Wheezing, asthma, and pulmonary dysfunction 10 years after infection with respiratory syncytial virus in infancy

Effects of COVID-19 pandemic-associated reduction in respiratory infections on infantile asthma development

Background

It is speculated that the coronavirus disease 2019 (COVID-19) pandemic-associated reduction in the prevalence of respiratory tract infections has influenced the incidence of asthma in young children.

Objectives

We investigated an association between the reduction in viral infections and the reduction in asthma in young children.

Methods

The subjects were infants born in the early stages of the COVID-19 pandemic in Japan, which began in February 2020. A questionnaire survey related to asthma and allergy was conducted at 18 months and 3 years of age. These results were compared to those of age-matched infants during the nonpandemic period.

Results

There were no epidemics of viral infectious diseases until the target child was 18 months old. At 18 months, the incidence of asthma/asthmatic bronchitis diagnosed by physicians in pandemic children was significantly lower than that in nonpandemic children. In 3-year-olds, no marked difference was observed between nonpandemic infants and pandemic children, except for an increase in respiratory syncytial virus infection in pandemic children. In a comparative study of the same children at ages 18 months and 3 years, an increased prevalence of asthma/asthmatic bronchitis was observed in pandemic children. Furthermore, the incidence of asthma after respiratory syncytial virus infection in pandemic infants was significantly lower than that in nonpandemic children.

Conclusion

The COVID-19 pandemic-associated reduction in respiratory tract infections may have reduced the incidence of asthma in early childhood, and respiratory syncytial virus infection after 18 months of age had little effect on the onset of asthma. These results indicate the importance of preventing respiratory tract infections in early infancy.

Approaches to the Prevention and Treatment of Respiratory Syncytial Virus Infection in Children: Rationale and Progress to Date

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection (LRTI) in children, and is associated with long-term pulmonary sequelae for up to 30 years after infection. The mainstay of RSV management is supportive therapy such as supplemental oxygen. Palivizumab (Synagis™-AstraZeneca), a monoclonal antibody targeting the RSV F protein site II, has been licensed for the prevention of RSV in high-risk groups since 1998. There has been recent promising progress in preventative strategies that include vaccines and long-acting, high-potency monoclonal antibodies. Nirsevimab (Beyfortus™-AstraZeneca/Sanofi), a monoclonal antibody with an extended half-life, has recently been registered in the European Union and granted licensure by the US Food and Drug Administration. Furthermore, a pre-fusion sub-unit protein vaccine has been granted licensure for pregnant women, aimed at protecting their young infants, following established safety and efficacy in clinical trials (Abrysvo™-Pfizer). Also, multiple novel antiviral therapeutic options are in early phase clinical trials. The next few years have the potential to change the landscape of LRTI through improvements in the prevention and management of RSV LRTI. Here, we discuss these new approaches, current research, and clinical trials in novel therapeutics, monoclonal antibodies, and vaccines against RSV infection in infants and children.

Health effects associated with exposure to secondhand smoke: a Burden of Proof study

Despite a gradual decline in smoking rates over time, exposure to secondhand smoke (SHS) continues to cause harm to nonsmokers, who are disproportionately children and women living in low- and middle-income countries. We comprehensively reviewed the literature published by July 2022 concerning the adverse impacts of SHS exposure on nine health outcomes. Following, we quantified each exposure-response association accounting for various sources of uncertainty and evaluated the strength of the evidence supporting our analyses using the Burden of Proof Risk Function methodology. We found all nine health outcomes to be associated with SHS exposure. We conservatively estimated that SHS increases the risk of ischemic heart disease, stroke, type 2 diabetes and lung cancer by at least around 8%, 5%, 1% and 1%, respectively, with the evidence supporting these harmful associations rated as weak (two stars). The evidence supporting the harmful associations between SHS and otitis media, asthma, lower respiratory infections, breast cancer and chronic obstructive pulmonary disease was weaker (one star). Despite the weak underlying evidence for these associations, our results reinforce the harmful effects of SHS on health and the need to prioritize advancing efforts to reduce active and passive smoking through a combination of public health policies and education initiatives.

Epidemiology and Immunopathogenesis of Virus Associated Asthma Exacerbations

Asthma is a common airway disease, affecting millions of people worldwide. Although most asthma patients experience mild symptoms, it is characterized by variable airflow limitation, which can occasionally become life threatening in the case of a severe exacerbation. The commonest triggers of asthma exacerbations in both children and adults are viral infections. In this review article, we will try to investigate the most common viruses triggering asthma exacerbations and their role in asthma immunopathogenesis, since viral infections in young adults are thought to trigger the development of asthma either right away after the infection or at a later stage of their life. The commonest viral pathogens associated with asthma include the respiratory syncytial virus, rhinoviruses, influenza and parainfluenza virus, metapneumovirus and coronaviruses. All these viruses exploit different molecular pathways to infiltrate the host. Asthmatics are more prone to severe viral infections due to their unique inflammatory response, which is mostly characterized by T2 cytokines. Unlike the normal T1 high response to viral infection, asthmatics with T2 high inflammation are less potent in containing a viral infection. Inhaled and/or systematic corticosteroids and bronchodilators remain the cornerstone of asthma exacerbation treatment, and although many targeted therapies which block molecules that viruses use to infect the host have been used in a laboratory level, none has been yet approved for clinical use. Nevertheless, further understanding of the unique pathway that each virus follows to infect an individual may be crucial in the development of targeted therapies for the commonest viral pathogens to effectively prevent asthma exacerbations. Finally, biologic therapies resulted in a complete change of scenery in the treatment of severe asthma, especially with a T2 high phenotype. All available data suggest that monoclonal antibodies are safe and able to drastically reduce the rate of viral asthma exacerbations.

Effect of infant viral respiratory disease on childhood asthma in a non-industrialized setting

BACKGROUND

There are limited data from non-industrialized settings on the effects of early life viral respiratory disease on childhood respiratory illness. We followed a birth cohort in tropical Ecuador to understand how early viral respiratory disease, in the context of exposures affecting airway inflammation including ascariasis, affect wheezing illness, asthma, and rhinoconjunctivitis in later childhood.

METHODS

A surveillance cohort nested within a birth cohort was monitored for respiratory infections during the first 2 years in rural Ecuador and followed for 8 years for the development of wheeze and rhinoconjunctivitis. Nasal swabs were examined for viruses by polymerase chain reaction and respiratory symptom data on recent wheeze and rhinoconjunctivitis were collected by periodic questionnaires at 3, 5, and 8 years. Stools from pregnant mothers and periodically from children aged 2 years were examined microscopically for soil-transmitted helminths. Atopy was measured by allergen skin prick testing at 2 years. Spirometry, fractional exhaled nitric oxide measurement, and nasal washes were performed at 8 years. Associations between clinically significant respiratory disease (CSRD) and wheezing or rhinoconjunctivitis at 3, 5, and 8 years were estimated using multivariable logistic regression.

RESULTS

Four hundred and twenty six children were followed of which 67.7% had at least one CSRD episode; 12% had respiratory syncytial virus (RSV)+CSRD and 36% had rhinovirus (RHV)+CSRD. All-cause CSRD was associated with increased wheeze at 3 (OR 2.33 [95% confidence intervals (CI) 1.23-4.40]) and 5 (OR: 2.12 [95% CI 1.12-4.01]) years. RHV+CSRD was more strongly associated with wheeze at 3 years in STH-infected (STH-infected [OR 13.41, 95% CI 1.56-115.64] vs. uninfected [OR 1.68, 95% CI 0.73-3.84]) and SPT+ (SPT+ [OR 9.42, 95% CI 1.88-47.15] versus SPT- [OR 1.92, 95% CI 0.84-4.38]) children. No associations were observed between CSRD and rhinoconjunctivitis.

DISCUSSION

CSRD was significantly associated with childhood wheeze with stronger associations observed for RHV+CSRD in SPT+ and STH-infected children.

Review and Update of Active and Passive Immunization Against Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection (LRTI) in children, causing approximately 3.6 million hospitalizations per year, and has been associated with long-term pulmonary sequelae for up to 30 years after infection, yet preventative strategies and active treatment options remain elusive. The associated morbidity and healthcare related costs could be decreased substantially with the development of these much-needed medications. After an initial false start in the development of an RSV vaccine, gradual progress is now being made with the development of multiple vaccine candidates using numerous different mechanisms of action. Furthermore, nirsevimab, a new monoclonal antibody for the prevention of RSV, has recently been registered in the European Union. New novel treatments for RSV infection are also in the pipeline, which would provide the clinician with much needed ammunition in the management of the acute disease. The next few years have the potential to change the landscape of LRTI forever through the prevention and management of RSV LRTI and thereby decrease the mortality and morbidity associated with it. In this review, we discuss these new approaches, current research, and clinical trials in monoclonal antibody and vaccine development against RSV.

Association between early viral lower respiratory tract infections and subsequent asthma development

BACKGROUND

The association between hospitalization for human respiratory syncytial virus (HRSV) bronchiolitis in early childhood and subsequent asthma is well established. The long-term prognosis for non-bronchiolitis lower respiratory tract infections (LRTI) caused by viruses different from HRSV and rhinovirus, on the other hand, has received less interest.

AIM

To investigate the relationship between infant LRTI and later asthma and examine the influence of confounding factors.

METHODS

The PubMed and Global Index Medicus bibliographic databases were used to search for articles published up to October 2021 for this systematic review. We included cohort studies comparing the incidence of asthma between patients with and without LRTI at ≤ 2 years regardless of the virus responsible. The meta-analysis was performed using the random effects model. Sources of heterogeneity were assessed by stratified analyses.

RESULTS

This review included 15 articles (18 unique studies) that met the inclusion criteria. LRTIs at ≤ 2 years were associated with an increased risk of subsequent asthma up to 20 years [odds ratio (OR) = 5.0, 95%CI: 3.3-7.5], with doctor-diagnosed asthma (OR = 5.3, 95%CI: 3.3-8.6), current asthma (OR = 5.4, 95%CI: 2.7-10.6), and current medication for asthma (OR = 1.2, 95%CI: 0.7-3.9). Our overall estimates were not affected by publication bias (P = 0.671), but there was significant heterogeneity [I² = 58.8% (30.6-75.5)]. Compared to studies with hospitalized controls without LRTI, those with ambulatory controls had a significantly higher strength of association between LRTIs and subsequent asthma. The strength of the association between LRTIs and later asthma varied significantly by country and age at the time of the interview. The sensitivity analyses including only studies with similar proportions of confounding factors (gender, age at LRTI development, age at interview, gestational age, birth weight, weight, height, smoking exposure, crowding, family history of atopy, and family history of asthma) between cases and controls did not alter the overall estimates.

CONCLUSION

Regardless of the causative virus and confounding factors, viral LRTIs in children < 2 years are associated with an increased risk of developing a subsequent asthma. Parents and pediatricians should be informed of this risk.

Lung function at school age in infants with lower respiratory tract infections with and without wheezing: A birth cohort study

OBJECTIVE

To evaluate the relationship between lower respiratory tract infections (LRTI), in the first 2 years of life and lung function at school age in the Piccolipiù birth cohort (Italy).

METHODS

Data on LRTI (doctor diagnosis of bronchitis, bronchiolitis, pneumonia) and wheezing (≥3 episodes or a diagnosis of asthmatic bronchitis) in the first 2 years of life were obtained from parental questionnaires. Lung function was assessed at 7 years by spirometry and forced volume vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC, forced expiratory flow between 25% and 75%, and at 75% of FVC (FEF_25-75 and FEF₇₅ ) were reported as Z-scores. The associations between LRTI and spirometric variables were estimated with linear regression models.

RESULTS

Among 877 children studied, 22.1% had LRTI only, 5.4% wheezing only, 13.2% had both, and 59.3% had neither LRTI nor wheezing. Children with LRTI had lower FVC and FEV₁ than children without (Z-score differences: -0.18 [95% confidence intervals: -0.31; -0.06] and -0.15 [-0.27; -0.03]). When children were stratified by history of both LRTI and wheezing, there was no association between LRTI only and spirometric values. Conversely, having had both LRTI and wheezing was inversely associated with all lung function measures: Z-score differences of -0.24 (-0.42; -0.07); -0.42 (-0.59; -0.24); -0.25 (-0.41; -0.08); -0.37 (-0.54; -0.21); -0.30 (-0.46; -0.14) for FVC, FEV_1, FEV₁ /FVC, FEF_25-75 and FEF_75, respectively.

CONCLUSION

Infants with wheezing and LRTI, but not those with LRTI only, had reduced lung function at school-age.

An overview on the RSV-mediated mechanisms in the onset of non-allergic asthma

Respiratory syncytial virus (RSV) infection is recognized as an important risk factor for wheezing and asthma, since it commonly affects babies during lung development. While the role of RSV in the onset of atopic asthma is widely recognized, its impact on the onset of non-atopic asthma, mediated via other and independent causal pathways, has long been also suspected, but the association is less clear. Following RSV infection, the release of local pro-inflammatory molecules, the dysfunction of neural pathways, and the compromised epithelial integrity can become chronic and influence airway development, leading to bronchial hyperreactivity and asthma, regardless of atopic status. After a brief review of the RSV structure and its interaction with the immune system and neuronal pathways, this review summarizes the current evidence about the RSV-mediated pathogenic pathways in predisposing and inducing airway dysfunction and non-allergic asthma development.

Risk of asthma in children diagnosed with bronchiolitis during infancy: protocol of a longitudinal cohort study linking emergency department-based clinical data to provincial health administrative databases

INTRODUCTION

The Canadian Bronchiolitis Epinephrine Steroid Trial (CanBEST) and the Bronchiolitis Severity Cohort (BSC) study enrolled infants with bronchiolitis during the first year of life. The CanBEST trial suggested that treatment of infants with a combined therapy of high-dose corticosteroids and nebulised epinephrine reduced the risk of admission to hospital. Our study aims to-(1) quantify the risk of developing asthma by age 5 and 10 years in children treated with high-dose corticosteroid and epinephrine for bronchiolitis during infancy, (2) identify risk factors associated with development of asthma in children with bronchiolitis during infancy, (3) develop asthma prediction models for children diagnosed with bronchiolitis during infancy.

METHODS AND ANALYSIS

We propose a longitudinal cohort study in which we will link data from the CanBEST and BSC study with routinely collected data from provincial health administrative databases. Our outcome is asthma incidence measured using a validated health administrative data algorithm. Primary exposure will be treatment with a combined therapy of high-dose corticosteroids and nebulised epinephrine for bronchiolitis. Covariates will include type of viral pathogen, disease severity, medication use, maternal, prenatal, postnatal and demographic factors and variables related to health service utilisation for acute lower respiratory tract infection. The risk associated with development of asthma in children treated with high-dose corticosteroid and epinephrine for bronchiolitis will be assessed using multivariable Cox proportional hazards regression models. Prediction models will be developed using multivariable logistic regression analysis and internally validated using a bootstrap approach.

ETHICS AND DISSEMINATION

Our study has been approved by the ethics board of all four participating sites of the CanBEST and BSC study. Finding of the study will be disseminated to the academic community and relevant stakeholders through conferences and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

ISRCTN56745572; Post-results.

Association between early viral LRTI and subsequent wheezing development, a meta-analysis and sensitivity analyses for studies comparable for confounding factors

Introduction

Consideration of confounding factors about the association between Lower Respiratory Tract Infections (LRTI) in childhood and the development of subsequent wheezing has been incompletely described. We determined the association between viral LRTI at ≤ 5 years of age and the development of wheezing in adolescence or adulthood by a meta-analysis and a sensitivity analysis including comparable studies for major confounding factors.

Methods

We performed searches through Pubmed and Global Index Medicus databases. We selected cohort studies comparing the frequency of subsequent wheezing in children with and without LRTI in childhood regardless of the associated virus. We extracted the publication data, clinical and socio-demographic characteristics of the children, and confounding factors. We analyzed data using random effect model.

Results

The meta-analysis included 18 publications (22 studies) that met the inclusion criteria. These studies showed that viral LRTI in children ≤ 3 years was associated with an increased risk of subsequent development of wheezing (OR = 3.1, 95% CI = 2.4–3.9). The risk of developing subsequent wheezing was conserved when considering studies with comparable groups for socio-demographic and clinical confounders.

Conclusions

When considering studies with comparable groups for most confounding factors, our results provided strong evidence for the association between neonatal viral LRTI and the subsequent wheezing development. Further studies, particularly from lower-middle income countries, are needed to investigate the role of non-bronchiolitis and non-HRSV LRTI in the association between viral LRTI in childhood and the wheezing development later. In addition, more studies are needed to investigate the causal effect between childhood viral LRTI and the wheezing development later.

Trial registration

Review registration: PROSPERO, CRD42018116955; https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42018116955.

Asthma-Associated Long TSLP Inhibits the Production of IgA

Thymic stromal lymphopoietin (TSLP) contributes to asthmatic disease. The concentrations of protective IgA may be reduced in the respiratory tract of asthma patients. We investigated how homeostatic short TSLP (shTSLP) and asthma-associated long TSLP (loTSLP) regulate IgA production. B cells from healthy donors were stimulated in the presence or absence of shTSLP or loTSLP; the concentrations of IgA, IgM, IgE, and IgG antibodies were determined in cell culture supernatants; and B cells were analyzed by flow cytometry. LoTSLP, but not shTSLP, suppressed the secretion of IgA but not of IgE. The type 2 cytokine IL-4, which in addition to loTSLP contributes to asthmatic disease, did not affect the production of IgA or the frequency of IgA+ B cells. Instead, IL-4 increased IgG production, especially of the subclasses IgG2 and IgG4. LoTSLP inhibited IgA secretion by sorted memory B cells but not by naïve B cells. Although loTSLP inhibited IgA production, the vitamin A metabolite retinoic acid promoted the secretion of IgA, also in the presence of loTSLP, suggesting that vitamin A may promote IgA production in asthma. Our data demonstrate that asthma-associated loTSLP negatively regulates the secretion of IgA, which may negatively impact the surveillance of mucosal surfaces in asthma.

Viruses and asthma: the role of common respiratory viruses in asthma and its potential meaning for SARS-CoV-2

Viral infections and atopic diseases are closely related and contribute to each other. The physiological deficiencies and immune mechanisms that underlie atopic diseases can result in a suboptimal defense against multiple viruses, and promote a suitable environment for their proliferation and dissemination. Viral infections, on the other hand, can induce per se several immunological mechanisms involved in allergic inflammation capable to promote the initiation or exacerbation of atopic diseases such as atopic asthma. In a world that is affected more and more by factors that significantly impact the prevalence of atopic diseases, coronavirus disease 2019 (COVID-19) induced by the novel coronavirus severe acute respiratory syndrome (SARS-CoV-2) is having an unprecedented impact with still unpredictable consequences. Therefore, it is of crucial importance to revise the available scientific literature regarding the association between common respiratory viruses and asthma, as well as the newly emerging data about the molecular mechanisms of SARS-CoV-2 infection and its possible relation with asthma, to better understand the interrelation between common viruses and asthma and its potential meaning on the current global pandemic of COVID-19.

Assessing the strength of evidence for a causal effect of respiratory syncytial virus lower respiratory tract infections on subsequent wheezing illness: a systematic review and meta-analysis

Background

Although a positive association has been established, it is unclear whether lower respiratory tract infections (LRTIs) with respiratory syncytial virus (RSV) cause chronic wheezing illnesses. If RSV-LRTI were causal, we would expect RSV-LRTI prevention to reduce the incidence of chronic wheezing illnesses in addition to reducing acute disease. We aimed to evaluate the strength of evidence for a causal effect of RSV-LRTI on subsequent chronic wheezing illness to inform public health expectations for RSV vaccines.

Methods

We did a systematic review and meta-analysis of observational studies evaluating the association between RSV-LRTI and subsequent wheezing illness (exposure studies) and studies evaluating the association between RSV immunoprophylaxis and subsequent wheezing illness (immunoprophylaxis studies). Exposure studies were included if the exposure group members had an LRTI with laboratory-confirmed RSV and if the exposure ascertainment period began before 2 years of age and ended before 5 years of age. We required a wash-out period of more than 30 days between the index RSV-LRTI and the outcome measurement to allow for resolution of the acute illness. Comparisons between RSV-LRTI and non-RSV-LRTI were not included. Immunoprophylaxis studies were included if they measured the association with subsequent wheezing illness relative to a control group, either in a randomised controlled trial (RCT) or an observational design. For the immunoprophylaxis drugs in question, we required evidence of efficacy in targeting RSV-LRTI from at least one RCT to ensure biological plausibility. All variations of wheezing illness were combined into a single outcome that refers broadly to asthma or any other respiratory illness with wheezing symptoms. Ovid MEDLINE and Embase databases were searched from inception up to Aug 28, 2018. We evaluated whether data from exposure studies could provide evidence against the most viable non-causal theory that RSV-LRTI is a marker of respiratory illness susceptibility rather than a causal factor. Additionally, we tested whether RSV immunoprophylaxis reduces the odds of subsequent wheezing illnesses. We used a random-effects modelling framework and, to accommodate studies providing multiple correlated estimates, robust variance estimation meta-regressions. Meta-regression coefficients (b) quantify differences between exposure and comparator groups on the log_e odds ratio (log_e OR) scale.

Findings

From 14 235 records we identified 57 eligible articles that described 42 studies and provided 153 effect estimates. 35 studies estimated the direct effect of RSV-LRTI on wheezing illnesses (exposure studies) and eight evaluated the effect of RSV immunoprophylaxis (immunoprophylaxis studies). Exposure studies that adjusted for genetic influences yielded a smaller mean adjusted OR estimate (aOR₊ 2·45, 95% CI 1·23–4·88) compared with those that did not (4·17, 2·36–7·37), a significant difference (b 0·53, 95% CI 0·04–1·02). Infants who were not protected with RSV immunoprophylaxis tended to have higher odds of subsequent wheezing illness, as we would expect if RSV-LRTI were causal, but the effect was not significant (OR₊ 1·21, 95% CI 0·73–1·99). There was generally a high threat of confounding bias in the observational studies. Additionally, in both the observational studies and immunoprophylaxis RCTs, there was high risk of bias due to missing outcome data.

Interpretation

Our findings, limited to exposure and immunoprophylaxis studies, do not support basing policy decisions on an assumption that prevention of RSV-LRTI will reduce recurrent chronic wheezing illnesses.

Funding

Bill & Melinda Gates Foundation.

Pulmonary function sequelae after respiratory syncytial virus lower respiratory tract infection in children: A systematic review

Respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) during early childhood may be associated with subsequent pulmonary sequelae, including recurrent wheezing and asthma. We undertook a systematic review to investigate the pulmonary function sequelae following RSV LRTI in the first 3 years of life. The systematic review protocol was registered on PROSPERO (CRD42018087168). PubMed, Scopus, Cochrane Library, and World Health Organization Global Index Medicus, as well as ClinicalTrials.gov and Cochrane Central Register of Controlled Trials, were searched up until 15 June 2019 for published and unpublished interventional and observational studies with the end-point outcome of pulmonary function testing (PFT) after a proven RSV LRTI in the first 3 years of life. Two independent reviewers screened all the titles, abstracts and full texts. Data were extracted using a standardized data extraction form. Corresponding authors were contacted for additional information if required. All studies were assessed for risk of bias using the Newcastle-Ottawa quality assessment scale. The final analysis included 31 studies. Thirteen studies using spirometry reported no association between RSV LRTI and pulmonary function sequelae. The remaining 16 reported abnormal spirometry; 12 obstructive airways disease, three restrictive lung disease, and one mixed lung disease. The heterogeneity in PFT techniques, different ages at testing, and methods used for reporting outcomes made direct comparisons or pooled effect estimates impossible. Children with confirmed RSV LRTI during the first 3 years of life often have abnormal PFTs, favoring obstructive airways disease. The evidence, however, is not overwhelming with conflicting results between studies.

Differential asthma odds following respiratory infection in children from three minority populations

RATIONALE

Severe early-life respiratory illnesses, particularly those caused by respiratory syncytial virus (RSV) and human rhinovirus (HRV), are strongly associated with the development of asthma in children. Puerto Rican children in particular have a strikingly high asthma burden. However, prior studies of the potential associations between early-life respiratory illnesses and asthma in Puerto Rican and other minority populations have been limited.

OBJECTIVES

We sought to determine whether early-life respiratory illness was associated with asthma in Puerto Rican, Mexican American, and African American children.

METHODS

Using a logistic regression analysis, we examined the association between early-life respiratory illnesses (report of upper respiratory infection (URI), pneumonia, bronchitis, and bronchiolitis/RSV) within the first two years of life and physician-diagnosed asthma after the age of two in a large cohort of Puerto Rican, Mexican American, and African American children.

MEASUREMENTS AND MAIN RESULTS

While early-life respiratory illnesses were associated with greater asthma odds in Puerto Ricans, Mexican Americans, and African Americans, these associations were stronger among Puerto Rican children. Specifically, in Puerto Ricans, the odds was 6.15 (95% CI: 4.21-9.05) if the child reported at least one of the following respiratory illness: URI, pneumonia, bronchitis or bronchiolitis. The odds were also higher in Puerto Ricans when considering these conditions separately.

CONCLUSIONS

We observed population-specific associations between early-life respiratory illnesses and asthma, which were especially significant and stronger in Puerto Ricans. Taken together with the known high burden of RSV in Puerto Rico, our results may help explain the high burden of asthma in Puerto Ricans.

A Durable Relationship: Respiratory Syncytial Virus Bronchiolitis and Asthma past Their Golden Anniversary

Numerous preventive strategies against respiratory syncytial virus (RSV) are undergoing late stage evaluation in humans and, in addition to their intended benefit for acute illness, may impact long term consequences of infection in infants. Severe RSV infection has been repeatedly associated in the literature with long term complications, including impaired lung function, recurrent wheezing, and asthma. However, whether RSV lower respiratory tract infection (LRTI) causally affects the odds for developing wheezing and/or asthma during childhood requires further study, and the biological mechanisms underlying this hypothetical progression from viral illness to chronic lung disease are poorly characterized. In this review, we summarize the literature exploring the association between RSV LRTI in infancy and subsequent recurrent wheezing and pediatric asthma.

Association of early viral lower respiratory infections and subsequent development of atopy, a systematic review and meta-analysis of cohort studies

INTRODUCTION

Existing evidence on the relationship between childhood lower respiratory tract infections (LRTI) and the subsequent atopy development is controversial. We aimed to investigate an association between viral LRTI at <5 years and the development of atopy at > 2 years.

METHODS

We conducted a search at Embase, Pubmed, Web of Science, and Global Index Medicus. We collected data from the included articles. We estimated the odds ratio and the 95% confidence intervals with a random effect model. We determined factors associated with atopy development after childhood LRTI using univariate and multivariate meta-regression analyses. We recorded this systematic review at PROSPERO with the number CRD42018116955.

RESULTS

We included 24 studies. There was no relationship between viral LRTI at <5 years and skin prick test-diagnosed-atopy (OR = 1.2, [95% CI = 0.7-2.0]), unknown diagnosed-atopy (OR = 0.7, [95% CI = 0.4-1.3]), atopic dermatitis (OR = 1.2, [95% CI = 0.9-1.6]), hyperreactivity to pollen (OR = 0.8, [95% CI = 0.3-2.7]), food (OR = 0.8, [95% CI = 0.3-2.5]), or house dust mite (OR = 1.1, [95% CI = 0.6-2.2]). Although not confirmed in all studies with a symmetric distribution of the 23 confounding factors investigated, the overall analyses showed that there was a relationship between childhood viral LRTI at < 5 years and serum test diagnosed-atopy (OR = 2.0, [95% CI = 1.0-4.1]), allergic rhinoconjunctivitis (OR = 1.7, [95% CI = 1.1-2.9]), hyperreactivity diagnosed by serum tests with food (OR = 5.3, [1.7-16.7]) or inhaled allergens (OR = 4.2, [95% CI = 2.1-8.5]), or furred animals (OR = 0.6, [95% CI = 0.5-0.9]).

CONCLUSION

These results suggest that there is no association between viral LRTI at < 5 years and the majority of categories of atopy studied during this work. These results, however, are not confirmed for the remaining categories of atopy and more particularly those diagnosed by serum tests. There is a real need to develop more accurate atopy diagnostic tools.

Impact of Respiratory Syncytial Virus Infection on Host Functions: Implications for Antiviral Strategies

Respiratory syncytial virus (RSV) is one of the leading causes of viral respiratory tract infection in infants, the elderly, and the immunocompromised worldwide, causing more deaths each year than influenza. Years of research into RSV since its discovery over 60 yr ago have elucidated detailed mechanisms of the host-pathogen interface. RSV infection elicits widespread transcriptomic and proteomic changes, which both mediate the host innate and adaptive immune responses to infection, and reflect RSV's ability to circumvent the host stress responses, including stress granule formation, endoplasmic reticulum stress, oxidative stress, and programmed cell death. The combination of these events can severely impact on human lungs, resulting in airway remodeling and pathophysiology. The RSV membrane envelope glycoproteins (fusion F and attachment G), matrix (M) and nonstructural (NS) 1 and 2 proteins play key roles in modulating host cell functions to promote the infectious cycle. This review presents a comprehensive overview of how RSV impacts the host response to infection and how detailed knowledge of the mechanisms thereof can inform the development of new approaches to develop RSV vaccines and therapeutics.

Effect of acute respiratory infections in infancy on pulmonary function test at 3 years of age: a prospective birth cohort study

INTRODUCTION

Acute respiratory infections (ARIs) in infancy may have a long-term impact on the developing respiratory system. We planned a prospective cohort study to determine the impact of ARI during infancy on the pulmonary function test indices at 3 years of age.

METHODS

A cohort of normal, full-term newborns were followed up 6 monthly and during ARI episodes. Infant pulmonary function tests (IPFTs) were performed at baseline and each follow-up visit using tidal breathing flow-volume loop, rapid thoracoabdominal compression (RTC) and raised volume RTC manoeuvres. During each ARI episode, nasopharyngeal aspirates were tested for respiratory pathogens by real-time PCR.

RESULTS

We screened 3421 neonates; 310 were enrolled; IPFT was performed in 225 (boys: 125 (55.6%)) at 3 years. During infancy, 470 ARI episodes were documented in 173 infants. At 3 years, children with history of any ARI episode during infancy had lower forced expiratory volume in 1 s (FEV_1.0), forced expiratory volume in 0.75 s (FEV_0.75), forced expiratory volume in 0.5 s (FEV_0.5), forced expiratory flow between 25% and 75% of FVC (FEF_25-75), and maximal expiratory flow at 25% of FVC (MEF₂₅) as compared with those without any ARI episode during infancy. The ratio of tidal expiratory flow (TEF) at 25% or 50% of tidal expiratory volume to peak TEF (TEF₅₀ or TEF₂₅/peak TEF) at 3 years was significantly increased in children who had ARI in infancy.

CONCLUSIONS

ARI during infancy is associated with impaired pulmonary function indices such as increased resistance and decreased forced expiratory flow and volume at 3 years of age.

Does respiratory syncytial virus lower respiratory illness in early life cause recurrent wheeze of early childhood and asthma? Critical review of the evidence and guidance for future studies from a World Health Organization-sponsored meeting

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection (LRTI) and hospitalization in infants and children globally. Many observational studies have found an association between RSV LRTI in early life and subsequent respiratory morbidity, including recurrent wheeze of early childhood (RWEC) and asthma. Conversely, two randomized placebo-controlled trials of efficacious anti-RSV monoclonal antibodies (mAbs) in heterogenous infant populations found no difference in physician-diagnosed RWEC or asthma by treatment group. If a causal association exists and RSV vaccines and mAbs can prevent a substantial fraction of RWEC/asthma, the full public health value of these interventions would markedly increase. The primary alternative interpretation of the observational data is that RSV LRTI in early life is a marker of an underlying predisposition for the development of RWEC and asthma. If this is the case, RSV vaccines and mAbs would not necessarily be expected to impact these outcomes. To evaluate whether the available evidence supports a causal association between RSV LRTI and RWEC/asthma and to provide guidance for future studies, the World Health Organization convened a meeting of subject matter experts on February 12-13, 2019 in Geneva, Switzerland. After discussing relevant background information and reviewing the current epidemiologic evidence, the group determined that: (i) the evidence is inconclusive in establishing a causal association between RSV LRTI and RWEC/asthma, (ii) the evidence does not establish that RSV mAbs (and, by extension, future vaccines) will have a substantial effect on these outcomes and (iii) regardless of the association with long-term childhood respiratory morbidity, severe acute RSV disease in young children poses a substantial public health burden and should continue to be the primary consideration for policy-setting bodies deliberating on RSV vaccine and mAb recommendations. Nonetheless, the group recognized the public health importance of resolving this question and suggested good practice guidelines for future studies.

Childhood pneumonia, pleurisy and lung function: a cohort study from the first to sixth decade of life

INTRODUCTION

Adult spirometry following community-acquired childhood pneumonia has variably been reported as showing obstructive or non-obstructive deficits. We analysed associations between doctor-diagnosed childhood pneumonia/pleurisy and more comprehensive lung function in a middle-aged general population cohort born in 1961.

METHODS

Data were from the prospective population-based Tasmanian Longitudinal Health Study cohort. Analysed lung function was from ages 7 years (prebronchodilator spirometry only, n=7097), 45 years (postbronchodilator spirometry, carbon monoxide transfer factor and static lung volumes, n=1220) and 53 years (postbronchodilator spirometry and transfer factor, n=2485). Parent-recalled histories of doctor-diagnosed childhood pneumonia and/or pleurisy were recorded at age 7. Multivariable linear and logistic regression were used.

RESULTS

At age 7, compared with no episodes, childhood pneumonia/pleurisy-ever was associated with reduced FEV₁:FVC for only those with current asthma (beta-coefficient or change in z-score=-0.20 SD, 95% CI -0.38 to -0.02, p=0.028, p interaction=0.036). At age 45, for all participants, childhood pneumonia/pleurisy-ever was associated with a restrictive pattern: OR 3.02 (1.5 to 6.0), p=0.002 for spirometric restriction (FVC less than the lower limit of normal plus FEV₁:FVC greater than the lower limit of normal); total lung capacity z-score -0.26 SD (95% CI -0.38 to -0.13), p<0.001; functional residual capacity -0.16 SD (-0.34 to -0.08), p=0.001; and residual volume -0.18 SD (-0.31 to -0.05), p=0.008. Reduced lung volumes were accompanied by increased carbon monoxide transfer coefficient at both time points (z-score +0.29 SD (0.11 to 0.49), p=0.001 and +0.17 SD (0.04 to 0.29), p=0.008, respectively).

DISCUSSION

For this community-based population, doctor-diagnosed childhood pneumonia and/or pleurisy were associated with obstructed lung function at age 7 for children who had current asthma symptoms, but with evidence of 'smaller lungs' when in middle age.

The Impact of RSV-Associated Respiratory Disease on Children in Asia

Acute respiratory tract infections (ARTIs) are leading contributors to the global infectious disease burden, which is estimated to be 112,900,000 disability adjusted life years. Viruses contribute to the etiology of ARTIs in a big way compared with other microorganisms. Since the discovery of respiratory syncytial virus (RSV) 61 years ago, the virus has been recognized as a major cause of ARTI and hospitalization in children. The morbidity and mortality attributable to RSV infection appear to be higher in infants < 3 months and in those with known risk factors such as prematurity, chronic lung, and congenital heart diseases. Crowded living conditions, exposure to tobacco smoke, and industrial or other types of air pollution also increase the risk of RSV-associated ARTI. Many epidemiological studies have been conducted in developed countries to understand the seasonal patterns and risk factors associated with RSV infections. Dearth of information on RSV-associated morbidity and mortality in Asian and developing countries indicates the need for regional reviews to evaluate RSV-associated disease burden in these countries. Epidemiological studies including surveillance is the key to track the disease burden including risk factors, seasonality, morbidity, and mortality associated with RSV infection in these countries. These data will contribute to improve the clinical diagnosis and plan preventive strategies in resource-limited developing countries.

Should we use Palivizumab immunoprophylaxis for infants against respiratory syncytial virus? - a cost-utility analysis

BACKGROUND

Passive immunization against RSV (Respiratory Syncytial Virus) is given in most western countries (including Israel) to infants of high risk groups such as premature babies, and infants with Congenital Heart Disease or Congenital Lung Disease. However, immunoprophylaxis costs are extremely high ($2800-$4200 per infant). Using cost-utility analysis criteria, we evaluate whether it is justified to expand, continue or restrict nationwide immunoprophylaxis using palivizumab of high risk infants against RSV.

METHODS

Epidemiological, demographic, health service utilisation and economic data were integrated from primary (National Hospitalization Data, etc.) and secondary data sources (ie: from published articles) into a spread-sheet to calculate the cost per averted disability-adjusted life year (DALY) of vaccinating various infant risk groups. Costs of intervention included antibody plus administration costs. Treatment savings and DALYs averted were estimated from applying vaccine efficacy data to relative risks of being hospitalised and treated for RSV, including possible long-term sequelae like asthma and wheezing.

RESULTS

For all the groups RSV immunoprophylaxis is clearly not cost effective as its cost per averted DALY exceeds the $105,986 guideline representing thrice the per capita Gross Domestic Product. Vaccine price would have to fall by 48.1% in order to justify vaccinating Congenital Heart Disease or Congenital Lung Disease risk groups respectively on pure cost-effectiveness grounds. For premature babies of < 29 weeks, 29-32 and 33-36 weeks gestation, decreases of 36.8%, 54.5% and 83.3% respectively in vaccine price are required.

CONCLUSIONS

Based solely on cost-utility analysis, at current price levels it is difficult to justify the current indications for passive vaccination with Palivizumab against RSV. However, if the manufacturers would reduce the price by 54.5% then it would be cost-effective to vaccinate the Congenital Heart Disease or Congenital Lung Disease risk groups as well as premature babies born before the 33rd week of gestation.

Antibodies in lymphocyte supernatants can distinguish between neutralising antibodies induced by RSV vaccination and pre-existing antibodies induced by natural infection

INTRODUCTION

Respiratory syncytial virus (RSV) is the single most important cause of severe respiratory illness in infants. There is no effective vaccine and the only effective treatment available is the monoclonal antibody palivizumab which reduces the risk of severe RSV disease in prematurely born infants. However, palivizumab is too costly to allow for wide implementation and thus treatment is restricted to supportive care. Despite extensive efforts to develop a vaccine, progress has been hindered by the difficulty in measuring and assessing immunological correlates of RSV vaccine efficacy in the presence of high levels of pre-existing RSV antibodies.

METHODS

Here we describe a new method for measuring the functional activity of antibodies induced by vaccination distinct from pre-existing antibodies. Antibodies in lymphocyte supernatants (ALS) from the cultured peripheral blood mononuclear cells (PBMCs) of young adults who had recently been vaccinated with a novel RSV candidate vaccine were directly assayed for virus neutralising activity. An ELISA method was used to measure antibodies in nasal and serum samples and then compared with the adapted ALS based method.

RESULTS

There was a wide background distribution of RSV-specific antibodies in serum and nasal samples that obscured vaccine-specific responses measured two weeks after vaccination. No RSV-specific antibodies were observed at baseline in ALS samples, but a clear vaccine-specific antibody response was observed in ALS seven days after the administration of each dose of vaccine. These vaccine-specific antibodies in ALS displayed functional activity in vitro, and quantification of this functional activity was unperturbed by pre-existing antibodies from natural exposure. The results demonstrate a promising new approach for assessing functional immune responses attributed to RSV vaccines.

Childhood measles contributes to post-bronchodilator airflow obstruction in middle-aged adults: A cohort study

BACKGROUND AND OBJECTIVE

Chronic obstructive pulmonary disease (COPD) has potential origins in childhood but an association between childhood measles and post-bronchodilator (BD) airflow obstruction (AO) has not yet been shown. We investigated whether childhood measles contributed to post-BD AO through interactions with asthma and/or smoking in a non-immunized middle-aged population.

METHODS

The population-based Tasmanian Longitudinal Health Study (TAHS) cohort born in 1961 (n = 8583) underwent spirometry in 1968 before immunization was introduced. A history of childhood measles infection was obtained from school medical records. During the fifth decade follow-up (n = 5729 responses), a subgroup underwent further lung function measurements (n = 1389). Relevant main associations and interactions by asthma and/or smoking on post-BD forced expiratory volume in 1 s/forced vital capacity (FEV₁ /FVC; continuous variable) and AO (FEV₁ /FVC < lower limit of normal) were estimated by multiple regression.

RESULTS

Sixty-nine percent (n = 950) had a history of childhood measles. Childhood measles augmented the combined adverse effect of current clinical asthma and smoking at least 10 pack-years on post-BD FEV₁ /FVC ratio in middle age (z-score: -0.70 (95% CI: -1.1 to -0.3) vs -1.36 (-1.6 to -1.1), three-way interaction: P = 0.009), especially for those with childhood-onset asthma. For never- and ever-smokers of <10 pack-years who had current asthma symptoms, compared with those without childhood measles, paradoxically, the odds for post-BD AO was not significant in the presence of childhood measles (OR: 12.0 (95% CI: 3.4-42) vs 2.17 (0.9-5.3)).

CONCLUSION

Childhood measles infection appears to compound the associations between smoking, current asthma and post-BD AO. Differences between asthma subgroups provide further insight into the complex aetiology of obstructive lung diseases for middle-aged adults.

Respiratory viral infections in infancy and school age respiratory outcomes and healthcare costs

OBJECTIVES

To determine the impact of viral lower respiratory tract infections (LRTIs) in infancy including rhinovirus (RV) and infancy respiratory syncytial virus (RSV), on school age pulmonary function and healthcare utilization in prematurely born children.

WORKING HYPOTHESIS

School age respiratory outcomes would be worse and healthcare utilization greater in children who had viral LRTIs in infancy.

STUDY DESIGN

Prospective study.

SUBJECT SELECTION

A cohort of prematurely born children who had symptomatic LRTIs during infancy documented, was recalled.

METHODS

Pulmonary function was assessed at 5 to 7 years of age and health related costs of care from aged one to follow-up determined.

RESULTS

Fifty-one children, median gestational age 33⁺⁶ weeks, were assessed at a median (IQR) age 7.03 (6.37-7.26) years. Twenty-one children had no LRTI, 14 RV LRTI, 10 RSV LRTI, and 6 another viral LRTI (other LRTI). Compared to the no LRTI group, the RV group had a lower FEV₁ (P = 0.033) and the other LRTI group a lower FVC (P = 0.006). Non-respiratory medication costs were higher in the RV (P = 0.018) and RSV (P = 0.013) groups. Overall respiratory healthcare costs in the RV (£153/year) and RSV (£27/year) groups did not differ significantly from the no LRTI group (£56/year); the other LRTI group (£431/year) had higher respiratory healthcare costs (P = 0.042).

CONCLUSIONS

In moderately prematurely born children, RV and RSV LRTIs in infancy were not associated with higher respiratory healthcare costs after infancy. Children who experienced LRTIs caused by other respiratory viruses (including RV) had higher respiratory healthcare costs and greater pulmonary function impairment.

A population-based prospective cohort study examining the influence of early-life respiratory tract infections on school-age lung function and asthma

BACKGROUND

Early-life respiratory tract infections could affect airway obstruction and increase asthma risk in later life. However, results from previous studies are inconsistent.

OBJECTIVE

We examined the associations of early-life respiratory tract infections with lung function and asthma in school-aged children.

METHODS

This study among 5197 children born between April 2002 and January 2006 was embedded in a population-based prospective cohort study. Information on physician-attended upper and lower respiratory tract infections until age 6 years (categorised into ≤ 3 and >3-6 years) was obtained by annual questionnaires. Spirometry measures and physician-diagnosed asthma were assessed at age 10 years.

RESULTS

Upper respiratory tract infections were not associated with adverse respiratory outcomes. Compared with children without lower respiratory tract infections ≤3 years, children with lower respiratory tract infections ≤3 years had a lower FEV₁, FVC, FEV₁:FVC and forced expiratory flow at 75% of FVC (FEF₇₅) (Z-score (95% CI): ranging from -0.22 (-0.31 to -0.12) to -0.12 (-0.21 to -0.03)) and an increased risk of asthma (OR (95% CI): 1.79 (1.19 to 2.59)). Children with lower respiratory tract infections >3-6 years had an increased risk of asthma (3.53 (2.37 to 5.17)) only. Results were not mediated by antibiotic or paracetamol use and not modified by inhalant allergic sensitisation. Cross-lagged modelling showed that results were not bidirectional and independent of preschool wheezing patterns.

CONCLUSION

Early-life lower respiratory tract infections ≤3 years are most consistently associated with lower lung function and increased risk of asthma in school-aged children.

A population-based prospective cohort study examining the influence of early-life respiratory tract infections on school-age lung function and asthma

BACKGROUND

Early-life respiratory tract infections could affect airway obstruction and increase asthma risk in later life. However, results from previous studies are inconsistent.

OBJECTIVE

We examined the associations of early-life respiratory tract infections with lung function and asthma in school-aged children.

METHODS

This study among 5197 children born between April 2002 and January 2006 was embedded in a population-based prospective cohort study. Information on physician-attended upper and lower respiratory tract infections until age 6 years (categorised into ≤ 3 and >3-6 years) was obtained by annual questionnaires. Spirometry measures and physician-diagnosed asthma were assessed at age 10 years.

RESULTS

Upper respiratory tract infections were not associated with adverse respiratory outcomes. Compared with children without lower respiratory tract infections ≤3 years, children with lower respiratory tract infections ≤3 years had a lower FEV₁, FVC, FEV₁:FVC and forced expiratory flow at 75% of FVC (FEF₇₅) (Z-score (95% CI): ranging from -0.22 (-0.31 to -0.12) to -0.12 (-0.21 to -0.03)) and an increased risk of asthma (OR (95% CI): 1.79 (1.19 to 2.59)). Children with lower respiratory tract infections >3-6 years had an increased risk of asthma (3.53 (2.37 to 5.17)) only. Results were not mediated by antibiotic or paracetamol use and not modified by inhalant allergic sensitisation. Cross-lagged modelling showed that results were not bidirectional and independent of preschool wheezing patterns.

CONCLUSION

Early-life lower respiratory tract infections ≤3 years are most consistently associated with lower lung function and increased risk of asthma in school-aged children.

Modulation of Host Immunity by Human Respiratory Syncytial Virus Virulence Factors: A Synergic Inhibition of Both Innate and Adaptive Immunity

The Human Respiratory Syncytial Virus (hRSV) is a major cause of acute lower respiratory tract infections (ARTIs) and high rates of hospitalizations in children and in the elderly worldwide. Symptoms of hRSV infection include bronchiolitis and pneumonia. The lung pathology observed during hRSV infection is due in part to an exacerbated host immune response, characterized by immune cell infiltration to the lungs. HRSV is an enveloped virus, a member of the Pneumoviridae family, with a non-segmented genome and negative polarity-single RNA that contains 10 genes encoding for 11 proteins. These include the Fusion protein (F), the Glycoprotein (G), and the Small Hydrophobic (SH) protein, which are located on the virus surface. In addition, the Nucleoprotein (N), Phosphoprotein (P) large polymerase protein (L) part of the RNA-dependent RNA polymerase complex, the M2-1 protein as a transcription elongation factor, the M2-2 protein as a regulator of viral transcription and (M) protein all of which locate inside the virion. Apart from the structural proteins, the hRSV genome encodes for the non-structural 1 and 2 proteins (NS1 and NS2). HRSV has developed different strategies to evade the host immunity by means of the function of some of these proteins that work as virulence factors to improve the infection in the lung tissue. Also, hRSV NS-1 and NS-2 proteins have been shown to inhibit the activation of the type I interferon response. Furthermore, the hRSV nucleoprotein has been shown to inhibit the immunological synapsis between the dendritic cells and T cells during infection, resulting in an inefficient T cell activation. Here, we discuss the hRSV virulence factors and the host immunological features raised during infection with this virus.

New Insights Contributing to the Development of Effective Vaccines and Therapies to Reduce the Pathology Caused by hRSV

Human Respiratory Syncytial Virus (hRSV) is one of the major causes of acute lower respiratory tract infections (ALRTI) worldwide, leading to significant levels of immunocompromisation as well as morbidity and mortality in infants. Its main target of infection is the ciliated epithelium of the lungs and the host immune responses elicited is ineffective at achieving viral clearance. It is thought that the lack of effective immunity against hRSV is due in part to the activity of several viral proteins that modulate the host immune response, enhancing a Th2-like pro-inflammatory state, with the secretion of cytokines that promote the infiltration of immune cells to the lungs, with consequent damage. Furthermore, the adaptive immunity triggered by hRSV infection is characterized by weak cytotoxic T cell responses and secretion of low affinity antibodies by B cells. These features of hRSV infection have meant that, to date, no effective and safe vaccines have been licensed. In this article, we will review in detail the information regarding hRSV characteristics, pathology, and host immune response, along with several prophylactic treatments and vaccine prototypes. We will also expose significant data regarding the newly developed BCG-based vaccine that promotes protective cellular and humoral response against hRSV infection, which is currently undergoing clinical evaluation.

Palivizumab Prophylaxis in Preterm Infants and Subsequent Recurrent Wheezing. Six-Year Follow-up Study

RATIONALE

Respiratory syncytial virus (RSV) induces not only infantile recurrent wheezing but also potentially atopic asthma.

OBJECTIVES

To test the effect of RSV infection on development of subsequent atopic asthma, we evaluated whether palivizumab, an anti-RSV monoclonal antibody, by preventing severe RSV disease in the first year of life, could impact subsequent recurrent wheezing and atopic asthma at 6 years of age.

METHODS

During the 2007 to 2008 RSV season, the decision to administer palivizumab was made based on standard medical practice and an observational prospective multicenter (n = 52) case-control study in preterm infants with a gestational age between 33 and 35 weeks followed from 0 to 3 years (preceding Committee on Recurrent Wheezing study). The 52 investigators at hospitals then followed these subjects until 6 years of age, reported here (Effects of Preventive Treatment for Respiratory Syncytial [RS] Virus Infection During Infancy on Later Atopic Asthma in Preterm Infants; Scientific Committee for Elucidation of Infantile Asthma). Parents of study subjects reported the infants' physicians' assessment of recurrent wheezing, using a report card and a novel mobile phone-based reporting system using the Internet. The primary endpoint was the incidence of atopic asthma.

MEASUREMENTS AND MAIN RESULTS

Of 444 preterm infants enrolled, 349 received palivizumab during the first year of life. At 6 years, atopic asthma was not different in the groups: 15.3 and 18.2% of infants in the treated and untreated groups, respectively (P = 0.57). On the other hand, physician-diagnosed recurrent wheezing was observed in 15.3 and 31.6% in the treated and untreated groups, respectively (P = 0.003).

CONCLUSIONS

Palivizumab prophylaxis administered to preterm infants did not suppress the onset of atopic asthma but resulted in a significantly lower incidence of recurrent wheezing during the first 6 years. Clinical trial registered with www.clinicaltrials.gov (NCT 01545245).

Bronchiolitis in young infants: is it a risk factor for recurrent wheezing in childhood?

BACKGROUND

Acute bronchiolitis in infancy is considered a risk factor for recurrent wheezing episodes in childhood. The present study assessed prevalence, clinical manifestations and risk factors for recurrent wheezing events during the first 3 years of life and persistent wheezing events beyond this age in children hospitalized as young infants with acute bronchiolitis.

METHODS

Two groups of children aged 6 years were included. The study group comprised 150 children with a history of hospitalization for bronchiolitis, with the first event at <6 months of age. The control group comprised 66 age- and sex-matched children with no history of bronchiolitis before 6 months of age. Children in both groups had been followed until 6 years of age by their pediatricians; data were obtained retrospectively by reviewing ambulatory records during children's visits in pediatricians' clinics. The data included epidemiological parameters, prevalence, age at onset, number of and treatments given for episodes of wheezing events prior to 6 years of age, pathogens detected, and severity of acute bronchiolitis in the study group.

RESULTS

Overall, 58% and 27% of children in the study and control groups, respectively (P=0.001) had recurrent wheezing episodes prior to the age of 3 years. Children in the study group had earlier onset of recurrent wheezing, had more episodes of wheezing, and required more bronchodilator and systemic steroids treatments compared to the control group.

CONCLUSION

Hospitalization within the first six months of life for acute bronchiolitis is an independent risk factor for recurrent wheezing episodes during the first 3 years of life.

Genes associated with RSV lower respiratory tract infection and asthma: the application of genetic epidemiological methods to understand causality

Infants with respiratory syncytial virus (RSV) lower respiratory tract infections (LRIs) are at increased risk for childhood asthma. The objectives of this article are to review the genes associated with both RSV LRI and asthma, review analytic approaches to assessing shared genetic risk and propose a future perspective on how these approaches can help us to understand the role of infant RSV infection as both an important risk factor for asthma and marker of shared genetic etiology between the two conditions. The review of shared genes and thus pathways associated with severity of response to RSV infection and asthma risk can help us to understand mechanisms of disease and ultimately propose new and novel targets for primary prevention of both diseases.

Association between respiratory infections in early life and later asthma is independent of virus type

Background

Lower respiratory tract infections in the first years of life are associated with later asthma, and this observation has led to a focus on the potential causal role of specific respiratory viruses, such as rhinoviruses and respiratory syncytial virus, in asthma development. However, many respiratory viruses and bacteria trigger similar respiratory symptoms and it is possible that the important risk factors for asthma are the underlying susceptibility to infection and the exaggerated reaction to such triggers rather than the particular triggering agent.

Objective

We sought to study the association between specific infections in early life and development of asthma later in childhood.

Methods

Three hundred thirteen children were followed prospectively in the Copenhagen Prospective Studies of Asthma in Childhood₂₀₀₀ high-risk birth cohort. Nine respiratory virus types (respiratory syncytial virus, rhinoviruses, other picornaviruses, coronaviruses 229E and OC43, parainfluenza viruses 1-3, influenza viruses AH1, AH3, and B, human metapneumovirus, adenoviruses, and bocavirus) and 3 pathogenic airway bacteria (Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis) were identified in airway secretions sampled during episodes of troublesome lung symptoms in the first 3 years of life. Asthma was determined by age 7 years.

Results

In unadjusted analyses, all viruses and pathogenic bacteria identified during episodes of troublesome lung symptoms were associated with increased risk of asthma by age 7 years with similar odds ratios for all viruses and pathogenic bacteria. After adjustment for the frequency of respiratory episodes, the particular triggers were no longer associated with asthma.

Conclusion

The number of respiratory episodes in the first years of life, but not the particular viral trigger, was associated with later asthma development. This suggests that future research should focus on the susceptibility and exaggerated response to lower respiratory tract infections in general rather than on the specific triggering agent.

Pneumonia in childhood and impaired lung function in adults: a longitudinal study

BACKGROUND

Diminished lung function and increased prevalence of asthma have been reported in children with a history of early lower respiratory illnesses (LRIs), including pneumonia. Whether these associations persist up to adulthood has not been established.

METHODS

As part of the prospective Tucson Children's Respiratory Study, LRIs during the first 3 years of life were ascertained by pediatricians. Spirometry was performed at ages 11, 16, 22, and 26 years. The occurrence of asthma/wheeze during the previous year was ascertained at ages 11, 13, 16, 18, 22, 24, 26, and 29 years. Longitudinal random effects models and generalized estimating equations were used to assess the relation of LRIs to lung function and asthma.

RESULTS

Compared with participants without early-life LRIs, those with pneumonia had the most severe subsequent lung function impairment, with mean ± SE deficits of -3.9% ± 0.9% (P < .001) and -2.5% ± 0.8% (P = .001) for pre- and post-bronchodilator FEV1:FVC ratio from age 11 to 26 years, respectively. Pneumonia was associated with increased risk for asthma (odds ratio [OR]: 1.95; 95% confidence interval [CI]: 1.11-3.44) and wheeze (OR: 1.94; 95% CI: 1.28-2.95) over the same age range. Early non-pneumonia LRIs were associated with mildly impaired pre-bronchodilator FEV1 (-62.8 ± 27.9 mL, P = .024) and FEV1:FVC ratio (-1.1 ± 0.5%, P = .018), and wheeze (OR: 1.37; 95% CI: 1.09-1.72).

CONCLUSIONS

Early pneumonia is associated with asthma and impaired airway function, which is partially reversible with bronchodilators and persists into adulthood. Early pneumonia may be a major risk factor for adult chronic obstructive pulmonary disease.

The Respiratory System

This chapter addresses upper airway physiology for the pediatric intensivist, focusing on functions that affect ventilation, with an emphasis on laryngeal physiology and control in breathing. Effective control of breathing ensures that the airway is protected, maintains volume homeostasis, and provides ventilation. Upper airway structures are effectors for all of these functions that affect the entire airway. Nasal functions include air conditioning and protective reflexes that can be exaggerated and involve circulatory changes. Oral cavity and pharyngeal patency enable airflow and feeding, but during sleep pharyngeal closure can result in apnea. Coordination of breathing with sucking and nutritive swallowing alters during development, while nonnutritive swallowing at all ages limits aspiration. Laryngeal functions in breathing include protection of the subglottic airway, active maintenance of its absolute volume, and control of tidal flow patterns. These are vital functions for normal lung growth in fetal life and during rapid adaptations to breathing challenges from birth through adulthood. Active central control of breathing focuses on the coordination of laryngeal and diaphragmatic activities, which adapts according to the integration of central and peripheral inputs. For the intensivist, knowledge of upper airway physiology can be applied to improve respiratory support. In a second part the mechanical properties of the respiratory system as a critical component of the chain of events that result in translation of the output of the respiratory rhythm generator to ventilation are described. A comprehensive understanding of respiratory mechanics is essential to the delivery of optimized and individualized mechanical ventilation. The basic elements of respiratory mechanics will be described and developmental changes in the airways, lungs, and chest wall that impact on measurement of respiratory mechanics with advancing postnatal age are reviewed. This will be follwowed by two sections, the first on respiratory mechanics in various neonatal pathologies and the second in pediatric pathologies. The latter can be classified in three categories. First, restrictive diseases may be of pulmonary origin, such as chronic interstitial lung diseases or acute lung injury/acute respiratory distress syndrome, which are usually associated with reduced lung compliance. Restrictive diseases may also be due to chest wall abnormalities such as obesity or scoliosis (idiopathic or secondary to neuromuscular diseases), which are associated with a reduction in chest wall compliance. Second, obstructive diseases are represented by asthma and wheezing disorders, cystic fibrosis, long term sequelae of neonatal lung disease and bronchiolitis obliterans following hematopoietic stem cell transplantation. Obstructive diseases are defined by a reduced FEV1/VC ratio. Third, neuromuscular diseases, mainly represented by DMD and SMA, are associated with a decrease in vital capacity linked to respiratory muscle weakness that is better detected by PImax, PEmax and SNIP measurements.

Immunity to RSV in Early-Life

Respiratory Syncytial Virus (RSV) is the commonest cause of severe respiratory infection in infants, leading to over 3 million hospitalizations and around 66,000 deaths worldwide each year. RSV bronchiolitis predominantly strikes apparently healthy infants, with age as the principal risk factor for severe disease. The differences in the immune response to RSV in the very young are likely to be key to determining the clinical outcome of this common infection. Remarkable age-related differences in innate cytokine responses follow recognition of RSV by numerous pattern recognition receptors, and the importance of this early response is supported by polymorphisms in many early innate genes, which associate with bronchiolitis. In the absence of strong, Th1 polarizing signals, infants develop T cell responses that can be biased away from protective Th1 and cytotoxic T cell immunity toward dysregulated, Th2 and Th17 polarization. This may contribute not only to the initial inflammation in bronchiolitis, but also to the long-term increased risk of developing wheeze and asthma later in life. An early-life vaccine for RSV will need to overcome the difficulties of generating a protective response in infants, and the proven risks associated with generating an inappropriate response. Infantile T follicular helper and B cell responses are immature, but maternal antibodies can afford some protection. Thus, maternal vaccination is a promising alternative approach. However, even in adults adaptive immunity following natural infection is poorly protective, allowing re-infection even with the same strain of RSV. This gives us few clues as to how effective vaccination could be achieved. Challenges remain in understanding how respiratory immunity matures with age, and the external factors influencing its development. Determining why some infants develop bronchiolitis should lead to new therapies to lessen the clinical impact of RSV and aid the rational design of protective vaccines.

Japanese pediatric guideline for the treatment and management of bronchial asthma 2012

A new version of the Japanese pediatric guideline for the treatment and management of bronchial asthma was published in Japanese at the end of 2011. The guideline sets the pragmatic goal for clinicians treating childhood asthma as maintaining a "well-controlled level" for an extended period in which the child patient can lead a trouble-free daily life, not forgetting the ultimate goal of obtaining remission and/or cure. Important factors in the attainment of the pragmatic goal are: (i) appropriate use of anti-inflammatory drugs; (ii) elimination of environmental risk factors; and (iii) educational and enlightening activities for the patient and caregivers regarding adequate asthma management in daily life. The well-controlled level refers to a symptom-free state in which no transient coughs, wheezing, dyspnea or other symptoms associated with bronchial asthma are present, even for a short period of time. As was the case in the previous versions of the guideline, asthmatic children younger than 2 years of age are defined as infantile asthma patients. Special attention is paid to these patients in the new guideline: they often have rapid exacerbation and easily present chronic asthmatic conditions after the disease is established.

A population-based study of childhood respiratory morbidity after severe lower respiratory tract infections in early childhood

OBJECTIVES

To estimate the risk of childhood chronic respiratory morbidity among those hospitalized for severe lower respiratory tract infection (LRTI) in early childhood, and to determine whether severe LRTI is an independent predictor.

STUDY DESIGN

The population-based Régie de l'Assurance Maladie du Québec datasets were used to identify LRTI hospitalizations before age 2 years in a birth cohort from 1996-1997 and a comparison cohort of children without an LRTI hospitalization. The incidence rate and incidence rate ratio of chronic respiratory morbidity before age 10 years were calculated, and multivariable logistic regression was performed to estimate the impact of LRTI hospitalization on chronic respiratory morbidity. Population-attributable risks of chronic respiratory morbidity due to severe LRTI were estimated, and similar analyses were performed for respiratory syncytial virus LRTI.

RESULTS

Among the birth cohort, 7104 patients (4.9%) were hospitalized for LRTI before age 2 years. By age 10 years, 52.5% of the LRTI cohort and 27.9% of the nonhospitalized cohort had developed chronic respiratory morbidity; the incidence rate ratio was 1.81 (95% CI, 1.76-1.86) for males and 1.91 (95% CI, 1.84-1.99) for females. The OR for chronic respiratory morbidity based on LRTI hospitalization before age 2 years was 2.79 (95% CI, 2.66-2.93). The population-attributable risk of chronic respiratory morbidity due to any LRTI was approximately 25%, and that for respiratory syncytial virus LRTI was similar.

CONCLUSIONS

Hospitalization of young children for LRTIs is associated with two-fold increased risk of childhood chronic respiratory morbidity, demonstrating the ongoing impact of LRTI in infancy.

The relationship between respiratory syncytial virus and asthma

Asthma is a chronic inflammatory disease of the lung that is a leading cause of morbidity and mortality in children worldwide. Most infants who experience wheezing episodes also exhibit evidence of an ongoing respiratory viral infection. Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection in children and is a common cause of wheezing in infants and young children. In the past several decades, a number of studies have demonstrated a relationship between infants with severe RSV infections and the subsequent development of asthma later during childhood. This review provides an overview of data that suggests a severe RSV infection early in childhood is linked to development of asthma later in life. In addition, the current and potential future use of various animal models to gain additional insight into the relationship between RSV and asthma is discussed.

Increased risk of wheeze and decreased lung function after respiratory syncytial virus infection

Background

A relationship between hospitalization for respiratory syncytial virus (RSV) bronchiolitis and asthma development has been suggested in case-control studies.

Objective

The aim of this study was to assess the risk of current wheeze, asthma, and lung function at school age in infants previously hospitalized for RSV bronchiolitis compared to non-hospitalized children.

Methods

For this study, data from a prospective birth cohort of unselected, term-born infants (n = 553), of whom 4 (0.7%) were hospitalized for RSV bronchiolitis, and a prospective patient cohort of 155 term infants hospitalized for RSV bronchiolitis were used. Respiratory outcomes at age 6 in children hospitalized for RSV bronchiolitis were compared to non-hospitalized children.

Results

The risk of current wheeze was higher in hospitalized patients (n = 159) compared to non-hospitalized children (n = 549) (adjusted odds ratio (OR) 3.2 (95% CI 1.2–8.1). Similarly, the risk of current asthma, defined as a doctor’s diagnosis of asthma plus current symptoms or medication use, was higher in hospitalized patients (adjusted OR 3.1 (95% CI 1.3–7.5). Compared to non-hospitalized children, RSV bronchiolitis hospitalization was associated with lower lung function (mean difference FEV1% predicted −6.8 l (95% CI (−10.2 to −3.4).

Conclusions and Clinical Relevance

This is the first study showing that hospitalization for RSV bronchiolitis during infancy is associated with increased risk of wheezing, current asthma, and impaired lung function as compared to an unselected birth cohort at age 6.

Lack of long-term effects of high-dose inhaled beclomethasone for respiratory syncytial virus bronchiolitis: a randomized placebo-controlled trial

BACKGROUND

Previously, we showed that high-dose early initiated inhaled corticosteroids during respiratory syncytial virus bronchiolitis partially and transiently prevents subsequent recurrent wheeze. Here, we study treatment effect on lung function at age 6.

METHODS

This is a 6-year follow-up report of a randomized placebo-controlled trial, in which 185 infants hospitalized for respiratory syncytial virus bronchiolitis were treated with early initiated, high-dose inhaled beclomethasone (n = 86) or placebo (n = 99) for 3 months. The primary outcome was forced expiratory volume in 1 second as percentage predicted. Secondary outcomes were bronchial hyperresponsiveness, physician-diagnosed asthma, hay fever and eczema. Possible toxicity was assessed by linear growth measurements.

RESULTS

At age 6, no significant differences were found in mean forced expiratory volume in 1 second percentage predicted between beclomethasone-treated and placebo-treated patients (91.4 vs. 93.4, mean difference 2.05 (95% confidence interval: -1.98 to 6.08). The proportion of bronchial hyperresponsiveness, physician-diagnosed asthma, parent reported hay fever and eczema was comparable between groups. There were no differences in linear growth.

CONCLUSIONS

Early initiated prolonged treatment with high-dose inhaled beclomethasone during hospitalization for respiratory syncytial virus infection during infancy did not improve the long-term respiratory outcome, but was safe.

Respiratory syncytial virus--a comprehensive review

Respiratory syncytial virus (RSV) is amongst the most important pathogenic infections of childhood and is associated with significant morbidity and mortality. Although there have been extensive studies of epidemiology, clinical manifestations, diagnostic techniques, animal models and the immunobiology of infection, there is not yet a convincing and safe vaccine available. The major histopathologic characteristics of RSV infection are acute bronchiolitis, mucosal and submucosal edema, and luminal occlusion by cellular debris of sloughed epithelial cells mixed with macrophages, strands of fibrin, and some mucin. There is a single RSV serotype with two major antigenic subgroups, A and B. Strains of both subtypes often co-circulate, but usually one subtype predominates. In temperate climates, RSV infections reflect a distinct seasonality with onset in late fall or early winter. It is believed that most children will experience at least one RSV infection by the age of 2 years. There are several key animal models of RSV. These include a model in mice and, more importantly, a bovine model; the latter reflects distinct similarity to the human disease. Importantly, the prevalence of asthma is significantly higher amongst children who are hospitalized with RSV in infancy or early childhood. However, there have been only limited investigations of candidate genes that have the potential to explain this increase in susceptibility. An atopic predisposition appears to predispose to subsequent development of asthma and it is likely that subsequent development of asthma is secondary to the pathogenic inflammatory response involving cytokines, chemokines and their cognate receptors. Numerous approaches to the development of RSV vaccines are being evaluated, as are the use of newer antiviral agents to mitigate disease. There is also significant attention being placed on the potential impact of co-infection and defining the natural history of RSV. Clearly, more research is required to define the relationships between RSV bronchiolitis, other viral induced inflammatory responses, and asthma.

Association between respiratory syncytial virus hospitalizations in infants and respiratory sequelae: systematic review and meta-analysis

BACKGROUND

The association between hospitalization for respiratory syncytial virus (RSV) infection in infancy and asthma/wheezing in later life has long been studied. However, no published studies have combined systematic review and meta-analysis of existing evidence.

PURPOSE

To quantify the link between RSV hospitalization in early life and subsequent diagnosis of asthma.

METHOD

A systematic search was conducted using MEDLINE and EMBASE databases. Studies were selected for meta-analysis if they assessed the association between RSV-confirmed hospitalization for up to 3 years of age and asthma/wheezing later in life. Potential sources of heterogeneity were identified by stratified analysis.

RESULTS

Twenty articles representing 15 unique studies of 82,008 unique individuals (including 1533 with RSV-confirmed hospitalization) were selected for meta-analysis. Children who had RSV disease in early life had a higher incidence of asthma/wheezing in later life (odds ratio: 3.84; 95% confidence interval: 3.23-4.58). There was moderate heterogeneity between studies (I² = 45%). The association was found to decrease with age at follow-up, consistent with the findings of longitudinal studies. When age at follow-up was considered, heterogeneity was low (residual I² = 17%).

LIMITATIONS

Study quality was generally poor because randomization to hospitalization for RSV infection was not possible, appropriate blinding was rare and adjustment for confounding variables was not always appropriate.

CONCLUSIONS

The meta-analysis suggests an association between infant RSV hospitalization and respiratory morbidity that decreases with age. If the association is causal, the development of an effective vaccine against RSV could decrease the burden of asthma.

Viral infection of the lung: host response and sequelae

Because of its essential role in gas exchange and oxygen delivery, the lung has evolved a variety of strategies to control inflammation and maintain homeostasis. Invasion of the lung by pathogens (and in some instances exposure to certain noninfectious particulates) disrupts this equilibrium and triggers a cascade of events aimed at preventing or limiting colonization (and more importantly infection) by pathogenic microorganisms. In this review we focus on viral infection of the lung and summarize recent advances in our understanding of the triggering of innate and adaptive immune responses to viral respiratory tract infection, mechanisms of viral clearance, and the well-recognized consequences of acute viral infection complicating underlying lung diseases, such as asthma.

A novel influenza virus hemagglutinin-respiratory syncytial virus (RSV) fusion protein subunit vaccine against influenza and RSV

Influenza A virus and respiratory syncytial virus (RSV) cause substantial morbidity and mortality afflicting the ends of the age spectrum during the autumn through winter months in the United States. The benefit of vaccination against RSV and influenza using a subunit vaccine to enhance immunity and neutralizing antibody was investigated. Influenza virus hemagglutinin (HA) and RSV fusion (F) protein were tested as vaccine components alone and in combination to explore the adjuvant properties of RSV F protein on HA immunity. Mice vaccinated with HA and F exhibited robust immunity that, when challenged, had reduced viral burden for both influenza and RSV. These studies show an enhancing and cross-protective benefit of F protein for anti-HA immunity.