Respiratory infections: their role in airway responsiveness and the pathogenesis of asthma

Influenza A virus infection and cigarette smoke impair bronchodilator responsiveness to β-adrenoceptor agonists in mouse lung

β2-adrenoceptor agonists are the mainstay therapy for patients with asthma but their effectiveness in cigarette smoke (CS)-induced lung disease such as chronic obstructive pulmonary disease (COPD) is limited. In addition, bronchodilator efficacy of β2-adrenoceptor agonists is decreased during acute exacerbations of COPD (AECOPD), caused by respiratory viruses including influenza A. Therefore, the aim of the present study was to assess the effects of the β2-adrenoceptor agonist salbutamol (SALB) on small airway reactivity using mouse precision cut lung slices (PCLS) prepared from CS-exposed mice and from CS-exposed mice treated with influenza A virus (Mem71, H3N1). CS exposure alone reduced SALB potency and efficacy associated with decreased β2-adrenoceptor mRNA expression, and increased tumour necrosis factor α (TNFα) and interleukin-1β (IL-1β) expression. This impaired relaxation was restored by day 12 in the absence of further CS exposure. In PCLS prepared after Mem71 infection alone, responses to SALB were transient and were not well maintained. CS exposure prior to Mem71 infection almost completely abolished relaxation, although β2-adrenoceptor and TNFα and IL-1β expression were unaltered. The present study has shown decreased sensitivity to SALB after CS or a combination of CS and Mem71 occurs by different mechanisms. In addition, the PCLS technique and our models of CS and influenza infection provide a novel setting for assessment of alternative bronchodilators.

Seasons can influence the results of the methacholine challenge test

OBJECTIVE

This study tried to evaluate whether a methacholine test may be influenced by the seasons.

METHODS

We considered 4826 consecutive subjects with normal spirometry (50.53% males; age: 35.1±16.2; forced expiratory volume in one second: 99.5±13.0%) who underwent a methacholine test for suspected asthma symptoms between 2000 and 2010. They were subdivided into four groups, like the seasons, according to the test dates.

RESULTS

A total of 1981 (41%) resulted normal (no PD(20) was obtained with 2400 μg of methacholine); the others showed a mean LogPD(20) of 2.52±0.5 μg. The number of subjects with bronchial hyper-responsiveness (BHR) found in autumn (789, 62.3%) was higher than in summer (583, 56.7%; P=0.03). A higher number of females and overweight/obese subjects showed a BHR in autumn compared with the other seasons. The spring mean LogPD(20) value (2.48±0.48 μg) was lower if compared with the one measured in summer (2.59±0.49 μg; P=0.05). LogPD(20) value was lower in females and non-smokers in spring compared with summer (P<0.05). Overweight/obese non-smokers showed a lower LogPD(20) in spring and autumn compared with that in summer (P<0.05). Autumn was a risk factor (OR: 1.378; P=0.001) for BHR (using a PD(20) <2 400 μg as BHR limit), while spring (OR: 1.330; P=0.021) and autumn (OR: 1.331; P=0.020) were risk factors for a more severe BHR (using a PD(20) <400 μg as BHR limit).

CONCLUSION

There was a higher probability of finding BHR in outpatients with suspected asthma in autumn and spring compared with summer. Spring is the season where BHR may be more severe. Females and overweight/obese subjects were those mainly involved in this seasonal variability of BHR.

[Asthma: treatment of exacerbations]

INTRODUCTION

Exacerbations remain, in both adults and children, a common reason for emergency consultation. The management of the asthmatic patient with an acute exacerbation is well defined.

BACKGROUND

The initial evaluation, based on the background risk factors and the clinical examination, will determine the choice of treatment and management. Treatment is based on bronchodilators and corticosteroids in the majority of cases.

VIEWPOINTS

An episode of exacerbation may be the opportunity to establish contact with the patient (an educational approach) to improve the adherence to long-term treatment with inhaled corticosteroids, which remain the best way of preventing future exacerbations.

CONCLUSION

Early and appropriate management of exacerbations of asthma should reduce asthma morbidity and mortality. It could also reduce the socioeconomic costs of these episodes and the number and duration of hospital admissions.

Asthma and autoimmunity: a complex but intriguing relation

Asthma and autoimmune diseases apparently have little to share except for the involvement of the immune system in both types of disorder. However, epidemiological studies have shown that asthma and Type 1 diabetes, a typical autoimmune disease, are associated at the population level, and some experimental findings have suggested that autoimmune mechanisms might be operating in asthma as well. Female preponderance, increased incidence of antinuclear autoantibodies and detection of autoantibodies against either bronchial epithelial antigens or endothelial antigens in patients with nonallergic asthma suggest that the disease may have an autoimmune basis. Approximately 50% of patients with nonallergic asthma react to intradermal injection of autologous serum, indicating the presence of circulating vasoactive factors and suggesting an autoreactive mechanism. Recent findings in experimental animals support the involvement of an autoreactive mechanism in allergic asthma as well, indicating that human alpha-nascent polypeptide-associated complex, identified as an IgE-reactive autoantigen, has the potential to sensitize and induce immediate skin reactions and airway inflammation. In summary, asthma is a heterogeneous disorder characterized by chronic inflammation of the respiratory airways that can be triggered by allergen exposure or by other mechanisms, possibly autoreactive/autoimmune. The autoimmune hypothesis is further, indirectly, supported by the response to immunosuppressive drugs.

Seasonal variability of the methacholine challenge test

BACKGROUND

Since the intensity of some variables that influence bronchial hyper-responsiveness (BHR) varies across different seasons of the year, the percentage of positive metacholine challenge test (MCT) is theoretically subjected to seasonal variation. This study has looked at the seasonal variability of MCT among young adults with suspected asthma.

METHODS

The number of MCT performed and its corresponding proportion of positive results were retrospectively evaluated and compared for different seasons over a 5-year period.

RESULTS

Overall 645 subjects (mean age 21.4 +/- 2.3 yr) underwent MCT during the study period. Two-hundred nine MCTs (34.2%) were performed in the winter, significantly higher when compared to any other season of the year. Positive MCT (defined as PC(20) < 16 mg/mL) was noted in 163 patients (25.2%). The proportion of positive MCTs has shown significant seasonal trend, (p < 0.0001, chi-square test for trend), it was significantly higher in the winter and in the spring (32.2% and 32.4%, respectively) when compared with the summer (13.4%).

CONCLUSIONS

This study showed a significant seasonal variability for both pattern of referral to MCT and the seasonal prevalence of BHR young adults. These findings probably reflect seasonal variation in the intensity of external stimuli that involve in the pathogenesis of BHR, such as allergens burden and respiratory tract infections across the year. We suggest that interpretation of a positive MCT as predictive of BHR and of asthma should take into account the observed seasonal variability of the test.

Murine cytomegalovirus influences Foxj1 expression, ciliogenesis, and mucus plugging in mice with allergic airway disease

We have followed throughout time the development of allergic airway disease (AAD) in both uninfected mice and mice infected intranasally with murine cytomegalovirus (MCMV). Histological evaluation of lung tissue from uninfected mice with AAD demonstrated mucus plugging after 14 and 21 days of ovalbumin-aerosol challenge, with resolution of mucus plugging occurring by 42 days. In MCMV/AAD mice, mucus plugging was observed after 7 days of ovalbumin-aerosol challenge and remained present at 42 days. The level of interleukin-13 in bronchoalveolar lavage fluid from MCMV/AAD mice was decreased compared with AAD mice and was accompanied by increased levels of interferon-gamma. Levels of Muc5A/C, Muc5B, or Muc2 mucin mRNA in the lungs of MCMV/AAD mice were not elevated compared with AAD mice. MCMV was able to infect the airway epithelium, resulting in decreased expression of Foxj1, a transcription factor critical for ciliogenesis, and a loss of ciliated epithelial cells. In addition, an increase in the number of epithelial cells staining positive for periodic acid-Schiff was observed in MCMV/AAD airways. Together, these findings suggest that MCMV infection of the airway epithelium enhances goblet cell metaplasia and diminishes efficient mucociliary clearance in mice with AAD, resulting in increased mucus plugging.

Adenovirus IL-13-induced airway disease in mice: a corticosteroid-resistant model of severe asthma

Interleukin 13 (IL-13) is considered to be a key driver of the development of airway allergic inflammation and remodeling leading to airway hyperresponsiveness (AHR). How precisely IL-13 leads to the development of airway inflammation, AHR, and mucus production is not fully understood. In order to identify key mediators downstream of IL-13, we administered adenovirus IL-13 to specifically induce IL-13-dependent inflammation in the lungs of mice. This approach was shown to induce cardinal features of lung disease, specifically airway inflammation, elevated cytokines, AHR, and mucus secretion. Notably, the model is resistant to corticosteroid treatment and is characterized by marked neutrophilia, two hallmarks of more severe forms of asthma. To identify IL-13-dependent mediators, we performed a limited-scale two-dimensional SDS-PAGE proteomic analysis and identified proteins significantly modulated in this model. Intriguingly, several identified proteins were unique to this model, whereas others correlated with those modulated in a mouse ovalbumin-induced pulmonary inflammation model. We corroborated this approach by illustrating that proteomic analysis can identify known pathways/mediators downstream of IL-13. Thus, we have characterized a murine adenovirus IL-13 lung model that recapitulates specific disease traits observed in human asthma, and have exploited this model to identify effectors downstream of IL-13. Collectively, these findings will enable a broader appreciation of IL-13 and its impact on disease pathways in the lung.

Asthma

Asthma has been recognized as a disease since the earliest times. In the Corpus Hippocraticum, Hippocrates used the term “ασθμα” to indicate any form of breathing difficulty manifesting itself by panting. Aretaeus of Cappadocia, a well-known Greek physician (second century A.D.), is credited with providing the first detailed description of an asthma attack [13], and to Celsus it was a disease with wheezing and noisy, violent breathing. In the history of Rome, we find many members of the Julio-Claudian family affected with probable atopic respiratory disorders: Caesar Augustus suffered from bronchoconstriction, seasonal rhinitis as well as a highly pruritic skin disease. Claudius suffered from rhinoconjunctivitis and Britannicus was allergic to horse dander [529]. Maimonides (1136–1204) warned that to neglect treatment of asthma could prove fatal, whereas until the 19th century, European scholars defined it as “nervous asthma,” a term that was given to mean a defect of conductivity of the ninth pair of cranial nerves.

Nonspecific provocation of target organs in allergic diseases: EAACI-GA(2)LEN consensus report

It is widely accepted that nonspecific tissue reactivity is a distinct pathophysiological hallmark of allergic diseases, influenced by genetic and environmental factors different from those involved in causing sensitization and allergen response of target organs. This consensus document aims at reviewing procedures currently used for nonspecific provocation of the bronchi, nose and eye and for measuring their responsiveness to nonspecific stimuli.

Development of motavizumab, an ultra-potent antibody for the prevention of respiratory syncytial virus infection in the upper and lower respiratory tract

Respiratory syncytial virus (RSV) is the leading cause of viral bronchiolitis and pneumonia in infants and children. Currently, palivizumab is the only approved monoclonal antibody (mAb) for prophylaxis of RSV. However, a small percentage of patients are not protected by palivizumab; in addition, palivizumab does not inhibit RSV replication effectively in the upper respiratory tract. We report here the development and characterization of motavizumab, an ultra-potent, affinity-matured, humanized mAb derived from palivizumab. Several palivizumab variants that enhanced the neutralization of RSV in vitro by up to 44-fold were generated; however, in vivo prophylaxis of cotton rats with these antibodies conferred only about a twofold improvement in potency over palivizumab. This unexpected small increase of in vivo potency was caused by poor serum pharmacokinetics and lung bio-availability that resulted from unexpectedly broad tissue binding. Subsequent analyses revealed that changes at three amino acids arising from the affinity maturation markedly increased the non-specific binding to various tissues. Our results suggested that k(on)-driven mutations are more likely to initiate non-specific binding events than k(off)-driven mutations. Reversion of these three residues to the original sequences greatly diminished the tissue binding. The resulting mAb, motavizumab, binds to RSV F protein 70-fold better than palivizumab, and exhibits about a 20-fold improvement in neutralization of RSV in vitro. In cotton rats, at equivalent concentrations, motavizumab reduced pulmonary RSV titers to up to 100-fold lower levels than did palivizumab and, unlike palivizumab, motavizumab very potently inhibited viral replication in the upper respiratory tract. This affinity-enhanced mAb is being investigated in pivotal clinical trials. Importantly, our engineering process offers precious insights into the improvement of other therapeutic mAbs.

Incidência de infecção viral do trato respiratório em asma aguda atendida em sala de emergência

OBJETIVO: Avaliar a incidência de infecção viral em asma aguda em pacientes atendidos em setor de adultos de um serviço de emergência. MÉTODOS: Conduzimos um estudo de coorte de pacientes que se apresentaram com asma aguda no setor de adultos do Serviço de Emergência do Hospital de Clínicas de Porto Alegre (idade > 12 anos). Um aspirado nasofaríngeo foi obtido para detecção de antígenos com a técnica de coloração de imunofluorescência indireta para os vírus sincicial respiratório, adenovírus, influenza e parainfluenza tipos 1, 2, 3 e 4. Foram coletados dados referentes a características demográficas, história médica pregressa, crise que levou à atual visita ao serviço de emergência e desfechos da crise. RESULTADOS: No período de março a julho de 2004, 49 pacientes foram examinados para infecção viral do trato respiratório. Foram identificados vírus respiratórios em 6 pacientes (3 com adenovírus, 2 com influenza A e 1 com parainfluenza tipo 1). Os pacientes com infecção viral do trato respiratório apresentaram média de idade de 61,7 ± 11,5 anos, enquanto que os pacientes sem infecção viral apresentaram média de idade de 41,7 ± 20,9 anos (p = 0,027). Não houve outras diferenças significativas quanto às características clínicas e desfechos. CONCLUSÃO: Este estudo mostra uma incidência de 12,24% de infecção viral do trato respiratório na asma aguda em pacientes com idade igual ou maior que doze anos atendidos em sala de emergência, o que confirma a infecção viral como um desencadeante nessa faixa etária.

Susceptibility to allergic lung disease regulated by recall responses of dual-receptor memory T cells

BACKGROUND

Microbial infections are associated with the initial susceptibility to and flares of asthma. However, immunologic mechanisms whereby infections might alter the asthmatic phenotype are lacking.

OBJECTIVE

To test the hypothesis that memory T cells specific both for a viral antigen and an allergen could influence the pathogenesis of allergic disease in vivo .

METHODS

We developed a system in which 2 distinct T-cell receptors coexist on the T-cell surface, 1 specific for a virus and the other for an inhaled antigen.

RESULTS

We show that a population of dual-receptor T cells, polarized through a virus-specific T-cell receptor to contain T(H)1 or T(H)2 cells, can be reactivated through an unrelated T-cell receptor in recall responses in vivo . Quiescent memory cells derived from a T(H)1-polarized effector population blocked the development of airway hyperreactivity in a model of allergic lung disease, in association with decreased induction of chemokines and eosinophil recruitment. Conversely, reactivation of quiescent T(H)2 cells after inhalation of antigen or virus infection was sufficient to lead to the development of airway hyperresponsiveness and allergic pulmonary inflammation in mice whose lungs were previously normal.

CONCLUSION

These data provide evidence that dual-receptor memory T cells can regulate allergic disease susceptibility and suggest that they may play a role in mediating the influence of microbes on asthma pathogenesis.

Enhanced virulence, airway inflammation and impaired lung function induced by respiratory syncytial virus deficient in secreted G protein

BACKGROUND

Respiratory syncytial virus (RSV) infection can cause bronchial hyperresponsiveness and asthma exacerbations. In mice it results in airway inflammation and airway hyperresponsiveness. Since viral factors influencing these responses are not well defined, a study was undertaken to investigate the role of secreted G protein of human RSV in determining virulence, inflammatory responses, and changes in lung function.

METHODS

BALB/c mice were infected with a spontaneous mutant of RSV deficient in secreted G protein (RSV-DeltasG) or with wild type RSV (RSV-WT). Viral titres, numbers of pulmonary inflammatory cells, and concentrations of interferon (IFN)-gamma, interleukin (IL)-4, IL-5 and IL-10 in bronchoalveolar lavage (BAL) fluid were determined. Airway function was assessed at baseline and following methacholine provocation using barometric whole body plethysmography.

RESULT

Following infection with RSV-DeltasG, viral titres were increased 50-fold compared with RSV-WT. Influx of eosinophils and macrophages to the lung and concentrations of IFN-gamma and IL-10 in BAL fluid were also significantly higher following infection with RSV-DeltasG. Airway function, both at baseline and after methacholine provocation, was significantly decreased following infection with RSV-DeltasG compared with RSV-WT.

CONCLUSION

Secreted G protein is likely to be a regulatory factor in RSV infection limiting infectivity of the virus, inflammatory responses in the lungs, and reduction in lung function.

Psychological problems in Turkish asthmatic children and their families

BACKGROUND

Asthma is a chronic respiratory disorder characterized by recurrent episodes of impaired breathing. The disease causes psychological problems due to hospitalization, long-term medication use, and restricted social life.

OBJECTIVE

The aim of this study was to investigate the relationship between the severity and duration of asthma and psychological problems in asthmatic children, as well as the probability of maternal anxiety.

METHODS

Thirty-seven children with mild asthma, 55 with moderate asthma and eight with severe asthma were compared with 50 healthy children. The severity of asthma was evaluated using the Pearlman-Bierman classification. Psychological adjustment was measured using the Achenback child Behavior checklist and Spielberger's scale.

RESULTS

Emotional factors and family dynamics were found to be triggering factors for disease attacks in 16% of children with mild asthma, 38% of those with moderate asthma and 63% of those with severe asthma (p < 0.05). There was no significant difference in the mean maternal anxiety score between the disease severity groups (p > 0.05). The mean depression score was significantly higher in children with moderate and severe asthma than in those with mild asthma (p < 0.05). Disease duration showed no effect on depression and anxiety.

CONCLUSION

Both asthmatic children and their mothers are negatively affected by the disease.

Autocrine regulation of airway smooth muscle responsiveness

Bronchial asthma is characterized by airway inflammation, exaggerated airway narrowing to bronchoconstrictor agonists, and attenuated beta-adrenoceptor-mediated airway relaxation. Various cytokines/chemokines have been implicated in the pathogenesis of the airway inflammatory response, and certain cytokines, most notably including specific Th2-type cytokines and IL-1beta, have been shown to directly regulate airway smooth muscle (ASM) responsiveness. Recent evidence supports the concept that the ASM itself has the capacity to endogenously express a number of these cytokines under specific conditions of ASM sensitization. Moreover, these cytokines were found to act in an autocrine manner on the ASM to evoke the 'pro-asthmatic' phenotype of altered airway responsiveness. This cytokine-driven autocrine signaling mechanism in ASM may be triggered by either Fc receptor activation in the atopic (IgE-mediated) sensitized state or by ASM exposure to specific viral respiratory pathogens, most notably including rhinovirus. Furthermore, the autocrine-induced changes in ASM responsiveness are attributed to altered receptor-coupled transmembrane signaling in the sensitized ASM, resulting in perturbed expression and release of second messenger molecules that regulate ASM contraction and relaxation. Collectively, this evidence identifies mechanisms intrinsic to the ASM itself, including autocrine pro-inflammatory signaling and altered receptor/G protein-coupled second messenger activation, that importantly contribute to phenotypic expression of the changes in ASM responsiveness that characterize the asthmatic state.

Interleukin-6, interleukin-8, interleukin-11, and interferon-gamma levels in nasopharyngeal aspirates from wheezing children with respiratory syncytial virus or influenza A virus infection

The differences between respiratory syncytial virus (RSV) and influenza A virus (IFAV) in the pathogenesis of wheezing in young children have not been clearly defined. The aim of this study was to assess the contributions of RSV vs IFAV in the pathogenesis of upper airway inflammation in wheezy young children. We compared interleukin (IL)-6, IL-8, IL-11, and interferon-gamma (IFN-gamma) levels in nasopharyngeal aspirates (NPA) from non-asthmatic children with respiratory virus infections (RSV in 17 children and IFAV in 13 children), asthmatic children with viral infections (RSV in nine children, IFAV in 10 children), and 22 unaffected healthy children (controls). Levels of IL-11 in NPA from asthmatic children were significantly higher than those from non-asthmatic children with RSV infection, and RSV infection enhanced the IL-11 production in NPA significantly compared to IFAV infection. Nasopharyngeal epithelium from children with RSV infection secreted more IL-6 than that of children with IFAV infection. There was little difference in the IL-8 and IFN-gamma levels between asthmatic and non-asthmatic children with RSV or IFAV infection. In conclusion, asthma enhanced IL-11 production in RSV infection rather than IFAV infection in early childhood. There was a trend towards greater IL-6 production in RSV infection compared with IFAV infection.

RANTES may be predictive of later recurrent wheezing after respiratory syncytial virus bronchiolitis in infants

BACKGROUND

In vitro studies have shown that RANTES is strongly induced by respiratory syncytial virus (RSV) infection in cultures of upper airway epithelial cells. RANTES is known as a chemoattractant and activator for eosinophils.

OBJECTIVES

We performed this study to investigate whether RANTES is increased in the airway during naturally acquired RSV bronchiolitis. RANTES levels were then evaluated in relation to the severity of illness and later development of recurrent wheezing.

METHODS

We measured RANTES in nasal secretions of 30 patients with acute RSV bronchiolitis. Eosinophil cationic protein (ECP) was determined to evaluate the activation of eosinophils. The severity of illness was determined by the initial PaO2 values and the duration of wheezing. At a 1-year followup, all infants were re-evaluated if they had experienced subsequent wheezing, and we investigated if RANTES levels could predict the later development of recurrent wheezing.

RESULTS

Both RANTES and ECP in RSV bronchiolitis were significantly higher than in controls. There was a significant correlation between the levels of RANTES and ECP. RANTES was not significantly higher in patients with severe symptoms than in patients with mild symptoms. RANTES in infants who had experienced subsequent wheezing was significantly higher than in infants who had not.

CONCLUSIONS

Our results showed that RANTES is increased in nasal secretion during acute RSV bronchiolitis and suggest that high levels of RANTES may be predictive of later development of recurrent wheezing.

Lactic dehydrogenase virus (LDV) infection inhibits allergic eosinophil reaction in the airway

The effects of interferon (IFN)-gamma induced by virus infection on eosinophil reaction in allergic airway inflammation are not yet clear. We investigated the effects of lactic dehydrogenase virus (LDV) infection, which increases IFN -gamma production with no viral infection or replication in respiratory epithelium, on allergic airway hypersensitivity. LDV infection suppressed antigen-induced eosinophil recruitment into the airway in sensitized mice. IL -5 gene expression in bronchoalveolar lavage (BAL) cells was significantly suppressed in LDV -infected mice compared with uninfected controls. The numbers of total T cells and CD 4+ T cells were significantly reduced in LDV -infected mice compared with controls. The present results suggested that the increase in production of IFN -gamma by viral infection suppresses the eosinophil reaction, and this suppressive effect may be mediated by inhibition of the recruitment of CD 4+ T cell and IL -5 production.

Rhinovirus elicits proasthmatic changes in airway responsiveness independently of viral infection

BACKGROUND

Rhinovirus (RV), the principal pathogen responsible for the common cold, is importantly implicated in triggering attacks of asthma secondary to changes in airway responsiveness.

OBJECTIVE

Because the airway histopathologic features of RV infection are relatively modest, we tested the hypothesis that RV can directly elicit proasthmatic-like changes in airway smooth muscle (ASM) responsiveness independently of actual viral infection and its associated cytopathic effects.

METHODS

Isolated ASM tissues and cultured ASM cells were inoculated with either infectious or noninfectious (UV-irradiated) RV16 and RV2, the latter serotypes belonging to the "major" and "minor" groups of RV subtypes, respectively. ASM constrictor and relaxant responsiveness, G(i) protein expression, and proinflammatory cytokine release were subsequently compared under the different treatment conditions.

RESULTS

In contrast to RV2, which had no effect, RV16 inoculation elicited enhanced ASM contractility and impaired relaxation to cholinergic and beta-adrenergic agonists, respectively, in association with increased ASM membrane G(i) protein expression and induced release of the proinflammatory cytokines IL-5 and IL-1beta. These proasthmatic-like effects were also observed in ASM exposed to UV-irradiated RV16, wherein viral replication was completely inhibited. In contrast, pretreatment of ASM with a neutralizing antibody directed against ICAM-1, the host receptor for the "major" group of RVs, completely abrogated the proasthmatic effects of RV16.

CONCLUSIONS

The results demonstrate that (1) RV16 elicits proasthmatic changes in ASM responsiveness that can occur independently of actual viral infection of the ASM and (2) the effects of RV16 are attributed solely to binding of the virus to its host receptor (ICAM-1) on the ASM cell surface. Collectively, these findings support the notion that RV-induced exacerbation of wheezing in asthmatic individuals can occur even in the absence of any cytopathology associated with viral infection.

Role of latent viral infections in chronic obstructive pulmonary disease and asthma

Acute viral respiratory tract infections are well known to precipitate asthma attacks and acute exacerbations of chronic obstructive pulmonary disease, but their role in the pathogenesis of chronic disease is poorly defined. Double-stranded DNA viruses have the ability to persist in airway epithelial cells long after the acute infection has cleared. During these latent infections, viral genes are expressed at the protein level without replication of a complete virus. The expression of the adenoviral trans-activating protein has been demonstrated in the airway epithelium of both human and animal lungs and is associated with an amplification of the cigarette smoke-induced inflammatory response. Studies of cultured human airway epithelial cells have also shown that transfection with this viral gene upregulates the expression of intercellular adhesion molecule 1 and interleukin 8 by these cells when they are challenged with endotoxin. In guinea pigs, cigarette smoke-induced emphysema is amplified by latent adenoviral infection. Furthermore, this infection independently increased the number of CD-8 cells, whereas the cigarette smoke independently increased the number of CD-4 cells in the inflammatory infiltrate. On the other hand, allergen-induced lung inflammation was uninfluenced by latent adenoviral infection in the guinea pig, but the latent infection caused the eosinophilic component of this response to become steroid resistant. These studies suggest that latent adenoviral infections may have a role in the pathogenesis of obstructive airway disease by amplifying the response to cigarette smoke and inducing steroid resistance.

The role of age at asthma diagnosis in the development of triggers of asthma episodes

This study examined the relationship of age at asthma diagnosis to the subsequent impacts of 12 common asthma triggers, which we classified as either mainly physically based or strongly psychosocially mediated. The physically based triggers were air pollution, cigarette smoke, high humidity, high/low environmental temperature, allergy problems, respiratory infection, physical activity, and nighttime hours; the psychosocially mediated triggers were stress or worry, anger, excitement, and laughter. Data were collected with questionnaires from families with asthmatic children (n=115), 2 to 20 years of age, as part of a larger study of biological and psychosocial factors in asthma and other illnesses. Using parents' reports, we classified the children as early-diagnosed (before age 2) or later-diagnosed (at or after 2) for asthma and compared these groups, separated by gender, in 2 x 2 multivariate analyses. The impacts of all four psychosocially mediated triggers on asthma attacks were significantly greater for the later-diagnosed children than the early-diagnosed children. No age of diagnosis differences were found for any of the physically based triggers, and no gender or interaction effects were found for either type of trigger.

Role of tumor necrosis factor-alpha in endotoxin-induced lung parenchymal hyporesponsiveness in mice

Although changes in airway responsiveness in pulmonary inflammation are commonly related to the action of infiltrated leukocytes, our previous report suggested a direct role of inflammatory cytokines in LPS-induced lung hyporesponsiveness. The aim of this study was to define if cytokines detected in the BALF (bronchoalveolar lavage fluid) of intratracheal LPS-treated mice could be, at least in part, responsible for 5-HT (5-hydroxytryptamine) lung hyporeactivity. Our results show that intratracheal instillation of LPS induced a time-dependent increase in IL-(interleukin-)1beta, IL-6, and TNF (tumor necrosis factor)alpha in the BALF. Cytokine production was paralleled by 5-HT lung hyporesponsiveness, and intratracheal administration of TNFalpha proved to be very efficient in inhibiting 5-HT responsiveness. In addition, systemic treatment with rolipram, an inhibitor of TNFalpha production, was paralleled by a significant recovery of lung responsiveness. On the contrary, IL-1beta and IL-6 were not demonstrated to play a relevant role in 5-HT hyporesponsiveness. It is concluded that TNFalpha could be a crucial mediator of LPS-induced lung hyporesponsiveness.

Mechanism of cooperative effects of rhinovirus and atopic sensitization on airway responsiveness

To elucidate the mechanistic interplay between rhinovirus (RV) exposure and atopic sensitization in regulating airway smooth muscle (ASM) responsiveness, isolated rabbit ASM tissue and cultured human ASM cells were passively sensitized with sera from atopic asthmatic or nonatopic nonasthmatic (control) subjects in the absence and presence of inoculation with RV serotype 16. Relative to control subjects, atopic asthmatic serum-sensitized and RV-inoculated ASM exhibited significantly increased contractility to acetylcholine, impaired relaxation to isoproterenol, and enhanced release of the proinflammatory cytokine interleukin-1beta. These effects were potentiated in atopic asthmatic serum-sensitized ASM concomitantly inoculated with RV and inhibited by pretreating the tissues with monoclonal blocking antibodies against intercellular adhesion molecule (ICAM)-1 (CD54), the host receptor for RV serotype 16, or lymphocyte function-associated antigen (LFA)-1 (CD11a/CD18), the endogenous counterreceptor for ICAM-1. Moreover, RV inoculation was found to potentiate the induction of mRNA and surface protein expression of FcepsilonRII (CD23), the low-affinity receptor for IgE, in atopic asthmatic serum-sensitized ASM. Collectively, these observations provide new evidence demonstrating that 1) RV exposure and atopic sensitization act cooperatively to potentiate induction of proasthmatic changes in ASM responsiveness in association with upregulated proinflammatory cytokine release and FcepsilonRII expression and 2) the effects of RV exposure and atopic sensitization are mediated by cooperative ICAM-1-coupled LFA-1 signaling in the ASM itself.

Wheezing in early life and asthma at school age: predictors of symptom persistence

Early childhood wheezing is associated with asthma later in life. However, the high spontaneous recovery rate and the lack of firm predictors for persistence of wheezing complicates the development of evidence-based guidelines for long-term management of wheezy infants and toddlers. Our aim was to define variables that could be used to identify wheezy individuals younger than 3 years of age who would continue to be symptomatic at school age. The method used was a questionnaire-based cross-sectional survey of 2,027 randomly chosen, 6-13-year-old school children. Altogether 1,829 (90%) questionnaires were returned. Emergency medical care had been sought for 186 (10.2%) children for wheezing during the first 3 years of life, and only 17.2% of these children had received similar emergency treatment during the 12 months preceding the survey. The total proportion of children with current asthma at school age was 11.4%. A logistic regression analysis indicated that for the early wheezers, a family history of asthma, an itchy rash or food allergy, and exposure to tobacco smoke at home before the age of 3 years, were all independently associated with symptom persistence until school age. Among all wheezy children younger than 3 years, those who have a history of food allergy, itchy rash, asthma occurrence in a sibling or parent, or are exposed to tobacco smoke during the first years of life are at highest risk for symptom persistence until school age.

Wheezing following lower respiratory tract infections with respiratory syncytial virus and influenza A in infancy

We examined the incidence of subsequent wheezing in 292 children, hospitalized for influenza A or respiratory syncytial virus (RSV) lower respiratory tract infection, during two consecutive seasons (November-December, 1993 and March-April, 1995). Questionnaires concerning episodes of wheezing and known risk factors for wheezy bronchitis were mailed to parents 1 year after hospitalization. Sixty per cent of parents reported two or more episodes of wheezing following either influenza A or RSV. Hospitalization as a result of wheezing was necessary in 15% of the patients. The severity of the primary infection, as indicated by the need for treatment in the intensive care unit (ICU), was correlated with later wheezing. No additional significant risk factors predicting later wheezing could be identified.

Long-term effects of prednisolone in the acute phase of bronchiolitis caused by respiratory syncytial virus

Follow-up studies have demonstrated that bronchiolitis caused by respiratory syncytial virus (RSV) is strongly associated with wheezing in the ensuing years. During the acute infection the immune response may induce long-lasting detrimental effects, thereby contributing to post-bronchiolitis wheezing (PBW). Therefore, immune-modulating drugs like corticosteroids, administered in the acute phase of RSV bronchiolitis, may prevent PBW and asthma. To evaluate this, we performed a controlled prospective follow-up study after a randomized double-blind placebo-controlled intervention in the acute phase with oral prednisolone. Fifty-four patients under 2 years of age and hospitalized for RSV bronchiolitis between 1992 and 1995 were randomly assigned to prednisolone 1 mg/kg/day for 7 days or placebo. At the mean age of 5 years, 47 patients had completed their follow-up. Patients were divided into four groups: no wheezing, transient wheezing (wheezing during the first year of life); persistent wheezing (wheezing during the first year of life and asthma at the age of 5); and late-onset wheezing (no wheezing during the first year of life but asthma at the age of 5). Prevalence of wheezing and asthma were investigated through an interview by telephone, using a standardized questionnaire. We found no significant differences between the prednisolone- and the placebo-treated group in the number of patients with transient wheezing (8% vs. 17%), persistent wheezing (42% vs. 31%), or late-onset wheezing (17% vs. 13%). We conclude that oral prednisolone during the acute phase of RSV bronchiolitis is not effective in preventing PBW or asthma at the mean age of 5 years. Pediatr Pulmonol. 2000; 30: 92-96.

Is primary prevention of asthma possible?

The increased prevalence of asthma over the past quarter century has become a major public health problem for the industrialized world. Asthma is a disease process which has a strong heritable component which is impacted by multiple environmental factors. Given the rapid increase in asthma prevalence, it is difficult to ascribe the change to a genetic alteration. Therefore, the focus for understanding the changing prevalence of asthma must be on environmental factors. This article reviews factors which may contribute, in whole or in part, to the development of the disease process. In questioning whether it is possible to prevent development of a disease (primary prevention), it is critical to understand these factors. The environment may even have an impact on the fetus during intrauterine life. There does appear to be a "window of opportunity" in early life where a variety of factors, including food and inhalant allergen exposure, exposure to pollutants, and infection with both viral and bacterial agents, may be important in initiating the development of asthma and allergy. Potential approaches to primary prevention of asthma and allergy must consider each of these important factors. Given that asthma is a multifactorial disease with both complex genetic and environmental components, it is unlikely that any single intervention will significantly decrease the prevalence of asthma.

Autocrine cytokine signaling mediates effects of rhinovirus on airway responsiveness

The airway responses to allergen exposure in allergic asthma are qualitatively similar to those elicited by specific viral respiratory pathogens, most notably rhinovirus (RV), suggesting that the altered airway responsiveness seen in allergic asthma and that elicited by viral respiratory tract infection may share a common underlying mechanism. To the extent that T helper cell type 2 (Th2) cytokines have been implicated in the pathogenesis of allergic asthma, this study examined the potential role(s) of Th2-type cytokines in mediating pro-asthmatic-like changes in airway smooth muscle (ASM) responsiveness after inoculation of naive ASM with human RV. Isolated rabbit ASM tissues and cultured human ASM cells were exposed to RV (serotype 16) for 24 h in the absence and presence of monoclonal blocking antibodies (MAbs) or antagonists directed against either the Th2-type cytokines interleukin (IL)-4 and IL-5, intercellular adhesion molecule (ICAM)-1 (the endogenous host receptor for most RVs), or the pleiotropic proinflammatory cytokine IL-1beta. Relative to control (vehicle-treated) tissues, RV-exposed ASM exhibited significantly enhanced isometric contractility to acetylcholine and impaired relaxation to isoproterenol. These pro-asthmatic-like changes in ASM responsiveness were ablated by pretreating the RV-exposed tissues with either IL-5-receptor-alpha blocking antibody or human recombinant IL-1-receptor antagonist, whereas IL-4 neutralizing antibody had no effect. Extended studies further demonstrated that inoculation of ASM cells with RV elicited 1) an increased mRNA expression and release of IL-5 protein, which was inhibited in the presence of anti-ICAM-1 MAb, and 2) an enhanced release of IL-1beta protein, which was inhibited in the presence of IL-5 receptor-alpha antibody. Collectively, these observations provide new evidence demonstrating that RV-induced changes in ASM responsiveness are largely attributed to ICAM-1-dependent activation of a cooperative autocrine signaling mechanism involving upregulated IL-5-mediated release of IL-1beta by the RV-exposed ASM itself.

The role of viruses in development or exacerbation of atopic asthma

Respiratory viral infections in early childhood have been linked to the development of persistent wheezing and asthma. Epidemiologic data indicate that, for the majority of children, virus-induced wheezing is a self-limited condition, with no long-term consequences. For a substantial minority, however, virus-induced wheezing is associated with persistent asthma and the potential for enhanced allergic sensitization. For the most part, this subset of patients is genetically predisposed; they are atopic children in whom respiratory viral infections trigger the early development of asthma by mechanisms that have not been fully elucidated. Both inflammatory and noninflammatory mechanisms may be involved. It does not appear that viral infection per se in early life is responsible for the induction of atopic asthma. Data from animal models provide support for the concept that enhanced allergic sensitization caused by increased uptake of allergen during infection may play a critical role, as well as T-cell-mediated immune responses to viral infection, which may favor eosinophilic inflammatory responses and the development of altered airway function to inhaled methacholine. Recent advances in our understanding of the interactions between respiratory viruses and the development of reactive airway disease offer new possibilities for preventive treatment in children at risk for developing persistent wheezing and asthma exacerbation as a result of viral infection.

Nordic consensus report on asthma management. Nordic Asthma Consensus Group

The work with the Nordic consensus report on asthma management started some years ago. The Nordic countries have common socioeconomic conditions. We acknowledge the international as well as other European guidelines providing valuable recommendations. Nevertheless, we felt the need to combine the common Nordic experiences in order to have a local statement of asthma and asthma care, based upon Nordic clinical science and tradition. The work has been rewarding and we acknowledge many valuable contributions from paediatricians, allergologists and lung physicians in all Nordic countries. The response has so far been positive and we feel that the present material reflects the main opinion of Nordic physicians taking care of asthma patients of all ages. However, the asthma and allergy research field is rapidly developing. Thus, this document should merely be regarded as a time-limited contribution to the continuing scientific discussion of this fascinating field.

Tests of the relationship between children's temperament and asthma and of the reliability and validity of the Brief Scale of Temperament

Two studies are reported. One examined the reliability and validity of a brief scale to measure children's temperament; the other tested the relationship of early temperament and the development of asthma. In Study 1, principal caretakers of 46 4- to 7-year-olds, usually the mothers, filled out questionnaires containing the Brief Scale of Temperament (BST) and the Behavioral Style Questionnaire. The caretakers did this twice, about 1 week apart. The first time the children's recent temperament was assessed, and the second time past (> 1 year) temperament was assessed. Internal consistency and correlational analyses revealed substantial reliability and validity for BST assessments of recent and past temperament. Study 2 incorporated the BST in a large-scale survey of 325 families, with parents providing data on their children's asthma and temperament. BST assessments of early (past) temperament were made retrospectively regarding the child's first few years. Comparisons of early temperament revealed no differences between children who developed asthma and those who did not in their overall scores on the BST or for any of the temperament characteristics it measures. In addition, correlational analyses of data for asthmatics showed that early temperament was not related to ratings of the severity of the asthma condition the children developed or the impacts of any of 12 specific asthma triggers, including any involving emotional states, such as stress or worry.

Serious childhood respiratory infections and asthma in adult life. A population based study. ECRHS Italy. European Community Respiratory Health Survey

BACKGROUND

A number of epidemiologic studies have tried to establish whether respiratory tract infections in early childhood cause obstructive pulmonary disease in adult life.

OBJECTIVE

To determine whether reported serious respiratory infection before the age of 5 years (SRI) is a significant risk factor for subsequent development of bronchial asthma and/or bronchial hyperresponsiveness in adults.

METHODS

We investigated a random population sample of 1,104 subjects (aged 20 to 40 years), participating in the European Respiratory Health Survey in Italy. Bronchial response to methacholine and answers to a standardized questionnaire were analyzed.

RESULTS

The prevalence of SRI (ie, a positive response to the question "Have you ever had a serious respiratory infection before the age of 5 years?") was significantly higher in the subjects with a positive family history of allergic diseases than in those with a negative one (O.R. 1.89; 95% C.I. 1.24 to 2.87, P < .01). No relationship was found between SRI and current adult asthma; however, asthma in the past was found in 20.5% of the SRI positive subjects and in 9.1% of SRI negative subjects (O.R. 2.47; 95% C.I. 1.47 to 4.15, P < .05). No difference in the response to methacholine and in FEV1, FEV1/FVC values was found between SRI positive and SRI negative subjects.

CONCLUSIONS

We suggest that a positive family history of atopy is associated with a significantly higher prevalence of SRI. Furthermore our results indicate that exposure to SRI is a risk factor for asthma in the past (ie, asthma in childhood and adolescence) but not for adult asthma or for the development of bronchial impairment in adult life.

Rhinovirus-mediated changes in airway smooth muscle responsiveness: induced autocrine role of interleukin-1beta

An important interplay exists between specific viral respiratory pathogens, most commonly rhinovirus (RV), and altered airway responsiveness in the development and exacerbations of asthma. Given that RV infection reportedly induces the release of various cytokines in different cell types and that the reported effects of RV on airway smooth muscle (ASM) responsiveness are highly comparable to those obtained in ASM exposed to the proinflammatory cytokine interleukin (IL)-1beta, this study examined whether RV (serotype 16)-mediated pertubations in ASM responsiveness are mechanistically coupled to altered induced expression and action of IL-1beta in RV-exposed isolated rabbit and human ASM tissue and cultured cells. Relative to control tissues, ASM inoculated with RV exhibited significantly increased maximal isometric contractility to ACh (P < 0.01) and attenuated relaxation to isoproterenol (P < 0. 005). In extended studies, we found that 1) the RV-induced changes in ASM responsiveness were ablated by pretreating the tissues with the IL-1 recombinant human receptor antagonist; 2) in contrast to their respective controls, RV-inoculated ASM tissue and cultured cells exhibited progressively induced expression of IL-1beta mRNA and elaboration of IL-1beta protein at 6 and 24 h after viral exposure; and 3) the latter effect of RV was inhibited in the presence of a monoclonal antibody to intercellular adhesion molecule-1, the endogenous receptor for most RV. Collectively, these observations provide new evidence demonstrating that "pro-asthmatic-like" pertubations in agonist responsiveness elicited in RV-exposed ASM are largely attributed to the induced autologous expression and autocrine action of IL-1beta in the virus-infected ASM.

Review of psychosocial stress and asthma: an integrated biopsychosocial approach

Environmental stressors may impact asthma morbidity through neuroimmunological mechanisms which are adversely impacted and/or buffered y social networks, social support, and psychological functioning. In addition, life stress may impact on health beliefs and behaviours that may affect asthma management. Whereas earlier psychosomatic models have supported a role for psychological stress in contributing to variable asthma morbidity among those with existing disease, a growing appreciation of the interactions between behavioural, neural, endocrine, and immune processes suggest a role for these psychosocial factors in the genesis of asthma as well. While a causal link between stress and asthma has not bee established, this review provides a framework in which we can begin to see links between these systems that might provide new insights to guide future explorations. The complexity of these interactions underscore the need for a multidisciplinary approach which combines the idea that the origin of asthma is purely psychogenic in nature with the antithetical consideration that the biological aspects are all important. These distinctions are artificial, and future research that synthesizes biological, psychological, sociocultural, and family parameters is urgently needed to further our understanding of the rising burden of asthma.

CD8 T Cells Are Essential in the Development of Respiratory Syncytial Virus-Induced Lung Eosinophilia and Airway Hyperresponsiveness

Viral respiratory infections can cause bronchial hyperresponsiveness and exacerbate asthma. In mice, respiratory syncytial virus (RSV) infection results in airway hyperresponsiveness (AHR) and eosinophil influx into the airways. The immune cell requirements for these responses to RSV infection are not well defined. To delineate the role of CD8 T cells in the development of RSV-induced AHR and lung eosinophilia, we tested the ability of mice depleted of CD8 T cells to develop these symptoms of RSV infection. BALB/c mice were depleted of CD8 T cells using anti-CD8 Ab treatment before intranasal administration of infectious RSV. Six days postinfection, airway responsiveness to inhaled methacholine was assessed by barometric body plethysmography, and numbers of lung eosinophils and levels of IFN-γ, IL-4, and IL-5 in bronchoalveolar lavage fluid were monitored. RSV infection resulted in airway eosinophilia and AHR in control mice, but not in CD8-depleted animals. Further, whereas RSV-infected mice secreted increased amounts of IL-5 into the airways as compared with noninfected controls, no IL-5 was detectable in both bronchoalveolar lavage fluid and culture supernatants from CD8-depleted animals. Treatment of CD8-depleted mice with IL-5 fully restored both lung eosinophilia and AHR. We conclude that CD8 T cells are essential for the influx of eosinophils into the lung and the development of AHR in response to RSV infection.

IL-5 and Eosinophils Are Essential for the Development of Airway Hyperresponsiveness Following Acute Respiratory Syncytial Virus Infection

Viral respiratory infections can cause bronchial hyperresponsiveness and exacerbate asthma. In mice, respiratory syncytial virus (RSV) infection, which induces an immune response dominated by IFN-γ, results in airway hyperresponsiveness (AHR) and eosinophil influx into the airways, both of which are prevented by pretreatment with anti-IL-5 Ab. To delineate the role of IL-5, IL-4, and IFN-γ in the development of RSV-induced AHR and lung eosinophilia, we tested the ability of mice deficient in each of these cytokines to develop these symptoms of RSV infection. Mice deficient in either IL-5, IL-4, or IFN-γ were administered infectious RSV intranasally, and 6 days later, airway responsiveness to inhaled methacholine was assessed by barometric body plethysmography, and numbers of lung eosinophils and production of IFN-γ, IL-4, and IL-5 by mononuclear cells from peribronchial lymph nodes were monitored. RSV infection resulted in airway eosinophilia and AHR in both IL-4- and IFN-γ-deficient mice, but not in IL-5-deficient mice. Reconstitution of IL-5-deficient mice with IL-5 restored these responses and enhanced the responses in IL-4-deficient mice. Anti-VLA-4 (very late Ag-4) treatment prevented lung eosinophilia and AHR following RSV infection and IL-5 reconstitution. We conclude that in response to RSV, IL-5 is essential for the influx of eosinophils into the lung and that eosinophils in turn are critical for the development of AHR. IFN-γ and IL-4 are not essential for these responses to RSV infection.

Mechanism of rhinovirus-induced changes in airway smooth muscle responsiveness

An important interplay exists between specific viral respiratory infections and altered airway responsiveness in the development and exacerbations of asthma. However, the mechanistic basis of this interplay remains to be identified. This study addressed the hypothesis that rhinovirus (RV), the most common viral respiratory pathogen associated with acute asthma attacks, directly affects airway smooth muscle (ASM) to produce proasthmatic changes in receptor-coupled ASM responsiveness. Isolated rabbit and human ASM tissue and cultured ASM cells were inoculated with human RV (serotype 16) or adenovirus, each for 6 or 24 h. In contrast to adenovirus, which had no effect, inoculation of ASM tissue with RV induced heightened ASM tissue constrictor responsiveness to acetylcholine and attenuated the dose-dependent relaxation of ASM to beta-adrenoceptor stimulation with isoproterenol. These RV-induced changes in ASM responsiveness were largely prevented by pretreating the tissues with pertussis toxin or with a monoclonal blocking antibody to intercellular adhesion molecule-1 (ICAM-1), the principal endogenous receptor for most RVs. In extended studies, we found that the RV-induced changes in ASM responsiveness were associated with diminished cAMP accumulation in response to dose-dependent administration of isoproterenol, and this effect was accompanied by autologously upregulated expression of the Gi protein subtype, Gialpha3, in the ASM. Finally, in separate experiments, we found that the RV-induced effects on ASM responsiveness were also accompanied by autologously induced upregulated mRNA and cell surface protein expression of ICAM-1. Taken together, these findings provide new evidence that RV directly induces proasthmatic phenotypic changes in ASM responsiveness, that this effect is triggered by binding of RV to its ICAM-1 receptor in ASM, and that this binding is associated with the induced endogenously upregulated expression of ICAM-1 and enhanced expression and activation of Gi protein in the RV-infected ASM.

Relationships among respiratory infections, triggers of attacks, and asthma severity in children

The present study of asthmatic children examined relationships among the frequencies of prior respiratory infections (i.e., those prior to the development of asthma) and recent (past year) respiratory infections, asthma severity, and the impacts of 12 common asthma triggers: air pollution, allergy problems, anger, cigarette smoke, excitement, high humidity, high or low environmental temperature, laughter, nighttime hours, physical activity, respiratory infection, and stress or worry. Data on these variables were obtained through a survey in which 325 families completed questionnaires; 121 families had asthmatic children who were 2-20 years of age. Pearson correlational analyses revealed many significant positive correlations: The frequencies of prior and recent infections were correlated. The frequency of prior infections was correlated with the impacts of all asthma triggers except allergy problems, but the frequency of recent infections was correlated only with the impacts of air pollution, cigarette smoke, respiratory infection, and nighttime hours as triggers of asthma attacks. Asthma severity was correlated with the frequencies of prior and recent respiratory infections and with the impact of respiratory infection as an asthma trigger.

The effect of fluticasone propionate on respiratory syncytial virus-induced chemokine release by a human bronchial epithelial cell line

Respiratory syncytial virus (RSV) is an important cause of bronchiolitis in infants, is an important trigger of asthma exacerbation, and stimulates chemokine production by human respiratory epithelial cells in vitro. We tested the effect of the corticosteroid fluticasone propionate (FP) on RSV-stimulated production of the chemokines interleukin 8 (IL-8) and RANTES (regulated upon activation, normal T cell expressed and secreted) by a human bronchial epithelial cell line, BEAS-2B. Confluent BEAS-2B cultures were inoculated with RSV at approximately 1 plaque-forming unit/cell, and media were collected at 24 h intervals. Concentrations of IL-8 and RANTES were measured in supernatants using ELISA. The effect of FP at varying concentrations on RSV-induced chemokine release was determined. RSV stimulated increased release of both IL-8 and RANTES, particularly at 24-48 h after virus inoculation. Significant but incomplete inhibition of RSV-stimulated increases for both chemokines was found when cultures were treated with FP at > or = 10(-8) M (for IL-8) or > or = 10(-7) M (for RANTES). There was no significant effect of FP on release of RSV itself from infected BEAS-2B cells. We conclude that a possible mechanism for the efficacy of inhaled corticosteroids in reducing the frequency or severity of asthma exacerbations is inhibition of virus-induced chemokine production by airway cells.

Immunoglobulin E and G responses to pertussis toxin in children immunised with adsorbed and non-adsorbed whole cell pertussis vaccines

The IgE and IgG responses to pertussis toxin were measured in blood samples from 70 children (age 1.5-2.9 years) after primary immunisation with either a non-aluminium adsorbed, whole cell vaccine (n = 34) or an aluminium adsorbed whole cell vaccine (n = 36). Two years later, they received a booster immunisation with either the non-adsorbed (n = 24) or the aluminium adsorbed vaccine (n = 14). Neutralising antibodies to pertussis toxin were higher (P < 0.05) after the three priming doses of the adsorbed vaccine than of the non-adsorbed vaccine, although both groups showed > 90% seropositives after the third dose. IgE antibodies to PT (PT-IgE) were detected in samples from 11/52 children after completed primary immunisation and the levels were low (median < or = 0.1 PRU ml-1) in both groups. No significant differences between the groups were found. PT-IgE levels did not increase after the booster injection. Thus, the aluminium content of the whole cell vaccines influenced the IgG response but not the IgE responses to pertussis toxin. The high rates of PT-IgE responses noted after a booster dose of acellular or whole cell pertussis vaccine to children primed with acellular vaccine in previous studies can therefore be mainly ascribed to the nature of the priming vaccine rather than the aluminium adjuvant.