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

Interactions between respiratory syncytial virus and Streptococcus pneumoniae in the pathogenesis of childhood respiratory infections: a systematic review

Lower respiratory tract infections, commonly caused by respiratory syncytial virus (RSV) or Streptococcus pneumoniae (pneumococcus), pose a substantial global health burden, especially in children younger than 5 years of age. A deeper understanding of the relationship between RSV and pneumococcus would aid the development of health-care approaches to disease prevention and management. We completed a systematic review to identify and assess evidence pertaining to the relationship between RSV and pneumococcus in the pathogenesis of childhood respiratory infections. We found mechanistic evidence for direct pathogen-pathogen interactions and for indirect interactions involving host modulation. We found a strong seasonal epidemiological association between these two pathogens, which was recently confirmed by a parallel decrease and a subsequent resurgence of both RSV and pneumococcus-associated disease during the COVID-19 pandemic. Importantly, we found that pneumococcal vaccination was associated with reduced RSV hospitalisations in infants, further supporting the relevance of their interaction in modulating severe disease. Overall evidence supports a broad biological and clinical interaction between pneumococcus and RSV in the pathogenesis of childhood respiratory infections. We hypothesise that the implementation of next-generation pneumococcal and RSV vaccines and monoclonal antibodies targeting RSV will act synergistically to reduce global morbidity and mortality related to childhood respiratory infections.

CA, Harmon B, Espinola JA, Reck Cechinel L, Batabyal R, Freishtat RJ, Hahn A. Bacterial small RNAs may mediate immune response differences seen in respiratory syncytial virus versus rhinovirus bronchiolitis

Bronchiolitis, a viral lower respiratory infection, is the leading cause of infant hospitalization, which is associated with an increased risk for developing asthma later in life. Bronchiolitis can be caused by several respiratory viruses, such as respiratory syncytial virus (RSV), rhinovirus (RV), and others. It can also be caused by a solo infection (e.g., RSV- or RV-only bronchiolitis) or co-infection with two or more viruses. Studies have shown viral etiology-related differences between RSV- and RV-only bronchiolitis in the immune response, human microRNA (miRNA) profiles, and dominance of certain airway microbiome constituents. Here, we identified bacterial small RNAs (sRNAs), the prokaryotic equivalent to eukaryotic miRNAs, that differ between infants of the 35th Multicenter Airway Research Collaboration (MARC-35) cohort with RSV- versus RV-only bronchiolitis. We first derived reference sRNA datasets from cultures of four bacteria known to be associated with bronchiolitis (i.e., Haemophilus influenzae, Moraxella catarrhalis, Moraxella nonliquefaciens, and Streptococcus pneumoniae). Using these reference sRNA datasets, we found several sRNAs associated with RSV- and RV-only bronchiolitis in our human nasal RNA-Seq MARC-35 data. We also determined potential human transcript targets of the bacterial sRNAs and compared expression of the sRNAs between RSV- and RV-only cases. sRNAs are known to downregulate their mRNA target, we found that, compared to those associated with RV-only bronchiolitis, sRNAs associated with RSV-only bronchiolitis may relatively activate the IL-6 and IL-8 pathways and relatively inhibit the IL-17A pathway. These data support that bacteria may be contributing to inflammation differences seen in RSV- and RV-only bronchiolitis, and for the first time indicate that the potential mechanism in doing so may be through bacterial sRNAs.

Lung microbiome: new insights into the pathogenesis of respiratory diseases

The lungs were long thought to be sterile until technical advances uncovered the presence of the lung microbial community. The microbiome of healthy lungs is mainly derived from the upper respiratory tract (URT) microbiome but also has its own characteristic flora. The selection mechanisms in the lung, including clearance by coughing, pulmonary macrophages, the oscillation of respiratory cilia, and bacterial inhibition by alveolar surfactant, keep the microbiome transient and mobile, which is different from the microbiome in other organs. The pulmonary bacteriome has been intensively studied recently, but relatively little research has focused on the mycobiome and virome. This up-to-date review retrospectively summarizes the lung microbiome's history, composition, and function. We focus on the interaction of the lung microbiome with the oropharynx and gut microbiome and emphasize the role it plays in the innate and adaptive immune responses. More importantly, we focus on multiple respiratory diseases, including asthma, chronic obstructive pulmonary disease (COPD), fibrosis, bronchiectasis, and pneumonia. The impact of the lung microbiome on coronavirus disease 2019 (COVID-19) and lung cancer has also been comprehensively studied. Furthermore, by summarizing the therapeutic potential of the lung microbiome in lung diseases and examining the shortcomings of the field, we propose an outlook of the direction of lung microbiome research.

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.

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.

An Overview on the Primary Factors That Contribute to Non-Allergic Asthma in Children

The prevalence of non-allergic asthma in childhood is low, peaking in late adulthood. It is triggered by factors other than allergens, like cold and dry air, respiratory infections, hormonal changes, smoke and air pollution. In the literature, there are few studies that describe non-allergic asthma in pediatric age. Even though it is a less common disorder in kids, it is crucial to identify the causes in order to keep asthma under control, particularly in patients not responding to conventional treatments. In this review, we discuss non-IgE-mediated forms of asthma, collecting the latest research on etiopathogenesis and treatment.

Changes in T-Cell Subsets and Serum IFN-γ, IL-17, and IgE Levels in Children with Respiratory Syncytial Virus Capillary Bronchitis and Their Clinical Significance

Objective

To investigate the changes in T-cell subsets and serum IFN-γ, IL-17, and IgE levels in children with respiratory syncytial virus capillary bronchitis and their clinical significance.

Methods

The clinical data of 50 children with respiratory syncytial virus capillary bronchitis admitted to our hospital between July 2020 and June 2021 were retrospectively reviewed, and they were included in the observation group, while 50 children with a healthy physical examination during the same period were chosen as the control group. The T-cell subsets (CD4, CD8, and CD4/CD8) and serum IL-4, IL-8, IFN-, IL-17, and IgE levels of children in the two groups were compared, and the clinical significance of the changes in the levels of the indices mentioned above was analyzed.

Results

There was no statistically significant difference in T-cell subset levels (CD4 and CD8) between the two groups (P > 0.05); the level of CD4/CD8, IL-4, IL-8, IL-17, and IgE in the observation group were substantially higher than those in the control group (P < 0.05), while the serum IFN-γ levels in the observation group were significantly lower than those in the control group (P < 0.05).

Conclusion

Increased CD4/CD8 levels in children with respiratory syncytial virus capillary bronchitis cause an imbalance in the Th1/Th2 immune response, similar to changes in bronchial asthma, suggesting a link between the two diseases. Increased serum levels of IL-4, IL-8, IL-17, and IgE and decreased serum levels of IFN-γ have been seen in children with respiratory syncytial virus capillary bronchitis, suggesting the severity of the children's disease may in part be reflected in the levels of the aforementioned serum indicators.

Host-microbial co-metabolites modulated by human milk oligosaccharides relate to reduced risk of respiratory tract infections

Human milk oligosaccharides (HMOs) are structurally diverse oligosaccharides present in breast milk, supporting the development of the gut microbiota and immune system. Previously, 2-HMO (2'fucosyllactose, lacto-N-neotetraose) compared to control formula feeding was associated with reduced risk of lower respiratory tract infections (LRTIs), in part linked to lower acetate and higher bifidobacteria proportions. Here, our objective was to gain further insight into additional molecular pathways linking the 2-HMO formula feeding and LRTI mitigation. From the same trial, we measured the microbiota composition and 743 known biochemical species in infant stool at 3 months of age using shotgun metagenomic sequencing and untargeted mass spectrometry metabolomics. We used multivariate analysis to identify biochemicals associated to 2-HMO formula feeding and LRTI and integrated those findings with the microbiota compositional data. Three molecular pathways stood out: increased gamma-glutamylation and N-acetylation of amino acids and decreased inflammatory signaling lipids. Integration of stool metagenomic data revealed some Bifidobacterium and Bacteroides species to be implicated. These findings deepen our understanding of the infant gut/microbiome co-metabolism in early life and provide evidence for how such metabolic changes may influence immune competence at distant mucosal sites such as the airways.

Small-molecule metabolome identifies potential therapeutic targets against COVID-19

Respiratory viruses are transmitted and acquired via the nasal mucosa, and thereby may influence the nasal metabolome composed of biochemical products produced by both host cells and microbes. Studies of the nasal metabolome demonstrate virus-specific changes that sometimes correlate with viral load and disease severity. Here, we evaluate the nasopharyngeal metabolome of COVID-19 infected individuals and report several small molecules that may be used as potential therapeutic targets. Specimens were tested by qRT-PCR with target primers for three viruses: Influenza A (INFA), respiratory syncytial virus (RSV), and SARS-CoV-2, along with unaffected controls. The nasopharyngeal metabolome was characterized using an LC–MS/MS-based screening kit capable of quantifying 141 analytes. A machine learning model identified 28 discriminating analytes and correctly categorized patients with a viral infection with an accuracy of 96% (R² = 0.771, Q² = 0.72). A second model identified 5 analytes to differentiate COVID19-infected patients from those with INFA or RSV with an accuracy of 85% (R² = 0.442, Q² = 0.301). Specifically, Lysophosphatidylcholines-a-C18:2 (LysoPCaC18:2) concentration was significantly increased in COVID19 patients (P < 0.0001), whereas beta-hydroxybutyric acid, Methionine sulfoxide, succinic acid, and carnosine concentrations were significantly decreased (P < 0.0001). This study demonstrates that COVID19 infection results in a unique nasopharyngeal metabolomic signature with carnosine and LysoPCaC18:2 as potential therapeutic targets.

Accurate virus identification with interpretable Raman signatures by machine learning

Significance A large Raman dataset collected on a variety of viruses enables the training of machine learning (ML) models capable of highly accurate and sensitive virus identification. The trained ML models can then be integrated with a portable device to provide real-time virus detection and identification capability. We validate this conceptual framework by presenting highly accurate virus type and subtype identification results using a convolutional neural network to classify Raman spectra of viruses. The accurate and interpretable ML model developed for Raman virus identification presents promising potential in a real-time, label-free virus detection system that could be used in future outbreaks and pandemics.

Pragmatic Randomized Trial of Corticosteroids and Inhaled Epinephrine for Bronchiolitis in Children in Intensive Care

OBJECTIVE

To determine whether the combination of systemic corticosteroids and nebulized epinephrine, compared with standard care, reduces the duration of positive pressure support in children with bronchiolitis admitted to intensive care.

STUDY DESIGN

We performed a pragmatic, multicenter, open-label, randomized trial between July 2013 and November 2019 in children younger than 18 months old with a clinical diagnosis of bronchiolitis. The intervention group received the equivalent of 13 mg/kg prednisolone over 3 days, then 1 mg/kg daily for 3 days, plus 0.05 mL/kg of nebulized 1% epinephrine made up to 6 ml with 0.9% saline via jet nebulizer and mask using oxygen at 12 l/min every 30 minutes for 5 doses, then 1-4 hourly for 3 days, then as required for 3 days. The primary outcome was clinician-managed duration of positive pressure support in intensive care defined as high-flow nasal-prong oxygen, nasopharyngeal continuous positive airway pressure, or mechanical ventilation.

RESULTS

In total, 210 children received positive pressure support. In the corticosteroid-epinephrine group, 107 children received positive pressure support for a geometric mean of 26 (95% CI, 22-32) hours compared with 40 (95% CI 34-47) hours in 103 controls, adjusted ratio 0.66 (95% CI 0.51-0.84), P = .001. In the intervention group, 41 (38%) children experienced at least 1 adverse event, compared with 39 (38%) in the control group.

CONCLUSIONS

In children with severe bronchiolitis, the duration of clinician-managed pressure support was reduced by regular treatment with systemic corticosteroids and inhaled epinephrine compared with standard care.

CLINICAL TRIAL REGISTRATION

Australian Clinical Trials Research Network: ACTRN12613000316707.

Integrated analysis of plasma and single immune cells uncovers metabolic changes in individuals with COVID-19

A better understanding of the metabolic alterations in immune cells during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection may elucidate the wide diversity of clinical symptoms experienced by individuals with coronavirus disease 2019 (COVID-19). Here, we report the metabolic changes associated with the peripheral immune response of 198 individuals with COVID-19 through an integrated analysis of plasma metabolite and protein levels as well as single-cell multiomics analyses from serial blood draws collected during the first week after clinical diagnosis. We document the emergence of rare but metabolically dominant T cell subpopulations and find that increasing disease severity correlates with a bifurcation of monocytes into two metabolically distinct subsets. This integrated analysis reveals a robust interplay between plasma metabolites and cell-type-specific metabolic reprogramming networks that is associated with disease severity and could predict survival.

Statin-mediated disruption of Rho GTPase prenylation and activity inhibits respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is a leading cause of severe respiratory tract infections in children. To uncover new antiviral therapies, we developed a live cell-based high content screening approach for rapid identification of RSV inhibitors and characterized five drug classes which inhibit the virus. Among the molecular targets for each hit, there was a strong functional enrichment in lipid metabolic pathways. Modulation of lipid metabolites by statins, a key hit from our screen, decreases the production of infectious virus through a combination of cholesterol and isoprenoid-mediated effects. Notably, RSV infection globally upregulates host protein prenylation, including the prenylation of Rho GTPases. Treatment by statins or perillyl alcohol, a geranylgeranyltransferase inhibitor, reduces infection in vitro. Of the Rho GTPases assayed in our study, a loss in Rac1 activity strongly inhibits the virus through a decrease in F protein surface expression. Our findings provide new insight into the importance of host lipid metabolism to RSV infection and highlight geranylgeranyltransferases as an antiviral target for therapeutic development.

Metabolic Reprogramming of Nasal Airway Epithelial Cells Following Infant Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is a seasonal mucosal pathogen that infects the ciliated respiratory epithelium and results in the most severe morbidity in the first six months of life. RSV is a common cause of acute respiratory infection during infancy and is an important early-life risk factor strongly associated with asthma development. While this association has been repeatedly demonstrated, limited progress has been made on the mechanistic understanding in humans of the contribution of infant RSV infection to airway epithelial dysfunction. An active infection of epithelial cells with RSV in vitro results in heightened central metabolism and overall hypermetabolic state; however, little is known about whether natural infection with RSV in vivo results in lasting metabolic reprogramming of the airway epithelium in infancy. To address this gap, we performed functional metabolomics, 13C glucose metabolic flux analysis, and RNA-seq gene expression analysis of nasal airway epithelial cells (NAECs) sampled from infants between 2-3 years of age, with RSV infection or not during the first year of life. We found that RSV infection in infancy was associated with lasting epithelial metabolic reprogramming, which was characterized by (1) significant increase in glucose uptake and differential utilization of glucose by epithelium; (2) altered preferences for metabolism of several carbon and energy sources; and (3) significant sexual dimorphism in metabolic parameters, with RSV-induced metabolic changes most pronounced in male epithelium. In summary, our study supports the proposed phenomenon of metabolic reprogramming of epithelial cells associated with RSV infection in infancy and opens exciting new venues for pursuing mechanisms of RSV-induced epithelial barrier dysfunction in early life.

Nasopharyngeal metabolomics and machine learning approach for the diagnosis of influenza

Background

Respiratory virus infections are significant causes of morbidity and mortality, and may induce host metabolite alterations by infecting respiratory epithelial cells. We investigated the use of liquid chromatography quadrupole time-of-flight mass spectrometry (LC/Q-TOF) combined with machine learning for the diagnosis of influenza infection.

Methods

We analyzed nasopharyngeal swab samples by LC/Q-TOF to identify distinct metabolic signatures for diagnosis of acute illness. Machine learning models were performed for classification, followed by Shapley additive explanation (SHAP) analysis to analyze feature importance and for biomarker discovery.

Findings

A total of 236 samples were tested in the discovery phase by LC/Q-TOF, including 118 positive samples (40 influenza A 2009 H1N1, 39 influenza H3 and 39 influenza B) as well as 118 age and sex-matched negative controls with acute respiratory illness. Analysis showed an area under the receiver operating characteristic curve (AUC) of 1.00 (95% confidence interval [95% CI] 0.99, 1.00), sensitivity of 1.00 (95% CI 0.86, 1.00) and specificity of 0.96 (95% CI 0.81, 0.99). The metabolite most strongly associated with differential classification was pyroglutamic acid. Independent validation of a biomarker signature based on the top 20 differentiating ion features was performed in a prospective cohort of 96 symptomatic individuals including 48 positive samples (24 influenza A 2009 H1N1, 5 influenza H3 and 19 influenza B) and 48 negative samples. Testing performed using a clinically-applicable targeted approach, liquid chromatography triple quadrupole mass spectrometry, showed an AUC of 1.00 (95% CI 0.998, 1.00), sensitivity of 0.94 (95% CI 0.83, 0.98), and specificity of 1.00 (95% CI 0.93, 1.00). Limitations include lack of sample suitability assessment, and need to validate these findings in additional patient populations.

Interpretation

This metabolomic approach has potential for diagnostic applications in infectious diseases testing, including other respiratory viruses, and may eventually be adapted for point-of-care testing.

Big Data, Data Science, and Causal Inference: A Primer for Clinicians

Clinicians handle a growing amount of clinical, biometric, and biomarker data. In this “big data” era, there is an emerging faith that the answer to all clinical and scientific questions reside in “big data” and that data will transform medicine into precision medicine. However, data by themselves are useless. It is the algorithms encoding causal reasoning and domain (e.g., clinical and biological) knowledge that prove transformative. The recent introduction of (health) data science presents an opportunity to re-think this data-centric view. For example, while precision medicine seeks to provide the right prevention and treatment strategy to the right patients at the right time, its realization cannot be achieved by algorithms that operate exclusively in data-driven prediction modes, as do most machine learning algorithms. Better understanding of data science and its tasks is vital to interpret findings and translate new discoveries into clinical practice. In this review, we first discuss the principles and major tasks of data science by organizing it into three defining tasks: (1) association and prediction, (2) intervention, and (3) counterfactual causal inference. Second, we review commonly-used data science tools with examples in the medical literature. Lastly, we outline current challenges and future directions in the fields of medicine, elaborating on how data science can enhance clinical effectiveness and inform medical practice. As machine learning algorithms become ubiquitous tools to handle quantitatively “big data,” their integration with causal reasoning and domain knowledge is instrumental to qualitatively transform medicine, which will, in turn, improve health outcomes of patients.

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.

Association of Increased Circulating Acetic Acid With Poor Survival in Pseudomonas aeruginosa Ventilator-Associated Pneumonia Patients

Background

We previously found that microbial disruption in Pseudomonas aeruginosa ventilator-associated pneumonia (PA-VAP) patients are long-lasting. Long-term microbial dysbiosis may lead to changes in metabolites. Short-chain fatty acids (SCFAs) are microbial fermentation products and show beneficial effects in patients with pneumonia. In this study, we aimed to explore the association between circulating SCFA levels and clinical outcomes in patients with PA-VAP.

Methods

In this study, we analyzed SCFAs in the serum of 49 patients with PA-VAP by gas chromatography-mass spectrometry analysis. Twenty of these patients died, and 29 survived. The correlation between serum SCFAs and patient survival and immune parameters was analyzed.

Results

We developed a partial least squares discriminant analysis (PLS-DA) model to examine differential SCFAs in 49 patients with PA-VAP. Among the seven SCFAs, only acetic acid was increased in non-survivors (P = 0.031, VIP > 1). Furthermore, high levels of acetic acid (>1.96ug/ml) showed increased 90-day mortality compared to low levels of acetic acid (<1.96ug/ml) in Kaplan-Meier survival analyses (P = 0.027). Increased acetic acid also correlated with reduced circulating lymphocyte and monocyte counts.

Conclusion

Our study showed that increased circulating acetic acid is associated with 90-day mortality in PA-VAP patients. The decrease in lymphocytes and monocytes might be affected by acetic acid and involved in the poor prognosis.

Application of Metabolomics in Pediatric Asthma: Prediction, Diagnosis and Personalized Treatment

Asthma in children remains a significant public health challenge affecting 5–20% of children in Europe and is associated with increased morbidity and societal healthcare costs. The high variation in asthma incidence among countries may be attributed to differences in genetic susceptibility and environmental factors. This respiratory disorder is described as a heterogeneous syndrome of multiple clinical manifestations (phenotypes) with varying degrees of severity and airway hyper-responsiveness, which is based on patient symptoms, lung function and response to pharmacotherapy. However, an accurate diagnosis is often difficult due to diversities in clinical presentation. Therefore, identifying early diagnostic biomarkers and improving the monitoring of airway dysfunction and inflammatory through non-invasive methods are key goals in successful pediatric asthma management. Given that asthma is caused by the interaction between genes and environmental factors, an emerging approach, metabolomics—the systematic analysis of small molecules—can provide more insight into asthma pathophysiological mechanisms, enable the identification of early biomarkers and targeted personalized therapies, thus reducing disease burden and societal cost. The purpose of this review is to present evidence on the utility of metabolomics in pediatric asthma through the analysis of intermediate metabolites of biochemical pathways that involve carbohydrates, amino acids, lipids, organic acids and nucleotides and discuss their potential application in clinical practice. Also, current challenges on the integration of metabolomics in pediatric asthma management and needed next steps are critically discussed.

Relationship of Viral Detection with Duration of Ventilation in Critically Ill Infants with Lower Respiratory Tract Infection

RATIONALE

Although respiratory virus testing is frequent done for critically ill infants with bronchiolitis, the prognostic value of this testing is unknown for those requiring positive pressure ventilation (PPV).

OBJECTIVES

To determine the differences in PPV utilization according to viral detection and to explore the association between viral detection and duration of PPV in critically ill children with presumed respiratory infection.

METHODS

This is a retrospective cohort study in a quaternary pediatric intensive care unit from February 2014 until February 2017. We evaluated 984 children < 1 year of age who received PPV for presumed respiratory infection without significant congenital heart disease, care limitations, baseline PPV usage, or tracheostomy. Respiratory viruses were identified using a PCR panel. Analyses of duration of PPV according to viral etiology were performed using univariate and multivariable logistic regression and truncated negative binomial regression with calculated mean marginal effect (MME).

RESULTS

Overall, 85 (9%) infants had no viruses identified, 629 (64%) had a single virus detected, most commonly respiratory syncytial virus (RSV) (417, 42%) followed by rhinovirus/enterovirus (RV/EV) (145, 15%), 230 (23%) had 2 viruses detected, and 40 (4%) had three viruses detected. Compared to those with 1 or no virus detected, infants with ≥2 viruses received longer total PPV duration in adjusted analysis [RR:1.4 (95% CI 1.2-1.6); p<0.001, MME=29 hours]. Detection of RV/EV alone, compared to RSV alone, was associated with significantly shorter duration of total PPV [RR:0.7 (95% CI 0.62, 0.87); p=<0.001, MME= -23 hours], noninvasive PPV [RR: 0.7 (95% CI 0.60, 0.85); p<0.001 MME = -15 hours], and invasive PPV [RR 0.7 (95% CI 0.54, 0.83); p<0.001, MME = -54 hours) when adjusted for weight, prematurity, and administration of early antibiotic therapy.

CONCLUSIONS

Identification of viral type and number in severe bronchiolitis is an important predictor of duration of PPV.

TIPICO X: report of the 10th interactive infectious disease workshop on infectious diseases and vaccines

TIPICO is an expert meeting and workshop that aims to provide the most recent evidence in the field of infectious diseases and vaccination. The 10th Interactive Infectious Disease TIPICO workshop took place in Santiago de Compostela, Spain, on November 21-22, 2019. Cutting-edge advances in vaccination against respiratory syncytial virus, Streptococcus pneumoniae, rotavirus, human papillomavirus, Neisseria meningitidis, influenza virus, and Salmonella Typhi were discussed. Furthermore, heterologous vaccine effects were updated, including the use of Bacillus Calmette-Guérin (BCG) vaccine as potential treatment for type 1 diabetes. Finally, the workshop also included presentations and discussion on emergent virus and zoonoses, vaccine resilience, building and sustaining confidence in vaccination, approaches to vaccine decision-making, pros and cons of compulsory vaccination, the latest advances in decoding infectious diseases by RNA gene signatures, and the application of big data approaches.

A Comparative Evaluation of Tools to Predict Metabolite Profiles From Microbiome Sequencing Data

Metabolomic analyses of human gut microbiome samples can unveil the metabolic potential of host tissues and the numerous microorganisms they support, concurrently. As such, metabolomic information bears immense potential to improve disease diagnosis and therapeutic drug discovery. Unfortunately, as cohort sizes increase, comprehensive metabolomic profiling becomes costly and logistically difficult to perform at a large scale. To address these difficulties, we tested the feasibility of predicting the metabolites of a microbial community based solely on microbiome sequencing data. Paired microbiome sequencing (16S rRNA gene amplicons, shotgun metagenomics, and metatranscriptomics) and metabolome (mass spectrometry and nuclear magnetic resonance spectroscopy) datasets were collected from six independent studies spanning multiple diseases. We used these datasets to evaluate two reference-based gene-to-metabolite prediction pipelines and a machine-learning (ML) based metabolic profile prediction approach. With the pre-trained model on over 900 microbiome-metabolome paired samples, the ML approach yielded the most accurate predictions (i.e., highest F1 scores) of metabolite occurrences in the human gut and outperformed reference-based pipelines in predicting differential metabolites between case and control subjects. Our findings demonstrate the possibility of predicting metabolites from microbiome sequencing data, while highlighting certain limitations in detecting differential metabolites, and provide a framework to evaluate metabolite prediction pipelines, which will ultimately facilitate future investigations on microbial metabolites and human health.

The use of β2-adrenoreceptor agonists in viral bronchiolitis: scientific rationale beyond evidence-based guidelines

Despite scientific evidence proving that inhaled β₂-adrenergic receptor (β₂-AR) agonists can reverse bronchoconstriction in all ages, current guidelines advocate against the use of β₂-AR bronchodilators in infants with viral bronchiolitis because clinical trials have not demonstrated an overall clinical benefit. However, there are many different types of viral bronchiolitis, with variations occurring at an individual and viral level. To discard a potentially helpful treatment from all children regardless of their clinical features may be unwarranted. Unfortunately, the clinical criteria to identify the infants that may benefit from bronchodilators from those who do not are not clear. Thus, we summarised the current understanding of the individual factors that may help clinicians determine the highest probability of response to β₂-AR bronchodilators during viral bronchiolitis, based on the individual immunobiology, viral pathogen, host factors and clinical presentation.

There are several factors that may help clinicians determine the highest probability of response to β₂-AR bronchodilators during viral bronchiolitis, based on the individual immunobiology, viral pathogen, host factors and clinical presentationhttps://bit.ly/30CoHcH

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.

Decoding Susceptibility to Respiratory Viral Infections and Asthma Inception in Children

Human Respiratory Syncytial Virus and Human Rhinovirus are the most frequent cause of respiratory tract infections in infants and children and are major triggers of acute viral bronchiolitis, wheezing and asthma exacerbations. Here, we will discuss the application of the powerful tools of systems biology to decode the molecular mechanisms that determine risk for infection and subsequent asthma. An important conceptual advance is the understanding that the innate immune system is governed by a Bow-tie architecture, where diverse input signals converge onto a few core pathways (e.g., IRF7), which in turn generate diverse outputs that orchestrate effector and regulatory functions. Molecular profiling studies in children with severe exacerbations of asthma/wheeze have identified two major immunological phenotypes. The IRF7hi phenotype is characterised by robust upregulation of antiviral response networks, and the IRF7lo phenotype is characterised by upregulation of markers of TGFβ signalling and type 2 inflammation. Similar phenotypes have been identified in infants and children with severe viral bronchiolitis. Notably, genome-wide association studies supported by experimental validation have identified key pathways that increase susceptibility to HRV infection (ORMDL3 and CHDR3) and modulate TGFβ signalling (GSDMB, TGFBR1, and SMAD3). Moreover, functional deficiencies in the activation of type I and III interferon responses are already evident at birth in children at risk of developing febrile lower respiratory tract infections and persistent asthma/wheeze, suggesting that the trajectory to asthma begins at birth or in utero. Finally, exposure to microbes and their products reprograms innate immunity and provides protection from the development of allergies and asthma in children, and therefore microbial products are logical candidates for the primary prevention of asthma.

Predictors for the prescription of albuterol in infants hospitalized for viral bronchiolitis

INTRODUCTION AND OBJECTIVES

Despite the recommendation against routine use of inhaled bronchodilators in infants with viral bronchiolitis given in the main clinical practice guidelines (CPGs) on viral bronchiolitis, albuterol is widely prescribed to patients with this disease. The aim of this study was to identify predictors of prescription of albuterol in a population of infants hospitalized for viral bronchiolitis.

MATERIAL AND METHODS

An analytical cross-sectional study performed during the period from March 2014 to August 2015, in a random sample of patients <2 years old hospitalized in the Fundacion Hospital La Misericordia, a hospital located in Bogota, Colombia. After reviewing the electronic medical records, we collected demographic, clinical, and disease-related information, including prescription of albuterol at any time during the course of hospitalization as the outcome variable.

RESULTS

For a total of 1365 study participants, 1042 (76.3%) were prescribed with albuterol therapy. After controlling for potential confounders, it was found that age (OR 1.11; CI 95% 1.08-1.15; p<0.001), and a prolonged length of stay (LOS) (OR 1.93; CI 95% 1.44-2.60; p<0.001) were independent predictors of prescription of albuterol in our sample of patients. By contrast, albuterol prescription was less likely in the post-guideline assessment period (OR 0.41; CI 95% 0.31-0.54; p<0.001), and in infants with RSV isolation (OR 0.71; CI 95% 0.52-0.97; p=0.035).

CONCLUSIONS

Albuterol was highly prescribed in our population of inpatients with the disease. The independent predictors of prescription of albuterol in our sample of patients were age, implementation of a CPG on viral bronchiolitis, RSV isolation, and LOS.

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.

Early-Life Respiratory Syncytial Virus Infection, Trained Immunity and Subsequent Pulmonary Diseases

Respiratory syncytial virus (RSV) is often the first clinically relevant pathogen encountered in life, with nearly all children infected by two years of age. Many studies have also linked early-life severe respiratory viral infection with more pathogenic immune responses later in life that lead to pulmonary diseases like childhood asthma. This phenomenon is thought to occur through long-term immune system alterations following early-life respiratory viral infection and may include local responses such as unresolved inflammation and/or direct structural or developmental modifications within the lung. Furthermore, systemic responses that could impact the bone marrow progenitors may be a significant cause of long-term alterations, through inflammatory mediators and shifts in metabolic profiles. Among these alterations may be changes in transcriptional and epigenetic programs that drive persistent modifications throughout life, leaving the immune system poised toward pathogenic responses upon secondary insult. This review will focus on early-life severe RSV infection and long-term alterations. Understanding these mechanisms will not only lead to better treatment options to limit initial RSV infection severity but also protect against the development of childhood asthma linked to severe respiratory viral infections.

The impact of viral bronchiolitis phenotyping: Is it time to consider phenotype-specific responses to individualize pharmacological management?

Although recent guidelines recommend a minimalist approach to bronchiolitis, there are several issues with this posture. First, there are concerns about the definition of the disease, the quality of the guidelines, the method of administration of bronchodilators, and the availability of tools to evaluate the response to therapies. Second, for decades it has been assumed that all cases of viral bronchiolitis are the same, but recent evidence has shown that this is not the case. Distinct bronchiolitis phenotypes have been described, with heterogeneity in clinical presentation, molecular immune signatures and clinically relevant outcomes such as respiratory failure and recurrent wheezing. New research is critically needed to refine viral bronchiolitis phenotyping at the molecular and clinical levels as well as to define phenotype-specific responses to different therapeutic options.

Metabolic changes during respiratory syncytial virus infection of epithelial cells

Viral infections induce substantial metabolic changes in infected cells to optimize viral production while cells develop countermeasures to restrict that infection. Human respiratory syncytial virus (HRSV) is an infectious pathogen that causes severe lower respiratory tract infections (LRTI) in infants, the elderly, and immunocompromised adults for which no effective treatment or vaccine is currently available. In this study, variations in metabolite levels at different time points post-HRSV infection of epithelial cells were studied by untargeted metabolomics using liquid chromatography/mass spectrometry analysis of methanol cell extracts. Numerous metabolites were significantly upregulated after 18 hours post-infection, including nucleotides, amino acids, amino and nucleotide sugars, and metabolites of the central carbon pathway. In contrast, most lipid classes were downregulated. Additionally, increased levels of oxidized glutathione and polyamines were associated with oxidative stress in infected cells. These results show how HRSV infection influences cell metabolism to produce the energy and building blocks necessary for virus reproduction, suggesting potential therapeutic interventions against this virus.

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.

Metabolomic Profiling of Infants With Recurrent Wheezing After Bronchiolitis

Background

Bronchiolitis is associated with a greater risk of developing recurrent wheezing, but with currently available tools, it is impossible to know which infants with bronchiolitis will develop this condition. This preliminary prospective study aimed to assess whether urine metabolomic analysis can be used to identify children with bronchiolitis who are at risk of developing recurrent wheezing.

Methods

Fifty-two infants <1 year old treated in the emergency department at University Hospital of Padova for acute bronchiolitis were enrolled (77% tested positive for respiratory syncytial virus [RSV]). Follow-up visits were conducted for 2 years after the episode of bronchiolitis. Untargeted metabolomic analyses based on mass spectrometry were performed on urine samples collected from infants with acute bronchiolitis. Data modeling was based on univariate and multivariate data analyses.

Results

We distinguished children with and those without postbronchiolitis recurrent wheeze, defined as ≥3 episodes of physician-diagnosed wheezing. Pathway overrepresentation analysis pointed to a major involvement of the citric acid cycle (P < .001) and some amino acids (lysine, cysteine, and methionine; P ≤ .015) in differentiating between these 2 groups of children.

Conclusion

This is the first study showing that metabolomic profiling of urine specimens from infants with bronchiolitis can be used to identify children at increased risk of developing recurrent wheezing.

Functional effects of the microbiota in chronic respiratory disease

The composition of the lung microbiome is increasingly well characterised, with changes in microbial diversity or abundance observed in association with several chronic respiratory diseases such as asthma, cystic fibrosis, bronchiectasis, and chronic obstructive pulmonary disease. However, the precise effects of the microbiome on pulmonary health and the functional mechanisms by which it regulates host immunity are only now beginning to be elucidated. Bacteria, viruses, and fungi from both the upper and lower respiratory tract produce structural ligands and metabolites that interact with the host and alter the development and progression of chronic respiratory diseases. Here, we review recent advances in our understanding of the composition of the lung microbiome, including the virome and mycobiome, the mechanisms by which these microbes interact with host immunity, and their functional effects on the pathogenesis, exacerbations, and comorbidities of chronic respiratory diseases. We also describe the present understanding of how respiratory microbiota can influence the efficacy of common therapies for chronic respiratory disease, and the potential of manipulation of the microbiome as a therapeutic strategy. Finally, we highlight some of the limitations in the field and propose how these could be addressed in future research.

The Problematic 2014 American Academy of Pediatrics Bronchiolitis Guidelines

The 2014 American Academy of Pediatrics bronchiolitis guidelines do not adequately serve the needs and clinical realities of front-line clinicians caring for undifferentiated wheezing infants and children. This article describes the clinical challenges of evaluating and managing a heterogeneous disease syndrome presenting as undifferentiated patients to the emergency department. Although the 2014 American Academy of Pediatrics bronchiolitis guidelines and the multiple international guidelines that they closely mirror have made a good faith attempt to provide clinicians with the best evidence-based recommendations possible, they have all failed to address practical, front-line clinical challenges. The therapeutic nihilism of the guidelines and the dissonance between many of the recommendations and frontline realities have had wide-ranging consequences. Nevertheless, newer evidence of therapeutic options is emerging and forecasts hope for more therapeutically optimistic recommendations with the next revision of the guidelines.

The lung microbiome dynamics between stability and exacerbation in chronic obstructive pulmonary disease (COPD): Current perspectives

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disorder with a course that is not uniform for all COPD patients. Although smoking is considered as the major cause of the disease, persistent or recurrent infections seem to play a particular role in the disease establishment and progression. COPD is characterized by dysregulated immunity that has been associated with the bacterial colonization and infections. The establishment of culture-independent techniques has shed new light on the relationships between bacterial ecology and health status and expanded our knowledge on the lung microbiome. Interactions between the host and lung microbiome result in inflammation and activation of resident cells. The lung microbiome contains populations of symbionts and pathobionts in balance which lose their equilibrium and disturb the balance of T-helper and regulatory T-cells (Treg) upon infection, or lung disease. In COPD factors such as disease severity, exacerbations, degree of inflammation, and type of treatment used (e.g inhaled or systemic steroids and antibiotics) affect the composition of lung microbiota. Recent data indicate that the presence of specific bacterial taxa in the airways has the potential to influence the host immune response and possibly to interfere with disease phenotype. Although, there is a growing body of evidence for the role of microbiome in COPD several unanswered questions still exist for its clinical relevance.

Impact of Rhinovirus Infections in Children

Rhinovirus (RV) is an RNA virus that causes more than 50% of upper respiratory tract infections in humans worldwide. Together with Respiratory Syncytial Virus, RV is one of the leading causes of viral bronchiolitis in infants and the most common virus associated with wheezing in children aged between one and two years. Because of its tremendous genetic diversity (>150 serotypes), the recurrence of RV infections each year is quite typical. Furthermore, because of its broad clinical spectrum, the clinical variability as well as the pathogenesis of RV infection are nowadays the subjects of an in-depth examination and have been the subject of several studies in the literature. In fact, the virus is responsible for direct cell cytotoxicity in only a small way, and it is now clearer than ever that it may act indirectly by triggering the release of active mediators by structural and inflammatory airway cells, causing the onset and/or the acute exacerbation of asthmatic events in predisposed children. In the present review, we aim to summarize the RV infection's epidemiology, pathogenetic hypotheses, and available treatment options as well as its correlation with respiratory morbidity and mortality in the pediatric population.

Application of metabolomics in viral pneumonia treatment with traditional Chinese medicine

Nowadays, traditional Chinese medicines (TCMs) have been reported to provide reliable therapies for viral pneumonia, but the therapeutic mechanism remains unknown. As a systemic approach, metabolomics provides an opportunity to clarify the action mechanism of TCMs, TCM syndromes or after TCM treatment. This review aims to provide the metabolomics evidence available on TCM-based therapeutic measures against viral pneumonia. Metabolomics has been gradually applied to the efficacy evaluation of TCMs in treatment of viral pneumonia and the metabolomics analysis exhibits a systemic metabolic shift in lipid, amino acids, and energy metabolism. Currently, most studies of TCM in treatment of viral pneumonia are untargeted metabolomics and further validations on targeted metabolomics should be carried out together with molecular biology technologies.

Metabolomic and Immunological Profiling of Respiratory Syncytial Virus Infection after Intranasal Immunization with a Subunit Vaccine Candidate

Respiratory syncytial virus (RSV) is a significant cause of mortality and morbidity in infants, the elderly, immunocompromised individuals, and patients with congenital heart diseases. Despite extensive efforts, a vaccine against RSV is still not available. We have previously reported the development of a subunit vaccine (ΔF/TriAdj) composed of a truncated version of the fusion protein (ΔF) and a polymer-based combination adjuvant (TriAdj). We compared inflammatory responses of ΔF/TriAdj-vaccinated and unvaccinated mice following intranasal challenge with RSV. Rapid and early inflammatory responses were observed in lung samples from both groups but modulated in the vaccinated group 7 days after the viral challenge. The underlying mechanism of action of ΔF/TriAdj was further studied through LC-MS-based metabolomic profiling by using ¹²C- or ¹³C-dansyl labeling for the amine/phenol submetabolome. RSV infection predominantly affected the amino acid biosynthesis pathways and urea cycle, whereas ΔF/TriAdj modulated the concentrations of almost all of the altered metabolites. Tryptophan metabolites were significantly affected, including indole, l-kynurenine, xanthurenic acid, serotonin, 5-hydroxyindoleacetic acid, and 6-hydroxymelatonin. The results from the present study provide further mechanistic insights into the mode of action of this RSV vaccine candidate and have important implications in the design of metabolic therapeutic interventions.

Role of the Airway Microbiome in Respiratory Infections and Asthma in Children

The respiratory tract can be colonized with bacterial, fungal, and viral microorganisms, and the whole of the microbiota, their genes, and the surrounding environment is collectively termed the microbiome. Increasing evidence indicates that the respiratory microbiome has an important role in respiratory health and disease and is both impacted by and potentially contributes to the severity of symptomatic respiratory viral infections and asthma in children. A deeper understanding of the complex interactions between bacteria, viruses, and the host will provide further comprehension into the drivers and mechanisms of respiratory health and disease and will impart opportunities for clinical therapies.

Respiratory syncytial virus

Respiratory syncytial virus (RSV) is the most common cause of infant hospitalization and causes a high burden of disease in the elderly, too. This enveloped negative-stranded RNA virus has been recently reclassified in the Pneumoviridae family. Infections of the respiratory cells happens when the two major surface glycoproteins, G and F, take contact with the cell receptor CX3CR1 and mediate entry by fusion, respectively. Viral mRNA transcription, genomic RNA synthesis and nucleocapsid formation occur in large cytoplasmic inclusion bodies to avoid recognition by the host innate immune response. Most progeny virions remain associated to the infected cell surface; fusion of infected with adjacent cells results in the formation of large multinucleated syncytia that eventually undergo apoptosis. Desquamated epithelial cells form the plugs that with mucus and fibrin may cause lower airway obstructions. Pathogenetic mechanism of severe RSV disease likely involve both the extent of viral replication and the host immune response. Regarding the latter, single nucleotide polymorphism analysis and genome-wide association studies showed that genetic susceptibility to severe RSV infection is likely a complex trait, in which many different host genetic variants contribute. Recent studies pointed to the fact that bronchiolitis severity depends more on the specific infecting RSV genotypes than on the amount of viral loads. A population-based surveillance system to better define RSV burden of disease would be of valuable help for implementing future vaccination programs.

Fatty Acid Metabolism is Associated With Disease Severity After H7N9 Infection

BACKGROUND

Human infections with the H7N9 virus could lead to lung damage and even multiple organ failure, which is closely associated with a high mortality rate. However, the metabolic basis of such systemic alterations remains unknown.

METHODS

This study included hospitalized patients (n = 4) with laboratory-confirmed H7N9 infection, healthy controls (n = 9), and two disease control groups comprising patients with pneumonia (n = 9) and patients with pneumonia who received steroid treatment (n = 10). One H7N9-infected patient underwent lung biopsy for histopathological analysis and expression analysis of genes associated with lung homeostasis. H7N9-induced systemic alterations were investigated using metabolomic analysis of sera collected from the four patients by using ultra-performance liquid chromatography-mass spectrometry. Chest digital radiography and laboratory tests were also conducted.

FINDINGS

Two of the four patients did not survive the clinical treatments with antiviral medication, steroids, and oxygen therapy. Biopsy revealed disrupted expression of genes associated with lung epithelial integrity. Histopathological analysis demonstrated severe lung inflammation after H7N9 infection. Metabolomic analysis indicated that fatty acid metabolism may be inhibited during H7N9 infection. Serum levels of palmitic acid, erucic acid, and phytal may negatively correlate with the extent of lung inflammation after H7N9 infection. The changes in fatty acid levels may not be due to steroid treatment or pneumonia.

INTERPRETATION

Altered structural and secretory properties of the lung epithelium may be associated with the severity of H7N9-infection-induced lung disease. Moreover, fatty acid metabolism level may predict a fatal outcome after H7N9 virus infection.