Viral respiratory tract infection and exacerbations of asthma in adult patients

Asthma exacerbations and airway redox imbalance under type 2 inflammatory conditions

Asthma is a chronic inflammatory airway disease characterized by bronchial hyperresponsiveness and reversibility. Despite considerable advances in asthma treatment based on our understanding of its pathophysiology, asthma exacerbations remain challenging. To reduce asthma exacerbations, it is essential to identify triggers, patients' risk factors, and underlying mechanisms. While exposure to viruses and environmental stimuli are known common triggers for asthma exacerbations, the key factors involved in asthma exacerbations have been identified as type 2 inflammation. Type 2 inflammatory biomarkers have been demonstrated to be useful in predicting individuals at risk of exacerbations. Furthermore, recent clinical trials of targeted biological therapy, which blocks the type 2 pathway, have supported the critical role of type 2 inflammation in asthma exacerbations. Although the specific mechanisms linking type 2 inflammation to asthma exacerbations have not yet been fully elucidated, increasing evidence shows that reduction/oxidation (redox) imbalance likely plays an important role in this association. Under type 2 inflammatory conditions, human airway epithelial cells activate 15-lipoxygenase-1 in complex with phosphatidylethanolamine binding protein-1, leading to the generation of electrophilic hydroperoxyl-phospholipids. When the accumulation of reactive lipid peroxidation surpasses a specific glutathione-dependent activity, these electrophilic compounds are not neutralized, leading to programmed cell death, ferroptosis. Reduced glutathione levels, caused by type 2 inflammation, may impair its ability to neutralize reactive lipid peroxidation. The accumulation of lipid peroxidation with intracellular redox imbalance may contribute to asthma exacerbations in individuals with type 2 inflammation. Inhibiting the ferroptotic pathway holds promise as a therapeutic strategy to alleviate asthma exacerbations.

Understanding the Burden of Respiratory Syncytial Virus in Older Adults in Latin America: An Expert Perspective on Knowledge Gaps

Respiratory syncytial virus (RSV) is a significant global health concern and major cause of hospitalization, particularly among infants and older adults. The clinical impact of RSV is well characterized in infants; however, in many countries, the burden and risk of RSV in older populations are overlooked. In Latin America, there are limited data on RSV epidemiology and disease management in older adults. Therefore, the impact of RSV in this region needs to be addressed. Here, current insights on RSV infections in older populations in Latin America, including those with underlying health conditions, are discussed. We also outline the key challenges limiting our understanding of the burden of RSV in Latin America in a worldwide context and propose an expert consensus to improve our understanding of the burden of RSV in the region. By so doing, we aim to ultimately improve disease management and outcomes of those at risk and to alleviate the impact on healthcare systems.A graphical plain language summary is available with this article.

Natural Killer Cells and Host Defense Against Human Rhinoviruses Is Partially Dependent on Type I IFN Signaling

Rhinovirus (RV), the causative agent of the common cold, causes only mild upper respiratory tract infections in healthy individuals, but can cause longer lasting and more severe pulmonary infections in people with chronic lung diseases and in the setting of immune suppression or immune deficiency. RV-infected lung structural cells release type I interferon (IFN-I), initiating the immune response, leading to protection against viruses in conjunction with migratory immune cells. However, IFN-I release is deficient in some people with asthma. Innate immune cells, such as natural killer (NK) cells, are proposed to play major roles in the control of viral infections, and may contribute to exacerbations of chronic lung diseases, such as asthma. In this study, we characterized the NK cell response to RV infection using an in vitro model of infection in healthy individuals, and determined the extent to which IFN-I signaling mediates this response. The results indicate that RV stimulation in vitro induces NK cell activation in healthy donors, leading to degranulation and the release of cytotoxic mediators and cytokines. IFN-I signaling was partly responsible for NK cell activation and functional responses to RV. Overall, our findings suggest the involvement of NK cells in the control of RV infection in healthy individuals. Further understanding of NK cell regulation may deepen our understanding of the mechanisms that contribute to susceptibility to RV infections in asthma and other chronic lung diseases.

In vivo experimental models of infection and disease

Human and animal models continue to play a crucial role in research to understand host immunity to rhinovirus (RV) and identify disease mechanisms. Human models have provided direct evidence that RV infection is capable of exacerbating chronic respiratory diseases and identified immunological processes that correlate with clinical disease outcomes. Mice are the most commonly used nonhuman experimental RV infection model. Although semipermissive, under defined experimental conditions sufficient replication occurs to induce host immune responses that recapitulate immunity and disease during human infection. The capacity to use genetically modified mouse strains and drug interventions has shown the mouse model to be an invaluable research tool defining causal relationships between host immunity and disease and supporting development of new treatments. Used in combination the insights achieved from human and animal experimental infection models provide complementary insights into RV biology and yield novel therapeutic options to reduce the burden of RV-induced disease.

Neonatal Immunity, Respiratory Virus Infections, and the Development of Asthma

Infants are exposed to a wide range of potential pathogens in the first months of life. Although maternal antibodies acquired transplacentally protect full-term neonates from many systemic pathogens, infections at mucosal surfaces still occur with great frequency, causing significant morbidity and mortality. At least part of this elevated risk is attributable to the neonatal immune system that tends to favor T regulatory and Th2 type responses when microbes are first encountered. Early-life infection with respiratory viruses is of particular interest because such exposures can disrupt normal lung development and increase the risk of chronic respiratory conditions, such as asthma. The immunologic mechanisms that underlie neonatal host-virus interactions that contribute to the subsequent development of asthma have not yet been fully defined. The goals of this review are (1) to outline the differences between the neonatal and adult immune systems and (2) to present murine and human data that support the hypothesis that early-life interactions between the immune system and respiratory viruses can create a lung environment conducive to the development of asthma.

Modeling TH 2 responses and airway inflammation to understand fundamental mechanisms regulating the pathogenesis of asthma

In this review, we highlight experiments conducted in our laboratories that have elucidated functional roles for CD4⁺ T-helper type-2 lymphocytes (T_H 2 cells), their associated cytokines, and eosinophils in the regulation of hallmark features of allergic asthma. Notably, we consider the complexity of type-2 responses and studies that have explored integrated signaling among classical T_H 2 cytokines (IL-4, IL-5, and IL-13), which together with CCL11 (eotaxin-1) regulate critical aspects of eosinophil recruitment, allergic inflammation, and airway hyper-responsiveness (AHR). Among our most important findings, we have provided evidence that the initiation of T_H 2 responses is regulated by airway epithelial cell-derived factors, including TRAIL and MID1, which promote T_H 2 cell development via STAT6-dependent pathways. Further, we highlight studies demonstrating that microRNAs are key regulators of allergic inflammation and potential targets for anti-inflammatory therapy. On the background of T_H 2 inflammation, we have demonstrated that innate immune cells (notably, airway macrophages) play essential roles in the generation of steroid-resistant inflammation and AHR secondary to allergen- and pathogen-induced exacerbations. Our work clearly indicates that understanding the diversity and spatiotemporal role of the inflammatory response and its interactions with resident airway cells is critical to advancing knowledge on asthma pathogenesis and the development of new therapeutic approaches.

Routine Use of Budesonide/Formoterol Fixed Dose Combination in Elderly Asthmatic Patients: Practical Considerations

Asthma has been demonstrated to be as common in the elderly as in younger age groups. Although no specific recommendations exist to manage the disease differently in older individuals, functional features and clinical presentations may be affected by age per se, and by age-related conditions, such as comorbidities and polypharmacy. In this review article, we aimed to explore the efficacy and safety in elderly asthmatic patients of one of the most currently used inhaled treatments for asthma, that is, the fixed-dose combination of budesonide/formoterol. We attempted to address some practical questions that are relevant to the daily practice of clinicians. We focused on the efficacy and real-world effectiveness of inhaled corticosteroids and long-acting β-adrenergic bronchodilators (ICS/LABA) as treatment in the elderly population, since data are extrapolated from younger populations. We investigated whether a maintenance and reliever therapy approach is more effective in the elderly as opposed to maintenance regimens, from both the general practitioner's and the pulmonologist's perspective. To address these questions, we scanned electronic databases (PubMed, MEDLINE, Embase, Scopus and Google Scholar) from the date of inception up to October 2016 with a cross-search using the following keywords: 'asthma', 'elderly', 'SMART therapy', 'MART therapy', 'Turbuhaler', and 'budesonide/formoterol'. The available literature on the topic confirms that when the age-associated changes are properly managed in clinical practice, asthma in older populations can be optimally controlled with inhaled treatment including ICS/LABA. This also applies for the budesonide/formoterol fixed combination, thus allowing for the maintenance and reliever therapy approach.

Mouse models of severe asthma: Understanding the mechanisms of steroid resistance, tissue remodelling and disease exacerbation

Severe asthma has significant disease burden and results in high healthcare costs. While existing therapies are effective for the majority of asthma patients, treatments for individuals with severe asthma are often ineffective. Mouse models are useful to identify mechanisms underlying disease pathogenesis and for the preclinical assessment of new therapies. In fact, existing mouse models have contributed significantly to our understanding of allergic/eosinophilic phenotypes of asthma and facilitated the development of novel targeted therapies (e.g. anti-IL-5 and anti-IgE). These therapies are effective in relevant subsets of severe asthma patients. Unfortunately, non-allergic/non-eosinophilic asthma, steroid resistance and disease exacerbation remain areas of unmet clinical need. No mouse model encompasses all features of severe asthma. However, mouse models can provide insight into pathogenic pathways that are relevant to severe asthma. In this review, as examples, we highlight models relevant to understanding steroid resistance, chronic tissue remodelling and disease exacerbation. Although these models highlight the complexity of the immune pathways that may underlie severe asthma, they also provide insight into new potential therapeutic approaches.

Prevalence of Respiratory Viral Infections in Korean Adult Asthmatics With Acute Exacerbations: Comparison With Those With Stable State

PURPOSE

Viral infections are involved in ~50% of exacerbations among Caucasian adult asthmatics. However, there have been few reports on the causative virus of exacerbations in Korean adult asthmatics. Thus, we compared frequencies and types of viruses between lower respiratory tract illnesses (LRTIs) with exacerbations (exacerbated LRTIs) and those without exacerbations (stable LRTIs) to evaluate contribution of respiratory viruses to exacerbations.

METHODS

Viral RNA was extracted from sputum using the Viral Gene-spin™ Kit. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to detect adenovirus (ADV), metapneumovirus (MPV), parainfluenza virus (PIV) 1/2/3, influenza virus (IFV) A, IFV B, respiratory syncytial virus (RSV) A/B, and rhinovirus (RV) A.

RESULTS

Among the 259 patients, 210 underwent a single sputum examination, and the remaining 49 underwent 2 to 4 sputum examinations. Virus was detected in 68 of the 259 exacerbated episodes and in 11 of the 64 stable episodes. Among the exacerbated episodes, RV was the most frequently detected virus, followed by influenza A, parainfluenza, RSV A/B, and ADV. Among the 11 stable episodes, RV was most frequently detected. Detection rates of these viruses did not differ between the 2 groups (P>0.05). Thirty-five patients underwent the virus examination at 2 episodes of exacerbation, while 14 patients underwent at each time of exacerbated and stable episodes. Virus detection rate at the second examination was significantly higher in cases with 2 exacerbation episodes than in those with initial exacerbation and sequential stable episodes (P=0.003). A seasonal pattern was noted in the detection rates of RV (September to December), IFV (January to April), PIV (May to September), and RSV A/B (September to April).

CONCLUSIONS

Respiratory viruses were identified in approximately 20% of LRTI irrespective of the presence of asthma exacerbation. RV and IFV A/B were most frequently detected. A group of patients experienced frequent viral infections followed by asthma exacerbations.

Pathogenesis of Viral Infection in Exacerbations of Airway Disease

Chronic airway diseases are a significant cause of morbidity and mortality worldwide, and their prevalence is predicted to increase in the future. Respiratory viruses are the most common cause of acute pulmonary infection, and there is clear evidence of their role in acute exacerbations of inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease. Studies have reported impaired host responses to virus infection in these diseases, and a better understanding of the mechanisms of these abnormal immune responses has the potential to lead to the development of novel therapeutic targets for virus-induced exacerbations. The aim of this article is to review the current knowledge regarding the role of viruses and immune modulation in acute exacerbations of chronic pulmonary diseases and to discuss exciting areas for future research and novel treatments.

The role of viral infections in exacerbations of chronic obstructive pulmonary disease and asthma

Asthma and chronic obstructive pulmonary disease (COPD) are major causes of global morbidity and mortality worldwide. The clinical course of both asthma and COPD are punctuated by the occurrence of exacerbations, acute events characterized by increased symptoms and airflow obstruction. Exacerbations contribute most of the morbidity, mortality and excess healthcare costs associated with both asthma and COPD. COPD and asthma exacerbations are frequently associated with respiratory virus infections and this has led to an intense research focus into the mechanisms of virus-induced exacerbations over the past decade. Current therapies are effective in reducing chronic symptoms but are less effective in preventing exacerbations, particularly in COPD. Understanding the mechanisms of virus-induced exacerbation will lead to the development of new targeted therapies that can reduce the burden of virus-induced exacerbations. In this review we discuss current knowledge of virus-induced exacerbations of asthma and COPD with a particular focus on mechanisms, human studies, virus-bacteria interactions and therapeutic advances.

Asthma in the older adult: presentation, considerations and clinical management

Asthma affects older adults to the same extent as children and adolescents. However, one is led to imagine that asthma prevalence decreases with aging and becomes a rare entity in the elderly. From a clinical perspective, this misconception has nontrivial consequences in that the recognition of the disease is delayed and the treatment postponed. The overall management of asthma in the elderly population is also complicated by specific features that the disease develops in the most advanced ages, and by the difficulties that the physician encounters when approaching the older asthmatic subjects. The current review article aims at describing the specific clinical presentations of asthma in the elderly and highlights the gaps and pitfalls in the diagnostic and therapeutic approaches. Relevant issues with regard to the clinical management of asthma in the elderly are also discussed.

Asthma in the elderly: what we know and what we have yet to know

In the past, asthma was considered mainly as a childhood disease. However, asthma is an important cause of morbidity and mortality in the elderly nowadays. In addition, the burden of asthma is more significant in the elderly than in their younger counterparts, particularly with regard to mortality, hospitalization, medical costs or health-related quality of life. Nevertheless, asthma in the elderly is still been underdiagnosed and undertreated. Therefore, it is an imperative task to recognize our current challenges and to set future directions. This project aims to review the current literature and identify unmet needs in the fields of research and practice for asthma in the elderly. This will enable us to find new research directions, propose new therapeutic strategies, and ultimately improve outcomes for elderly people with asthma. There are data to suggest that asthma in older adults is phenotypically different from young patients, with potential impact on the diagnosis, assessment and management in this population. The diagnosis of AIE in older populations relies on the same clinical findings and diagnostic tests used in younger populations, but the interpretation of the clinical data is more difficult. The challenge today is to encourage new research in AIE but to use the existing knowledge we have to make the diagnosis of AIE, educate the patient, develop a therapeutic approach to control the disease, and ultimately provide a better quality of life to our elderly patients.

A prospective study of respiratory viral infection in pregnant women with and without asthma

BACKGROUND

Respiratory viral infections are common in pregnancy, but their health impact, especially in asthma, is unknown. The objective of this study was to assess the frequency, severity, and consequences of respiratory viral infection during pregnancy in women with and without asthma.

METHODS

In this prospective cohort study, common cold symptoms were assessed during pregnancy in 168 women with asthma and 117 women without asthma using the common cold questionnaire and by self-report. Nasal and throat swabs were collected for suspected infections and tested by polymerase chain reaction for respiratory viruses. Pregnancy and asthma outcomes were recorded.

RESULTS

Pregnant women with asthma had more prospective self-reported and questionnaire-detected common colds than pregnant women without asthma (incidence rate ratio, 1.77; 95% CI, 1.30-2.42; P < .0001). Retrospectively reported common colds in early pregnancy and post partum were increased in women with asthma compared with women without asthma. The severity of cold symptoms was also increased in women with asthma (total cold score median, 8; interquartile range [5, 10] in women with asthma vs 6 [5, 8] in control subjects; P = .031). Among women with asthma, having a laboratory-confirmed viral infection was associated with poorer maternal health, with 60% of infections associated with uncontrolled asthma and a higher likelihood of preeclampsia.

CONCLUSIONS

Pregnant women with asthma have more common colds during pregnancy than pregnant women without asthma. Colds during pregnancy were associated with adverse maternal and pregnancy outcomes. Prevention of viral infection in pregnancy may improve the health of mothers with asthma.

Virus-induced exacerbations in asthma and COPD

Chronic obstructive pulmonary disease (COPD) is characterized by chronic airway inflammation and/or airflow limitation due to pulmonary emphysema. Chronic bronchitis, pulmonary emphysema, and bronchial asthma may all be associated with airflow limitation; therefore, exacerbation of asthma may be associated with the pathophysiology of COPD. Furthermore, recent studies have suggested that the exacerbation of asthma, namely virus-induced asthma, may be associated with a wide variety of respiratory viruses. COPD and asthma have different underlying pathophysiological processes and thus require individual therapies. Exacerbation of both COPD and asthma, which are basically defined and diagnosed by clinical symptoms, is associated with a rapid decline in lung function and increased mortality. Similar pathogens, including human rhinovirus, respiratory syncytial virus, influenza virus, parainfluenza virus, and coronavirus, are also frequently detected during exacerbation of asthma and/or COPD. Immune response to respiratory viral infections, which may be related to the severity of exacerbation in each disease, varies in patients with both COPD and asthma. In this regard, it is crucial to recognize and understand both the similarities and differences of clinical features in patients with COPD and/or asthma associated with respiratory viral infections, especially in the exacerbative stage. In relation to definition, epidemiology, and pathophysiology, this review aims to summarize current knowledge concerning exacerbation of both COPD and asthma by focusing on the clinical significance of associated respiratory virus infections.

Virus-induced exacerbations in asthma and COPD

Chronic obstructive pulmonary disease (COPD) is characterized by chronic airway inflammation and/or airflow limitation due to pulmonary emphysema. Chronic bronchitis, pulmonary emphysema, and bronchial asthma may all be associated with airflow limitation; therefore, exacerbation of asthma may be associated with the pathophysiology of COPD. Furthermore, recent studies have suggested that the exacerbation of asthma, namely virus-induced asthma, may be associated with a wide variety of respiratory viruses. COPD and asthma have different underlying pathophysiological processes and thus require individual therapies. Exacerbation of both COPD and asthma, which are basically defined and diagnosed by clinical symptoms, is associated with a rapid decline in lung function and increased mortality. Similar pathogens, including human rhinovirus, respiratory syncytial virus, influenza virus, parainfluenza virus, and coronavirus, are also frequently detected during exacerbation of asthma and/or COPD. Immune response to respiratory viral infections, which may be related to the severity of exacerbation in each disease, varies in patients with both COPD and asthma. In this regard, it is crucial to recognize and understand both the similarities and differences of clinical features in patients with COPD and/or asthma associated with respiratory viral infections, especially in the exacerbative stage. In relation to definition, epidemiology, and pathophysiology, this review aims to summarize current knowledge concerning exacerbation of both COPD and asthma by focusing on the clinical significance of associated respiratory virus infections.

Human parainfluenza type 3 virus impairs the efficacy of glucocorticoids to limit allergy-induced pulmonary inflammation in guinea-pigs

Viral exacerbations of allergen-induced pulmonary inflammation in pre-clinical models reportedly reduce the efficacy of glucocorticoids to limit pulmonary inflammation and airways hyper-responsiveness to inhaled spasmogens. However, exacerbations of airway obstruction induced by allergen challenge have not yet been studied. hPIV-3 (human parainfluenza type 3 virus) inoculation of guinea-pigs increased inflammatory cell counts in BAL (bronchoalveolar lavage) fluid and caused hyper-responsiveness to inhaled histamine. Both responses were abolished by treatment with either dexamethasone (20 mg/kg of body weight, subcutaneous, once a day) or fluticasone propionate (a 0.5 mg/ml solution aerosolized and inhaled over 15 min, twice a day). In ovalbumin-sensitized guinea-pigs, allergen (ovalbumin) challenge caused two phases of airway obstruction [measured as changes in sGaw (specific airways conductance) using whole body plethysmography]: an immediate phase lasting between 4 and 6 h and a late phase at about 7 h. The late phase, airway hyper-responsiveness to histamine and inflammatory cell counts in BAL were all significantly reduced by either glucocorticoid. Inoculation of guinea-pigs sensitized to ovalbumin with hPIV-3 transformed the allergen-induced airway obstruction from two transient phases into a single sustained response lasting up to 12 h. This exacerbated airway obstruction and airway hyper-responsiveness to histamine were unaffected by treatment with either glucocorticoid whereas inflammatory cell counts in BAL were only partially inhibited. Virus- or allergen-induced pulmonary inflammation, individually, are glucocorticoid-sensitive, but in combination generate a phenotype where glucocorticoid efficacy is impaired. This suggests that during respiratory virus infection, glucocorticoids might be less effective in limiting pulmonary inflammation associated with asthma.

An Approach to the Management of High Risk Asthmatic Patients

This review briefly outlines an approach to the management of high risk asthmatic patients. This approach involves: (i) identification of such high risk patients; (ii) investigation of precipitating factors contributing to severe attacks; and (iii) the introduction of a management strategy based on a simple system of self-assessment and self-treatment.

Association between episodes of upper respiratory infection and exacerbations in adult patients with asthma

BACKGROUND

Asthma has several phenotypical features, including recurrent exacerbations and recurrent episodes of upper respiratory infection (URI).

PURPOSE

A retrospective study was performed to identify the characteristics of adult patients with recurrent exacerbations of asthma, especially in association with recurrent episodes of URI.

METHODS

Information was collected using a self-administered questionnaire given to 7070 patients in autumn-winter 2006, 4859 patients in spring-summer 2007, and 4452 patients in autumn-winter 2007. The patients reported the degree of symptoms and the frequency of febrile episodes of URI and exacerbations. Severe exacerbations were defined as a self-report of asthma-related hospitalization, an emergency department visit, or a requirement for systemic corticosteroids. Recurrent febrile URI and exacerbations were defined as two or more episodes within the previous 6 months. A Poisson regression model was used to identify the factors that were predictors of a risk for exacerbations.

RESULTS

Of the 6266 patients who completed the questionnaire, the frequencies of febrile URI and episodes of severe exacerbations were 1.54 and 0.54 per subject per year, respectively. Logistic regression analysis showed that an older age [odds ratio (OR): 1.57; 95% confidence interval (CI): 1.15-2.13], female sex (OR: 1.58; 95% CI: 1.20-2.08), recurrent febrile episodes of URI (OR: 2.68; 95% CI: 1.47-4.91), a history of previous exacerbation within 1 year (OR: 1.74; 95% CI: 1.28-2.34), disuse of inhaled corticosteroids (ICSs) (OR: 2.63; 95% CI: 1.68-4.12), and disuse of add-on leukotriene receptor antagonists (LTRAs) (OR: 1.42; 95% CI: 1.06-1.74) were independently associated with moderate to severe symptom-severity. Poisson regression analysis showed that the independent factors that contributed to the frequency of recurrent severe exacerbations were female sex (regression coefficient β = 0.62, p < .01), an episode of sputum with coughing (β = 1.23, p < .01), nocturnal awakening (β = 1.22, p < .01), and severe exacerbation (β = 0.78, p < .01) within the previous 6 months.

CONCLUSION

Symptom-severity of asthma and the frequency of severe exacerbations were associated with previous exacerbations and susceptibility to URI.

IL-13 suppresses double-stranded RNA-induced IFN-λ production in lung cells

Acute asthma exacerbations are frequently associated with respiratory viral infections. Although impaired production of type III IFNs (IFN-λs) is related to the severity of asthma exacerbation, the mechanisms underlying deficient IFN-λ production in asthma are poorly understood. Airway epithelial cells were stimulated in vitro with a synthetic mimetic of viral double-stranded RNA (dsRNA). IL-13, a crucial cytokine responsible for asthma pathogenesis, suppressed dsRNA-induced expression of IFN-λs, and JAK inhibitor AG490 prevented the suppression by IL-13. IL-13 per se did not affect IFN-λ production or the expressions of membrane dsRNA receptor TLR3 and of cytoplasmic receptors RIG-I and MDA5. IL-13-deficient mice exhibited more enhanced IFN-λ expression after intratracheal instillation of dsRNA than wild-type mice, whereas IFN-λ expression after dsRNA was absent in the mouse lungs of the OVA-induced asthma model. These findings suggest that IL-13 may be a putative cytokine suppressing IFN-λ production against airway viral infections in asthmatics.

Coevolution of TH1, TH2, and TH17 responses during repeated pulmonary exposure to Aspergillus fumigatus conidia

Aspergillus fumigatus, a ubiquitous airborne fungus, can cause invasive infection in immunocompromised individuals but also triggers allergic bronchopulmonary aspergillosis in a subset of otherwise healthy individuals repeatedly exposed to the organism. This study addresses a critical gap in our understanding of the immunoregulation in response to repeated exposure to A. fumigatus conidia. C57BL/6 mice were challenged intranasally with A. fumigatus conidia weekly, and leukocyte composition, activation, and cytokine production were examined after two, four, and eight challenges. Approximately 99% of A. fumigatus conidia were cleared within 24 h after inoculation, and repeated exposure to A. fumigatus conidia did not result in hyphal growth or accumulation of conidia with time. After 2 challenges, there was an early influx of neutrophils and regulatory T (T(reg)) cells into the lungs but minimal inflammation. Repeated exposure promoted sustained expansion of the draining lymph nodes, while the influx of eosinophils and other myeloid cells into the lungs peaked after four exposures and then decreased despite continued A. fumigatus challenges. Goblet cell metaplasia and low-level fibrosis were evident during the response. Repeated exposure to A. fumigatus conidia induced T cell activation in the lungs and the codevelopment by four exposures of T(H)1, T(H)2, and T(H)17 responses in the lungs, which were maintained through eight exposures. Changes in CD4 T cell polarization or T(reg) numbers did not account for the reduction in myeloid cell numbers later in the response, suggesting a non-T-cell regulatory pathway involved in dampening inflammation during repeated exposure to A. fumigatus conidia.

The infectious march: the complex interaction between microbes and the immune system in asthma

There has been significant progress in our knowledge about the relationship between infectious disease and the immune system in relation to asthma, but many unanswered questions still remain. Respiratory tract infections such as those caused by respiratory syncytial virus and rhinovirus during the first 2 years of life are still clearly associated with later wheezing and asthma, but the mechanism has not been completely worked out. Is there an "infectious march" triggered by infection in infancy that progresses to disease pathology or are infants who contract respiratory infections predisposed to developing asthma? This review focuses on the common themes in the interaction between microbes and the immune system, and presents a critical appraisal of the evidence to date. The various mechanisms whereby microbes alter the immune response and how this might influence asthma are discussed along with new and promising clinical practices for prevention and therapy. Recent advances in using sensitive polymerase chain reaction detection methods have allowed more rigorous testing of the causality hypothesis of virus infection leading to asthma, but the evidence is still equivocal. Various exceptions and inconsistencies in the clinical trials are discussed in light of new guidelines for subject inclusion/exclusion in hopes of providing some standardization. Despite past failures in vaccination and disappointing results of some clinical trials, the new strategies for prophylaxis including RNA interference and targeted delivery of microbicides offer a large dose of hope to a world suffering from an increasing incidence of asthma as well as a huge burden of health care cost and loss of quality of life.

Respiratory syncytial virus infections in the adult asthmatic--mechanisms of host susceptibility and viral subversion

Respiratory syncytial virus (RSV), a single-stranded RNA virus of the Paramyxoviridae family, is a major cause of bronchiolitis in infants and is also conjectured to be an early-life influence on the development of asthma. Although the data supporting a role for RSV in bronchiolitis in children are robust and evidence to support its role in juvenile asthmatics exists, RSV's role in asthma pathogenesis in adults is not as clearly defined. The authors review the literature to further elucidate RSV's impact on adult asthmatics, including its importance as a cause of asthma exacerbations. They examine the morbidity associated with RSV infection and how the immune response may differ between adult asthmatics and nonasthmatics. They review the responses by specific cell types from adults with asthma that are stimulated by RSV. They also consider the role of early-life exposure to RSV and its contribution to asthma in adults. Lastly, they review the mechanisms by which RSV evades normal host immune responses and subverts these responses to its benefit.

Adult asthma exacerbations and environmental triggers: a retrospective review of ED visits using an electronic medical record

BACKGROUND

Despite familiarity with triggers for asthma, there is little recent study on the association of triggers with the emergency department (ED) presentation of adult asthma exacerbation.

METHODS

Retrospective electronic chart review of adult patients treated in an urban teaching hospital ED with chief complaint and diagnostic coding related to asthma and upper respiratory tract infection (URI) was conducted. Monthly aeroallergen data and environmental conditions were obtained from a local allergen extract laboratory and local government sources. Data analysis was performed using Newey-West time series regression modeling with adjustment for autocorrelation or ordinary least squares linear regression modeling using outcome variables of asthma visits and admissions.

RESULTS

There were 56, 747 visits, with 554 asthma visits and 1,514 URI visits. Asthma visits (R(2) = 0.631) were positively correlated with tree pollen counts (correlation coefficient = 0.458 [0.152-0.765]) and average humidity (correlation coefficient = 1.528 [0.296-2.760]). Asthma admissions (R(2) = 0.480) were negatively correlated with average temperature (correlation coefficient = -0.557 [-1.052 to -0.061]) when adjusting for confounding by fine particulate matter.

CONCLUSIONS

The ED acute asthma exacerbation presentation is positively correlated with tree pollen and humidity, whereas need for admission is associated with dropping temperatures. These results reinforce the need for vigilance during periods of increased risk and perhaps focused preventative strategies.

Effect of BSA antigen sensitization during the acute phase of influenza A viral infection on CD11c+ pulmonary antigen presenting cells

BACKGROUND

Influenza A viral infection is concerned with induction of asthma. CD11c+ pulmonary antigen presenting cells (APCs) play a central role in sensitization with inhaled antigens during the acute phase of influenza A viral infection and also reside on bronchial epithelium for the long term after sensitization. To investigate the role of CD11c+ pulmonary APCs in the inhaled antigen sensitization during the acute phase of influenza A viral infection, we analyzed their function.

METHODS

Mice were infected with influenza A virus and were sensitized intranasally with BSA/alum during the acute phase of influenza A viral infection. Expression of surface antigens on CD11c+ pulmonary APCs was analyzed by FACS. Cytokine production from CD11c+ pulmonary APCs, and interaction between CD11c+ pulmonary APCs and naïve CD4+ T cells was assessed by ELISA. Ability of antigen presentation by CD11c+ pulmonary APCs was measured by proliferation assay.

RESULTS

BSA antigen sensitization during the acute phase of influenza A viral infection induced eosinophil recruitment into the lungs after BSA antigen challenge and moderately increased expression of MHC class II molecules on CD11c+ pulmonary APCs. The interaction between the CD11c+ pulmonary APCs and naïve CD4+ T cells secreted large amounts of IL-10.

CONCLUSIONS

BSA antigen sensitization during the acute phase of influenza A viral infection enhanced IL-10 production from naïve CD4+ T cell interaction with CD11c+ pulmonary APCs. The IL-10 secretion evoked Th2 responses in the lungs with downregulation of Th1 responses and was important for the eosinophil recruitment into the lungs after BSA antigen challenge.

Modern approaches to understanding stress and disease susceptibility: A review with special emphasis on respiratory disease

Studies in animals and humans link both physical and psychological stress with an increased incidence and severity of respiratory infections. For this manuscript we define stress as the physiological responses an individual undergoes while adjusting to a continually changing environment. It is known that stressors of various types (psychological/physical) can alter the physiological levels of certain hormones, chemokines and cytokines. These alterations send information to the central nervous system to take necessary action which then sends messages to appropriate organs/tissues/cells to respond. These messages can either activate or suppress the immune system as needed and failure to compensate for this by the body can lead to serious health-related problems. Little is known how stress affects disease susceptibility, yet understanding this mechanism is important for developing effective treatments, and for improving health and food quality. The current review focuses on (a) the effects of psychological stressors in humans and animals, (b) various methodologies employed to understand stress responses and their outcomes, and (c) the current status of the attempts to correlate stress and disease with respiratory disease as model system. The methodologies included in this review span traditional epidemiological, behavioral and immunological studies to current high throughput genomic, proteomic, metabolomic/metabonomic approaches. With the advent of various newer omics and bioinformatics methodologies we postulate that it will become feasible to understand the mechanisms through which stress can influence disease onset. Although the literature in this area is limited because of the infancy of this research area, the objective of this review is to illustrate the power of new approaches to address complex biological questions. These new approaches will also aid in our understanding how these processes are related to the dynamics and kinetics of changes in expression of multiple genes at various levels.

Regulation of TLR2 expression and function in human airway epithelial cells

Toll-like receptor (TLR1-6) mRNAs are expressed in normal human bronchial epithelial cells with higher basal levels of TLR3. TLR2 mRNA and plasma membrane protein expression was enhanced by pretreatment with Poly IC, a synthetic double-stranded RNA (dsRNA) known to activate TLR3. Poly IC also enhanced mRNA expression of adaptor molecules (MyD88 and TIRAP) and coreceptors (Dectin-1 and CD14) involved in TLR2 signaling. Additionally, mRNA expression of TLR3 and dsRNA-sensing proteins MDA5 and RIG-I increased following Poly IC treatment. In contrast, basal mRNA expression of TLR5 and TLR2 coreceptor CD36 was reduced by 77% and 62%, respectively. ELISA of apical and basolateral solutions from Poly IC-stimulated monolayers revealed significantly higher levels of IL-6 and GM-CSF compared with the TLR2 ligand PAM(3)CSK(4). Pretreatment with anti-TLR2 blocking antibody inhibited the PAM(3)CSK(4)-induced increase in IL-6 secretion after Poly IC exposure. An increase in IL-6 secretion was also observed in cells stimulated with Alternaria extract after pretreatment with Poly IC. However, IL-6 secretion was not stimulated by zymosan or lipothechoic acid (LTA). These data demonstrated that upregulation of TLR2 following exposure to dsRNA enhances functional responses of the airway epithelium to certain (PAM(3)CSK(4)), but not all (zymosan, LTA) TLR2 ligands and that this is likely due to differences in coreceptor expression.

Infections

This chapter reviews the epidemiological evidence implicating infectious pathogens as triggers and will discuss the mechanisms of interaction between the host–pathogen response and preexisting airway pathology that result in an exacerbation. Asthma is a multifaceted syndrome involving atopy, bronchial hyperreactivity, and IgE and non-IgE-mediated acute and chronic immune responses. The asthmatic airway is characterized by an infiltrate of eosinophils and of T-lymphocytes expressing the type 2 cytokines IL-4, IL-5, and IL-13. Trigger factors associated with acute exacerbations of asthma include exposure to environmental allergens, especially animals, molds, pollens and mites, cold, exercise, and drugs. The frequency of exacerbations is a major factor in the quality of life of patients with COPD. The typical clinical features of an exacerbation include increased dyspnea, wheezing, cough, sputum production, and worsened gas exchange. Although noninfectious causes of exacerbations such as allergy, air pollution, or inhaled irritants including cigarette smoke may be important, acute airway infections are the major precipitants. The infection and consequent host inflammatory response result in increased airway obstruction. The success of vaccination to prevent respiratory virus infections has been limited by significant variation within the major virus types causing disease. Currently much of the treatment of infective exacerbations of asthma and COPD is symptomatic, consisting of increased bronchodilators, either short-acting β 2—agonists in inhaled or intravenous form or anticholinergics or theophyllines, or supportive in the form of oxygen and in severe cases noninvasive or invasive ventilatory measures.

Predicting worsening asthma control following the common cold

The asthmatic response to the common cold is highly variable, and early characteristics that predict worsening of asthma control following a cold have not been identified. In this prospective multicentric cohort study of 413 adult subjects with asthma, the mini-Asthma Control Questionnaire (mini-ACQ) was used to quantify changes in asthma control and the Wisconsin Upper Respiratory Symptom Survey-21 (WURSS-21) to measure cold severity. Univariate and multivariable models were used to examine demographic, physiological, serological and cold-related characteristics for their relationship to changes in asthma control following a cold. Clinically significant worsening of asthma control was observed following a cold (mean+/-SD increase in mini-ACQ score of 0.69+/-0.93). Univariate analysis demonstrated that season, centre location, cold duration and cold severity measurements were all associated with a change in asthma control. Multivariable analysis of the covariates available within the first 2 days of cold onset revealed that the day 2 and cumulative sum of day 1 and 2 WURSS-21 scores were significant predictors of the subsequent changes in asthma control. In asthmatic subjects, cold severity within the first 2 days can be used to predict subsequent changes in asthma control. This information may help clinicians prevent deterioration in asthma control following a cold.

Prevalence of viral respiratory tract infections in children with asthma

Background

Previous studies support a strong association between viral respiratory tract infections and asthma exacerbations. The effect of newly discovered viruses on asthma control is less well defined.

Objective

We sought to determine the contribution of respiratory viruses to asthma exacerbations in children with a panel of PCR assays for common and newly discovered respiratory viruses.

Methods

Respiratory specimens from children aged 2 to 17 years with asthma exacerbations (case patients, n = 65) and with well-controlled asthma (control subjects, n = 77), frequency matched by age and season of enrollment, were tested for rhinoviruses, enteroviruses, respiratory syncytial virus, human metapneumovirus, coronaviruses 229E and OC43, parainfluenza viruses 1 to 3, influenza viruses, adenoviruses, and human bocavirus.

Results

Infection with respiratory viruses was associated with asthma exacerbations (63.1% in case patients vs 23.4% in control subjects; odds ratio, 5.6; 95% CI, 2.7- 11.6). Rhinovirus was by far the most prevalent virus (60% among case patients vs 18.2% among control subjects) and the only virus significantly associated with exacerbations (odds ratio, 6.8; 95% CI, 3.2-14.5). However, in children without clinically manifested viral respiratory tract illness, the prevalence of rhinovirus infection was similar in case patients (29.2%) versus control subjects (23.4%, P > .05). Other viruses detected included human metapneumovirus (4.6% in patients with acute asthma vs 2.6% in control subjects), enteroviruses (4.6% vs 0%), coronavirus 229E (0% vs 1.3%), and respiratory syncytial virus (1.5% vs 0%).

Conclusion

Symptomatic rhinovirus infections are an important contributor to asthma exacerbations in children.

Clinical implications

These results support the need for therapies effective against rhinovirus as a means to decrease asthma exacerbations.

How viral infections cause exacerbation of airway diseases

Exacerbations of asthma and COPD are major causes of morbidity, mortality, and health-care costs. Over the last decade, studies using new molecular diagnostic techniques have established that respiratory viruses are a major cause of exacerbations of both asthma and COPD. The most prevalent viruses detected during exacerbations are the rhinoviruses. Despite the burden of disease associated with exacerbations, little is known about the mechanisms of virus-induced exacerbations of airway diseases. Exacerbations are associated with increased airway inflammation in patients with both asthma and COPD, but many questions remain unanswered regarding the key inflammatory cells and mediators involved. Identifying the key inflammatory mediators involved in exacerbations holds the promise of developing diagnostic and prognostic markers of exacerbation. In addition, such studies can identify new therapeutic targets for the development of novel drugs for the prevention and treatment of exacerbations.

The relationship of rhinovirus-associated asthma hospitalizations with inhaled corticosteroids and smoking

BackgroundAlthough rhinovirus (RV) respiratory infections trigger asthma exacerbations, the etiologic association between this virus and severe exacerbations, as well as the clinical characteristics of adults at risk for RV-associated asthma that necessitates hospitalization, have not been established

MethodsDuring 1999–2003, we conducted a cohort study of 101 adults prospectively enrolled at hospital admission for an asthma exacerbation. Patient characteristics and frequencies of RV in nasal specimens were analyzed, by reverse-transcription polymerase chain reaction (RT-PCR), at asthma-related hospital admission and at a 3-month convalescent follow-up visit

ResultsRV was detected by RT-PCR in 21% of hospitalized patients over a 4-year period and in 1.3% of patients who returned for a 3-month follow-up visit. RV detection was strongly associated with hospitalization for asthma (adjusted odds ratio [OR], 15.1 [95% confidence interval {CI}, 1.88–121.4]). After adjustment for baseline asthma severity, RV-positive patients were more likely than RV-negative patients to be current smokers and nonusers of inhaled corticosteroids (ICSs) (adjusted OR, 11.18 [95% CI, 2.37–52.81]; P=.002)

ConclusionsRV respiratory infection is an etiologic agent in severe asthma exacerbations necessitating hospitalization in adults. Compared with hospitalized patients with asthma who were RV negative, RV-positive patients were significantly more likely to be smokers and nonusers of ICSs

Study of modifiable risk factors for asthma exacerbations: virus infection and allergen exposure increase the risk of asthma hospital admissions in children

BACKGROUND

Asthma exacerbation is the most common cause of hospital admission in children. A study was undertaken to investigate the importance of allergen exposure in sensitised individuals in combination with viral infections and other potentially modifiable risk factors precipitating asthma hospital admission in children.

METHODS

Eighty four children aged 3-17 years admitted to hospital over a 1 year period with an acute asthma exacerbation (AA) were matched for age and sex with two control groups: stable asthmatics (SA) and children admitted to hospital with non-respiratory conditions (IC). Risk factors were assessed by questionnaires and determination of allergen sensitisation, home allergen exposure, pollen exposure, and respiratory virus infection.

RESULTS

Several non-modifiable factors (atopy, duration of asthma) were associated with increased risk. Among the modifiable factors, pet ownership, housing characteristics, and parental smoking did not differ between the groups. Regular inhaled corticosteroid treatment was significantly less common in the AA group than in the SA group (OR 0.2, 95% CI 0.1 to 0.6; p = 0.002). A significantly higher proportion of the AA group were virus infected (44%) and sensitised and highly exposed to sensitising allergen (76%) compared with the SA (18% and 48%) and IC groups (17% and 28%; both p<0.001). In a multiple conditional logistic regression (AA v SA), allergen sensitisation and exposure or virus detection alone were no longer independently associated with hospital admission. However, the combination of virus detection and sensitisation with high allergen exposure substantially increased the risk of admission to hospital (OR 19.4, 95% CI 3.7 to 101.5, p<0.001).

CONCLUSIONS

Natural virus infection and real life allergen exposure in allergic asthmatic children increase the risk of hospital admission. Strategies for preventing exacerbations will need to address these factors.

How appropriate is asthma therapy in general practice?

High association between burden of asthma and inadequate disease control make asthma management a major public health issue. We studied asthma management practices of general practitioners (GPs) in France to describe drug therapy and more specifically, to identify correlates of antibiotic prescriptions, a marker of inappropriate asthma management. Patients with persistent asthma aged 17-50 years were evaluated in a 12-month retrospective study using a computerized GPs database (Thales) and a patient survey, in which patients reported hospital contacts, use of oral corticosteroids and recent asthma symptoms. Therapy was described and the correlates of antibiotic prescriptions in the previous year were identified using multivariate logistic regression. During the study period, 16.4% of 1038 patients received one or more prescriptions of theophylline, 31.3% long-acting beta-agonists and 61.6% inhaled corticosteroids. Rates of prescription of antibiotics, expectorants, antihistamines, antitussives and nasal corticosteroids were 57.6, 42.0, 33.0, 19.9, and 14.4%, respectively. In parallel, 15% of patients reported at least one hospital contact for asthma and 43.1% used oral corticosteroids. Antibiotic prescriptions were more likely co-prescribed in patients using expectorants [odds ratio (OR) = 13.0, 95% confidence interval (CI) = 8.5-19.8] and antitussives (OR = 6.5, 95% CI = 3.7-11.6). Moreover, patients using courses of oral corticosteroids, and often visiting their GP (more than four times) during the study period were more likely to receive antibiotics. The results were unchanged when analyses were restricted to non-smokers and younger patients (< or = 40 years). Asthma management was sub-optimal among asthma patients treated by general practitioners in France. Antibiotics, expectorants, antihistamines, antitussives and nasal corticosteroids were commonly prescribed while asthma controllers were under-used.

Modulation of protective immunity, eosinophilia, and cytokine responses by selective mutagenesis of a recombinant G protein vaccine against respiratory syncytial virus

Using an Escherichia coli-grown plasmid vector encoding a fragment of thioredoxin (Trx) fused to a central region (amino acids 128 to 229) of the respiratory syncytial virus (RSV) (Long strain) G protein, we employed site-directed mutagenesis to investigate the importance of selected amino acids to vaccine efficacy. Mice were immunized with a total of 10 wild-type or mutant Trx-G proteins and challenged intranasally with RSV. Striking differences in the induction of RSV G-protein-specific antibodies, protection against RSV challenge, cytokine RNA responses, and induction of RSV-associated eosinophilic inflammation were observed among the mutant proteins examined. Taken together, the results identify a critical role for specific amino acids in the induction of protective immunity and priming for eosinophilia against RSV.

The Totton-Ken Seibu earthquake and exacerbation of asthma in adults

The aim of the study was to characterize patients at risk for exacerbations of their asthma as a result of the Tottori-Ken Seibu earthquake and to identify factors that predict exacerbation of asthma after an earthquake. A retrospective cohort study-analysis was conducted of 156 asthmatic patients, aged 18 to 89 years, who were out-patients of Tottori University Hospital and who had completely recorded their asthmatic symptoms and measured their peak expiratory flow (PEF) rates for more than one year prior to the earthquake. Seventeen (11%) patients who experienced the earthquake were identified as having an exacerbation within one month after the earthquake. Diurnal variability of PEF during the month after the earthquake was compared to values during a matched month one year previously. When factors associated with exacerbation were identified by a review of the medical case notes and the contribution of these factors to the exacerbation was determined using multivariate analysis, airflow limitation was shown to be independently associated with exacerbation after the earthquake. Acute asthma attacks are more likely to occur within the first week after the earthquake event without diurnal PEF variability. Asthma is likely to worsen after an earthquake.

Infectious triggers of asthma

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

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Bystander suppression of allergic airway inflammation by lung resident memory CD8+ T cells

CD8+ memory T cells have recently been recognized as playing a key role in natural immunity against unrelated viral infections, a phenomenon referred to as "heterologous antiviral immunity." We now provide data that the cellular immunological interactions that underlie such heterologous immunity can play an equally important role in regulating T helper 2 immune responses and protecting mucosal surfaces from allergen-induced inflammation. Our data show that CD8+ T cells, either retained in the lung after infection with influenza virus, or adoptively transferred via the intranasal route can suppress allergic airway inflammation. The suppression is mediated by IFN-gamma, which acts to reduce the activation level, T helper 2 cytokine production, airways hyperresponsiveness, and migration of allergen-specific CD4+ T cells into the lung, whereas the systemic and draining lymph node responses remain unchanged. Of note, adoptive transfer of previously activated transgenic CD8+ T cells conferred protection against allergic airway inflammation, even in the absence of specific-antigen. Airway resident CD8+ T cells produced IFN-gamma when directly exposed to conditioned media from activated dendritic cells or the proinflammatory cytokines IL-12 and IL-18. Taken together these data indicate that effector/memory CD8+ T cells present in the airways produce IFN-gamma after inflammatory stimuli, independent of specific-antigen, and as a consequence play a key role in modifying the degree and frequency of allergic responses in the lung.

Severe asthma

Severe asthma is a term that is commonly used to describe patients with refractory, brittle, near fatal, and difficult-to-control asthma. Patients with severe asthma typically experience persistent symptoms despite medical therapy, report decreased quality of life and suffer an accelerated loss of lung function. The role of genetics, environmental exposure, and infection in the development of more severe asthma is the focus of ongoing research. While pathologic changes in these patients are now believed to involve lung parenchyma, in addition to large and small airways, the independent contribution of each of these compartments to the severe asthma phenotype is not well defined. The clinical evaluation of severe asthma patients should include investigating conditions commonly associated with severe asthma, such as gastroesophageal reflux disease, vocal cord dysfunction, and rhinosinusitis. In addition, advanced imaging techniques, measurement of exhaled gas or sputum indices, and airway biopsy are tools that may aid in evaluating severe asthma patients in the near future. Management of patients with severe asthma requires a comprehensive approach that includes non-pharmacological and pharmacological measures. Combination antiinflammatory and long-acting bronchodilator therapy remains the mainstay of management.

Temporal dynamics of emergency department and hospital admissions of pediatric asthmatics

Asthma is a chronic disease that can result in exacerbations leading to urgent care in emergency departments (EDs) and hospitals. We examined seasonal and temporal trends in pediatric asthma ED (1997-1999) and hospital (1986-1999) admission data so as to identify periods of increased risk of urgent care by age group, gender, and race. All pediatric ED and hospital admission data for Maryland residents occurring within the state of Maryland were evaluated. Distinct peaks in pediatric ED and hospital asthma admissions occurred each year during the winter-spring and autumn seasons. Although the number and timing of these peaks were consistent across age and racial groups, the magnitude of the peaks differed by age and race. The same number, timing, and relative magnitude of the major peaks in asthma admissions occurred statewide, implying that the variables affecting these seasonal patterns of acute asthma exacerbations occur statewide. Similar gross seasonal trends are observed worldwide. Although several environmental, infectious, and psychosocial factors have been linked with increases in asthma exacerbations among children, thus far they have not explained these seasonal patterns of admissions. The striking temporal patterns of pediatric asthma admissions within Maryland, as described here, provide valuable information in the search for causes.

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

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

CD8+ T cells and immunoregulatory networks in asthma

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

A single amino acid substitution in a recombinant G protein vaccine drastically curtails protective immunity against respiratory syncytial virus (RSV)

Recent studies have indicated a dominant T cell epitope located approximately between amino acids 184 and 203 on the respiratory syncytial virus (RSV) G protein. Using an Escherichia coli-grown plasmid vector encoding a fragment of thioredoxin (Trx) fused to a central region (amino acids 128-229) of the RSV G protein, we employed site-directed mutagenesis to investigate the importance of selected amino acids on vaccine efficacy. By changing two amino acids Arg 188 and Lys 192 to alanine, the ability of the Trx-G 128-229 fusion protein to protect mice against RSV challenge was virtually abolished. Mice immunized with the double mutant protein showed low levels of neutralizing antibodies and no pulmonary eosinophilic infiltrate, in contrast to that observed in mice immunized with wild type protein prior to RSV challenge. While less effective than the double mutant, mutation of either Arg 188 or Lys 192 to Ala drastically impaired the ability of immunized Trx-G 128-229 to induce neutralizing antibodies and to elicit pulmonary eosinophilia associated with RSV challenge. Despite low levels of virus-neutralizing antibodies, G protein-specific antibodies were detected by Western blotting in the sera from mice immunized with either of the single mutants (Arg 188 or Lys 192) but not the double mutant. Finally, immunization of mice with truncated forms of the Trx-G protein, showed partial protection against RSV challenge with Trx-G 128-188 but not with Trx-G 189-229. Taken together, the results indicate an important role for Arg 188 and Lys 192 in the induction of protective immunity and priming for eosinophilia against RSV. Furthermore, while the dominant protective linear epitope on the RSV G protein requires an intact sequence around Arg 188, there are additional, but less potent, protective epitopes upstream of Arg 188.

Conventional influenza vaccination is not associated with complications in working-age patients with asthma or chronic obstructive pulmonary disease

By using a nested case-control design, the authors studied the effectiveness of the influenza vaccine in reducing severe and fatal complications in 4,241 and 5,966 primary care, working-age patients aged 18-64 years who had asthma or chronic obstructive pulmonary disease during the 1998-1999 and 1999-2000 influenza epidemics in the Netherlands. Patients developing fatal or nonfatal exacerbations of lung disease, pneumonia, congestive heart failure, or myocardial infarction during either epidemic were considered cases. For each case, four age- and sex-matched controls were randomly sampled, and patient records were reviewed. Conditional logistic regression and propensity scores were used to assess vaccine effectiveness after adjustment for confounding factors. In seasons one and two, respectively, 87% (47/54) and 85% (171/202) of the cases and 74% (155/210) and 75% (575/766) of the controls had been vaccinated. After adjustments, vaccination was not associated with reductions in complications (season one: odds ratio = 0.95, 95% confidence interval (CI): 0.26, 3.48; season two: odds ratio = 1.07, 95% CI: 0.59, 1.96; pooled odds ratio = 1.07, 95% CI: 0.63, 1.80). Because influenza vaccination appeared not to be associated with a clinically relevant reduction in severe morbidity, other measures need to be explored.

Design of the Dutch prevention of influenza, surveillance and management (PRISMA) study

Rationale and design of a study on the cost-effectiveness of the Dutch influenza vaccination campaign are described. During two influenza epidemics, about 75,000 primary care patients recommended for influenza vaccination are included. Cases have fatal or non-fatal influenza, pneumonia, otitis media, acute respiratory disease (ARD), heart failure, myocardial infarction, depression or diabetes dysregulation. Per case four controls are sampled, frequency matched on age and high-risk co-morbidity (<18 years, 18-64, >/=65 healthy, >/=65 with co-morbidity). Baseline and outcome data are retrieved from patient records. During the 1999-2000 influenza A epidemic 5891 (7.9%) high-risk children, 24,848 (33.2%) high-risk adults aged 18-64 years, 18,484 (24.7%) elderly with co-morbidity and 25,527 (34.1%) healthy elderly had been included. The mortality rate was 5.2 per 1000 and 2035 non-fatal outcome events were recorded (incidence rate 27.2/1000).

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.