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

Dexamethasone prevents virus-induced hyperresponsiveness via multiple mechanisms

In the lungs, neuronal M2 muscarinic receptors inhibit acetylcholine release from the parasympathetic nerves. Parainfluenza virus infection causes loss of M2 receptor function, which increases acetylcholine release and vagally mediated bronchoconstriction. Because glucocorticoids are known to inhibit airway hyperresponsiveness, we tested whether dexamethasone (6.5 or 65 microg/kg i.p.) prevents virus-induced hyperresponsiveness and M2 receptor dysfunction in guinea pigs. In controls, pilocarpine, a muscarinic agonist, inhibited vagally induced bronchoconstriction, demonstrating functional M2 receptors. However, in virus-infected animals, pilocarpine failed to inhibit vagally induced bronchoconstriction, demonstrating M2 receptor dysfunction. Frequency-dependent bronchoconstriction was greater in virus-infected animals than in controls, indicating airway hyperresponsiveness. Low-dose dexamethasone (6.5 microg/kg i.p.) treatment prevented virus-induced airway hyperresponsiveness, ameliorated M2 receptor dysfunction, and decreased viral content in the lungs without inhibiting virus induced inflammation. High-dose dexamethasone (65 microg/kg i.p.) prevented virus-induced hyperresponsiveness, completely reversed M2 receptor dysfunction, decreased viral titers, and decreased virus-induced inflammation. This high-dose dexamethasone also increased M2 receptor function in uninfected animals. In conclusion, dexamethasone prevented virus-induced hyperresponsiveness and M2 receptor dysfunction via multiple mechanisms.

Treating exacerbations of asthma in children: the role of systemic corticosteroids

OBJECTIVE

To review the use of systemic corticosteroids to treat recurrent, acute asthma episodes in children, with a focus on the role of oral corticosteroids.

METHODS

A comprehensive review of the literature was performed using the Medline database (January 1966-October 2002) and the Embase database (January 1980-August 2002).

RESULTS

The significant findings of 17 selected, controlled clinical trials of oral corticosteroids (OCSs) for acute exacerbations of asthma in children, compared with placebo or with other formulations of corticosteroids, can be summarized as follows: 1) OCSs are effective for the outpatient treatment of acute asthma, 2) pulmonary function tests may not be the best means of assessing the efficacy of OCSs for acute asthma, 3) early administration of OCSs for acute asthma reduces hospitalizations, 4) the critical factor for a positive outcome is early administration of the corticosteroid, and 5) OCSs are preferred for the outpatient treatment of acute asthma.

CONCLUSIONS

Early treatment of acute asthma symptoms with OCSs in children with a pattern of recurrent acute asthma may decrease the severity of acute asthma episodes and reduce the likelihood of subsequent relapses. Attention should be given to identifying these children and standardizing a treatment approach based on accepted, consistent definitions of what constitutes an asthma exacerbation and recurrence. A suggested protocol is described.

Hospitalization for asthma: atopic, pulmonary function, and psychological correlates among participants in the Childhood Asthma Management Program

BACKGROUND

Asthma in childhood has a significant impact on children and families, in part because of the frequent need for hospital-based care for acute exacerbations. Sensitization and exposure to inhalant allergens have been identified as risk factors for asthma hospitalization.

OBJECTIVE

The Childhood Asthma Management Program (CAMP), comprised of 1041 children aged 5 to 12 with mild-to-moderate asthma, provides the opportunity to identify specific risk factors for prior hospitalization for asthma.

METHODS

Data gathered during the screening period from CAMP were evaluated to elucidate differences between patients who had ever been hospitalized for asthma before enrollment in CAMP and those who had never been hospitalized.

RESULTS

Univariate analyses indicated that prior hospitalization for asthma was associated with a younger age of asthma onset, longer duration of asthma, greater number of positive allergy skin tests, higher serum immunoglobulin E level, greater peripheral blood eosinophilia, greater recent inhaled corticosteroid use, greater airflow obstruction, greater airway hyperresponsiveness, and lower patient intelligence quotient (IQ). Gender, race, and family income did not differ between hospitalized and never-hospitalized patients. The combination of both sensitization and exposure to high levels of dog allergen (Can f1) was associated with greater likelihood of prior hospitalization. Forward multivariate logistic regression analysis identified younger age of asthma onset, longer duration of asthma, recent use of asthma controller therapy, greater airflow obstruction, and lower patient IQ as significant risk factors for prior hospitalization when all risk factors identified by univariate analysis were included in the model.

CONCLUSIONS

Children with mild-to-moderate asthma who had a past hospitalization for acute asthma had greater asthma severity, younger age of onset, and lower patient IQ at the time of entry into CAMP. They also had more markers of atopy than children without prior hospitalization, although atopy was not associated with prior hospitalization on multivariate analysis. Although we have identified these risk factors in a retrospective manner, one can speculate that the persistence of these features should alert the clinician to closely follow abnormalities on pulmonary function tests and general features of atopy to potentially identify patients at risk for future hospitalization.

An adult model of exclusive viral wheeze: inflammation in the upper and lower respiratory tracts

BACKGROUND

We have previously reported an experimental infection of young adults with a history of episodic and exclusive viral wheeze (EVW) using human coronavirus, in which 16 of 24 with EVW (15 atopic) and 11 of 19 healthy controls (seven atopic) developed a symptomatic cold with evidence of infection, but only those with EVW developed lower respiratory tract symptoms and increased airway responsiveness.

OBJECTIVE

The aim of this study was to compare the EVW and control groups from this study for inflammatory changes occurring in the upper and lower respiratory tracts during the experimental infection, in particular, to determine whether eosinophil-driven inflammation was associated with EVW.

METHODS

Nasal lavage and induced sputum were collected prior to inoculation (day 0) and 2, 4 and 17 days later. Differential cell counts were performed and supernatant was assayed for IL-8, IL-5, IFN-gamma, and eosinophilic cationic protein (ECP).

RESULTS

There was no difference between the two groups in any measurement at baseline. In both groups, during colds the volume of nasal secretion increased as did leucocyte counts in both upper and lower respiratory tracts. A modest increase in nasal neutrophil count was seen in both EVW and control groups with symptomatic colds on day 2 (median (quartile) difference from baseline 5.4 (0.0, 11.0) and 1.8 (-1.1, 2.2)x10(4)/mL of secretions, respectively). The change in nasal neutrophil counts in all subjects correlated with nasal symptom scores. A significant relative increase in sputum differential neutrophil count was seen on day 4 in the EVW group with a cold but not in controls (mean difference (95% confidence interval) 20.4 (9.6, 31.1)% and 3.1 (-8.2, 14.5)%, respectively, P<0.01); however, this increase did not correlate with lower respiratory tract symptom scores. IL-8 increased in both the upper and lower respiratory tracts in both EVW and control subjects with colds, the largest change being seen on day 4 in the sputum of those with EVW (mean difference from baseline (95% confidence interval) 2.5 (0.55-4.46) ng/mL). Only modest changes were seen in IFN-gamma and no changes were seen in IL-5 or ECP. None of the results was influenced by the atopic status of the subjects in either group.

CONCLUSIONS

EVW wheeze is characterized by neutrophilic inflammation in both the upper and lower respiratory tracts without eosinophilia (even in atopic subjects). IL-8 is likely to be an important chemokine in this process. Symptoms and airway responsiveness were correlated with change in neutrophils.

The complex relationship between respiratory syncytial virus and allergy in lung disease

Epidemiologic studies suggest a strong link between severe respiratory syncytial virus (RSV)-induced bronchiolitis in infancy and allergic disease; however, the mechanisms determining this relationship are currently unknown. In this review article, we summarize data from human clinical studies that explore the association between RSV infection and allergy, some that suggest that RSV bronchiolitis requiring hospitalization leads to an increased incidence of the allergic phenotype and others that suggest that pre-existing allergy is a risk factor for severe RSV bronchiolitis. We also review the published murine models that combine RSV infection and allergic sensitization that attempt to explain the complex relationship between these two factors in regard to lung immunopathology and physiologic dysfunction.

Personal exposure to nitrogen dioxide (NO2) and the severity of virus-induced asthma in children

BACKGROUND

A link between exposure to the air pollutant nitrogen dioxide (NO2) and respiratory disease has been suggested. Viral infections are the major cause of asthma exacerbations. We aimed to assess whether there is a relation between NO2 exposure and the severity of asthma exacerbations caused by proven respiratory viral infections in children.

METHODS

A cohort of 114 asthmatic children aged between 8 and 11 years recorded daily upper and lower respiratory-tract symptoms, peak expiratory flow (PEF), and measured personal NO2 exposures every week for up to 13 months. We took nasal aspirates during reported episodes of upper respiratory-tract illness and tested for infection by common respiratory viruses and atypical bacteria with RT-PCR assays. We used generalised estimating equations to assess the relation between low (<7.5 microg/m3), medium (7.5-14 microg/m3 ), and high (>14 microg/m3) tertiles of NO2 exposure in the week before or after upper respiratory-tract infection and the severity of asthma exacerbation in the week after the start of an infection.

FINDINGS

One or more viruses were detected in 78% of reported infection episodes, and the medians of NO2 exposure were 5 (IQR 3.6-6.3), 10 (8.7-12.0), and 21 microg/m3 (16.8-42.9) for low, medium, and high tertiles, respectively. There were significant increases in the severity of lower respiratory-tract symptom scores across the three tertiles (0.6 for all viruses [p=0.05] and >2 for respiratory syncytial virus [p=0.01]) and a reduction in PEF of more than 12 L/min for picornavirus (p=0.04) for high compared with low NO2 exposure before the start of the virus-induced exacerbation.

INTERPRETATION

High exposure to NO2 in the week before the start of a respiratory viral infection, and at levels within current air quality standards, is associated with an increase in the severity of a resulting asthma exacerbation.

Double-stranded RNA induces the synthesis of specific chemokines by bronchial epithelial cells

Virus-induced secretion of proinflammatory chemokines (e.g., regulated on activation, normal T cells expressed and secreted [RANTES], interleukin [IL]-8) by airway epithelial cells helps to initiate antiviral responses and airway inflammation by enhancing inflammatory cell recruitment. To define mechanisms for virus-induced chemokine secretion, monolayers of nontransformed bronchial epithelial cells were transfected or incubated with polydeoxyinosinic-deoxycytidylic acid (synthetic double-stranded [ds] RNA), rhinovirus dsRNA, or single-stranded RNA (ssRNA), and the secretion of selected chemokines was determined. Transfection or incubation with dsRNA, but not ssRNA, significantly enhanced secretion of RANTES and IL-8, but not eotaxin or macrophage inflammatory protein-1alpha. Mechanistically, dsRNA induced and activated dsRNA-dependent protein kinase (PKR), and activated nuclear factor-kappaB and p38 mitogen-activated protein kinase. Furthermore, the PKR inhibitor 2-aminopurine significantly blocked dsRNA-induced RANTES and IL-8 secretion, whereas the p38 mitogen-activated protein kinase inhibitor SB203580 suppressed dsRNA-induced IL-8, but not RANTES. These findings indicate that dsRNA selectively induce the secretion of chemokines such as IL-8 and RANTES, and implicate dsRNA-sensitive signaling proteins in this process. Moreover, these data suggest that this may be an important mechanism for the selective secretion of chemokines by viruses (e.g., rhinovirus, respiratory syncytial virus, influenza) that synthesize dsRNA during replication.

Infectious triggers of pediatric asthma

Respiratory infections can cause wheezing illnesses in children of all ages and also can influence the causation and disease activity of asthma. For years it has been recognized that respiratory syncytial virus infections often produce the first episode of wheezing in children who go on to develop chronic asthma. More recently, it has been proposed that repeated infections with other common childhood viral pathogens might help the immune system develop in such a way as to prevent the onset of allergic diseases and possibly asthma. In addition to the effects of viral infections, infections with certain intracellular pathogens, such as chlamydia and mycoplasma, may cause acute and chronic wheezing in some individuals, whereas common cold and acute sinus infections can trigger acute symptoms of asthma. In this article, the epidemiologic, mechanistic, and treatment implications of the association between respiratory infections and asthma are discussed.

Diagnosis and treatment of rhinovirus respiratory infections

Acute upper viral respiratory infection (VRI) is the number one cause of illness for which patients seek medical care in the United States. Rhinoviruses, members of the family Picornaviridae, are the causative pathogens in more than half of VRIs, and they are associated with acute exacerbations of respiratory disease, including asthma, sinusitis, otitis media, and COPD. Owing to the lack of commercial availability of rapid and cost-effective laboratory tests to confirm the presence of VRI, the diagnosis is most commonly made empirically, based on patient history and physical examination. Currently, no antiviral agents that are active against picornaviruses are available for clinical use. Antimicrobial agents, frequently prescribed for VRIs, are not active against viruses, and their inappropriate and widespread use has contributed to an increase in antimicrobial resistance among bacteria commonly involved in respiratory tract infections. Several newer antiviral agents are being evaluated for treatment of VRIs. Although a variety of mechanisms and agents have been tested, few have shown significant clinical benefit in human trials. The most advanced antiviral agent in clinical trials is pleconaril, a novel viral capsid-binding inhibitor with potent and highly specific in vitro activity against the majority of serotypes of rhinoviruses and enteroviruses. Clinical trials of pleconaril for the treatment of VRIs have been conducted, and the role of pleconaril in patients with chronic lung disease is being evaluated.

Experimental rhinovirus challenges in adults with mild asthma: response to infection in relation to IgE

BACKGROUND

Although most children and young adults with asthma are atopic, exacerbations of asthma are frequently associated with viral respiratory tract infections, especially those caused by rhinovirus (HRV).

OBJECTIVE

Young atopic adults with mild asthma were evaluated before and during an experimental HRV infection to test the hypothesis that airway inflammation before virus inoculation may be a risk factor for an adverse response to HRV.

METHODS

Experimental HRV infections were evaluated in 16 allergic volunteers with mild asthma and 9 nonatopic control patients (age, 18 to 30 years). Before virus inoculation, each participant was screened with tests for lung function, prick skin tests for sensitization to common aeroallergens, measurements of total serum IgE, and serum neutralizing antibody to rhinovirus-16 (the serotype used for inoculation). The response to infection was monitored for 21 days by using symptom diary cards, tests for lung function, and markers of airway inflammation in nasal washes, blood, and expired air.

RESULTS

During the infection, asthmatic patients had cumulative upper and lower respiratory tract symptom scores that were significantly greater over the course of 21 days than scores from the control patients. At baseline, the asthmatic patients also had increased sensitivity to methacholine and significantly lower values for FEV(1) (percent predicted) than the control patients (geometric mean and intraquartile values: 87% [79% to 91%] for the asthmatic patients and 101% [90% to 104%] for the control patients, P <.03). Among the patients with mild asthma, 6 had levels of total serum IgE that were substantially elevated (range, 371 to 820 IU/mL) compared with 10 who had lower levels (range, 29 to 124 IU/mL). Those with high levels of IgE had significantly greater lower respiratory tract symptom scores during the initial 4 days of the infection than the low IgE group. They also had higher total blood eosinophil counts at baseline, increased eosinophil cationic protein in their nasal washes (>200 ng/mL), and augmented levels of expired nitric oxide at baseline and during peak cold symptoms. In contrast, levels of soluble intracellular adhesion molecule-1 in nasal wash supernatants from the asthmatic patients with high IgE were diminished, both at baseline and during the infection.

CONCLUSIONS

The reduced lung function and increased markers of inflammation observed before virus inoculation in the asthmatic patients who had high levels of total serum IgE may be risk factors for an adverse response to infections with HRV.

Introduction to nasal and pulmonary allergy cascade

The early phase of an IgE-dependent allergic reaction is followed by the activation of a complex network of inflammatory phenomena - T lymphocytes, cytokines, mediators, and adhesion molecules - that mediate late and ongoing allergic symptoms. The kinetics of respiratory inflammation following allergen exposure involve the migration of inflammatory cells to the mucosa within about 30 min, increased inflammatory infiltration over the following hours, and then slow subsidence. A relationship between asthma and allergic rhinitis is supported by epidemiological, histological, physiological, and immunopathological data, and by the response of asthma symptoms in rhinitic patients to intranasal corticosteroids and antihistamines. For example, there is no morphological difference between the bronchial inflammatory response following allergen-specific challenge in patients suffering from asthma alone or rhinitis alone. It is the allergen dose that makes the difference in the airway response to allergen in allergic rhinitis and asthma. Recognition of the relationship between asthma and allergic rhinitis has led to the introduction of new diagnostic terminology and treatment recommendations: 1) patients with persistent rhinitis should be evaluated for asthma; 2) patients with persistent asthma should be evaluated for rhinitis; and 3) a strategy should combine the treatment of upper and lower airways in terms of efficacy and safety.

Impact of respiratory viral infections on cystic fibrosis

The life expectancy for patients with cystic fibrosis has improved remarkably over the last 20 years. Progressive deterioration of pulmonary function continues despite the aggressive use of antimicrobials. The absence of fever, neutrophilia, and systemic symptoms suggest that during pulmonary exacerbations other non-bacterial factors may have played a part. Some have suggested respiratory viruses as main suspects. So far, few data have illustrated the relationship of respiratory viruses and cystic fibrosis. By gaining further knowledge of this relationship, one may change future clinical practice and boost the survival of these patients.

Muscarinic acetylcholine receptors and airway diseases

Parasympathetic nerves provide the dominant autonomic innervation of the airways. Release of acetylcholine from parasympathetic nerves activates postjunctional muscarinic receptors present on airway smooth muscle, submucosal glands, and blood vessels to cause bronchoconstriction, mucus secretion, and vasodilatation, respectively. Acetylcholine also feeds back onto prejunctional muscarinic receptors to enhance or inhibit further acetylcholine release. In asthma and chronic obstructive pulmonary disease, bronchoconstriction and mucus secretion is increased and the airways are hyperresponsive to contractile agents. These changes are due to increased parasympathetic nerve activity. The number and function of postjunctional muscarinic receptors in the airways are unchanged in animal models of asthma. Rather, it is the supply of acetylcholine to the postjunctional cells (smooth muscle and submucosal gland) that is increased. The increase in acetylcholine release occurs because prejunctional, inhibitory M(2) muscarinic receptors on the parasympathetic nerves are dysfunctional. M(2) muscarinic receptor dysfunction and subsequent airway hyperreactivity have been demonstrated to occur in animals in response to a variety of triggers, including antigen challenge, virus infection, ozone exposure, and vitamin A deficiency. In humans, there is evidence that loss of M(2) muscarinic receptor function is related to asthma. The mechanisms by which neuronal M(2) muscarinic receptor function is lost and its relevance to human airway disease are discussed in this review.

T cell cytokine profiles in childhood asthma

BACKGROUND

An imbalance of T cell subsets in asthma with a predominance of Th2 type cells has been proposed. The aim of this study was simultaneously to detect surface markers and intracellular production of cytokines in T cells from the airways of children with and without asthma.

METHODS

Bronchoalveolar lavage (BAL) fluid was obtained by wedging a suction catheter into the distal airway immediately before elective surgery. Cells were stimulated with phorbol 12-myristrate 13-acetate (PMA) and ionomycin and intracytoplasmic cytokine retention was achieved using monensin. The cells were stained with the relevant antibodies and analysed by flow cytometry.

RESULTS

No statistical difference was observed between children with atopic asthma, atopic non-asthmatic subjects, and normal controls in the percentage of CD3+ cells producing interleukin (IL)-2 or IL-4. Interferon (IFN)gamma+ T cells were, however, present in a much higher percentage than either IL-2 or IL-4 positive cells. The percentage of IFNgamma+ T cells was significantly increased in subjects with atopic asthma (median 71.3%, interquartile range (IQR) 65.1-82.2, n=13) compared with both atopic non-asthmatic subjects (51.9%, IQR 37.2-70.3, n=12), p<0.05 and normal controls (58.1%, IQR 36.1-66.1, n=23), p<0.01.

CONCLUSIONS

These findings indicate that IFNgamma producing T cells are more abundant in the airways of children with atopic asthma than in atopic non-asthmatic subjects and controls. The proinflammatory activities of IFNgamma may play an important role in the pathogenesis of childhood asthma and may suggest that asthma is not simply a Th2 driven response.

Specific patterns of responsiveness to microbial antigens staphylococcal enterotoxin B and purified protein derivative by cord blood mononuclear cells are predictive of risk for development of atopic dermatitis

BACKGROUND

Mononuclear cells from children with active atopic dermatitis (AD) have been reported to be hyper-responsive to certain microbial stimuli, in particular staphylococcal enterotoxin B (SEB). However, it is not known whether this responsiveness is acquired during disease development, or is inherent. We investigated this question in a cohort of children at high risk of atopy followed prospectively from birth to age 3 years. We asked whether their cord blood mononuclear cell (CBMC) cytokine responses to SEB, to an unrelated microbial stimulus purified protein derivative (PPD), or to common allergens, were predictive of risk for subsequent AD development during infancy.

METHODS

Children at high risk of developing atopy were randomly selected from an ongoing prospective cohort. Cord blood was collected at birth. The children were seen at 6 months, 1, 2 and 3 years and examined for the development of AD. IFN-gamma, IL-5, IL-10 and IL-13 production by CBMC cultured in the presence of SEB, PPD, PHA, house dust mite (HDM) allergen, ovalbumin (OVA) and cat allergen was determined.

RESULTS

SEB-induced IL-5 production by CBMC was elevated in children who developed AD at 6 months (P = 0.01) and 2 years (P = 0.009). PPD-induced IL-5 responses were also elevated in CBMC from children who developed AD at 6 months, 2 years and 3 years (P = 0.05, P = 0.06 and P = 0.06, respectively), as were PPD-induced IL-10 responses (P = 0.05 at 1 years, P = 0.007 at 2 years, P = 0.003 at 3 years) and corresponding IFN-gamma responses (P = 0.05 at 6 months, P = 0.003 at 2 years, P = 0.0004 at 3 years). Increased IL-10 responses to HDM allergen were also observed throughout the observation period in CBMC from children who developed AD.

CONCLUSION

Children who develop infantile AD appear to have a predisposition to respond to SEB in a Th2-dominant manner involving selective stimulation of IL-5 production. The increased IL-10 and IFN-gamma induced in response to PPD by children with AD may point to additional intrinsic differences in responses to microbial stimuli between those at high vs. those at low risk for AD, which merit more detailed investigations.

Use of induced sputum for the diagnosis of influenza and infections in asthma: a comparison of diagnostic techniques

BACKGROUND

Influenza (Flu) and respiratory syncytial virus (RSV) are important viral pathogens that cause lower respiratory tract infections and severe exacerbations of asthma. Molecular biological techniques are permitting a rapid and accurate diagnosis of infections caused by respiratory pathogens, and have typically been applied to upper respiratory samples. Sputum induction provides an opportunity to directly sample secretions from the lower respiratory tract.

OBJECTIVES/STUDY DESIGN

To determine the role of induced sputum reverse-transcription polymerase chain reaction (RT-PCR) in the detection of respiratory pathogens and compare this with detection using serology and immunofluorescent antigen (IFA) testing, we recruited 49 adults from emergency room with exacerbations of asthma. After a medical assessment and spirometry, sputum was induced using ultrasonically nebulised normal saline. Sputum was assayed using IFA and RT-PCR for flu and RSV. Flu serology was performed acutely and at convalescence, 4-5 weeks later.

RESULTS

Influenza A or B was detected in 24% of the samples by PCR, significantly more than the nine cases detected using serology and the one case using IFA (P<0.05). RSV was detected in 37% of samples using PCR and 20% by IFA (P<0.05).

CONCLUSION

The combination of induced sputum and RT-PCR provides a useful means of detecting respiratory infection. The technique is safe in both adults and children, and RT-PCR is more sensitive than conventional serology and IFA. The improved sensitivity of induced sputum RT-PCR also permits a more rapid diagnosis and the opportunity of early administration of effective treatments.

Changes in rhinovirus protein 2C allow efficient replication in mouse cells

Rhinovirus type 16 was found to replicate in mouse L cells that express the viral receptor, human intercellular adhesion molecule 1 (ICAM-1). However, infection of these cells at a low multiplicity of infection leads to no discernible cytopathic effect, and low virus titers are produced. A variant virus, 16/L, was isolated after alternate passage of rhinovirus 16 between HeLa and ICAM-1 L cells. Infection of mouse cells with 16/L leads to higher virus titers, increased production of RNA, and total cytopathic effect. Three amino acid changes were identified in the P2 region of virus 16/L, and the adaptation phenotype mapped to two changes in protein 2C. The characterization of a rhinovirus host range mutant will facilitate the investigation of cellular proteins required for efficient viral growth and the development of a murine model for rhinovirus infection.

Anti-inflammatory treatment for recurrent wheezing in the first five years of life

Medications identified for the treatment of recurrent wheezing in preschool children by the Expert Panel Report of the NHLBI Guidelines for the Diagnosis and Management of Asthma include inhaled corticosteroids, chromones, theophylline, and leukotriene pathway modifiers. However, these various agents differ in their mechanism, extent of action on the airway inflammatory process, and degree of clinical efficacy. Inhaled corticosteroids can control symptoms in many young children with even severe persistent wheezing, but data on their long-term safety when administered in preschool-age children are scarce. There is some information on the uninterrupted use of inhaled corticosteroids in school-age children and the absence of an adverse effect on ultimate adult height. Despite laboratory evidence of adrenal suppression in some studies, few pediatric cases of clinical adrenal insufficiency have been reported. Low-dose inhaled corticosteroid (<400 mcg/day for beclomethasone), which is adequate for controlling mild persistent symptoms, is generally safe. Chromones have a remarkable safety profile, but they are most effective for symptoms of mild severity. Promising data have been published on the efficacy and safety of leukotriene pathway modifiers when used in young children with persistent symptoms. It is uncertain whether early introduction and long-term administration of inhaled corticosteroids prevent development of irreversible airway obstruction. Nevertheless, they may be especially useful for patients with moderate to severe disease in whom other agents (chromones or leukotriene pathway modifiers) will most likely fail to control symptoms. Pediatr Pulmonol. 2003; 35:241-252.

Viral infections in obstructive airway diseases

The most common syndromes associated with obstructive lung disease are asthma and chronic obstructive pulmonary disease (COPD). Evidence for a viral etiology of asthmatic exacerbations is well known, but evidence for a role for viruses in COPD exacerbation is just emerging. Viruses may cause chronic infection in both diseases. This paper reviews some studies on the effects of respiratory viruses on asthma and COPD published in 2002 and discusses their relevance to current thinking in pulmonary medicine.

Is asthma an infectious disease?: Thomas A. Neff lecture

Respiratory tract infections caused by viruses, Chlamydia, and Mycoplasma have been implicated in the pathogenesis of asthma. Of these respiratory pathogens, viruses have been demonstrated to be associated with asthma epidemiologically in at least two ways. First, during infancy, certain viruses have been implicated as potentially being responsible for the inception of the asthmatic phenotype. Second, in patients with established asthma, particularly children, viral upper respiratory tract infections play a significant role in producing acute exacerbations of airway obstruction that may result in frequent outpatient visits or in hospitalizations. For infections with other microbial agents, recent attention has focused on Chlamydia and Mycoplasma as potential contributors to both exacerbations and the severity of chronic asthma in terms of loss of lung function or medication requirements. In an attempt to address the question posed in the title, this article will briefly review these various associations as they pertain to the pathogenesis of asthma in both children and adults.

Efficacy of a consensus protocol therapy in adults with acute, severe asthma

BACKGROUND

International guidelines recommend multiple doses of inhaled beta2-agonists and anticholinergics plus early administration of systemic corticosteroids for acute, severe asthma. This study examined the efficacy of this protocol in adults and analyzed those factors associated with unresponsiveness to the protocol therapy.

OBJECTIVE

Ninety-three consecutive patients 18 to 55 years old presenting for treatment of acute asthma with a peak expiratory flow rate (PEFR) < or = 50% of the predicted value were analyzed.

METHODS

All subjects received 400 microg of salbutamol every 20 minutes for three doses and 400 microg of oxitropium bromide with each of the three salbutamol doses by means of a metered-dose inhaler with a spacer device, plus intravenously 8 mg betamethasone. PEFR was measured at baseline and at 20, 40, 60, and 120 minutes.

RESULTS

Sixty-nine percent of subjects improved sufficiently to be discharged. In 31% of subjects, the protocol therapy failed. There were no significant differences in age, sex, smoking status, or beta-agonist use within 6 hours between the two groups. Logistic regression analysis demonstrated that a PEFR < 35% of the predicted value at presentation (odds ratio [OR]; 16.3, 95% confidence interval [CI] 4.5 to 59.9), viral respiratory tract infection symptoms > or = 2 days (OR, 4.8, 95% CI 1.3 to 17.1), and asthma hospitalization in the past year (OR, 4.6, 95% CI 1.1 to 19.9) were significantly associated with unresponsiveness to the protocol.

CONCLUSIONS

Unresponsiveness to protocol therapy occurs in nearly one-third of individuals presenting with acute, severe asthma. Our findings underscore the need to explore more effective strategies for improving lung function and reducing hospital admission rates.

Pleconaril, a novel antipicornaviral agent

Despite the availability of therapy for selected symptoms, no specific antiviral agents are available to treat or prevent infections due to the viruses of the Picornaviridae family--rhinoviruses and enteroviruses. Characterization of the three-dimensional structure of picornaviruses in the 1980s allowed development of compounds targeted at the virus itself. Pleconaril is a novel, orally available, systemically acting molecule whose pharmacokinetics are characterized by a two-compartment open model with first-order absorption and with a safety profile similar to that of placebo. It shows promising results in treatment of picornaviral respiratory tract infections, meningitis, and other life-threatening infections.

Rhinoviruses in the pathogenesis of asthma

Using sensitive diagnostic methodologies, epidemiologic studies during the past decade have allowed the identification of human rhinoviruses (RVs), generally recognized as "common cold viruses," as major asthma precipitants. This association was further established by evaluating the impact of RV infection in airway obstruction and inflammation during naturally acquired or experimentally induced RV colds. There is now strong evidence that RVs can infect and propagate not only in the upper but also in the lower airways. Bronchial and pulmonary epithelia infected by RVs are rich sources of inflammatory mediators, which may initiate or augment airway inflammation and obstruction. Furthermore, in an atopic environment, responses to the virus are skewed by and toward an "atopic," Th2-like balance, which may further enhance inflammation and exacerbate asthma.

CD8+ T lymphocytes in viral hyperreactivity and M2 muscarinic receptor dysfunction

In the airways, inhibitory M2 muscarinic receptors (M2Rs) on parasympathetic nerves limit acetylcholine release. Viral infection causes M2R dysfunction, which increases acetylcholine release and leads to airway hyperreactivity. In these studies we tested the role of CD8+ T cells in parainfluenza virus-induced hyperreactivity and M2R dysfunction in normal guinea pigs and in guinea pigs previously sensitized to ovalbumin. Depleting CD8+ T cells prevented virus-induced M2R dysfunction and hyperreactivity in sensitized animals, but not in nonsensitized animals. Sensitization increased the number of eosinophils in close relation to the airway nerves where, when activated, they release major basic protein, which binds to and blocks the M2Rs. Regardless of sensitization, viral infection decreased the number of visible tissue eosinophils, likely reflecting eosinophil degranulation via cytolysis. Depleting CD8+ T cells prevented this virus-induced eosinophil degranulation. In addition, an antiviral effect of sensitization, which we previously showed to be eosinophil mediated, was again seen. This was prevented by depletion of CD8+ Tcells. Thus, CD8+ T cells play a role in airway hyperreactivity and M2R dysfunction of sensitized virus-infected guinea pigs by mediating eosinophil degranulation near airway nerves. In contrast, CD8+ T cells are not necessary for virus-induced hyperreactivity and M2R dysfunction in nonsensitized guinea pigs.

6. Asthma

The increasing incidence and prevalence of asthma in many parts of the world continue to make it a global health concern. The heterogeneous nature of the clinical manifestations and therapeutic responses of asthma in both adult and pediatric patients indicate that it may be more of a syndrome rather than a specific disease entity. Numerous triggering factors including viral infections, allergen and irritant exposure, and exercise, among others, complicate both the acute and chronic treatment of asthma. Therapeutic intervention has focused on the appreciation that airway obstruction in asthma is composed of both bronchial smooth muscle spasm and variable degrees of airway inflammation characterized by edema, mucus secretion, and the influx of a variety of inflammatory cells. The presence of only partial reversibility of airflow obstruction in some patients indicates that structural remodeling of the airways may also occur over time. Choosing appropriate medications depends on the disease severity (intermittent, mild persistent, moderate persistent, severe persistent), extent of reversibility, both acutely and chronically, patterns of disease activity (exacerbations related to viruses, allergens, exercise, etc), and the age of onset (infancy, childhood, adulthood).

Development of a predictive index for picornavirus infections

To create a clinical prediction index that aids in the diagnosis of picornavirus respiratory infections, we analyzed patients from 5 clinical trials designed to evaluate the efficacy of an antiviral treatment for respiratory infections. Logistic regression was used to determine which baseline symptoms and patient characteristics best predicted picornavirus infection. Parameter estimates were then used to create a predictive index for estimating the probability of picornavirus infection on the basis of cold symptoms. The presence at baseline of rhinorrhea (odds ratio [OR], 2.73), nasal congestion (OR, 1.63), and sore throat (OR, 1.37) increased the likelihood of picornavirus infection; the presence of myalgia (OR, 0.71) and fever (OR, 0.59) decreased the likelihood. The positive and negative predictive values of the model were 61.5% and 64.4%, respectively. The model was simplified for clinical use by creating a whole-number index: the lowest possible score (-3) indicates a 15% chance of picornavirus infection and the highest (7) indicates a 69% chance of picornavirus infection.

8. Occupational asthma and allergies

A diversity of airborne dusts, gases, fumes, and vapors can cause dose-related symptoms in individuals exposed in the workplace. More than 250 chemicals have been incriminated as a cause of occupational asthma (OA). The prevalence of OA ranges from 2% to 6% of the asthmatic population. Predisposing factors facilitating the development of OA include the work environment, climatic conditions, genetic proclivities, tobacco and recreational drug use, respiratory infection, and bronchial hyperresponsiveness. Pathogenetically, new-onset OA may be immunologic or nonimmunologic in origin. The immunologic variants are usually caused by high molecular-weight allergens such as grain dust and animal or fish protein. Symptoms ensue after a latent period of months to years. Nonimmunologic OA can be precipitated by a brief, high-level exposure to a potent irritant. Symptoms occur immediately or within a few hours of the exposure. In either instance, once the diagnosis is established, the worker should be removed from the workplace. If the diagnosis is made in a timely fashion, most workers experience improvement. Prevention is the best therapeutic intervention.

Role of viruses and atypical bacteria in exacerbations of asthma in hospitalized children: a prospective study in the Nord-Pas de Calais region (France)

We studied the role of viruses and atypical bacteria in children hospitalized with exacerbated asthma by a prospective study of children with acute asthma admitted to the Department of Pediatrics in Lille, and to 15 hospitals in the Nord-Pas de Calais region, from October 1, 1998-June 30, 1999. We included children aged 2-16 years with active asthma, defined as three or more recurrent episodes of reversible wheezing. The severity of asthma and of asthmatic exacerbations was recorded. Immunofluorescence assays (IFA) on nasopharyngeal secretions (NPS), serological tests, or both, were used for detection of influenza virus, respiratory syncytial virus (RSV), adenovirus, parainfluenza virus, and coronavirus. Polymerase chain reaction (PCR) assays on NPS were used for rhinovirus and enterovirus. Serological tests for Chlamydia pneumoniae and Mycoplasma pneumoniae were performed. A control group of asymptomatic asthmatic outpatients was examined for respiratory viruses (using IFA and PCR). Eighty-two symptomatic children (mean age, 7.9 years) were examined. Viruses were detected in 38% (enterovirus, 15.8%; rhinovirus, 12%; RSV, 7.3%). Serological tests for atypical bacteria were positive in 10% of patients (C. pneumoniae, 5%; M. pneumoniae, 5%). Among the 27 control subjects (mean age, 7.9 years), one PCR was positive for enterovirus. There was no correlation between severity of chronic asthma or asthmatic exacerbations and the diagnosis of infection. Atypical bacterial pathogen infections were linked with prolonged asthmatic symptoms. In conclusion, we confirmed the high incidence of viral infection in acute exacerbations of asthma, especially enteroviruses or rhinoviruses. Persistent clinical features were more frequently associated with atypical bacterial infections, suggesting that these infections should be investigated and treated in cases of persistent asthmatic symptoms.

Atypical pathogen infection in adults with acute exacerbation of bronchial asthma

In a serologically based prospective study, acute infections with four atypical pathogens were determined in 100 adults hospitalized for acute exacerbation of bronchial asthma, and compared with the corresponding rate in a matched control group. Paired sera were tested using immunofluorescence or enzyme immunoassay methods to establish the serologic diagnosis. In 18 patients (18%), there was evidence of acute infection with Mycoplasma pneumoniae, compared with 3% in the control group (p = 0.0006). In 10 of these patients there was evidence of infection with at least one additional pathogen, a respiratory virus in 7. There was no significant difference between the study groups in the rates of acute infection by Chlamydia pneumoniae (8% in the hospitalized patients versus 6% in the control subjects), Legionella spp. (5 versus 3%, respectively), or Coxiella burnettii (no patients in either group). We conclude that of these four atypical pathogens, only infection with M. pneumoniae is associated with hospitalization for acute exacerbation of bronchial asthma. In most of these M. pneumoniae patients there is evidence of infection with a respiratory virus as well. The pathophysiologic and therapeutic significance of these findings should be tested in further studies specifically designed to address these questions.

The role of respiratory viruses in the origin and exacerbations of asthma

PURPOSE OF REVIEW

The present review focuses and comments on the increasing body of evidence correlating respiratory viral infections with asthma onset and exacerbations.

RECENT FINDINGS

Recent data suggest multiple and some time contrasting roles for viral infection in the origin of asthma. These data also indicate that the immune status of the host, including atopy, may interactively contribute to this process, conferring susceptibility or even resistance to the development of asthma in virus-infected individuals. In the presence of asthma, the role of viral infection in triggering exacerbations is clearly established. Chemokine and cytokine responses of the respiratory epithelium, a biased type 1/type 2 cytokine balance, defective costimulation, as well as abnormal neural control have been suggested as possible mechanisms. The importance of concurrent or synergistic effects of allergen exposure is currently under scrutiny.

SUMMARY

Viruses may initiate and certainly exacerbate asthma. Mild repeated infections early in life could also stimulate type 1 immune responses conferring protection from atopy and asthma. The host's immune status, the type of viral infection and the timing of exposure to various environmental stimuli are probably the key factors in this process. Mechanistic insights deduced from recent work should allow for the development of intervening strategies in the near future.

Airborne rhinovirus detection and effect of ultraviolet irradiation on detection by a semi-nested RT-PCR assay

BACKGROUND

Rhinovirus, the most common cause of upper respiratory tract infections, has been implicated in asthma exacerbations and possibly asthma deaths. Although the method of transmission of rhinoviruses is disputed, several studies have demonstrated that aerosol transmission is a likely method of transmission among adults. As a first step in studies of possible airborne rhinovirus transmission, we developed methods to detect aerosolized rhinovirus by extending existing technology for detecting infectious agents in nasal specimens.

METHODS

We aerosolized rhinovirus in a small aerosol chamber. Experiments were conducted with decreasing concentrations of rhinovirus. To determine the effect of UV irradiation on detection of rhinoviral aerosols, we also conducted experiments in which we exposed aerosols to a UV dose of 684 mJ/m2. Aerosols were collected on Teflon filters and rhinovirus recovered in Qiagen AVL buffer using the Qiagen QIAamp Viral RNA Kit (Qiagen Corp., Valencia, California) followed by semi-nested RT-PCR and detection by gel electrophoresis.

RESULTS

We obtained positive results from filter samples that had collected at least 1.3 TCID50 of aerosolized rhinovirus. Ultraviolet irradiation of airborne virus at doses much greater than those used in upper-room UV germicidal irradiation applications did not inhibit subsequent detection with the RT-PCR assay.

CONCLUSION

The air sampling and extraction methodology developed in this study should be applicable to the detection of rhinovirus and other airborne viruses in the indoor air of offices and schools. This method, however, cannot distinguish UV inactivated virus from infectious viral particles.

The common cold

Despite great advances in medicine, the common cold continues to be a great burden on society in terms of human suffering and economic losses. Of the several viruses that cause the disease, the role of rhinoviruses is most prominent. About a quarter of all colds are still without proven cause, and the recent discovery of human metapneumovirus suggests that other viruses could remain undiscovered. Research into the inflammatory mechanisms of the common cold has elucidated the complexity of the virus-host relation. Increasing evidence is also available for the central role of viruses in predisposing to complications. New antivirals for the treatment of colds are being developed, but optimum use of these agents would require rapid detection of the specific virus causing the infection. Although vaccines against many respiratory viruses could also become available, the ultimate prevention of the common cold seems to remain a distant aim.

Air pollution and infection in respiratory illness

The detrimental effects of air pollution on health have been recognized for most of the last century. Effective legislation has led to a change in the nature of the air pollutants in outdoor air in developed countries, while combustion of raw fuels in the indoor environment remains a major health hazard in developing countries. The mechanisms of how these pollutants exert their effects are likely to be different, but there is emerging evidence that the toxic effects of new photochemical pollutants such as nitrogen dioxide are likely to be related to infection. This review discusses the relationship between air pollution and infection and will explore some of the mechanisms of how both could act synergistically to cause respiratory illnesses especially in exacerbating symptoms in individuals with pre-existing respiratory conditions such as asthma and chronic obstructive pulmonary disease.

Respiratory viruses in exacerbations of chronic obstructive pulmonary disease requiring hospitalisation: a case-control study

BACKGROUND

Acute exacerbations of chronic obstructive pulmonary disease (AE-COPD) are a common cause of hospital admission. Many exacerbations are believed to be due to upper and/or lower respiratory tract viral infections, but the incidence of these infections in patients with COPD is still undetermined.

METHODS

Respiratory syncytial virus (RSV), influenza A and B, parainfluenza 3, and picornaviruses were detected by nested reverse transcription polymerase chain reaction (RT-PCR) in upper (nasal lavage) and lower respiratory tract specimens (induced sputum). In a 2:1 case-control set up, 85 hospitalised patients with AE-COPD and 42 patients with stable COPD admitted for other medical reasons were studied.

RESULTS

Respiratory viruses were found more often in sputum and nasal lavage of patients with AE-COPD (48/85, 56%) than in patients with stable COPD (8/42, 19%, p<0.01). The most common viruses were picornaviruses (21/59, 36%), influenza A (15/59, 25%), and RSV (13/59, 22%). When specimens were analysed separately, this difference was seen in induced sputum (exacerbation 40/85 (47%) v stable 4/42 (10%), p<0.01) but was not significant in nasal lavage (exacerbation 26/85 (31%) v stable 7/42 (17%), p=0.14). In patients with AE-COPD, fever was more frequent in those in whom viruses were detected (12/48, 25%) than in those in whom viruses were not detected (2/37, 5%, p=0.03).

CONCLUSION

Viral respiratory pathogens are found more often in respiratory specimens of hospitalised patients with AE-COPD than in control patients. Induced sputum detects respiratory viruses more frequently than nasal lavage in these patients. These data indicate that nasal lavage probably has no additional diagnostic value to induced sputum in cross-sectional studies on hospitalised patients with AE-COPD and that the role of viral infection in these patients is still underestimated.

Rhinovirus-induced wheezing in infancy--the first sign of childhood asthma?

BACKGROUND

Although known as common causes of upper respiratory infections, rhinoviruses, enteroviruses, and corona-viruses are poorly studied as inducers of wheezing in infants, and their possible role in the development of childhood asthma has not been investigated.

OBJECTIVE

The purposes of this study were to assess the occurrence of RV, enterovirus, and coronavirus infections in wheezing infants and to evaluate the association of these viral findings with early school-age asthma.

METHODS

In 1999, outcome in relation to asthma was studied in 82 of 100 initially recruited children who had been hospitalized for wheezing in infancy during the period 1992-1993. In 2000, etiologic viral studies regarding the index episode of wheezing were supplemented by rhinovirus, enterovirus, and coronavirus detection by RT-PCR from frozen nasopharyngeal aspirates in 81 of the children for whom adequate samples were available. Of these children, 66 had participated in the follow-up in 1999.

RESULTS

Rhinoviruses were identified in 27 (33%) of the 81 children, enteroviruses in 10 (12%), and coronaviruses in none. Rhinoviruses were present as single viral findings in 22 (81%) of the 27 rhinovirus-positive cases, and rhinovirus infections were associated with the presence of atopic dermatitis in infancy. Enteroviruses were commonly encountered in mixed infections and had no association with atopy. As single viral findings, rhinoviruses were associated with the development of asthma (P =.047; odds ratio, 4.14; 95% CI, 1.02-16.77 versus rhinovirus-negative cases [by logistic regression adjusted for age, sex, and atopic dermatitis on entry)].

CONCLUSION

Our results present rhinoviruses as important inducers of wheezing even in infancy. The association with atopy and subsequent asthma calls for reevaluation of the role of rhinoviruses in the development of asthma.

Lymphocyte and mast cell counts are increased in the nasal mucosa in symptomatic natural colds

Knowledge of the virus-induced immune response is important in understanding the pathophysiology of respiratory virus infections. Data on the cellular immune response is still limited and based mainly on experimental studies. Natural colds may differ in their pathophysiology from experimentally induced ones. To evaluate the inflammatory cell responses in the upper respiratory tract during natural colds we counted the number of lymphocytes, mast cells and macrophages in the nasal mucosa. Nasal biopsies were taken from 22 adult volunteers during the acute (2-4 days of symptoms) and convalescent phases (day 21) of the cold, and the numbers of cells were counted with immunohistochemical methods. Viral aetiology was identified in 14 (64%) subjects by using viral isolation, antigen detection and rhino-polymerase chain reaction assays. The number of T lymphocytes was increased in the nasal epithelium and that of T and B lymphocytes and mast cells in the subepithelial layer in the acute phase compared to the convalescent phase. Intraepithelial T lymphocyte counts were significantly higher in the subjects who had a proven viral infection or a finding of pathogenic bacteria in the nasopharynx compared to the subjects without such findings (P = 0.005 and P = 0.04, respectively). Contrary to the earlier experimental studies, we found that viruses cause accumulation of T and B lymphocytes and mast cells during the first days of a symptomatic naturally acquired respiratory infection.

Omalizumab, a recombinant humanized anti-IgE antibody, reduces asthma-related emergency room visits and hospitalizations in patients with allergic asthma

BACKGROUND

Prevention of serious asthma exacerbations is an important therapeutic goal in patients with asthma.

OBJECTIVE

The purpose of this study was to investigate the effect of omalizumab (Xolair), a recombinant humanized monoclonal anti-IgE antibody, on the rate of serious exacerbations during long-term therapy.

METHODS

A pooled analysis was completed of 3 multicenter, randomized, double-blind, placebo-controlled phase III studies with omalizumab in adults/adolescents aged > or =12 years (n = 1071) and in children aged 6 to 12 years (n = 334) who required treatment with inhaled corticosteroids for allergic asthma. Rates of serious asthma exacerbations were computed and compared between omalizumab- and placebo-treated patients. Serious exacerbations were those leading to unscheduled outpatient visits, emergency room treatment, or hospitalization during 1 year of treatment.

RESULTS

In all, 767 patients were treated with omalizumab (at least 0.016 mg/kg/IgE [IU/mL], administered subcutaneously every 4 weeks). Another 638 patients were treated with placebo. The rate of unscheduled, asthma-related outpatient visits was lower for the omalizumab-treated patients than for the placebo-treated patients (rate ratio [95% CI], 0.60 [0.44, 0.81]; P <.01), as were asthma-related emergency room visits (rate ratio [95% CI], 0.47 [0.24, 1.01]; P =.05). Importantly, hospitalizations for asthma were markedly reduced in patients receiving omalizumab (rate ratio [95% CI], 0.08 [0.00, 0.25]; P <.01).

CONCLUSION

Omalizumab reduces the rate of serious asthma exacerbations and the need for unscheduled outpatient visits, emergency room treatment, and hospitalization in patients with moderate-to-severe allergic asthma.

Neuraminidase inhibitors for preventing and treating influenza in children

BACKGROUND

During epidemic years, influenza attack rates in children exceed 40%. Options for prevention and treatment include immunisation, amantadine and rimantadine, and the neuraminidase inhibitors: zanamivir and oseltamivir.

OBJECTIVES

Our objective was to assess the efficacy, safety and tolerability of neuraminidase inhibitors in the treatment and prophylaxis of influenza infection in children.

SEARCH STRATEGY

We searched the Cochrane Acute Respiratory Infections Group Specialised Trials Register, the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, and the GlaxoSmithKline Clinical Trials Register, generally from inception through to December 2002. We also screened the references of retrieved articles and scrutinised relevant web sites. We also screened references of retrieved articles and other systematic reviews, scrutinised web sites of European and US regulatory bodies, and contacted manufacturers and authors.

SELECTION CRITERIA

Double-blind randomised controlled trials comparing neuraminidase inhibitors with placebo or other antiviral drugs in children less than 12 years of age. Additional safety and tolerability data from other sources were also included.

DATA COLLECTION AND ANALYSIS

Four reviewers applied the inclusion criteria to the retrieved studies, assessed trial quality and extracted data. Data were analysed separately for oseltamivir and zanamivir.

MAIN RESULTS

We identified three randomised controlled trials reporting data from 1500 children with a clinical case definition of influenza, of whom 798 had laboratory confirmed influenza infection. Two were trials of oseltamivir (in healthy children and in children with asthma) and one was a trial of zanamivir (in healthy children). Overall, trial quality was good. Oseltamivir reduced the median duration of illness by 26% (36 hours) in previously healthy children with laboratory confirmed influenza (p < 0.0001) and by 17% (21 hours) in the intention-to-treat population (p = 0.0002). Zanamivir reduced the median duration of illness by 24% (1.25 days) in previously healthy children with laboratory confirmed influenza (p < 0.001) and by 10% (0.5 days) in the intention-to-treat population (p = 0.011). Both drugs also significantly reduced the time to return to normal activity. Only oseltamivir produced a significant reduction in the complications of influenza (particularly otitis media), although there was a trend to benefit for zanamivir. No data on the use of zanamivir in 'at risk' children were available. The reduction in time to resolution of illness in 'at risk' children (with asthma) treated with oseltamivir was not statistically significant. Although we identified three trials of neuraminidase inhibitors in the prevention of influenza in families (including children), Roche and GlaxoSmithKline were not willing to break-out data for paediatric populations, and so no data were eligible for inclusion in the review. The adverse events profile of zanamivir was no worse than placebo and we found no reports of zanamivir-induced bronchospasm in children. Vomiting was more common in children treated with oseltamivir (p = 0.008), but study withdrawals were similar (<2%) between oseltamivir and placebo.

REVIEWER'S CONCLUSIONS

Neuraminidase inhibitors were effective in shortening illness duration and hastening return to normal activity in previously healthy children with a clinical or laboratory diagnosis of influenza. Oseltamivir was effective in reducing the incidence of secondary complications. Efficacy in 'at risk' children remains to be proven. The drugs are safe, but oseltamivir can cause vomiting.

Viral respiratory infections in association with asthma and sinusitis: a review

OBJECTIVE

Viral respiratory infections (VRIs) commonly precede asthma exacerbations in both children and adults. Likewise, VRIs may affect the paranasal sinuses, predisposing infected individuals to the development of subsequent acute bacterial sinusitis. This article discusses the role that viruses play in both the development of asthma and in acute asthma exacerbations. Mechanisms by which viral infections provoke asthma exacerbations are reviewed, and treatment of such episodes is discussed. The pathogenesis of sinusitis and association with VRIs is reviewed along with treatment recommendations.

DATA SOURCES

Relevant articles in the medical literature were reviewed with sources including randomized, controlled clinical trials, review articles, epidemiologic studies, and standard textbooks in allergy and immunology.

CONCLUSIONS

This review highlights the prominent role that viral pathogens (especially rhinovirus) play in exacerbation of asthma and in the development of sinus disease. The specific mechanisms whereby viral infection leads to an acute asthma exacerbation or to subsequent bacterial sinusitis are described. Treatment options are outlined including the potential future application of antiviral compounds.

Increased aeroallergen-specific interleukin-4-producing T cells in asthmatic adults

BACKGROUND

Asthma, atopy and some forms of respiratory syncytial virus (RSV) disease are thought to be caused by T cells making IL-4 (Th2 cells). However, not all patients with similar patterns of clinical disease have the same underlying pathogenesis and the ability to detect immunopathogenic T cells by examination of the peripheral blood remains in doubt. With the prospect of specific immunotherapy for diseases caused by T cell subsets, it is important to determine whether peripheral blood mononuclear cell (PBMC) reactivity can be used to establish the presence of immunopathogenic responses and therefore to predict therapeutic effects.

OBJECTIVE

To detect IL-4 and IFN-gamma production as markers of Th1 and Th2 responses in the peripheral blood of atopic and asthmatic adults.

METHODS

PBMC from 22 adult asthmatics (18 of whom were atopic) and 21 non-asthmatic volunteers (ten of whom were atopic) were stimulated with cat, birch and house dust mite allergens, human rhinovirus, RSV and recombinant chimaeric F/G protein from RSV in vitro. ELISPOT assays were used to enumerate cells producing IL-4 and IFN-gamma.

RESULTS

Asthmatics had a sixfold increase in frequencies of IL-4-producing cells to cat and birch allergen (median values: 37 vs. 7 per million PBMC, P < 0.01 and 20 vs. 3 per million PBMC, P < 0.04, respectively) compared to non-asthmatics. By contrast, non-asthmatic atopics showed no specific increase in antigen-specific IL-4 responses and there was no evident correlation between skin prick test reactivity and ELISPOT results. Atopics had significantly more IFN-gamma-producing cells specific for FG than nonatopics. while IFN-gamma and IL-4 responses to other antigens were not significantly different.

CONCLUSION

Enhanced IL-4 responses to non-viral aeroallergens are seen in adults with asthma, while enhanced IFN-gamma responses to viral antigen FG were see in atopics. In practical terms, ELISPOT assays for specific cytokines may provide a method that could be used to monitor antigen-specific T cell responses in peripheral blood.

The seasonality of rhinovirus infections and its implications for clinical recognition

BACKGROUND

Rhinoviruses are the most common cause of acute respiratory infections. Isolation of rhinoviruses occurs in a distinct and consistent seasonal pattern that can be used to help determine whether an acute respiratory illness is caused by a rhinovirus.

OBJECTIVE

This article reviews information on the seasonality of rhinovirus infection derived from early and recent studies of rhinovirus occurrence and treatment.

METHODS

PubMed was searched from 1965 to the present to identify all potentially relevant papers. The search terms used were rhinovirus and seasonality. A total of 1998 papers were screened.

RESULTS

Rhinoviruses comprise more than three quarters of viruses circulating in early autumn. In some years and perhaps some geographic areas, spring is an even more important time for rhinovirus transmission. Although overall rates of respiratory illness are lower in summer, rhinoviruses are the most frequently isolated virus at this time of year. Other viral agents, including influenza viruses and respiratory syncytial virus (particularly with parainfluenza virus), predominate in the winter. Thus, for most of the year, rhinoviruses are the cause of the majority of acute viral respiratory infections.

CONCLUSION

Understanding the seasonal incidence of rhinovirus infection may help determine how best to employ currently available antirhinoviral agents in patients presenting with symptoms of an acute viral respiratory infection.

[Difficult asthma in children]

Difficult asthma in children is defined as the persistence of exacerbations or frequent symptoms requiring rescue bronchodilator, or persistent airway obstruction in spite of treatment with inhaled steroid >/= 800 microg/d beclomethasone or equivalent and beta-2 long acting agonist. Management of difficult asthma in children first requires to identify conditions that may mimic asthma, asthma with bad compliance to treatment, and difficult asthma in relation with avoidable factors that worsen symptoms. The pathological bases of genuine difficult asthma remain unknown. Different patterns have been described according to the cells that are involved (eosinophil, neutrophil), the degree of airway remodeling, or the distal localization of the lesions. Difficult asthma requires specialized management including airway inflammation evaluation. Studies on bronchoalveolar lavage and bronchial mucosa biopsies will perhaps help to better understand the pathophysiology and to improve the management.

Reducing agents inhibit rhinovirus-induced up-regulation of the rhinovirus receptor intercellular adhesion molecule-1 (ICAM-1) in respiratory epithelial cells

Rhinoviruses are the major cause of common colds and of asthma exacerbations. Intercellular adhesion molecule-1 (ICAM-1) has a central role in airway inflammation and is the receptor for 90% of rhinoviruses. Rhinovirus infection of airway epithelium induces ICAM-1. Because redox state is directly implicated in inflammatory responses via molecular signaling mechanisms, here we studied the effects of reducing agents on rhinovirus-induced ICAM-1 expression, mRNA up-regulation, promoter activation, and nuclear factor activation. To investigate the effects of rhinovirus infection on the intracellular redox balance, we also studied whether rhinovirus infection triggers the production of reactive oxygen species. We found that reduced (GSH) but not oxidized (GSSG) glutathione (1-100 microM) inhibited in a dose-dependent manner rhinovirus-induced ICAM-1 up-regulation and mRNA induction in primary bronchial and A549 respiratory epithelial cells. GSH but not GSSG also inhibited rhinovirus-induced ICAM-1 promoter activation and rhinovirus-induced NF-kB activation. In parallel, we found that rhinovirus infection induced a rapid increase of intracellular superoxide anion that was maximal at the time of NF-kB activation. This oxidant generation was completely inhibited by GSH. We conclude that redox-mediated intracellular pathways represent an important target for the therapeutic control of rhinovirus-induced diseases.

Understanding the seasonal pattern of childhood asthma: results from the National Cooperative Inner-City Asthma Study (NCICAS)

OBJECTIVE

To contrast the seasonal patterns of asthma symptoms and utilization and determine the impact of allergen sensitivity, environmental tobacco smoke (ETS) exposure, and air pollution on the seasonal patterns of asthma.

STUDY DESIGN

Participants in the National Cooperative Inner-City Asthma Study (NCICAS) were tracked for approximately 4 years after allergen skin testing and determination of exposure to ETS. Air pollution data were obtained from EPA monitoring sites in NCICAS cities.

RESULTS

Asthma symptoms (wheeze) and health care utilization (unscheduled visits and hospitalization) had similar seasonal patterns, with low points during the summer months of June through August and a distinct autumn peak beginning in September. Seasonal patterns were similar among children with no allergen skin test reactivity, those reactive only to indoor allergens, and those reactive to outdoor allergens. ETS exposure, whether defined by self-report or urinary cotinine/creatinine ratio, was not related to the observed seasonal patterns. Among the pollutants evaluated, only the seasonal pattern of SO(2) coincided with that of asthma morbidity.

CONCLUSIONS

Atopy, ETS, and most air pollutants do not appear to contribute to the distinct asthma seasonal pattern. On a population level, changes in symptoms are mirrored by changes in utilization.