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

Seasonality of long term wheezing following respiratory syncytial virus lower respiratory tract infection

BACKGROUND

It is well known that respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) is associated with subsequent wheezing episodes, but the precise natural course of wheezing following RSV LRTI is not known. This study aimed to determine the continuous development of wheezing following RSV LRTI in children up to the age of 3 years.

METHODS

A prospective cohort study was performed in 140 hospitalised infants with RSV LRTI. Continuous follow up data were obtained with a unique log in which parents noted daily respiratory symptoms.

RESULTS

A marked decrease in wheezing was seen during the first year of follow up. The burden of wheezing following RSV LRTI was observed during the winter season. Signs of airflow limitation during RSV LRTI were strongly associated with wheezing during the follow up period. Total and specific serum immunoglobulin E levels, patient eczema, and parental history of atopy were not associated with wheezing.

CONCLUSIONS

Airway morbidity following RSV LRTI has a seasonal pattern, which suggests that viral upper respiratory tract infections are the predominant trigger for wheezing following RSV LRTI. There is a significant decrease in airway symptoms during the first 12 months after admission to hospital. Simple clinical variables, but not allergic risk factors, can predict the development of wheezing following RSV LRTI.

Role of macrophages in virus-induced airway hyperresponsiveness and neuronal M2 muscarinic receptor dysfunction

Viral infections exacerbate asthma. One of the pathways by which viruses trigger bronchoconstriction and hyperresponsiveness is by causing dysfunction of inhibitory M(2) muscarinic receptors on the airway parasympathetic nerves. These receptors normally limit acetylcholine (ACh) release from the parasympathetic nerves. Loss of M(2) receptor function increases ACh release, thereby increasing vagally mediated bronchoconstriction. Because viral infection causes an influx of macrophages into the lungs, we tested the role of macrophages in virus-induced airway hyperresponsiveness and M(2) receptor dysfunction. Guinea pigs infected with parainfluenza virus were hyperresponsive to electrical stimulation of the vagus nerves but not to intravenous ACh, indicating that hyperresponsiveness was due to increased release of ACh from the nerves. In addition, the muscarinic agonist pilocarpine no longer inhibited vagally induced bronchoconstriction, indicating M(2) receptor dysfunction. Treating animals with liposome-encapsulated dichloromethylene-diphosphonate depleted macrophages as assessed histologically. In these animals, viral infection did not cause airway hyperresponsiveness or M(2) receptor dysfunction. These data suggest that macrophages mediate virus-induced M(2) receptor dysfunction and airway hyperresponsiveness.

Activation of airway epithelial cells by toll-like receptor agonists

Toll-like receptors (TLR) play an important role in pathogen recognition and innate immunity. We investigated the presence and function of TLRs in the BEAS-2B airway epithelial cell line and primary bronchial epithelial cells. Standard real-time reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and Taqman RT-PCR revealed that BEAS-2B cells express mRNA for TLR1-10. Several TLR ligands were tested for their ability to activate gene expression in BEAS-2B cells using limited microarray analyses focusing on genes of the chemokine and chemokine receptor family, cytokines, and signaling pathways. While the TLR3 ligand double-stranded RNA was the most effective epithelial activator, clear responses to flagellin, lipopolysaccharide, CpG, peptidoglycan, and zymosan were also observed. RT-PCR and/or enzyme-linked immunosorbent assay were used to confirm results obtained with microarrays for five of the induced genes: interleukin-8, serum amyloid A, TLR3, macrophage inflammatory protein-3alpha, and granulocyte-macrophage colony-stimulating factor. Stimulation of epithelial cells with double-stranded RNA induced levels of interleukin-8 exceeding 20 ng/ml and levels of serum amyloid A exceeding 80 ng/ml. Double-stranded RNA, lipopolysaccharide, zymosan A, and flagellin also induced expression of macrophage inflammatory protein-3alpha and granulocyte-macrophage colony-stimulating factor, which may facilitate immature dendritic cell migration and maturation. These results suggest that airway epithelial cells express several TLRs and that they are functionally active. Epithelial expression of TLRs may be of importance in inflammation and immunity in the airways in response to inhaled pathogens.

Risk factors for wheezing in a subtropical environment: role of respiratory viruses and allergen sensitization

Background

Risk factors for acute wheezing among children in subtropical areas are largely unknown.

Objective

To investigate the role of viral infections, allergen sensitization, and exposure to indoor allergens as risk factors for acute wheezing in children 0 to 12 years old.

Methods

One hundred thirty-two children 0 to 12 years of age who sought emergency department care for wheezing and 65 children with no history of wheezing were enrolled in this case-control study. Detection of respiratory syncytial virus antigen, rhinovirus and coronavirus RNA, adenovirus, influenza, and parainfluenza antigens was performed in nasal washes. Total IgE and specific IgE to mites, cockroach, cat, and dog were measured with the CAP system. Major allergens from mites, cockroach, cat, and dog were quantified in dust samples by ELISA. Univariate and multivariate analyses were performed by logistic regression.

Results

In children under 2 years of age, infection with respiratory viruses and family history of allergy were independently associated with wheezing (odds ratio, 15.5 and 4.2; P = .0001 and P = .008, respectively). Among children 2 to 12 years old, sensitization to inhalant allergens was the major risk factor for wheezing (odds ratio, 2.7; P = .03). High-level allergen exposure, exposure to tobacco smoke, and lack of breast-feeding showed no association with wheezing.

Conclusions

Some risk factors for wheezing previously identified in temperate climates were present in a subtropical area, including respiratory syncytial virus infection in infants and allergy in children older than 2 years. Rhinovirus was not associated with wheezing and did not appear to be a trigger for asthma exacerbations.

The wheezy infant -- immunological and molecular considerations

Most of the data on the pathogenesis of asthma is based on information obtained through bronchial biopsies and bronchoalveolar lavage in adults and young adults. Ethical considerations linked to the invasive nature of airway endoscopy have limited the studies on the pathophysiology of asthma in infancy and early childhood. Although there is evidence that an asthma-like inflammation, with increased inflammatory cells and thickening of the lung basement membrane, may be present also at a very early age, clinical and epidemiologic studies suggest that asthma manifestations in preschool children may significantly differ from those observed in older subjects. In western countries, the vast majority of infants and young children has episodic (or intermittent) asthma, and the exacerbations generally defined "wheezing episodes" occur more frequently with a seasonal pattern being usually related to acute viral infections. There is strong epidemiological evidence that approximately 2/3 of all children who wheeze because of viral infections in early life (and are not atopic) have a transient condition that tends to disappear during early school years. All respiratory viruses may be implicated in the wheezing episodes, the principal being respiratory syncytial virus (RSV) and, with a lower frequency, adenovirus and parainfluenza viruses during the first 3 years of life, and rhinoviruses after that age. Infants and preschool children have on average 6-8 "colds" per year, but the illness tends to be limited to the upper respiratory tract alone in a considerable proportion of individuals, without causing symptomatic involvement of the lower respiratory tract. The variety of factors determining the different outcomes are only partially known, but complex interactions between the intrinsic pathogenicity of the virus and host factors, including the socio-economic conditions of the family, are central to define the type of manifestations and the severity of the process.

Pathogenesis of respiratory syncytial virus bronchiolitis-related wheezing

Respiratory syncytial virus (RSV) is a common cause of virus infection of the human respiratory tract during the first two years of life, with virtually all children experiencing at least one infection within this period. Although this usually leads to mild respiratory illness, some infants develop more severe disease (bronchiolitis, pneumonia, etc.) affecting the lower airways and frequently requiring hospitalisation. There is evidence that bronchiolitis hospitalisations have increased during the last two decades and many of the hospitalised children develop wheezing later in life. The immune response to the virus is probably a major factor in the development or the expression of the pathological phenotype. In particular, a bias towards type-2 cytokine responses seems to be associated with more severe disease, whereas a type-1 response leads to more effective viral clearance and milder illness. Although the virus by itself triggers a type-1 response, a preexisting type-1 deficiency may contribute to the severity of the disease. In that sense, RSV bronchiolitis may serve as a marker, reflecting predisposition of the individual for virus induced wheezing early in life and/or asthma later in life.

Respiratory syncytial virus in allergic lung inflammation increases Muc5ac and gob-5

Respiratory syncytial virus (RSV) is associated with wheezing and childhood asthma. We previously reported that RSV infection prolongs methacholine-induced airway hyperresponsiveness in ovalbumin (OVA)-sensitized mice. In addition, allergically sensitized RSV-infected (OVA/RSV) mice had more abundant airway epithelial mucus production compared with OVA mice 14 days after infection, whereas there was almost no mucus in mice that were only RSV infected. We hypothesized that this increased mucus was associated with mucosal expression of Muc5ac, a mucus gene expression in airways, and gob-5, a member of the Ca(2)(+)-activated chloride channel family. By histochemical analysis, we found that there was significantly increased staining for gob-5 and Muc5ac in the airways of OVA/RSV mice compared with either OVA mice or allergically sensitized mice that were challenged with inactivated RSV, and virtually no detectable staining in the RSV group. These findings were confirmed by Western blot analysis. The increased mucus expression in the OVA/RSV group was associated with increased lung levels of interleukin-17, a factor known to stimulate airway mucin gene expression. The impact of virus infection combined with allergic inflammation on mucus production may partially explain the more severe disease and airway hyperresponsiveness associated with RSV in the setting of atopy.

Rhinopharyngites de l’enfant

La rhinopharyngite désigne une inflammation modérée des voies aériennes supérieures d’origine infectieuse. Les signes habituels en sont l’obstruction nasale, la rhinorrhée, l’éternuement, la douleur pharyngée et la toux. Le terme de rhinopharyngite est spécifiquement français. Les auteurs anglo-saxons parlent de rhume (common cold) ou de upper respiratory tract infection (URI) pour décrire une inflammation aiguë des voies aériennes supérieures, et d’adénoïdite chronique (chronic adenoiditis) pour désigner une infection chronique des végétations adénoïdes responsable de rhinorrhées fébriles itératives ou d’obstruction des voies aériennes supérieures. Les rhinopharyngites aiguës non compliquées sont d’origine virale. Leur évolution spontanée est habituellement rapide et non compliquée. Elles ne nécessitent donc ni prélèvement bactériologique ni antibiothérapie systématique. En première intention, elles relèvent exclusivement d’un traitement antalgique et antipyrétique associé à des lavages des fosses nasales au sérum salé iso- ou hypertonique. Les complications des rhinopharyngites sont infectieuses, essentiellement représentées par les otites et les sinusites, et respiratoires obstructives. Le caractère fréquemment itératif des rhinopharyngites à partir de l’âge de 6 mois reflète un processus physiologique de maturation du système immunitaire. En présence de rhinopharyngites fréquentes et invalidantes, les principaux facteurs de risque devant être recherchés et si possible éradiqués sont le tabagisme passif et la fréquentation d’une collectivité d’enfants. L’adénoïdectomie n’est pas indiquée en l’absence de complications. Le développement d’antiviraux efficaces dans la prévention et dans le traitement des rhinopharyngites fait l’objet d’intenses recherches cliniques et expérimentales.

Mycoplasma pneumoniae and asthma in children

The aim of this prospective study of a population of children (age, 2-15 years) hospitalized for severe asthma was to test them for acute infection due to Mycoplasma pneumoniae and acute infection due to Chlamydia pneumoniae. Of 119 patients with previously diagnosed asthma, acute M. pneumoniae infection was found in 24 (20%) and C. pneumoniae infection was found in 4 (3.4%) of the patients during the current exacerbation. Of 51 patients experiencing their first asthma attack, acute M. pneumoniae infection was proven in 26 (50%) of the patients (P<.01) and C. pneumoniae in 4 (8.3%). In the control group of 152 children with stable asthma or rhinitis, 8 (5.2%) had M. pneumoniae infection (P<.005). Of the 29 patients experiencing their first asthma attack and infected with M. pneumoniae or C. pneumoniae, 18 (62%) had asthma recurrences but only 6 (27%) of the 22 patients who did not have such infections had asthma recurrences (P<.05). M. pneumoniae may play a role in the onset of asthma in predisposed children and could be a trigger for recurrent wheezing.

Detection of influenza, parainfluenza, adenovirus and respiratory syncytial virus during asthma attacks in children older than 2 years old

BACKGROUND

Viral upper respiratory tract infections (URTI) have been correlated with the onset of asthma attacks in children and viral identification was reported in 14-49 % of nasal samples. The aim of the present study was to detect influenza, parainfluenza, adenovirus and respiratory syncytial virus (RSV) in older children during acute asthma attacks.

METHODS

A total of 104 children (2-14 years) were included in four groups: group I: asthmatics with acute attack and URTI; group II: asthmatics without URTI (group I children, 30 days later); group III: non-asthmatics with URTI; group IV: non-asthmatic, asymptomatic children. A diagnosis of URTI was considered when (3 symptoms (cough and/or sneeze, nasal obstruction, hypertrophy of turbinates, pain and/or retropharynx hyperemia, headache and fever) in asthmatics and at least 2 symptoms in non-asthmatics were present, starting within 7 days. Samples of nasal mucosa cells (n = 123) were collected, and culture and indirect immunofluorescence were carried out to identify respiratory syncytial virus, adenovirus, influenza A and B, parainfluenza 1,2 and 3 and rhinovirus.

RESULTS

Viral identification rates were higher in the asthmatic groups: 13.9 % in group I, 11.1 % in group II; 2.8 % in group III and 0 in group IV. The following viruses were identified: RSV 2/36, rhinovirus 1/36, adenovirus 1/36 and parainfluenzae 1/36 in group I; adenovirus 2/18 in group II; RSV 1/36 in group III.

CONCLUSIONS

The rate of viral identification was higher in asthmatic children, whether symptomatic or not, suggesting a possible susceptibility to viral infections. Virus could also be a triggering factor in attacks, although it is not the most preponderant in older children.

The common cold: a review of the literature

Respiratory viral infections, also known as the common cold, are the most common infections in humans. Despite their benign nature, they are a major cause of morbidity and mortality on a worldwide basis. Several viruses have been associated with such illness, of which rhinovirus is the most common. Symptom production is a combination of viral cytopathic effect and the activation of inflammatory pathways. Therefore, antiviral treatment alone may not be able to prevent these events. The optimal use of such agents also requires earlier initiation; therefore, it is important to develop accurate and rapid diagnostic techniques for respiratory viruses. Before any reliable and effective treatment is available, symptomatic therapies may remain the only possible choice of management.

Simultaneous detection of fourteen respiratory viruses in clinical specimens by two multiplex reverse transcription nested-PCR assays

There is a need for rapid, sensitive, and accurate diagnosis of lower respiratory tract infections in children, elderly, and immunocompromised patients, who are susceptible to serious complications. The multiplex RT‐nested PCR assay has been used widely for simultaneous detection of non‐related viruses involved in infectious diseases because of its high specificity and sensitivity. A new multiplex RT‐PCR assay is described in this report. This approach includes nested primer sets targeted to conserve regions of human parainfluenza virus haemagglutinin, human coronavirus spike protein, and human enterovirus and rhinovirus polyprotein genes. It permits rapid, sensitive, and simultaneous detection and typing of the four types of parainfluenza viruses (1, 2, 3, 4AB), human coronavirus 229E and OC43, and the generic detection of enteroviruses and rhinoviruses. The testing of 201 clinical specimens with this multiplex assay along with other one formerly described by our group to simultaneously detect and type the influenza viruses, respiratory syncytial viruses, and a generic detection of all serotypes of adenovirus, covers the detection of most viruses causing respiratory infectious disease in humans. The results obtained were compared with conventional viral culture, immunofluorescence assay, and a third multiplex RT‐PCR assay for all human parainfluenza viruses types described previously. In conclusion, both multiplex RT‐PCR assays provide a system capable of detecting and identifying simultaneously 14 different respiratory viruses in clinical specimens with high sensitivity and specificity, being useful for routine diagnosis and survey of these viruses within the population. J. Med. Virol. 72:484–495, 2004. © 2004 Wiley‐Liss, Inc.

Rhinovirus and the lower respiratory tract

Human rhinoviruses (HRVs) are well‐recognised causes of common colds and associated upper respiratory tract complications such as sinusitis and otitis media. This article reviews information linking HRV infection to illness in the lower respiratory tract. HRVs are capable of efficient replication in vitro at temperatures present in the tracheobronchial tree and have been shown to cause productive infection, elaboration of cytokines and chemokines, and up‐regulation of cell surface markers in human bronchial epithelial cells. In situ hybridisation studies have proven that HRV infection occurs in the tracheobronchial tree following experimental infection. Clinical studies report that HRV infection is the second most frequently recognised agent associated with pneumonia and bronchiolitis in infants and young children and commonly causes exacerbations of pre‐existing airways disease in those with asthma, chronic obstructive pulmonary disease or cystic fibrosis. HRV infection is associated with one‐third to one‐half of asthma exacerbations depending on age and is linked to asthma hospitalisations in both adults and children. Limited information implicates HRV infection as a cause of severe lower respiratory tract illness in older adults and in highly immunocompromised hosts, particularly bone marrow transplant recipients. More information is needed about the pathogenesis of HRV infection with regard to lower respiratory tract complications in these diverse patient groups. Given the large unmet medical need associated with HRV infections, safe and effective antiviral agents are needed for both prevention and treatment of these infections. Copyright © 2004 John Wiley & Sons, Ltd.

Macrolide and occult infection in asthma

PURPOSE OF REVIEW

A small percentage of asthma exacerbations are linked with infection by an atypical bacterium, such as Chlamydia pneumoniae or Mycoplasma pneumoniae. These bacteria also have been proposed to cause occult chronic lower airway inflammation and to initiate nonatopic asthma in adults. Consequently, the logical procedure would be to eliminate these pathogens as soon and as thoroughly as possible using antibiotics. Nonetheless, antibiotics are not recommended even for the treatment of acute asthma exacerbations except as needed for comorbid conditions. These discrepancies highlight the need to define the role, if any, of antimicrobials that are active against atypical pathogens, mainly macrolides, but also tetracyclines and fluoroquinolones, in the treatment of asthma.

RECENT FINDINGS

Macrolides are antibiotics with both antimicrobial and antiinflammatory activities. Some studies have documented that these agents could be useful in the treatment of occult infection in asthma because of their antimicrobial activity against atypical pathogens. They could also lead to reduction of the airways inflammation by decreasing the transcription of mRNA for a variety of cytokines and inhibiting interleukin-8 release by eosinophils, and therefore improvement of symptoms and pulmonary function. These effects are not caused by bronchodilation, elevation of serum theophylline level, or steroid-sparing mechanism.

SUMMARY

The available clinical evidence seems to support use of macrolides in the treatment of asthma because of their antimicrobial activity. However, studies that may confirm this hypothesis are scarce and with limited scientific value because of their open, uncontrolled design.

The natural history of asthma in a primary care cohort

BACKGROUND

We examined the natural history of asthma in a primary care cohort of patients 10 years after the cohort was stratified for asthma risk by responses to a questionnaire and bronchial hyperresponsiveness (BHR) testing.

METHODS

Children and young adults who were born between 1967 and 1979 within 1 of 4 affiliated family practices of the Nijmegen Department of Family Medicine, The Netherlands, were asked to participate in an asthma study in 1989. Of 926 patients available, 581 (63%) agreed to participate. Their family physicians' diagnoses of upper and lower respiratory tract disease and asthma were prospectively collected during the next 10 years and were analyzed.

RESULTS

BHR or the presence of asthma symptoms at screening did not result in a significantly disproportionate number of physician visits during the next 10 years for 4 or more upper or lower respiratory tract infections when compared with patients who did not have these findings at the beginning of the study. The presence of asthma symptoms correlated with an increased risk of an asthma diagnosis or allergic rhinitis in the group of patients who did not have asthma diagnosed at start of the study. One half of the known asthmatic patients at the onset of the study (21 of 44) had no further visits to their physicians for treatment of asthma during the next 10 years.

CONCLUSIONS

In primary care, BHR testing has limited value in predicting subsequent respiratory tract disease for patients who have asthma diagnosed by a physician. The use of symptom questionnaires can be of clinical use in predicting asthma.

Phase II, randomized, double-blind, placebo-controlled studies of ruprintrivir nasal spray 2-percent suspension for prevention and treatment of experimentally induced rhinovirus colds in healthy volunteers

Human rhinovirus (HRV) infections are usually self-limited but may be associated with serious consequences, particularly in those with asthma and chronic respiratory disease. Effective antiviral agents are needed for preventing and treating HRV illnesses. Ruprintrivir (Agouron Pharmaceuticals, Inc., San Diego, Calif.) selectively inhibits HRV 3C protease and shows potent, broad-spectrum anti-HRV activity in vitro. We conducted three double-blind, placebo-controlled clinical trials in 202 healthy volunteers to assess the activity of ruprintrivir in experimental HRV infection. Subjects were randomized to receive intranasal ruprintrivir (8 mg) or placebo sprays as prophylaxis (two or five times daily [2x/day or 5x/day] for 5 days) starting 6 h before infection or as treatment (5x/day for 4 days) starting 24 h after infection. Ruprintrivir prophylaxis reduced the proportion of subjects with positive viral cultures (for 5x/day dosing groups, 44% for ruprintrivir treatment group versus 70% for placebo treatment group [P=0.03]; for 2x/day dosing groups, 60% for ruprintrivir group versus 92% for placebo group [P=0.004]) and viral titers but did not decrease the frequency of colds. Ruprintrivir treatment reduced the mean total daily symptom score (2.2 for ruprintrivir treatment group and 3.3 for the placebo treatment group [P=0.014]) by 33%. Secondary endpoints, including viral titers, individual symptom scores, and nasal discharge weights, were also reduced by ruprintrivir treatment. Overall, ruprintrivir was well tolerated; blood-tinged mucus and nasal passage irritation were the most common adverse effects reported. Pharmacokinetic analysis of plasma and nasal ruprintrivir concentrations revealed intranasal drug residence with minimal systemic absorption. Results from these studies in experimental rhinoviral infection support continued investigation of intranasal ruprintrivir in the setting of natural HRV infection.

Effect of environmental interventions to reduce exposure to asthma triggers in homes of low-income children in Seattle

The effectiveness of community health workers (CHWs) assisting families in reducing exposure to indoor asthma triggers has not been studied. In all, 274 low-income asthmatic children were randomly assigned to high- or low-intensity groups. CHWs visited all homes to assess exposures, develop action plans and provide bedding encasements. The higher-intensity group also received cleaning equipment and five to nine visits over a year focusing on asthma trigger reduction. The asthma trigger composite score decreased from 1.56 to 1.19 (Delta=-0.37, 95% CI 0.13, 0.61) in the higher-intensity group and from 1.63 to 1.43 in the low-intensity group (Delta=-0.20, 95% CI 0.004, 0.4). The difference in this measure due to the intervention was significant at the P=0.096 level. The higher-intensity group also showed improvement during the intervention year in measurements of condensation, roaches, moisture, cleaning behavior, dust weight, dust mite antigen, and total antigens above a cut point, effects not demonstrated in the low-intensity group. CHWs are effective in reducing asthma trigger exposure in low-income children. Further research is needed to determine the effectiveness of specific interventions and structural improvements on asthma trigger exposure and health.

Viral respiratory infection and the link to asthma

BACKGROUND

Acute wheezing secondary to viral infection is common in children. Whereas many children suffer primarily mild to moderate symptoms, others develop severe coughing and wheezing.

METHODS

Review of recent medical literature regarding the correlation between viral illness and increased susceptibility to develop severe respiratory illnesses and subsequent asthma.

DISCUSSION

In infants factors that predispose to severe disease and lower respiratory airway effects include small lung size, passive smoke exposure, virus-induced immune responses, severe disease and infection at a young age. Acute asthma symptoms have been correlated with a variety of viral pathogens, most commonly respiratory syncytial virus bronchiolitis in infancy and rhinovirus in older children. Epidemiologic and biologic factors that influence development of asthma include repeated exposure to infectious disease during early childhood, early exposure to pets, a farming lifestyle, alterations in bacterial flora of the intestine and increased use of antibiotics. Thus the likelihood of asthma is related to the specific pathogen, severity of infection, cumulative number of infections and stage of immunologic development. Progress is also being made in understanding how viruses can adversely affect lung or immune development. In asthmatic children viral infections initiate bronchospasm and airway obstruction. It is hoped that research on virus-induced airway alterations and the host factors that lead to severe clinical illnesses can help clinicians to identify children whose wheezing is an early sign of asthma.

Rhinovirus 16 3C protease induces interleukin-8 and granulocyte-macrophage colony-stimulating factor expression in human bronchial epithelial cells

Rhinovirus (RV), a member of the Picornaviridae family, accounts for many virus-induced asthma exacerbations. RV induces airway cell chemokine expression both in vivo and in vitro. Because of the known interactions of proteases with cellular functions, we hypothesized that RV 3C protease is sufficient for cytokine up-regulation. A cDNA encoding RV16 3C protease was constructed by PCR amplification and transfected into 16HBE14o- human bronchial epithelial cells. 3C protease induced expression of both IL-8 and GM-CSF, as well as transcription from both the IL-8 and GM-CSF promoters. 3C expression also induced activator protein 1 and NF-kappaB transcriptional activation. Finally, mutation of IL-8 promoter AP-1 and NF-kappaB promoter sequences significantly reduced 3C-induced responses. Together, these data suggest expression of RV16 3C protease is sufficient to induce chemokine expression in human bronchial epithelial cells, and does so in an AP-1- and NF-kappaB-dependent manner.

Rinofaringitis infantiles

La rinofaringitis designa una inflamación moderada de las vías respiratorias superiores de origen infeccioso. Sus signos habituales son obstrucción nasal, rinorrea, estornudos, dolor faríngeo y tos. Los autores anglosajones hablan de catarro (common cold) o de infección de vías respiratorias altas para describir una inflamación de las vías respiratorias superiores, y de adenoiditis crónica (chronic adenoiditis) para designar una infección crónica de las vegetaciones adenoides que produce rinorrea febril recidivante u obstrucción de las vías respiratorias altas. Las rinofaringitis agudas no complicadas son de origen vírico. Habitualmente su evolución espontánea es rápida y sin complicaciones. Por tanto, no hay que obtener muestras bacteriológicas ni hacer un tratamiento antibiótico sistemático. Como tratamiento de primera línea, sólo precisan analgésicos y antipiréticos asociados a lavados de las fosas nasales con suero salino isotónico o hipertónico. Las complicaciones de las rinofaringitis son infecciosas –representadas esencialmente por las otitis y las sinusitis– y respiratorias obstructivas. El carácter a menudo repetitivo de las rinofaringitis a partir de los 6 meses de edad refleja un proceso fisiológico de maduración del sistema inmunitario. Cuando existen rinofaringitis frecuentes e invalidantes, los principales factores de riesgo que se deben buscar, y de ser posible erradicar, son el tabaquismo pasivo y los contactos con una población infantil. La adenoidectomía ya no está indicada si no existen complicaciones. Se están realizando investigaciones clínicas y experimentales sobre el desarrollo de fármacos antivíricos eficaces para la prevención y el tratamiento de las rinofaringitis.

Host defense function of the airway epithelium in health and disease: clinical background

Respiratory infection is extremely common and a major cause of morbidity and mortality worldwide. The airway epithelium has an important role in host defense against infection and this is illustrated in this review by considering infection by respiratory viruses. In patients with asthma or chronic obstructive pulmonary disease, respiratory viruses are a common trigger of exacerbations. Rhinoviruses (RV) are the most common virus type detected. Knowledge of the immunopathogenesis of such RV-induced exacerbations remains limited, but information is available from in vitro and from in vivo studies, especially of experimental infection in human volunteers. RV infects and replicates within epithelial cells (EC) of the lower respiratory tract. EC are an important component of the innate-immune response to RV infection. The interaction between virus and the intracellular signaling pathways of the host cell results in activation of potentially antiviral mechanisms, including type 1 interferons and nitric oxide, and in the production of cytokines and chemokines [interleukin (IL)-1 beta, IL-6, IL-8, IL-11, IL-16, tumor necrosis factor alpha, granulocyte macrophage-colony stimulating factor, growth-regulated oncogene-alpha, epithelial neutrophil-activating protein-78, regulated on activation, normal T expressed and secreted, eotaxin 1/2, macrophage-inflammatory protein-1 alpha], which influence the subsequent induced innate- and specific-immune response. Although this is beneficial in facilitating clearance of virus from the respiratory tract, the generation of proinflammatory mediators and the recruitment of inflammatory cells result in a degree of immunopathology and may amplify pre-existing airway inflammation. Further research will be necessary to determine whether modification of EC responses to respiratory virus infection will be of therapeutic benefit.

Acute cough in the elderly: aetiology, diagnosis and therapy

Although the frequency of physician consultations and the sale of over-the-counter remedies establish the high prevalence of acute cough in the elderly, epidemiological studies have tended to be imprecise. However, respiratory tract infections in nose, larynx and/or bronchi, either viral or bacterial or both, are by far the commonest cause of acute cough. These are especially frequent and hazardous in the elderly, and community living and institutionalisation may aggravate this problem. A variety of viruses and bacteria have been incriminated, with rhinovirus, influenza and respiratory syncytial viruses, and Streptococcus pneumoniae, Haemophilus influenza and Bordetella pertussis being especially important. Viral infections can readily lead to community-acquired pneumonia. Successful diagnosis should point to successful treatment, and in this respect clinical examination and patient history are paramount, supplemented by chest X-ray, viral and bacterial culture and serological testing. Depending on the results of these tests, specific antibacterial therapy may be called for, although there is dispute as to the merits of antibacterial therapy in cases of uncertain diagnosis. Prevention and prophylaxis for influenza and S. pneumoniae infections are now commendably routine in the elderly, especially those in communities. Treatment, as well as the use of antibacterials, may also be directed against the inflammatory and infective processes in the airways. Non-specific antitussive therapy is common and usually highly desirable to prevent the adverse effects of repeated coughing. There have been few advances in antitussive therapy in recent years, opioids and dextromethorphan being the most commonly used agents; they act centrally on the brainstem, but also have a large placebo effect. However they work, they are much appreciated by patients and their partners. Moreover, striking advances in our understanding of the peripheral sensory and central nervous pathways of the cough reflex in recent years should soon lead to a new and more specific choice of agents to inhibit cough.

Vaccines for preventing influenza in people with asthma

BACKGROUND

Influenza vaccination is recommended for asthmatic patients in many countries as observational studies have shown that influenza infection can be associated with asthma exacerbations, but influenza vaccination itself has the potential to adversely affect pulmonary function. A recent overview concluded that there was no clear benefit of influenza vaccination in patients with asthma but this conclusion was not based on a systematic search of the literature.

OBJECTIVES

Whilst influenza may cause asthma exacerbations, there is controversy about the use of influenza vaccinations, since they may precipitate an asthma attack in some people. The objective of this review was to assess the efficacy of influenza vaccination in children and adults with asthma.

SEARCH STRATEGY

We searched the Cochrane Airways Group trials register and checked reference lists of articles. The last search was carried out in February 2003.

SELECTION CRITERIA

Randomised trials of influenza vaccination in children (over two years of age) and adults with asthma. Studies involving people with chronic obstructive pulmonary disease were excluded.

DATA COLLECTION AND ANALYSIS

Inclusion criteria and assessment of trial quality were applied by two reviewers independently. Data extraction was done by two reviewers independently. Study authors were contacted for missing information.

MAIN RESULTS

Nine trials were initially included. Four of these trials were of high quality. Five further articles have been included in two updates (Bueving 2002; Castro 2001; Redding 2002; Reid 1998). The included studies covered a wide diversity of people, settings and types of influenza vaccination, but data from the more recent studies that used similar vaccines have been pooled. The pooled results of two trials involving 2306 people with asthma did not demonstrate a significant increase in asthma exacerbations in the two weeks following influenza vaccination (Risk Difference 0.00; 95% confidence interval -0.02 to 0.02). A recent study on 696 children with asthma did not demonstrate a significant reduction in influenza related asthma exacerbations (Risk Difference 0.01; 95% confidence interval -0.02 to 0.04).

REVIEWERS' CONCLUSIONS

Evidence from recently published trials indicates that there is no significant increase in asthma exacerbations immediately after vaccination (at least with inactivated influenza vaccination); however, uncertainty remains about the degree of protection vaccination affords against asthma exacerbations that are related to influenza infection.

Interleukin-1beta and interleukin-1ra levels in nasal lavages during experimental rhinovirus infection in asthmatic and non-asthmatic subjects

BACKGROUND

Exacerbations of asthma are often associated with rhinovirus (RV)-induced common colds. During experimental RV-infection in healthy subjects, increased levels of the pro-inflammatory mediator IL-1beta and the anti-inflammatory IL-1 receptor antagonist (IL-1ra) have been found in nasal lavage.

OBJECTIVE

We postulated that the balance between nasal pro- and anti-inflammatory mediator expression is disturbed in asthma, resulting in more extensive inflammation following RV-exposure in asthma.

METHODS

We determined IL-1ra, IL-1beta, and IL-8 in nasal lavages (days -2, 3, and 6) of non-asthmatics and asthmatics (with and without pre-treatment with the inhaled steroid budesonide) before and after experimental RV16-infection (days 0 and 1).

RESULTS

Following RV16-infection, a significant increase in IL-8 was observed in the placebo- and budesonide-treated asthmatics (P=0.033 and 0.037, respectively), whereas IL-1beta only increased in the two asthma groups combined (P=0.035). A small, but significant, increase in IL-1ra was only observed in the budesonide-treated asthmatics (P=0.047). At baseline, IL-1ra levels were significantly higher in the non-asthmatics than in the placebo-treated asthmatics (P=0.017).

CONCLUSION

These results demonstrate differences between non-asthmatic and asthmatic subjects in the basal levels of nasal cytokines and their inhibitors, and in the effect of experimental RV-infection on these levels. The results indicate that RV may enhance inflammation more markedly in asthmatics, and suggest that this may in part be explained by lower IL-1ra levels. In addition, the observation that budesonide-treatment may result in higher nasal IL-1ra levels supports the hypothesis that steroids act in part by increasing the endogenous anti-inflammatory screen.

Influenza vaccination in children with asthma: randomized double-blind placebo-controlled trial

There is little evidence that influenza vaccination reduces asthma exacerbations. We determined whether influenza vaccination is more effective than placebo in 6-18-year-old children with asthma. We performed a randomized, double-blind, placebo-controlled trial. Parenteral vaccination with inactivated influenza vaccine or placebo took place approximately November 1, and children were followed until April 1 of the next year. Airway symptoms were reported in a diary. When symptom scores reached a predefined level, a pharyngeal swab was taken. Primary outcome was the number of asthma exacerbations associated with virologically proven influenza infection. Three hundred forty-nine children were assigned placebo, and 347 were assigned vaccine. Pharyngeal swabs positive for influenza were related to 42 asthma exacerbations, 24 in the vaccine group and 18 in the placebo group, a difference of 33% favoring placebo (31% after adjustment for confounders; 95% confidence interval, -34% to 161%). Influenza-related asthma exacerbations were of similar severity in both groups; they lasted 3.1 days shorter in the vaccine group (95% confidence interval, -6.2 to 0.002 days, p = 0.06). We conclude that influenza vaccination did not result in a significant reduction of the number, severity, or duration of asthma exacerbations caused by influenza. Additional studies are warranted to justify routine influenza vaccination of children with asthma.

Evaluation of clinical and immunological effects of inactivated influenza vaccine in children with asthma

Although annual influenza vaccinations are recommended by many authorities, some doctors may be reluctant to vaccinate asthmatic children because of the risk of inducing bronchial reactivity and exacerbating the asthma. In this study, the effect of split influenza vaccine on clinical symptoms, airway responsiveness and its influence on T lymphocytes was evaluated. Twenty-one asthmatic children with stable asthma were recruited and divided into two groups. Eleven patients who received the influenza vaccine formed the vaccination group and 10 patients who received a placebo formed the placebo group. Forced expiratory volume in 1 s (FEV1), airway response (PC20 methacholine, PC20=provocation concentration causing a 20% fall in FEV1) and the T lymphocyte subset ratio (Th1/Th2) were recorded on day 1 pre-vaccination and day 14 post-vaccination. Patients were also asked to record their peak expiratory flow (PEF) every morning and evening and to complete daily symptom scores over the period of 2 weeks. There were no significant changes in PC20, FEV1, PEF variability, symptom scores and the Th1/Th2 ratio between the vaccination and placebo groups between day 1 pre-vaccination and day 14 post-vaccination. Similar results of PEF variability and asthma symptom score were obtained when the analysis was restricted to the day 1 pre-vaccination and day 3 post-vaccination. Immunization with split influenza vaccine does not exacerbate asthma in children either with a clinical or immunological effect. These results suggest that children with stable asthma can safely be immunized with a split influenza vaccine.

Are rhinovirus-induced airway responses in asthma aggravated by chronic allergen exposure?

Airway inflammation in asthma may represent a favorable environment for respiratory viral infections, augmenting virus-induced exacerbations in asthma. We postulated that repeated low-dose allergen exposure preceding experimental rhinovirus 16 (RV16) infection increases the severity of RV-induced airway obstruction and inflammation. Thirty-six house dust mite-allergic patients with mild to moderate asthma participated in a three-arm, parallel, placebo-controlled, double-blind study. Patients inhaled a low dose of house dust mite allergen for 10 subsequent working days (Days 1-5 and 8-12) and/or were subsequently infected with RV16 (Days 15 and 16). Allergen exposure resulted in a significant fall in FEV1 (p < 0.001) and provocative concentration of histamine causing a 20% fall in FEV1 (p < 0.001) and an increase in exhaled nitric oxide (p < 0.001) and percentage of sputum eosinophils (p < 0.001). RV16 infection led to a fall in FEV1 (p = 0.02) and increases in the percentage of sputum neutrophils (p = 0.01), sputum interleukin-8 (p = 0.04), and neutrophil elastase (p = 0.04). Successive allergen exposure and RV16 infection had no synergistic or additive effect on any of the clinical or inflammatory outcomes. In conclusion, repeated low-dose allergen exposure and RV16 infection induce distinct inflammatory profiles within the airways in asthma without apparent interaction between these two environmental triggers. This suggests that preceding allergen exposure, at the used dose and duration, is not a determinant of the severity of RV-induced exacerbations in patients with mild to moderate asthma.

Rhinovirus-induced interferon-gamma and airway responsiveness in asthma

The majority of asthma exacerbations are caused by respiratory infections, with rhinovirus (RV) being the most common virus. Recent evidence has suggested that decreased generation of IFN-gamma is associated with more severe colds and delayed elimination of virus. Whether the generation of IFN-gamma also has any relationship to general features of asthma severity has yet to be determined. To evaluate this hypothesis, peripheral blood mononuclear cells from 19 subjects with atopy and asthma were incubated with RV16 for 6 days to determine IFN-gamma and interleukin (IL)-5 production; these responses were then compared with measurements of airflow obstruction and airway responsiveness. RV16-induced IFN-gamma production correlated significantly with the methacholine PD (r = 0.50, p = 0.03), and the ratio of RV16-induced IFN-gamma:IL-5 correlated with % predicted FEV1 (r = 0.53, p = 0.02). In contrast, there were no significant associations between measures of asthma severity and RV-induced IL-5. These findings suggest that a cytokine imbalance with a deficient Th1 response to RV, but not a Th2 response, is associated with measures of asthma severity and support the concept that impaired antiviral responses may be associated with asthma severity.

Age-related seasonal patterns of emergency department visits for acute asthma in an urban environment

STUDY OBJECTIVE

Asthma morbidity is greater in younger patients. The reasons are not fully understood, although identifying demographic patterns of seasonality may help determine causes and potential prevention. The objective of this study is to determine the relationship between age and seasonal asthma periodicity in patients presenting to the emergency department (ED).

METHODS

We conducted a retrospective study of ED visits from 1991 to 2000 in 11 municipal hospitals in New York City, with 911 receiving facilities. There were 673,141 patients who presented to the ED during the study period and had a primary diagnosis of acute asthma.

RESULTS

Distinct seasonal patterns were observed, with the highest number of visits occurring in the fall and the fewest in the summer. Seasonal fluctuations of ED visits were highest in children aged 13 years or younger (coefficient of variation [CV] 37.8%; 95% confidence interval [CI] 37.5% to 38.1%), with a peak in CV occurring at approximately age 7 years (CV 43.3%; 95% CI 43.0% to 43.6%). Less variability was noted with increasing age, and the population aged 30 years and older appeared to be the least susceptible to seasonal influences (CV 11.7%; 95% CI 11.3% to 12.1%). Although the total number of asthma visits decreased by more than 30% from 1991 to 2000, the CVs for each year remained within a relatively narrow range of 24.2% to 30.5%.

CONCLUSION

In an urban population, seasonal variability of asthma episodes requiring ED visits are closely linked to age, which may be important in understanding the causes of asthma and developing disease-management strategies for the prevention of asthma episodes.

Mouse respiratory epithelial cells support efficient replication of human rhinovirus

Human rhinoviruses (HRV) are responsible for the majority of virus infections of the upper respiratory tract. Furthermore, HRV infection is associated with acute exacerbation of asthma and other chronic respiratory diseases of the lower respiratory tract. A small animal model of HRV-induced disease is required for the development of new therapies. However, existing mouse models of HRV infection are difficult to work with and until recently mouse cell lines were thought to be generally non-permissive for HRV replication in vitro. In this report we demonstrate that a virus of the minor receptor group, HRV1B, can infect and replicate in a mouse respiratory epithelial cell line (LA-4) more efficiently than in a mouse fibroblast cell line (L). The major receptor group virus HRV16 requires human intercellular adhesion molecule-1 (ICAM-1) for cell entry and therefore cannot infect LA-4 cells. However, transfection of in vitro-transcribed HRV16 RNA resulted in the replication of viral RNA and production of infectious virus. Expression of a chimeric ICAM-1 molecule, comprising mouse ICAM-1 with extracellular domains 1 and 2 replaced by the equivalent human domains, rendered the otherwise non-permissive mouse respiratory epithelial cell line susceptible to entry and efficient replication of HRV16. These observations suggest that the development of mouse models of respiratory tract infection by major as well as minor group HRV should be pursued.

CD8+ T cells and immunoregulatory networks in asthma

It is well established that infection with respiratory viruses can cause acute local inflammation in humans and is a leading cause in the hospitalization of asthmatics. Less well recognized is the potential for viral infections to actually protect against the development of asthma, as are the cellular mechanisms which might underlie such protection. This review outlines the basic immunological pathways involved in atopic asthma and details the currently recognized cellular mechanisms induced by respiratory viral infections which can protect against the development of asthma. Specifically, it appears that virus infection induced memory T cells that remain in tissues, e.g. the lung and airways, can under certain circumstances create a local cytokine milieu which inhibits the development of ensuing allergic immune responses at that site. One key aspect of this immune modulation is the cytokine-dependent communication which occurs between the innate and the adaptive immune systems. The mechanistic principles underlying this form of immunomodulation should be taken into consideration when developing future forms of therapy and rational vaccine design.

Predominance of rhinovirus in the nose of symptomatic and asymptomatic infants

Respiratory infections in infancy may protect against developing Th2-mediated allergic disease (hygiene hypothesis). To estimate the relative contribution of particular viruses to the development of the immune system and allergic disease, we investigated longitudinally the prevalence of respiratory viral infections in infants. One hundred and twenty-six healthy infants were included in this prospective birth cohort study in their first year of life. Physical examination was performed and nasal brush samples were taken during routine visits every 6 months and during an upper respiratory tract infection (URTI) (sick visits). The prevalence of respiratory viral infections in infants with URTI, infants with rhinitis without general malaise and infants without nasal symptoms was studied. Rhinovirus was the most prevalent pathogen during URTI and rhinitis in 0- to 2-year-old infants ( approximately 40%). During URTI, also respiratory syncytial virus ( approximately 20%) and coronavirus ( approximately 10%) infections were found, which were rarely detected in infants with rhinitis. Surprisingly, in 20% of infants who did not present with nasal symptoms, rhinovirus infections were also detected. During routine visits at 12 months, a higher prevalence of rhinovirus infections was found in infants who attended day-care compared with those who did not. We did not observe a relation between breast-feeding or smoking by one or both parents and the prevalence of rhinovirus infections. The parental history of atopy was not related to the prevalence of rhinovirus infection, indicating that the genetic risk of allergic disease does not seem to increase the chance of rhinovirus infections. In conclusion, rhinovirus infection is the most prevalent respiratory viral infection in infants. It may therefore affect the maturation of the immune system and the development of allergic disease considerably.

Serum and low-density lipoprotein enhance interleukin-8 secretion by airway epithelial cells

Viral respiratory infections rapidly increase vascular permeability, which leads to the transudation of serum proteins into airway secretions and tissues. To determine whether this process activates airway epithelial cells, bronchial epithelial cells were incubated with serum, and interleukin (IL)-8 secretion and gene expression were examined. As little as 0.1% serum significantly enhanced IL-8 secretion, and maximal secretion (65 +/- 4 ng/ml, 48 h) was observed with 10% serum. Low-density lipoprotein, but not albumin or immunoglobulin G, augmented bronchial epithelial IL-8 secretion, which was partially blocked by a monoclonal antibody specific for the low-density lipoprotein receptor. The IL-8-inducing activity of plasma was also augmented by clotting and platelet activation. Mechanistically, serum activated nuclear factor-kappaB and increased the stability and steady state levels of IL-8 mRNA. In summary, specific components of serum are potent activators of IL-8 mRNA and secretion, and the increased IL-8 production is likely to be a result of both increased transcription and mRNA stability. This effect may represent an innate mechanism for the recruitment of neutrophils to the airway in response to noxious stimuli, such as viral infections, that increase vascular permeability.

Rhinovirus and asthma

Rhinoviruses (RVs) cause the majority of common colds, which often provoke wheezing in patients with asthma. The precise mechanisms responsible for the RV infection-induced exacerbations of bronchial asthma are still uncertain. However, several reports reveal airway hyperresponsiveness, increases in chemical mediators in airway secretions such as kinin and histamine, and airway inflammation in patients with bronchial asthma after RV infection. RV infection induces an accumulation of inflammatory cells in airway mucosa and submucosa including neutrophils, lymphocytes and eosinophils. RV affects the barrier function of airway epithelial cells, and activates the airway epithelial cells and other cells in the lung to produce pro-inflammatory cytokines, including various kinds of interleukins, GM-CSF and RANTES, and histamine. RV also stimulates the expression of intercellular adhesion molecule-1 (ICAM-1) and low-density lipoprotein receptors in the airway epithelium, receptors for major and minor RVs. On the other hand, RV infection is inhibited by treatment with soluble ICAM-1, and by reduction of ICAM-1 expression in the airway epithelial cells after treatment with erythromycin. Both soluble ICAM-1 and erythromycin were reported to reduce the frequency of common colds. Here, we review the pathogenesis and management of RV infection-induced exacerbation of bronchial asthma.

Increased circulating 92 kDa matrix metalloproteinase (MMP-9) activity in exacerbations of asthma

BACKGROUND

The 72 kDa matrix metalloproteinase 2 (MMP-2) and the 92 kDa matrix metalloproteinase 9 (MMP-9) are type IV collagenases implicated in various aspects of inflammation including accumulation of inflammatory cells, tissue injury, and development of remodelling. The role of these enzymes in the pathogenesis of asthma exacerbations is unknown.

METHODS

Circulating levels of MMP-2 and MMP-9 proteins and the expression of their inhibitor, tissue inhibitor of metalloproteinase 1 (TIMP-1), were measured in 21 patients experiencing an asthma exacerbation and 21 age matched patients with stable asthma. Circulating gelatinolytic activity was compared during the asthma exacerbation and during subsequent convalescence by gelatin zymography in the same individuals. In addition, MMP-9 specific activity was quantified with a colorimetric assay which uses an artificial proenzyme containing a specific domain recognised by MMP-9 in the same paired samples.

RESULTS

A significant increase in the circulating level of MMP-9 was seen in patients with an asthma exacerbation compared with patients with stable asthma (202.9 (22.0) v 107.7 (9.9) ng/ml, p=0.0003). There were no significant differences in the circulating levels of MMP-2 or TIMP-1. Gelatin zymography identified two major circulating gelatinolytic activities corresponding to MMP-2 and MMP-9, and showed that asthma exacerbations are characterised by markedly increased MMP-9 activity with no significant change in MMP-2 activity compared with the activities during convalescence in the same individuals. Direct measurement showed that MMP-9 specific activity is significantly increased during asthma exacerbations compared with subsequent convalescence (269.6 (31.7) v 170.4 (12.6) ng/ml, p=0.0099).

CONCLUSIONS

Asthma exacerbations are characterised by increased circulating MMP-9 activity. This increased activity may be related to exaggerated airway inflammation and airway remodelling.

Epidemiology of respiratory viruses in patients hospitalized with near-fatal asthma, acute exacerbations of asthma, or chronic obstructive pulmonary disease

PURPOSE

We compared the prevalence and spectrum of common respiratory viruses among patients with near-fatal asthma, acute exacerbations of asthma, or chronic obstructive pulmonary disease (COPD), and the relation of these findings to acute respiratory symptoms.

METHODS

We obtained adequate samples of respiratory secretions from 17 patients hospitalized with near-fatal asthma, 29 with acute asthma, and 14 with COPD. We used a polymerase chain reaction-based method to test for six common respiratory viruses in samples from endotracheal tube aspirates from patients with near-fatal asthma, and from induced sputum specimens from patients with acute asthma or COPD. Respiratory symptoms (runny nose, sore throat, fever, chills, malaise, and cough) were recorded. Quiescent-phase induced sputum specimens were examined from patients who were initially virus positive.

RESULTS

Viral nucleic acids were detected in 52% (31/60) of acute-phase specimens and 7% (2/29) of quiescent-phase specimens examined (P <0.001), with similar proportions of virus-positive patients during the acute phase in the three groups: 59% (10/17) of those with near-fatal asthma, 41% (12/29) with acute asthma, and 64% (9/14) with COPD. Picornavirus (47% [n = 8]) and adenovirus (24% [n = 4]) were most commonly identified in near-fatal asthma, whereas influenza virus (36% [n = 5]) predominated in COPD. Virus-positive patients had a significantly increased frequency of runny nose, sore throat, fever, chills, and malaise (odds ratio = 4.1 to 18; P = 0.02 to 0.001).

CONCLUSION

Respiratory viruses are associated with hospitalizations for near-fatal asthma, acute asthma, and COPD, with some differences in the spectrum of viruses involved in the different groups of patients. Respiratory viruses are a target for the prevention and perhaps the treatment of these conditions.

Respiratory virus infections in cystic fibrosis

Respiratory virus infections have pronounced and long-lasting effects on patients with cystic fibrosis (CF), resulting in significant declines in FVC, FEV(1) and Shwachman score, significantly increasing both the frequency and duration of hospitalisation. Deleterious effects on patients with CF have been reported for most viruses studied but the effects of respiratory syncytial virus and influenza appear the greatest. There is circumstantial evidence that respiratory virus infections may facilitate bacterial infections, particularly Pseudomonas aeruginosa.

Virus infections, wheeze and asthma

Viral infections are the most frequent triggers of wheeze and asthma and yet their role in the development of symptoms remains controversial. Pre-existing airway abnormalities contribute to early virus-induced symptoms which usually remit in early childhood, whereas an interaction with airway inflammation causes exacerbations in asthma. However, the distinction between these two groups and the reason why some but not other children wheeze with viral infections is still debated. The effect of early infections on the developing immune system is also complex. The successful maturation of the T-cell response from a predominantly type 2 (atopic predisposition) at birth to a predominantly type 1 (optimal viral immunity) response, is influenced by genetic factors and the number of infections, as both are known to affect outcome. The relative parts played by predisposition and immunomodulation by early infections in later development of asthma are still controversial. These contentions are gradually being resolved by detailed prospective studies.

Virus infections, wheeze and asthma

Viral infections are the most frequent triggers of wheeze and asthma and yet their role in the development of symptoms remains controversial. Pre-existing airway abnormalities contribute to early virus-induced symptoms which usually remit in early childhood, whereas an interaction with airway inflammation causes exacerbations in asthma. However, the distinction between these two groups and the reason why some but not other children wheeze with viral infections is still debated. The effect of early infections on the developing immune system is also complex. The successful maturation of the T-cell response from a predominantly type 2 (atopic predisposition) at birth to a predominantly type 1 (optimal viral immunity) response, is influenced by genetic factors and the number of infections, as both are known to affect outcome. The relative parts played by predisposition and immunomodulation by early infections in later development of asthma are still controversial. These contentions are gradually being resolved by detailed prospective studies.