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

Respiratory viruses, symptoms, and inflammatory markers in acute exacerbations and stable chronic obstructive pulmonary disease

The effects of respiratory viral infection on the time course of chronic obstructive pulmonary disease (COPD) exacerbation were examined by monitoring changes in systemic inflammatory markers in stable COPD and at exacerbation. Eighty-three patients with COPD (mean [SD] age, 66.6 [7.1] yr, FEV(1), 1.06 [0.61] L) recorded daily peak expiratory flow rate and any increases in respiratory symptoms. Nasal samples and blood were taken for respiratory virus detection by culture, polymerase chain reaction, and serology, and plasma fibrinogen and serum interleukin-6 (IL-6) were determined at stable baseline and exacerbation. Sixty-four percent of exacerbations were associated with a cold occurring up to 18 d before exacerbation. Seventy-seven viruses (39 [58.2%] rhinoviruses) were detected in 66 (39.2%) of 168 COPD exacerbations in 53 (64%) patients. Viral exacerbations were associated with frequent exacerbators, colds with increased dyspnea, a higher total symptom count at presentation, a longer median symptom recovery period of 13 d, and a tendency toward higher plasma fibrinogen and serum IL-6 levels. Non-respiratory syncytial virus (RSV) respiratory viruses were detected in 11 (16%), and RSV in 16 (23.5%), of 68 stable COPD patients, with RSV detection associated with higher inflammatory marker levels. Respiratory virus infections are associated with more severe and frequent exacerbations, and may cause chronic infection in COPD. Prevention and early treatment of viral infections may lead to a decreased exacerbation frequency and morbidity associated with COPD.

Relationship between asthma medication and antibiotic use

STUDY OBJECTIVES

Increasing morbidity due to asthma and antimicrobial resistance among human pathogens are both major public-health concerns. Numerous studies describe the overuse of antibiotics in general populations and underuse of anti-inflammatory medications by asthmatic patients. However, little is known about the relationship between asthma medication and antibiotic use in asthmatics. Specifically, we tested the hypothesis that higher use of bronchodilator and anti-inflammatory medication by asthmatics, as a marker of problematic asthma, is associated with greater antibiotic use. We also test the hypothesis that physicians who are low prescribers of anti-inflammatory medications are high prescribers of antibiotics.

DESIGN

We conducted a retrospective cohort study evaluating asthma medication and antibiotic use by children and adults with asthma and the prescribing of these medications by primary-care physicians.

SETTING/PATIENTS

Subjects were continuously enrolled asthma patients aged 6 to 55 years receiving care in an urban, group-model, health maintenance organization.

INTERVENTIONS

None.

MEASUREMENT AND RESULTS

Main outcome measures were (1) antibiotic use by asthmatics stratified by low, moderate, and high bronchodilator use; (2) antibiotic use by asthmatics stratified by no, intermittent, and long-term anti-inflammatory use; and (3) correlation between physician-level anti-inflammatory agent to bronchodilator ratio (AIF:BD) and their rate of antibiotic prescribing. We found that (1) high bronchodilator users received 1.72 antibiotics per person-year (95% confidence interval [CI], 1.62 to 1.83), whereas low bronchodilator users received 1.23 antibiotics per person-year (95% CI, 1.19 to 1.27; p < 0.0001); (2) long-term users of anti-inflammatory agents received 1.85 antibiotics per person-year (95% CI, 1.76 to 1.95), whereas those not receiving an anti-inflammatory agent received 0.95 antibiotics per person-year (95% CI, 0.90 to 1.00; p < 0.0001); and (3) despite variations in physician AIF:BDs and antibiotic prescribing, respectively, these measures were not correlated.

CONCLUSIONS

Antibiotic use and asthma medication use are positively associated in a cohort of asthma patients. Greater effort is needed to define the appropriate role of antibiotics in asthma management.

Income-based drug benefit policy: impact on receipt of inhaled corticosteroid prescriptions by Manitoba children with asthma

BACKGROUND

Drug benefit policies are an important determinant of a population's use of prescription drugs. This study was undertaken to determine whether a change in a provincial drug benefit policy, from a fixed deductible and copayment system to an income-based deductible system, resulted in changes in receipt of prescriptions for inhaled corticosteroids by Manitoba children with asthma.

METHODS

Using Manitoba's health care administrative databases, we identified a population-based cohort of 10,703 school-aged children who met our case definition for asthma treatment before and after the province's drug benefit policy was changed in April 1996. The effects of the program change on the probability of receiving a prescription for an inhaled corticosteroid and on the mean number of inhaled corticosteroid doses dispensed were compared between a group of children insured under other drug programs (the comparison group) and 2 groups of children insured under the deductible program: those living in low-income neighbourhoods and those living in higher-income neighbourhoods. All analyses were adjusted for a measure of asthma severity.

RESULTS

For higher-income children with severe asthma who were covered by the deductible program, the probability of receiving an inhaled corticosteroid prescription and the mean annual number of inhaled corticosteroid doses declined after the change to the drug policy. A trend toward a decrease in receipt of prescriptions was also observed for low-income children, but receipt of prescriptions was unaltered in the comparison group. Before the policy change, among children with severe asthma, the mean annual number of inhaled corticosteroid doses was lowest for low-income children, and this pattern persisted after the change. Among children with mild to moderate asthma, those covered by the deductible program (both low income and higher income) were less likely to receive prescriptions for inhaled corticosteroids than those in the comparison group, and this difference was statistically significant for the higher-income children.

INTERPRETATION

The change to an income-based drug benefit policy was associated with a decrease in the use of inhaled corticosteroids by higher-income children with severe asthma and did not improve use of these drugs by low-income children.

Respiratory illness caused by picornavirus infection: a review of clinical outcomes

BACKGROUND

Respiratory infections result from invasion of the respiratory tract, mainly by viruses, and are the leading cause of acute morbidity in individuals of all ages worldwide. During peak season, picornaviruses cause 82% of all episodes of acute nasopharyngitis (the common cold), the most frequent manifestation of acute respiratory infection, and produce more restriction of activity and physician consultations annually than any other viral or bacterial source of respiratory illness.

OBJECTIVE

This article reviews the clinical impact and outcomes of picornavirus-induced respiratory infections in specific populations at risk for complications. It also discusses the potential economic impact of the morbidity associated with picornavirus-induced respiratory infection.

METHODS

Relevant literature was identified through searches of MEDLINE, OVID, International Pharmaceutical Abstracts, and Lexis-Nexis. The search terms used were picornavirus, rhinovirus, enterovirus, viral respiratory infection, upper respiratory infection, disease burden, economic, cost, complications, asthma, COPD, immunocompromised, elderly otitis media, and sinusitis. Additional publications were identified from the reference lists of the retrieved articles.

CONCLUSIONS

Based on the clinical literature, picornavirus infections are associated with severe morbidity as well as considerable economic and societal costs. Future research should focus on identifying patterns of illness and the costs associated with management of these infections. New treatments should be assessed not only in terms of their ability to produce the desired clinical outcome, but also in terms of their ability to reduce the burden of disease, decrease health care costs, and improve productivity.

Environmental tobacco smoke as a risk factor for respiratory disease in children

Respiratory diseases are a frequent reason for using health care. In 1995-1996, diseases of the respiratory tract (ICD 460-519) contributed seven of the top 15 reasons for visits to physician offices among children under 15 years of age in the United States. Environmental tobacco smoke (ETS) is a wide-spread environmental pollutant that has been long linked with respiratory problems. This paper will review the available literature on the role ETS plays in respiratory diseases, including asthma. This review focuses not only on the respiratory problems caused by ETS, but also examines the influence of age at exposure on the consequences of ETS and the importance of the differing sources of ETS exposure. As ETS is a completely preventable form of environmental pollution, the success or failure of various types of interventions will also be reviewed.

Prolonged nasal eosinophilia in allergic patients after common cold

BACKGROUND

Viral respiratory tract infections may cause both harmless common colds and severe asthma exacerbations; the differences in disease expression probably depend on the allergic status of the patient. To determine whether altered immunologic mechanisms underlie these differences, we investigated nasal inflammation during naturally acquired common cold.

METHODS

In a group of 16 patients (eight allergic), nasal brush samples were taken, and nasal symptoms were recorded during common cold, 2 weeks later (convalescence), and at baseline (>4 weeks without nasal symptoms). Nasal brush cells were stained immunohistochemically for Langerhans cells, T cells, monocytes, neutrophils, B cells, macrophages, natural killer (NK) cells, mast cells, eosinophils, eotaxin, and RANTES.

RESULTS

Four rhinovirus, four coronavirus, three RSV, one Mycoplasma pneumoniae, and one influenza A/enterovirus double infection were confirmed. Increased numbers of T cells, monocytes, macrophages, NK cells, eosinophils, and RANTES- and eotaxin-positive cells, but not neutrophils, were observed during common cold in allergic and nonallergic patients, and increased numbers of mast cells in allergic patients. Compared to nonallergic patients, in allergic patients eosinophil influx persisted into convalescence.

CONCLUSION

Prolonged nasal eosinophil influx was observed in allergic patients after common cold. What immunologic factors can induce prolonged eosinophil influx and whether this may increase the risk of subsequent allergen-induced hypersensitivity reactions must be studied further.

Outcome of asthma in children and adolescents at a specialty-based care program

BACKGROUND

Asthma remains a major cause of morbidity for children despite national guidelines.

OBJECTIVE

To evaluate outcome from a structured specialty-based care program.

METHODS

Comparison of previous and subsequent years for children ranging from infancy to adolescence who entered a specialty clinic program at a university hospital serving a widely dispersed patient population. One hundred fifty-seven patients previously receiving primary care for their respiratory symptoms were seen during the study period; 23 were lost to followup, 15 were excluded because of other serious concurrent medical problems, and 119 were available for outcome analysis. Evaluation included historical data base from a structured interview, evaluation of pulmonary physiology, and allergy skin testing. Treatment decisions were evidence-based. Patient and/or family education was targeted at decision-making. Toll-free telephone access to the specialty service was provided around the clock. Frequency of unscheduled medical care, hospitalizations, sleep disturbance, activity interference, attainment of defined criteria for control, and medication use were quantified.

RESULTS

Seven hundred thirty-five acute care visits were reduced to 47, and 99 hospitalizations were decreased to 10 (P < 0.001 for both). Nocturnal symptoms and exercise limitation decreased significantly (P < 0.001 for both). All criteria for control of asthma were met in 89% of 75 without tobacco smoke exposure and 50% of 44 with exposure (P < 0.0001 for the difference in outcome). Frequent antibiotic use for respiratory symptoms were eliminated after entering the program. Maintenance medications were not used in 72 with an intermittent pattern of viral respiratory infection-induced asthma. Inhaled corticosteroid use increased from 38 to 68% among 47 subjects with a chronic pattern.

CONCLUSIONS

Morbidity from asthma is largely prevented with often less, but better selected, medication than had been occurring in previous primary care. These data have implications for revised guidelines directed at primary care physicians.

Murine cytomegalovirus infection alters Th1/Th2 cytokine expression, decreases airway eosinophilia, and enhances mucus production in allergic airway disease

Concomitant infection of murine CMV (MCMV), an opportunistic respiratory pathogen, altered Th1/Th2 cytokine expression, decreased bronchoalveolar lavage (BAL) fluid eosinophilia, and increased mucus production in a murine model of OVA-induced allergic airway disease. Although no change in the total number of leukocytes infiltrating the lung was observed between challenged and MCMV/challenged mice, the cellular profile differed dramatically. After 10 days of OVA-aerosol challenge, eosinophils comprised 64% of the total leukocyte population in BAL fluid from challenged mice compared with 11% in MCMV/challenged mice. Lymphocytes increased from 11% in challenged mice to 30% in MCMV/challenged mice, and this increase corresponded with an increase in the ratio of CD8(+) to CD4(+)TCRalphabeta lymphocytes. The decline in BAL fluid eosinophilia was associated with a change in local Th1/Th2 cytokine profiles. Enhanced levels of IL-4, IL-5, IL-10, and IL-13 were detected in lung tissue from challenged mice by RNase protection assays. In contrast, MCMV/challenged mice transiently expressed elevated levels of IFN-gamma and IL-10 mRNAs, as well as decreased levels of IL-4, IL-5, and IL-13 mRNAs. Elevated levels of IFN-gamma and reduced levels of IL-5 were also demonstrated in BAL fluid from MCMV/challenged mice. Histological evaluation of lung sections revealed extensive mucus plugging and epithelial cell hypertrophy/hyperplasia only in MCMV/challenged mice. Interestingly, the development of airway hyperresponsiveness was observed in challenged mice, not MCMV/challenged mice. Thus, MCMV infection can modulate allergic airway inflammation, and these findings suggest that enhanced mucus production may occur independently of BAL fluid eosinophilia.

Long-term cetirizine treatment reduces allergic symptoms and drug prescriptions in children with mite allergy

BACKGROUND

Experimental data demonstrate that mite allergy is characterized by persistent chronic inflammation, even during asymptomatic periods. This suggests that long-term continuous treatment be included in the global strategy of allergy treatment.

OBJECTIVE

We conducted a study to evaluate whether regularly administered cetirizine reduces allergic symptoms and drug prescriptions in children with mite allergy.

METHODS

In this double-blind, randomized, placebo-controlled study, two parallel groups of 10 children with mite allergy (mean age: 6.5 years) received either cetirizine or placebo daily for 6 months. Participants were allowed to take rescue medications for rhinitis and/or mild asthma. The symptoms (nasal itching, sneezing, obstruction, rhinorrhea, conjunctival itching, lacrimation, conjunctival hyperemia, cough, wheezing, and chest tightness) were recorded on a diary card. The intake of cetirizine (as additional symptomatic treatment), antibiotics, acetaminophen, beta2-agonists, inhaled and systemic corticosteroids was also recorded.

RESULTS

Symptom scores and drug consumption were significantly lower (P < 0.05) in the cetrizine-treated group versus the placebo group. The greatest reductions were in cetirizine itself, inhaled corticosteroids, beta2-agonists, and antibiotics. No side effects were reported in either group.

CONCLUSIONS

In mite-allergic children, cetirizine administered daily for prolonged periods decreases symptoms of and drug prescriptions for allergic rhinitis and asthma compared with symptomatic treatment.

Increased lymphoid MxA expression in acute asthma exacerbation in children

BACKGROUND

Although the association between acute asthma exacerbation and viral infection has been well documented, virus identification rates vary. It has recently been reported that the expression of MxA protein in lymphocytes, inducible by type I interferons, can serve as a sensitive marker for viral infection in the host. The objective was to determine the contribution of viral infection to precipitation of asthma attacks in children.

METHODS

We studied 186 asthmatic children, aged 0-12 years, over a 1-year period to evaluate MxA protein levels in peripheral blood lymphocytes by using a flow cytometric analysis in whole blood.

RESULTS

Of all the subjects, 80 (47%) exhibited significantly elevated levels of MxA expression in lymphocytes, presumably indicating the states of viral infection. The association of viral infections with acute asthma exacerbation seemed to be marked in younger children: enhanced MxA expression was seen in 73.3% of infants (aged 0-1 year), 49.5% of toddlers (aged 2-5 years), and 26% of schoolchildren (aged 6-12 years). Seasonal changes in the frequency of viral infection associated with deterioration were also observed.

CONCLUSIONS

Flow cytometric assay of MxA protein expression in whole blood appears to be an easy and useful method to evaluate viral infections in acute asthma exacerbation.

Effect of oromucosal administration of IFN-alpha on allergic sensitization and the hypersensitive inflammatory response in animals sensitized to ragweed pollen

Oromucosal (o.m.) administration of interferon-alpha (IFN-alpha) during either allergic sensitization (days 0-6) or the hypersensitive response (days 11 and 12) or both periods caused a dose-dependent reduction in allergen-specific IgE production and allergen-induced eosinophil recruitment in mice sensitized to ragweed pollen, a common allergen in humans. Treatment during the hypersensitive response period alone appeared to be most effective. Oromucosal treatment was as effective as intraperitoneal (i.p.) treatment, with maximum inhibition of both allergen-specific IgE production and allergen-induced eosinophil recruitment observed at a dose of a 1000 IU IFN-alpha. Treatment of animals with up to 10(5) IU murine IFN-alpha/beta (MuIFN-alpha/beta) by either the om. or i.p. route did not inhibit significantly allergen-specific IgG production, which may even have been increased at certain doses of IFN. Treatment of animals with up to 10(5) IU MuIFN-alpha/beta by either the o.m. or i.p. route did not affect significantly total serum IgE or IgG levels. Oromucosal administration of IFN-alpha reduced allergen-specific IgE production and allergen-induced eosinophil recruitment in the absence of detectable toxicity, the induction of H(2) antigen expression, and 2',5'-oligoadenylate synthetase activity associated with parenteral administration of IFN-alpha and thus may find application for the treatment of asthma and associated viral infections.

Effect of desloratadine and loratadine on rhinovirus-induced intercellular adhesion molecule 1 upregulation and promoter activation in respiratory epithelial cells

BACKGROUND

Rhinoviruses have been recently associated with the majority of asthma exacerbations for which current therapy is inadequate. Intercellular adhesion molecule 1 (ICAM-1) has a central role in airway inflammation in asthma, and it is the receptor for 90% of rhinoviruses. Rhinovirus infection of airway epithelium induces ICAM-1. Desloratadine and loratadine are compounds belonging to the new class of H(1)-receptor blockers. Anti-inflammatory properties of antihistamines have been recently documented, although the underlying molecular mechanisms are not completely defined.

OBJECTIVE

We have investigated the effects of desloratadine and loratadine on rhinovirus-induced ICAM-1 expression, mRNA upregulation, and promoter activation.

METHODS

Cultured primary bronchial or transformed (A549) respiratory epithelial cells were pretreated with desloratadine and loratadine for 16 hours and infected with rhinovirus type 16 for 8 hours. ICAM-1 surface expression was evaluated with flow cytometry, and ICAM-1 mRNA was evaluated with specific RT-PCR. In A549 cells promoter activation was evaluated with a chloramphenicol acetyltransferase assay, and binding activity of nuclear factor kappa B in nuclear extracts was evaluated with an electrophoretic mobility shift assay.

RESULTS

Desloratadine and loratadine (0.1-10 micromol/L) inhibited rhinovirus-induced ICAM-1 upregulation in both primary bronchial or transformed (A549) respiratory epithelial cells. In A549 cells the 2 compounds showed a dose-dependent inhibition with similar efficacy (inhibitory concentration of 50%, 1 micromol/L). Desloratadine and loratadine also inhibited ICAM-1 mRNA induction caused by rhinovirus infection in a dose-dependent manner, and they completely inhibited rhinovirus-induced ICAM-1 promoter activation. Desloratadine also inhibited rhinovirus-induced nuclear factor kappa B activation. Desloratadine and loratadine had no direct effect on rhinovirus infectivity and replication in cultured epithelial cells.

CONCLUSION

These effects are unlikely to be mediated by H(1)-receptor antagonism and suggest a novel mechanism of action that may be important for the therapeutic control of virus-induced asthma exacerbations.

A model of viral wheeze in nonasthmatic adults: symptoms and physiology

Episodic wheezing associated with viral infections of the upper respiratory tract (URT) is a common problem in young children but also occurs in adults. It is hypothesized that an experimental infection with human coronavirus (HCoV), the second most prevalent common cold virus, would cause lower respiratory tract (LRT) changes in adults with a history of viral wheeze. Twenty-four viral wheezers (15 atopic) and 19 controls (seven atopic) were inoculated with HCoV 229E and monitored for the development of symptoms, changes in airway physiology and provocative concentration of methacholine causing a 20% fall in forced expiratory volume in one second (FEV1) (PC20). At baseline, viral wheezers were similar to controls in PC20 (mean+/-SD log2PC20: 5.1+/-1.9 and 5.8+/-1.4 g x L(-1), respectively) but had a lower FEV1 than controls (mean+/-SD 85.8+/-11.4 and 95.6+/-13.2% predicted, respectively p < 0.05). Nineteen viral wheezers and 11 controls developed colds. Viral wheezers with colds reported significantly more URT symptoms than controls (median scores (interquartile range): 24 (10-37) and 6 (4-15), respectively p = 0.014). Sixteen viral wheezers and no controls reported LRT symptoms (wheeze, chest tightness and shortness of breath). The viral wheezers with colds had small (3-4%) reductions in FEV1 and peak expiratory flow on days with LRT symptoms (days 3-6), but a progressive reduction in PC20 from baseline on days 2, 4 and 17 after inoculation (by 0.82, 1.35 and 1.82 doubling concentrations, respectively). The fall in PC20 affected both atopic and nonatopic subjects equally. There were no changes in FEV1 or PC20 in controls. An adult model of viral wheeze that is independent of atopy and therefore, of classical atopic asthma was established.

Pathophysiological mechanisms of asthma. Application of cell and molecular biology techniques

Asthma is a common increasing and relapsing disease that is associated with genetic and environmental factors such as respiratory viruses and allergens. It causes significant morbidity and mortality. The changes occurring in the airways consist of a chronic eosinophilic and lymphocytic inflammation, together with epithelial and structural remodeling and proliferation, and altered matrix proteins, which underlie airway wall narrowing and bronchial hyperresponsiveness (BHR). Several inflammatory mediators released from inflammatory cells such as histamine and cysteinyl-leukotrienes induce bronchoconstriction, mucus production, plasma exudation, and BHR. Increased expression of T-helper 2 (Th2)-derived cytokines such as interleukin-4 and 5 (IL-4, 5) have been observed in the airway mucosa, and these may cause IgE production and terminal differentiation of eosinophils. Chemoattractant cytokines (chemokines) such as eotaxin may be responsible for the chemoattraction of eosinophils to the airways. The initiating events are unclear but may be genetically determined and may be linked to the development of a Th2-skewed allergen-specific immunological memory. The use of molecular biology techniques on tissues obtained from asthmatics is increasing our understanding of the pathophysiology of asthma. With the application of functional genomics and the ability to transfer or delete genes, important pathways underlying the cause if asthma will be unraveled. The important outcome of this is that new preventive and curative treatments may ensue.

Interleukin-1beta and rhinovirus sensitize adenylyl cyclase in human airway smooth-muscle cells

Rhinovirus (RV) is a major cause of wheezing in asthmatics and has been reported to cause beta2 adrenergic receptor hyporesponsiveness in human airway smooth muscle (HASM) via cellular secretion of interleukin (IL)-1beta. We studied the effects of IL-1beta and RV on cyclic adenosine monophosphate (cAMP) production in HASM cells. Chronic incubation with IL-1beta or RV caused a significant increase (approximately 3- and approximately 2-fold, respectively) in forskolin (FSK)-stimulated cAMP production, suggesting a sensitization of adenylyl cyclase (AC). The observed augmentation of FSK-stimulated cAMP formation by IL-1beta was completely abrogated by pretreatment with an IL-1 receptor antagonist or cycloheximide, demonstrating that the effect is mediated via the IL-1 receptor 1 (IL-1R1) and that de novo protein synthesis is required. In contrast, RV-induced AC sensitization was not mediated via the IL-1R1 but was observed to be protein kinase C-dependent. We suggest that the sensitization of AC observed after exposure to IL-1beta or RV infection is a cellular defense mechanism to promote pathways that induce relaxation in the inflamed airway.

Structure of the human M(2) muscarinic acetylcholine receptor gene and its promoter

The M(2) muscarinic receptor inhibits the release of acetylcholine from cholinergic fibers in the lungs and elsewhere. In airway parasympathetic neurons, M(2) receptor expression is decreased by viral infections and by interferon-gamma, increasing actylcholine release. Dexamethasone increases M(2) receptor expression, decreasing acetylcholine release. We carried out 5' rapid amplification of cDNA ends beginning with mRNA from human heart and IMR32 human neuroblastoma cells. This demonstrated a 5' UTR of 100 BP, corresponding to two sequences on chromosome 7, separated by a 22.6 kB intron. The splice acceptor site is at -45 relative to the initiating atg. The 3000 BP upstream of 5' RACE product were subcloned into a pGL3 luciferase reporter vector. Deletional constructs were expressed in IMR32 cells. These demonstrated that 412 BP provided full expression of the reporter gene, and suggested a repressor element between -1848 and -1510.

The association between respiratory viruses and symptoms in 2-week-old infants at high risk for asthma and allergy

OBJECTIVES

The role of viral respiratory tract infections in the onset of childhood asthma and allergy is controversial, partly because of limited understanding about postnatal viral exposures. We investigated the prevalence of 3 common respiratory viruses and associated respiratory symptoms in 2-week-old infants at high risk for having asthma and allergy.

STUDY DESIGN

Frozen nasal specimens from 2-week-old children at high risk (n = 495) underwent reverse transcription-polymerase chain reaction (RT-PCR) for picornavirus-, parainfluenza-, and respiratory syncytial virus-specific nucleic acid. RT-PCR findings were related to respiratory symptoms (cold, cough, and wheeze) and to characteristics implicated with increased risk for asthma and allergy.

RESULTS

Viral RT-PCR was positive in 199 (40.2%) of 495 specimens examined, with picornavirus and parainfluenza significantly associated with respiratory symptoms. Viral prevalence was significantly higher in children born during the winter and summer months.

CONCLUSIONS

A high percentage (40.2%) of infants at high risk for asthma and allergy had been exposed to common respiratory viruses at 2 weeks of age. RT-PCR is a powerful diagnostic method that can be used in epidemiologic studies examining the role of viral respiratory tract infections in the pathogenesis of pediatric asthma and allergy.

Bafilomycin A1inhibits rhinovirus infection in human airway epithelium: effects on endosome and ICAM-1

To examine the effects of bafilomycin A1, a blocker of vacuolar H+-ATPase, on rhinovirus (RV) infection in the airway epithelium, primary cultures of human tracheal epithelial cells were infected with RV14. Viral infection was confirmed by showing that viral RNA in the infected cells and the viral titers in the supernatants of infected cells increased with time. RV14 infection upregulated the production of cytokines and mRNA of intercellular adhesion molecule (ICAM)-1 in epithelial cells. Bafilomycin A1reduced the viral titers of RV14 and inhibited the production of cytokines and ICAM-1 before and after RV14 infection. Bafilomycin A1reduced susceptibility of epithelial cells to RV14 infection. RV14 increased activated nuclear factor-κB in the cells, and bafilomycin A1reduced the activated nuclear factor-κB. Bafilomycin A1decreased the number of acidic endosomes in the epithelial cells. These results suggest that bafilomycin A1may inhibit infection by RV14 by not only blocking RV RNA entry into the endosomes but also reducing ICAM-1 expression in the epithelial cells. Bafilomycin A1may therefore modulate airway inflammation after RV infection.

Nebulized budesonide after hospitalization for recurrent bronchial obstruction in children younger than 18 months

A multi-center, double-blind, randomized dose-response study was performed to assess the effect of 3 months of treatment with two different doses of inhaled nebulized budesonide in children with acute recurrent bronchial obstruction (BO) causing hospitalization. Steroid-naive children younger than 18 months were included when admitted to hospital because of BO for at least the second time, and were followed-up monthly for 15 months. Forty-five of 49 subjects (43 boys, 2 girls) (mean age 9.3 months upon inclusion) completed the study. Twenty-four patients (20 boys, 4 girls) received nebulized budesonide 0.5 mg twice daily for 1 month followed by 0.25 mg daily for the next 2 months, whereas 25 children received 0.1 mg twice daily throughout the 3-month treatment period. Outcome (number of BO episodes, time to first BO after start of treatment, and use of rescue medication), as well as height/length and weight, were assessed at the start of treatment and monthly for the following 3 months, as well as for 12 months after cessation of treatment (15 months in total). There was an overall tendency towards better symptom control (fewer episodes of acute BO during treatment and follow-up, fewer hospital visits because of acute BO, lower clinical score during follow-up, and less use of rescue medication during follow-up) in the high-dose treatment group vs. the low-dose treatment group. However, the differences did not reach statistical significance for any of the outcomes. The only significant difference in effect between the groups was fewer children in the high-dose group treated openly with nebulized budesonide during follow-up. Length/height and weight gain did not differ significantly between the two treatment groups throughout the study. There was no significant dose-dependent beneficial effect of 3 months of treatment with nebulized budesonide in infants and toddlers with at least two hospitalizations for acute bronchial obstruction.

The relationship between atopic status and IL-10 nasal lavage levels in the acute and persistent inflammatory response to upper respiratory tract infection

We examined the influence of atopy on virus-induced airway inflammation by comparing the nasal response to naturally acquired upper respiratory tract infection in atopic and nonatopic subjects by measurement of cytokine, chemokine, and mediator levels in nasal lavage from 44 adults (23 atopic) taken during the acute and the convalescent phases of the common cold. Nasal aspirates were examined for the presence of upper respiratory viruses by RT-PCR. In atopic and nonatopic subjects there were increased levels of IL-1beta, IL-6, IL-8, TNF-alpha, RANTES, sICAM-1, MPO, ECP, IL-10, and IFN-gamma in nasal lavage during the acute compared with the convalescent phase (p < 0.001). During the acute phase histamine levels were significantly higher in the atopic than in the nonatopic subjects (p < 0.05), whereas IL-10 levels were significantly greater in the nonatopic than in the atopic subjects (p < 0.05). At convalescence levels of IL-1beta, IL-6, sICAM-1, ECP, RANTES and albumin were significantly higher in the atopic group (p < 0.05). An upper respiratory tract virus was found in 27 volunteers (61%) during the acute stage and in two volunteers (4%) at convalescence. We conclude that virus-induced inflammatory changes within the nose are more prolonged in atopic than in nonatopic subjects and that this is associated with reduced IL-10 levels in atopic compared with nonatopic subjects during the acute phase of upper respiratory tract infection.

Seasonal variation in bronchial hyperreactivity (BHR) in allergic patients

As summarized in Table 1, the literature consistently supports the hypothesis that allergic asthmatic patients have seasonal BHR changes that parallel allergen exposure. These seasonal changes appear to be preventable by treatment with corticosteroids (systemic, inhaled, or nasal), disodium cromoglycate, and immunotherapy. Studies have almost exclusively focused on pollens, though similar limited data exist for dust mites. Though the dust mite is a perennial allergen, mite levels are well known to fluctuate with seasonal temperature and humidity trends (44-46), and therefore, seasonal BHR variation in mite-sensitive asthmatic patients is not surprising. Allergenic mold species have not been studied in this regard. In allergic rhinitis patients, the data are less consistent (see Table 2). However, the studies that failed to identify a seasonal BHR difference were either small or had other design limitations. The seasonal changes identified by the larger analyses were similar to those identified for asthmatic patients. Thus, although confirmatory studies would be helpful, it seems likely that in the absence of clinical asthma, allergic rhinitis patients with baseline BHR have allergen-related seasonal changes in BHR. The BHR effects of seasonal changes in air pollution and viral URIs are not known, since they have not yet been directly studied. However, interesting recent reports have identified possible synergistic effects of air pollution exposure on BHR and allergic responses. Similarly, the availability of new viral identification techniques has resulted in the discovery that viral infection may be more prevalent during clinical asthma exacerbation than previously realized. Therefore, air pollution and viral infections may well influence BHR seasonally, and (along with allergens) may contribute to seasonal asthma morbidity and mortality peaks. The mechanism(s) underlying seasonal BHR changes is (are) not known. One plausible possibility with regard to allergen-driven BHR changes involves a type I hypersensitivity late-phase reaction. Characterized by recruitment of eosinophils, lymphocytes, and other cells that are central components of allergic inflammation and are not normally found in the lower airways, this reversible inflammatory process could in turn act, presumably via chemical mediators, on the airway smooth muscle. This may cause bronchoconstriction, but may also increase responsiveness to bronchoconstrictive stimuli independent of bronchoconstriction. This explanation for seasonal BHR changes is supported by findings of blood eosinophil (31,47) and BAL eosinophilic cationic protein (31) level changes that parallel BHR. Prevention of seasonal BHR changes using anti-inflammatory medications (32,33,35) also supports this hypothesis (30) however, and the complex potential interactions between infectious agents and air pollutants on seasonal BHR changes have yet to be studied directly. Therefore, although BHR indeed may predictably vary season to season in allergic individuals, additional investigation is needed to better characterize the reasons for this phenomenon. Further insight in this area may help address the reasons why there are often seasonal epidemics in asthma morbidity and mortality.

Type 2 rhinovirus infection of cultured human tracheal epithelial cells: role of LDL receptor

To examine the role of the low-density lipoprotein (LDL) receptor on minor group human rhinovirus (RV) infection, primary cultures of human tracheal epithelial cells were infected with a minor group (RV2) or a major group (RV14) RV. Viral infection was confirmed by showing with PCR that viral titers in supernatants and lysates from infected cells increased with time. RV2 and RV14 increased expression of mRNA and protein of the LDL receptor on the cells and the cytokine production. RV2 induced activation of transcription factors SP1 and nuclear factor-kappaB (NF-kappaB). An antibody to the LDL receptor inhibited RV2 infection and RV2-induced cytokine production without an effect on RV14 infection and RV14-induced cytokine production. These findings imply that RV2 upregulates LDL receptor expression on airway epithelial cells, thereby increasing susceptibility to minor group RV infection. LDL receptor expression and cytokine production may be mediated, in part, via activation of transcription factors by RV2. These events may be important in airway inflammation after minor group RV infection in asthma.

Airflow limitation during respiratory syncytial virus lower respiratory tract infection predicts recurrent wheezing

BACKGROUND

Respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) is frequently followed by recurrent wheezing. Thus far no clinical risk factors have been identified to predict which infants will have wheezing episodes subsequent to RSV LRTI.

OBJECTIVE

To determine clinical predictors for airway morbidity after RSV LRTI.

METHODS

In a 1-year follow-up study we investigated the predictive value of auscultatory findings characteristic of airflow limitation (wheezing) during RSV LRTI for subsequent airway morbidity. Clinical characteristics, including the presence or absence of signs of airflow limitation, of hospitalized infants with RSV LRTI were prospectively recorded during 2 winter epidemics. During a 1-year follow-up period parents of 130 infants recorded daily airway symptoms.

OUTCOME MEASURE

Recurrent wheezing defined as > or = 2 episodes of wheezing.

RESULTS

Signs of airflow limitation during RSV LRTI were absent in 47 (36%) infants and present in 83 (64%) infants. Recurrent wheezing was recorded in 10 (21%) infants without signs of airflow limitation and in 51 (61%) with signs of airflow limitation during initial RSV LRTI (relative risk, 0.29, P < 0.001). In a multiple logistic regression model, airflow limitation during initial RSV LRTI proved independent from other clinical parameters, including age, parental history of asthma and smoke exposure.

CONCLUSIONS

A sign of airflow limitation during RSV LRTI is the first useful clinical predictor for subsequent recurrent wheezing.

Induction of type 2 activity in adult human CD8(+) T cells by repeated stimulation and IL-4

Repeated administration or chronic presence of antigen during CD4(+) T cell activation and a cytokine milieu enriched in IL-4 favour the generation and maintenance of a T(h)2 population. However, there is little data on how these factors affect adult human CD8(+) T cell functions. We established in vitro conditions to culture purified human CD8(+) T cells, and investigated how repeated stimulation and exogenous IL-4 modulated their functions. Repeated TCR-CD3 stimulation of CD8(+) T cells increased the number of CD25-, CD30- and CD40 ligand-expressing cells, and their capacity to secrete IL-4 and IL-5. In addition, repeatedly stimulated CD8(+) T cells had cytotoxic activity and provided help to resting B cells for IgE synthesis. The presence of exogenous IL-4 during repeated stimulation further increased the number of CD25(+) and CD30(+) CD8(+) T cells, up-regulated the number of IL-5(+) cells, and increased IL-5 levels released. These observations demonstrate that repeated TCR-CD3 stimulation of normal human CD8(+) T cells favoured the growth of cells with a type 2 phenotype and that this was further amplified by the presence of IL-4. These mechanisms may be important in virus-induced lung eosinophilic inflammation in healthy subjects and virus-induced exacerbations of asthma.

Respiratory infections and asthma

Clinical and experimental evidence suggests an important role for respiratory infections in the development of asthma attacks. Viral upper respiratory infections have been associated with 80% of asthma exacerbations in children and 50% of all asthma episodes in adults. Human rhinovirus has been implicated as the principal virus associated with asthma episodes. Separate studies indicate that atypical bacteria such as Chlamydia pneumoniae and Mycoplasma pneumoniae may precipitate asthma symptoms. Although not completely clarified, the intricate pathogenetic mechanisms by which viral infections promote asthma attacks have been extensively investigated in recent years. By contrast, it has not yet been established whether atypical bacterial infections are an epiphenomenon or a pathogenic event in asthma.

Eosinophil recruitment to the airway nerves

Increased vagal reflexes contribute to bronchoconstriction in asthma. Antigen challenge of sensitized animals induces vagal hyperresponsiveness. This review will discuss the evidence that eosinophils increase release of acetylcholine from the parasympathetic nerves. After antigen challenge, eosinophils are actively recruited to the airway nerves, possibly through expression of chemotactic substances and adhesion molecules by the nerves. Tachykinins acting on neurokinin 1 receptors activate the eosinophils. Activated eosinophils release eosinophil major basic protein (MBP), which is an endogenous antagonist for M2 muscarinic receptors. The M2 muscarinic receptors on the parasympathetic nerves in the lungs normally inhibit release of acetylcholine. When M2 receptors are blocked by MBP, acetylcholine release is increased, resulting in hyperresponsiveness. Neutralization of MBP with polyanionic substances restores M2 receptor function and eliminates hyperresponsiveness. Antibodies to MBP prevent M2 receptor dysfunction and hyperresponsiveness, as do antibodies to the adhesion molecule very late antigen 4, which prevent eosinophil migration. A low dose of dexamethasone, which does not affect total eosinophil influx into the lungs and airways, prevents eosinophils from clustering around the nerves and prevents antigen-induced M2 dysfunction and hyperresponsiveness. Furthermore, animal studies show that viral infections, which are important precipitants of asthma attacks, and exposure to air pollutants such as ozone can also activate airway eosinophils, leading to a chain of events similar to that seen after antigen challenge. Finally, a similar clustering of eosinophils around airway nerves, as well as release of MBP onto the nerves, is seen in fatal asthma, suggesting that similar mechanisms may be involved in human airway hyperresponsiveness.

Rhinovirus infection induces expression of type 2 nitric oxide synthase in human respiratory epithelial cells in vitro and in vivo

BACKGROUND

Human rhinovirus (HRV) infections are the predominant cause of the common cold and are associated with exacerbations of asthma. Nitric oxide (NO) may play an important role in host defense by means of its potent antiviral properties.

OBJECTIVE

We sought to determine whether epithelial expression of type 2 nitric oxide synthase (NOS 2), which produces NO, is induced on rhinovirus infection in vitro and in vivo.

METHODS

Primary cultures of human airway epithelial cells were infected with HRV-16, and NOS 2 mRNA expression was assessed by conventional and real-time RT-PCR and NOS 2 protein by using Western blot analysis. Human subjects were also infected with HRV-16 in vivo, and mRNA for NOS 2 was assessed in nasal epithelial scrapings obtained before and after infection.

RESULTS

NOS 2 mRNA levels increased within 8 hours after HRV-16 infection of cultured cells and remained elevated up to 48 hours after infection. NOS 2 protein was elevated at 24 hours. Induction of NOS 2 did not occur with UV-inactivated HRV-16 but could be reproduced by using double-stranded RNA, indicating that induction was dependent on viral replication. Increased NOS 2 expression was also observed in nasal epithelial scrapings during symptomatic colds.

CONCLUSION

Increased epithelial expression of NOS 2 mRNA occurs as part of the host response to HRV infection in vitro and in vivo. Given the antiviral effects of NO, we speculate that increased host production of NO may play an important role in host defense during HRV infections.

The treatment of rhinovirus infections: progress and potential

The common cold is an important illness both as a result of the economic impact of this common disease and because of the morbidity associated with the complications of the illness. Recent attempts to develop antiviral treatments for the common cold represent a substantial advance over previous efforts. Formidable barriers remain to be overcome, however, before any of these new products will be proven to be clinically useful. Recent advances in our understanding of the pathogenesis of common cold symptoms have provided insights into potential new targets for the treatment of this illness.

Eosinophil granule proteins and their role in disease

The eosinophil has a potent armory of proinflammatory mediators with considerable potential to initiate and sustain an inflammatory response. These include cytotoxic granule proteins, cytokines, chemokines, and lipid mediators. Eosinophils are considered important in the immune response to infection with helminthic parasitic worms. Incrementally increasing evidence supports a critical role for their proinflammatory activities in diverse human conditions, most notably in allergic diseases such as asthma. In these conditions severe tissue damage is a consequence of an inappropriate accumulation of eosinophils and the subsequent release of their highly toxic granule proteins. In addition, release of granule-associated products such as chemokines and cytokines at the sites of inflammation is likely to have significant paracrine and autocrine relevance. This review will update recent developments in understanding the role that eosinophil granule proteins play in human disease, particularly those of the respiratory tract.

The role of viruses in the induction and progression of asthma

Viral respiratory infections have been related to asthma in several ways. It is well established that viral common colds precipitate exacerbations of asthma. Severe bronchiolitis in early life is related to subsequent wheezing and therefore may represent a marker of susceptibility to asthma; alternatively, it could be involved in the initiation of the disease. Finally, it is possible that some infections may protect from the development of asthma and allergies by promoting a type-1 host response. However, whether respiratory or other viruses could mediate such a protective effect is debated. The design and implementation of novel anti- or proviral strategies targeting asthma depends on the resolution of these questions. This review presents current evidence on the epidemiologic correlations and proposed mechanisms for the involvement of viral infections in the development and progression of asthma.

[Childhood asthma and viral infection: interactions and therapeutic possibilities]

Rhinovirus infections are the main cause of wheezing in children and adults. Studies carried out with experimental infections report that at least in certain conditions, this infection may spread to the lower respiratory tract as the virus acts on the respiratory epithelium. In vitro experiments with cells from the immune system and lower respiratory tract suggest that the mechanisms of action are directly linked to the production of pro-inflammatory cytokines. Both in vivo and in vitro evidence shows that rhinoviruses may stimulate bronchial epithelial cells to produce cytokines and pro-inflammatory chemokines. They may also stimulate the cholinergic and non-cholinergic nervous system, increasing the production of ICAM-1 and may give rise to a T-lymphocyte non-specific response or to T-lymphocyte replication in direct relation with viral infection. In addition, greater production of cysteinyl leukotrienes has been observed in the secretions of patients with bronchospasm. Experimental infection with Rhinovirus increases clinical symptomatology and bronchial hyperreactivity. The latter is associated with increased eosinophils and cationic proteins in sputum. The above findings suggest that multiple cellular pathways are involved in the induction of exacerbations of asthma induced by the virus. In addition, the possible stimulating role of exposure to allergens in sensitized patients would also increase allergic inflammation. Because of the limited therapeutic efficacy of steroids in reducing exacerbations, new treatment strategies based on greater insight into the physiopathology of the role of viruses in asthma are needed.

Histopathology of fatal asthma: drowning in mucus

The recent development of PCR for the diagnosis of respiratory viral infection has highlighted the importance of these infections in acute exacerbations of asthma. Rhinoviruses are important in all age groups, but particularly over 1 yr, while the role of RSV in bronchiolitis and wheezing in infants has been reaffirmed. Recent studies using the same technique for the detection of C. pneumoniae suggest a high prevalence of chronic infection in asthmatic children, and that the immune response to this organism may play a pathological role. These studies now require confirmation with larger carefully controlled studies.

The burden of influenza illness in children with asthma and other chronic medical conditions

OBJECTIVE

Although influenza immunization is recommended for children with high-risk medical conditions, the majority of such children do not receive influenza vaccine. This study was designed to measure the burden of influenza among children with asthma and other chronic medical conditions.

STUDY DESIGN

We performed a retrospective cohort study of children younger than 15 years with medically treated asthma or other chronic medical conditions enrolled in the Tennessee Medicaid program from 1973 to 1993. We determined rates of hospitalization for acute cardiopulmonary disease, outpatient visits, and antibiotic courses throughout the year. Annual differences between event rates when influenza virus was circulating and event rates during winter months when there was no influenza in the community were used to calculate influenza-attributable morbidity.

RESULTS

Influenza accounted for an average of 19, 8, and 2 excess hospitalizations for cardiopulmonary disease yearly per 1000 high-risk children aged <1 year, 1 to <3 years, and 3 to <15 years, respectively. For every 1000 children, an estimated 120 to 200 outpatient visits and 65 to 140 antibiotic courses were attributable to influenza annually.

CONCLUSIONS

Children younger than 15 years with asthma and other chronic medical conditions experience substantial morbidity requiring inpatient and outpatient care during influenza season. More effective targeting of this population for annual influenza immunization is warranted.

Influence of ambient fungal spores on emergency visits for asthma to a regional children's hospital

The impact of ambient aeroallergens on morbidity from childhood asthma is largely unknown. To address this issue, we studied the association between daily emergency department visits for asthma to a children's hospital, and daily concentrations of both pollen grains and fungal spores during a 5-yr period between 1993 and 1997. Air pollution and meteorological data accounted for in the analyses included ozone, nitrogen dioxide, sulfur dioxide, sulfates, temperature, barometric pressure, and relative humidity. The daily number of asthma visits ranged from 0 to 36 per day with an average of 7.5. Fungal spores, but not pollen grains, were associated with visits (p < 0.05). The percentage increase associated with each group, independent of the others, was 1.9% (SE 0.9) for deuteromycetes, 4.1% (1.6) for basidiomycetes, 2.8% (1.0) for ascomycetes, and 8.8% for these spores combined. In summary, fungal spores account for a significant proportion of the asthma exacerbations in children that prompt an emergency department visit.

Pathophysiology of severe asthma

Although asthma affects nearly 8% of the adult population, most of these patients have mild-to-moderate disease that can be controlled with appropriate treatment. It is estimated, however, that 5% to 10% of patients with asthma have severe disease that is unresponsive to typical therapeutics, including corticosteroids. Because patients with severe asthma are disproportionately affected by their disease, in terms of both impaired lifestyle and health care costs, the National Heart, Lung, and Blood Institute sponsored a workshop on the pathogenesis of severe asthma. The goals of this workshop were to begin to define the characteristics of severe asthma. In these discussions, it was clear that many characteristics need to be considered in defining this phenotype of asthma, including symptoms, intensity of therapy (including administration of systemic corticosteroids), and impairment of lung function. Also discussed were potential mechanisms of severe asthma including the role of allergic diseases, which may play less of a role in severe asthma than in mild-to-moderate disease, and infections. A major limitation to control of severe asthma is the recalcitrant response of these patients to usual therapy including systemic corticosteroids; the potential of other therapies was reviewed. From these discussions, recommendations were made for future research needs to gain insights into a difficult therapeutic and possibly novel mechanistic area of asthma.

Personal exposure to nitrogen dioxide and risk of airflow obstruction in asthmatic children with upper respiratory infection

BACKGROUND

Several studies have linked air pollution by nitrogen dioxide (NO(2)) with increased hospital admissions for asthma in children. Exacerbations of asthma in children are often precipitated by upper respiratory infections. It is therefore possible that NO(2) increases the risk of airways obstruction when asthmatic children develop upper respiratory infections.

METHODS

To test this hypothesis a sample of 114 asthmatic children aged 7-12 years were followed for a total of up to 13 months. Probable upper respiratory infections were identified by consensus review of daily symptom diaries, and episodes of airways obstruction from serial records of peak expiratory flow (PEF). Personal exposures to NO(2) were measured with Palmes tubes that were changed weekly. Generalised estimating equations were used to assess the relative risk (RR) of an asthmatic exacerbation starting within seven days of an upper respiratory infection according to estimated NO(2) exposure during the one week period from two days before to four days after the onset of the infection.

RESULTS

The children were followed for an average of 34 weeks during which 318 upper respiratory infections and 224 episodes of reduced PEF were diagnosed. PEF episodes were much more likely to occur in the seven days following the onset of an upper respiratory infection than at other times. Estimated exposures to NO(2) at the time of infections were generally low (geometric mean 10.6 microg/m(3)). Compared with exposures of < or = 8 microg/m(3), exposures of >28 microg/m(3) were associated with a RR of 1.9 (95% confidence interval 1.1 to 3.4) for the development of an asthmatic episode within seven days of an infection.

CONCLUSIONS

The findings give some support to the hypothesis that NO(2) increases the risk of asthmatic exacerbations following respiratory infections, even at relatively low levels of exposure. Further studies in populations with higher exposures would be useful.

Role of NF-kappa B in cytokine production induced from human airway epithelial cells by rhinovirus infection

Infection of human epithelial cells with human rhinovirus (HRV)-16 induces rapid production of several proinflammatory cytokines, including IL-8, IL-6, and GM-CSF. We evaluated the role of NF-kappaB in HRV-16-induced IL-8 and IL-6 production by EMSA using oligonucleotides corresponding to the binding sites for NF-kappaB in the IL-6 and IL-8 gene promoters. Consistent with the rapid induction of mRNA for IL-8 and IL-6, maximal NF-kappaB binding to both oligonucleotides was detected at 30 min after infection. NF-kappaB complexes contained p65 and p50, but not c-Rel. The IL-8 oligonucleotide bound recombinant p50 with only about one-tenth the efficiency of the IL-6 oligonucleotide, even though epithelial cells produced more IL-8 protein than IL-6. Neither the potent glucocorticoid, budesonide (10-7 M), nor a NO donor inhibited NF-kappaB binding to either cytokine promoter or induction of mRNA for either IL-8 or IL-6. Sulfasalazine and calpain inhibitor I, inhibitors of NF-kappaB activation, blocked HRV-16-induced formation of NF-kappaB complexes with oligonucleotides from both cytokines, but did not inhibit mRNA induction for either cytokine. By contrast, sulfasalazine clearly inhibited HRV-16 induction of mRNA for GM-CSF in the same cells. Thus, HRV-16 induces epithelial expression of IL-8 and IL-6 by an NF-kappaB-independent pathway, whereas induction of GM-CSF is at least partially dependent upon NF-kappaB activation.

Long-term consequences of respiratory syncytial virus (RSV) bronchiolitis

Despite differences in study design, follow-up studies consistently show that approximately half of the infants with respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) go on to have recurrent wheezing episodes during childhood. Respiratory symptoms are associated with abnormal lung function, including bronchial hyper-responsiveness. Wheezing symptoms following RSV LRTI gradually decrease, and it appears that during school age airway morbidity is no longer related to RSV LRTI during infancy. Mechanisms underlying the association between RSV LRTI and long-term airway morbidity are poorly understood. On the one hand, abnormal airway function that is congenitally present or acquired before RSV LRTI occurs could be the cause of both RSV LRTI and subsequent recurrent wheezing. On the other hand, it is possible that RSV LRTI causes changes in the lower airways or the immune system that result in long-term airway morbidity. Animal models suggest that RSV infection can promote the development of allergic sensitization, but most studies in humans do not indicate a role for atopy in the development of recurrent wheezing following RSV LRTI.