Integrated nasopharyngeal airway metagenome and asthma genetic risk endotyping of severe bronchiolitis in infancy and risk of childhood asthma.

The severe bronchiolitis endotype characterized by a high abundance of H. influenzae, high proportion of RV-A and RV-C infections, and high asthma genetic risk had a significantly higher risk for developing asthma. BACKGROUND: Infants with bronchiolitis are at increased risk for developing asthma. Growing evidence suggests bronchiolitis is a heterogeneous condition. However, little is known about its biologically distinct subgroups based on the integrated metagenome and asthma genetic risk signature and their longitudinal relationships with asthma development. METHODS: In a multi-center prospective cohort study of infants with severe bronchiolitis (i.e., bronchiolitis requiring hospitalization), we profiled nasopharyngeal airway metagenome and virus at hospitalization, and calculated the polygenic risk score of asthma. Using similarity network fusion clustering approach, we identified integrated metagenome-asthma genetic risk endotypes. We also examined their longitudinal association with the risk of developing asthma by age six years. RESULTS: Of 450 infants with bronchiolitis (median age, 3 months), we identified five distinct endotypes-characterized by their nasopharyngeal metagenome, virus, and asthma genetic risk profiles. Compared with endotype A infants (who clinically resembled "classic" bronchiolitis), endotype E infants (characterized by a high abundance of H. influenzae, high proportion of RV-A and RV-C infections, and high asthma genetic risk) had a significantly higher risk for developing asthma (35.9% versus 16.7%; ORadj, 2.24; 95%CI, 1.02-4.97; p=0.046). The pathway analysis showed that endotype E had enriched microbial pathways (e.g., glycolysis, L-lysine, arginine metabolism) and host pathways (e.g., IFNs, IL-6/JAK/STAT3, fatty acids, MHC, and immunoglobin-related) (FDR<0.05). Additionally, endotype E had a significantly higher proportion of neutrophils (FDR<0.05). CONCLUSION: In this multi-center prospective cohort study of infant bronchiolitis, the clustering analysis of integrated-omics data identified biologically distinct endotypes with differential risks for developing asthma.

Race-Neutral Equations and Pulmonary Function Test Interpretation in Two Pediatric Cohorts.

OBJECTIVE: To investigate the changes in predicted lung function measurements when using race-neutral equations in children, based upon the new Global Lung Initiative (GLI) reference equations, utilizing a race-neutral approach in interpreting spirometry results compared with the 2012 race-specific GLI equations. STUDY DESIGN: We analyzed data from 2 multicenter prospective cohorts comprised of healthy children and children with history of severe (requiring hospitalization) bronchiolitis. Spirometry testing was done at the 6-year physical exam, and 677 tests were analyzed using new GLI Global and 2012 GLI equations. We used multivariable logistic regression, adjusted for age, height, and sex, to examine the association of race with the development of new impairment or increased severity (forced expiratory volume in the first second (FEV1) z-score ≤ -1.645) as per 2022 American Thoracic Society (ATS) guidelines. RESULTS: Compared with the race-specific GLI, the race-neutral equation yielded increases in the median forced expiratory volume in the first second and forced vital capacity (FVC) percent predicted in White children but decreases in these two measures in Black children. The prevalence of obstruction increased in White children by 21%, and the prevalence of possible restriction increased in Black children by 222%. Compared with White race, Black race was associated with increased prevalence of new impairments (aOR 7.59; 95%CI, 3.00-19.67; P < .001) and increased severity (aOR 35.40; 95%CI, 4.70-266.40; P = .001). Results were similar across both cohorts. CONCLUSIONS: As there are no biological justifications for the inclusion of race in spirometry interpretation, use of race-neutral spirometry reference equations led to an increase in both the prevalence and severity of respiratory impairments among Black children.

Respiratory Virus-Specific Nasopharyngeal Lipidome Signatures and Severity in Infants With Bronchiolitis: A Prospective Multicenter Study.

BACKGROUND: In infant bronchiolitis, recent evidence indicates that respiratory viruses (eg, respiratory syncytial virus [RSV], rhinovirus [RV]) contribute to the heterogeneity of disease severity. Of the potential pathobiological molecules, lipids serve as signaling molecules in airway inflammation. However, little is known about the role of the airway lipidome in between-virus heterogeneity and disease severity. METHODS: In this multicenter prospective study of 800 infants hospitalized for RSV or RV bronchiolitis, we analyzed nasopharyngeal lipidome data. We examined discriminatory lipids between RSV and RV infection and the association of the discriminatory lipids with bronchiolitis severity, defined by positive pressure ventilation (PPV) use. RESULTS: We identified 30 discriminatory nasopharyngeal lipid species and 8 fatty acids between RSV and RV infection. In the multivariable models adjusting for patient-level confounders, 8 lipid species-for example, phosphatidylcholine (18:2/18:2) (adjusted odds ratio [aOR], 0.23 [95% confidence interval {CI}, .11-.44]; false discovery rate [FDR] = 0.0004) and dihydroceramide (16:0) (aOR, 2.17 [95% CI, 1.12-3.96]; FDR = 0.04)-were significantly associated with the risk of PPV use. Additionally, 6 fatty acids-for example, eicosapentaenoic acid (aOR, 0.27 [95% CI, .11-.57]; FDR = 0.01)-were also significantly associated with the risk of PPV use. CONCLUSIONS: In infants hospitalized for bronchiolitis, the nasopharyngeal lipidome plays an important role in the pathophysiology of between-virus heterogeneity and disease severity.

Severe bronchiolitis profiles and risk of asthma development in Finnish children.

BACKGROUND: Recent studies support the existence of several entities under the clinical diagnosis of bronchiolitis. Among infants with severe bronchiolitis, distinct profiles have been differentially associated with development of recurrent wheezing by age 3 years. However, their associations with actual asthma remain unclear. OBJECTIVE: Our aim was to study the association between severe bronchiolitis profiles identified by using a clustering approach and childhood asthma. METHODS: Among 408 children (aged <2 years) hospitalized with bronchiolitis in Finland (in 2008-2010), latent class analysis identified 3 bronchiolitis profiles: profile A (47%), characterized by history of wheezing and/or eczema, wheezing during acute illness, and rhinovirus infection; profile BC (38%), characterized by severe illness and respiratory syncytial virus infection; and profile D (15%), characterized by the least severely ill children, including mostly children without wheezing and with rhinovirus infection. The children were followed by questionnaire 4 years later (86% [n = 348]) and through a nationwide social insurance database 7 years later (99% [n = 403]). Current asthma at the 4- and 7-year follow-ups was defined by regular use (according to parental report and medical records) or purchase (according to the social insurance database) of asthma control medication. RESULTS: Compared with risk of current asthma associated with profile BC, we observed increased risk of current asthma associated with profile A both at the 4-year follow-up (age- and sex-adjusted odds ratio = 2.42 [95% CI = 1.23-4.75]) and at the 7-year follow-up (age- and sex-adjusted odds ratio = 3.14 [95% CI = 1.33-7.42]). No significant difference in asthma risk was observed between profile D and profile BC. CONCLUSION: These longitudinal results provide further support for an association between a distinct severe bronchiolitis profile (characterized by a history of wheezing and/or eczema and rhinovirus infection) and risk of development childhood asthma.

Nasopharyngeal airway dual-transcriptome of infants with severe bronchiolitis and risk of childhood asthma: A multicenter prospective study.

BACKGROUND: Severe bronchiolitis (ie, bronchiolitis requiring hospitalization) during infancy is a major risk factor for childhood asthma. However, the exact mechanism linking these common conditions remains unclear. OBJECTIVES: This study sought to examine the integrated role of airway microbiome (both taxonomy and function) and host response in asthma development in this high-risk population. METHODS: This multicenter prospective cohort study of 244 infants with severe bronchiolitis (median age, 3 months) examined the infants' nasopharyngeal metatranscriptomes (microbiomes) and transcriptomes (hosts), as well as metabolomes at hospitalization. The longitudinal relationships investigated include (1) major bacterial species (Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis), (2) microbial function, and (3) host response with risks of developing asthma by age 6 years. RESULTS: First, the abundance of S pneumoniae was associated with greater risks of asthma (P = .01), particularly in infants with nonrhinovirus infection (Pinteraction = .04). Second, of 328 microbial functional pathways that are differentially enriched by asthma development, the top pathways (eg, fatty acid and glycolysis pathways; false discovery rate [FDR] < 1 × 10-12) were driven by these 3 major species (eg, positive association of S pneumoniae with glycolysis; FDR < 0.001). These microbial functional pathways were validated with the parallel metabolome data. Third, 104 transcriptome pathways were differentially enriched (FDR < .05)-for example, downregulated interferon-α and -γ and upregulated T-cell activation pathways. S pneumoniae was associated with most differentially expressed transcripts (eg, DAGLB; FDR < 0.05). CONCLUSIONS: By applying metatranscriptomic, transcriptomic, and metabolomic approaches to a multicenter cohort of infants with bronchiolitis, this study found an interplay between major bacterial species, their function, and host response in the airway, and their longitudinal relationship with asthma development.

Nasopharyngeal metatranscriptome profiles of infants with bronchiolitis and risk of childhood asthma: a multicentre prospective study.

BACKGROUND: Bronchiolitis is not only the leading cause of hospitalisation in US infants but also a major risk factor for asthma development. Growing evidence supports clinical heterogeneity within bronchiolitis. Our objectives were to identify metatranscriptome profiles of infant bronchiolitis, and to examine their relationship with the host transcriptome and subsequent asthma development. METHODS: As part of a multicentre prospective cohort study of infants (age <1 year) hospitalised for bronchiolitis, we integrated virus and nasopharyngeal metatranscriptome (species-level taxonomy and function) data measured at hospitalisation. We applied network-based clustering approaches to identify metatranscriptome profiles. We then examined their association with the host transcriptome at hospitalisation and risk for developing asthma. RESULTS: We identified five metatranscriptome profiles of bronchiolitis (n=244): profile A: virusRSVmicrobiomecommensals; profile B: virusRSV/RV-Amicrobiome H.influenzae ; profile C: virusRSVmicrobiome S.pneumoniae ; profile D: virusRSVmicrobiome M.nonliquefaciens ; and profile E: virusRSV/RV-Cmicrobiome M.catarrhalis . Compared with profile A, profile B infants were characterised by a high proportion of eczema, Haemophilus influenzae abundance and enriched virulence related to antibiotic resistance. These profile B infants also had upregulated T-helper 17 and downregulated type I interferon pathways (false discovery rate (FDR) <0.005), and significantly higher risk for developing asthma (17.9% versus 38.9%; adjusted OR 2.81, 95% CI 1.11-7.26). Likewise, profile C infants were characterised by a high proportion of parental asthma, Streptococcus pneumoniae dominance, and enriched glycerolipid and glycerophospholipid metabolism of the microbiome. These profile C infants had an upregulated RAGE signalling pathway (FDR <0.005) and higher risk of asthma (17.9% versus 35.6%; adjusted OR 2.49, 95% CI 1.10-5.87). CONCLUSIONS: Metatranscriptome and clustering analysis identified biologically distinct metatranscriptome profiles that have differential risks of asthma.

Late Pre-term Infants with Severe Bronchiolitis and Risk of Asthma by Age 5 Years.

In a prospective, multicenter cohort of infants hospitalized with bronchiolitis, we found infants born late pre-term (ie, gestational age of 34-36.9 weeks) had 35% higher odds of having asthma by age 5 years compared with infants born at full-term.

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.

Integrated-omics endotyping of infants with rhinovirus bronchiolitis and risk of childhood asthma.

BACKGROUND: Young children with rhinovirus (RV) infection-particularly bronchiolitis-are at high risk for developing childhood asthma. Emerging evidence suggests clinical heterogeneity within RV bronchiolitis. However, little is known about these biologically distinct subgroups (endotypes) and their relations with asthma risk. OBJECTIVE: We aimed to identify RV bronchiolitis endotypes and examine their longitudinal relations with asthma risk. METHODS: As part of a multicenter prospective cohort study of infants (age <12 months) hospitalized for bronchiolitis, we integrated clinical, RV species (RV-A, RV-B, and RV-C), nasopharyngeal microbiome (16S rRNA gene sequencing), cytokine, and metabolome (liquid chromatography tandem mass spectrometry) data collected at hospitalization. We then applied network and clustering approaches to identify bronchiolitis endotypes. We also examined their longitudinal association with risks of developing recurrent wheeze by age 3 years and asthma by age 5 years. RESULTS: Of 122 infants hospitalized for RV bronchiolitis (median age, 4 months), we identified 4 distinct endotypes-mainly characterized by RV species, microbiome, and type 2 cytokine (T2) response: endotype A, virusRV-CmicrobiomemixedT2low; endotype B, virusRV-AmicrobiomeHaemophilusT2low; endotype C, virusRSV/RVmicrobiomeStreptococcusT2low; and endotype D, virusRV-CmicrobiomeMoraxellaT2high. Compared with endotype A infants, endotype D infants had a significantly higher rate of recurrent wheeze (33% vs 64%; hazard ratio, 2.23; 95% CI, 1.00-4.96; P = .049) and a higher risk for developing asthma (28% vs 59%; odds ratio, 3.74: 95% CI, 1.21-12.6; P = .03). CONCLUSIONS: Integrated-omics analysis identified biologically meaningful RV bronchiolitis endotypes in infants, such as one characterized by RV-C infection, Moraxella-dominant microbiota, and high T2 cytokine response, at higher risk for developing recurrent wheeze and asthma. This study should facilitate further research toward validating our inferences.

Detection of Respiratory Syncytial Virus or Rhinovirus Weeks After Hospitalization for Bronchiolitis and the Risk of Recurrent Wheezing.

BACKGROUND: In severe bronchiolitis, it is unclear if delayed clearance or sequential infection of respiratory syncytial virus (RSV) or rhinovirus (RV) is associated with recurrent wheezing. METHODS: In a 17-center severe bronchiolitis cohort, we tested nasopharyngeal aspirates (NPA) upon hospitalization and 3 weeks later (clearance swab) for respiratory viruses using PCR. The same RSV subtype or RV genotype in NPA and clearance swab defined delayed clearance (DC); a new RSV subtype or RV genotype at clearance defined sequential infection (SI). Recurrent wheezing by age 3 years was defined per national asthma guidelines. RESULTS: Among 673 infants, RSV DC and RV DC were not associated with recurrent wheezing, and RSV SI was rare. The 128 infants with RV SI (19%) had nonsignificantly higher risk of recurrent wheezing (hazard ratio [HR], 1.31; 95% confidence interval [CI], .95-1.80; P = .10) versus infants without RV SI. Among infants with RV at hospitalization, those with RV SI had a higher risk of recurrent wheezing compared to children without RV SI (HR, 2.49; 95% CI, 1.22-5.06; P = .01). CONCLUSIONS: Among infants with severe bronchiolitis, those with RV at hospitalization followed by a new RV infection had the highest risk of recurrent wheezing.

Serum Soluble Receptor for Advanced Glycation End Products in Infants With Bronchiolitis: Associations With Acute Severity and Recurrent Wheeze.

BACKGROUND: Although bronchiolitis contributes to substantial acute (eg, intensive care use) and chronic (eg, recurrent wheeze) morbidities in young children, the pathobiology remains uncertain. We examined the associations of serum soluble receptor for advanced glycation end products (sRAGE) with acute and chronic morbidities of bronchiolitis including recurrent wheeze. METHODS: A multicenter, multiyear, cohort study of infants hospitalized for bronchiolitis was analyzed. We measured the serum sRAGE level at hospitalization and its association with intensive care use (use of mechanical ventilation and/or admission to the intensive care unit) and development of recurrent wheeze by age 3 years. We performed causal mediation analysis to estimate indirect (mediation) and direct effects of sRAGE on recurrent wheeze. RESULTS: In 886 infants with bronchiolitis, the median age was 2.9 months. Overall, 15% underwent intensive care and 32% developed recurrent wheeze. In multivariable modeling adjusting for 11 confounders, a higher presenting sRAGE level was associated with lower risk of intensive care (odds ratio for each 1-log increment, 0.39; 95% confidence interval [CI], .16 -.91; P = .03) and significantly lower rate of recurrent wheeze (hazard ratio [HR], 0.58; 95% CI, .36 -.94; P = .03). In mediation analysis, the direct effect was significant (HR, 0.60; 95% CI, .37 -.97; P = .04), while the indirect effect was not (P = .30). CONCLUSIONS: Serum sRAGE levels were inversely associated with acute and chronic morbidities of bronchiolitis. The effect of sRAGE on development of recurrent wheeze is potentially driven through pathways other than acute severity of bronchiolitis.

A joint modeling approach for longitudinal microbiome data improves ability to detect microbiome associations with disease.

Changes in the composition of the microbiome over time are associated with myriad human illnesses. Unfortunately, the lack of analytic techniques has hindered researchers' ability to quantify the association between longitudinal microbial composition and time-to-event outcomes. Prior methodological work developed the joint model for longitudinal and time-to-event data to incorporate time-dependent biomarker covariates into the hazard regression approach to disease outcomes. The original implementation of this joint modeling approach employed a linear mixed effects model to represent the time-dependent covariates. However, when the distribution of the time-dependent covariate is non-Gaussian, as is the case with microbial abundances, researchers require different statistical methodology. We present a joint modeling framework that uses a negative binomial mixed effects model to determine longitudinal taxon abundances. We incorporate these modeled microbial abundances into a hazard function with a parameterization that not only accounts for the proportional nature of microbiome data, but also generates biologically interpretable results. Herein we demonstrate the performance improvements of our approach over existing alternatives via simulation as well as a previously published longitudinal dataset studying the microbiome during pregnancy. The results demonstrate that our joint modeling framework for longitudinal microbiome count data provides a powerful methodology to uncover associations between changes in microbial abundances over time and the onset of disease. This method offers the potential to equip researchers with a deeper understanding of the associations between longitudinal microbial composition changes and disease outcomes. This new approach could potentially lead to new diagnostic biomarkers or inform clinical interventions to help prevent or treat disease.

Integrated associations of nasopharyngeal and serum metabolome with bronchiolitis severity and asthma: A multicenter prospective cohort study.

BACKGROUND: While infant bronchiolitis contributes to substantial acute (eg, severity) and chronic (eg, asthma development) morbidities, its pathobiology remains uncertain. We examined the integrated relationships of local (nasopharyngeal) and systemic (serum) responses with bronchiolitis morbidities. METHODS: In a multicenter prospective cohort study of infants hospitalized for bronchiolitis, we applied a network analysis approach to identify distinct networks (modules)-clusters of densely interconnected metabolites-of the nasopharyngeal and serum metabolome. We examined their individual and integrated relationships with acute severity (defined by positive pressure ventilation [PPV] use) and asthma development by age 5 years. RESULTS: In 140 infants, we identified 285 nasopharyngeal and 639 serum metabolites. Network analysis revealed 7 nasopharyngeal and 8 serum modules. At the individual module level, nasopharyngeal-amino acid, tricarboxylic acid (TCA) cycle, and carnitine modules were associated with higher risk of PPV use (r > .20; P < .001), while serum-carnitine, amino acid, and glycerophosphorylcholine (GPC)/glycerophosphorylethanolamine (GPE) modules were associated with lower risk (all r < -.20; P < .05). The integrated analysis for PPV use revealed consistent findings-for example, nasopharyngeal-TCA (adjOR: 2.87, 95% CI: 1.68-12.2) and serum-GPC/GPE (adjOR: 0.54, 95% CI: 0.38-0.80) modules-and an additional module-serum-glucose-alanine cycle module (adjOR: 0.69, 95% CI: 0.56-0.86). With asthma risk, there were no individual associations, but there were integrated associations (eg, nasopharyngeal-carnitine module; adjOR: 1.48, 95% CI: 1.11-1.99). CONCLUSION: In infants with bronchiolitis, we found integrated relationships of local and systemic metabolome networks with acute and chronic morbidity. Our findings advance research into the complex interplay among respiratory viruses, local and systemic response, and disease pathobiology in infants with bronchiolitis.

Increased Moraxella and Streptococcus species abundance after severe bronchiolitis is associated with recurrent wheezing.

BACKGROUND: The role of the airway microbiome in the development of recurrent wheezing and asthma remains uncertain, particularly in the high-risk group of infants hospitalized for bronchiolitis. OBJECTIVE: We sought to examine the relation of the nasal microbiota at bronchiolitis-related hospitalization and 3 later points to the risk of recurrent wheezing by age 3 years. METHODS: In 17 US centers researchers collected clinical data and nasal swabs from infants hospitalized for bronchiolitis. Trained parents collected nasal swabs 3 weeks after hospitalization and, when healthy, during the summer and 1 year after hospitalization. We applied 16S rRNA gene sequencing to all nasal swabs. We used joint modeling to examine the relation of longitudinal nasal microbiota abundances to the risk of recurrent wheezing. RESULTS: Among 842 infants hospitalized for bronchiolitis, there was 88% follow-up at 3 years, and 31% had recurrent wheezing. The median age at enrollment was 3.2 months (interquartile range, 1.7-5.8 months). In joint modeling analyses adjusting for 16 covariates, including viral cause, a 10% increase in relative abundance of Moraxella or Streptococcus species 3 weeks after day 1 of hospitalization was associated with an increased risk of recurrent wheezing (hazard ratio [HR] of 1.38 and 95% high-density interval [HDI] of 1.11-1.85 and HR of 1.76 and 95% HDI of 1.13-3.19, respectively). Increased Streptococcus species abundance the summer after hospitalization was also associated with a greater risk of recurrent wheezing (HR, 1.76; 95% HDI, 1.15-3.27). CONCLUSIONS: Enrichment of Moraxella or Streptococcus species after bronchiolitis hospitalization was associated with recurrent wheezing by age 3 years, possibly providing new avenues to ameliorate the long-term respiratory outcomes of infants with severe bronchiolitis.

Respiratory viruses are associated with serum metabolome among infants hospitalized for bronchiolitis: A multicenter study.

BACKGROUND: Bronchiolitis is the leading cause of infant hospitalizations in the United States. Growing evidence supports the heterogeneity of bronchiolitis. However, little is known about the interrelationships between major respiratory viruses (and their species), host systemic metabolism, and disease pathobiology. METHODS: In an ongoing multicenter prospective cohort study, we profiled the serum metabolome in 113 infants (63 RSV-only, 21 RV-A, and 29 RV-C) hospitalized with bronchiolitis. We identified serum metabolites that are most discriminatory in the RSV-RV-A and RSV-RV-C comparisons using sparse partial least squares discriminant analysis. We then investigated the association between discriminatory metabolites with acute and chronic outcomes. RESULTS: In 113 infants with bronchiolitis, we measured 639 metabolites. Serum metabolomic profiles differed in both comparisons (Ppermutation  < 0.05). In the RSV-RV-A comparison, we identified 30 discriminatory metabolites, predominantly in lipid metabolism pathways (eg, sphingolipids and carnitines). In multivariable models, these metabolites were significantly associated with the risk of clinical outcomes (eg, tricosanoyl sphingomyelin, OR for recurrent wheezing at age of 3 years = 1.50; 95% CI: 1.05-2.15). In the RSV-RV-C comparison, the discriminatory metabolites were also primarily involved in lipid metabolism (eg, glycerophosphocholines [GPCs], 12,13-diHome). These metabolites were also significantly associated with the risk of outcomes (eg, 1-stearoyl-2-linoleoyl-GPC, OR for positive pressure ventilation use during hospitalization = 0.47; 95% CI: 0.28-0.78). CONCLUSION: Respiratory viruses and their species had distinct serum metabolomic signatures that are associated with differential risks of acute and chronic morbidities of bronchiolitis. Our findings advance research into the complex interrelations between viruses, host systemic response, and bronchiolitis pathobiology.

Severe bronchiolitis profiles and risk of recurrent wheeze by age 3 years.

BACKGROUND: A better understanding of bronchiolitis heterogeneity might help clarify its relationship with the development of recurrent wheezing and asthma. OBJECTIVES: We sought to identify severe bronchiolitis profiles using a clustering approach and to investigate for the first time their association with allergy/inflammatory biomarkers, nasopharyngeal microbiota, and development of recurrent wheezing by age 3 years. METHODS: We analyzed data from a prospective, 17-center US cohort study of 921 infants (age <1 year) hospitalized with bronchiolitis (2011-2014 winters) with posthospitalization follow-up. Severe bronchiolitis profiles at baseline (hospitalization) were determined by using latent class analysis based on clinical factors and viral etiology. Blood biomarkers and nasopharyngeal microbiota profiles were determined by using samples collected within 24 hours of hospitalization. Recurrent wheezing by age 3 years was defined based on parental report of breathing problem episodes after discharge. RESULTS: Three severe bronchiolitis profiles were identified: profile A (15%), which was characterized by a history of breathing problems/eczema during infancy and non-respiratory syncytial virus (mostly rhinovirus) infection; profile B (49%), which has the largest probability of respiratory syncytial virus infection and resembled classic respiratory syncytial virus-induced bronchiolitis; and profile C (36%), which was composed of the most severely ill group. Profile A infants had higher eosinophil counts, higher cathelicidin levels, and increased proportions of Haemophilus-dominant or Moraxella-dominant microbiota profiles. Compared with profile B, we observed significantly increased risk of recurrent wheezing in children with profile A (hazard ratio, 2.64; 95% CI, 1.90-3.68) and, to a lesser extent, with profile C (hazard ratio, 1.51; 95% CI, 1.14-2.01). CONCLUSION: Although longer follow-up is needed, our results might help identify, among children hospitalized for bronchiolitis, subgroups with particularly increased risk of asthma.

Serum Metabolome Is Associated With the Nasopharyngeal Microbiota and Disease Severity Among Infants With Bronchiolitis.

BACKGROUND: Emerging evidence suggests relationships between the nasopharyngeal metabolome and both the microbiota and severity of bronchiolitis. However, the influence of host systemic metabolism on disease pathobiology remains unclear. We aimed to examine metabolome profiles and their association with more-severe disease, defined by use of positive pressure ventilation (PPV), in infants hospitalized for bronchiolitis. METHODS: In 140 infants with bronchiolitis, metabolomic profiling was performed on serum; samples from 70 were in a training data set, and samples from 70 were in an independent test data set. We also profiled the nasopharyngeal airway microbiota and examined its association with the serum metabolites. RESULTS: Serum metabolome profiles differed by bronchiolitis severity (P < .001). In total, 20 metabolites in the training data set were significantly associated with the risk of PPV, of which 18 remained significant following adjustment for confounders (false-discovery rate [FDR], < 0.10). Phosphatidylcholine metabolites were associated with higher risks of PPV use, while metabolites from the plasmalogen subpathway were associated with lower risks. The test data set validated these findings (FDR < 0.05). Streptococcus abundance was positively associated with metabolites that are associated with higher risks of PPV. CONCLUSIONS: Serum metabolomic signatures were associated with both the nasopharyngeal microbiota and the severity of bronchiolitis. Our findings advance research into the complex interrelations between the airway microbiome, host systemic response, and pathobiology of bronchiolitis.

Haemophilus-Dominant Nasopharyngeal Microbiota Is Associated With Delayed Clearance of Respiratory Syncytial Virus in Infants Hospitalized for Bronchiolitis.

The relation of nasopharyngeal microbiota to the clearance of respiratory syncytial virus (RSV) in infants hospitalized for bronchiolitis is not known. In a multicenter cohort, we found that 106 of 557 infants (19%) hospitalized with RSV bronchiolitis had the same RSV subtype 3 weeks later (ie, delayed clearance of RSV). Using 16S ribosomal RNA gene sequencing and a clustering approach, infants with a Haemophilus-dominant microbiota profile at hospitalization were more likely than those with a mixed profile to have delayed clearance, after adjustment for 11 factors, including viral load. Nasopharyngeal microbiota composition is associated with delayed RSV clearance.

Respiratory Syncytial Virus and Rhinovirus Bronchiolitis Are Associated With Distinct Metabolic Pathways.

Background: Bronchiolitis, the leading cause of hospitalization among infants in the United States, is most commonly caused by respiratory syncytial virus (RSV), followed by rhinovirus (RV). Conventional perception is that bronchiolitis is a single entity, albeit with different viral etiologies and degrees of severity. Methods: We conducted a cross-sectional study of nasopharyngeal aspirates from 106 infants hospitalized with bronchiolitis due to either RSV only (80 patients) or RV only (26 patients). We performed metabolomics analysis and 16S ribosomal RNA gene sequencing on all samples and metagenomic sequencing on 58 of 106 samples. Results: Infants with RSV-only and RV-only infections had significantly different nasopharyngeal metabolome profiles (P < .001) and bacterial metagenome profiles (P < .05). RSV-only infection was associated with metabolites from a range of pathways and with a microbiome dominated by Streptococcus pneumoniae. By contrast, RV-only infection was associated with increased levels of essential and nonessential N-acetyl amino acids and with a high relative abundance of Haemophilus influenzae. These co-occurring species were associated with driving the bacterially derived metabolic pathways. Multi-omic analysis showed that both the virus and the microbiome were significantly associated with metabolic function in infants hospitalized with bronchiolitis. Conclusion: Although replication of these findings is necessary, they highlight that bronchiolitis is not a uniform disease between RSV and RV infections, a result with future implications for prevention and treatment.

Vitamin D Status at the Time of Hospitalization for Bronchiolitis and Its Association with Disease Severity.

OBJECTIVE: To investigate the association between circulating 25-hydroxyvitamin D [25(OH)D] status at admission and disease severity among infants hospitalized for bronchiolitis and to determine whether the association differs by the form of 25(OH)D-total, bioavailable or free 25(OH)D. STUDY DESIGN: We conducted a 17-center prospective cohort study of 1016 US infants <12 months old hospitalized with bronchiolitis. Vitamin D status was defined by total 25(OH)D levels, and by calculated levels of bioavailable and free 25(OH)D. Bronchiolitis severity was defined by requirement for intensive care and hospital length-of-stay (LOS). Logistic and Poisson regression were used for unadjusted and multivariable analyses. RESULTS: The median age of hospitalized infants was 3.2 months (IQR 1.6-6.0). The median total 25(OH)D was 26.5 ng/mL (IQR 18.0-33.1); 298 (29%) infants had total 25(OH)D <20 ng/mL. In multivariable models, infants with total 25(OH)D <20 ng/mL had higher risk of requiring intensive care (aOR 1.72, 95% CI 1.12-2.64) and longer LOS (adjusted rate ratio 1.39, 95% CI 1.17-1.65) compared with infants with total 25(OH)D ≥30 ng/mL. Infants with the lowest tertile of bioavailable 25(OH)D, compared with those with the highest tertile, had longer LOS (adjusted rate ratio 1.32, 95% CI 1.07-1.62); admission to the intensive care unit was not statistically significant in the adjusted model (aOR 1.39, 95% CI 0.96-2.64). Free 25(OH)D level was not associated with severity of bronchiolitis in either unadjusted or adjusted models. CONCLUSION: In a large, multicenter cohort of US infants hospitalized for bronchiolitis, infants with total 25(OH)D <20 ng/mL had increased risk of intensive care and longer hospital LOS.