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

[Epidemiology of viral infection and asthma]

The first epidemiological data concerning viruses and asthma were obtained in the 1970s and 1980s by viral isolation and serology. Viral infection can be identified in 24 % to 31.9 % of children, and in 13.3 % of adults. The three most frequent viruses are rhinovirus (RV), respiratory syncytial virus (RSV), and parainfluenza viruses (PIV), detected in 8.8 %, 6.4 % and 6 % of cases, respectively. Due to its amplifying properties, the use of PCR increases the frequency of viral detection, and appears particularly appropriate in asthma where the viral load can be reduced. In a study of bronchiolitis, RSV, PIV3, AdV and RV were identified in 39.3 %, 4.3 %, 1.4 % and 3.9 % of cases, respectively, by IF or culture, and in 62.4 %, 8.3 %, 10.8 % and 12.6 % of cases, respectively, by PCR. Two recent epidemiological surveys used molecular diagnosis in asthma attacks. In a series of 61 adults, 27 (44 %) infections were identified: 16 RV, 4 CV OC43, 3 PIV, 1 RSV, 1 VI, 1 Chlamydia psitacci. In children, viral infection was detected in 226 cases (77 %) : 84 RV, 38 CV, 21 IV, 21 PIV, 12 RSV. We have performed a short retrospective survey for 1997, using molecular biology, on 39 nasal aspirates from children consulting for asthma or wheezing bronchitis. Testing for respiratory viruses by conventional techniques identified 8 (20.5 %) viral infections: 3 RV, 3 RSV, 1 IBV and 1 VPI2. After nucleic acid extraction, PCR-hybridization techniques were applied to these samples to detect RSV, AdV, RV, CV 229E, CV OC43, CP and MP sequences. Twenty six aspirates (54 %) were positive only on molecular biology techniques: 11 RSV, 12 RV, 2 enterovirus, 1 CV OC43. Overall 34 (82 %) viral infections were detected in these children, and a mixed RSV-RV infection was identified in 6 cases. Compared to the studies reported in the literature, we observed the same predominance of RV infections, more RSV infections, probably related to the use of PCR, and a lower incidence of CV infections.

Interleukin-10 gene expression in acute virus-induced asthma

RATIONALE

Virus-induced asthma is characterized by marked neutrophil influx and eosinophil degranulation, suggesting a mode of immunopathogenesis different from that of allergen-induced asthma.

OBJECTIVES

This study compared induced sputum cytokine responses in subjects with severe asthma exacerbation and respiratory virus infection with those of patients with stable asthma, healthy control subjects, and virus-infected nonasthmatic subjects.

METHODS

Subject infection status and pulmonary history were established on the basis of common cold and asthma questionnaires, and lung function and atopy tests were performed. Respiratory virus infection was diagnosed by cell culture and direct polymerase chain reaction, using induced sputum. The induced sputum cellular profile was examined and cytokine gene expression was assessed by quantitative real-time polymerase chain reaction.

RESULTS

A respiratory virus was detected in 78% of subjects with acute asthma. Specific viruses detected were rhinovirus (83%), influenza (15%), enterovirus (4%), and respiratory syncytial virus (2%). Virus-infected subjects with acute asthma or no asthma had increased RANTES (regulated on activation, normal T cell expressed and secreted) and macrophage inflammatory protein-1alpha messenger RNAs compared with other groups. Interleukin (IL)-10 mRNA was significantly increased in virus-infected acute asthma and reduced on recovery from acute asthma. IL-5, eotaxin, and IL-8 mRNA transcripts were similar across groups.

CONCLUSIONS

Asthma exacerbation triggered by respiratory virus infection is characterized by increased IL-10 gene expression that may explain the suppressed eosinophil influx in acute asthma. Airway neutrophilia due to respiratory virus infection is associated with chemokine gene expression involving RANTES and macrophage inflammatory protein-1alpha.

Influence of viral infection on the development of nasal hypersensitivity

BACKGROUND

The underlying relationship between viral infections and allergic diseases of the upper respiratory tract has not been well clarified.

METHODS

In order to clarify the relationship between viral infection and nasal hypersensitivity, mice were sensitized with ovalbumin (OVA) and then infected intranasally with respiratory syncytial virus (RSV), after which their nasal sensitivity to histamine or antigen was examined.

RESULTS

Non-sensitized mice showed transient mild nasal hypersensitivity following nasal administration of histamine after intranasal RSV inoculation. In mice sensitized with OVA, RSV infection significantly exaggerated their nasal hypersensitivity to histamine and OVA. Treatment of these mice with a neurokinin (NK)-1/NK-2 receptor antagonist, but not with anti-IL-5 antibodies, reduced their hypersensitivity. The infiltration of nasal mucosa with eosinophils was temporarily associated with accelerated rate of RSV elimination in these animals.

CONCLUSION

RSV infection induced transient nasal hypersensitivity. Several mechanisms, including impairment of nasal epithelial cells are thought to mediate this effect. In allergen-sensitized mice, RSV inoculation strongly enhanced nasal hypersensitivity.

Analysis of tracheal secretions for rhinovirus during natural colds

Rhinoviruses (RV) cause 50% of common colds and are frequently isolated from children and adults hospitalized for asthma exacerbations. Although colds may trigger severe coughing and wheezing, it is not known whether these symptoms are a result of lower airway infection with RV. Previous efforts to address this question by sampling lower airway secretions during experimental RV infections have been complicated by the possibility of contamination of the bronchoscope with nasopharyngeal cells and secretions. To further test the hypothesis that RV infections involve the lower airways, tracheal and nasal secretions were obtained from 23 pediatric tracheostomy patients, including seven with cold symptoms and 16 asymptomatic controls. RV was detected by reverse-transcription polymerase chain reaction from the nasal and tracheal secretions of three of the seven children with cold symptoms. In the 16 well children, RV was not detected in any samples of nasal secretions, but was isolated from four samples of tracheal secretions. These results demonstrate the presence of RV in the lower airways of children with tracheostomies during community-acquired colds, without the possibility of nasal contamination. In addition, these findings suggest that children with tracheostomies carry subclinical viral infections in their tracheas, rather than their noses.

What is the contribution of respiratory viruses and lung proteases to airway remodelling in asthma and chronic obstructive pulmonary disease?

It is well known that the lungs of asthmatics show airway wall remodelling and that asthma exacerbations are linked to respiratory infections. There is some evidence that respiratory infections in early childhood may increase the risk of developing asthma later in life. Chronic obstructive pulmonary disease (COPD), by definition, involves structural changes to the airways. However, very little is known about what role virus infections play in the development of this remodelling. This review considers the role of matrix metalloproteases and neutrophil elastase in remodelling, and whether the induction of proteases and other mediators during respiratory virus infections may contribute to the development of airway remodelling.

Detection of human picornaviruses by multiplex reverse transcription-PCR and liquid hybridization

A qualitative multiplex reverse transcription (RT)-PCR and liquid hybridization assay for the detection of human enteroviruses, rhinoviruses, parechoviruses, and Aichi virus was developed. Furthermore, a separate assay for the recognition of hepatitis A virus was established to complement the test pattern so that all human picornaviruses were covered. The amplicons, which represented the 5' untranslated regions of the viral RNA genomes, were identified in liquid hybridization reactions with genus-specific digoxigenin-labeled oligonucleotide probes. The sensitivity of the multiplex RT-PCR and liquid hybridization assay was 10 to 100 picornavirus genome equivalents for representatives of each picornavirus genus. The hepatitis A virus assay exhibited a sensitivity of 10 genome copies. Both the uniplex and the multiplex tests were highly specific for the target viruses. Twenty-three clinical samples, including cerebrospinal fluid, serum, and nasopharyngeal swab specimens, were used for clinical evaluation of the multiplex RT-PCR assay. The results obtained were consistent with the results of routine virus diagnostic assays. Furthermore, the assay was used to screen 68 stool specimens for the presence of parechoviruses and Aichi virus. One sample was found to contain parechovirus RNA, whereas no Aichi virus was detected. The assay described here can be applied for the efficient identification of human enteroviruses and rhinoviruses in clinical specimens and simultaneously enables the collection of information on the epidemiology and clinical outcomes of infections caused by the currently poorly known human parechoviruses and Aichi virus.

Viruses in asthma exacerbations

PURPOSE OF REVIEW

Respiratory viruses are well recognized as major triggers of acute exacerbations of asthma in children and adults, resulting in frequent outpatients visits and hospitalizations. Clinical and epidemiologic evidence supports this association. The application of molecular diagnostic methods has improved understanding of viral epidemiology and the pathophysiological mechanisms involved in viral induced acute asthma. This article reviews publications since October 2002 for an update of the role of viruses in exacerbations of asthma.

RECENT FINDINGS

Respiratory viruses are present in most patients hospitalized for life-threatening asthma and acute non life-threatening asthma. Rhinovirus is the most common, but coinfection with other viruses may be important. Patients with asthma are not more susceptible to upper respiratory tract rhinovirus infections than healthy people but suffer from more severe consequences of the lower respiratory tract infection. Recent epidemiologic studies suggest that viruses provoke asthma attacks by additive or synergistic interactions with allergen exposure or with air pollution. An impaired antiviral immunity to rhinovirus may lead to impaired viral clearance and hence prolonged symptoms. Respiratory viral infections cause asthmatic exacerbations by triggering recruitment of Th2-type cells into the lungs. There is no specific antiviral strategy for prevention of respiratory-triggered asthma exacerbations, although clinical trials of potential antiviral agents are ongoing. Indirect prevention strategies focus on the reduction of overall airway inflammation to reduce the severity of the host response to respiratory viral infections.

SUMMARY

Respiratory viral infections are a major cause of morbidity and mortality in asthma. There is a lack of specific antiviral strategies in the prevention or reduction of viral-triggered asthma exacerbations. Recent advances in understanding of the epidemiology and immunopathogenesis of respiratory viral infection in asthma provide opportunities or identification of specific targets for antiviral agents and strategies for management and prevention.

Infectious triggers of asthma

There is abundant evidence that asthma is frequently exacerbated by infectious agents. Several viruses have been implicated in the inception and exacerbation of asthma. Recent attention has been directed at the role of infections with the atypical bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae as agents capable of triggering asthma exacerbations and potentially as inciting agents for asthma. This article examines the evidence for interaction between specific infectious agents and exacerbations of asthma, including the immunopathology of infection-triggered asthma, and the current therapeutic options for management.

Acute and chronic cough

Individuals are generally content to self-medicate for acute cough. It is only when the cough becomes persistent that they seek medical assistance. It is not known why patients cough in association with an acute upper respiratory tract infection (URTI), although interest has focused on how viruses may influence airway sensory nerve function and contribute to heightened cough reflex sensitivity. Why some patients develop a persistent cough following a viral URTI is also unclear. Much more is known about the causes and aggravants of chronic cough although there is no broad agreement as to the best way to manage such patients. Asthma, upper gastrointestinal dysfunction and rhinitis are frequently associated with chronic cough, although the impact of cough in suppurative lung disease and interstitial lung fibrosis is rarely considered. The development of effective treatments for cough remains a challenge and will require co-operation between clinicians, scientists and the pharmaceutical industry.

Pathophysiology of airway viral infections

Viral infections are major causes of cough. Virus-induced changes in airway sensory nerve function include increased tachykinin expression and, more specifically, expression of tachykinins by Adelta fibers. This change may be mediated by neurotrophins produced in response to viral infection. At the same time, activity of neutral endopeptidase, an enzyme that is important in degrading and inactivating tachykinins, is decreased by airway viral infections. Viral infections can activate eosinophils, releasing proteins that can cause tachykinin release. Moreover, expression of the NK1 receptor is increased by viral infections of the lungs. The expression of M2 muscarinic receptors, which normally decrease the sensitivity of sensory nerves, is decreased by viral infections. So it is possible that viral infections (1) increase expression of tachykinins (by causing neurotrophin expression), (2) increase release of tachykinins (by causing release of eosinophil proteins), (3) decrease degradation of tachykinins (by decreasing neutral endopeptidase activity), (4) increase expression of the NK1 receptor (again mediated by neurotrophins), and (5) increase the sensitivity of airway afferents (by decreasing M2 muscarinic receptor expression). All these changes may potentiate the tachykininergic input into the cough reflex, and may provide new therapeutic targets for controlling virus-induced cough.

Oral oseltamivir improves pulmonary function and reduces exacerbation frequency for influenza-infected children with asthma

BACKGROUND

Among asthmatic children, influenza is associated with increased hospitalizations. Although vaccination is safe and effective among asthmatic children, its protective efficacy varies and uptake rates can be low. In comparison, oseltamivir (Tamiflu) is effective against all influenza strains and can reduce the severity and duration of influenza among adults and children. This study determined the effects of oseltamivir among influenza-infected children with asthma.

METHODS

Asthmatic children (6-12 years of age) were randomized to receive oseltamivir (2 mg/kg) or placebo twice daily, as a syrup. The primary efficacy endpoint was the time to freedom from illness. Secondary endpoints included the area under the symptom score-hour curve, the proportion of patients with asthma exacerbations and changes in forced expiratory volume at 1 second during the dosing period. Analysis was performed for both the intent-to-treat infected (n = 179) and per protocol (n = 162) populations.

RESULTS

The primary endpoint for this study was not met. Oseltamivir tended to reduce the time to freedom from illness in the intent-to-treat infected population (10.4 hours, 8%; P = 0.5420), the per protocol population (24.3 hours, 17%; P = 0.1607) and patients who started treatment <24 hours after symptom onset (39.8 hours, 25%; P = 0.0780). However, an improvement in pulmonary function was observed. The improvement in forced expiratory volume at 1 second was significantly greater among oseltamivir-treated patients (10.8% versus 4.7%; P = 0.0148). Oseltamivir-treated patients also experienced fewer asthma exacerbations up to day 7 (68% versus 51%; P = 0.031). Oseltamivir was safe and well-tolerated.

CONCLUSIONS

Oseltamivir is safe and well-tolerated among asthmatic children, may reduce symptom duration and helps improve lung function and reduce asthma exacerbations during influenza infection.

The need for standardisation of peak flow charts

Peak expiratory flow (PEF) monitoring is recommended in asthma guidelines as a tool for assessing severity, monitoring response to treatment, detecting exacerbations, identifying triggers, and providing objective justification for treatment to the patient, but some clinicians have expressed concerns about its relevance in the management of asthma. We have identified a sevenfold variation in the scale of existing PEF charts, with resulting wide variation in the appearance of the same PEF date on different charts. There is an obvious need for standardisation of PEF charts to avoid confusion for patients and to allow development of pattern recognition skills by clinicians. Evidence is provided from visual perception studies to suggest that preference should be given to a horizontally compressed PEF chart to facilitate identification of exacerbations and of overall trends, but this needs to be formally evaluated by retrospective and prospective studies. It is hoped that clinical expertise in PEF pattern recognition can eventually be incorporated into electronic decision making algorithms, as has occurred in occupational asthma, but, in the meantime, the ideal PEF chart for asthma management will represent a compromise between ease of manual data entry and ease of interpretation.

Montelukast Reduces Asthma Exacerbations in 2- to 5-Year-Old Children with Intermittent Asthma

The PREVIA study was designed to investigate the role of montelukast, a leukotriene receptor antagonist, in the prevention of viral-induced asthma exacerbations in children aged 2 to 5 years with a history of intermittent asthma symptoms. The study was a 12-month multicenter, double-blind, parallel-group study of patients with asthma exacerbations associated with respiratory infections and minimal symptoms between episodes. Patients were randomized to receive oral montelukast 4 or 5 mg (depending on age) (n = 278) or placebo (n = 271) once per day for 12 months. Caregivers recorded children's symptoms, beta-agonist use, and health care resource use in a diary card. Over 12 months of therapy, montelukast significantly reduced the rate of asthma exacerbations by 31.9% compared with placebo. The average rate of exacerbation episodes per patient was 1.60 episodes per year on montelukast compared with 2.34 episodes on placebo. Montelukast also delayed the median time to first exacerbation by approximately 2 months (p = 0.024), and the rate of inhaled corticosteroid courses (p = 0.027) compared with placebo. Montelukast effectively reduced asthma exacerbations in 2- to 5-year-old patients with intermittent asthma over 12 months of treatment and was generally well tolerated.

Practical implementation of a multiplex PCR for acute respiratory tract infections in children

Molecular testing for acute respiratory infections (ARIs) has documented value but limited implementation due to questions that typically slow the acceptance of new tests. This study sought to address these questions and achieve implementation. Rhinovirus was added to a nested multiplex PCR (M-PCR), increasing its diagnostic yield. Over one winter, three hospital pediatric departments used the M-PCR to complement their direct fluorescent-antibody assay (DFA) for respiratory syncytial virus (RSV). Clinicians recorded "pretest probability estimates" (using continuous scales for various pathogen groups) for comparison with test results; treatments and test turnaround times were also recorded. Transnasal and throat swabs, with or without nasopharyngeal aspirate (NPA), were M-PCR tested. NPA-containing sample sets found to be RSV positive by DFA were not further tested. Single PCR for human metapneumovirus (hMPV) was performed retrospectively. Of 178 ARI episodes representing 172 patients, NPA was included in 97 sample sets; 54 (56%) were determined to be RSV positive. The other NPA-containing sample sets (n = 43) yielded 27 findings (63%), and the swab-only sets (n = 81) yielded 47 findings (58%); rhinovirus was found most often. Testing for hMPV yielded seven positive results. M-PCR median turnaround times were 4 days in swab-only samples and 5 days with NPA. Antibiotics were prescribed in 50 episodes, at rates similar for RSV and rhinovirus. Pretest probability estimates of a viral cause were lower in episodes caused by rhinovirus than in episodes caused by RSV. The hospitals continued to use M-PCR for NPA-containing samples found to be RSV negative by DFA. Test implementation is more likely with higher diagnostic yield and a protocol that reflects day-to-day clinical and laboratory operations.

Respiratory infections and asthma: current treatment strategies

Infections such as lower respiratory illness potentially contribute to the initiation of asthma and are major factors in recurring acute exacerbations of the condition. Although typical bacterial respiratory pathogens such as Streptococcus pyogenes, Streptococcus pneumoniae and Hemophilus influenzae do not initiate asthmatic exacerbations, data from a subgroup of adults suggest a potential role for Mycoplasma pneumoniae and Chlamydia pneumoniae in the onset of asthma. Common cold viruses, predominantly respiratory syncytial virus (RSV) in young children and rhinoviruses in older children and adults, are the major causes of acute exacerbations of asthma. These exacerbations are not prevented with maintenance therapies that are used for chronic asthma, but do respond to short courses of systemic corticosteroids. There are continued attempts to produce a successful vaccine and antiviral agents for the treatment of RSV that are more effective and more practical to use than ribavirin, which is currently the only available antiviral for RSV. The prevention and treatment of rhinovirus infections have focused on the major receptor for the virus, intercellular adhesion molecule-1 (ICAM-1), which is located on respiratory epithelial cells. A multivalent, recombinant, antibody fusion protein identified as CFY196 has high avidity for ICAM-1 and has the potential to protect against rhinovirus infection. Another approach for preventing and treating rhinovirus infection uses a recombinant, soluble, truncated form of ICAM-1 in which the transmembrane and intracellular domains of the protein have been deleted. An initial clinical study on this agent demonstrated clinical efficacy in ameliorating the symptoms of experimental rhinovirus infection in volunteers, but did not significantly prevent infection.

Inflammatory events in severe acute asthma

Severe acute asthma can be induced by different triggers, allergens, irritants, viruses, etc., which induce inflammation and provoke acute bronchoconstriction. Inflammatory cells, such as activated eosinophils and neutrophils identified in sputum and bronchial lavages (BL) in severe acute asthma from children and adults are associated with increased levels of IL-5, IL-8, and of proinflammatory mediators. Viruses, but also endotoxin or allergen exposure, are able to recruit neutrophils, via an IL-8 production by activated macrophages or epithelial cells. Together, these inflammatory mediators are responsible for the diffuse bronchial inflammation, which involve large and small airways. Activated T cells may also be related to the pathogenesis of severe asthma. An aberrant CD8+ T lymphocyte response in bronchi, with a cytotoxic activity has been associated with fatal asthma. Moreover, the persistence of inflammatory cells in bronchi, particularly neutrophils, which respond poorly to corticosteroids, could be in part responsible for the epithelial damage, the extensive mucus plugging, and the abnormalities of epithelial and endothelial permeability which are associated with severe acute asthma. Further studies are necessary to better identify the implication of this increased bronchial permeability in the persistence of high levels of airway resistance, particularly in patients with status asthmaticus.

On roots of childhood asthma: the role of respiratory infections

The prevalence of childhood asthma has increased throughout the last decades, but the reasons for the increase still remain unresolved. However, the debate has recently focused on the role of infections, and microbial exposure in general, in the development of childhood asthma. Many studies have suggested that there is an inverse relation between certain infections and the risk of asthma. This article outlines the contemporary role of childhood asthma in public health, reviews the importance of topical respiratory pathogens in the development of childhood asthma, and provides an example how selection bias may have caused controversy in previous studies assessing the role of infections in the development of childhood asthma.

New considerations in the treatment and prevention of rhinovirus infections

Rhinoviruses are a very common cause of infections in children. Although these infections are most closely associated with the common cold, recent studies have established the rhinoviruses as important causes of other upper and lower respiratory illnesses as well. Treatment of these infections is limited to symptomatic therapy. There is no clear evidence that treatment with zinc or echinacea have any role in these infections. Interruption of transmission by handwashing remains the only method for prevention of rhinovirus infections.

Role of human mast cells and basophils in bronchial asthma

Mast cells and basophils are the only cells expressing the tetrameric (alphabetagamma2) structure of the high affinity receptor for IgE (FcepsilonRI) and synthesizing histamine in humans. Human FcepsilonRI+ cells are conventionally considered primary effector cells of bronchial asthma. There is now compelling evidence that these cells differ immunologically, biochemically, and pharmacologically, which suggests that they might play distinct roles in the appearance and fluctuation of the asthma phenotype. Recent data have revealed the complexity of the involvement of human mast cells and basophils in asthma and have shed light on the control of recruitment and activation of these cells in different lung compartments. Preliminary evidence suggests that these cells might not always be detrimental in asthma but, under some circumstances, they might exert a protective effect by modulating certain aspects of innate and acquired immunity and allergic inflammation.

Incidence of influenza and associated illness in children aged 0-19 years: a systematic review

A systematic review was conducted to estimate the incidence of influenza and concomitant morbidity and mortality in children from 0 to 19 years (0-19 years). Medline was searched for observational studies and placebo or non-treated arms of experimental studies providing occurrence rates of laboratory-proven influenza illness. From the 2758 titles identified, 356 full papers were reviewed based on the abstract or title; after searching their reference lists an additional 16 papers were found. Finally 28 studies met our inclusion criteria, reporting a varying seasonal incidence of influenza of up to 46%. However, when analysing two long-term observational studies and averaging seasonal fluctuations, the overall incidence of influenza was found to range from 5% to 9.5% per year. Serious morbidity was seldom reported and no cases of mortality were found. Our review shows influenza as an infection with a moderate average incidence and a self-limiting character that is associated with mild morbidity and rare cases of mortality in children. This systematic review may be subject to two contrasting biases. First, the limited number of children reported in the literature with proven influenza infections would tend to under-represent the incidence of uncommon but serious complications such as death. Second, the preferential reporting of influenza outbreak seasons may over-estimate the importance of influenza. Future population based studies should focus on consecutive influenza seasons and capture indirect benefits of vaccinations such as interruption of transmission in the community so that preventive strategies for children can be reconsidered with special attention to their cost effectiveness.

Mycoplasma pneumoniae induces host-dependent pulmonary inflammation and airway obstruction in mice

Respiratory tract infections result in wheezing in a subset of patients. Mycoplasma pneumoniae is a common etiologic agent of acute respiratory infection in children and adults that has been associated with wheezing in 20-40% of individuals. The current study was undertaken to elucidate the host-dependent pulmonary and immunologic response to M. pneumoniae respiratory infection by studying mice with different immunogenetic backgrounds (BALB/c mice versus C57BL/6 mice). After M. pneumoniae infection, only BALB/c mice developed significant airway obstruction (AO) compared with controls. M. pneumoniae-infected BALB/c mice manifested significantly elevated airway hyperresponsiveness (AHR) compared with C57BL/6 mice 4 and 7 d after inoculation as well as BALB/c control mice. Compared with C57BL/6 mice, BALB/c mice developed worse pulmonary inflammation, including greater peribronchial infiltrates. Infected BALB/c mice had significantly higher concentrations of tumor necrosis factor-alpha, interferon-gamma, interleukin (IL)-1beta, IL-6, IL-12, KC (functional IL-8), and macrophage inflammatory protein 1alpha in the bronchoalveolar lavage fluid compared with infected C57BL/6 mice. No differences in IL-2, IL-4, IL-5, IL-10, and granulocyte/macrophage colony-stimulating factor concentrations were found. The mice in this study exhibited host-dependent infection-related AO and AHR associated with chemokine and T-helper type (Th)1 pulmonary host response and not Th2 response after M. pneumoniae infection.

Allergic airway inflammation is exacerbated during acute influenza infection and correlates with increased allergen presentation and recruitment of allergen-specific T-helper type 2 cells

BACKGROUND

Respiratory viral infections are a leading cause of the hospitalization of asthmatics, however, the cellular immunological interactions which underlie these two diseases remain elusive.

OBJECTIVE

We sought to characterize the effect influenza viral infection has on allergic airway inflammation and to identify the cellular pathways involved.

METHODS

We have used an ovalbumin (OVA) model of allergic airway inflammation, which involves sensitization of animals with OVA adsorbed in alum adjuvant followed by an intranasal challenge with OVA in phosphate-buffered saline. To study T cell recruitment into the lung, we adoptively transferred in vitro activated T cell receptor-transgenic T cells, which were subsequently identified by fluorescence-activated cell sorting (FACS) analysis. In addition, to study in vivo dendritic cell (DC) migration, we administered fluorescently labelled dextran and identified DCs that had phagocytosed it by FACS analysis.

RESULTS

We found that different stages of influenza infection had contrasting effects upon the outcome of OVA-induced allergic airway inflammation. The allergic response against OVA was exacerbated during the acute stage of influenza infection; however, mice were protected against the development of airway eosinophilia at late time-points following infection. We investigated the mechanisms responsible for the virus-induced exacerbation and found that the response was partially independent of IL-4 and that there was increased delivery of inhaled allergens to the draining lymph node during the acute stage of the infection. In addition, virus-induced inflammation in the lung and draining lymph node resulted in the non-specific recruitment of circulating allergen-specific effector/memory cells.

CONCLUSION

In addition to virus-mediated damage to the lung and airways, influenza viral infection can also enhance unrelated local allergic responses.

Atopic disease and its determinants -- a focus on the potential role of childhood infection

BACKGROUND

Atopic diseases develop on a genetic background and are modulated by environmental factors among which some infectious diseases are thought to have a protective influence.

OBJECTIVE

The aim of this study was to determine the influence of infectious diseases in younger ages, bacterial and viral, on atopic diseases and sensitization to aero- and food-allergens in adults.

METHODS

A population-based sample of 4262 subjects aged 25-74 years were interviewed concerning their history of infectious disease within the first 18 years of life. Information about allergic disease, including atopic eczema, allergic rhinitis (AR), and asthma was obtained. A blood sample was drawn and analysed for allergen-specific IgE antibodies against food- and aero-allergens.

RESULTS

Multiple logistic regression analyses identified viral infection to be associated with AR (adjusted odds ratio (OR) = 1.39; 95% confidence interval (95% CI): 1.13-1.72) and sensitization to aeroallergens (OR = 1.21; 95% CI: 1.05-1.41). Bacterial disease was a negative predictor for atopy development in the subgroup of patients sensitized to nutritional allergens with concomitant atopic eczema (OR = 0.34; 95% CI: 0.11-0.99), AR (OR = 0.67; 95% CI: 0.42-1.07), or asthma (OR = 0.41; 95% CI: 0.19-0.87). Influences of viral and bacterial infection on AR differed with regard to family history of atopic disease.

CONCLUSION

In our study population, history of viral infection was consistently positively associated with AR. Our data suggests that bacterial infections might be preventive for specific subgroups of atopy.

Quantitative and qualitative analysis of rhinovirus infection in bronchial tissues

Although rhinovirus (RV) infections can cause asthma exacerbations and alter lower airway inflammation and physiology, it is unclear how important bronchial infection is to these processes. To study the kinetics, location, and frequency of RV appearance in lower airway tissues during an acute infection, immunohistochemistry and quantitative polymerase chain reaction analysis were used to analyze the presence of virus in cells from nasal lavage, sputum, bronchoalveolar lavage, bronchial brushings, and biopsy specimens from 19 subjects with an experimental RV serotype 16 (RV16) cold. RV was detected by polymerase chain reaction analysis on cells from nasal lavage and induced sputum samples from all subjects after RV16 inoculation, as well as in 5 of 19 bronchoalveolar lavage cell samples and in 5 of 18 bronchial biopsy specimens taken 4 days after virus inoculation. Immunohistochemistry detected RV16 in 39 and 36% of all biopsy and brushing samples taken 4 and 15 days, respectively, after inoculation. Infected cells were primarily distributed in discrete patches on the epithelium. These results confirm that infection of lower airway tissues is a frequent finding during a cold and further demonstrate a patchy distribution of infected cells, a pattern similar to that reported in upper airway tissues.

An update on the asthma-rhinitis link

PURPOSE OF REVIEW

For the present article we collected and reviewed the more relevant experimental results concerning the asthma-rhinitis link in allergic diseases, published since January 2002.

RECENT FINDINGS

During the last 2 years, particular attention has been devoted to the behaviour of the immune response in the two compartments of the airways. The recent experimental data, mainly obtained with specific nasal or bronchial allergen challenges, have confirmed that the link between the nose and the bronchi is bidirectional, and that a systemic cross-talk occurs. Furthermore, the pathogenic role of paranasal sinus infections in respiratory allergy has been better elucidated. It was shown that, in sinusitis, a T helper type 2 polarization exists, which can be reverted by proper therapy. On the other hand, despite the abundant experimental evidence, our view of the united airways is still not complete, and several points need to be developed.

SUMMARY

The new findings on the asthma-rhinitis link have confirmed the current pathogenic view of respiratory allergy. These findings have important implications from a therapeutic point of view, and therefore encourage and promote the search for novel integrated treatment strategies.

The Copenhagen Prospective Study on Asthma in Childhood (COPSAC): design, rationale, and baseline data from a longitudinal birth cohort study

BACKGROUND

The atopic diseases asthma, atopic dermatitis, and allergic rhinitis are the most common chronic diseases in children, and their prevalence has increased recently in industrialized nations. Little is known about the genetic-environmental interaction factors driving such proliferation.

OBJECTIVE

To investigate the relationships among genetic, environmental, and lifestyle factors in the development of atopic diseases in high-risk children with the aim of developing evidence-based prevention strategies.

METHODS

The Copenhagen Prospective Study on Asthma in Childhood is a single-center, birth cohort study of children of asthmatic mothers. Objective assessments begin at birth, with scheduled visits every 6 months and when acute symptoms manifest. Clinical outcomes comprise preasthma, asthma, atopic dermatitis, allergic rhinitis, allergy, lung function, and bronchial responsiveness. Exposure assessments comprise respiratory, intestinal, and skin microbiology; the child's diet; indoor and outdoor air quality; allergens; and indicators of lifestyle. Genetic characteristics of probands and parents are evaluated. Quality assurance follows Good Clinical Practice guidelines.

RESULTS

Four hundred eleven infants of asthmatic mothers were enrolled at the age of 1 month. The children were born between August 2, 1998, and December 28, 2001. Compared with the Copenhagen population, mothers of the cohort population were less likely to have given natural childbirth. The households were slightly less affluent, with fewer children and fewer pets. Whites may be overrepresented. At age 2 years, 93% of the infants were still actively participating in the cohort.

CONCLUSIONS

This longitudinal birth cohort study of high-risk Danish infants consists of objective phenotyping, detailed information on exposure, high data quality, and a high participant retention rate.

Vaccination for asthma exacerbations

Most asthma exacerbations are caused by common cold virus infections, predominantly rhinovirus infections. Full protection against repeat infections with the same rhinovirus serotype is given by serum neutralizing antibody, but cross-reactive antibody developed against other serotypes could yield partial protection and result in attenuated cold and airway symptoms. It is proposed that vaccine-mediated induction of cross-reactive antibody might not prevent rhinovirus infections but might reduce severe asthma symptoms and exacerbations.

How to improve current therapeutic standards in upper respiratory infections: value of fusafungine

Despite guidelines and educational programs, systemic antibiotics and anti-inflammatory drugs are often inappropriately prescribed in upper respiratory tract infections (URTIs), although they are most often of viral origin, generally benign, and self-limiting with spontaneous recovery in more than 80% of cases. Reduced use of systemic antibiotics is crucial in the current context of concern about emerging antibiotic resistance and reducing unnecessary costs associated both with drug over-consumption and with the management of the consequences of antibiotic resistance. Local bacterial or viral infection of the airways induces an early inflammatory reaction. Although this inflammatory reaction has a beneficial effect in the capture and destruction of the pathogens, it can be responsible for deleterious tissue damage and vascular alterations leading to a self-perpetuating cycle of events. A wide array of medicines is available for symptomatic relief of URTIs: many of them are partially effective in reducing symptoms, but none is curative. Local administration of antibiotics and anti-inflammatory drugs allows drug delivery directly to the target site of infection and inflammation, i.e., the respiratory mucosa, thus enabling a higher concentration of the drug, which results in smaller doses to be given, decreased potential for systemic toxicity, fewer side effects, protection of other flora, and rapid relief. Fusafungine is a naturally occurring peptide antibiotic with anti-inflammatory properties, which selectively targets the tissue reaction and preserves the natural antibacterial and antiviral defences. It is indicated for topical use in nose and throat infections. A recent analysis of French general practitioners' (GPs) prescribing pattern in the field of URTIs has demonstrated that prescription of fusafungine has achieved what many educational programs have failed to do: a significant reduction in the 'real life' prescription of systemic antibiotics and antiinflammatory drugs, without the side effects of corticosteroids and vasoconstrictive agents, and without impact on microbial ecology.

Detection of human Coronavirus 229E in nasal specimens in large scale studies using an RT-PCR hybridization assay

A novel human Coronavirus (HCoV) was this year recognized as the etiological agent of the Severe Acute Respiratory Syndrome. Two other HCoV (HCoV-229E and HCoV-OC43) have been known for 30 years. HCoV-229E has been recently involved in nosocomial respiratory viral infections in high-risk children. However, their diagnosis is not routinely performed. Currently, reliable immunofluorescence and cell culture methodologies are not available. As part of a four-year epidemiological study in a Pediatric and Neonatal Intensive care unit, we have performed and demonstrated the reliability of a reverse transcription-PCR-hybridization assay to detect HCoV of the 229E antigenic group in 2028 clinical respiratory specimens. In hospitalized children (children and newborns) and staff members we found a high incidence of HcoV-229E infection. This reverse transcription-PCR-hybridization assay gave a high specificity and a sensitivity of 0.5 50% Tissue Culture Infective Dose per ml. This technique is reliable and its application for screening large number of clinical samples would improve the diagnosis of HCoVs respiratory infection and our knowledge of these viruses epidemiology.

Upregulation of Interleukin-4 Receptor by Interferon-γ

Airway epithelial cells produce a number of chemokines, including eotaxins. Among the three known eotaxins, T helper (Th) type 2 cytokines have been observed to induce the expression of eotaxin-3 mRNA. This study investigated the effect of interferon (IFN)-gamma, a Th1 cytokine, on Th2 cytokine-induced eotaxin-3 production in a bronchial epithelial cell line, BEAS-2B. BEAS-2B cells produced eotaxin-3 after stimulation with the Th2 cytokines interleukin (IL)-13 and IL-4. When BEAS-2B cells were cultured with varying concentrations of IFN-gamma for 24 h, dose-dependent inhibition of Th2 cytokine-induced eotaxin-3 mRNA expression and protein production was observed. This was associated with downregulation of signal transducer and activator of transcription 6 activation. On the other hand, 2-d pretreatment of BEAS-2B cells with IFN-gamma dose-dependently enhanced Th2 cytokine-induced eotaxin-3 mRNA expression and production. IFN-gamma also increased the mRNA expression and protein production of IL-4 receptor (R) alpha in a time- and dose-dependent manner. In addition, IL-2Rgamma, a component of the type 1 IL-4R, was also upregulated by IFN-gamma. These results indicate that IFN-gamma has opposite effects on Th2 cytokine-induced eotaxin-3 production in BEAS-2B cells, depending on the length of exposure. Because high levels of IFN-gamma are produced during viral infection, airway viral infection may affect allergic airway inflammation in vivo by modulation of eotaxin-3 production.

Viral infections in relation to age, atopy, and season of admission among children hospitalized for wheezing

BACKGROUND

Viral respiratory tract infections and atopy are associated with attacks of wheezing during childhood. However, information about the relationship between viral infections and atopy among children whose attacks of wheezing lead to hospitalization is unclear.

OBJECTIVE

To evaluate the prevalence of viral respiratory tract pathogens among infants and children hospitalized for wheezing and to analyze the results in relation to the patient's age, atopic characteristics, and season of admission.

METHODS

This was a case-control study of children (age 2 months to 18 years) admitted for wheezing to the University of Virginia Medical Center over a period of 12 months. Children without wheezing were enrolled as controls. Nasal secretions were evaluated for viral pathogens by using cultures, PCR tests, and antigen detection. Total IgE and specific IgE antibody to common aeroallergens was measured in serum.

RESULTS

Seventy percent of children hospitalized for wheezing before age 3 years (n=79) were admitted between December and March, whereas 46% of children age 3 to 18 years (n=54) were hospitalized between September and November. Among children younger than 3 years, viral pathogens were detected in 84% (66/79) of wheezing children and 55% (42/77) of controls (P <.001). Respiratory syncytial virus was the dominant pathogen during the winter months, but rhinovirus was more common during other months. Total serum IgE levels were generally low, and values from wheezing and control subjects overlapped considerably. Among children 3 years and older, 61% (33/54) of subjects admitted for wheezing tested positive for virus (predominantly rhinovirus), compared with 21% (12/56) of controls (P <.001). The total serum IgE values among wheezing children (geometric mean, 386 IU/mL; 95% CI, 259-573) were substantially elevated compared with those of controls (geometric mean, 38 IU/mL; 95% CI, 26-56; P <.001). A significantly higher percentage of wheezing children compared with controls was sensitized to at least 1 of the inhaled allergens tested: 84% (36/43) compared with 33% (15/45; P <.001). The atopic characteristics of wheezing children who tested positive or negative for virus were similar.

CONCLUSIONS

Viral infections were the dominant risk factor for wheezing among children hospitalized before 3 years of age. By comparison, a large majority of the wheezing children age 3 to 18 years had striking atopic characteristics that may be critical as a risk factor for hospitalization and an adverse response to viral infections, especially infections caused by rhinovirus.

Lower respiratory viral illnesses: improved diagnosis by molecular methods and clinical impact

We assessed the frequency and the potential role of respiratory viruses on disease outcomes in hospitalized patients and lung transplant recipients who underwent a bronchoalveolar lavage (BAL) for an acute respiratory infection. BAL specimens (148) were analyzed by reverse transcription-polymerase chain reaction for the presence of 11 different viruses, as well as Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila. Respiratory viruses were identified in 34 of 117 BAL specimens (29%) obtained in patients with a suspected respiratory infection and in only 2 of 31 control subjects (7%) (p < 0.01). M. pneumoniae was identified in five additional cases. Only 30% of cases that were virus positive by molecular methods were also positive by cell culture analysis. Rhinovirus was the most frequently identified virus (56% of cases) followed by respiratory syncytial virus (27%). In lung transplant recipients, the rate of viral infections was 55% in cases with respiratory symptoms compared with only 4% in control subjects (p < 0.001). In these cases, respiratory viral infections were associated with significant lung function abnormalities. By using reverse transcription-polymerase chain reaction assays, we frequently identified respiratory viruses in BAL specimens of patients hospitalized with lower respiratory tract infections. These viruses were associated with high morbidity, particularly in lung transplant recipients.

Efficacy of organic acids in hand cleansers for prevention of rhinovirus infections

Direct hand-to-hand contact is an important mechanism of transmission of rhinovirus infection. The rhinoviruses are inactivated at a low pH. A survey of organic acids in vitro revealed that these compounds have antirhinoviral activity that persists for at least 3 h after application to the skin. In additional studies of salicylic acid (SA) and pyroglutamic acid (PGA), the hands of volunteers were contaminated with rhinovirus at defined times after application of the acid, and then volunteers attempted to inoculate the nasal mucosa with one hand and quantitative viral cultures were done on the other hand. In one study, 3.5% SA or 1% SA with 3.5% PGA was compared with controls 15 min after application to assess the efficacy of the inactivation of virus and prevention of infection. Virus was recovered from the hands of 28 out of 31 (90%) of the volunteers in the control group compared to 4 out of 27 (15%) and 0 out of 27 in the groups administered 3.5 and 1% SA, respectively (P < 0.05). Rhinovirus infection occurred in 10 out of 31 (32%) of the controls and 2 out of 27 (7%) of volunteers in both treatment groups (P < 0.05 compared with control). In a second study, the efficacy of 4% PGA was evaluated 15 min, 1 h, and 3 h after application. Significantly fewer volunteers had positive hand cultures at all time points compared with the control group, but the proportion that developed rhinovirus infection was not significantly reduced. These results suggest the feasibility of the prevention of rhinovirus transmission by hand treatments that are virucidal on contact and have activity that persists after application.

Mechanisms of rhinovirus-induced asthma

Several epidemiological studies using sensitive detection methodologies have confirmed that the majority of acute asthma exacerbations follow upper respiratory tract infections--common colds. Most of these colds are due to human rhinoviruses (RVs). RVs are able to reach and replicate in epithelial cells of the lower airways and can activate these cells to produce pro-inflammatory mediators. Under some circumstances, RVs can also become cytotoxic to the epithelium. Atopic asthmatic individuals produce less interferon-gamma and more interleukin-10 than normal subjects in response to RV infection. Symptom severity as well as viral shedding after experimental RV infection, is inversely correlated with 'atopic' status, expressed as the interferon-gamma to interleukin-5 ratio. Expression of co-stimulatory molecules on immune cells is also affected in atopic asthmatics, suggesting an aberrant immune response to RV that may lead to suboptimal viral clearance and viral persistence. Some of the above effects can be reversed in vitro by corticosteroids, second-generation antihistamines or anti-oxidants; however, the optimal strategy for treating acute asthma exacerbations requires further research at both mechanistic and clinical levels.

Virus-induced asthma attacks

Viral infections are responsible for the majority of asthma attacks in both children and adults. Vagally mediated reflex bronchoconstriction is potentiated due to loss of function of inhibitory M2 muscarinic receptors on the airway parasympathetic nerves. Multiple mechanisms are involved. Production of interferons may down regulate the expression of the M2 receptor gene. This effect is reversed by steroids. In allergic animals (and perhaps in atopic humans) eosinophils are recruited to the airway nerves, where they are activated, releasing major basic protein, which binds to the M2 receptors, blocking their function. Despite these negative physiological consequences of eosinophil activation, eosinophils are capable of exerting a potent antiviral effect. Thus, the inflammatory response to viral infections may have positive, as well as negative, consequences.

Respiratory picornaviruses and respiratory syncytial virus as causative agents of acute expiratory wheezing in children

We studied the viral etiology of acute expiratory wheezing (bronchiolitis, acute asthma) in 293 hospitalized children in a 2-year prospective study in Finland. A potential causative viral agent was detected in 88% of the cases. Eleven different viruses were represented. Respiratory syncytial virus (RSV) (27%), enteroviruses (25%), rhinovirus (24%), and nontypable rhino/enterovirus (16%) were found most frequently. In infants, RSV was found in 54% and respiratory picornaviruses (rhinovirus and enteroviruses) in 42% of the cases. In older children, respiratory picornaviruses dominated (65% of children ages 1-2 years and 82% of children ages >3 years). Human metapneumovirus was detected in 4% of all children and in 11% of infants. To prevent and treat acute expiratory wheezing illnesses in children, efforts should be focused on RSV, enterovirus, and rhinovirus infections.

Human airway submucosal glands augment eosinophil chemotaxis during rhinovirus infection

BACKGROUND

Asthma exacerbations are frequently associated with rhinovirus (RV) infections. However, the contribution of airway submucosal gland (SMG) to exacerbations of asthma in RV respiratory infection has not been studied.

OBJECTIVE

This study was undertaken to examine whether RV-infected human respiratory SMG cells produce pro-inflammatory cytokines and chemokines for eosinophils, and augment eosinophil transmigration across human airway epithelium.

METHODS

We infected cultured human tracheal SMG cells with RV14, collected culture media at 1, 3, and 5 days after infection, and measured the chemotactic activity for eosinophils in the culture supernatant using a 48-well microchemotaxis chamber and a (51)Cr-labelled eosinophil transmigration assay.

RESULTS

Exposing a confluent human tracheal SMG cell monolayer to RV14 consistently led to infection. Human SMG cells with RV infection secreted soluble factors activating human eosinophil chemotaxis into the culture supernatant in a time-dependent manner, and the culture supernatant significantly augmented the transmigration of (51)Cr-labelled eosinophils through human airway epithelial cell layers from the basal to mucosal side. These effects were completely abolished by a mixture of a monoclonal antibody regulated on activation, normal T cells expressed and secreted (RANTES) and an antibody to granulocyte macrophage-colony stimulating factor (GM-CSF).

CONCLUSION

These results suggest that human respiratory SMG cells may augment eosinophil transmigration across the airway epithelium through the secretion of RANTES and GM-CSF after RV infection, and may contribute to exacerbations of asthma.

Nasal mucosa in natural colds: effects of allergic rhinitis and susceptibility to recurrent sinusitis

The mechanisms of virus-induced airway hyperresponsiveness in asthma and allergy and the failure of host defence in patients suffering from secondary airway infections are still largely unknown. The aim of this study was to examine whether the presence of allergic rhinitis or susceptibility to recurrent sinusitis affects the structural and cellular changes in nasal mucosa during natural colds and convalescence. We compared the mucosal changes in biopsy samples during acute natural colds (days 2-4 of illness) and convalescence (3 weeks later) in patients with allergic rhinitis (n = 9), patients with susceptibility to sinusitis (n = 19) and healthy controls (n = 20). We saw similarly increased numbers of mucosal T and B lymphocytes and mast cells and increased vascular density during the acute colds compared to convalescence in all the three groups. The allergic subjects had elevated levels of eosinophils in the acute phase (P = 0.03), and the allergic and sinusitis-prone subjects had elevated levels of epithelial T cells (P = 0.04) and low levels of mast cells (P = 0.005) in convalescence compared to the control group. The sinusitis-prone subjects lacked intraepithelial cytotoxic cells in convalescence. In the allergic subjects, the reticular basement membrane was thicker in the acute phase compared to the convalescence (P = 0.05). These results suggest that various cells of the airways, including inflammatory and structural cells, are involved during viral respiratory infections in subjects with allergic rhinitis. The small numbers of mast cells and cytotoxic lymphocytes in the sinusitis-prone subjects may be related to their susceptibility to bacterial complications.

Human rhinovirus infection induces airway epithelial cell production of human beta-defensin 2 both in vitro and in vivo

We hypothesized that airway epithelial cells, the primary site of human rhinovirus (HRV) infection, provide a link between the innate and specific immune response to HRV via production of human beta-defensin (HBD)-2, a potent in vitro attractant and activator of immature dendritic cells. Infection of primary cultures of human epithelial cells with several HRV serotypes induced expression of HBD-2 mRNA and protein, indicating that HBD-2 production was independent of viral receptor usage or mechanisms of viral RNA internalization. Induction of HBD-2 was dependent upon viral replication and could be mimicked by transfection of cells with synthetic dsRNA, but was not dependent upon epithelial production of IL-1. Studies with stable epithelial cell lines expressing HBD-2 promoter constructs, as well as inhibitor studies in primary cells, both demonstrated that induction of HBD-2 involves activation of the transcription factor, NF-kappaB. Other transcription factors must also be activated by HRV infection, however, as expression of HBD-3 mRNA was also induced and there is no putative NF-kappaB recognition sequence in the promoter of this gene. HBD-2 showed no direct antiviral activity against HRV. In vivo infection of normal human subjects with HRV-16 induced expression of mRNA for HBD-2 in nasal epithelial scrapings. Increases in mRNA correlated with viral titer and with increased levels of HBD-2 protein in nasal lavages. This represents the first demonstration that HRV infection induces epithelial expression of HBD-2 both in vitro and in vivo, and supports the concept that HBD-2 may play a role in host defense to HRV infection.

Doubling the dose of budesonide versus maintenance treatment in asthma exacerbations

BACKGROUND

Previous guidelines recommend doubling the daily dose of maintenance inhaled corticosteroid to treat or prevent progression of exacerbations of asthma.

METHODS

Over a 6 month period a cohort of patients were evaluated prospectively and randomised in a double blind controlled trial to treatment with either a continued maintenance dose (MD) of inhaled corticosteroid or doubling the dose (DD) at the time of an exacerbation.

RESULTS

A total of 290 patients were randomised (33% male) and 98 (DD, n = 46) experienced evaluable asthma exacerbations during the study period. Mean (SD) baseline characteristics at randomisation (age 33.5 (14.0) years; forced expiratory volume in 1 second (FEV(1)) 2.8 (0.7) l; peak expiratory flow (PEF) 422.9 (110.5) l/min) were similar in both groups. In the DD group 41% of patients were considered treatment failures because they either required systemic steroids (n = 12), had an unscheduled visit to a physician (n = 1), or their asthma did not return to baseline (n = 6). This did not differ from the MD group in which 40% were treatment failures (n = 9, 0, and 12, respectively; p = 0.94).

CONCLUSIONS

In patients who regularly take an inhaled corticosteroid, doubling the maintenance dose may not affect the pattern of the exacerbation.

Rhinovirus detection: comparison of real-time and conventional PCR

Rhinoviruses are important human respiratory viruses and the major causative agents of the common cold. Historically, detection of rhinovirus has been by virus culture and this was significantly improved by the use of PCR assays. Recently real-time PCR was developed but to date there have been no reported comparisons of conventional and real-time PCR assays for detection of rhinovirus. In this study, we first compared real-time PCR (SYBR Green I) to conventional PCR for the detection of rhinovirus in serially diluted standard DNA and rhinovirus stock to determine the limits of detection. Next, assays were compared for sensitivity to detect rhinovirus in cell culture with a known number of infected cells. Finally, the assays were compared using clinical samples known to contain rhinovirus. Real-time PCR was 10-fold more sensitive than conventional PCR to detect rhinovirus in standard DNA and in virus stock and >10-fold more sensitive to detect rhinovirus in cultured cells. Real-time PCR was significantly superior for detection of rhinovirus in patients' nasal aspirates (sensitivity 72% versus 39%, P < 0.05). In summary, we found that real-time PCR was more sensitive than conventional PCR and reduced post-PCR processing. Hence, real-time PCR is suitable for both research and clinical purposes.