Metabolome subtyping of severe bronchiolitis in infancy and risk of childhood asthma

Microbiome modifications by steroids during viral exacerbation of asthma and in healthy mice

In the present studies, the assessment of how viral exacerbation of asthmatic responses with and without pulmonary steroid treatment alters the microbiome in conjunction with immune responses presents striking data. The overall findings identify that although steroid treatment of allergic animals diminished the severity of the respiratory syncytial virus (RSV)-induced exacerbation of airway function and mucus hypersecretion, there were local increases in IL-17 expression. Analysis of the lung and gut microbiome suggested that there are differences in RSV exacerbation that are further altered by fluticasone (FLUT) treatment. Using metagenomic inference software, PICRUSt2, we were able to predict that the metabolite profile produced by the changed gut microbiome was significantly different with multiple metabolic pathways and associated with specific treatments with or without FLUT. Importantly, measuring plasma metabolites in an unbiased manner, our data indicate that there are significant changes associated with chronic allergen exposure, RSV exacerbation, and FLUT treatment that are reflective of responses to the disease and treatment. In addition, the changes in metabolites appeared to have contributions from both host and microbial pathways. To understand if airway steroids on their own altered lung and gut microbiome along with host responses to RSV infection, naïve animals were treated with lung FLUT before RSV infection. The naïve animals treated with FLUT before RSV infection demonstrated enhanced disease that corresponded to an altered microbiome and the related PICRUSt2 metagenomic inference analysis. Altogether, these findings set the foundation for identifying important correlations of severe viral exacerbated allergic disease with microbiome changes and the relationship of host metabolome with a potential for early life pulmonary steroid influence on subsequent viral-induced disease.NEW & NOTEWORTHY These studies outline a novel finding that airway treatment with fluticasone, a commonly used inhaled steroid, has significant effects on not only the local lung environment but also on the mucosal microbiome, which may have significant disease implications. The findings further provide data to support that pulmonary viral exacerbations of asthma with or without steroid treatment alter the lung and gut microbiome, which have an impact on the circulating metabolome that likely alters the trajectory of disease progression.

Association between nasopharyngeal airway lipidome signatures of infants with severe bronchiolitis and risk of recurrent wheeze: A prospective multicenter cohort study

BACKGROUND

Infants hospitalized for bronchiolitis are at high risk for developing recurrent wheeze in childhood. The role of airway lipids in the link between these two conditions remains unclear. This study aimed to identify the association between airway lipids in infants hospitalized for bronchiolitis and the development of recurrent wheeze, with a focus on immunoglobulin E (IgE) sensitization.

METHODS

In a multicenter prospective cohort study of 919 infants (age <1 year) hospitalized for bronchiolitis, we performed lipidomic profiling of nasopharyngeal airway specimens collected at hospitalization. We first identified lipid modules composed of highly correlated lipids by performing weighted correlation network analysis. We then examined the longitudinal association of those lipid modules with the rate of recurrent wheeze by age 3 years after discharge from hospitalization for bronchiolitis. We also examined the associations of lipid modules with IgE non-sensitized (i.e., neither sensitized at admission nor at age 3 years) and IgE-sensitized (i.e., sensitized at admission and/or at age 3 years) recurrent wheeze by age 3 years, respectively.

RESULTS

Our analysis identified 15 distinct lipid modules in the nasopharyngeal airway lipidome data. Overall, lipid modules composed of triacylglycerols (hazard ratio [HR] 1.78, 95% confidence interval [CI] 1.26-2.51, FDR < 0.01) and sphingolipids (HR 1.74, 95% CI 1.25-2.44, FDR <0.01) had the strongest associations with recurrent wheeze development. Stratification by IgE sensitization revealed differential associations. For example, the module composed of triacylglycerols was significantly associated with IgE non-sensitized recurrent wheeze, whereas the module composed of sphingolipids was significantly associated with IgE-sensitized recurrent wheeze (both FDR <0.05).

CONCLUSION

Distinct nasopharyngeal airway lipid modules are associated with recurrent wheeze development following severe bronchiolitis, with different patterns based on IgE sensitization status.

Integrated metabolomics and network pharmacology to reveal the mechanisms of Shexiang Baoxin pill against atherosclerosis

BACKGROUND

Atherosclerosis is a disease marked by the development of lipid lesions within the endothelium and continues to be a prominent contributor to global mortality. Shexiang Baoxin pill (SBP) has been employed in the management of numerous cardiovascular diseases, but the complex mechanisms by which it operates remain obscure. This research was conducted to determine the potential impact of SBP on atherosclerosis and the underlying regulatory mechanism involved.

METHOD

Network pharmacology was utilized to predict the key drug-disease targets, and a nontargeted metabolomic assay was applied to identify the key metabolites and metabolic pathways. A mouse atherosclerosis model was constructed to clarify the protective effect of SBP on atherosclerosis, and in vivo and in vitro tests were performed to verify the analysis results and clarify the mechanism through which SBP affects atherosclerosis.

RESULTS

The results show that SBP can exert a protective effect in vivo by decreasing lipid levels, plaque formation and endothelial damage. Network pharmacology and metabolomics revealed that MAPK3, AKT1 and STAT3 were the hub targets and that trimethylamine n-oxide (TMAO) was the pivotal metabolite. Due to the atherogenic effect of TMAO, the corresponding protective effect of SBP was investigated in vitro. SBP inhibited TMAO-induced endothelial cell apoptosis and oxidative stress and counteracted the upregulation of MAPK3, AKT1, and STAT3 expression. Molecular docking and enzymatic inhibition suggested that the active components of SBP could bind stably to key target proteins.

CONCLUSION

Taken together, based on the integrated metabolomics and network pharmacology, our findings suggest that SBP may be implicated in TMAO-induced atherosclerosis by affecting endothelial function and bile acid synthesis. We observed that SBP may ameliorate atherosclerosis by regulating TMAO levels through multiple pathways, which may provide a novel direction and insight for SBP involved in cardiovascular protection by mediating the gut-heart axis.

Early-life respiratory syncytial virus disease and long-term respiratory health

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection (LRTI), hospital admission, and mortality in children worldwide. Early-life RSV LRTI has also been associated with subsequent long-term respiratory sequelae, including recurrent LRTI, recurrent wheezing, asthma, and lung function impairment, and these effects can persist into adulthood as chronic respiratory disease. New preventive measures (maternal vaccine or long-acting monoclonal antibodies) have been licensed to reduce the burden of acute RSV LRTI in infants and children at high risk through passive immunisation. Studies of these RSV prevention products show high efficacy and effectiveness, particularly for preventing severe RSV LRTI, with implementation in many high-income countries, but limited access in low-income and middle-income countries (LMICs). These interventions might also reduce the risk of additional health outcomes and long-term morbidity. This Series paper provides the evidence for the long-term effects of early-life RSV disease, discusses mechanisms of disease development, and addresses the potential full public health value of prevention of RSV illness. Further research is needed to determine whether prevention of RSV LRTI or delay of RSV illness in early life might prevent or ameliorate the development of associated long-term respiratory disease. This potential further underscores the urgency for access and availability of new interventions to prevent early-life RSV LRTI in LMICs.

Urinary metabolomic profiles uncover metabolic pathways in children with asthma

OBJECTIVE

The prevalence of asthma has gradually increased worldwide in recent years, which has made asthma a global public health problem. However, due to its complexity and heterogeneity, there are a few academic debates on the pathogenic mechanism of asthma. The study of the pathogenesis of asthma through metabolomics has become a new research direction. We aim to uncover the metabolic pathway of children with asthma.

METHODS

Liquid chromatography (LC)-mass spectrometry (MS)-based metabolomic analysis was conducted to compare urine metabolic profiles between asthmatic children (n = 30) and healthy controls (n = 10).

RESULTS

Orthogonal projections to latent structures-discrimination analysis (OPLS-DA) showed that there were significant differences in metabolism between the asthma group and the control group with three different metabolites screened out, including traumatic acid, dodecanedioic acid, and glucobrassicin, and the levels of traumatic acid and dodecanedioic acid in the urine samples of asthmatic children were lower than those of healthy controls therein. Pathway enrichment analysis of differentially abundant metabolites suggested that α-linolenic acid metabolism was an asthma-related pathway.

CONCLUSIONS

This study suggests that there are significant metabolic differences in the urine of asthmatic children and healthy controls, and α-linolenic acid metabolic pathways may be involved in the pathogenesis of asthma.

Integrated-omics analysis with explainable deep networks on pathobiology of infant bronchiolitis

Bronchiolitis is the leading cause of infant hospitalization. However, the molecular networks driving bronchiolitis pathobiology remain unknown. Integrative molecular networks, including the transcriptome and metabolome, can identify functional and regulatory pathways contributing to disease severity. Here, we integrated nasopharyngeal transcriptome and metabolome data of 397 infants hospitalized with bronchiolitis in a 17-center prospective cohort study. Using an explainable deep network model, we identified an omics-cluster comprising 401 transcripts and 38 metabolites that distinguishes bronchiolitis severity (test-set AUC, 0.828). This omics-cluster derived a molecular network, where innate immunity-related metabolites (e.g., ceramides) centralized and were characterized by toll-like receptor (TLR) and NF-κB signaling pathways (both FDR < 0.001). The network analyses identified eight modules and 50 existing drug candidates for repurposing, including prostaglandin I2 analogs (e.g., iloprost), which promote anti-inflammatory effects through TLR signaling. Our approach facilitates not only the identification of molecular networks underlying infant bronchiolitis but the development of pioneering treatment strategies.

Nasopharyngeal airway long noncoding RNAs of infants with bronchiolitis and subsequent risk of developing childhood asthma

BACKGROUND

Severe bronchiolitis (ie, bronchiolitis requiring hospitalization) during infancy is a major risk factor for developing childhood asthma. However, the biological mechanisms linking these 2 conditions remain unclear.

OBJECTIVE

We sought to investigate the longitudinal relationship between nasopharyngeal airway long noncoding RNA (lncRNA) in infants with severe bronchiolitis and subsequent asthma development.

METHODS

In this multicenter prospective cohort study of infants with severe bronchiolitis, we performed RNA sequencing of nasopharyngeal airway lncRNAs at index hospitalization. First, we identified differentially expressed lncRNAs (DE-lncRNAs) associated with asthma development by age 6 years. Second, we investigated the associations of DE-lncRNAs with asthma-related clinical characteristics. Third, to characterize the function of DE-lncRNAs, we performed pathway analysis for mRNA targeted by DE-lncRNAs. Finally, we examined the associations of DE-lncRNAs with nasal cytokines at index hospitalization.

RESULTS

Among 343 infants with severe bronchiolitis (median age, 3 months), we identified 190 DE-lncRNAs (false-discovery rate [FDR] < 0.05) associated with asthma development (eg, LINC02145, RAMP2-AS1, and PVT1). These DE-lncRNAs were associated with asthma-related clinical characteristics (FDR < 0.05), for example, respiratory syncytial virus or rhinovirus infection, infant eczema, and IgE sensitization. Furthermore, DE-lncRNAs were characterized by asthma-related pathways, including mitogen-activated protein kinase, FcɛR, and phosphatidylinositol 3-kinase (PI3K)-protein kinase B signaling pathways (FDR < 0.05). These DE-lncRNAs were also associated with nasal cytokines (eg, IL-1β, IL-4, and IL-13; FDR < 0.05).

CONCLUSIONS

In a multicenter cohort study of infants with severe bronchiolitis, we identified nasopharyngeal airway lncRNAs associated with childhood asthma development, characterized by asthma-related clinical characteristics, asthma-related pathways, and nasal cytokines. Our approach identifies lncRNAs underlying the bronchiolitis-asthma link and facilitates the early identification of infants at high risk of subsequent asthma development.

Update on asthma biology

This is an exciting time to be conducting asthma research. The recent development of targeted asthma biologics has validated the power of basic research to discover new molecules amenable to therapeutic intervention. Advances in high-throughput sequencing are providing a wealth of "omics" data about genetic and epigenetic underpinnings of asthma, as well as about new cellular interacting networks and potential endotypes in asthma. Airway epithelial cells have emerged not only as key sensors of the outside environment but also as central drivers of dysregulated mucosal immune responses in asthma. Emerging data suggest that the airway epithelium in asthma remembers prior encounters with environmental exposures, resulting in potentially long-lasting changes in structure and metabolism that render asthmatic individuals susceptible to subsequent exposures. Here we summarize recent insights into asthma biology, focusing on studies using human cells or tissue that were published in the past 2 years. The studies are organized thematically into 6 content areas to draw connections and spur future research (on genetics and epigenetics, prenatal and early-life origins, microbiome, immune and inflammatory pathways, asthma endotypes and biomarkers, and lung structural alterations). We highlight recent studies of airway epithelial dysfunction and response to viral infections and conclude with a framework for considering how bidirectional interactions between alterations in airway structure and mucosal immunity can lead to sustained lung dysfunction in asthma.

Infant Bronchiolitis Endotypes and the Risk of Developing Childhood Asthma: Lessons From Cohort Studies

Severe bronchiolitis (i.e., bronchiolitis requiring hospitalization) during infancy is a heterogeneous condition associated with a high risk of developing childhood asthma. Yet, the exact mechanisms underlying the bronchiolitis-asthma link remain uncertain. Birth cohort studies have reported this association at the population level, including only small groups of patients with a history of bronchiolitis, and have attempted to identify the underlying biological mechanisms. Although this evidence has provided valuable insights, there are still unanswered questions regarding severe bronchiolitis-asthma pathogenesis. Recently, a few bronchiolitis cohort studies have attempted to answer these questions by applying unbiased analytical approaches to biological data. These cohort studies have identified novel bronchiolitis subtypes (i.e., endotypes) at high risk for asthma development, representing essential and enlightening evidence. For example, one distinct severe respiratory syncytial virus (RSV) bronchiolitis endotype is characterized by the presence of Moraxella catarrhalis and Streptococcus pneumoniae, higher levels of type I/II IFN expression, and changes in carbohydrate metabolism in nasal airway samples, and is associated with a high risk for childhood asthma development. Although these findings hold significance for the design of future studies that focus on childhood asthma prevention, they require validation. However, this scoping review puts the above findings into clinical context and emphasizes the significance of future research in this area aiming to offer new bronchiolitis treatments and contribute to asthma prevention.

Purine degradation pathway metabolites at birth and the risk of lower respiratory tract infections in infancy

Background

Lower respiratory tract infections (LRTIs) are the leading cause of infant morbidity and mortality worldwide, and altered metabolite production is recognised as a critical factor in LRTI pathogenesis.

Methods

This study aimed to identify prenatal metabolic changes associated with LRTI risk in infancy, using liquid chromatography-mass spectrometry unbiased metabolomics analysis on cord blood from 810 full-term newborns.

Results

We identified 22 compounds linked to LRTIs in infancy, enriched for purine degradation pathway (PDP) metabolites. High cord blood PDP metabolites, including xanthine, hypoxanthine, xanthosine and inosine, were linked to reduced LRTI risk during infancy. Notably, a low xanthine to uric acid ratio at birth predicted a four-fold increased LRTI risk.

Conclusion

This study is the first to reveal that high cord blood PDP metabolites identify newborns at lower LRTI risk, stratifying disease risk at birth. Moreover, our results prompt further study on PDP enzymes as pharmacological targets to decrease LRTI morbidity and mortality for at-risk newborns.

Reduced Serum Brain-Derived Neurotrophic Factor in Infants Affected by Severe Bronchiolitis

BACKGROUND

Bronchiolitis is an acute viral infection of the lower respiratory tract, typical of infants in their first year of life and causing hypoxia in the most serious cases. Bronchiolitis recognizes various demographic risk factors that are associated with greater clinical severity; however, no laboratory factors are yet able to correlate with the clinical severity. Neurotrophins as Brain-Derived Neurotrophic Factor (BDNF) are mediators of neuronal plasticity. BDNF is constitutively expressed in smooth muscle cells and epithelium of the lower respiratory tract, and as it is released during inflammatory conditions, serum levels may have a relevant role in the prognosis of infants with bronchiolitis.

OBJECTIVE

In the present pilot study, we aimed to disclose the presence of serum BDNF in infants hospitalized with bronchiolitis at discharge as a disease severity indicator.

METHODS AND RESULTS

Serum BDNF, measured at hospital discharge, was significantly lower in severe bronchiolitis (expressed as O2-supplemented infants). Furthermore, no changes were disclosed for the Tropomyosin receptor kinase B, the main BDNF receptor and neurofilament light chain, a biomarker of neuronal degeneration.

CONCLUSION

Low serum BDNF in infants with severe bronchiolitis could be associated with a higher utilization by lung cells or with an altered production by lung cells. Therefore, further research is required to study if a decreased production or increased consumption of this biomarker is at the base of the above-mentioned findings.

The re-emerging role of linoleic acid in paediatric asthma

Asthma is the most common chronic disease within the paediatric population. Although it is multifactorial, its onset may be linked to early-life exposures with subsequent impact on immune system development. Microbial and dietary metabolic products have been implicated in the development and exacerbation of paediatric asthma. Linoleic acid is the most common omega-6 polyunsaturated fatty acid in the Western diet. In this review, we summarise the literature regarding the involvement of linoleic acid in the development of and its impact on existing paediatric asthma. First, we summarise the existing knowledge surrounding the relationship between human microbial metabolism and allergic diseases in children. Next, we examine cellular or animal model-based mechanistic studies that investigated the impact of dietary- and microbial-derived linoleic acid metabolites on asthma. Finally, we review the literature investigating the impact of linoleic acid metabolites on the development and exacerbation of childhood asthma. While there is conflicting evidence, there is growing support for a role of linoleic acid in the onset and pathophysiology of asthma. We recommend that additional cellular, animal, and longitudinal studies are performed that target linoleic acid and its metabolites.

Epigenome-wide association analysis of infant bronchiolitis severity: a multicenter prospective cohort study

Bronchiolitis is the most common lower respiratory infection in infants, yet its pathobiology remains unclear. Here we present blood DNA methylation data from 625 infants hospitalized with bronchiolitis in a 17-center prospective study, and associate them with disease severity. We investigate differentially methylated CpGs (DMCs) for disease severity. We characterize the DMCs based on their association with cell and tissues types, biological pathways, and gene expression. Lastly, we also examine the relationships of severity-related DMCs with respiratory and immune traits in independent cohorts. We identify 33 DMCs associated with severity. These DMCs are differentially methylated in blood immune cells. These DMCs are also significantly enriched in multiple tissues (e.g., lung) and cells (e.g., small airway epithelial cells), and biological pathways (e.g., interleukin-1-mediated signaling). Additionally, these DMCs are associated with respiratory and immune traits (e.g., asthma, lung function, IgE levels). Our study suggests the role of DNA methylation in bronchiolitis severity.

Application of Asthma Prediction Tools in a Cohort of Infants with Severe Bronchiolitis

Background: Severe bronchiolitis is a strong childhood asthma risk factor. Early and accurate asthma prediction is key. We applied the Asthma Predictive Index (API), the modified Asthma Predictive Index (mAPI), and the Pediatric Asthma Risk Score (PARS) in a cohort of high-risk infants to predict asthma at age 6 years. Methods: We conducted a 17-center cohort of infants (age <1 year) hospitalized with severe bronchiolitis during 2011-2014. We used only infancy data to predict asthma at age 6 years. Results: The prevalence of parent-reported asthma at age 6 years was 328/880 (37%). The prevalences of a positive index/score for stringent and loose API, mAPI, and PARS were 21%, 51%, 11%, and 34%, respectively. Area under the receiver operating characteristic curves [95% confidence interval (CI)] ranged from 0.57 (95% CI 0.55-0.60) for mAPI to 0.66 (95% CI 0.63-0.70) for PARS. Conclusions: An asthma prediction tool for high-risk infants is needed to identify those who would benefit most from asthma prevention interventions.

Childhood asthma phenotypes and endotypes: a glance into the mosaic

BACKGROUND

Asthma is an inflammatory lung disease that constitutes the most common noncommunicable chronic disease in childhood. Childhood asthma shows large heterogeneity regarding onset of disease, symptoms, severity, prognosis, and response to therapy.

MAIN BODY

Evidence suggests that this variability is due to distinct pathophysiological mechanisms, which has led to an exhaustive research effort to understand and characterize these distinct entities currently designated as "endotypes." Initially, studies focused on identifying specific groups using clinical variables yielding different "clinical phenotypes." In addition, the identification of specific patterns based on inflammatory cell counts and cytokine data has resulted in "inflammatory endotypes." More recently, an increasing number of molecular data from high-throughput technology ("omics" data) have allowed to investigate more complex "molecular endotypes."

CONCLUSION

A better definition and comprehension of childhood asthma heterogeneity is key for improving diagnosis and treatment. This review aims at summarizing the current knowledge on this topic and discusses some limitations in their application as well as recommendations for future studies.

Metabolomics Applied to Pediatric Asthma: What Have We Learnt in the Past 10 Years?

Background: Asthma is the most common chronic condition in children. It is a complex non-communicable disease resulting from the interaction of genetic and environmental factors and characterized by heterogeneous underlying molecular mechanisms. Metabolomics, as with the other omic sciences, thanks to the joint use of high-throughput technologies and sophisticated multivariate statistical methods, provides an unbiased approach to study the biochemical-metabolic processes underlying asthma. The aim of this narrative review is the analysis of the metabolomic studies in pediatric asthma published in the past 10 years, focusing on the prediction of asthma development, endotype characterization and pharmaco-metabolomics. Methods: A total of 43 relevant published studies were identified searching the MEDLINE/Pubmed database, using the following terms: "asthma" AND "metabolomics". The following filters were applied: language (English), age of study subjects (0-18 years), and publication date (last 10 years). Results and Conclusions: Several studies were identified within the three areas of interest described in the aim, and some of them likely have the potential to influence our clinical approach in the future. Nonetheless, further studies are needed to validate the findings and to assess the role of the proposed biomarkers as possible diagnostic or prognostic tools to be used in clinical practice.

Nasal airway microRNA profiling of infants with severe bronchiolitis and risk of childhood asthma: a multicentre prospective study

BACKGROUND

Severe bronchiolitis (i.e. bronchiolitis requiring hospitalisation) during infancy is a major risk factor for childhood asthma. However, the exact mechanism linking these common conditions remains unclear. We examined the longitudinal relationship between nasal airway miRNAs during severe bronchiolitis and the risk of developing asthma.

METHODS

In a 17-centre prospective cohort study of infants with severe bronchiolitis, we sequenced their nasal microRNA at hospitalisation. First, we identified differentially expressed microRNAs (DEmiRNAs) associated with the risk of developing asthma by age 6 years. Second, we characterised the DEmiRNAs based on their association with asthma-related clinical features, and expression level by tissue and cell types. Third, we conducted pathway and network analyses by integrating DEmiRNAs and their mRNA targets. Finally, we investigated the association of DEmiRNAs and nasal cytokines.

RESULTS

In 575 infants (median age 3 months), we identified 23 DEmiRNAs associated with asthma development (e.g. hsa-miR-29a-3p; false discovery rate (FDR) <0.10), particularly in infants with respiratory syncytial virus infection (FDR for the interaction <0.05). These DEmiRNAs were associated with 16 asthma-related clinical features (FDR <0.05), e.g. infant eczema and corticosteroid use during hospitalisation. In addition, these DEmiRNAs were highly expressed in lung tissue and immune cells (e.g. T-helper cells, neutrophils). Third, DEmiRNAs were negatively correlated with their mRNA targets (e.g. hsa-miR-324-3p/IL13), which were enriched in asthma-related pathways (FDR <0.05), e.g. toll-like receptor, PI3K-Akt and FcɛR signalling pathways, and validated by cytokine data.

CONCLUSION

In a multicentre cohort of infants with severe bronchiolitis, we identified nasal miRNAs during illness that were associated with major asthma-related clinical features, immune response, and risk of asthma development.

Etiologies of Acute Bronchiolitis in Children at Risk for Asthma, with Emphasis on the Human Rhinovirus Genotyping Protocol

This research aims to determine acute bronchiolitis' causative virus(es) and establish a viable protocol to classify the Human Rhinovirus (HRV) species. During 2021-2022, we included children 1-24 months of age with acute bronchiolitis at risk for asthma. The nasopharyngeal samples were taken and subjected to a quantitative polymerase chain reaction (qPCR) in a viral panel. For HRV-positive samples, a high-throughput assay was applied, directing the VP4/VP2 and VP3/VP1 regions to confirm species. BLAST searching, phylogenetic analysis, and sequence divergence took place to identify the degree to which these regions were appropriate for identifying and differentiating HRV. HRV ranked second, following RSV, as the etiology of acute bronchiolitis in children. The conclusion of the investigation of all available data in this study distributed sequences into 7 HRV-A, 1 HRV-B, and 7 HRV-C types based on the VP4/VP2 and VP3/VP1 sequences. The nucleotide divergence between the clinical samples and the corresponding reference strains was lower in the VP4/VP2 region than in the VP3/VP1 region. The results demonstrated the potential utility of the VP4/VP2 region and the VP3/VP1 region for differentiating HRV genotypes. Confirmatory outcomes were yielded, indicating how nested and semi-nested PCR can establish practical ways to facilitate HRV sequencing and genotyping.

Immunoglobulin E-virus phenotypes of infant bronchiolitis and risk of childhood asthma

Background

Bronchiolitis is the leading cause of infant hospitalization in U.S. and is associated with increased risk for childhood asthma. Immunoglobulin E (IgE) not only plays major roles in antiviral immune responses and atopic predisposition, but also offers a potential therapeutic target.

Objective

We aimed to identify phenotypes of infant bronchiolitis by using total IgE (tIgE) and virus data, to determine their association with asthma development, and examine their biological characteristics.

Methods

In a multicenter prospective cohort study of 1,016 infants (age <1 year) hospitalized for bronchiolitis, we applied clustering approaches to identify phenotypes by integrating tIgE and virus (respiratory syncytial virus [RSV], rhinovirus [RV]) data at hospitalization. We examined their longitudinal association with the risk of developing asthma by age 6 years and investigated their biological characteristics by integrating the upper airway mRNA and microRNA data in a subset (n=182).

Results

In infants hospitalized for bronchiolitis, we identified 4 phenotypes: 1) tIgE^lowvirus^RSV-high, 2) tIgE^lowvirus^RSV-low/RV, 3) tIgE^highvirus^RSV-high, and 4) tIgE^highvirus^RSV-low/RV phenotypes. Compared to phenotype 1 infants (resembling "classic" bronchiolitis), phenotype 4 infants (tIgE^highvirus^RSV-low/RV) had a significantly higher risk for developing asthma (19% vs. 43%; adjOR, 2.93; 95% CI, 1.02-8.43; P=.046). Phenotypes 3 and 4 (tIgE^high) had depleted type I interferon and enriched antigen presentation pathways; phenotype 4 also had depleted airway epithelium structure pathways.

Conclusions

In this multicenter cohort, tIgE-virus clustering identified distinct phenotypes of infant bronchiolitis with differential risks of asthma development and unique biological characteristics.

Integration of transcriptomics and metabolomics to reveal the effect of ginsenoside Rg3 on allergic rhinitis in mice

Increasing studies have demonstrated that ginsenoside Rg3 (Rg3) plays an important role in the prevention and treatment of various diseases, including allergic lower airway inflammation such as asthma. To investigate the role of Rg3 in allergic upper airway disease, the effect and therapeutic mechanism of Rg3 in allergic rhinitis (AR) were studied. Ovalbumin-induced AR model mice were intragastrically administered with Rg3. Nasal symptoms, levels of IgE, IL-4, IL-5, IL-13, SOD and MDA in serum, and histopathological analysis of nasal mucosa were used to evaluate the effect of Rg3 on ameliorating AR in mice. Moreover, nasal mucosa samples from the normal control group, AR model group and high dosage of Rg3 were collected to perform omics analysis. The differentially expressed genes and significantly changed metabolites were screened based on transcriptomics and metabolomics analyses, respectively. Integrative analysis was further performed to confirm the hub genes, metabolites and pathways. After Rg3 intervention, the nasal symptoms and inflammatory infiltration were effectively improved, the levels of IgE, IL-4, IL-5, IL-13 and MDA were significantly reduced, and the level of SOD was obviously increased. The results of the qRT-PCR assay complemented the transcriptomic findings. Integrated analysis showed that Rg3 played an anti-AR role mainly by regulating the interaction network, which was constructed by 12 genes, 8 metabolites and 4 pathways. Our findings suggested that Rg3 had a therapeutic effect on ovalbumin-induced AR in mice by inhibiting inflammation development and reducing oxidative stress. The present study could provide a potential natural agent for the treatment of AR.

Metabolomics of asthma, COPD, and asthma-COPD overlap: an overview

The two common progressive lung diseases, asthma and chronic obstructive pulmonary disease (COPD), are the leading causes of morbidity and mortality worldwide. Asthma-COPD overlap, referred to as ACO, is another complex pulmonary disease that manifests itself with features of both asthma and COPD. The disease has no clear diagnostic or therapeutic guidelines, thereby making both diagnosis and treatment challenging. Though a number of studies on ACO have been documented, gaps in knowledge regarding the pathophysiologic mechanism of this disorder exist. Addressing this issue is an urgent need for improved diagnostic and therapeutic management of the disease. Metabolomics, an increasingly popular technique, reveals the pathogenesis of complex diseases and holds promise in biomarker discovery. This comprehensive narrative review, comprising 99 original research articles in the last five years (2017-2022), summarizes the scientific advances in terms of metabolic alterations in patients with asthma, COPD, and ACO. The analytical tools, nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS), commonly used to study the expression of the metabolome, are discussed. Challenges frequently encountered during metabolite identification and quality assessment are highlighted. Bridging the gap between phenotype and metabotype is envisioned in the future.

Application of Metabolomics in Obesity-Related Childhood Asthma Subtyping: A Narrative Scoping Review

Obesity-related asthma is a heterogeneous childhood asthma phenotype with rising prevalence. Observational studies identify early-life obesity or weight gain as risk factors for childhood asthma development. The reverse association is also described, children with asthma have a higher risk of being obese. Obese children with asthma have poor symptom control and an increased number of asthma attacks compared to non-obese children with asthma. Clinical trials have also identified that a proportion of obese children with asthma do not respond as well to usual treatment (e.g., inhaled corticosteroids). The heterogeneity of obesity-related asthma phenotypes may be attributable to different underlying pathogenetic mechanisms. Although few childhood obesity-related asthma endotypes have been described, our knowledge in this field is incomplete. An evolving analytical profiling technique, metabolomics, has the potential to link individuals' genetic backgrounds and environmental exposures (e.g., diet) to disease endotypes. This will ultimately help define clinically relevant obesity-related childhood asthma subtypes that respond better to targeted treatment. However, there are challenges related to this approach. The current narrative scoping review summarizes the evidence for metabolomics contributing to asthma subtyping in obese children, highlights the challenges associated with the implementation of this approach, and identifies gaps in research.

Metabolomics in pediatric lower respiratory tract infections and sepsis: a literature review

Lower respiratory tract infections (LRTIs) are a leading cause of morbidity and mortality in children. The ability of healthcare providers to diagnose and prognose LRTIs in the pediatric population remains a challenge, as children can present with similar clinical features regardless of the underlying pathogen or ultimate severity. Metabolomics, the large-scale analysis of metabolites and metabolic pathways offers new tools and insights that may aid in diagnosing and predicting the outcomes of LRTIs in children. This review highlights the latest literature on the clinical utility of metabolomics in providing care for children with bronchiolitis, pneumonia, COVID-19, and sepsis. IMPACT: This article summarizes current metabolomics approaches to diagnosing and predicting the course of pediatric lower respiratory infections. This article highlights the limitations to current metabolomics research and highlights future directions for the field.

Severe bronchiolitis profiling as the first step towards prevention of asthma

Bronchiolitis is the most common respiratory infection leading to hospitalization and constitutes a significant healthcare burden. The two main viral agents causing bronchiolitis, respiratory syncytial virus (RSV) and rhinovirus (RV), have distinct cytopathic, immune response, and clinical characteristics. Different approaches have been suggested for subtyping bronchiolitis based on viral etiology, atopic status, transcriptome profiles in blood, airway metabolome, lipidomic data, and airway microbiota. The highest risk of asthma at school age has been in a subgroup of bronchiolitis characterized by older age, high prevalence of RV infection, previous breathing problems, and/or eczema. Regarding solely viral etiology, RV-bronchiolitis in infancy has been linked to a nearly three times higher risk of developing asthma than RSV-bronchiolitis. Although treatment with betamimetics and systemic corticosteroids has been found ineffective in bronchiolitis overall, it can be beneficial for infants with severe RV bronchiolitis. Thus, there is a need to develop a more individualized therapeutic approach for bronchiolitis and follow-up strategies for infants at higher risk of asthma in the future perspective.

Diagnosis and management of asthma in infants and preschoolers

Asthma is one of the most common chronic disease affecting children, and it often starts in infancy and preschool years. In previous birth cohorts, frequent wheezing in early life was associated with the development of asthma in later childhood and reduced lung function persisting into adulthood. Preschool wheezing is considered an umbrella term for distinctive diseases with different clinical features (phenotypes), each of which may be related to different underlying pathophysiologic mechanisms (endotypes). The classification of phenotypes of early wheezing is needed to identify children at high risk for developing asthma later who might benefit from early intervention. However, diagnosis of asthma in infants and preschoolers is particularly difficult because objective lung function tests cannot be performed and definitive biomarkers are lacking. Moreover, management of early asthma is challenging because of its different phenotypic presentations. Many prediction models and asthma guidelines have been developed to provide useful information for physicians to assess young children with recurrent wheezing and manage them appropriately. Many recent studies have investigated the application of personalized medicine for early asthma by identifying specific phenotypes and biomarkers. Further researches, including genetic and molecular studies, are needed to establish a clear definition of asthma and develop more targeted therapeutic approaches in this age group.

Nasopharyngeal lipidomic endotypes of infants with bronchiolitis and risk of childhood asthma: a multicentre prospective study

BACKGROUND

Bronchiolitis is the leading cause of hospitalisation of US infants and an important risk factor for childhood asthma. Recent evidence suggests that bronchiolitis is clinically heterogeneous. We sought to derive bronchiolitis endotypes by integrating clinical, virus and lipidomics data and to examine their relationship with subsequent asthma risk.

METHODS

This is a multicentre prospective cohort study of infants (age <12 months) hospitalised for bronchiolitis. We identified endotypes by applying clustering approaches to clinical, virus and nasopharyngeal airway lipidomic data measured at hospitalisation. We then determined their longitudinal association with the risk for developing asthma by age 6 years by fitting a mixed-effects logistic regression model. To account for multiple comparisons of the lipidomics data, we computed the false discovery rate (FDR). To understand the underlying biological mechanism of the endotypes, we also applied pathway analyses to the lipidomics data.

RESULTS

Of 917 infants with bronchiolitis (median age, 3 months), we identified clinically and biologically meaningful lipidomic endotypes: (A) cinicalclassiclipidmixed (n=263), (B) clinicalseverelipidsphingolipids-high (n=281), (C) clinicalmoderatelipidphospholipids-high (n=212) and (D) clinicalatopiclipidsphingolipids-low (n=161). Endotype A infants were characterised by 'classic' clinical presentation of bronchiolitis. Profile D infants were characterised by a higher proportion of parental asthma, IgE sensitisation and rhinovirus infection and low sphingolipids (eg, sphingomyelins, ceramides). Compared with endotype A, profile D infants had a significantly higher risk of asthma (22% vs 50%; unadjusted OR, 3.60; 95% CI 2.31 to 5.62; p<0.001). Additionally, endotype D had a significantly lower abundance of polyunsaturated fatty acids (eg, docosahexaenoic acid; FDR=0.01). The pathway analysis revealed that sphingolipid metabolism pathway was differentially expressed in endotype D (FDR=0.048).

CONCLUSIONS

In this multicentre prospective cohort study of infants with bronchiolitis, integrated clustering of clinical, virus and lipidomic data identified clinically and biologically distinct endotypes that have a significantly differential risk for developing asthma.Delete.

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.

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.

Microbial dysbiosis and childhood asthma development: Integrated role of the airway and gut microbiome, environmental exposures, and host metabolic and immune response

Asthma is a chronic and heterogeneous respiratory disease with many risk factors that typically originate during early childhood. A complex interplay between environmental factors and genetic predisposition is considered to shape the lung and gut microbiome in early life. The growing literature has identified that changes in the relative abundance of microbes (microbial dysbiosis) and reduced microbial diversity, as triggers of the airway-gut axis crosstalk dysregulation, are associated with asthma development. There are several mechanisms underlying microbial dysbiosis to childhood asthma development pathways. For example, a bacterial infection in the airway of infants can lead to the activation and/or dysregulation of inflammatory pathways that contribute to bronchoconstriction and bronchial hyperresponsiveness. In addition, gut microbial dysbiosis in infancy can affect immune development and differentiation, resulting in a suboptimal balance between innate and adaptive immunity. This evolving dysregulation of secretion of pro-inflammatory mediators has been associated with persistent airway inflammation and subsequent asthma development. In this review, we examine current evidence around associations between the airway and gut microbial dysbiosis with childhood asthma development. More specifically, this review focuses on discussing the integrated roles of environmental exposures, host metabolic and immune responses, airway and gut microbial dysbiosis in driving childhood asthma development.

Association of Nasopharyngeal and Serum Glutathione Metabolism with Bronchiolitis Severity and Asthma Risk: A Prospective Multicenter Cohort Study

Infants hospitalized for bronchiolitis are at high risk for asthma. Glutathione-related metabolites may antagonize oxidative stress, which induces airway injuries in respiratory infection and subsequent airway remodeling. However, little is known about the relationship of glutathione-related metabolites with bronchiolitis severity and the risk of asthma. In a multicenter prospective observational cohort study of infants hospitalized for bronchiolitis, we measured nasopharyngeal and serum glutathione-related metabolites by using liquid chromatography−tandem mass spectrometry. We then examined their association with bronchiolitis severity (defined by positive pressure ventilation (PPV) use). We also identified severity-related glutathione-related metabolite signatures and examined their association with asthma at age 6 years. In 1013 infants, we identified 12 nasopharyngeal and 10 serum glutathione-related metabolites. In the multivariable models, lower relative abundances of seven metabolites, e.g., substrates of glutathione, including cysteine (adjOR 0.21, 95%CI 0.06−0.76), glycine (adjOR 0.25, 95%CI 0.07−0.85), and glutamate (adjOR 0.25, 95%CI 0.07−0.88), were significantly associated with PPV use (all FDR < 0.05). These associations were consistent with serum glutathione-related metabolites. The nasopharyngeal glutathione-related metabolite signature was also associated with a significantly higher risk of asthma (adjOR 0.90, 95%CI 0.82−0.99, p = 0.04). In infants hospitalized for bronchiolitis, glutathione-related metabolites were associated with bronchiolitis severity and asthma risk.

The impact of maternal asthma on the preterm infants' gut metabolome and microbiome (MAP study)

Preterm infants are at a greater risk for the development of asthma and atopic disease, which can lead to lifelong negative health consequences. This may be due, in part, to alterations that occur in the gut microbiome and metabolome during their stay in the Neonatal Intensive Care Unit (NICU). To explore the differential roles of family history (i.e., predisposition due to maternal asthma diagnosis) and hospital-related environmental and clinical factors that alter microbial exposures early in life, we considered a unique cohort of preterm infants born ≤ 34 weeks gestational age from two local level III NICUs, as part of the MAP (Microbiome, Atopic disease, and Prematurity) Study. From MAP participants, we chose a sub-cohort of infants whose mothers had a history of asthma and matched gestational age and sex to infants of mothers without a history of asthma diagnosis (control). We performed a prospective, paired metagenomic and metabolomic analysis of stool and milk feed samples collected at birth, 2 weeks, and 6 weeks postnatal age. Although there were clinical factors associated with shifts in the diversity and composition of stool-associated bacterial communities, maternal asthma diagnosis did not play an observable role in shaping the infant gut microbiome during the study period. There were significant differences, however, in the metabolite profile between the maternal asthma and control groups at 6 weeks postnatal age. The most notable changes occurred in the linoleic acid spectral network, which plays a role in inflammatory and immune pathways, suggesting early metabolomic changes in the gut of preterm infants born to mothers with a history of asthma. Our pilot study suggests that a history of maternal asthma alters a preterm infants’ metabolomic pathways in the gut, as early as the first 6 weeks of life.

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.