Hospitalization for RSV bronchiolitis before 12 months of age and subsequent asthma, atopy and wheeze: a longitudinal birth cohort study

Genotypic analysis of rhinovirus and human respiratory syncytial virus in sudden unexpected death in infancy cases at Tygerberg Hospital, Cape Town, South Africa

Infant mortality remains a major global concern. Sudden unexpected death in infancy (SUDI) is reported globally and an infant mortality rate of 23.129 per 1 000 live births has been reported in the Western Cape, South Africa, in 2024. Infections are often confirmed in SUDI cases admitted to the Tygerberg Medico-legal Mortuary in Cape Town, but molecular diversity in respiratory viruses is underreported. A total of 162 previously confirmed polymerase chain reaction (PCR)-positive trachea and / or lung samples from SUDI cases collected between 2015 and 2019 were retested for either rhinovirus or human respiratory syncytial virus (RSV). Sixty-four samples were positive for rhinovirus and 15 for RSV. Results from 5 of all positive samples were outside the PCR assay amplification limits determined by the cycle threshold (Ct) value and were excluded. Another 4 samples did not amplify, and the remaining 70 underwent subsequent sequencing, but successful sequences could only be obtained in 53 samples. All three rhinovirus (A, B and C) genotypes were identified, with RV-A most prevalent, followed by RV-C and RV-B. RSV-A and RSV-B were detected equally, and after amino acid alignment, 20 amino acid duplication and nine substitutions were found that confirmed two RSV-BA9 genotypes. This study describes the molecular and phylogenetic characterisation of specific respiratory viruses in SUDI cases in South Africa. However, the rapid decline in viral viability in post-mortem samples does not allow correlation between viral genotypes and cause of death or disease severity. Future prospective studies should therefore investigate temporality and associations between specific viral strains and clinical disease severity and mortality.

The Microbiome and Pulmonary Immune Function

In the last decade, the lung microbiome field has matured into a promising area of translational and clinical research due to emerging evidence indicating a role for respiratory microbiota in lung immunity and pathogenesis. Here, we review recent insights pertaining to the lung microbiome's relationship with pulmonary immune function. We discuss areas of future investigation that will be essential to the development of immunomodulatory therapies targeting the respiratory microbiome.

The Association Between Respiratory Viruses and Asthma Exacerbation in Children Visiting Pediatric Emergency Department: A Retrospective Cohort Study

Background/Objectives: Respiratory viral infections are a major cause of asthma exacerbations. However, studies examining the association between symptoms, signs, treatments, outcomes of asthma exacerbations, and various respiratory viruses in children are limited. This study aims to investigate the association between respiratory viral infections and clinical symptoms and signs, treatment, and hospital admission in children with asthma exacerbations visiting the pediatric emergency department. Methods: This study examined 395 children under 15 years of age who had a previous diagnosis of bronchial asthma, experienced asthma exacerbation, and visited an emergency center between 1 July 2015 and 30 June 2017. Among the 395 participants, respiratory virus polymerase chain reaction (PCR) was conducted in 96 patients (24.3%). The symptoms and signs of asthma exacerbation (dyspnea, tachypnea, chest retraction, wheezing, and gastrointestinal symptoms), treatment (oxygen supplementation and systemic steroid administration), symptom relief within 1 h, and hospital admission were analyzed. Results: Among the 96 patients who underwent respiratory virus PCR, at least one respiratory virus was detected in 72 (75.0%), and over two viruses were detected in 21 children (21.9%). Three common viruses were detected: rhinovirus in 59 (61.5%), adenovirus in 10 (10.4%), and respiratory syncytial virus (RSV) in nine children (9.4%). Rhinovirus infection was associated with tachypnea (adjusted odd ratio (aOR) 4.457, p = 0.007), chest retraction (aOR 3.142, p = 0.013), and systemic steroid administration (aOR 3.065, p = 0.034). Adenovirus infection was associated with oxygen supplementation via nasal cannula (aOR 5.297, p = 0.042). Conclusions: Rhinovirus was associated with tachypnea, chest retraction, and systemic steroid administration, while adenovirus was linked to oxygen supplementation in childhood asthma exacerbations. These findings will help clinicians to better observe asthma symptoms, select appropriate treatments, and improve outcomes for asthma exacerbations.

Economic and clinical burden associated with respiratory syncytial virus and impact of universal immunization with nirsevimab in Italy

Objectives

To describe the seasonal respiratory syncytial virus (RSV) burden in Italy considering the current prophylaxis strategy with palivizumab recommended only for high-risk infants (representing only 4.4% of an estimated birth cohort) and to evaluate the potential benefits of a new prophylaxis strategy targeting all infants with nirsevimab.

Methods

A static decision analytic model previously used in the US was adapted to evaluate the RSV-related health and cost outcomes associated with nirsevimab versus standard of care (SoC) for the prevention of RSV medically attended lower respiratory tract infections (RSV-MA-LRTIs). Monthly probabilities of RSV infections, health events, mortality, and complications associated with RSV infections were obtained from the literature. Costs associated with each event were obtained using the available literature and through real-world data analysis of National Hospital Discharge Records.

Results

For one RSV season, in the current SoC, the model estimated 216,100 RSV-MA-LRTIs, 15,121 associated complications, and 16 RSV-deaths-corresponding to an economic burden of approximately €50.5 million related to RSV-MA-LRTIs management, €10.9 million associated with potential complications due to RSV and €3 million in lost productivity due to RSV-deaths. Nirsevimab is expected to prevent 100,208 RSV-MA-LRTIs, 6,969 complications, and 6 deaths due to RSV infections, corresponding to an economic saving of about €23.3, €5, and €1.2 million, respectively.

Conclusion

Nirsevimab is a new prophylaxis strategy that helps to protect all infants against RSV disease and could substantially reduce the clinical and economic burden of RSV in Italy in infants experiencing their first RSV season.

Strain-specific differences in reovirus infection of murine macrophages segregate with polymorphisms in viral outer-capsid protein σ3

Mammalian orthoreovirus (reovirus) strains type 1 Lang (T1L) and type 3 Dearing-RV (T3D-RV) infect the intestine in mice but differ in the induction of inflammatory responses. T1L infection is associated with the blockade of oral immunological tolerance to newly introduced dietary antigens, whereas T3D-RV is not. T1L infection leads to an increase in infiltrating phagocytes, including macrophages, in gut-associated lymphoid tissues that are not observed in T3D-RV infection. However, the function of macrophages in reovirus intestinal infection is unknown. Using cells sorted from infected intestinal tissue and primary cultures of bone-marrow-derived macrophages (BMDMs), we discovered that T1L infects macrophages more efficiently than T3D-RV. Analysis of T1L × T3D-RV reassortant viruses revealed that the viral S4 gene segment, which encodes outer-capsid protein σ3, is responsible for strain-specific differences in infection of BMDMs. Differences in the binding of T1L and T3D-RV to BMDMs also segregated with the σ3-encoding S4 gene. Paired immunoglobulin-like receptor B (PirB), which serves as a receptor for reovirus, is expressed on macrophages and engages σ3. We found that PirB-specific antibody blocks T1L binding to BMDMs and that T1L binding to PirB-/- BMDMs is significantly diminished. Collectively, our data suggest that reovirus T1L infection of macrophages is dependent on engagement of PirB by viral outer-capsid protein σ3. These findings raise the possibility that macrophages function in the innate immune response to reovirus infection that blocks immunological tolerance to new food antigens.IMPORTANCEMammalian orthoreovirus (reovirus) infects humans throughout their lifespan and has been linked to celiac disease (CeD). CeD is caused by a loss of oral immunological tolerance (LOT) to dietary gluten and leads to intestinal inflammation following gluten ingestion, which worsens with prolonged exposure and can cause malnutrition. There are limited treatment options for CeD. While there are genetic risk factors associated with the illness, triggers for disease onset are not completely understood. Enteric viruses, including reovirus, have been linked to CeD induction. We found that a reovirus strain associated with oral immunological tolerance blockade infects macrophages by virtue of its capacity to bind macrophage receptor PirB. These data contribute to an understanding of the innate immune response elicited by reovirus, which may shed light on how viruses trigger LOT and inform the development of CeD vaccines and therapeutic agents.

Epidemiology of respiratory syncytial virus in hospitalized children over a 9-year period and preventive strategy impact

Background: Respiratory Syncytial Virus (RSV) is the primary cause of respiratory infections and hospitalizations in young children globally, leading to substantial disease burden and mortality. The aim of the present study was to review and provide updates on how the SARS-CoV-2 pandemic have significantly influenced RSV epidemiology on hospitalized children due to RSV infection. A potential impact of the available preventive strategies on the same population were provided. Methods: All children aged 0-6 years hospitalized at Meyer Children's Hospital IRCCS for RSV infection from September 2014 to March 2023 were retrospectively recorded. Seasonal trends before and after SARS-CoV-2 pandemic, age distribution, ICU admission and co-infections, comorbidities and prematurity were retrieved. Predictions on the number of hospitalizations avoided by the deployment of different preventive strategies were provided. Results: A total of 1,262 children with RSV infection were included in the study. The 70% of them had less than 1 year-of-age at the moment of hospitalization and almost 50% less than 3 months. In the post-pandemic seasons, a 317% increase in the number of hospitalizations was recorded with a significant increase in older children compared to the pre-pandemic seasons. ICU support was required for 22% of children, the majority of whom were under 3 months of age. Almost 16% of hospitalized children were born preterm and only 27% of hospitalized children had prior comorbidities. The rate of comorbidities among RSV hospitalized children increased with age. Nirsevimab prophylaxis could have prevented more than 46% of hospitalizations in this cohort. A preventive strategy addressing also children aged 7 months to 6 years of age with co-existing comorbidities would increase that rate above 57%. Discussion: The identification of RSV hospitalization-related features is informing the decision-maker for the deployment of the wisest preventive approach on a population scale.

Mutations in the F protein of the live-attenuated respiratory syncytial virus vaccine candidate ΔNS2/Δ1313/I1314L increase the stability of infectivity and content of prefusion F protein

Respiratory syncytial virus (RSV) is the leading viral cause of bronchiolitis and pneumonia in infants and toddlers, but there currently is no licensed pediatric vaccine. A leading vaccine candidate that has been evaluated for intranasal immunization in a recently completed phase 1/2 clinical trial is an attenuated version of RSV strain A2 called RSV/ΔNS2/Δ1313/I1314L (hereafter called ΔNS2). ΔNS2 is attenuated by deletion of the interferon antagonist NS2 gene and introduction into the L polymerase protein gene of a codon deletion (Δ1313) that confers temperature-sensitivity and is stabilized by a missense mutation (I1314L). Previously, introduction of four amino acid changes derived from a second RSV strain "line 19" (I79M, K191R, T357K, N371Y) into the F protein of strain A2 increased the stability of infectivity and the proportion of F protein in the highly immunogenic pre-fusion (pre-F) conformation. In the present study, these four "line 19" assignments were introduced into the ΔNS2 candidate, creating ΔNS2-L19F-4M. During in vitro growth in Vero cells, ΔNS2-L19F-4M had growth kinetics and peak titer similar to the ΔNS2 parent. ΔNS2-L19F-4M exhibited an enhanced proportion of pre-F protein, with a ratio of pre-F/total F that was 4.5- to 5.0-fold higher than that of the ΔNS2 parent. The stability of infectivity during incubation at 4°C, 25°C, 32°C and 37°C was greater for ΔNS2-L19F-4M; for example, after 28 days at 32°C, its titer was 100-fold greater than ΔNS2. ΔNS2-L19F-4M exhibited similar levels of replication in human airway epithelial (HAE) cells as ΔNS2. The four "line 19" F mutations were genetically stable during 10 rounds of serial passage in Vero cells. In African green monkeys, ΔNS2-L19F-4M and ΔNS2 had similar growth kinetics, peak titer, and immunogenicity. These results suggest that ΔNS2-L19F-4M is an improved live attenuated vaccine candidate whose enhanced stability may simplify its manufacture, storage and distribution, which merits further evaluation in a clinical trial in humans.

Asthma-community acquired pneumonia co-diagnosis in children: a scoping review

OBJECTIVE

This scoping review investigated the existing literature and identified the evidence gaps related to diagnosis and management in children aged 2-18 years presenting to hospitals with a co-diagnosis of asthma and community-acquired pneumonia.

DATA SOURCES

We designed a scoping review following Arksey and O'Malley's scoping review framework and PRISMA extension for a scoping review. We searched literature using five electronic databases: PubMed, CINAHL, Scopus, Web of Science, and Embase from 2003 to June 2023.

RESULTS

A total of 1599 abstracts with titles were screened and 12 abstracts were selected for full review. Separate guidelines including Modified Global Initiative for Asthma (GINA) guidelines; modified Integrated Management of Childhood Illness (IMCI) guidelines; and a consensus guideline developed by the Pediatric Infectious Diseases Society (PIDS) and Infectious Diseases Society of America (IDSA) were used for diagnosing asthma and CAP individually. Chest X-rays were used in 83.3% (10/12) of studies to establish the co-diagnosis of asthma-CAP in children. Variations were observed in using different laboratory investigations across the studies. Infectious etiologies were detected in five (41.7%) studies. In 75% (9/12) of studies, children with asthma-CAP co-diagnosis were treated with antimicrobials, however, bacterial etiology was not reported in 44.4% (4/9) of the studies.

CONCLUSIONS

Our scoping review suggests that chest X-rays are commonly used to establish the co-diagnosis of asthma-CAP and antibiotics are often used without laboratory confirmation of a bacterial etiology. Clinical practice guidelines for the management of asthma and pneumonia in children who present with co-diagnosis may standardize clinical care and reduce variation.

Respiratory and Gut Microbiome Modification during Respiratory Syncytial Virus Infection: A Systematic Review

BACKGROUND

Respiratory syncytial virus (RSV) infection is a major cause of lower respiratory tract infection, especially in infants, and increases the risk of recurrent wheezing and asthma. Recently, researchers have proposed a possible association between respiratory diseases and microbiome alterations. However, this connection has not been fully established. Herein, we conducted a systematic literature review to evaluate the reported evidence of microbiome alterations in patients with RSV infection.

METHODS

The systematic literature review on the association between RSV and microbiome in humans was conducted by searching PubMed, EMBASE, Scopus, and CINAHL from 2012 until February 2022. The results were analyzed qualitatively, focusing on the relationship between microbiome and RSV infection with available key microbiome-related parameters.

RESULTS

In the 405 articles identified by searching databases, 12 (Respiratory tract: 9, Gut: 2, Both: 1) articles in line with the research aims were eligible for this qualitative review. The types of samples for the respiratory tract microbiome and the sequencing methods utilized varied from study to study. This review revealed that the overall microbial composition in both the respiratory tract and gut in RSV-infected patients was different from that in healthy controls. Our generated results demonstrated an increase in the abundance of Haemophilus and Streptococcus, which could contribute to the distinctive separation based on the beta diversity in the respiratory tract.

CONCLUSIONS

The respiratory tract and gut microbiome changed in patients with RSV infection. Further research with a well-organized longitudinal design is warranted to clarify the impact of microbiome alterations on disease pathogenesis.

Histone acetylation regulates ORMDL3 expression-mediated NLRP3 inflammasome overexpression during RSV-allergic exacerbation mice

Whether respiratory syncytial virus (RSV) infection in early life may induce orosomucoid 1-like protein 3 (ORMDL3) and lead to NOD-like receptor protein 3 (NLRP3) inflammasome overexpression in asthma, which could be alleviated by the inhibition of HAT p300. First, we explored the relationship between RSV, ORMDL3, and recurrent wheezing in the future through clinical data of infants with RSV-induced bronchiolitis. Then, we used bronchial epithelium transformed with Ad12-SV40 2B (BEAS-2B) and an asthmatic mouse model of repeated RSV infection and OVA sensitization and challenge (rRSV + OVA) in early life to assess the effects of ORMDL3 on NLRP3 inflammasome and that of histone acetylation on ORMDL3 regulation. ORMDL3 overexpression is the independent risk factor of recurrent wheezing in RSV-bronchiolitis follow-up. In BEAS-2B, ORMDL3-induced NLRP3 inflammasome expression. BEAS-2B infected by RSV resulted in overexpression of ORMDL3 and NLRP3 inflammasome and histone hyperacetylation, while ORMDL3-small interfering RNA and C646 interfered could decrease NLRP3 inflammasome. ORMDL3 overexpression in mouse lung increased NLRP3 inflammasome. The expression of ORMDL3 and NLRP3 inflammasome significantly increased, with histone hyperacetylation in the lung in rRSV + OVA mice. p300 and acetylH3 bound to ORMDL3 promoter. In C646 + rRSV + OVA mice, C646 alleviated lung inflammation and overexpression of ORMDL3 and NLRP3 inflammasome. RSV activated ORMDL3 overexpression through histone hyperacetylation and induced NLRP3 inflammasome expression.

Early-immune development in asthma: A review of the literature

This review presents a comprehensive examination of the various factors contributing to the immunopathogenesis of asthma from the prenatal to preschool period. We focus on the contributions of genetic and environmental components as well as the role of the nasal and gut microbiome on immune development. Predisposing genetic factors, including inherited genes associated with increased susceptibility to asthma, are discussed alongside environmental factors such as respiratory viruses and pollutant exposure, which can trigger or exacerbate asthma symptoms. Furthermore, the intricate interplay between the nasal and gut microbiome and the immune system is explored, emphasizing their influence on allergic immune development and response to environmental stimuli. This body of literature underscores the necessity of a comprehensive approach to comprehend and manage asthma, as it emphasizes the interactions of multiple factors in immune development and disease progression.

Chitinase 3-like 1 plays a pivotal role in airway response of RSV infection via regulating DC functional transition

BACKGROUND

Dendritic cells (DCs) contribute to immune imbalance and airway hyperresponsiveness (AHR) induced by respiratory syncytial virus (RSV). The aim of present study was to explore the mechanism of RSV regulating naive T cell differentiation through DCs.

METHODS

We generated a Lentivirus shRNA expression vector to knock down CHI3L1 in mouse lungs and bone marrow-derived dendritic cells (BMDCs). Then we investigated the effect of CHI3L1 knockdown on MAPK/ERK pathway, PI3K/AKT pathway, mature DCs represented by molecular markers, naive T cell differentiation and related cytokine expression in vitro and in vivo models of RSV.

RESULTS

RSV elevated CHI3L1 expression in lung DCs and BMDCs. Knockdown of CHI3L1 impeded RSV-induced activation of MAPK/ERK and PI3K/AKT signaling pathways, attenuated CD86 and OX40L expression in mature DCs, reduced the proportion of Th2 and Th17 cells, and increased the proportion of Treg cells. In addition, by blocking CHI3L1, RSV-infected mice shown relief of airway resistance, the downregulation of Th2/Th17 like cytokines IL-4, IL-13 and IL-17 levels, and the upregulation of IL-10.

CONCLUSION

Our data show that CHI3L1 promotes RSV induced immune imbalance and airway hyperresponsiveness by regulating the functional transformation of DCs.

Are Babies Born Preterm High-Risk Asthma Candidates?

Among preterm infants, the risk of developing asthma is a matter of debate. This review discusses the state of the art of poorly understood prematurity-associated asthma. Impaired pulmonary function is common in children born prematurely. Preterm infants are prone to developing viral respiratory tract infections, bronchiolitis in the first year of life, and recurrent viral wheezing in preschool age. All of these conditions may precede asthma development. We also discuss the role of both atopic sensitization and intestinal microbiome and, consequently, immune maturation. Diet and pollution have been considered to better understand how prematurity could be associated with asthma. Understanding the effect of factors involved in asthma onset may pave the way to improve the prediction of this asthma phenotype.

Case-control study of exclusive breast feeding and severe bronchiolitis in the United States

BACKGROUND

Bronchiolitis is a major cause of infant illness, with few known modifiable risk factors. Breast feeding may reduce risk of severe bronchiolitis, but the association of exclusive vs. partial breast feeding with severe bronchiolitis is unclear.

OBJECTIVE

To estimate the association of exclusive vs. partial breast feeding during ages 0-2.9 months with bronchiolitis hospitalisation during infancy.

METHODS

We conducted a case-control study as a secondary analysis of two prospective US cohorts in the Multicenter Airway Research Collaboration. Cases were enrolled in a 17-centre study of infants hospitalised for bronchiolitis during 2011-2014 (n = 921). Controls were enrolled in a five-centre study of healthy infants during 2013-2014 and 2017 (n = 719). Breast feeding history during ages 0-2.9 months was collected by parent interview. Among breastfed infants, the association of exclusive vs. partial breast feeding with odds of bronchiolitis hospitalisation was estimated using a multivariable logistic regression model adjusted for demographic variables, parental asthma history, and early-life exposures. As a secondary analysis, we estimated the associations of exclusive, predominant, and occasional breast feeding vs. no breast feeding with the odds of bronchiolitis hospitalisation.

RESULTS

Among 1640 infants, the prevalence of exclusive breast feeding was 187/921 (20.3%) among cases and 275/719 (38.3%) among controls. Exclusive vs. partial breast feeding was associated with 48% reduced odds of bronchiolitis hospitalisation (adjusted odds ratio [OR] 0.52, 95% confidence interval [CI] 0.39, 0.69). In the secondary analysis, exclusive vs. no breast feeding was associated with 58% reduced odds of bronchiolitis hospitalisation (OR 0.42, 95% CI 0.23, 0.77), whereas predominant breast feeding (OR 0.77, 95% CI 0.37, 1.57) and occasional breast feeding (OR 0.98, 95% CI 0.57, 1.69) were not associated with meaningfully reduced odds of bronchiolitis hospitalisation.

CONCLUSION

Exclusive breast feeding had a strong protective association against bronchiolitis hospitalisation.

Pulmonary sequelae in 2-year-old children after hospitalisation for respiratory syncytial virus lower respiratory tract infection during infancy: an observational study

BACKGROUND

Respiratory syncytial virus (RSV) is the most common cause of hospitalisation for lower respiratory tract infection (LRTI) in children. RSV LRTI during early childhood may increase susceptibility to recurrent wheezing and asthma.

RESEARCH QUESTION

The aim of this study was to describe the pulmonary sequelae at 1 and 2 years of age following RSV LRTI hospitalisation during the first year of life in term infants.

STUDY DESIGN AND METHODS

A longitudinal case-control study was undertaken from April 2016 to December 2019. Cases constituted children hospitalised with PCR-confirmed RSV LRTI during infancy and controls were children not previously hospitalised with LRTI. A questionnaire detailing environmental and medical history, as well as a modified International Study of Asthma and Allergies (ISAAC) questionnaire, was administered, and pulmonary function testing, including oscillometry, tidal breath flow-volume loops and multiple breath wash-out, was performed, at one and two years of age.

RESULTS

One (n=308) and two-year-old (n=214) cases were more likely than one (n=292) and two-year-old (n=209) controls to have experienced clinical pulmonary symptoms, including wheezing ((55% vs 24%; p<0.001) and (61% vs 16%; p<0.001)), received treatment for wheezing ((17 vs 8%; p<0.001) and (51 vs 6%; p<0.001)) and had any admissions for wheezing ((31 vs 6%; p<0.001) and (46 vs 1.4%; p<0.001)) or any LRTI ((24 vs 2%; p<0.001) and (32 vs 1.4%; p<0.001)), after the initial RSV hospitalisation. RSV LRTI during infancy was associated with an increase in airway resistance by two years (22.46 vs 20.76 hPa.s.l^-1 (p=0.022)), along with a decrease in compliance at both one (-4.61 vs -3.09 hPa.s/l (p<0.001)) and two years (-0.99 vs 0.33 hPa.s/l¹ (p<0.001)). There was an increased work of breathing at one year, but this was no longer present at two years.

INTERPRETATION

RSV LRTI during infancy in cases was associated with more clinical and pulmonary function sequelae through to two years of age.

Blood eosinophils during bronchiolitis: Associations with atopy, asthma and lung function in young adults

AIM

To study if blood eosinophils during bronchiolitis were associated with atopy, asthma and lung function in young adults and if these associations differed between respiratory syncytial virus (RSV) bronchiolitis and non-RSV bronchiolitis.

METHODS

This historical cohort enrolled 225 subjects. Blood eosinophils were measured during bronchiolitis in infancy, and the subjects were invited to a follow-up at 17-20 years of age including questionnaires for asthma and examinations of lung function and atopy.

RESULTS

The level of eosinophils was positively associated with subsequent atopy in the unadjusted analysis, but not in the adjusted analysis, and not with asthma. There was a negative association between the level of eosinophils and forced vital capacity (FVC) (-0.11; -0.19, -0.02) and forced expiratory volume in first second (FEV₁ ) (-0.12; -0.21, -0.03) (regression coefficient; 95% confidence interval). The non-RSV group had higher levels of eosinophils during bronchiolitis, but there was no interaction between the level of eosinophils and RSV status for any outcome.

CONCLUSIONS

The level of eosinophils during bronchiolitis was negatively associated with lung function in young adult age, but we found no associations with atopy or asthma. These associations were not different after RSV bronchiolitis compared to non-RSV bronchiolitis.

Respiratory Syncytial Virus-Specific Antibodies and Atopic Diseases in Children: A 10-Year Follow-Up

BACKGROUND

Respiratory syncytial virus (RSV) stimulates the production of specific immunoglobulin (Ig) E and IgG4 antibodies as a hallmark of the Th2 immune response. In this paper, we evaluated the occurrence of atopic diseases in 10-year-old children who were positive for RSV-specific IgG antibodies during infancy.

METHODS

The prospective follow-up of 72 children included a physical examination, an International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire and the determination of RSV-specific antibodies and total and allergen-specific IgE.

RESULTS

Children with asthma had their first wheezing episode at a younger age (χ2 8.097, df = 1, p = 0.004). RSV-specific IgG4 levels at year one were positively correlated with atopic dermatitis (AD) (tau_b = 0.211, p = 0.049) and current AD (tau_b = 0.269, p = 0.012); and RSV-specific IgE levels were positively correlated with allergic rhinitis (AR) (tau_b = 0.290, p = 0.012) and current AR (tau_b = 0.260, p = 0.025). Positive RSV-specific IgE at the age of one increased the chances of asthma occurrence by 5.94 (OR = 5.94, 95% CI = 1.05-33.64; p = 0.044) and the chances of AR by more than 15 times (OR = 15.03, 95% CI = 2.08-108.72; p = 0.007). A positive family history of atopy increased the chances of asthma occurrence by 5.49 times (OR = 5.49, 95% CI = 1.01-30.07; p = 0.049), and a longer duration of exclusive breastfeeding lowered that chance (OR = 0.63, 95% CI = 0.45-0.89; p = 0.008). Prenatal smoking increased the chances of AR occurrence by 7.63 times (OR = 7.63, 95% CI = 1.59-36.53; p = 0.011).

CONCLUSION

RSV-specific IgE and RSV-specific IgG4 antibodies could be risk markers for the development of atopic diseases in children.

The Long-Term Healthcare Utilization and Economic Burden of RSV Infection in Children ≤5 Years in Japan: Propensity Score Matched Cohort Study

BACKGROUND

The objective of this study was to estimate the long-term healthcare utilization and cost burden of RSV by chronological age of diagnosis (Year 1, Year 2 and Years 3-5 cohorts) as well as by gestational age at birth in Japan.

METHODS

The JMDC database was used to retrospectively identify RSV and control patients between February 1, 2011 and January 31, 2016 and follow them through December 31, 2017. Infants with RSV infection (n = 9028 in Year 1; n = 4929 in Year 2; n = 2004 in Years 3-5) were matched to controls (n = 17,886; n = 9351; n = 3655, respectively) based on gestational age and year and quarter of birth; controls were assigned the index date (ie, diagnosis) of their respective match. Covariate-balancing propensity score weights were employed adjusting for remaining imbalances between cohorts. The main outcomes were average cumulative rates for all-cause, asthma/wheezing, and respiratory-related hospitalizations, physician and urgent care/emergency visits and associated costs (reported as 2018 ¥JPY) over 36-months of follow-up since index.

RESULTS

Healthcare utilization was significantly higher among RSV cases for most comparisons. All-cause average differential cost burden was higher for RSV, compared to controls, among the following cohorts: Year 1 full-term (¥277,727); Year 2 preterm (¥530,302), late preterm (¥270,797), full-term (¥238,832); Years 3-5 preterm (¥110,057), late preterm (¥486,670), full-term (¥289,986). While all-cause costs were similar for preterm and late preterm children in the Year 1 cohort, respiratory- and asthma/wheezing-related attributable costs were substantially higher for RSV.

CONCLUSION

RSV infection had a significant long-term health and economic burden among children infected during their first year of life and later in life. Study findings have import for prevention strategies, currently directed at maternal immunization and monoclonal antibodies for preventing primary RSV infections in the first six months of life and beyond but also for older age not targeted currently.

Proteomics endotyping of infants with severe bronchiolitis and risk of childhood asthma

BACKGROUND

Bronchiolitis is the leading cause of hospitalization in U.S. infants and a major risk factor for childhood asthma. Growing evidence supports clinical heterogeneity within bronchiolitis. We aimed to identify endotypes of infant bronchiolitis by integrating clinical, virus, and serum proteome data, and examine their relationships with asthma development.

METHODS

This is a multicenter prospective cohort study of infants hospitalized for physician-diagnosis of bronchiolitis. We identified bronchiolitis endotypes by applying unsupervised machine learning (clustering) approaches to integrated clinical, virus (respiratory syncytial virus [RSV], rhinovirus [RV]), and serum proteome data measured at hospitalization. We then examined their longitudinal association with the risk for developing asthma by age 6 years.

RESULTS

In 140 infants hospitalized with bronchiolitis, we identified three endotypes: (1) clinicalatopic virusRV proteomeNFκB-dysregulated , (2) clinicalnon-atopic virusRSV/RV proteomeTNF-dysregulated , and (3) clinicalclassic virusRSV proteomeNFκB/TNF-regulated endotypes. Endotype 1 infants were characterized by high proportion of IgE sensitization and RV infection. These endotype 1 infants also had dysregulated NFκB pathways (FDR < 0.001) and significantly higher risks for developing asthma (53% vs. 22%; adjOR 4.04; 95% CI, 1.49-11.0; p = 0.006), compared with endotype 3 (clinically resembling "classic" bronchiolitis). Likewise, endotype 2 infants were characterized by low proportion of IgE sensitization and high proportion of RSV or RV infection. These endotype 2 infants had dysregulated tumor necrosis factor (TNF)-mediated signaling pathway (FDR <0.001) and significantly higher risks for developing asthma (44% vs. 22%; adjOR 2.71; 95% CI, 1.03-7.11, p = 0.04).

CONCLUSION

In this multicenter cohort, integrated clustering of clinical, virus, and proteome data identified biologically distinct endotypes of bronchiolitis that have differential risks of asthma development.

Identification of potential immune/diagnosis related gene-immunocyte subtype networks in extracellular immune response to respiratory syncytial virus infection

INTRODUCTION

Respiratory syncytial virus (RSV) is one of the important pathogenic agents of pediatric respiratory tract infection. Weighted gene co-expression network analysis (WGCNA) is used to study autoimmune diseases, which can find potential hub genes. The diagnostic model based on hub genes and machine learning makes it possible to diagnose the extracellular immune response to RSV infection early.

OBJECTIVE

The aim of the present study was to identify potential immune, diagnose and treatment related genes expressed in RSV-infected cells.

METHODS

Firstly, gene expression data were downloaded from the Gene Expression Omnibus (GEO) to identify differentially expressed genes (DEGs). Secondly, WGCNA was performed based on DEGs to obtain hub genes related to immunity score. Thirdly, protein-protein interaction (PPI) and the immune infiltration analysis of hub immune related genes were performed. Finally, diagnostic and immune related genes were identified by machine learning, followed by functional analysis.

RESULTS

Totally, 2063 DEGs were identified in the extracellular immune response to RSV infection. Among which, 10 key immune and diagnosis related genes were identified, including ITGA2B, GP9, ITGB3, SELP, PPBP, MPL, CXCL8, NFE2, PTGS1 and LY6G6F. Several immune/diagnosis related gene-immunocyte subtype networks were identified, such as CXCL8-Type 17 T helper cell, LY6G6F-CD56 bright natural killer cell, PPBP-activated CD4 T cell/T follicular helper cell, NFE2/PTGS1/SELP-activated dendritic cell, GP9/ITGA2B/MPL-activated CD8 T cell. ITGB3, MPL and PTGS1 could be considered as therapeutic targets. Some significantly enriched signaling pathways were identified, including hematopoietic cell lineage (involving GP9 and ITGA2B), cytokine-cytokine receptor interaction (involving MPL), chemokine signaling pathway (involving PPBP) and arachidonic acid metabolism (involving PTGS1).

CONCLUSIONS

The 10-immune related gene signature may be used as potential diagnostic markers for the extracellular immune response to RSV infection, which may provide a new field in searching for diagnostic and therapeutic molecules in the extracellular immune response to RSV infection.

The clinical impact of multiple prevention strategies for respiratory syncytial virus infections in infants and high-risk toddlers in the United States

BACKGROUND

Respiratory syncytial virus (RSV) remains a leading cause of medically-attended acute respiratory infection in infants and children. With multiple preventative interventions under development, accurate estimates of health care resource utilization are essential for policy decision making.

METHODS

We developed a literature-based decision-tree model that estimated annual medically-attended RSV (MA-RSV) lower respiratory tract infection (LRTI) and non-LRTI episodes in the US for all infants and for high-risk toddlers. The model accounted for the gestational age and birth-month of infants, and the seasonal variation in RSV incidence. The impact of no prophylaxis, palivizumab, maternal vaccine, and long-acting monoclonal antibody (mAb) interventions was estimated.

RESULTS

We estimated 1.23 million (range: 0.96 million-1.40 million) annual MA-RSV LRTI/non-LRTI episodes comprised of 1.19 million (range: 0.93 million-1.36 million) emergency department (ED) and outpatient visits, and 39,040 (range: 32,726-45,851) hospitalizations. Outpatient and ED visits were comprised of 586,034 (range: 430,595-718,868) LRTIs and 608,733 (range: 495,705-644,658) non-LRTIs. The long-acting mAb intervention resulted in the greatest number of averted outpatient and ED episodes (310,997 [53%] LRTIs; 284,305 [47%] non-LRTIs) and hospitalizations (21,845 [56%]). Full-term infants constitute the highest proportion of episodes across all interventions.

CONCLUSIONS

MA-RSV disease is substantial in infants and high-risk toddlers. Long-acting mAbs are most effective at reducing the number of MA-RSV LRTI/non-LRTI episodes, and the only intervention that prevents disease in older infants (≥6 months old).

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.

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 [I 2 = 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.

Immune determinants of chronic sequelae after respiratory viral infection

The acute effects of various respiratory viral infections have been well studied, with extensive characterization of the clinical presentation as well as viral pathogenesis and host responses. However, over the course of the recent COVID-19 pandemic, the incidence and prevalence of chronic sequelae after acute viral infections have become increasingly appreciated as a serious health concern. Post-acute sequelae of COVID-19, alternatively described as “long COVID-19,” are characterized by symptoms that persist for longer than 28 days after recovery from acute illness. Although there exists substantial heterogeneity in the nature of the observed sequelae, this phenomenon has also been observed in the context of other respiratory viral infections including influenza virus, respiratory syncytial virus, rhinovirus, severe acute respiratory syndrome coronavirus, and Middle Eastern respiratory syndrome coronavirus. In this Review, we discuss the various sequelae observed following important human respiratory viral pathogens and our current understanding of the immunological mechanisms underlying the failure of restoration of homeostasis in the lung.

Risk of Developing Asthma After Lower Respiratory Tract Infections with Respiratory Syncytial Virus During Childhood

Background: Recent studies indicate causal relationship between infection by respiratory syncytial virus (RSV) and bronchial asthma. We evaluated the incidence of bronchial asthma in children with RSV positive infection early in their childhood in a nation-wide cohort study. Methods: Children (aged between one month and 15 years) were evaluated for the presence of RSV infection when they presented with one or more acute respiratory tract infection symptoms (fever, cough, cold and wheezing) in a major tertiary care hospital in the Kingdom of Bahrain during a period of seven years. RSV detection was done using nasopharyngeal secretion (NPS) samples by direct antigen detection immunofluorescence technique. Number of children who were later diagnosed with asthma was recorded. Serum IgE levels were estimated. Risk of developing bronchial asthma is represented using relative risk (RR) [95% CI]. Children with asthma without prior RSV infection from the same population formed the historical control. Results: A total of 3782 children diagnosed with respiratory tract infection were recruited. We observed that RSV infection at younger age (during infancy) and severe infection were significantly associated with asthmatic episodes RR [95% CI]: 7 [5.5, 8.2]. Additionally, asthmatics with prior RSV infection had significantly higher total IgE levels (167 ± 37 IU/ml) compared to those without RSV infection (92 ±17 IU/ml). Mean (SD) age of children developing asthma with prior RSV infection was 0.7 (0.42) years compared to the historical control [6.8 (3.8) years] and was statistically significant. Conclusion: Infants with RSV infection have an increased risk of developing bronchial asthma later in the childhood. The more severe the RSV infection, the greater is the severity of bronchial asthma as indicted by serum IgE levels. Asthma in children with RSV infection occurs at much younger age compared to those without RSV infection.

Moderate-to-severe lower respiratory tract infection in early life is associated with increased risk of polysensitization and atopic dermatitis: Findings from the CHILD Study

Background

Respiratory infections in infancy are associated with the development of allergic asthma and atopy. Delineating whether symptomatic infections are a marker of atopic predisposition or contribute to atopic development is important for preventive strategies. We hypothesized that early, severe lower respiratory tract infections (LRTIs) may be a risk factor for the development of atopic disease.

Objective

Our aim was to determine whether clinically defined, moderate-to-severe LRTIs in infancy are associated with the development of atopic dermatitis and allergic sensitization at preschool age.

Methods

LRTI timing and severity in the first 18 months of life was defined by using the Canadian Healthy Infant Longitudinal Development study questionnaires. Polysensitization and atopic dermatitis were determined by standardized skin prick testing and structured clinical assessments. Longitudinal associations between LRTI severity and clinical outcomes at ages 3 years and 5 years were determined by adjusted repeated measures generalized estimation equations.

Results

Moderate-to-severe LRTIs were associated with increased odds of polysensitization (odds ratio = 1.91 [95% CI = 1.16-3.15]; P = .014) and atopic dermatitis (odds ratio = 2.19 [95% CI 1.41-3.39]; P < .001) as compared with the odds in children with no history of LRTI in the first 18 months of life. The association between moderate-to-severe LRTI and polysensitization or atopic dermatitis remained robust after adjusting for sex; study site; breast-feeding duration; and mother, father, or both-parent atopy or asthma.

Conclusions

These results highlight severe infant LRTI as an important risk factor for allergic and atopic disease (ie, polysensitization and atopic dermatitis), and they suggest that this risk is independent of maternal in utero environment, both-parent history of asthma, and both-parent genetic predisposition.

Early-Life Lung and Gut Microbiota Development and Respiratory Syncytial Virus Infection

Several environmental factors can influence the development and establishment of the early-life microbiota. For example, exposure to different environmental factors from birth to childhood will shape the lung and gut microbiota and the development of the immune system, which will impact respiratory tract infection and widespread disease occurrence during infancy and later in life. Respiratory syncytial virus (RSV) infects most infants by the age of two and is the primary cause of bronchiolitis in children worldwide. Approximately a third of infants hospitalized with bronchiolitis develop asthma later in life. However, it is unclear what factors increase susceptibility to severe RSV-bronchiolitis and the subsequent asthma development. In recent years, the role of the gut and lung microbiota in airway diseases has received increased interest, and more studies have focused on this field. Different epidemiological studies and experimental animal models have associated early-life gut microbiota dysbiosis with an increased risk of lung disease later in life. This work will review published evidence that correlated environmental factors that affect the early-life microbiota composition and their role in developing severe RSV infection.

Recurrent Wheeze Exacerbations Following Acute Bronchiolitis-A Machine Learning Approach

Introduction: Acute bronchiolitis is one of the most common respiratory infections in infancy. Although most infants with bronchiolitis do not get hospitalized, infants with hospitalized bronchiolitis are more likely to develop wheeze exacerbations during the first years of life. The objective of this prospective cohort study was to develop machine learning models to predict incidence and persistence of wheeze exacerbations following the first hospitalized episode of acute bronchiolitis. Methods: One hundred thirty-one otherwise healthy term infants hospitalized with the first episode of bronchiolitis at a tertiary pediatric hospital in Athens, Greece, and 73 age-matched controls were recruited. All patients/controls were followed up for 3 years with 6-monthly telephone reviews. Through principal component analysis (PCA), a cluster model was used to describe main outcomes. Associations between virus type and the clusters and between virus type and other clinical characteristics and demographic data were identified. Through random forest classification, a prediction model with smallest classification error was identified. Primary outcomes included the incidence and the number of caregiver-reported wheeze exacerbations. Results: PCA identified 2 clusters of the outcome measures (Cluster 1 and Cluster 2) that were significantly associated with the number of recurrent wheeze episodes over 3-years of follow-up (Chi-Squared, p < 0.001). Cluster 1 included infants who presented higher number of wheeze exacerbations over follow-up time. Rhinovirus (RV) detection was more common in Cluster 1 and was more strongly associated with clinical severity on admission (p < 0.01). A prediction model based on virus type and clinical severity could predict Cluster 1 with an overall error 0.1145 (sensitivity 75.56% and specificity 91.86%). Conclusion: A prediction model based on virus type and clinical severity of first hospitalized episode of bronchiolitis could predict sensitively the incidence and persistence of wheeze exacerbations during a 3-year follow-up. Virus type (RV) was the strongest predictor.

The role of respiratory syncytial virus- and rhinovirus-induced bronchiolitis in recurrent wheeze and asthma-A systematic review and meta-analysis

INTRODUCTION

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis. RSV-induced bronchiolitis has been associated with preschool wheeze and asthma in cohort studies where the comparison groups consist of healthy infants. However, recent studies identify rhinovirus (RV)-induced bronchiolitis as a potentially stronger risk factor for recurrent wheeze and asthma.

AIM

This systematic review and meta-analysis aimed to compare the associations of RSV- and RV-induced bronchiolitis with the development of preschool wheeze and childhood asthma.

METHODS

We performed a systematic search of the published literature in five databases by using a MeSH term-based algorithm. Cohort studies that enrolled infants with bronchiolitis were included. The primary outcomes were recurrent wheeze and asthma diagnosis. Wald risk ratios and odds ratios (ORs) were estimated, along with their 95% confidence intervals (CIs). Individual and summary ORs were visualized with forest plots.

RESULTS

There were 38 studies included in the meta-analysis. Meta-analysis of eight studies that had data on the association between infant bronchiolitis and recurrent wheeze showed that the RV-bronchiolitis group were more likely to develop recurrent wheeze than the RSV-bronchiolitis group (OR 4.11; 95% CI 2.24-7.56). Similarly, meta-analysis of the nine studies that had data on asthma development showed that the RV-bronchiolitis group were more likely to develop asthma (OR 2.72; 95% CI 1.48-4.99).

CONCLUSION

This is the first meta-analysis that directly compares between-virus differences in the magnitude of virus-recurrent wheeze and virus-childhood asthma outcomes. RV-induced bronchiolitis was more strongly associated with the risk of developing wheeze and childhood asthma.

Asthma, atopy and lung function in young adults after hospitalisation for bronchiolitis in infancy: impact of virus and sex

Background

Hospitalisation for bronchiolitis is a risk factor for asthma and impaired lung function during childhood, but outcomes in young adults are poorly described. Our primary aim was to study the prevalence of asthma and atopy, and lung function at 17–20 years of age after bronchiolitis in infancy and, secondarily, the impact of viral aetiology (respiratory syncytial virus (RSV) vs non-RSV) and sex on these outcomes.

Methods

This Norwegian cohort study enrolled 225 young adults hospitalised for bronchiolitis in infancy during 1996–2001 and 167 matched control subjects. The follow-up included questionnaires for asthma and examinations of lung function and atopy. Outcomes were analysed by mixed effects regressions.

Results

Current asthma was more frequent in the postbronchiolitis group versus the control group: 25.1% (95% CI 19.0% to 31.2%) vs 13.1% (95% CI 7.9% to 18.2%), but not atopy: 44.3% (95% CI 37.1% to 51.5%) vs 48.2% (95% CI 40.5% to 55.8%), adjusted predicted proportions (95% CIs). Asthma prevalence did not differ between the RSV group and the non-RSV group: 24.0% (95% CI 16.1% to 32.0%) vs 23.8% (95% CI 12.8% to 34.7%) nor between sexes. Forced expiratory volume in 1 s (FEV₁), the ratio FEV₁/forced vital capacity (FVC), and forced expiratory flow between 25% and 75% of FVC, were lower in the postbronchiolitis group.

Conclusion

Young adults hospitalised for bronchiolitis had higher prevalence of asthma, but not atopy, and a more obstructive lung function pattern than control subjects. The asthma prevalence was high after both RSV bronchiolitis and non-RSV bronchiolitis, and there was no difference between sexes. Bronchiolitis in infancy is associated with respiratory morbidity persisting into young adulthood.

Integrative genetics-metabolomics analysis of infant bronchiolitis-childhood asthma link: A multicenter prospective study

Background

Infants with bronchiolitis are at high risk for developing childhood asthma. While genome-wide association studies suggest common genetic susceptibilities between these conditions, the mechanisms underlying the link remain unclear.

Objective

Through integrated genetics-metabolomics analysis in this high-risk population, we sought to identify genetically driven metabolites associated with asthma development and genetic loci associated with both these metabolites and asthma susceptibility.

Methods

In a multicenter prospective cohort study of infants hospitalized for bronchiolitis, we profiled the nasopharyngeal metabolome and genotyped the whole genome at hospitalization. We identified asthma-related metabolites from 283 measured compounds and conducted metabolite quantitative trait loci (mtQTL) analyses. We further examined the mtQTL associations by testing shared genetic loci for metabolites and asthma using colocalization analysis and the concordance between the loci and known asthma-susceptibility genes.

Results

In 744 infants hospitalized with bronchiolitis, 28 metabolites (e.g., docosapentaenoate [DPA], 1,2-dioleoyl-sn-glycero-3-phosphoglycerol, sphingomyelin) were associated with asthma risk. A total of 349 loci were associated with these metabolites-161 for non-Hispanic white, 120 for non-Hispanic black, and 68 for Hispanics. Of these, there was evidence for 30 shared loci between 16 metabolites and asthma risk (colocalization posterior probability ≥0.5). The significant SNPs within loci were aligned with known asthma-susceptibility genes (e.g., ADORA1, MUC16).

Conclusion

The integrated genetics-metabolomics analysis identified genetically driven metabolites during infancy that are associated with asthma development and genetic loci associated with both these metabolites and asthma susceptibility. Identifying these metabolites and genetic loci should advance research into the functional mechanisms of the infant bronchiolitis-childhood asthma link.

The Role of Interferons in Driving Susceptibility to Asthma Following Bronchiolitis: Controversies and Research Gaps

Bronchiolitis is the most common cause of hospitalization in infancy and is associated with a higher risk for the development of childhood asthma. However, not all children hospitalized with bronchiolitis will develop asthma. The mechanisms underlying asthma development following bronchiolitis hospitalization are complex. Immune responses to respiratory viruses may underlie both bronchiolitis severity and long-term sequela (such as asthma). Interferons (IFNs) are important components of innate immune responses to respiratory viruses and could influence both asthma development and asthma exacerbations. However, the nature of the relationship between interferon production and wheezing illnesses is controversial. For example, low peripheral blood IFN responses at birth have been linked with recurrent wheeze and asthma development. In contrast, there is evidence that severe illnesses (e.g., hospitalization for bronchiolitis) are associated with increased IFN responses during acute infection (bronchiolitis hospitalization) and a higher risk for subsequent asthma diagnosis. Furthermore, mechanistic studies suggest that bronchial epithelial cells from asthmatic children have impaired IFN responses to respiratory viruses, which may enable increased viral replication followed by exaggerated secondary IFN responses. This review aims to discuss controversies around the role of IFNs as drivers of susceptibility to asthma development following bronchiolitis hospitalization. Past evidence from both mechanistic and cohort studies are discussed. We will highlight knowledge gaps that can inform future research study design.

Immunopathology of RSV: An Updated Review

RSV is a leading cause of respiratory tract disease in infants and the elderly. RSV has limited therapeutic interventions and no FDA-approved vaccine. Gaps in our understanding of virus-host interactions and immunity contribute to the lack of biological countermeasures. This review updates the current understanding of RSV immunity and immunopathology with a focus on interferon responses, animal modeling, and correlates of protection.

Maternal gut microbiome regulates immunity to RSV infection in offspring

Development of the immune system can be influenced by diverse extrinsic and intrinsic factors that influence the risk of disease. Severe early life respiratory syncytial virus (RSV) infection is associated with persistent immune alterations. Previously, our group had shown that adult mice orally supplemented with Lactobacillus johnsonii exhibited decreased airway immunopathology following RSV infection. Here, we demonstrate that offspring of mice supplemented with L. johnsonii exhibit reduced airway mucus and Th2 cell–mediated response to RSV infection. Maternal supplementation resulted in a consistent gut microbiome in mothers and their offspring. Importantly, supplemented maternal plasma and breastmilk, and offspring plasma, exhibited decreased inflammatory metabolites. Cross-fostering studies showed that prenatal Lactobacillus exposure led to decreased Th2 cytokines and lung inflammation following RSV infection, while postnatal Lactobacillus exposure diminished goblet cell hypertrophy and mucus production in the lung in response to airway infection. These studies demonstrate that Lactobacillus modulation of the maternal microbiome and associated metabolic reprogramming enhance airway protection against RSV in neonates.

Factors Associated With Bronchiolitis Guideline Nonadherence at US Children's Hospitals

BACKGROUND

The objective with this study was to explore factors associated with nonadherence to national bronchiolitis guidelines at 52 children's hospitals.

METHODS

We included patients 1 month to 2 years old with emergency department (ED) or admission encounters between January 2016 and December 2018 and bronchiolitis diagnoses in the Pediatric Health Information System database. We excluded patients with any intensive care, stay >7 days, encounters in the preceding 30 days, chronic medical conditions, croup, pneumonia, or asthma. Guideline nonadherence was defined as receiving any of 5 tests or treatments: bronchodilators, chest radiographs, systemic steroids, antibiotics, and viral testing. Nonadherence outcomes were modeled by using mixed effects logistic regression with random effects for providers and hospitals. Adjusted odds ratio (aOR) >1 indicates greater likelihood of nonadherence.

RESULTS

A total of 198 028 encounters were included (141 442 ED and 56 586 admission), and nonadherence was 46.1% (ED: 40.2%, admissions: 61.0%). Nonadherence increased with patient age, with both ED and hospital providers being more likely to order tests and treatments for children 12 to 24 months compared with infants 1 ot 2 months (ED: aOR, 3.39; 95% confidence interval [CI], 3.20-3.60; admissions: aOR, 2.97; CI, 2.79-3.17]). Admitted non-Hispanic Black patients were more likely than non-Hispanic white patients to receive guideline nonadherent care (aOR, 1.16; CI, 1.10-1.23), a difference driven by higher use of steroids (aOR, 1.29; CI, 1.17-1.41) and bronchodilators (aOR, 1.39; CI, 1.31-1.48). Hospital effects were prominent for viral testing in ED and admission encounters (intraclass correlation coefficient of 0.35 and 0.32, respectively).

CONCLUSIONS

Multiple factors are associated with national bronchiolitis guideline nonadherence.

Epicutaneous immunization using synthetic virus-like particles efficiently boosts protective immunity to respiratory syncytial virus

Despite the substantial health and economic burden caused by RSV-associated illness, no vaccine is available. The sole licensed treatment (palivizumab), composed of a monoclonal neutralizing antibody, blocks the fusion of the virus to the host cell but does not prevent infection. The development of a safe and efficacious RSV vaccine is therefore a priority, but also a considerable challenge, and new innovative strategies are warranted. Most of the adult population encounter regular RSV infections and can elicit a robust neutralizing antibody response, but unfortunately it wanes over time and reinfections during subsequent seasons are common. One approach to protect the mother and young infant from RSV infection is to administer a vaccine capable of boosting preexisting RSV immunity during pregnancy, which would provide protection to the fetus through passive transfer of maternal antibodies, thus preventing primary RSV infection in newborns during their first months of life. Here, we describe the preclinical evaluation of an epicutaneous RSV vaccine booster that combines epicutaneous patches as a delivery platform and a Synthetic Virus-Like Particles (SVLP)-based vaccine displaying multiple RSV F-protein site II (FsII, palivizumab epitope) mimetic as antigen (V-306). We demonstrated in mice that epicutaneous immunization with V-306 efficiently boosts preexisting immunity induced by the homologous V-306 administered subcutaneously. This boosting was characterized by a significant increase in F- and FsII-specific antibodies capable of competing with palivizumab for its target antigen and neutralize RSV. More importantly, epicutaneous booster immunization with V-306 significantly decreased lung viral replication in experimental mice after intranasal RSV challenge, without inducing enhanced RSV disease. In conclusion, an epicutaneous booster vaccine based on V-306 is safe and efficacious in enhancing RSV preexisting immunity in mice. This needle-free vaccine candidate would be potentially suited as a booster vaccine for vulnerable populations such as young infants via pregnant women, and the elderly.

Eosinophils and Chronic Respiratory Diseases in Hospitalized COVID-19 Patients

BACKGROUND

Studies on the role of eosinophils in coronavirus disease 2019 (COVID-19) are scarce, though available findings suggest a possible association with disease severity. Our study analyzes the relationship between eosinophils and COVID-19, with a focus on disease severity and patients with underlying chronic respiratory diseases.

METHODS

We performed a retrospective analysis of 3018 subjects attended at two public hospitals in Madrid (Spain) with PCR-confirmed SARS-CoV-2 infection from January 31 to April 17, 2020. Patients with eosinophil counts less than 0.02×109/L were considered to have eosinopenia. Individuals with chronic respiratory diseases (n=384) were classified according to their particular underlying condition, i.e., asthma, chronic pulmonary obstructive disease, or obstructive sleep apnea.

RESULTS

Of the 3018 patients enrolled, 479 were excluded because of lack of information at the time of admission. Of 2539 subjects assessed, 1396 patients presented an eosinophil count performed on admission, revealing eosinopenia in 376 cases (26.93%). Eosinopenia on admission was associated with a higher risk of intensive care unit (ICU) or respiratory intensive care unit (RICU) admission (OR:2.21; 95%CI:1.42-3.45; p<0.001) but no increased risk of mortality (p>0.05).

CONCLUSIONS

Eosinopenia on admission conferred a higher risk of severe disease (requiring ICU/RICU care), but was not associated with increased mortality. In patients with chronic respiratory diseases who develop COVID-19, age seems to be the main risk factor for progression to severe disease or death.

Association between early bronchiolitis and the development of childhood asthma: a meta-analysis

OBJECTIVE

Early life bronchiolitis has been hypothesised to be associated with the subsequent risk of persistent wheezing or asthma. However, the link remains controversial. The objective of our study was to evaluate the association between bronchiolitis before 2 years of age and the late-onset wheezing/asthma.

DESIGN

Systematic review and meta-analysis.

METHODS

PubMed, Embase and Web of Science databases were systematically searched for studies published between 1955 and January 2020. Meanwhile, we also checked through the reference lists of relevant articles to see whether these references included reports of other studies that might be eligible for the review. Cohort and case-control studies assessing the association between early-life bronchiolitis and late-onset wheezing/asthma were included in this meta-analysis. Data were extracted by two independent reviewers. Results were pooled using a random-effects model or fixed-effects model according to the heterogeneity among studies.

RESULTS

32 original articles with 292 844 participants, which met the criteria, were included in this meta-analysis. Bronchiolitis before 2 years of age was associated with an increased risk of subsequent wheezing/asthma (relative risk=2.46, 95% CI 2.14 to 2.82, p<0.001). After categorising studies into different groups based on age at the end of follow-up, geographical region and study quality, the association still remained significant.

CONCLUSIONS

The meta-analysis indicates an association between bronchiolitis before 2 years of age and the wheezing/asthma in later life. Well-designed and highly standardised prospective studies that better address bias due to potential confounding factors are needed to validate the risk identified in our meta-analysis.PROSPERO registration numberCRD42018089453.

Sex and Gender Differences in Lung Disease

Sex differences in the anatomy and physiology of the respiratory system have been widely reported. These intrinsic sex differences have also been shown to modulate the pathophysiology, incidence, morbidity, and mortality of several lung diseases across the life span. In this chapter, we describe the epidemiology of sex differences in respiratory diseases including neonatal lung disease (respiratory distress syndrome, bronchopulmonary dysplasia) and pediatric and adult disease (including asthma, cystic fibrosis, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, lung cancer, lymphangioleiomyomatosis, obstructive sleep apnea, pulmonary arterial hypertension, and respiratory viral infections such as respiratory syncytial virus, influenza, and SARS-CoV-2). We also discuss the current state of research on the mechanisms underlying the observed sex differences in lung disease susceptibility and severity and the importance of considering both sex and gender variables in research studies' design and analysis.

Influence of age, sex and respiratory viruses on the rates of emergency department visits and hospitalisations with respiratory tract infections, asthma and COPD

Background

The importance of age, sex and respiratory virus prevalence in emergency department (ED) visits and hospitalisations for respiratory tract infections (RTIs), asthma and COPD in a whole population over time is not well established.

Methods

This study retrospectively analysed data for daily ED visits and hospitalisations from 2003 to 2013 in Ontario, Canada and the daily number of virus positive tests. Daily numbers of ED visits and hospitalisations with RTIs, asthma and COPD listed as a primary diagnosis were collected from the Canadian Institute for Health Information. Virus data were obtained from the Respiratory Virus Detection Surveillance System. Multiple linear regression was used to assess the association of individual viruses with the daily rates.

Results

There were 4 365 578 ED visits and 321 719 (7.4%) admissions for RTIs, 817 141 ED visits and 260 665 (31.9%) admissions for COPD and 649 666 ED visits and 68 626 (10.6%) admissions for asthma. Respiratory syncytial virus and influenza A were associated with male ED visits, whereas human rhinovirus was associated with female ED visits for RTIs in preschool children. 19.2% of males, but only 7.2% of females were admitted. The correlation between the prevalence of each virus and ED visits and hospitalisations for asthma was weak, irrespective of age group and sex. Influenza A was most strongly associated with COPD ED visits and hospitalisations in males and females.

Conclusions

There are significant age and sex differences in the contribution of respiratory viruses to the number of ED visits and hospitalisations for RTIs, asthma and COPD.

There are important age- and sex-related differences in the contribution of respiratory viruses to the number of ED visits and hospitalisations for respiratory tract infections, asthma and COPDhttps://bit.ly/39hrhIW

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.

Factors and mechanisms contributing to the development of preschool wheezing disorders

INTRODUCTION

Half of all children will experience an episode of wheezing by their sixth birthday and acute episodes of wheezing in preschool children account for the majority of all childhood hospital admissions for wheeze. Recurrent preschool wheezing associates with early loss of lung function and a life-long impact on lung health.

AREAS COVERED

We reviewed the literature on PubMed from August 2010-2020 focussing on factors associated with wheeze inception and persistence, paying specific attention to mechanistic studies that have investigated the impact of early life exposures in shaping immune responses in children with underlying susceptibility to wheezing. In particular, the role of early allergen sensitization, respiratory infections, and the impact of the environment on shaping the airway microbiome and resulting immune responses are discussed.

EXPERT OPINION

There is an abundance of associative data showing the role of in utero and postnatal factors influencing wheeze onset and persistence. However, mechanistic and stratified, biomarker-based interventional studies that confirm these associations are now needed if we are to impact the significant healthcare burden resulting from preschool wheezing disorders.

NLRP3-Inflammasome Inhibition during Respiratory Virus Infection Abrogates Lung Immunopathology and Long-Term Airway Disease Development

Respiratory syncytial virus (RSV) infects most infants by two years of age. It can cause severe disease leading to an increased risk of developing asthma later in life. Previously, our group has shown that RSV infection in mice and infants promotes IL-1β production. Here, we characterized the role of NLRP3-Inflammasome activation during RSV infection in adult mice and neonates. We observed that the inhibition of NLRP3 activation using the small molecule inhibitor, MCC950, or in genetically modified NLRP3 knockout (Nlrp3−/−) mice during in vivo RSV infection led to decreased lung immunopathology along with a reduced expression of the mucus-associated genes and reduced production of innate cytokines (IL-1β, IL-33 and CCL2) linked to severe RSV disease while leading to significant increases in IFN-β. NLRP3-inflammasome inhibition or deletion diminished Th2 cytokines and inflammatory cell infiltration into the lungs. Furthermore, NLRP3 inhibition or deletion during early-life RSV infection led to reducing viral-exacerbated allergic response in a mouse model of RSV-induced allergy exacerbation. Here, we demonstrated the critical role of NLRP3-inflammasome activation in RSV immunopathology and the related long-term airway alteration. Moreover, these findings suggest the NLRP3-inflammasome as a potential therapeutic target to attenuate severe RSV disease and limit childhood asthma development.

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.

Inhibition of Autophagy Does Not Affect Innate Cytokine Production in Human Lung Epithelial Cells During Respiratory Syncytial Virus Infection

Human respiratory syncytial virus (RSV) is one of the major causes of childhood acute lower respiratory tract infection worldwide. Autophagy is an intracellular pathway involved in nutrient recycling. Recently, autophagy has been reported to play a role in regulating host cytokine response to several viruses, including vesicular stomatitis virus and human immunodeficiency virus. Previous in vivo studies using mouse model has shown that inhibition of autophagy reduces RSV-induced cytokine production. However, the role of autophagy in modulating RSV-induced cytokine response in human cells has not been reported. We investigated the role of autophagy in regulating the production of the cytokines C-X-C motif ligand 8 (CXCL8) and C-C motif ligand 5 (CCL5), in RSV-infected human bronchial epithelium BEAS-2B cells. Fluorescent microscopic analysis showed that RSV infection induced autophagosome formation in BEAS-2B cells. This autophagy inducing ability of RSV was further confirmed by flow cytometry. The effects of pharmacological inhibition of autophagy by SAR405 or chloroquine on cell death and cytokine release were quantified using lactate dehydrogenase assay and enzyme-linked immunosorbent assay (ELISA), respectively. We found that SAR405 or chloroquine did not cause cell death. Importantly, ELISA analysis showed that pharmacological inhibition of autophagy by SAR405 or chloroquine did not affect the productions of both CXCL5 and CXCL8. In contrast to the previous studies using mouse model, our data suggest that pharmacological inhibition of autophagy may not be a suitable strategy in controlling RSV-induced airway inflammation.

From Submerged Cultures to 3D Cell Culture Models: Evolution of Nasal Epithelial Cells in Asthma Research and Virus Infection

Understanding the response to viral infection in the context of respiratory diseases is of significant importance. Recently, there has been more focus on the role of the nasal epithelium in disease modeling. Here, we provide an overview of different submerged, organotypic 3D and spheroid cell culture models of nasal epithelial cells, which were used to study asthma and allergy with a special focus on virus infection. In detail, this review summarizes the importance, benefits, and disadvantages of patient-derived cell culture models of nasal- and bronchial epithelial cells, including a comparison of these cell culture models and a discussion on why investigators should consider using nasal epithelial cells in their research. Exposure experiments, simple virus transduction analyses as well as genetic studies can be performed in these models, which may provide first insights into the complexity of molecular signatures and may open new doors for drug discovery and biomarker research.

TSLP-Driven Chromatin Remodeling and Trained Systemic Immunity after Neonatal Respiratory Viral Infection

Our studies have previously shown a role for persistent TSLP production in the lungs of mice after early-life respiratory syncytial virus (RSV) infection that leads to an altered immune phenotype, including accumulation of "inflammatory" dendritic cells (DC). This study investigates the role of TSLP driving systemic trained immunity in DC in early-life RSV-infected mice. Bone marrow-derived DCs (BMDC) from early-life RSV-infected mice at 4 wk postinfection showed enhanced expression of costimulatory molecules and cytokines, including Tslp, that regulate immune cell function. The adoptive transfer of BMDC grown from early-life RSV-infected mice was sufficient to exacerbate allergic disease development. The addition of recombinant TSLP during differentiation of BMDC from naive mice induced a similar altered phenotype as BMDC grown from early-life RSV-infected mice, suggesting a role for TSLP in the phenotypic changes. To assess the role of TSLP in these changes, global transcriptomic characterization of TSLPR^-/- BMDC infected with RSV was performed and showed a higher upregulation of type 1 IFN genes and concomitant downregulation of inflammatory genes. Assay for transposase-accessible chromatin using sequencing analysis demonstrated that TSLPR^-/- BMDC had a parallel gain in physical chromatin accessibility near type 1 genes and loss in accessibility near genes related to RSV pathology, with IFN regulatory factor 4 (IRF4) and STAT3 predicted as top transcription factors binding within differentially accessible regions in wild-type. Importantly, these studies show that in the absence of TSLP signaling, BMDC are able to mount an appropriate type 1 IFN-associated antiviral response to RSV. In summary, RSV-induced TSLP alters chromatin structure in DC to drive trained innate immunity and activates pathogenic gene programs in mice.

Economic-Burden Trajectories in Commercially Insured US Infants With Respiratory Syncytial Virus Infection

BACKGROUND

This study evaluates the long-term respiratory syncytial virus (RSV) burden among preterm and full-term infants in the United States.

METHODS

Infants with birth hospitalization claims and ≥24 months of continuous enrollment were retrospectively identified in the Truven MarketScan Commercial Claims and Encounters database for the period 1 January 2004-30 September 2015. Infants with RSV infection in the first year of life (n = 38 473) were matched to controls (n = 76 825), and remaining imbalances in the number of individuals in each group were adjusted using propensity score methods. All-cause, respiratory-related, and asthma/wheezing-related 5-year average cumulative costs were measured.

RESULTS

Early premature (n = 213), premature (n = 397), late premature (n = 4446), and full-term (n = 33 417) RSV-infected infants were matched to 424, 791, 8875, and 66 735 controls, respectively. After 2 years since RSV diagnosis, all-cause cumulative costs for RSV-infected infants as compared to those for controls increased by $22 081 (95% confidence interval [CI], -$5800-$42 543) for early premature infants, by $14 034 (95% CI, $5095- $22 973) for premature infants, by $10 164 (95% CI, $8835-$11 493) for late premature infants, and by $5404 (95% CI, $5110-$5698) for full-term infants. The 5-year RSV burden increased to $39 490 (95% CI, $18 217-$60 764), $23 160 (95% CI, $13 002-$33 317),$13 755 (95% CI, $12 097-$15 414), and $6631 (95% CI, $6060-$7202), respectively. The RSV burden was higher when stratified by inpatient and outpatient setting and respiratory-related and asthma/wheezing-related costs.

CONCLUSIONS

The RSV burden extends across cost domains and prematurity, with the greatest burden incurred by the second year of follow-up. Findings are useful in determining the cost-effectiveness of RSV therapies in development.

Long-term Assessment of Healthcare Utilization 5 Years After Respiratory Syncytial Virus Infection in US Infants

BACKGROUND

Respiratory syncytial virus (RSV) is the primary cause of respiratory tract infections in infants; however, current burden estimates report only the short-term effects of acute infection.

METHODS

Infants with RSV infection and ≥24 months of continuous enrollment were retrospectively identified from the Truven MarketScan database (1 January 2004-30 September 2015). Exposed infants (n = 38 473) were propensity score matched to nonexposed controls (n = 76 825) by baseline characteristics and gestational age. Five-year cumulative all-cause, asthma/wheezing, and respiratory event-related hospitalization rates and physician and emergency department healthcare-resource utilization rates were assessed.

RESULTS

During follow-up, RSV-infected cohorts had higher average all-cause cumulative hospitalization rates, compared with controls, with values of 79.9 hospitalizations/100 patient-years (95% confidence interval [CI], 41.7-118.2) for 213 early premature infants (P < .001), 18.2 hospitalizations/100 patient-years (95% CI, .8-35.7) for 397 premature infants (P = .04), 34.2 hospitalizations/100 patient-years (95% CI, 29.1-39.2) for 4446 late premature infants (P < .001), and 16.1 hospitalizations/100 patient-years (95% CI, 14.9-17.4) for 33 417 full-term infants (P < .001). Cumulative rates of physician and emergency department visits were also higher for RSV-infected infants. Asthma/wheezing accounted for 10%-18% of total 5-year physician visits.

CONCLUSIONS

Infant RSV infection has a significant long-term healthcare-resource utilization impact across gestational ages for at least 5 years after infection, most of it in the first 2 years. Systematically collecting healthcare-resource utilization data will be important for cost-effectiveness evaluations of RSV interventions in planned or ongoing trials.