An algorithm for discontinuing mechanical ventilation in boys with x-linked myotubular myopathy after positive response to gene therapy: the ASPIRO experience.

X-linked myotubular myopathy (XLMTM) is a rare, life-threatening congenital myopathy. Most (80%) children with XLMTM have profound muscle weakness and hypotonia at birth resulting in severe respiratory insufficiency, the inability to sit up, stand or walk, and early mortality. At birth, 85-90% of children with XLMTM require mechanical ventilation, with more than half requiring invasive ventilator support. Historically, ventilator-dependent children with neuromuscular-derived respiratory failure of this degree and nature, static or progressive, are not expected to achieve complete independence from mechanical ventilator support. In the ASPIRO clinical trial (NCT03199469), participants receiving a single intravenous dose of an investigational gene therapy (resamirigene bilparvovec) started showing significant improvements in daily hours of ventilation support compared with controls by 24 weeks post-dosing, and 16 of 24 dosed participants achieved ventilator independence between 14 and 97 weeks after dosing. At the time, there was no precedent or published guidance for weaning chronically ventilated children with congenital neuromuscular diseases off mechanical ventilation. When the first ASPIRO participants started showing dramatically improved respiratory function, the investigators initiated efforts to safely wean them off ventilator support, in parallel with primary protocol respiratory outcome measures. A group of experts in respiratory care and physiology and management of children with XLMTM developed an algorithm to safely wean children in the ASPIRO trial off mechanical ventilation as their respiratory muscle strength increased. The algorithm developed for this trial provides recommendations for assessing weaning readiness, a stepwise approach to weaning, and monitoring of children during and after the weaning process.

High TSLP responses in the human infant airways are associated with pre-activated airway epithelial IFN antiviral immunity.

Thymic stromal lymphopoietin (TSLP) is a primarily epithelial-derived cytokine that drives type 2 allergic immune responses. Early life viral respiratory infections elicit high TSLP production, which leads to the development of type 2 inflammation and airway hyperreactivity. The goal of this study was to examine in vivo and in vitro the human airway epithelial responses leading to high TSLP production during viral respiratory infections in early infancy. A total of 129 infants (<1-24 m, median age 10 m) with severe viral respiratory infections were enrolled for in vivo (n = 113), and in vitro studies (n = 16). Infants were classified as 'high TSLP' or 'low TSLP' for values above or below the 50th percentile. High versus low TSLP groups were compared in terms of type I-III IFN responses and production of chemokines promoting antiviral (CXCL10), neutrophilic (CXCL1, CXCL5, CXCL8), and type 2 responses (CCL11, CCL17, CCL22). Human infant airway epithelial cell (AEC) cultures were used to define the transcriptomic (RNAseq) profile leading to high versus low TSLP responses in vitro in the absence (baseline) or presence (stimulated) of a viral mimic (poly I:C). Infants in the high TSLP group had greater in vivo type III IFN airway production (median type III IFN in high TSLP 183.2 pg/mL vs. 63.4 pg/mL in low TSLP group, p = 0.007) and increased in vitro type I-III IFN AEC responses after stimulation with a viral mimic (poly I:C). At baseline, our RNAseq data showed that infants in the high TSLP group had significant upregulation of IFN signature genes (e.g., IFIT2, IFI6, MX1) and pro-inflammatory chemokine genes before stimulation. Infants in the high TSLP group also showed a baseline AEC pro-inflammatory state characterized by increased production of all the chemokines assayed (e.g., CXCL10, CXCL8). High TSLP responses in the human infant airways are associated with pre-activated airway epithelial IFN antiviral immunity and increased baseline AEC production of pro-inflammatory chemokines. These findings present a new paradigm underlying the production of TSLP in the human infant airway epithelium following early life viral exposure and shed light on the long-term impact of viral respiratory illnesses during early infancy and beyond childhood.

Airway clearance after highly effective CFTR modulators: Normalizing life and reducing treatment burden.

OBJECTIVES: Airway clearance therapy (ACT) is an important component of therapy for cystic fibrosis (CF) but is associated with significant treatment burden. Highly effective CFTR modulator therapy (HEMT) has improved pulmonary function for many people with CF (pwCF). We sought to understand changes in attitudes and practices about ACT in the post-HEMT era. STUDY DESIGN: Surveys of CF community members and CF care team members. METHODOLOGY: Separate surveys were created for the CF community and CF care providers to evaluate attitudes towards ACT and exercise in the post-HEMT era. We solicited answers from pwCF via the CF Foundation's Community Voice and from CF care providers via CF Foundation listservs. Surveys were available between July 20 and August 3, 2021. RESULTS: Surveys were completed by 153 community members (parents of children and pwCF) and 192 CF care providers. Belief that exercise can substitute partially for ACT was endorsed similarly by community members (59%) and providers (68%). After starting HEMT, 36% of parents of children and 51% of adults did fewer ACT treatments including 13% who stopped ACT. Adults reported altering their ACT regimen more than parents of children, though the sample size was limited. Half of providers had changed their ACT recommendations for those on HEMT. Fifty-three percent of respondents had discussed changing ACT with their care team (36% of parents, 58% of pwCF). CONCLUSIONS: Providers should be aware that ACT management changes may have been undertaken by pwCF who have pulmonary benefits of HEMT. Treatment burden should be considered in co-management decisions regarding ACT and exercise.

Asthma Cases Treated With Inhaled Anesthetics or Extracorporeal Membrane Oxygenation: A Virtual Pediatric Systems Database Study of Outcomes.

OBJECTIVES: Extracorporeal membrane oxygenation (ECMO) and/or inhaled anesthetics (IAs) are considered in the management of asthma when refractory to conventional therapy. We aimed to compare the outcomes of these two modalities in asthma PICU care and determine associated survival to hospital discharge among patients in a United States database. DESIGN: Retrospective analysis using the Virtual Pediatric Systems (VPS, LLC) database. SETTING: PICUs participating in the VPS database. PATIENTS: Patients less than 18 years old with diagnosis of asthma treated with IA and/or ECMO from January 2010 to December 2020. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A total of 221 patients were included; 149 (67%) received ECMO, 62 (28%) received IA, and 10 (5%) received both interventions. We failed to identify any difference between the ECMO and IA groups in demographics, Pediatric Index of Mortality 2 percentage, Pediatric Risk of Mortality 3 score, Pediatric Logistic Organ Dysfunction score, or pre-intervention pH and Pa co2 levels. Use of ECMO versus IA was associated with lower pre-intervention Pa o2 (60 torr [7.99 kPa] vs 78 torr [10.39 kPa]; p < 0.001) and higher utilization of high-frequency oscillatory ventilation. We failed to identify an association between type of intervention (IA vs ECMO) and greater odds of survival (57/62 [92%] vs 128/149 [86%]; odds ratio [OR], 1.87; 95% CI, 0.67-5.21; p = 0.23). However, these data do not exclude the possibility that IA use is associated with more than five-fold greater odds of survival. ECMO use was associated with longer duration of intervention (5 vs 1.3 d; p < 0.001) and PICU length of stay (LOS) (13 vs 7 d; p < 0.001). As expected, ECMO versus IA was also associated with greater odds of undergoing bronchoscopy (34% vs 11%; OR, 3.7; 95% CI, 1.5-9.4; p = 0.004). CONCLUSIONS: In the VPS database of asthma management cases, we failed to identify an association between ECMO versus IA use and survival to hospital discharge. However, ECMO was associated with longer duration of intervention and PICU LOS.

Parental survey of the sleep patterns and screen time in US school children during the first 6 months of the COVID-19 pandemic.

BACKGROUND: This study compared sleep duration, screen exposure and sleep quality in school-aged children before COVID-19 to that during school closures and again when schools re-opened in fall 2020. METHODS: Cross-sectional anonymous, online survey of parents of children 5-13 years old. Questions elicited information about sleep timing and quality, screen time, and schooling at three distinct periods: before the pandemic, when schools first closed and then re-opened in the fall. RESULTS: Respondents described 101 children who were an average of 8.5 years old and 51% male. In lockdown, children slept 25 min more (95%CI 00:13-00:38) due to later wake times (75 min, 95% CI 0:57-1:34) with later bedtimes (29 min, 95%CI 0:00-0:58). When schools re-opened, sleep duration returned to pre-pandemic levels, but sleep onset and offset times remained later. Despite more sleep, sleep quality and habits (e.g. bedtime refusal) worsened during lockdown and did not normalize in fall 2020. During lockdown, screen time increased in 65% of all children, and 96% of those in private schools. When schools reopened, 78% of children in hybrid/virtual learning had more than 4 h of screen exposure daily. Less screen time was associated with twofold higher odds of better sleep (OR 2.66, 95%CI 1.15-6.14). CONCLUSIONS: Although school-aged children had more total sleep when schools were closed, sleep quality and habits worsened. Upon return to school, sleep times and quality did not normalize and were linked to screen time.

Airway clearance therapy in the school environment: Retrospective analysis of a cohort of pediatric patients with cystic fibrosis.

BACKGROUND: Adherence to airway clearance therapy (ACT) in pediatric cystic fibrosis (CF) patients is reported to be below 50% and inability to sustain daily care is linked to poor health outcomes7,8,9. Through a collaboration between a CF care center and several schools, we hypothesized that ACT completed at school by pediatric CF patients will improve lung function while decreasing pulmonary exacerbations (PEx), days of antibiotics (abx) and hospitalizations. METHODS: This was a retrospective case-control study at a single CF care center consisting of 50 CF patients age < 18 at time when data was recorded (2012-2020). The case group used high-frequency chest wall oscillation or positive expiratory pressure devices at school for at least 1 year after self-reported or physician identified inadequate use at home. Lung function and measures of healthcare utilization were collected. RESULTS: In the case group (n = 14), paired t-tests showed that after initiation of ACT at school, there were significant reductions in PEx requiring IV or PO abx (P = 0.010), total days of abx (P = 0.032), and visits to the CF care center (P = 0.037). There was no change in these outcomes in the matched control group (n = 36). CONCLUSIONS: This is the first known study to highlight an initiative between a CF care center and schools which utilized airway clearance devices at school to ensure pediatric CF patients completed ACT. Through increased adherence, this relationship was associated with improved health outcomes. Use of alternative strategies may help patients with CF sustain adequate airway clearance.

Pulmonological issues.

Pediatric leukodystrophies are rare neurodegenerative diseases involving multiple systems. Each form has unique neurologic features but are characterized by encephalopathy with accompanying impairments evidenced in reflexes, muscle tone and movement control. Weakness of expiratory, inspiratory, and upper airway muscles may lead to impaired airway secretion clearance resulting in recurrent respiratory infections, dysphagia, sleep-disordered breathing, restrictive lung disease, and ultimately chronic respiratory insufficiency.

Dynamic PEEP Study: A Non-invasive Diagnostic Exam to Assess for Effective PEEP in Children with Severe BPD.

OBJECTIVE: Tracheobronchomalacia (TBM) is common in neonates with bronchopulmonary dysplasia (BPD) and is associated with higher morbidity. This study evaluates the value of a CT protocol to assess the degree of TBM and gauge the adequacy of prescribed PEEP. STUDY DESIGN: Four infants with severe BPD on invasive mechanical ventilation underwent a chest CT protocol, including limited reduced-dose expiratory scans with varying PEEP levels. RESULTS: Baseline PEEP was adjusted in all subjects after performing the Dynamic PEEP CT. In two infants, the PEEP was increased due to significant TBM and in the other two without signs of TBM PEEP was decreased. The clinical course improved in all patients after adjusting PEEP. CONCLUSION: A "Dynamic PEEP" study may be reliable and non-invasive imaging modality for the evaluation of adequate ventilator settings in infants with severe BPD who are not optimal candidates for bronchoscopy.

Measuring the impact of an empiric antibiotic algorithm for pulmonary exacerbation in children and young adults with cystic fibrosis.

BACKGROUND: Antimicrobial stewardship is a systematic effort to change prescribing attitudes that can provide benefit in the provision of care to persons with cystic fibrosis (CF). Our objective was to decrease the unwarranted use of broad-spectrum antibiotics and assess the impact of an empiric antibiotic algorithm using quality improvement methodology. METHODS: We assembled a multidisciplinary team with expertise in CF. We assessed baseline antibiotic use for treatment of pulmonary exacerbation (PEx) and developed an algorithm to guide empiric antibiotic therapy. We included persons with CF admitted to Children's National Hospital for treatment of PEx between January 2017 and March 2020. Our primary outcome measure was reducing unnecessary broad-spectrum antibiotic use, measured by use consistent with the empiric antibiotic algorithm. The primary intervention was the initiation of the algorithm. Secondary outcomes included documentation of justification for broad-spectrum antibiotic use and use of infectious disease (ID) consult. RESULTS: Data were collected from 56 persons with CF who had a total of 226 PEx events. The mean age at first PEx was 12 (SD 6.7) years; 55% were female, 80% were white, and 29% were Hispanic. After initiation of the algorithm, the proportion of PEx with antibiotic use consistent with the algorithm increased from 46.2% to 79.5%. Documentation of justification for broad-spectrum antibiotics increased from 56% to 85%. Use of ID consults increased from 17% to 54%. CONCLUSION: Antimicrobial stewardship initiatives are beneficial in standardizing care and fostering positive working relationships between CF pulmonologists, ID physicians, and pharmacists.

Genes, environment, and developmental timing: New insights from translational approaches to understand early origins of respiratory diseases.

Over the past decade, "omics" approaches have advanced our understanding of the molecular programming of the airways in humans. Several studies have identified potential molecular mechanisms that contribute to early life epigenetic reprogramming, including DNA methylation, histone modifications, microRNAs, and the homeostasis of the respiratory mucosa (epithelial function and microbiota). Current evidence supports the notion that early infancy is characterized by heightened susceptibility to airway genetic reprogramming in response to the first exposures in life, some of which can have life-long consequences. Here, we summarize and analyze the latest insights from studies that support a novel epigenetic paradigm centered on human maturational and developmental programs including three cardinal elements: genes, environment, and developmental timing. The combination of these factors is likely responsible for the functional trajectory of the respiratory system at the molecular, functional, and clinical levels.

Airway Remodeling Factors During Early-Life Rhinovirus Infection and the Effect of Premature Birth.

Background: Early rhinovirus (RV) infection is a strong risk factor for asthma development. Airway remodeling factors play a key role in the progression of the asthmatic condition. We hypothesized that RV infection in young children elicits the secretion of growth factors implicated in airway remodeling and asthma progression. Methods: We examined the nasal airway production of remodeling factors in children ( ≤ 2 years old) hospitalized due to PCR-confirmed RV infection. Airway remodeling proteins included: MMP-1, MMP-2, MMP-7, MMP-9, MMP-10, TIMP-1, TIMP-2, EGF, Angiopoietin-2, G-CSF, BMP-9, Endoglin, Endothelin-1, Leptin, FGF-1, Follistatin, HGF, HB-EGF, PLGF, VEGF-A, VEGF-C, VEGF-D, FGF-2, TGF-ß1, TGF-ß2, TGF-ß3, PDGF AA, PDGF BB, SPARC, Periostin, OPN, and TGF-α. Results: A total of 43 young children comprising RV cases (n = 26) and uninfected controls (n = 17) were included. Early RV infection was linked to (1) enhanced production of several remodeling factors (e.g., HGF, TGFα), (2) lower MMP-9/TIMP-2 and MMP-2/TIMP-2 ratios, and (3) increased MMP-10/TIMP-1 ratios. We also found that relative to term infants, severely premature children had reduced MMP-9/TIMP-2 ratios at baseline. Conclusion: RV infection in young children elicits the airway secretion of growth factors implicated in angiogenesis, fibrosis, and extracellular matrix deposition. Our results highlight the potential of investigating virus-induced airway remodeling growth factors during early infancy to monitor and potentially prevent chronic progression of respiratory disorders in all ages.

Cost-effectiveness analysis of phenotypic-guided versus guidelines-guided bronchodilator therapy in viral bronchiolitis.

OBJECTIVES: Although recent evidence suggests that management of viral bronchiolitis requires something other than guidelines-guided therapy, there is a lack of evidence supporting the economic benefits of phenotypic-guided bronchodilator therapy for treating this disease. The aim of the present study was to compare the cost-effectiveness of phenotypic-guided versus guidelines-guided bronchodilator therapy in infants with viral bronchiolitis. METHODS: A decision analysis model was developed to compare the cost-effectiveness of phenotypic-guided versus guidelines-guided bronchodilator therapy in infants with viral bronchiolitis. Phenotypic-guided bronchodilator therapy was defined as the administration of albuterol in infants exhibiting a profile of increased likelihood of response to bronchodilators. The effectiveness parameters and costs of the model were obtained from systematic reviews of the literature with meta-analyses and electronic medical records. The main outcome was the avoidance of hospital admission after initial care in the emergency department. RESULTS: Compared to guidelines-guided strategy, treating patients with viral bronchiolitis with the phenotypic-guided bronchodilator therapy strategy was associated with lower total costs (US$250.99; 95% uncertainty interval [UI]: US$184.37 to $336.51 vs. US$263.46; 95% UI: US$189.81 to $349.19 average cost per patient) and a higher probability of avoidance of hospital admission (0.7902; 95% UI: 0.7315-0.8356 vs. 0.7638; 95% UI: 0.7062-0.8201), thus leading to dominance. Results were robust to deterministic and probabilistic sensitivity analyses. CONCLUSIONS: Compared to guidelines-guided strategy, treating infants with viral bronchiolitis using the phenotypic-guided bronchodilator therapy strategy is a more cost-effective strategy, because it involves a lower probability of hospital admission at lower total treatment costs.

Decrease in Respiratory Related Hospitalizations in Tracheostomy-Dependent Children Who Tolerate Passy-Muir Valve Use.

OBJECTIVE: To assess the effect of Passy-Muir® Valve (PMV) tolerance on respiratory illness and respiratory related hospital admissions in tracheostomy-dependent children. METHODS: Retrospective cohort study of 262 patients who underwent tracheostomy placement between 2012 and 2018 at a tertiary free-standing children's hospital. Outcome measures studied were number of reported upper respiratory infections and respiratory related hospitalizations per year (RRH/year). RESULTS: About 135 (51.5%) tracheostomy-dependent children underwent PMV trials, and 106 (78.5%) of these children were able to tolerate PMV for at least 1 hour daily. When comparing children who tolerated PMV versus those who did not, the latter group had significantly higher rates of subglottic stenosis but no significant differences in RRH/year or average age. In those children who tolerated PMV and achieved routine use of PMV > 1 hour/day, an average of 1.14 RRH/year occurred prior to PMV tolerance, as compared with 0.57 RRH/year after PMV tolerance (P = .003). Multivariate analysis shows that in patients <2 years, there is a significant decrease in RRH/year after PMV tolerance is attained (1.53 vs 0.76, P = .001), independent of indication for tracheostomy. CONCLUSION: In tracheostomy-dependent children who tolerate PMV use routinely >1 hour/day there are decreased rates of respiratory related hospitalizations (RRH). Children <2 years of age have the most impact of RRH, with rates that are significantly lower with routine use of the PMV.

Communication skills among children with spinal muscular atrophy type 1: A parent survey.

Spinal muscular atrophy is one of the most common fatal autosomal recessive disorders. Children diagnosed with SMA Type 1 (SMAT1) demonstrate severe oral motor weakness and flaccid dysarthria progressing to complete anarthria. A review of literature illustrates that little has been described regarding augmentative and alternative communication (AAC) use among these children, although communication has a critical impact on quality of life and participation in daily activities. Responses to an investigator-developed parent survey were obtained to appraise communication skills and opportunities among children diagnosed with SMA1. Results illustrate parent perception of greater receptive than expressive language ability and highlight the benefits of implementing speech-generating devices (SGD). Barriers to SGD acquisition and implementation, including access and funding, are reported and described. Overall, families indicated that SGD increases quality of life and provides valued improvements through expanded functional communication.

Innate IFN-lambda responses to dsRNA in the human infant airway epithelium and clinical regulatory factors during viral respiratory infections in early life.

INTRODUCTION: IFN lambda (type III-IFN-λ1) is a molecule primarily produced by epithelial cells that provides an important first-line defence against viral respiratory infections and has been linked to the pathogenesis of viral-induced wheezing in early life. The goal of this study was to better understand the regulation of innate IFN-lambda responses in vitro in primary human infant airway epithelial cells (AECs) and in vivo using nasal aspirates during viral respiratory infections. METHODS: IFN-lambda protein levels were quantified: (a) in human infant AECs exposed to (poly(I:C) dsRNA) under different experimental conditions (n = 8 donors); and (b) in nasal aspirates of young children (≤3 years) hospitalized with viral respiratory infection (n = 138) and in uninfected controls (n = 74). In vivo IFN-lambda airway levels during viral infections were correlated with individual characteristics and respiratory disease parameters. RESULTS: Our in vitro experiments showed that the poly(I:C)-induced innate production of IFN lambda in human infant AECs is regulated by (a) p38-MAPK/NF-kB dependent mechanism; and (b) exposure to pro-inflammatory signals such as IL1ß. Our in vivo studies demonstrated that (a) infants (<18 months) had higher virus-induced IFN-lambda airway secretion; (b) subjects with RSV infection showed the highest IFN-lambda airway levels; and (c) individuals with the highest virus-induced IFN-lambda levels (>90th percentile) had higher viral loads and were more likely to have respiratory sick visits within 12 months of discharge (OR = 5.8). CONCLUSION: IFN-lambda responses to dsRNA in the human infant airway epithelium are regulated by p38-MAPK and NF-kB signalling. High in vivo IFN-lambda production is influenced by virus type and associated with recurrent respiratory sick visits in young children.

Airway microbial diversity is decreased in young children with cystic fibrosis compared to healthy controls but improved with CFTR modulation.

BACKGROUND: Culture-independent next generation sequencing has identified diverse microbial communities within the cystic fibrosis (CF) airway. The study objective was to test for differences in the upper airway microbiome of children with CF and healthy controls and age-related differences in children with CF. METHODS: Oropharyngeal swabs and clinical data were obtained from 25 children with CF and 50 healthy controls aged ≤6 years. Bacterial DNA was amplified and sequenced for the V4 region of 16S rRNA marker-gene. Alpha diversity was measured using operational taxonomic units (OTUs), Shannon diversity, and the inverse Simpson's index. Beta diversity was measured using Morisita-Horn and Bray-Curtis and Jaccard distances. General linear models were used for comparison of alpha diversity measures between groups to account for differences in demographics and exposures. Mixed effects general linear models were used for longitudinal comparisons 1) between children with CF of different ages and 2) between children with CF receiving CF transmembrane conductance regulator (CFTR) modulators, children with CF not receiving CFTR modulators, and healthy controls to adjust for repeated measures per subject. RESULTS: Children with CF were more likely to have received antibiotics in the prior year than healthy controls (92% vs 24%, p < 0.001). Controlling age, race, ethnicity, length of breastfeeding, and having siblings, children with CF had a lower richness than healthy controls: OTUs 62.1 vs 83, p = 0.022; and trended toward lower diversity: Shannon 2.09 vs 2.35, p = 0.057; inverse Simpson 5.7 vs 6.92, p = 0.118. Staphylococcus, three Rothia OTUs, and two Streptococcus OTUs were more abundant in CF children versus healthy controls (all p < 0.05). Bray-Curtis and Jaccard distances, which reflect overall microbial community composition, were also significantly different (both p = 0.001). In longitudinally collected samples from children with CF, Morisita-Horn trended toward more similarity in those aged 0-2 years compared to those aged 3-6 years (p = 0.070). In children >2 years of age, there was a significant trend in increasing alpha diversity measures between children with CF not receiving CFTR modulators, children with CF receiving CFTR modulators, and healthy controls: OTUs 63.7 vs 74.7 vs 97.6, p < 0.001; Shannon 2.11 vs 2.34 vs 2.56, p < 0.001; inverse Simpson 5.78 vs 7.23 vs 7.96, p < 0.001. CONCLUSIONS: Children with CF have lower bacterial diversity and different composition of organisms compared with healthy controls. This appears to start in early childhood, is possibly related to the use of antibiotics, and may be partially corrected with the use of CFTR modulators.

Airway mir-155 responses are associated with TH1 cytokine polarization in young children with viral respiratory infections.

BACKGROUND: MicroRNAs (miRs) control gene expression and the development of the immune system and antiviral responses. MiR-155 is an evolutionarily-conserved molecule consistently induced during viral infections in different cell systems. Notably, there is still an unresolved paradox for the role of miR-155 during viral respiratory infections. Despite being essential for host antiviral TH1 immunity, miR-155 may also contribute to respiratory disease by enhancing allergic TH2 responses and NFkB-mediated inflammation. The central goal of this study was to define how airway miR-155 production is related to TH1, TH2, and pro-inflammatory cytokine responses during naturally occurring viral respiratory infections in young children. METHODS: Normalized nasal airway levels of miR-155 and nasal protein levels of IFN-γ, TNF-α, IL-1ß, IL-13, IL-4 were quantified in young children (≤2 years) hospitalized with viral respiratory infections and uninfected controls. These data were linked to individual characteristics and respiratory disease parameters. RESULTS: A total of 151 subjects were included. Increased miR-155 levels were observed in nasal samples from patients with rhinovirus, RSV and all respiratory viruses analyzed. High miR-155 levels were strongly associated with high IFN-γ production, increased airway TH1 cytokine polarization (IFN-γ/IL-4 ratios) and increased pro-inflammatory responses. High airway miR-155 levels were linked to decreased respiratory disease severity in individuals with high airway TH1 antiviral responses. CONCLUSIONS: The airway secretion of miR-155 during viral respiratory infections in young children is associated with enhanced antiviral immunity (TH1 polarization). Further studies are needed to define additional physiological roles of miR-155 in the respiratory tract of human infants and young children during health and disease.