inhaled irritants including cigarette smoke may be important, acute airway infections are the major precipitants. The infection and consequent host inflammatory response result in increased airway obstruction. The success of vaccination to prevent respiratory virus infections has been limited by significant variation within the major virus types causing disease. Currently much of the treatment of infective exacerbations of asthma and COPD is symptomatic, consisting of increased bronchodilators, either short-acting β 2—agonists in inhaled or intravenous form or anticholinergics or theophyllines, or supportive in the form of oxygen and in severe cases noninvasive or invasive ventilatory measures.

Innate immune response to viral infection of the lungs

Viral respiratory tract infections are the most common infectious illnesses, though they are usually self-limiting and confined to the respiratory tract. The rapid identification of viruses and their effective elimination with minimal local and systemic inflammation is a testament to the efficiency of the innate immune response within the airways and lungs. A failure of this response appears to occur in those with asthma and chronic obstructive pulmonary disease, where viral infection is an important trigger for acute exacerbations. The innate immune response to viruses requires their early detection through pathogen recognition receptors and the recruitment of the efficient antiviral response that is centred around the release of type 1 interferons. The airway epithelium provides both a barrier and an early detector for viruses, and interacts closely with cells of the innate immune response, especially macrophages and dendritic cells, to eliminate infection and trigger a specific adaptive immune response.

Lycopene enrichment of cultured airway epithelial cells decreases the inflammation induced by rhinovirus infection and lipopolysaccharide

Rhinovirus infection results in increased release of inflammatory mediators from airway epithelial cells in asthma. As an antioxidant, lycopene offers protection from adverse effects of inflammation. The aim of this study was to find an appropriate method of lycopene enrichment of airway epithelial cells and to determine the effects of lycopene enrichment on the inflammatory response of cells infected by rhinovirus or exposed to lipopolysaccharide. Lycopene enrichment of airway epithelial cells using solubilisation in tetrahydrofuran versus incorporation in liposomes was compared. After determining that solubilisation of lycopene in tetrahydrofuran was the most suitable method of lycopene supplementation, airway epithelial cells (Calu-3) were incubated with lycopene (dissolved in tetrahydrofuran) for 24 h, followed by rhinovirus infection or lipopolysaccharide exposure for 48 h. The release of interleukin-6, interleukin-8 and interferon-gamma induced protein-10 (IP-10) and their messenger RNA levels were measured using enzyme linked immunosorbent assay and reverse transcription polymerase chain reaction, respectively. Viral replication was measured by tissue culture infective dose of 50% assay. Lycopene concentration of cells and media were analysed using high-performance liquid chromatography. Preincubation of airway epithelial cells with lycopene (dissolved in tetrahydrofuran) delivered lycopene into the cells and resulted in a 24% reduction in interleukin-6 after rhinovirus-1B infection, 31% reduction in IP-10 after rhinovirus-43 infection and 85% reduction in rhinovirus-1B replication. Lycopene also decreased the release of IL-6 and IP-10 following exposure to lipopolysaccharide. We conclude that lycopene has a potential role in suppressing rhinovirus induced airway inflammation.

Rhinovirus-induced lower respiratory illness is increased in asthma and related to virus load and Th1/2 cytokine and IL-10 production

Acute exacerbations are the major cause of asthma morbidity, mortality, and health-care costs and are difficult to treat and prevent. The majority of asthma exacerbations are associated with rhinovirus (RV) infection, but evidence supporting a causal relationship is weak and mechanisms are poorly understood. We hypothesized that in asthmatic, but not normal, subjects RV infection would induce clinical, physiologic, and pathologic lower airway responses typical of an asthma exacerbation and that these changes would be related to virus replication and impaired T helper 1 (Th1)/IL-10 or augmented Th2 immune responses. We investigated physiologic, virologic, and immunopathologic responses to experimental RV infection in blood, induced sputum, and bronchial lavage in 10 asthmatic and 15 normal volunteers. RV infection induced significantly greater lower respiratory symptoms and lung function impairment and increases in bronchial hyperreactivity and eosinophilic lower airway inflammation in asthmatic compared with normal subjects. In asthmatic, but not normal, subjects virus load was significantly related to lower respiratory symptoms, bronchial hyperreactivity, and reductions in blood total and CD8(+) lymphocytes; lung function impairment was significantly related to neutrophilic and eosinophilic lower airway inflammation. The same virologic and clinical outcomes were strongly related to deficient IFN-gamma and IL-10 responses and to augmented IL-4, IL-5, and IL-13 responses. This study demonstrates increased RV-induced clinical illness severity in asthmatic compared with normal subjects, provides evidence of strong relationships between virus load, lower airway virus-induced inflammation and asthma exacerbation severity, and indicates augmented Th2 or impaired Th1 or IL-10 immunity are likely important mechanisms.

The role of infection in asthma

This paper reviews the impact of infections on the onset and clinical course of bronchial asthma. A just emphasis is given to the role viral infections, particularly rhinovirus infections, play in exacerbations, and that played by respiratory syncytial virus, suspected of triggering the asthmatic syndrome. The mechanisms of the immune response to virus attacks are explained, highlighting the asthmatic and allergic patient's weakened response, particularly in the perinatal period. Further stressed is a potentiating effect of viral aggression on the allergic response. The hygiene hypothesis and its lack of scientific consistency is detailed, at least as far as the role it seeks to confer on an unproven antagonism of the Th1 and Th2 lymphocyte responses. The current importance of research not into bacteria, but into bacterial products, including endotoxins, on the modulation of asthma and allergy is noted. Studies which, along these lines, show an environmental impact on genetic secretion in the phenotype are underlined. Also discussed in passing are several mechanisms which go towards explaining neutrophilic asthma - for many a contradiction, given eosinophilia's stranglehold on asthmatic inflammation.

Infecção na modulaçâo da asma11Trabalho apresentado no XXIII Congresso de Pneumologia da SPP – Guarda, Novembro 2007 / Paper presented at the XXIII Congresso de Pneumologia da SPP / PSP Pulmonology Congress, Guarda, November 2007

Faz-se uma revisão da influência das infecções no aparecimento e na clínica da asma brônquica. Dá-se o relevo que merece à intervenção virusal, sobretudo ao rinovírus, pela sua influência nas exacerbações, e ao vírus sincicial respiratório, sobre o qual recai a suspeita de poder ser causa determinante no aparecimento da síndroma asmática. Tentam-se esclarecer os mecanismos da resposta imune à agressão virusal em função das debilidades da resposta do asmático e do atópico, sobretudo no período perinatal, salientando-se, ainda, um efeito de potenciação da agressão virusal sobre a resposta atópica. Aborda-se a hipótese higiénica e a sua falta de consistência científica, pelo menos no papel que pretende atribuir a um não demonstrado antagonismo das respostas linfocitárias Th₁ e Th_2, apontando-se a importância actual da investigação, não das bactérias mas dos produtos bacterianos, como as endotoxinas, na modulação da asma e da atopia, dando-se relevo aos estudos que, a partir deste modelo, demonstram uma influência do ambiente na secreção génica e, consequentemente, no fenótipo. Invocam-se, nas entrelinhas, vários mecanismos que podem explicar a asma neutrofílica que, para muitos, é um paradoxo perante o consagrado domínio do eosinófilo na inflamação asmática.

Rev Port Pneumol 2008; XIV (5): 647-675

Wheezing due to rhinovirus infection in infancy: Bronchial hyperresponsiveness at school age

BACKGROUND

Characteristics related to decreased lung function and increased bronchial responsiveness after early childhood wheezing requiring hospitalization are not fully established.

METHODS

Seventy-nine children with wheezing requiring hospitalization at age <2 years were prospectively followed up and re-investigated at age 5.6-8.8 years when the measurements of baseline lung function and bronchial responsiveness to exercise were performed.

RESULTS

At early school age, 23% of children had decreased lung function, and 13% had increased bronchial responsiveness to exercise. Predictors of decreased lung function were maternal history of smoking during pregnancy (odds ratio [OR], 12.8; 95% confidence interval [CI]: 1.2-139.6), parental history of asthma (OR, 4.3; 95%CI: 1.1-17.1), and female gender (OR, 4.0; 95%CI: 1.2-13.7). Increased bronchial responsiveness was associated with rhinovirus infection-induced wheezing in infancy (OR, 6.5; 95%CI: 1.2-36.3), and early cat or dog exposure leading to sensitization (OR, 26.6; 95%CI: 1.3-525.2). Inhaled anti-inflammatory therapy was common in children with rhinovirus infection-induced wheezing in infancy (n = 13/19; P = 0.001 vs children with other/no confirmed virus infection etiology for wheezing in infancy, n = 16/60), which may have improved lung function and attenuated bronchial responsiveness in them.

CONCLUSIONS

After early childhood wheezing requiring hospitalization, one-fourth of children will have decreased lung function and one-eighth of children will show increased bronchial responsiveness at school age. Gender, heredity of asthma, and antenatal exposure to tobacco smoke are predictors of decreased lung function, whereas rhinovirus infection etiology of wheeze and early animal exposure leading to sensitization are associated with increased bronchial responsiveness later in childhood.

Anti-inflammatory effects of long-chain n-3 PUFA in rhinovirus-infected cultured airway epithelial cells

Long-chain n-3 PUFA (LCn-3PUFA) including DHA and EPA, are known to decrease inflammation by inhibiting arachidonic acid (AA) metabolism to eicosanoids, decreasing the production of pro-inflammatory cytokines and reducing immune cell function. The aim of this study was to determine if EPA and DHA reduced the release of inflammatory mediators from airway epithelial cells infected with rhinovirus (RV). Airway epithelial cells (Calu-3) were incubated with EPA, DHA and AA for 24 h, followed by rhinovirus infection for 48 h. IL-6, IL-8 and interferon-γ-induced protein-10 (IP-10) released by cells were measured using ELISA. Viral replication was measured by serial titration assays. The fatty acid content of cells was analysed using GC. Cellular viability was determined by visual inspection of cells and lactate dehydrogenase release. DHA (400 μm) resulted in a significant 16 % reduction in IL-6 release after RV-43 infection, 29 % reduction in IL-6 release after RV-1B infection, 28 % reduction in IP-10 release after RV-43 infection and 23 % reduction in IP-10 release after RV-1B infection. Cellular DHA content negatively correlated with IL-6 and IP-10 release. None of the fatty acids significantly modified rhinovirus replication. DHA supplementation resulted in increased cellular content of DHA at the cost of AA, which may explain the decreased inflammatory response of cells. EPA and AA did not change the release of inflammatory biomarkers significantly. It is concluded that DHA has a potential role in suppressing RV-induced airway inflammation.

Epidermal growth factor receptor signaling to Erk1/2 and STATs control the intensity of the epithelial inflammatory responses to rhinovirus infection

Rhinovirus infection is the most common cause of acute exacerbations of inflammatory lung diseases, such as asthma and chronic obstructive pulmonary disease, where it provokes steroid refractory and abnormally intense neutrophilic inflammation that can be life threatening. Epidermal growth factor receptor (EGFR) expression correlates with disease severity and neutrophil infiltration in these conditions. However, the role of EGFR signaling in rhinovirus infection is unknown. We measured the key determinants of neutrophilic inflammation interleukin (IL)-8 and ICAM-1 in rhinovirus (RV16 serotype)-infected bronchial epithelial cells, BEAS-2B. RV16 infection stimulated IL-8 and ICAM-1 expression, which was further elevated (2-fold) by transient up-regulation of EGFR levels. Detection of viral RNA by quantitative real time PCR confirmed that enhanced expression was not associated with increased viral replication. EGFR ligands (epiregulin, amphiregulin, and heparin-binding epidermal growth factor) were induced by RV16 infection, and inhibition of metalloproteases responsible for ligand shedding partially suppressed this response. The EGFR inhibitor AG1478, completely blocked IL-8 and ICAM-1 expression to basal levels, as did the specific Erk1/2 inhibitor U0126. The p38 mitogen-activated protein kinase inhibitor SB203580 blocked IL-8 secretion but not ICAM-1 expression, whereas the PI3K inhibitor wortmannin was ineffective in both responses. Kinase inactive K721R EGFR, which is selectively deficient in STAT signaling, reversed RV16 responses associated with EGFR overexpression. In conclusion, RV16 infection rapidly promotes induction of EGFR ligands and utilizes EGFR signaling to increase IL-8 and ICAM-1 levels. These results suggest that targeting EGFR may provide a selective therapy that dampens neutrophil-driven inflammation without compromising essential antiviral pathways mediated by pathogen recognition receptors such as TLR3.

Pan-viral screening of respiratory tract infections in adults with and without asthma reveals unexpected human coronavirus and human rhinovirus diversity

Background. Between 50% and 80% of asthma exacerbations are associated with viral respiratory tract infections (RTIs), yet the influence of viral pathogen diversity on asthma outcomes is poorly understood because of the limited scope and throughput of conventional viral detection methods.

Methods. We investigated the capability of the Virochip, a DNA microarray—based viral detection platform, to characterize viral diversity in RTIs in adults with and without asthma.

Results. The Virochip detected viruses in a higher proportion of samples (65%) than did culture isolation (17%) while exhibiting high concordance (98%) with and comparable sensitivity (97%) and specificity (98%) to pathogen-specific polymerase chain reaction. A similar spectrum of viruses was identified in the RTIs of each patient subgroup; however, unexpected diversity among human coronaviruses (HCoVs) and human rhinoviruses (HRVs) was revealed. All but one of the HCoVs corresponded to the newly recognized HCoV-NL63 and HCoV-HKU1 viruses, and >20 different serotypes of HRVs were detected, including a set of 5 divergent isolates that formed a distinct genetic subgroup.

Conclusions. The Virochip can detect both known and novel variants of viral pathogens present in RTIs. Given the diversity detected here, larger-scale studies will be necessary to determine whether particular substrains of viruses confer an elevated risk of asthma exacerbation.

Mechanisms of virus-induced asthma exacerbations: state-of-the-art. A GA2LEN and InterAirways document

Viral infections of the respiratory tract are the most common precipitants of acute asthma exacerbations. Exacerbations are only poorly responsive to current asthma therapies and new approaches to therapy are needed. Viruses, most frequently human rhinoviruses (RV), infect the airway epithelium, generate local and systemic immune responses, as well as neural responses, inducing inflammation and airway hyperresponsiveness. Using in vitro and in vivo experimental models the role of various proinflammatory or anti‐inflammatory mediators, antiviral responses and molecular pathways that lead from infection to symptoms has been partly unravelled. In particular, mechanisms of susceptibility to viral infection have been identified and the bronchial epithelium appeared to be a key player. Nevertheless, additional understanding of the integration between the diverse elements of the antiviral response, especially in the context of allergic airway inflammation, as well as the interactions between viral infections and other stimuli that affect airway inflammation and responsiveness may lead to novel strategies in treating and/or preventing asthma exacerbations. This review presents the current knowledge and highlights areas in need of further research.

Antimicrobial strategies: an option to treat allergy?

Respiratory infections by bacteria and viruses often trigger symptoms of asthma in both adults and children. This observation and subsequent mechanistic studies have demonstrated important interactions among allergens, microbes and the atopic host. The mechanisms responsible for microbe-induced asthma exacerbations are only incompletely understood. A focal point of current research is the inflammatory response of the host following an encounter with a pathogenic microbe, including variations in chemokine and cytokine production and resulting in changes in bronchial hyper-responsiveness and lung function. Direct bronchial infection, exposure of nerves with resulting neurogenic inflammation and a deviated host immune response are among the mechanisms underlying these functional disorders. Lately, suboptimal innate immune responses, expressed as defective interferon production, have gained attention as they might be amenable to intervention. This review describes the suggested mechanisms involved in the complex interactions between 'asthmagenic' microbes, the immune system and atopy, based on in-vitro and in-vivo experimental models and epidemiological evidence. In addition, it provides a synopsis of potential therapeutic strategies either directly against the microorganisms or in respect to the associated inflammation.

Asthma exacerbations . 3: Pathogenesis

Asthma exacerbations are an exaggerated lower airway response to an environmental exposure. Respiratory virus infection is the most common environmental exposure to cause a severe asthma exacerbation. Airway inflammation is a key part of the lower airway response in asthma exacerbation, and occurs together with airflow obstruction and increased airway responsiveness. The patterns of airway inflammation differ according to the trigger factor responsible for the exacerbation. The reasons for the exaggerated response of asthmatic airways are not completely understood, but recent studies have identified a deficient epithelial type 1 interferon response as an important susceptibility mechanism for viral infection.