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

Role of viruses and atypical bacteria in asthma exacerbations among children in Oporto (Portugal)

BACKGROUND

Upper respiratory tract infections are known to be a significant precipitant of acute asthma exacerbations. The aim of this study was to evaluate seasonal trends and the role of these pathogens in asthma exacerbations in school-aged children from Oporto (Portugal).

METHODS

Nasal aspirates were collected from children aged 6 to 12 years old with asthma exacerbations attended in the Pediatric Emergency Department one day per week from January 1 to December 31, 2003. Demographic data, severity of asthma and asthma exacerbations, and current treatment were recorded. Samples were obtained through nasal wash with 1 ml saline and were processed by immunofluorescence assays (respiratory syncytial virus, adenovirus, parainfluenza and influenza virus), retrotranscription polymerase chain reaction (rhinovirus) and polymerase chain reaction (enterovirus, Chlamydia pneumoniae and Mycoplasma pneumoniae).

RESULTS

In 54 eligible children, 37 nasal samples were obtained. Infectious agents were detected in 78 % of the patients. Rhinovirus was detected in 70.3 %, Mycoplasma pneumoniae in 16.2 %, enterovirus in 10.8 %, and Chlamydia pneumoniae in 2.7 %. Coinfection was identified in 21.6 % of the samples. There was no significant correlation between current treatment status, severity of asthma or exacerbations and the isolated agents. Two distinct peaks of asthma exacerbation were found, 40.5 % in spring and 32.4 % in autumn [corrected] The highest number of cases was recorded in March and the lowest in August and January. Rhinoviruses was detected in 27 % of the cases in autumn and in 24.3 % in spring [corrected]

CONCLUSIONS

These results confirm the previously reported high frequency of rhinovirus detection in asthma exacerbations in children and provide evidence that asthma exacerbations and rhinovirus infections follow a seasonal pattern, occurring mostly in spring and autumn. The findings also underscore the frequency of Mycoplasma pneumoniae detection, and emphasize the importance of this agent as a possible trigger of asthma exacerbations.

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.

Respiratory syncytial virus infection and recurrent wheeze/asthma in children under five years: an epidemiological survey

AIM

To determine the rates of respiratory syncytial virus (RSV) infection in children under 5 years of age with recurrent wheeze or asthma and compare their clinical presentation, course and outcome with asthmatic children of the same age who did not have RSV.

METHODS

Children were recruited prospectively from the emergency department of the Royal Children's Hospital, Melbourne during peak RSV season in 1998. Information was collected regarding past and current asthma presentations, a nasopharyngeal asprirate was taken for viral isolation and all children were reviewed by telephone 1 week following presentation.

RESULTS

73 children were included with a median age of 28 months. RSV was isolated from 33 (45%) of children, one child had adenovirus and in the remainder no virus was isolated. Children less than 12 months were more likely to have RSV (70%). RSV-positive children had a longer duration of illness prior to hospital presentation than RSV-negative children but were not more likely to be admitted or to have a longer duration of ongoing symptoms.

CONCLUSION

A high rate of RSV infection was demonstrated in young children with recurrent wheeze or asthma during the RSV season. This information has important implications for the control of nosocomial infection with RSV (i.e. isolation of patients) and in targeting another group to be included for RSV vaccine development.

TLR3-mediated synthesis and release of eotaxin-1/CCL11 from human bronchial smooth muscle cells stimulated with double-stranded RNA

Respiratory infections with RNA viruses, such as rhinovirus or respiratory syncytial virus, are a major cause of asthma exacerbation, accompanied by enhanced neutrophilic and/or eosinophilic inflammation of the airways. We studied the effects of dsRNA synthesized during RNA virus replication, and of its receptor, TLR3, on the synthesis of eosinophilic chemokines in bronchial smooth muscle cells (BSMC). Synthetic dsRNA, polyinosinic-cystidic acid (poly(I:C)), induced the synthesis of eosinophilic chemokines, eotaxin-1/CCL11 and RANTES/CCL5, from primary cultures of human BSMC, and IL-4 increased synergistically the synthesis of poly(I:C)-induced CCL11. A robust eosinophil chemotactic activity was released from BSMC stimulated with poly(I:C) and IL-4, which was mostly inhibited by preincubation with an anti-CCL11, but not with an anti-CCL5 Ab. Although the immunoreactivity of TLR3 was detectable on the cellular surface of BSMC by flow cytometric analysis, pretreatment with an anti-TLR3-neutralizing Ab failed to block the poly(I:C)-induced synthesis of CCL11. We have determined by confocal laser-scanning microscopy that the immunoreactivity of TLR3 was aggregated intracellularly in poly(I:C)-stimulated BSMC, colocalizing with fluorescein-labeled poly(I:C). The synthesis of CCL11 was prominently inhibited by the transfection of TLR3-specific small interfering RNA or by bafilomycin A1, an endosomal acidification inhibitor, further supporting the essential role played by intracellular TLR3 in the synthesis of poly(I:C)-induced CCL11 in BSMC. In conclusion, these observations suggest that, by activating intracellular TLR3 in BSMC, respiratory RNA virus infections stimulate the production of CCL11 and enhance eosinophilic inflammation of the airways in the Th2-dominant microenvironment.

Plasmacytoid dendritic cells limit viral replication, pulmonary inflammation, and airway hyperresponsiveness in respiratory syncytial virus infection

Plasmacytoid dendritic cells (pDC), as major producers of IFN-alpha, are thought not only to be pivotal in antiviral immunity, but also to limit allergic inflammation. In this study, we delineate the role of pDC in a mouse model of respiratory syncytial virus (RSV)-induced airway inflammation. Bone marrow-derived pDC generated high levels of IFN-alpha upon RSV infection, and the percentage of pDC expressing MHC class II and maturation-associated costimulatory molecules was increased. However, their weak Ag-presenting capacity was not enhanced. Furthermore, pDC induced marked levels of IL-10 in T cell cultures irrespective of infection. In vivo, numbers of pDC in the lung increased early after RSV infection and remained elevated throughout the inflammatory phase and the resolution phase of infection. Depletion of pDC resulted in increases in peak RSV titers, pulmonary inflammation, and airway hyperresponsiveness. In contrast, adoptive transfer of activated pDC to the airways reduced RSV copy numbers. In conclusion, RSV infection induces activation of murine pDC with robust IFN-alpha production, limiting replication and accelerating elimination of RSV. In addition to this innate response, pDC also may play an immune regulatory role in reducing pulmonary inflammation and inhibiting the development of airway hyperresponsiveness.

Transforming growth factor-beta expression induced by rhinovirus infection in respiratory epithelial cells

Rhinovirus infection of the lower airways is now a recognized disease, associated with bronchiolitis and asthma. The bronchial epithelial cells are the host cells when rhinovirus infection occurs in the airway. It was hypothesized that a pro-fibrotic growth factor response may occur in these infected cells, leading to production of a key transforming growth factor, TGF-beta-1. Bronchial epithelial cells were inoculated with human rhinovirus and compared at day 1, 3 and 5 to control non-infected cells. Cell culture supernatant fluid and cellular RNA were isolated. The amount of released TGF-beta protein was measured by enzyme-linked immunosorbent assay (ELISA). Expression of TGF-beta at the level of transcription was measured by polymerase chain reaction (PCR) and gel electrophoresis. The results show that at all time points studied, TGF-beta production is greater in the infected cells, as demonstrated by ELISA (P<0.05) and by semi-quantitative PCR analysis. It was concluded that bronchial epithelial cells infected with common cold virus and rhinovirus, showed higher levels of TGF-beta. The production of TGF-beta may be indicative of a normal repair mechanism to counter inflammation, or in the setting of persistent asthma, could potentially lead to increased fibrosis and collagen deposition.

Prevalence of viral respiratory tract infections in children with asthma

Background

Previous studies support a strong association between viral respiratory tract infections and asthma exacerbations. The effect of newly discovered viruses on asthma control is less well defined.

Objective

We sought to determine the contribution of respiratory viruses to asthma exacerbations in children with a panel of PCR assays for common and newly discovered respiratory viruses.

Methods

Respiratory specimens from children aged 2 to 17 years with asthma exacerbations (case patients, n = 65) and with well-controlled asthma (control subjects, n = 77), frequency matched by age and season of enrollment, were tested for rhinoviruses, enteroviruses, respiratory syncytial virus, human metapneumovirus, coronaviruses 229E and OC43, parainfluenza viruses 1 to 3, influenza viruses, adenoviruses, and human bocavirus.

Results

Infection with respiratory viruses was associated with asthma exacerbations (63.1% in case patients vs 23.4% in control subjects; odds ratio, 5.6; 95% CI, 2.7- 11.6). Rhinovirus was by far the most prevalent virus (60% among case patients vs 18.2% among control subjects) and the only virus significantly associated with exacerbations (odds ratio, 6.8; 95% CI, 3.2-14.5). However, in children without clinically manifested viral respiratory tract illness, the prevalence of rhinovirus infection was similar in case patients (29.2%) versus control subjects (23.4%, P > .05). Other viruses detected included human metapneumovirus (4.6% in patients with acute asthma vs 2.6% in control subjects), enteroviruses (4.6% vs 0%), coronavirus 229E (0% vs 1.3%), and respiratory syncytial virus (1.5% vs 0%).

Conclusion

Symptomatic rhinovirus infections are an important contributor to asthma exacerbations in children.

Clinical implications

These results support the need for therapies effective against rhinovirus as a means to decrease asthma exacerbations.

Rhinovirus activates interleukin-8 expression via a Src/p110beta phosphatidylinositol 3-kinase/Akt pathway in human airway epithelial cells

Rhinovirus (RV) is responsible for the majority of common colds and triggers exacerbations of asthma and chronic obstructive lung disease. We have shown that RV serotype 39 (RV39) infection activates phosphatidylinositol 3 (PI 3)-kinase and the serine threonine kinase Akt minutes after infection and that the activation of PI 3-kinase and Akt is required for maximal interleukin-8 (IL-8) expression. Here, we further examine the contributions of Src and PI 3-kinase activation to RV-induced Akt activation and IL-8 expression. Confocal fluorescent microscopy of 16HBE14o- human bronchial epithelial cells showed rapid (10-min) colocalization of RV39 with Src, p85alpha PI 3-kinase, p110beta PI 3-kinase, Akt and Cit-Akt-PH, a fluorescent Akt pleckstrin homology domain which binds PI(3,4,5)P(3). The chemical Src inhibitor PP2 {4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo [3,4-d]pyrimidine} and the PI 3-kinase inhibitor LY294002 each inhibited Akt phosphorylation and the colocalization of RV39 with Akt. Digoxigenin-tagged RV coprecipitated with a Crosstide kinase likely to be Akt, and inhibition of Src blocked kinase activity. Digoxigenin-tagged RV39 colocalized with the lipid raft marker ceramide. In 16HBE14o- and primary mucociliary differentiated human bronchial epithelial cells, inhibition of Src kinase activity with the Src family chemical inhibitor PP2, dominant-negative Src (K297R), and Src small interfering RNA (siRNA) each inhibited RV39-induced IL-8 expression. siRNA against p110beta PI 3-kinase also inhibited IL-8 expression. These data demonstrate that, in the context of RV infection, Src and p110beta PI 3-kinase are upstream activators of Akt and the IL-8 promoter and that RV colocalizes with Src, PI 3-kinase, and Akt in lipid rafts.

How viral infections cause exacerbation of airway diseases

Exacerbations of asthma and COPD are major causes of morbidity, mortality, and health-care costs. Over the last decade, studies using new molecular diagnostic techniques have established that respiratory viruses are a major cause of exacerbations of both asthma and COPD. The most prevalent viruses detected during exacerbations are the rhinoviruses. Despite the burden of disease associated with exacerbations, little is known about the mechanisms of virus-induced exacerbations of airway diseases. Exacerbations are associated with increased airway inflammation in patients with both asthma and COPD, but many questions remain unanswered regarding the key inflammatory cells and mediators involved. Identifying the key inflammatory mediators involved in exacerbations holds the promise of developing diagnostic and prognostic markers of exacerbation. In addition, such studies can identify new therapeutic targets for the development of novel drugs for the prevention and treatment of exacerbations.

Short-course montelukast for intermittent asthma in children: a randomized controlled trial

RATIONALE

In children, intermittent asthma is the most common pattern and is responsible for the majority of exacerbations. Montelukast has a rapid onset of action and may be effective if used intermittently.

OBJECTIVES

To determine whether a short course of montelukast in children with intermittent asthma would modify the severity of an asthma episode.

METHODS

Children, aged 2-14 years with intermittent asthma participated in this multicenter, randomized, double-blind, placebo-controlled clinical trial over a 12-month period. Treatment with montelukast or placebo was initiated by parents at the onset of each upper respiratory tract infection or asthma symptoms and continued for a minimum of 7 days or until symptoms had resolved for 48 hours.

MEASUREMENTS AND MAIN RESULTS

A total of 220 children were randomized, 107 to montelukast and 113 to placebo. There were 681 treated episodes (345 montelukast, 336 placebo) provided by 202 patients. The montelukast group had 163 unscheduled health care resource utilizations for asthma compared with 228 in the placebo group (odds ratio, 0.65; 95% confidence interval, 0.47-0.89). There was a nonsignificant reduction in specialist attendances and hospitalizations, duration of episode, and beta-agonist and prednisolone use. Symptoms were reduced by 14% and nights awakened by 8.6% (p = 0.043), and days off from school or childcare by 37% and parent time off from work by 33% (p < 0.0001 for both).

CONCLUSIONS

A short course of montelukast, introduced at the first signs of an asthma episode, results in a modest reduction in acute health care resource utilization, symptoms, time off from school, and parental time off from work in children with intermittent asthma.

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.

Respiratory syncytial virus disease mechanisms implicated by human, animal model, and in vitro data facilitate vaccine strategies and new therapeutics

Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis, pneumonia, mechanical ventilation, and respiratory failure in infants in the US. No effective post-infection treatments are widely available, and currently there is no vaccine. RSV disease is the result of virus-induced airway damage and complex inflammatory processes. The outcome of infection depends on host and viral genetics. Here, we review disease mechanisms in primary RSV infection that are implicated by clinical studies, in vitro systems, and animal models. Defining RSV disease mechanisms is difficult because there is a wide range of RSV disease phenotypes in humans, and there are disparities in RSV disease phenotypes among the animal models of RSV infection. However, host factors identified by multiple lines of investigation as playing important roles in RSV pathogenesis are providing key insights. A better understanding of RSV molecular biology and RSV pathogenesis is facilitating rational vaccine design strategies and molecular targets for new therapeutics.

AluyMICB dimorphism within the class I region of the major histocompatibility complex is associated with asthma and airflow obstruction in the Busselton population

AIM

To examine the association between the Alu dimorphism within the first intron of the MICB gene and asthma and airflow obstruction. Background The highly polymorphic non-classical MHC class I polypeptide-related (MIC) genes, MICA and MICB, encode stress inducible glycoproteins, which are expressed on a variety of epithelial cells, including those of the lungs.

METHODS

AluyMICB genotyping was performed on 1109 subjects from the Busselton Health Study. From a standard questionnaire, 359 individuals indicated that they had been diagnosed by a doctor with asthma. Lung function was assessed by the forced expired volume in 1 second (FEV1) and expressed as a percent of the predicted value. Airflow obstruction was defined as FEV1<80% predicted.

RESULTS

In men, a dominant relationship was found between the AluyMICB DD genotype and asthma (P=0.006; chi2(2)=7.65). Furthermore, multivariate analysis adjusted for age, height, weight and body mass index (BMI) showed a relationship between DD genotype and asthma in men in a dominant model (odds ratio (OR)=1.97; 95% confidence interval (CI)=1.11-3.51; P=0.021). In women, an association was found between the AluyMICB II genotype and FEV1 percent predicted as a continuous variable (P=0.001). When adjusted for age and BMI, it showed a significant relationship between AluyMICB and airflow obstruction in a dominant model (OR=14.11%, 95% CI 3.29-60.57, P<0.001). However, no association was found between the AluyMICB II genotypes and airflow obstruction in men.

CONCLUSION

These findings suggest the possible involvement of a MHC class I gene in abnormal airway structure in women and airway function in men.

Asthma exacerbations. 2: aetiology

The natural history of asthma involves relatively stable periods that are often punctuated by significant exacerbations of symptoms. There are many aetiologies that may lead to an increase in asthma severity including respiratory infection (bacterial/viral), allergens, irritants, and occupational exposures. Each trigger probably acts through different mechanisms, but a final common pathway of multicellular inflammation, enhanced bronchial responsiveness, and airflow obstruction is a likely consequence. This review discusses the most common causes of asthma exacerbations with a focus on their microbiology and immunopathogenesis. Through an understanding of underlying causes of asthma exacerbations, treatments with increased effectiveness may be developed, and it is these future developments that may directly influence the morbidity and mortality of the disease.

Comparison of the efficacy and safety of live attenuated cold-adapted influenza vaccine, trivalent, with trivalent inactivated influenza virus vaccine in children and adolescents with asthma

BACKGROUND

Despite their potential for increased morbidity, 75% to 90% of asthmatic children do not receive influenza vaccination. Live attenuated influenza vaccine (LAIV), a cold-adapted, temperature-sensitive, trivalent influenza vaccine, is approved for prevention of influenza in healthy children 5 to 19 years of age. LAIV has been studied in only a small number of children with asthma.

METHODS

Children 6 to 17 years of age, with a clinical diagnosis of asthma, received a single dose of either intranasal CAIV-T (an investigational refrigerator-stable formulation of LAIV; n = 1114) or injectable trivalent inactivated influenza vaccine (TIV; n = 1115) in this randomized, open-label study during the 2002-2003 influenza season. Participants were followed up for culture-confirmed influenza illness, respiratory outcome, and safety.

RESULTS

The incidence of community-acquired culture-confirmed influenza illness was 4.1% (CAIV-T) versus 6.2% (TIV), demonstrating a significantly greater relative efficacy of CAIV-T versus TIV of 34.7% (90% confidence interval [CI] 9.4%-53.2%; 95% CI = 3.9%-56.0%). There were no significant differences between treatment groups in the incidence of asthma exacerbations, mean peak expiratory flow rate findings, asthma symptom scores, or nighttime awakening scores. The incidence of runny nose/nasal congestion was higher for CAIV-T (66.2%) than TIV (52.5%) recipients. Approximately 70% of TIV recipients reported injection site reactions.

CONCLUSIONS

CAIV-T was well tolerated in children and adolescents with asthma. There was no evidence of a significant increase in adverse pulmonary outcomes for CAIV-T compared with TIV. CAIV-T had a significantly greater relative efficacy of 35% compared with TIV in this high-risk population.

Protein kinase R, IkappaB kinase-beta and NF-kappaB are required for human rhinovirus induced pro-inflammatory cytokine production in bronchial epithelial cells

Rhinovirus infections cause the majority of acute exacerbations of airway diseases such as asthma and chronic obstructive pulmonary disease, with increased pro-inflammatory cytokine production by infected bronchial epithelial cells contributing to disease pathogenesis. Theses diseases are a huge cause of morbidity worldwide, and contribute a major economic burden to healthcare costs. Current steroid based treatments are only partially efficient at controlling virus induced inflammation, which remains an unmet therapeutic goal. Although NF-kappaB has been implicated, the precise mechanisms of rhinovirus induction of pro-inflammatory gene expression in bronchial epithelial cells are unclear. We hypothesised that rhinovirus replication and generation of dsRNA was an important process of pro-inflammatory cytokine induction. Using pharmalogical (2-aminopurine and a new small molecule inhibitor) and genetic inhibition of the dsRNA binding kinase protein kinase R, striking inhibition of dsRNA (polyrIC) and rhinovirus induced CCL5, CXCL8 and IL-6 protein was observed. Using confocal microscopy, rhinovirus induced protein kinase R phosphorylation co-located with NF-kappaB p65 nuclear translocation. Focusing on CXCL8, both rhinovirus infection and dsRNA treatment required IkappaB kinase-beta for induction of CXCL8. Analysis of cis-acting sites in the CXCL8 promoter revealed that both rhinovirus infection and dsRNA treatment upregulated CXCL8 promoter activation via NF-kappaB and NF-IL6 binding sites. Together, the results demonstrate the importance of dsRNA in induction of pro-inflammatory cytokines by rhinoviruses, and suggest that protein kinase R is involved in NF-kappaB mediated gene transcription of pro-inflammatory cytokines via IkappaB kinase-beta. These molecules regulating rhinovirus induction of inflammation represent therapeutic targets.

Rhinovirus replication in human macrophages induces NF-kappaB-dependent tumor necrosis factor alpha production

Rhinoviruses (RV) are the major cause of acute exacerbations of asthma and chronic obstructive pulmonary disease (COPD). Rhinoviruses have been shown to activate macrophages, but rhinovirus replication in macrophages has not been reported. Tumor necrosis factor alpha (TNF-alpha) is implicated in the pathogenesis of acute exacerbations, but its cellular source and mechanisms of induction by virus infection are unclear. We hypothesized that rhinovirus replication in human macrophages causes activation and nuclear translocation of NF-kappaB, leading to TNF-alpha production. Using macrophages derived from the human monocytic cell line THP-1 and from primary human monocytes, we demonstrated that rhinovirus replication was productive in THP-1 macrophages, leading to release of infectious virus into supernatants, but was limited in monocyte-derived macrophages, likely due to type I interferon production, which was robust in monocyte-derived but deficient in THP-1-derived macrophages. Similar to bronchial epithelial cells, only small numbers of cells supported complete virus replication. We demonstrated RV-induced activation of NF-kappaB and colocalization of p65/NF-kappaB nuclear translocation with virus replication in both macrophage types. The infection induced TNF-alpha release in a time- and dose-dependent, RV serotype- and receptor-independent manner and was largely (THP-1 derived) or completely (monocyte derived) dependent upon virus replication. Finally, we established the requirement for NF-kappaB but not p38 mitogen-activated protein kinase in induction of TNF-alpha. These data suggest RV infection of macrophages may be an important source of proinflammatory cytokines implicated in the pathogenesis of exacerbations of asthma and COPD. They also confirm inhibition of NF-kappaB as a promising target for development of new therapeutic intervention strategies.

Role of CCL5 (RANTES) in viral lung disease

CCL5/RANTES is a key proinflammatory chemokine produced by virus-infected epithelial cells and present in respiratory secretions of asthmatics. To examine the role of CCL5 in viral lung disease, we measured its production during primary respiratory syncytial virus (RSV) infection and during secondary infection after sensitizing vaccination that induces Th2-mediated eosinophilia. A first peak of CCL5 mRNA and protein production was seen at 18 to 24 h of RSV infection, before significant lymphocyte recruitment occurred. Treatment in vivo with Met-RANTES (a competitive chemokine receptor blocker) throughout primary infection decreased CD4+ and CD8+ cell recruitment and increased viral replication. In RSV-infected, sensitized mice with eosinophilic disease, CCL5 production was further augmented; Met-RANTES treatment again reduced inflammatory cell recruitment and local cytokine production. A second wave of CCL5 production occurred on day 7, attributable to newly recruited T cells. Paradoxically, mice treated with Met-RANTES during primary infection demonstrated increased cellular infiltration during reinfection. We therefore show that RSV induces CCL5 production in the lung and this causes the recruitment of RSV-specific cells, including those making additional CCL5. If this action is blocked with Met-RANTES, inflammation decreases and viral clearance is delayed. However, the exact effects of chemokine modulation depend critically on time of administration, a factor that may potentially complicate the use of chemokine blockers in inflammatory diseases.

Respiratory viral infections drive chemokine expression and exacerbate the asthmatic response

A number of investigations have linked respiratory vial infections and the intensity and subsequent exacerbation of asthma through host response mechanisms. For example, it is likely that the immune-inflammatory response to respiratory syncytial virus can cause a predisposition toward an intense inflammatory reaction associated with asthma, and adenovirus might cause exacerbation of the immune response associated with chronic obstructive pulmonary disease. In each of these situations, the host's immune response plays a critical mechanistic role through the production of certain cytokines and chemokines. Specific aspects of these augmented immune responses are determined by the biology of the virus, the genetic variability of the host, and the cytokine-chemokine phenotype of the involved tissue. For instance, the type 1/type 2 cytokine ratio in the airways during infection with rhinovirus determines how long the viral infection endures. By this same theory, it has been demonstrated that chemokine levels produced during respiratory syncytial virus infection determine host responses to later immune stimuli in the lung, with the potential to augment the asthmatic response. Further research in this area will clarify cytokines, chemokines, or cell targets, which will provide the basis for next-generation therapies.

The role of respiratory viruses in the pathogenesis of pediatric asthma

The role of respiratory viral infection in the development of asthma remains unclear. A number of factors play crucial roles, including the type of virus, the severity of the disease, the time of the infection, and, most important, the host predisposition. On the other hand, there is little doubt that a strong association exists between viral respiratory infections and induction of wheezing illnesses and asthma exacerbations. The underlying mechanisms, although not fully clarified, are likely to be multifactorial, involving inflammation of the bronchial mucosa, which interacts under certain circumstances with allergic inflammation. In addition, repetitive infections play an important role in perpetuating inflammation and airway hyperresponsiveness, especially in the presence of atopy, leading from childhood asthma to a more persistent asthma phenotype.

Role of deficient type III interferon-lambda 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-lambdas 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.

The relationship between respiratory syncytial virus infections and the development of wheezing and asthma in children

PURPOSE OF REVIEW

The relationship between respiratory syncytial virus lower-respiratory-tract infections in early childhood and asthma has been the subject of much debate. Most, but not all, previous cohort studies have failed to identify a link between early respiratory syncytial virus infection and atopic asthma. Recent studies have helped clarify some apparently contradictory findings.

RECENT FINDINGS

Cohort studies focusing on wheezing in early childhood have indicated that this is associated with an increased incidence of atopic asthma but that this risk is not increased by respiratory syncytial virus infection. Indeed, wheeze associated with rhinovirus infection may be a better marker for possible asthma. In contrast, there is no increased risk of atopic disease in infants with respiratory syncytial virus 'acute bronchiolitis', a phenotype characterized by widespread crepitation. Post-bronchiolitic symptoms are associated with intercurrent viral infections in particular and the incidence of symptoms falls rapidly during infancy.

SUMMARY

These studies confirm earlier suggestions that the phenotype of respiratory illness and hence the host response rather than the infecting organism is the best predictor of the future pattern of respiratory illness. Such considerations must be central to the design of any future intervention or cohort studies.

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.

Variação sazonal nos atendimentos de emergência por asma em Gama, Distrito Federal

OBJETIVO: Quantificar o atendimento por asma em um serviço de emergência público e estudar a flutuação sazonal, considerando as condições climáticas locais, caracterizadas por duas estações, uma chuvosa e úmida e outra seca. MÉTODOS: Levantamento retrospectivo conduzido em um hospital geral comunitário. Um total de 37.642 consultas emergenciais por asma, bronquite, pneumonia, infecções de vias aéreas superiores e outras condições foram identificadas durante um período de dois anos. As informações constantes em cada guia de atendimento foram levantadas para posterior análise. RESULTADOS: Asma foi o segundo diagnóstico mais freqüente dentre as condições respiratórias (24%). A maioria das consultas por asma foi feita em crianças de zero a catorze anos (56,6%). A análise de regressão mostrou uma variação sazonal dos atendimentos, com concentração significativamente maior de casos de asma no mês de março (p = 0,0109) e concentração menor nos meses de agosto e setembro (p = 0,0485 e p = 0,0169, respectivamente). A correlação entre asma e clima foi mais significativa em relação à flutuação da umidade defasada de um e dois meses (p = 0,0026 e p = 0,0002, respectivamente). CONCLUSÃO: As visitas por asma ao pronto-socorro foram mais freqüentes durante a estação úmida. O aumento do número de casos cresceu um a dois meses após o aumento da umidade e diminuiu no período seco. Essa correlação positiva levanta a possibilidade de uma relação causal com a proliferação de ácaros domésticos e fungos ambientais.

Viral upper respiratory tract infections in young children with emphasis on acute otitis media

Viral upper respiratory infection is the most common reason for seeking medical care for children. Recurrent viral respiratory infections and subsequent complications (e.g. acute otitis media (AOM)) are a burden for children, their families and society. Over the past decade, our knowledge on the significance of respiratory viruses has broadened remarkably. Viruses cause large variety of respiratory diseases and cause alone diseases, which previously have been assumed to be bacterial only (e.g. AOM and pneumonia). Methods for detection analysis of respiratory viruses are developing making both the diagnosis and epidemiological investigations of respiratory infections easier. Accurate diagnosis of respiratory infections and awareness of possible viral etiology could reduce the use of antibiotics. Etiologic studies of viral infections are becoming increasingly important, with the emergence of new antiviral drugs and vaccines.

Bronchiolitis

Bronchiolitis is a distressing, potentially life-threatening respiratory condition that affects young babies. Around 2-3% of all infants younger than 1 year are admitted to hospital with bronchiolitis, usually during the seasonal epidemic. The majority of these infants are infected with respiratory syncytial virus and all have an intense inflammatory response in their airways. Although most infants recover, they have an increased risk of recurrent wheezing. Although bronchiolitis is common, little is known about what causes infants to be susceptible. Diagnostic interventions have little effect on clinical outcome, and apart from supportive measures, there is no specific treatment. Bronchiolitis therefore presents an intriguing clinical conundrum and a major challenge to researchers. High quality clinical studies are needed to clarify assessment of disease severity and criteria for hospital admission, particularly the use of pulse oximetry and chest radiography. Careful mapping of the inflammatory pathways in the pathogenesis of bronchiolitis should lead to development of new therapies to alleviate symptoms.

Influenza vaccine in patients with asthma

Influenza virus continues to be a major cause of respiratory infection and is an important contributor to morbidity and mortality in at-risk populations, including those with underlying pulmonary conditions such as asthma. Vaccination with inactivated influenza vaccine remains the most popular method in controlling influenza through prevention. Current guidelines recommend the administration of the influenza vaccine to all patients with asthma. However, a third or fewer of those patients with asthma are currently receiving this vaccine. In this review, the risk-versus-benefit of influenza vaccination in children and adults with asthma is evaluated, based on the current evidence.

Role of viral infections in asthma and chronic obstructive pulmonary disease

Substantial evidence implicates common respiratory viral infections in the pathogenesis of asthma and chronic obstructive pulmonary disease (COPD). Children who experience recurrent virally induced wheezing episodes during infancy are at greater risk for developing asthma. In addition, respiratory viral infections are a major trigger for acute exacerbations of both asthma and COPD. Despite the importance of viral infections in asthma and COPD, the mechanisms by which viruses predispose to, or cause exacerbations of, these diseases remain poorly understood. It is clear that viral infections lead to enhanced airway inflammation and can cause airways hyperresponsiveness. The epithelial cell is the principal site of viral infection in the airways and plays a central role in viral modulation of airway inflammation via release of a variety of cytokines, chemokines, and growth factors. The mechanisms by which viral infections modulate epithelial function, therefore, is a topic of intense investigation. The epithelium also contributes to the host innate defense response to viral infection by releasing products that are antiviral and/or can lead to increased recruitment of dendritic cells and lymphocytes. Some evidence supports a role for the epithelial cell in specific immunity, although the response of more conventional cells of the immune system to viral infections is likely the dominant factor in this regard. Although current therapies may help combat virally induced disease exacerbations, they are less than ideal. A better understanding of the mechanisms underlying viral modulation of these diseases, therefore, may lead to new therapeutic approaches.

Human rhinovirus attenuates the type I interferon response by disrupting activation of interferon regulatory factor 3

The type I interferon (IFN) response requires the coordinated activation of the latent transcription factors NF-kappaB, interferon regulatory factor 3 (IRF-3), and ATF-2, which in turn activate transcription from the IFN-beta promoter. Synthesis and subsequent secretion of IFN-beta activate the Jak/STAT signaling pathway, resulting in the transcriptional induction of the full spectrum of antiviral gene products. We utilized high-density microarrays to examine the transcriptional response to rhinovirus type 14 (RV14) infection in HeLa cells, with particular emphasis on the type I interferon response and production of IFN-beta. We found that, although RV14 infection results in altered levels of a wide variety of host mRNAs, induction of IFN-beta mRNA or activation of the Jak/STAT pathway is not seen. Prior work has shown, and our results have confirmed, that NF-kappaB and ATF-2 are activated following infection. Since many viruses are known to target IRF-3 to inhibit the induction of IFN-beta mRNA, we analyzed the status of IRF-3 in infected cells. IRF-3 was translocated to the nucleus and phosphorylated in RV14-infected cells. Despite this apparent activation, very little homodimerization of IRF-3 was evident following infection. Similar results in A549 lung alveolar epithelial cells demonstrated the biological relevance of these findings to RV14 pathogenesis. In addition, prior infection of cells with RV14 prevented the induction of IFN-beta mRNA following treatment with double-stranded RNA, indicating that RV14 encodes an activity that specifically inhibits this innate host defense pathway. Collectively, these results indicate that RV14 infection inhibits the host type I interferon response by interfering with IRF-3 activation.

Picornavirus infections in children diagnosed by RT-PCR during longitudinal surveillance with weekly sampling: Association with symptomatic illness and effect of season

RT-PCR is more sensitive for rhinovirus detection than cell culture, but healthy controls are frequently rhinovirus (or picornavirus) positive in cross-sectional studies. Fifteen healthy children were followed over at least three seasons of the year with weekly sampling of nasal/nasopharyngeal secretion for RT-PCR testing for picornavirus and daily recording of respiratory symptoms. One sample positive for picornavirus was diagnosed as an infection; consecutive positive weekly samples constituted a single infection. Picornavirus illness was diagnosed if RNA was detected 7 days prior through 21 days after onset. One hundred fifty-five (21%) of 740 weekly samples were picornavirus positive and associated with illness; 37(5%) positives were not associated with illness (P = 0.001). The 192 positive samples occurred in 121 infections, 74 with a single positive and 47 with "runs" of positives in two or more consecutive samples. Forty five (96%) of the 47 runs comprised 2 or 3 consecutive positives. Ninety six (52%) of 185 reported illnesses during 235 child-months were picornavirus positive (0.4/child-month); 25 infections were asymptomatic (0.11/child-month). The infection rate was highest in fall (0.66/child-month); the winter rate (0.44/child-month) was similar to that in spring (0.5) and summer (0.43). Picornavirus infections in healthy children were common (0.51/child-month), episodic, and usually associated with brief illness; one fifth of infections were asymptomatic. The infection rate was highest in fall; infections in winter occurred at the same rate as in spring and summer.

Vascular endothelial growth factor induction by rhinovirus infection

Vascular participation manifested by a runny nose (rhinorrhea) is a prominent feature of the acute consequences of rhinovirus infection. Vascular endothelial growth factor (VEGF) is an angiogenic factor that also induces potent increases in vascular permeability; it is a candidate mediator of rhinorrhea in response to rhinovirus infection as well as contributing to enhanced vascular leakage in rhinovirus-linked asthma exacerbations. It has been shown that rhinovirus induces significant increases in both VEGF protein and mRNA in primary airway fibroblasts [Ghildyal et al. (2005): J Med Virol 75:608-615]. The current studies assessed VEGF responses to rhinovirus in primary culture airway epithelium, in epithelial and fibroblast cell lines and in rhinovirus-infected nasal secretions. Epithelial and fibroblast cells were infected with rhinovirus serotype 16 and VEGF protein and isoforms assessed by ELISA and RT-PCR, respectively. VEGF protein was released by both epithelial and fibroblast cell lines and primary airway epithelial cells in culture but was not increased following rhinovirus infection. PCR products coding for four or five of the six known VEGF isoforms were produced (121, 145, 165 and 183, and/or 189 amino acids) in cell lines and primary culture cells, but no specific isoform was linked to rhinovirus infection. Nasal VEGF was also measured in a cohort of asthmatics with verified rhinovirus and respiratory syncytial virus (RSV) infection. VEGF was not raised following rhinovirus infection alone, but was increased significantly if concomitant RSV infection was present. The data suggest that fibroblasts rather than the epithelium may play a key role in VEGF mediated vascular responses after rhinovirus infection. This may aid recruitment of inflammatory cells and contribute to airway inflammation and bronchial obstruction.

The many faces of the hygiene hypothesis

About 15 years have gone by since Strachan first proposed the idea that infections and unhygienic contact might confer protection against the development of allergic illnesses. The so-called hygiene hypothesis has ever since undergone numerous more or less subtle modifications by various researchers in the fields of epidemiology, clinical science, and immunology. Three major tracts have developed exploring the role of overt viral and bacterial infections, the significance of environmental exposure to microbial compounds, and the effect of both on underlying responses of the innate and adaptive immunity. To date, a truly unifying concept has not yet emerged, but various pieces of a complex interplay between immune responses of the host, characteristics of the invading microorganism, the level and variety of the environmental exposure, and the interactions between a genetic background and a range of exposures becomes apparent. These influences are discussed as determinants for a number of complex allergic illnesses in this review, while we attempt to pay attention to the importance of different phenotypes, namely of the asthma syndrome. Even if today practical implications cannot directly be deduced from these findings, there is great potential for the development of novel preventive and therapeutic strategies in the future.

Serum regulated upon activation, normal T cell expressed and presumably secreted concentrations and eosinophils in respiratory syncytial virus infection

BACKGROUND

The aim of this study was to characterize respiratory syncytial virus (RSV) infection. To do this, the authors evaluated eosinophil counts and chemokines including regulated upon activation, normal T cell expressed and presumably secreted (RANTES) in children with RSV, adenoviral, and influenza virus infections.

METHODS

The authors enrolled 80 patients who had been diagnosed with acute viral respiratory infection caused by RSV, adenoviral, or influenza viruses. In total, 35 patients (Group A) had RSV infection, 18 (Group B) had adenoviral infection, and 27 (Group C) had influenza virus infection. The authors evaluated clinical manifestations, white blood cell and eosinophil counts, and serum chemokines including RANTES concentrations in the acute and recovery phases in each group.

RESULTS

In recovery phase, eosinophil counts were higher in Group A than Groups B and C. In Group A, eosinophil counts were higher in recovery phase than in the acute phase. In Group A, serum RANTES concentration was significantly higher in the recovery phase than in the acute phase (132+/-76 pg/mL vs 52+/-25 pg/mL, P<0.05).

CONCLUSION

The findings suggest that high values of RANTES in children with RSV infection may be associated with the presence of eosinophils and be an important mediator of inflammatory response.

Antibiotic treatment of wheezing in children with asthma: what is the practice?

OBJECTIVE

Antibiotics are not recommended for the treatment of wheezing in children with asthma, but little is known about their use. This study was undertaken to evaluate trends and determinants of antibiotic use in children with wheezing during the fiscal years 1995 through 2001.

METHODS

Using the population-based health care and prescription databases in Manitoba, Canada, this descriptive study examined time trends in antibiotic prescription use for wheezing episodes in a population of children with asthma. The likelihood of receiving an antibiotic prescription according to child and physician characteristics also was determined. Annual population-based rates of antibiotic prescriptions for wheezing episodes were modeled by age and antibiotic class, using general estimating equations. The odds ratio for receiving an antibiotic prescription according to child demographics and physician factors was determined from hierarchical linear modeling.

RESULTS

The antibiotic prescription rate for wheezing decreased by 28% from 708 prescriptions per 1000 children with asthma in 1995 to 511 prescriptions in 2001. Fifteen-fold increases in use were observed for broader spectrum macrolides in preschool children. Twenty-three percent of physician visits for wheezing resulted in an immediate antibiotic prescription, but this percentage increased to 64% for antibiotics that were received within 7 days of the episode. General practitioners prescribed antibiotics more often than did pediatricians. Physicians who were not trained in Canada or the United States were 40% more likely to prescribe antibiotics than their counterparts.

CONCLUSIONS

Antibiotic use for wheezing in children declined in the 1990s, but the increased use of broader spectrum macrolides has implications for antibiotic resistance. A link between antibiotic prescribing and physician specialty and location of training identifies opportunities for intervention.

Combined fluticasone propionate and salmeterol reduces RSV infection more effectively than either of them alone in allergen-sensitized mice

BACKGROUND

Respiratory syncytial virus (RSV) infection is the major cause of bronchiolitis in infants and is a risk factor for the development of asthma. Allergic asthmatics are more susceptible to RSV infection and viral exacerbation.

METHODS

Since the effectiveness of corticosteroids in treating RSV infection has been controversial, we tested fluticasone propionate (FP) and salmeterol (Sal) alone versus FP plus Sal (FPS) on RSV-induced airway inflammation. Mice were sensitized and challenged with ovalbumin (OVA) and infected with RSV. Following infection they were treated with FP, Sal, or FPS intranasally and airway hyperreactivity (AHR), inflammation and RSV titers were examined.

RESULTS

The group treated with FPS showed significantly lower AHR compared to the group treated with FP or Sal alone. The group treated with FP alone showed slightly decreased (non-significant) AHR compared to controls. Treatment with FPS resulted in significant decreases in the percentage of eosinophils and neutrophils in bronchoalveolar lavage fluid and in lung pathology compared to FP or Sal. FP alone decreased eosinophils but not neutrophils or lymphocytes, while Sal alone decreased eosinophils and neutrophils but not lymphocytes. FPS treatment of mice infected with RSV in the absence of allergen sensitization resulted in a 50% decrease of RSV titer in the lung and a reduction in neutrophils compared to FP or Sal.

CONCLUSION

Together, these results indicate that fluticasone in combination with salmeterol is a more effective treatment for decreasing airway hyperreactivity and inflammation than either of them alone in allergen-sensitized, RSV-infected mice.

Pathogenesis of respiratory syncytial virus infection in the murine model

There is a wide spectrum of illness caused by respiratory syncytial virus (RSV) infection that is caused in large part by host-related factors, such as age of the patient and degree of host immunocompetency. Although the vast majority of persons infected with RSV experience symptoms of mild upper respiratory tract infection, in some people these infections cause significant morbidity and are sometimes fatal. Although a great deal of investigation in both humans and animals has explained the timing and tropism of RSV infection and the general principles by which the immune system responds to this infection, at present we only partially understand the disparity in illness severity that can occur. This article briefly reviews the clinical sequelae of RSV infection and then focuses on the mechanisms of viral pathogenesis.

Is influenza vaccination in asthmatic children helpful?

The rationale for influenza vaccination in asthmatic children theoretically lies in prevention of exacerbations and serious complications like pneumonia. Solid evidence from randomized clinical trials of its preventive effects on these clinical endpoints is, however, lacking. Nevertheless, most Western guidelines advise to vaccinate these children. In the real life situation this advice isn't very well followed: vaccine coverage for this indication is low. To assess the usefulness of influenza vaccination in children with asthma a set of fundamental questions regarding this activity is presented and answered. This leads to the conclusion that, given the evidence, influenza vaccination in children with mild to moderate disease should be reconsidered.

Increased proinflammatory responses from asthmatic human airway smooth muscle cells in response to rhinovirus infection

Background

Exacerbations of asthma are associated with viral respiratory tract infections, of which rhinoviruses (RV) are the predominant virus type. Airway smooth muscle is important in asthma pathogenesis, however little is known about the potential interaction of RV and human airway smooth muscle cells (HASM). We hypothesised that rhinovirus induction of inflammatory cytokine release from airway smooth muscle is augmented and differentially regulated in asthmatic compared to normal HASM cells.

Methods

HASM cells, isolated from either asthmatic or non-asthmatic subjects, were infected with rhinovirus. Cytokine production was assayed by ELISA, ICAM-1 cell surface expression was assessed by FACS, and the transcription regulation of IL-6 was measured by luciferase activity.

Results

RV-induced IL-6 release was significantly greater in HASM cells derived from asthmatic subjects compared to non-asthmatic subjects. This response was RV specific, as 5% serum- induced IL-6 release was not different in the two cell types. Whilst serum stimulated IL-8 production in cells from both subject groups, RV induced IL-8 production in only asthmatic derived HASM cells. The transcriptional induction of IL-6 was differentially regulated via C/EBP in the asthmatic and NF-κB + AP-1 in the non-asthmatic HASM cells.

Conclusion

This study demonstrates augmentation and differential transcriptional regulation of RV specific innate immune response in HASM cells derived from asthmatic and non-asthmatics, and may give valuable insight into the mechanisms of RV-induced asthma exacerbations.

Asthma during the primary school ages--prevalence, remission and the impact of allergic sensitization

BACKGROUND

Childhood is the most important time for asthma development. The aims of this study were to study changes in prevalence of asthma and wheeze, remission of asthma and changes in risk factor pattern from age 7-8 to age 11-12 in a cohort of school children.

METHODS

In 1996, 3525 children aged 7-8 years in northern Sweden were invited to participate in a parental expanded ISAAC questionnaire survey. The cohort has been followed prospectively with yearly follow-ups to age 11-12, with a 97% yearly response rate. Skin prick tests were conducted at age 7-8 and 11-12.

RESULTS

The prevalence of physician-diagnosed asthma increased from 5.7% at age 7-8 to 7.7% at age 11-12. Life-time prevalence of wheeze was 34.7% at age 11-12. The remission of asthma was 10% yearly and inversely related to allergic sensitization. Relapses were common, and remission persisting throughout the observation period was 5% yearly. Allergic sensitization was associated with current asthma at age 7-8 [adjusted odds ratio (OR) 4.9 (95% confidence interval (CI) 3.3-7.3)] and when the children were 4 years older [OR 5.6 (3.9-8.2)]. A family history of asthma was associated with current asthma at age 7-8 [OR 3.0 (2.1-4.5)] and 11-12 (OR 2.8 [2.0-3.9]). Ever having lived with a cat was significantly negatively associated with current asthma.

CONCLUSIONS

The prevalence of asthma increased continuously during the primary school ages. Among several significant risk factors, allergic sensitization and a family history of asthma were the most important. With increasing age many known risk factors lost significance. Remission was inversely related to allergic sensitization.

The relationship of rhinovirus-associated asthma hospitalizations with inhaled corticosteroids and smoking

BackgroundAlthough rhinovirus (RV) respiratory infections trigger asthma exacerbations, the etiologic association between this virus and severe exacerbations, as well as the clinical characteristics of adults at risk for RV-associated asthma that necessitates hospitalization, have not been established

MethodsDuring 1999–2003, we conducted a cohort study of 101 adults prospectively enrolled at hospital admission for an asthma exacerbation. Patient characteristics and frequencies of RV in nasal specimens were analyzed, by reverse-transcription polymerase chain reaction (RT-PCR), at asthma-related hospital admission and at a 3-month convalescent follow-up visit

ResultsRV was detected by RT-PCR in 21% of hospitalized patients over a 4-year period and in 1.3% of patients who returned for a 3-month follow-up visit. RV detection was strongly associated with hospitalization for asthma (adjusted odds ratio [OR], 15.1 [95% confidence interval {CI}, 1.88–121.4]). After adjustment for baseline asthma severity, RV-positive patients were more likely than RV-negative patients to be current smokers and nonusers of inhaled corticosteroids (ICSs) (adjusted OR, 11.18 [95% CI, 2.37–52.81]; P=.002)

ConclusionsRV respiratory infection is an etiologic agent in severe asthma exacerbations necessitating hospitalization in adults. Compared with hospitalized patients with asthma who were RV negative, RV-positive patients were significantly more likely to be smokers and nonusers of ICSs

Indoor environmental exposures among children with asthma seen in an urban emergency department

BACKGROUND

Current guidelines for asthma management emphasize the control of environmental irritants and allergens within the home. Understanding the prevalence of indoor home exposures within such a population may be important for any emergency department (ED) program that seeks to improve the quality of its asthma care and patient education.

OBJECTIVE

We sought to determine the prevalence of indoor home exposures in a cohort of children with moderate to severe asthma who were treated in an urban pediatric ED and to correlate these exposures with household income, prior asthma morbidity, health care utilization, and quality of life (QoL).

METHODS

We enrolled a cohort of children with chronic asthma who were 12 months through 17 years of age and who had at least one other unscheduled visit for asthma within the previous 6 months. Trained research assistants interviewed the children's parent or guardian regarding the prevalence of home exposures to environmental tobacco smoke (ETS) and common allergens. In addition, data were collected on each patient's prior asthma history, morbidity, health care utilization, medication use, and QoL.

RESULTS

Of the 488 eligible children enrolled, 60.0% were <6 years of age, 63.9% were male, 85.9% were black, 68.4% were publicly insured, and 51.8% had >3 ED visits in the previous 12 months. Home exposure to ETS and potential allergens was high. Exposure to cockroach allergen was significantly associated with household income. Coexistence of exposures was common: significantly more patients reporting ETS exposure also reported exposure to cockroach allergen and mold than those not reporting ETS exposure. Poorer QoL was significantly associated with cockroach exposure, although this effect was limited to those also exposed to ETS. Higher rates of unscheduled health care utilization and persistent asthma symptoms were not associated with exposures.

CONCLUSION

Additional investigation is necessary to clarify the role of exposure-avoidance measures as a component of ED-based interventions for asthma care.

Day-care attendance and increased risk for respiratory and allergic symptoms in preschool age

BACKGROUND

The reported impact of day-care attendance on respiratory and atopic symptoms has varied between studies from different countries. Regarding to the 'hygiene-hypothesis', day-care attendance may lead to less sensitization later in life, but the question still is whether day-care attendance and subsequent exposure to more frequent early infections is a risk or a protection against future allergic disease or asthma (atopic and nonatopic).

METHODS

A cross-sectional postal questionnaire was replied by parents of 10,851 children, aged 1-6 years, in the year 2000 in a Swedish region (DBH-phase 1). The questionnaire focused on respiratory and atopic symptoms, the home environment and information on day care of the children.

RESULTS

Children in day care were reported to have more symptoms than children in home care: adjusted odds ratio (AOR) for wheezing last 12 months, AOR 1.33 (CI 95%: 1.12-1.58), cough at night apart from colds last 12 months AOR 1.56 (CI: 1.17-2.07), doctor diagnosed asthma AOR 1.23 (CI: 0.88-1.71), rhinitis last 12 months AOR 1.15 (CI: 0.92-1.44), doctor diagnosed hay fever AOR 1.75 (CI: 0.94-3.23), eczema last 12 months, AOR 1.49 (CI: 1.24-1.79), allergic reactions to foods, AOR 1.27 (CI: 1.07-1.52), >6 colds last 12 months of 2.57 (CI: 2.12-3.12) and ear infection ever AOR 2.14 (CI: 1.87-2.45). The increased risks were mainly seen and reached significance in the youngest group of children, aged 1-4 years. Adjusting and stratification for the number of airway infections last year did not change the risk associated with day-care attendance for allergic diseases.

CONCLUSIONS

Attending day care was associated with an increased risk of symptoms related to airways infections as well with eczema and allergic reactions to food. No sign of protection from day-care attendance for allergic diseases was found up to 6 years of age. Multiple airway infections and day-care attendance were found to be independently associated with asthma and allergic symptoms.

Vascular endothelial growth factor-mediated induction of angiogenesis by human rhinoviruses

BACKGROUND

Human rhinoviruses, major precipitants of asthma exacerbations, infect the lower airway epithelium inducing inflammation. The possibility that viral infection may mediate angiogenesis, thus contributing to airway remodeling, has not been evaluated.

OBJECTIVE

To investigate whether epithelial infection with rhinovirus mediates angiogenesis in vitro, evaluate possible modulation by an atopic environment, and confirm angiogenic factor induction after in vivo rhinovirus infection.

METHODS

Bronchial epithelial cells were infected with rhinovirus and levels of vascular endothelial growth factor (VEGF), and angiopoietins were measured. The angiogenic effect of epithelial products was assessed in in vitro models of angiogenesis. PBMCs, obtained from patients with atopic asthma and normal controls, were exposed to rhinovirus; the ability of supernatants from these cultures differentially to affect rhinovirus-mediated epithelial VEGF production was evaluated. VEGF levels were measured in respiratory secretions from patients with asthma, before and during rhinovirus-induced exacerbations.

RESULTS

Epithelial infection with rhinovirus specifically stimulated mRNA expression and release of VEGF, but not angiopoietins, in a time-dependent and dose-dependent manner. Supernatants from these cultures were able to induce angiogenesis in vitro, significantly inhibited by a neutralizing anti-VEGF antibody. When bronchial cells were exposed to supernatants of rhinovirus-infected mononuclear cells from normal subjects or atopic patients with asthma, VEGF induction was significantly higher under the influence of the atopic environment. VEGF was elevated during rhinovirus-associated asthma exacerbations.

CONCLUSION

Rhinovirus infection, a frequent event, induces VEGF production in bronchial epithelial cells and human airways, an effect enhanced in an atopic environment. Rhinovirus-associated, VEGF-mediated angiogenesis may contribute to airway remodeling in asthma.

Temporal associations between daily counts of fungal spores and asthma exacerbations

BACKGROUND

Outdoor aeroallergens are one of a number of environmental factors thought to precipitate asthma exacerbations.

AIMS

To investigate the short term associations between daily fungal spore concentrations and indicators of daily asthma exacerbations in a large urban population.

METHODS

Daily counts of visits for asthma to family physicians and hospital accident and emergency (A&E) departments and emergency hospital admissions in London 1992-93 were compiled. Daily concentrations of fungal spores (30 species), daily average temperature, humidity, and concentrations of pollen and outdoor air pollution were also compiled. The analysis was restricted to the period when fungal spores were most prevalent (June to mid October). Non-parametric regression time series methods were used to assess associations controlling for seasonality, day of week, and meteorological factors. The sensitivity of the findings to the inclusion of pollen and air pollution into the models was also assessed.

RESULTS

In children aged 0-14 years the relative risks for increases in the number of A&E visits and hospital admissions associated with changes in fungal spore concentrations from the lower to upper quartiles were 1.06 (95% CI 0.94 to 1.18) and 1.07 (0.97 to 1.19) respectively. The addition of pollen or air pollutants had little impact on the observed associations. A number of individual spore taxa, in particular Alternaria, Epicoccum, Agrocybe, Mildews, and both coloured and colourless Basidiospores and Ascospores, were associated with increases in the number of emergency visits and hospital admissions for asthma, although the precision of these estimates were low. No evidence was found for associations in adults.

CONCLUSIONS

Fungal spore concentrations may provoke or exacerbate asthma attacks in children resulting in visits to A&E departments and emergency hospital admissions. These findings were unlikely to be due to confounding by other environmental factors. The associations were comparable to those observed for ambient air pollution from similarly designed studies.

Pathogenic bacteria and viruses in induced sputum or pharyngeal secretions of adults with stable asthma

BACKGROUND

Respiratory infections are well known triggers of asthma exacerbations, but their role in stable adult asthma remains unclear.

METHODS

103 asthmatics and 30 control subjects were enrolled in the study. Sputum was induced by inhalation of 3% NaCl solution. Oropharyngeal swab specimens were obtained from the posterior wall of the oropharynx. Respiratory specimens were analysed by RT-PCR for rhinovirus, enterovirus and respiratory syncytial virus and by PCR for adenovirus, Chlamydia pneumoniae, Mycoplasma pneumoniae and Bordetella pertussis.

RESULTS

Sputum samples from two of the 30 healthy controls (6.7%), five of 53 patients with mild asthma (9.4%), and eight of 50 with moderate asthma (16.0%) were positive for rhinovirus. Rhinovirus positive asthmatic subjects had more asthma symptoms and lower forced expiratory volume in 1 second (FEV(1)) (79% predicted) than rhinovirus negative cases (93.5% predicted; p = 0.020). Chlamydia pneumoniae PCR was positive in 11 healthy controls (36.6%), 11 mild asthmatics (20.8%), and 11 moderate asthmatics (22%), and PCR positive asthmatics had lower FEV(1)/FVC than negative cases (78.2% v 80.8%, p = 0.023). Bordetella pertussis PCR was positive in 30 cases: five healthy controls (16.7%), 15 mild asthmatics (28.3%), and 10 moderate asthmatics (20%). Bordetella pertussis positive individuals had lower FEV(1)/FVC (77.1% v 80.7%, p = 0.012) and more asthma symptoms than B pertussis negative cases.

CONCLUSIONS

Rhinovirus, C pneumoniae, and B pertussis are found in the sputum or pharyngeal swab specimens of asthmatic subjects without concurrent symptoms of infection or asthma exacerbation, as well as in some healthy controls. Positivity is associated with lower lung function and more frequent asthma symptoms.

The role of the respiratory syncytial virus in airway syndromes in childhood

The majority of infants admitted to hospital in infancy with lower respiratory tract infections (LRTIs) have been infected with the respiratory syncytial virus (RSV). Infants and young children experiencing RSV LRTIs experience increased respiratory morbidity in subsequent years, although the prevalence falls rapidly in early childhood. Recent data support the suggestion that in most subjects, this recurrent morbidity is not attributable to atopic asthma and that in most respects, the acute and long-term outcomes with RSV infections are similar in nature to those attributable to other viruses. The phenotype of the acute illness probably provides better prognostic information than the type of virus.

Guidelines for evaluating chronic cough in pediatrics: ACCP evidence-based clinical practice guidelines

OBJECTIVES

To review relevant literature and present evidence-based guidelines to assist general and specialist medical practitioners in the evaluation and management of children who present with chronic cough.

METHODOLOGY

The Cochrane, MEDLINE, and EMBASE databases, review articles, and reference lists of relevant articles were searched and reviewed by a single author. The date of the last comprehensive search was December 5, 2003, and that of the Cochrane database was November 7, 2004. The authors' own databases and expertise identified additional articles.

RESULTS/CONCLUSIONS

Pediatric chronic cough (ie, cough in children aged <15 years) is defined as a daily cough lasting for >4 weeks. This time frame was chosen based on the natural history of URTIs in children and differs from the definition of chronic cough in adults. In this guideline, only chronic cough will be discussed. Chronic cough is subdivided into specific cough (ie, cough associated with other symptoms and signs suggestive of an associated or underlying problem) and nonspecific cough (ie, dry cough in the absence of an identifiable respiratory disease of known etiology). The majority of this section focuses on nonspecific cough, as specific cough encompasses the entire spectrum of pediatric pulmonology. A review of the literature revealed few randomized controlled trials for treatment of nonspecific cough. Management guidelines are summarized in two pathways. Recommendations are derived from a systematic review of the literature and were integrated with expert opinion. They are a general guideline only, do not substitute for sound clinical judgment, and are not intended to be used as a protocol for the management of all children with a coughing illness. Children (aged <15 years) with cough should be managed according to child-specific guidelines, which differ from those for adults as the etiologic factors and treatments for children are sometimes different from those for adults. Cough in children should be treated based on etiology, and there is no evidence for using medications for the symptomatic relief of cough. If medications are used, it is imperative that the children are followed up and therapy with the medications stopped if there is no effect on the cough within an expected time frame. An evaluation of the time to response is important. Irrespective of diagnosis, environmental influences and parental expectations should be discussed and managed accordingly. Cough often impacts the quality of life of both children and parents, and the exploration of parental expectations and fears is often valuable in the management of cough in children.