Sebastian L. Johnston

Community study of role of viral infections in exacerbations of asthma in 9-11 year old children.

Abstract Objective: To study the association between upper and lower respiratory viral infections and acute exacerbations of asthma in schoolchildren in the community. Design: Community based 13 month longitudinal study using diary card respiratory symptom and peak expiratory flow monitoring to allow early sampling for viruses. Subjects: 108 Children aged 9-11 years who had reported wheeze or cough, or both, in a questionnaire. Setting: Southampton and surrounding community. Main outcome measures: Upper and lower respiratory viral infections detected by polymerase chain reaction or conventional methods, reported exacerbations of asthma, computer identified episodes of respiratory tract symptoms or peak flow reductions. Results: Viruses were detected in 80% of reported episodes of reduced peak expiratory flow, 80% of reported episodes of wheeze, and in 85% of reported episodes of upper respiratory symptoms, cough, wheeze, and a fall in peak expiratory flow. The median duration of reported falls in peak expiratory flow was 14 days, and the median maximum fall in peak expiratory flow was 81 1/min. The most commonly identified virus type was rhinovirus. Conclusions: This study supports the hypothesis that upper respiratory viral infections are associated with 80-85% of asthma exacerbations in school age children. Key messages Key messages In this study common cold viruses were found in 80-85% of reported exacerbations of asthma in children Rhinoviruses, which cause most common colds, accounted for two thirds of viruses detected Analysis of diary cards also showed large numbers of similar but less severe episodes that may also be viral in origin

Asthmatic bronchial epithelial cells have a deficient innate immune response to infection with rhinovirus

Rhinoviruses are the major trigger of acute asthma exacerbations and asthmatic subjects are more susceptible to these infections. To investigate the underlying mechanisms of this increased susceptibility, we examined virus replication and innate responses to rhinovirus (RV)-16 infection of primary bronchial epithelial cells from asthmatic and healthy control subjects. Viral RNA expression and late virus release into supernatant was increased 50- and 7-fold, respectively in asthmatic cells compared with healthy controls. Virus infection induced late cell lysis in asthmatic cells but not in normal cells. Examination of the early cellular response to infection revealed impairment of virus induced caspase 3/7 activity and of apoptotic responses in the asthmatic cultures. Inhibition of apoptosis in normal cultures resulted in enhanced viral yield, comparable to that seen in infected asthmatic cultures. Examination of early innate immune responses revealed profound impairment of virus-induced interferon-β mRNA expression in asthmatic cultures and they produced >2.5 times less interferon-β protein. In infected asthmatic cells, exogenous interferon-β induced apoptosis and reduced virus replication, demonstrating a causal link between deficient interferon-β, impaired apoptosis and increased virus replication. These data suggest a novel use for type I interferons in the treatment or prevention of virus-induced asthma exacerbations.

Role of deficient type III interferon-λ production in asthma exacerbations

Rhinoviruses are the major cause of asthma exacerbations, and asthmatics have increased susceptibility to rhinovirus and risk of invasive bacterial infections. Here we show deficient induction of interferon-λs by rhinovirus in asthmatic primary bronchial epithelial cells and alveolar macrophages, which was highly correlated with severity of rhinovirus-induced asthma exacerbation and virus load in experimentally infected human volunteers. Induction by lipopolysaccharide in asthmatic macrophages was also deficient and correlated with exacerbation severity. These results identify previously unknown mechanisms of susceptibility to infection in asthma and suggest new approaches to prevention and/or treatment of asthma exacerbations.

Rhinoviruses Infect the Lower Airways

Rhinoviruses are the major cause of the common cold and a trigger of acute asthma exacerbations. Whether these exacerbations result from direct infection of the lower airway or from indirect mechanisms consequent on infection of the upper airway alone is currently unknown. Lower respiratory infection was investigated in vitro by exposing primary human bronchial epithelial cells to rhinoviruses and in vivo after experimental upper respiratory infection of human volunteers. Bronchial infection was confirmed by both approaches. Furthermore, rhinoviruses induced production of interleukin-6, -8, and -16 and RANTES and were cytotoxic to cultured respiratory epithelium. This evidence strongly supports a direct lower respiratory epithelial reaction as the initial event in the induction of rhinovirus-mediated asthma exacerbations. The frequency of infection and the nature of the inflammatory response observed are similar to those of the upper respiratory tract, suggesting that rhinovirus infections may be one of the most important causes of lower in addition to upper respiratory disease.

Frequency, severity, and duration of rhinovirus infections in asthmatic and non-asthmatic individuals: a longitudinal cohort study.

BACKGROUND Rhinovirus infections cause exacerbations of asthma. We postulated that people with asthma are more susceptible to rhinovirus infection than people without the disease and compared the susceptibility of these groups. METHODS We recruited 76 cohabiting couples. One person in every couple had atopic asthma and one was healthy. Participants completed daily diary cards of upper-respiratory-tract (URT) and lower-respiratory-tract (LRT) symptoms and measured peak expiratory flow twice daily. Every 2 weeks nasal aspirates were taken and examined for rhinovirus. Mixed models were used to compare risks of infection between groups. We also compared the severity and duration of infections. FINDINGS We analysed 753 samples. Rhinovirus was detected in 10.1% (38/378) of samples from participants with asthma and 8.5% (32/375) of samples from healthy participants. After adjustment for confounding factors, asthma did not significantly increase risk of infection (odds ratio 1.15, 95% CI 0.71-1.87). Groups did not differ in frequency, severity, or duration of URT infections or symptoms associated with rhinovirus infection. First rhinovirus infection was associated more frequently with LRT infection in participants with asthma than in healthy individuals (12 of 28 infections vs four of 23, respectively, p=0.051). Symptoms of LRT associated with rhinovirus infection were significantly more severe (p=0.001) and longer-lasting in participants with asthma than in healthy participants (p=0.005). INTERPRETATION People with atopic asthma are not at greater risk of rhinovirus infection than healthy individuals but suffer from more frequent LRT infections and have more severe and longer-lasting LRT symptoms.

Study of modifiable risk factors for asthma exacerbations: virus infection and allergen exposure increase the risk of asthma hospital admissions in children

Background: Asthma exacerbation is the most common cause of hospital admission in children. A study was undertaken to investigate the importance of allergen exposure in sensitised individuals in combination with viral infections and other potentially modifiable risk factors precipitating asthma hospital admission in children. Methods: Eighty four children aged 3–17 years admitted to hospital over a 1 year period with an acute asthma exacerbation (AA) were matched for age and sex with two control groups: stable asthmatics (SA) and children admitted to hospital with non-respiratory conditions (IC). Risk factors were assessed by questionnaires and determination of allergen sensitisation, home allergen exposure, pollen exposure, and respiratory virus infection. Results: Several non-modifiable factors (atopy, duration of asthma) were associated with increased risk. Among the modifiable factors, pet ownership, housing characteristics, and parental smoking did not differ between the groups. Regular inhaled corticosteroid treatment was significantly less common in the AA group than in the SA group (OR 0.2, 95% CI 0.1 to 0.6; p = 0.002). A significantly higher proportion of the AA group were virus infected (44%) and sensitised and highly exposed to sensitising allergen (76%) compared with the SA (18% and 48%) and IC groups (17% and 28%; both p<0.001). In a multiple conditional logistic regression (AA v SA), allergen sensitisation and exposure or virus detection alone were no longer independently associated with hospital admission. However, the combination of virus detection and sensitisation with high allergen exposure substantially increased the risk of admission to hospital (OR 19.4, 95% CI 3.7 to 101.5, p<0.001). Conclusions: Natural virus infection and real life allergen exposure in allergic asthmatic children increase the risk of hospital admission. Strategies for preventing exacerbations will need to address these factors.

Role of respiratory viruses in acute upper and lower respiratory tract illness in the first year of life : A birth cohort study

Introduction: Although acute respiratory illnesses (ARI) are major causes of morbidity and mortality in early childhood worldwide, little progress has been made in their control and prophylaxis. Most studies have focused on hospitalized children or children from closed populations. It is essential that the viral etiology of these clinical diseases be accurately defined in the development of antiviral drugs. Objective: To investigate the role of all common respiratory viruses as upper and lower respiratory tract pathogens in the first year of life. Study Design: This community-based birth cohort study prospectively collected detailed information on all ARI contracted by 263 infants from birth until 1 year of age. Nasopharyngeal aspirates were collected for each ARI episode, and all common respiratory viruses were detected by polymerase chain reaction. Episodes were classified as upper respiratory illnesses or lower respiratory illnesses (LRI), with or without wheeze. Results: The majority reported 2–5 episodes of ARI in the first year (range, 0–11 episodes; mean, 4.1). One-third were LRI, and 29% of these were associated with wheeze. Viruses were detected in 69% of ARI; most common were rhinoviruses (48.5%) and respiratory syncytial virus (RSV) (10.9%). Compared with RSV, >10 times the number of upper respiratory illnesses and >3 times the number of both LRI and wheezing LRI were attributed to rhinoviruses. Conclusion: Rhinoviruses are the major upper and lower respiratory pathogens in the first year of life. Although RSV is strongly associated with severe LRI requiring hospitalization, the role of rhinoviruses as the major lower respiratory pathogens in infants has not previously been recognized.

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-γ 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.

Acute exacerbations of chronic obstructive pulmonary disease: identification of biologic clusters and their biomarkers.

RATIONALE Exacerbations of chronic obstructive pulmonary disease (COPD) are heterogeneous with respect to inflammation and etiology. OBJECTIVES Investigate biomarker expression in COPD exacerbations to identify biologic clusters and determine biomarkers that recognize clinical COPD exacerbation phenotypes, namely those associated with bacteria, viruses, or eosinophilic airway inflammation. METHODS Patients with COPD were observed for 1 year at stable and exacerbation visits. Biomarkers were measured in sputum and serum. Viruses and selected bacteria were assessed in sputum by polymerase chain reaction and routine diagnostic bacterial culture. Biologic phenotypes were explored using unbiased cluster analysis and biomarkers that differentiated clinical exacerbation phenotypes were investigated. MEASUREMENTS AND MAIN RESULTS A total of 145 patients (101 men and 44 women) entered the study. A total of 182 exacerbations were captured from 86 patients. Four distinct biologic exacerbation clusters were identified. These were bacterial-, viral-, or eosinophilic-predominant, and a fourth associated with limited changes in the inflammatory profile termed “pauciinflammatory.” Of all exacerbations, 55%, 29%, and 28% were associated with bacteria, virus, or a sputum eosinophilia. The biomarkers that best identified these clinical phenotypes were sputum IL-1β, 0.89 (area under receiver operating characteristic curve) (95% confidence interval [CI], 0.83–0.95); serum CXCL10, 0.83 (95% CI, 0.70–0.96); and percentage peripheral eosinophils, 0.85 (95% CI, 0.78–0.93), respectively. CONCLUSIONS The heterogeneity of the biologic response of COPD exacerbations can be defined. Sputum IL-1β, serum CXCL10, and peripheral eosinophils are biomarkers of bacteria-, virus-, or eosinophil-associated exacerbations of COPD. Whether phenotype-specific biomarkers can be applied to direct therapy warrants further investigation.

Rhinovirus Infection Induces Expression of Its Own Receptor Intercellular Adhesion Molecule 1 (ICAM-1) via Increased NF-κB-mediated Transcription

Virus infections, the majority of which are rhinovirus infections, are the major cause of asthma exacerbations. Treatment is unsatisfactory, and the pathogenesis unclear. Lower airway lymphocyte and eosinophil recruitment and activation are strongly implicated, but the mechanisms regulating these processes are unknown. Intercellular adhesion molecule-1 (ICAM-1) has a central role in inflammatory cell recruitment to the airways in asthma and is the cellular receptor for 90% of rhinoviruses. We hypothesized that rhinovirus infection of lower airway epithelium might induce ICAM-1 expression, promoting both inflammatory cell infiltration and rhinovirus infection. We therefore investigated the effect of rhinovirus infection on respiratory epithelial cell ICAM-1 expression and regulation to identify new targets for treatment of virus-induced asthma exacerbations. We observed that rhinovirus infection of primary bronchial epithelial cells and the A549 respiratory epithelial cell line increased ICAM-1 cell surface expression over 12- and 3-fold, respectively. We then investigated the mechanisms of this induction in A549 cells and observed rhinovirus-induction of ICAM-1 promoter activity and ICAM-1 mRNA transcription. Rhinovirus induction of ICAM-1 promoter activity was critically dependent upon up-regulation of NF-κB proteins binding to the −187/−178 NF-κB binding site on the ICAM-1 promoter. The principal components of the rhinovirus-induced binding proteins were NF-κB p65 homo- or heterodimers. These studies identify ICAM-1 and NF-κB as new targets for the development of therapeutic interventions for virus-induced asthma exacerbations.