Respiratory syncytial virus genomic load and disease severity among children hospitalized with bronchiolitis: multicenter cohort studies in the United States and Finland

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.

Viral load in hospitalized infants with respiratory syncytial virus bronchiolitis: a three-way comparative analysis

Viral load measurement of Respiratory syncytial virus (RSV) in acute bronchiolitis depends on specimen collection, viral load quantification, and transport media. The aim of this study was to investigate viral load in three-way-comparative analyses; nasal swab versus nasal wash, quantitative real-time polymerase chain reaction (RT-PCR) versus cell tissue culture, and various transport media. A prospective cohort study of infants aged < 12 months, admitted to the Soroka Medical Center, due to acute bronchiolitis, was conducted. Two nasal swabs and two nasal wash samples (in UTM and VCM) were collected from each infant upon admission and after 48 h. Samples were immediately stored at -80 °C and tested at Viroclinics DDL (Rotterdam, Netherlands). Quantitative RT-PCR and quantitative virus culture were performed using tissue culture infective dose (TCID50). Spearman's correlation coefficient test assessed the correlation between the different methods, viral load, and clinical severity score. One hundred samples were collected from 13 infants (mean age 5.7 ± 3.8 months, 46% males). Twelve patients were RSV-A positive, and one was RSV-B positive. A high correlation was found between transport media- UTM and VCM (0.92, P < 0.001) and between nasal swabs and nasal wash samples (0.62, P = 0.02). RSV signals were higher in nasal wash than in swabs. PCR signals were lower in the second collection compared to the first. No correlation was found between viral load and clinical severity.    Conclusion: RSV viral load is comparable across nasal wash, nasal swabs, and various transport media. However, it did not correlate with clinical severity, probably due to the limited sample size. Broader analyses are warranted. What is Known: • Viral load measurement in Respiratory Syncytial Virus (RSV) bronchiolitis depends on specimen collection, viral load quantification, and transport media. • The COVID-19 pandemic underscored the paramount significance of proper specimen collection, notably through nasal swabs. What is New: • RSV viral load was investigated in three-way-comparative analyses. • RSV viral load correlated well across PCR and tissue culture, nasal wash and swabs, and various transport media. RSV viral load did not correlate with clinical severity.

Epidemiology and viral loads of respiratory syncytial virus in hospitalized children prior to and during COVID-19 pandemic in Hangzhou, China

Non-pharmaceutical interventions (NPIs) implemented to control SARS-CoV-2 have significantly influenced the activity of respiratory pathogens. This study investigated epidemiological changes among hospitalized patients with respiratory syncytial virus (RSV) before (2017-2019) and during (2020-2022) the COVID-19 pandemic in Hangzhou, China. We also examined viral load distribution across demographic and temporal variables. Nasopharyngeal swabs were collected and RSV loads were quantified using reverse transcriptase polymerase chain reaction (RT-qPCR). RSV epidemic characteristics, seasonal dynamics, and viral load distributions were compared between pre- and pandemic years. General linear models were employed to assess associations between viral loads and age. Among 19 742 cases, 1576 and 2092 tested positive during the pre- and pandemic years, respectively. From February to July 2020, the implementation of NPIs led to the cessation of RSV circulation. However, after these measures were relaxed, RSV cases resurged over two consecutive seasons during the pandemic, notably affecting older children compared to those in the pre-pandemic years (1.00 years, IQR: 0.50-2.00 vs. 0.58 years, IQR: 0.27-1.00, p < 0.001). Specifically, in 2021-2022, an off-season resurgence of RSV began earlier (mid-June), lasted longer (40 weeks), and involved more positive cases (1238 cases) than both 2020-2021 and pre-pandemic years. Viral load distribution demonstrated a clear age-related relationship in both pre- and pandemic years, with younger children consistently showing higher viral loads, independently of gender and season (all p-values for trends <0.001). These findings highlight the impact of NPIs on RSV epidemiology and underscore the need to prioritize RSV infection prevention in younger children from the perspective of viral load.

Association of viral loads of influenza A (H3N2) with age and care setting on presentation-a prospective study during the 2022-2023 influenza season in Spain

OBJECTIVES

The aim of this study was to analyze the viral load (VL) using cycle threshold (Ct) in patients infected with influenza A (H3N2).

METHODS

This prospective study was conducted during the 2022-2023 influenza season in sentinel, non-sentinel, and hospitalized patients of Castilla y León (Spain). Respiratory samples were obtained from nasopharyngeal swabs and analyzed by quantitative reverse transcription-polymerase chain reaction specific for influenza A (H3N2) to obtain the Ct value.

RESULTS

A total of 1047 individuals were enrolled (174 [16.6%] sentinel, 200 [19.1%] non-sentinel, 673 [64.3%] hospitalized). The mean Ct value was lower in infants, young children, and in the elderly, with a sharp increase in the last from 65 years until 90 years. In addition, the lower Ct values were observed in non-sentinel patients and then in hospitalized patients, probably because non-sentinel are outpatients in the acute phase of the influenza infection.

CONCLUSIONS

A higher VL (lower Ct value) is related to the extreme ages of life: children and the elderly. Furthermore, a higher VL is related with the care setting, being probably higher in outpatients because they are in the acute phase of the disease and slightly lower in hospitalized patients because they are attended during the post-acute phase.

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.

Bronchiolitis recovery and the use of High Efficiency Particulate Air (HEPA) Filters (The BREATHE Study): study protocol for a multi-center, parallel, double-blind, randomized controlled clinical trial

BACKGROUND

Acute viral bronchiolitis is the most common reason for hospitalization of infants in the USA. Infants hospitalized for bronchiolitis are at high risk for recurrent respiratory symptoms and wheeze in the subsequent year, and longer-term adverse respiratory outcomes such as persistent childhood asthma. There are no effective secondary prevention strategies. Multiple factors, including air pollutant exposure, contribute to risk of adverse respiratory outcomes in these infants. Improvement in indoor air quality following hospitalization for bronchiolitis may be a prevention opportunity to reduce symptom burden. Use of stand-alone high efficiency particulate air (HEPA) filtration units is a simple method to reduce particulate matter ≤ 2.5 µm in diameter (PM2.5), a common component of household air pollution that is strongly linked to health effects.

METHODS

BREATHE is a multi-center, parallel, double-blind, randomized controlled clinical trial. Two hundred twenty-eight children < 12 months of age hospitalized for the first time with bronchiolitis will participate. Children will be randomized 1:1 to receive a 24-week home intervention with filtration units containing HEPA and carbon filters (in the child's sleep space and a common room) or to a control group with units that do not contain HEPA and carbon filters. The primary objective is to determine if use of HEPA filtration units reduces respiratory symptom burden for 24 weeks compared to use of control units. Secondary objectives are to assess the efficacy of the HEPA intervention relative to control on (1) number of unscheduled healthcare visits for respiratory complaints, (2) child quality of life, and (3) average PM2.5 levels in the home.

DISCUSSION

We propose to test the use of HEPA filtration to improve indoor air quality as a strategy to reduce post-bronchiolitis respiratory symptom burden in at-risk infants with severe bronchiolitis. If the intervention proves successful, this trial will support use of HEPA filtration for children with bronchiolitis to reduce respiratory symptom burden following hospitalization.

TRIAL REGISTRATION

NCT05615870. Registered on November 14, 2022.

Measurement of the interbronchial angle in acute viral bronchiolitis

BACKGROUND

Acute viral bronchiolitis (AVB) is the most common lower airway infection in children under 2 years. Attempts to determine disease severity based on clinical and radiological manifestations are a major challenge. Measurements of the anatomy of the trachea and main bronchi are not only limited to pure anthropometry, but are also useful for better care of critically ill patients. The purpose of the study is to verify the association between measurements of the interbronchial angle (ITB) and the severity of respiratory disease.

METHODS

A cross-sectional study, which included all patients admitted to the Santo Antônio Children's Hospital, over a period of 1 year, with diagnosis of AVB by respiratory syncytial virus (RSV) was designed. ITB angle was measured and clinical characteristics were analyzed. Quantitative variables were compared and correlation analysis was performed using Pearson's correlation coefficient. A receiving operator characteristic (ROC) curve was performed. P-value <0.05 was statistically significant.

RESULTS

A total of 425 patients with AVB due to RSV were included. Most of these patients were male and the median age was 130 days, 91.11% of them required oxygen therapy through a nasal catheter, 3.3% used noninvasive ventilation and 4% used mechanical ventilation. Those who required MV or NIV and intensive care unit support were considered severe. The mean ITB was lower for these patients than for those of lesser severity (p < 0.05).

CONCLUSION

The present study demonstrates that there is an association between ITB and AVB severity. The smaller the ITB, the greater the disease severity.

Inter and intra-host diversity of RSV in hematopoietic stem cell transplant adults with normal and delayed viral clearance

Respiratory syncytial virus (RSV) infection in immunocompromised individuals often leads to prolonged illness, progression to severe lower respiratory tract infection, and even death. How the host immune environment of the hematopoietic stem cell transplant (HCT) adults can affect viral genetic variation during an acute infection is not understood well. In the present study, we performed whole genome sequencing of RSV/A or RSV/B from samples collected longitudinally from HCT adults with normal (<14 days) and delayed (≥14 days) RSV clearance who were enrolled in a ribavirin trial. We determined the inter-host and intra-host genetic variation of RSV and the effect of mutations on putative glycosylation sites. The inter-host variation of RSV is centered in the attachment (G) and fusion (F) glycoprotein genes followed by polymerase (L) and matrix (M) genes. Interestingly, the overall genetic variation was constant between normal and delayed clearance groups for both RSV/A and RSV/B. Intra-host variation primarily occurred in the G gene followed by non-structural protein (NS1) and L genes; however, gain or loss of stop codons and frameshift mutations appeared only in the G gene and only in the delayed viral clearance group. Potential gain or loss of O-linked glycosylation sites in the G gene occurred both in RSV/A and RSV/B isolates. For RSV F gene, loss of N-linked glycosylation site occurred in three RSV/B isolates within an antigenic epitope. Both oral and aerosolized ribavirin did not cause any mutations in the L gene. In summary, prolonged viral shedding and immune deficiency resulted in RSV variation, especially in structural mutations in the G gene, possibly associated with immune evasion. Therefore, sequencing and monitoring of RSV isolates from immunocompromised patients are crucial as they can create escape mutants that can impact the effectiveness of upcoming vaccines and treatments.

Neutrophil-to-Lymphocyte Ratio and the Systemic Immune-Inflammation Index: Biomarkers in Infants with Bronchiolitis: a Cross-Sectional Study

The use of a novel inflammatory indicator, the systemic immune-inflammatory index (SII), in pediatric patients with bronchiolitis remains unreported. Therefore, this study investigated the relationship between the SII and the neutrophil-to-lymphocyte ratio (NLR) in patients with respiratory syncytial virus (RSV) and non-RSV bronchiolitis and clinical severity prediction. This study analyzed the data of 155 patients aged <2 years who were hospitalized for viral bronchiolitis caused by RSV and/or other viral pathogens. The SII (platelet count × [neutrophil/lymphocyte]) was calculated and compared among patients with RSV mono-infections, other viral mono-infections, and RSV co-infections. Severity was defined by the number of days of supplemental oxygen treatment. The NLR and SII were significantly higher in the non-RSV mono-infection group than in the RSV mono-infection group, and the number of days of supplemental oxygen therapy was significantly higher in the RSV mono-infection group. No significant differences in the NLR, SII, or days of supplemental oxygen therapy were found between the RSV mono-infection and RSV co-infection groups. Although patients with RSV mono-infection showed more severe clinical findings than those without non-RSV mono-infection, the NLR and SII values were significantly higher in the non-RSV mono-infection group. Therefore, the NLR and SII do not appear to be very useful measurements for determining the severity of acute bronchiolitis attacks; however, lower NLR and SII values in the RSV group compared to the non-RSV group may be potential biomarkers for RSV infection. Therefore, further studies are warranted.

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

BACKGROUND

In infant bronchiolitis, recent evidence indicates that respiratory viruses (eg, respiratory syncytial virus [RSV], rhinovirus [RV]) contribute to the heterogeneity of disease severity. Of the potential pathobiological molecules, lipids serve as signaling molecules in airway inflammation. However, little is known about the role of the airway lipidome in between-virus heterogeneity and disease severity.

METHODS

In this multicenter prospective study of 800 infants hospitalized for RSV or RV bronchiolitis, we analyzed nasopharyngeal lipidome data. We examined discriminatory lipids between RSV and RV infection and the association of the discriminatory lipids with bronchiolitis severity, defined by positive pressure ventilation (PPV) use.

RESULTS

We identified 30 discriminatory nasopharyngeal lipid species and 8 fatty acids between RSV and RV infection. In the multivariable models adjusting for patient-level confounders, 8 lipid species-for example, phosphatidylcholine (18:2/18:2) (adjusted odds ratio [aOR], 0.23 [95% confidence interval {CI}, .11-.44]; false discovery rate [FDR] = 0.0004) and dihydroceramide (16:0) (aOR, 2.17 [95% CI, 1.12-3.96]; FDR = 0.04)-were significantly associated with the risk of PPV use. Additionally, 6 fatty acids-for example, eicosapentaenoic acid (aOR, 0.27 [95% CI, .11-.57]; FDR = 0.01)-were also significantly associated with the risk of PPV use.

CONCLUSIONS

In infants hospitalized for bronchiolitis, the nasopharyngeal lipidome plays an important role in the pathophysiology of between-virus heterogeneity and disease severity.

Clinical Outcomes of Acutely Ill Children According to Cycle Threshold Values of Respiratory Viruses Detected by Multiplex PCR Testing

In this cohort study of 800 children attending a pediatric emergency department at Oulu University Hospital, Finland with fever or respiratory symptoms, the cycle threshold values of point-of-care multiplex polymerase chain reaction testing for respiratory viruses were not associated with hospitalization, respiratory support, or need for intensive care.

Nasopharyngeal fungal subtypes of infant bronchiolitis and disease severity risk

BACKGROUND

Bronchiolitis is a leading cause of infant hospitalization. Recent research suggests the heterogeneity within bronchiolitis and the relationship of airway viruses and bacteria with bronchiolitis severity. However, little is known about the pathobiological role of fungi. We aimed to identify bronchiolitis mycotypes by integrating fungus and virus data, and determine their association with bronchiolitis severity and biological characteristics.

METHODS

In a multicentre prospective cohort study of 398 infants (age <1 year, male 59%) hospitalized for bronchiolitis, we applied clustering approaches to identify mycotypes by integrating nasopharyngeal fungus (detected in RNA-sequencing data) and virus data (respiratory syncytial virus [RSV], rhinovirus [RV]) at hospitalization. We examined their association with bronchiolitis severity-defined by positive pressure ventilation (PPV) use and biological characteristics by nasopharyngeal metatranscriptome and transcriptome data.

RESULTS

In infants hospitalized for bronchiolitis, we identified four mycotypes: A) fungiM.restrictavirusRSV/RV, B) fungiM.restrictavirusRSV, C) fungiM.globosavirusRSV/RV, D) funginot-detectedvirusRSV/RV mycotypes. Compared to mycotype A infants (the largest subtype, n = 211), mycotype C infants (n = 85) had a significantly lower risk of PPV use (7% vs. 1%, adjOR, 0.21; 95% CI, 0.02-0.90; p = 0.033), while the risk of PPV use was not significantly different in mycotype B or D. In the metatranscriptome and transcriptome data, mycotype C had similar bacterial composition and microbial functions yet dysregulated pathways (e.g., Fc γ receptor-mediated phagocytosis pathway and chemokine signaling pathway; FDR <0.05).

INTERPRETATION

In this multicentre cohort, fungus-virus clustering identified distinct mycotypes of infant bronchiolitis with differential severity risks and unique biological characteristics.

FUNDING

This study was supported by the National Institutes of Health.

Viral load: We need a new look at an old problem?

The concept of viral load was introduced in the 1980s to measure the amount of viral genetic material in a person's blood, primarily for human immunodeficiency virus (HIV). It has since become crucial for monitoring HIV infection progression and assessing the efficacy of antiretroviral therapy. However, during the coronavirus disease 2019 pandemic, the term "viral load" became widely popularized, not only for the scientific community but for the general population. Viral load plays a critical role in both clinical patient management and research, providing valuable insights for antiviral treatment strategies, vaccination efforts, and epidemiological control measures. As measuring viral load is so important, why don't researchers discuss the best way to do it? Is it simply acceptable to use raw Ct values? Relying solely on Ct values for viral load estimation can be problematic due to several reasons. First, Ct values can vary between different quantitative polymerase chain reaction assays, platforms, and laboratories, making it difficult to compare data across studies. Second, Ct values do not directly measure the quantity of viral particles in a sample and they can be influenced by various factors such as initial viral load, sample quality, and assay sensitivity. Moreover, variations in viral RNA extraction and reverse-transcription steps can further impact the accuracy of viral load estimation, emphasizing the need for careful interpretation of Ct values in viral load assessment. Interestingly, we did not observe scientific articles addressing different strategies to quantify viral load. The absence of standardized and validated methods impedes the implementation of viral load monitoring in clinical management. The variability in cell quantities within samples and the variation in viral particle numbers within infected cells further challenge accurate viral load measurement and interpretation. To advance the field and improve patient outcomes, there is an urgent need for the development and validation of tailored, standardized methods for precise viral load quantification.

Single cell transcriptomics identifies distinct profiles in pediatric acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS), termed pediatric ARDS (pARDS) in children, is a severe form of acute respiratory failure (ARF). Pathologic immune responses are implicated in pARDS pathogenesis. Here, we present a description of microbial sequencing and single cell gene expression in tracheal aspirates (TAs) obtained longitudinally from infants with ARF. We show reduced interferon stimulated gene (ISG) expression, altered mononuclear phagocyte (MNP) transcriptional programs, and progressive airway neutrophilia associated with unique transcriptional profiles in patients with moderate to severe pARDS compared to those with no or mild pARDS. We additionally show that an innate immune cell product, Folate Receptor 3 (FOLR3), is enriched in moderate or severe pARDS. Our findings demonstrate distinct inflammatory responses in pARDS that are dependent upon etiology and severity and specifically implicate reduced ISG expression, altered macrophage repair-associated transcriptional programs, and accumulation of aged neutrophils in the pathogenesis of moderate to severe pARDS caused by RSV.

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.

Respiratory Syncytial Virus-Load Kinetics and Clinical Course of Acute Bronchiolitis in Hospitalized Infants: Interim Results and Review of the Literature

Respiratory Syncytial Virus (RSV) bronchiolitis is the leading cause of hospitalization in infants. The role of RSV load in disease severity is still debated. We present the interim results of a prospective monocentric study enrolling previously healthy infants hospitalized for RSV bronchiolitis, collecting nasopharyngeal aspirates every 48 h from admission to discharge, and evaluating RSV load dynamics in relation to clinical outcome measures of bronchiolitis severity, including: need, type and duration of oxygen therapy, length of hospitalization, and the bronchiolitis clinical score calculated at admission. The results showed that the highest viral replication occurs within the first 48 hours after admission, with a significant decrease at subsequent time points (p < 0.0001). Moreover, higher RSV-RNA values were associated with the need for oxygen therapy (p = 0.03), particularly high-flow nasal cannula type (p = 0.04), and longer duration of respiratory support (p = 0.04). Finally, higher RSV load values were correlated with lower white blood cells, especially lymphocyte counts and C-reactive protein levels (p = 0.03, p = 0.04, and p = 0.01, respectively), as well as with patients of a younger age (p = 0.02). These data suggest that RSV may actively contribute to the clinical severity of bronchiolitis, together with other potential non-viral factors.

Increased RSV-A Bronchiolitis Severity in RSV-Infected Children Admitted to a Reference Center in Catalonia (Spain) Between 2014 and 2018

Between 2014 and 2018, we evaluated the severity of 687 cases of bronchiolitis caused by respiratory syncytial virus (RSV) in Catalonia, Spain. Compared to RSV-B, RSV-A cases required intensive care (adjusted relative risk (aRR) = 1.44, p < 0.01) and respiratory support (aRR = 1.07, p < 0.01) more often; hospital stay was one day longer (p < 0.01). Subgroup identification may aid clinical evaluation and seasonal healthcare planning.

RSV-CLASS -Clinical Assessment Severity Score: An easy-to-use clinical disease severity score for respiratory syncytial virus infection in hospitalized children

Respiratory syncytial virus (RSV) is the most common cause of acute respiratory tract infection in infants and young children often leading to severe disease requiring hospitalization. However, validated tools for systematic assessment of disease severity are lacking. This study aimed at creating and validating a standardized, simple-to-use disease severity score for RSV infection in children-the RSV-CLASS (Clinical Assessment Severity Score). Therefore, data from over 700 RSV-infected children over six winter seasons (2014-2020) was analyzed using univariate and multiple regression analyses for the prediction of lower respiratory tract infection (LRTI) as a proxy for a severe course of the disease. Testing a broad range of respiratory symptoms, they eventually yielded seven items. Performing stepwise selection, these were reduced to the final four items: cough, tachypnea, rales, and wheezing, each receiving one point in the proposed score named RSV-CLASS. The score was calculated for children in two cohorts A and B, one for development and one for validation, with an area under the curve of 0.90 and 0.87, respectively. With a score value of 3 or 4, 97.8% and 100% of the children, respectively, were admitted with LRTI and classified correctly. The RSV-CLASS is a disease severity score based on a neutral, analytical approach using prospective data from a large study cohort. It will contribute to systematically assessing the disease severity of RSV infection and can be used for evidence-based clinical decision-making as well as for research settings.

Type III Interferons, Viral Loads, Age, and Disease Severity in Young Children With Respiratory Syncytial Virus Infection

BACKGROUND

The interplay among respiratory syncytial virus (RSV) loads, mucosal interferons (IFN), and disease severity in RSV-infected children is poorly understood.

METHODS

Children <2 years of age with mild (outpatients) or severe (inpatients) RSV infection and healthy controls were enrolled, and nasopharyngeal samples obtained for RSV loads and innate cytokines quantification. Patients were stratified by age (0-6 and >6-24 months) and multivariable analyses performed to identify predictors of disease severity.

RESULTS

In 2015-2019 we enrolled 219 RSV-infected children (78 outpatients; 141 inpatients) and 34 healthy controls. Type I, II, and III IFN concentrations were higher in children aged >6 versus 0-6 months and, like CXCL10, they were higher in outpatients than inpatients and correlated with RSV loads (P < .05). Higher IL6 concentrations increased the odds of hospitalization (odds ratio [OR], 2.30; 95% confidence interval [CI], 1.07-5.36) only in children >6 months, while higher IFN-λ2/3 concentrations had the opposite effect irrespective of age (OR, 0.38; 95% CI, .15-.86). Likewise, higher CXCL10 concentrations decreased the odds of hospitalization (OR, 0.21; 95% CI, .08-.48), oxygen administration (OR, 0.42; 95% CI, .21-.80),PICU admission (OR, 0.39; 95% CI, .20-.73), and prolonged hospitalization (OR, 0.57; 95% CI, .32-.98) irrespective of age.

CONCLUSIONS

Children with milder RSV infection and those aged >6 months had higher concentrations of mucosal IFNs, suggesting that maturation of mucosal IFN responses are associated with protection against severe RSV disease.

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.

Cilia-related gene signature in the nasal mucosa correlates with disease severity and outcomes in critical respiratory syncytial virus bronchiolitis

Background

Respiratory syncytial virus (RSV) can cause life-threatening respiratory failure in infants. We sought to characterize the local host response to RSV infection in the nasal mucosa of infants with critical bronchiolitis and to identify early admission gene signatures associated with clinical outcomes.

Methods

Nasal scrape biopsies were obtained from 33 infants admitted to the pediatric intensive care unit (PICU) with critical RSV bronchiolitis requiring non-invasive respiratory support (NIS) or invasive mechanical ventilation (IMV), and RNA sequencing (RNA-seq) was performed. Gene expression in participants who required shortened NIS (</= 3 days), prolonged NIS (> 3 days), and IMV was compared.

Findings

Increased expression of ciliated cell genes and estimated ciliated cell abundance, but not immune cell abundance, positively correlated with duration of hospitalization in infants with critical bronchiolitis. A ciliated cell signature characterized infants who required NIS for > 3 days while a basal cell signature was present in infants who required NIS for </= 3 days, despite both groups requiring an equal degree of respiratory support at the time of sampling. Infants who required invasive mechanical ventilation had increased expression of genes involved in neutrophil activation and cell death.

Interpretation

Increased expression of cilia-related genes in clinically indistinguishable infants with critical RSV may differentiate between infants who will require prolonged hospitalization and infants who will recover quickly. Validation of these findings in a larger cohort is needed to determine whether a cilia-related gene signature can predict duration of illness in infants with critical bronchiolitis. The ability to identify which infants with critical RSV bronchiolitis may require prolonged hospitalization using non-invasive nasal samples would provide invaluable prognostic information to parents and medical providers.

Integrated relationship of nasopharyngeal airway host response and microbiome associates with bronchiolitis severity

Bronchiolitis is a leading cause of infant hospitalizations but its immunopathology remains poorly understood. Here we present data from 244 infants hospitalized with bronchiolitis in a multicenter prospective study, assessing the host response (transcriptome), microbial composition, and microbial function (metatranscriptome) in the nasopharyngeal airway, and associate them with disease severity. We investigate individual associations with disease severity identify host response, microbial taxonomical, and microbial functional modules by network analyses. We also determine the integrated relationship of these modules with severity. Several modules are significantly associated with risks of positive pressure ventilation use, including the host-type I interferon, neutrophil/interleukin-1, T cell regulation, microbial-branched-chain amino acid metabolism, and nicotinamide adenine dinucleotide hydrogen modules. Taken together, we show complex interplays between host and microbiome, and their contribution to disease severity.

Clinical and Viral Factors Associated With Disease Severity and Subsequent Wheezing in Infants With Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) causes substantial morbidity and mortality in infants and young children worldwide. Here we evaluated host demographic and viral factors associated with RSV disease severity in 325 RSV-infected infants under 1 year of age from 3 European countries during 2017-2020. Younger infants had a higher clinical severity (ReSViNET) score and were more likely to require hospitalization, intensive care, respiratory support, and/or mechanical ventilation than older infants (<3 months vs 3 to <6 months and 3 to <6 months vs ≥6 months). Older age (≥6 months vs <3 months), higher viral load, and RSV-A were associated with a greater probability of fever. RSV-A and RSV-B caused similar disease severity and had similar viral dynamics. Infants with a more severe RSV infection, demonstrated by having a higher ReSViNET score, fever, and requiring hospitalization and intensive care, were more likely to have developed subsequent wheezing at 1 year of age.

CLINICAL TRIALS REGISTRATION

NCT03756766.

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.

Application of MRT-qPCR for pathogen detection of lower respiratory tract infection

OBJECTIVE

To analyze and clarify the application value of multiplex quantitative real-time PCR (MRT-PCR) assay in detecting pathogens involved in lower respiratory tract infection (LRTI), so as to realize accurate and rapid detection of respiratory pathogens.

METHODS

Bronchial alveolar lavage fluid (BALF) specimens from 186 patients with LRTI collected in the Cangzhou Central Hospital from June 2020 to September 2021 were analyzed retrospectively. Pathogen detection was performed by both MRT-PCR and direct immunofluorescence assay (DFA), and the results of different inspection methods were compared.

RESULTS

Among the seven pathogens detected by MRT-PCR, 140 positive specimens were identified out of the 186 patients, with the top three pathogens with the highest positive rates being influenza A virus (Flu A; 36 [19.35%]), respiratory syncytial virus (RSV; 30 [16.13%]) and human adenovirus (HAdV; 23 [12.37%]), and the pathogen with the lowest positive rate being parainfluenza virus type 3 (PIV3; 9 [4.84%]). DFA showed 110 pathogen-positive specimens, and the top three pathogens with the highest positive rates were Flu A (30 [16.13%]), HAdV (21 [11.29%]) and RSV (19 [10.22%]). The total sensitivity and accuracy of MRT-PCR assay were 93.01% and 98.69% respectively, which were statistically higher than those of 48.45% and 91.24% of DFA (P<0.05). The two inspection methods showed no significant difference in specificity (99.4% for MRT-PCR assay and 97.28% for DFA) (P>0.05).

CONCLUSIONS

MRT-PCR is rapid, accurate and specific in detecting pathogens of LRTI, which significantly improves the detection rate, with reliable performance and it has high clinical application value.

Exploring Key Genes and Mechanisms in Respiratory Syncytial Virus-Infected BALB/c Mice via Multi-Organ Expression Profiles

Respiratory syncytial virus (RSV) a leading cause of pediatric and adult morbidity and mortality worldwide. It can cause complications in multiple organs, thus increasing hospital stays and costs. However, RSV-based studies have primarily focused on effects in the lungs and blood, thereby potentially neglecting critical genes and pathways. Hence, studying RSV infection via a novel multi-organ approach is important. In this study, lung, intestine, brain, and spleen tissues from six BALB/c mice (6–8 weeks old; three in control group and three in RSV-infected group) were subjected to RNA sequencing. Differentially expressed genes (DEGs) in each organ were obtained and functional enrichment analysis was performed. We first used CIBERSORT to evaluate the immune-infiltration landscape. Subsequently, common DEGs (co-DEGs) among the four organs were analyzed to identify key genes and pathways. After quantitative reverse transcription-polymerase chain reaction, western blotting, and external validation analysis of key hub genes, their correlation with immune cells and potential functions were explored. We found that the host response to RSV infection varied among the four organs regarding gene expression profiles and immune cell infiltration. Analysis of the 16 co-DEGs indicated enrichment in the platelet and neutrophil degranulation pathways. Importantly, the key gene hemopexin (Hpx) was strongly correlated with the immune cell fraction in the lungs and may participate in the regulation of platelet activation and immune response.

Association of Growth Trajectory Profiles with Asthma Development in Infants Hospitalized with Bronchiolitis

BACKGROUND

Little is known about the relationship of longitudinal growth trajectory in early life with asthma development, particularly in infants with bronchiolitis (a high-risk population).

OBJECTIVE

Among infants with bronchiolitis, we aimed to identify growth trajectory profiles and determine their longitudinal relationship with the risk for developing childhood asthma.

METHODS

A multicenter prospective study enrolled infants (aged <1 year) hospitalized for bronchiolitis. We identified growth trajectory profiles-derived from body mass index-for-age at ages 0, 6, 12, 15, 18, 24, and 36 months by using a longitudinal clustering method. We examined associations between growth trajectory profiles and asthma development by age 5 years.

RESULTS

The analytic cohort consists of 880 infants hospitalized for bronchiolitis (median age, 3 months). Overall, 26% developed asthma by age 5 years. The longitudinal clustering identified 5 distinct profiles: persistent low growth (27%), normative growth (33%), transient overweight (21%), late-onset overweight (16%), and persistent obesity (3%) profiles. In multivariable model, compared with children with a normative profile, those with a persistent obesity profile had significantly higher risks of developing asthma (24% vs 38%, odds ratio [OR]: 2.55, 95% confidence interval [CI]: 1.07-6.09, P = .03). Among children with a persistent obesity profile, those without allergic predisposition had significantly higher risks of asthma (OR: 3.02, 95% CI: 1.05-8.64, P = .04 in the nonparental allergic history group; OR: 3.18, 95% CI: 1.02-9.92, P = .047 in the non-IgE sensitization group), whereas those with allergic predisposition were not at increased risk.

CONCLUSIONS

This multicenter cohort study of infants with bronchiolitis demonstrated distinct growth trajectory profiles that have differential risks for developing asthma.

Serum periostin among infants with severe bronchiolitis and risk of developing asthma: A prospective multicenter cohort study

BACKGROUND

Infants hospitalized for bronchiolitis (severe bronchiolitis) are at high risk for developing childhood asthma. However, the pathobiological link between these conditions remains unclear. We examined the longitudinal relationship of periostin (an extracellular matrix protein upregulated in response to type 2 inflammation) during bronchiolitis with the subsequent development of asthma.

METHODS

In a 17-center prospective cohort study of infants (aged <1 year) with severe bronchiolitis, we measured the serum periostin level at hospitalization and grouped infants into 3 groups: low, intermediate, and high levels. We examined their association with asthma development by age 6 years and investigated effect modification by allergic predisposition (eg, infant's IgE sensitization).

RESULTS

The analytic cohort consists of 847 infants with severe bronchiolitis (median age, 3 months). Overall, 28% developed asthma by age 6 years. In the multivariable model adjusting for nine patient-level factors, compared to the low periostin group, the asthma risk was significantly higher among infants in the intermediate group (23% vs. 32%, OR 1.68, 95%CI 1.12-2.51, p = .01) and non-significantly higher in the high-level group (28%, OR 1.29, 95%CI 0.86-1.95, p = .22). In the stratified analysis, infants with IgE sensitization had a significantly higher risk for developing asthma (intermediate group, OR 4.76, 95%CI 1.70-13.3, p = .002; high group, OR 3.19, 95%CI 1.08-9.36, p = .04). By contrast, infants without IgE sensitization did not have a significantly higher risk (p > .15).

CONCLUSIONS

In infants with severe bronchiolitis, serum periostin level at bronchiolitis hospitalization was associated with asthma risk by age 6 years, particularly among infants with an allergic predisposition.

Identifying and predicting severe bronchiolitis profiles at high risk for developing asthma: Analysis of three prospective cohorts

BACKGROUND

Bronchiolitis is the leading cause of infants hospitalization in the U.S. and Europe. Additionally, bronchiolitis is a major risk factor for the development of childhood asthma. Growing evidence suggests heterogeneity within bronchiolitis. We sought to identify distinct, reproducible bronchiolitis subgroups (profiles) and to develop a decision rule accurately predicting the profile at the highest risk for developing asthma.

METHODS

In three multicenter prospective cohorts of infants (age < 12 months) hospitalized for bronchiolitis in the U.S. and Finland (combined n = 3081) in 2007-2014, we identified clinically distinct bronchiolitis profiles by using latent class analysis. We examined the association of the profiles with the risk for developing asthma by age 6-7 years. By performing recursive partitioning analyses, we developed a decision rule predicting the profile at highest risk for asthma, and measured its predictive performance in two separate cohorts.

FINDINGS

We identified four bronchiolitis profiles (profiles A-D). Profile A (n = 388; 13%) was characterized by a history of breathing problems/eczema and non-respiratory syncytial virus (non-RSV) infection. In contrast, profile B (n = 1064; 34%) resembled classic RSV-induced bronchiolitis. Profile C (n = 993; 32%) was comprised of the most severely ill group. Profile D (n = 636; 21%) was the least-ill group. Profile A infants had a significantly higher risk for asthma, compared to profile B infants (38% vs. 23%, adjusted odds ratio [adjOR] 2⋅57, 95%confidence interval [CI] 1⋅63-4⋅06). The derived 4-predictor (RSV infection, history of breathing problems, history of eczema, and parental history of asthma) decision rule strongly predicted profile A-e.g., area under the curve [AUC] of 0⋅98 (95%CI 0⋅97-0⋅99), sensitivity of 1⋅00 (95%CI 0⋅96-1⋅00), and specificity of 0⋅90 (95%CI 0⋅89-0⋅93) in a validation cohort.

INTERPRETATION

In three prospective cohorts of infants with bronchiolitis, we identified clinically distinct profiles and their longitudinal relationship with asthma risk. We also derived and validated an accurate prediction rule to determine the profile at highest risk. The current results should advance research into the development of profile-specific preventive strategies for asthma.

Exchange Protein Directly Activated by cAMP 2 Enhances Respiratory Syncytial Virus-Induced Pulmonary Disease in Mice

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in young children. It is also a significant contributor to upper respiratory tract infections, therefore, a major cause for visits to the pediatrician. High morbidity and mortality are associated with high-risk populations including premature infants, the elderly, and the immunocompromised. However, no effective and specific treatment is available. Recently, we discovered that an exchange protein directly activated by cyclic AMP 2 (EPAC2) can serve as a potential therapeutic target for RSV. In both lower and upper epithelial cells, EPAC2 promotes RSV replication and pro-inflammatory cytokine/chemokine induction. However, the overall role of EPAC2 in the pulmonary responses to RSV has not been investigated. Herein, we found that EPAC2-deficient mice (KO) or mice treated with an EPAC2-specific inhibitor showed a significant decrease in body weight loss, airway hyperresponsiveness, and pulmonary inflammation, compared with wild-type (WT) or vehicle-treated mice. Overall, this study demonstrates the critical contribution of the EPAC2-mediated pathway to airway diseases in experimental RSV infection, suggesting the possibility to target EPAC2 as a promising treatment modality for RSV.

Viral Bronchiolitis in Children: Less is More

Jerath N. Viral Bronchiolitis in Children: Less is More. Indian J Crit Care Med 2021;25(11):1219-1220.

Host inflammatory response is the major marker of severe respiratory syncytial virus infection in older adults

OBJECTIVES

We aim to study the viral kinetics and host inflammatory response of RSV infection in older adults, and their correlation with disease severity.

METHODS

We performed a prospective observational study in adults with RSV infection. We serially collected nasal-throat swabs for quantification of RSV-A and RSV-B viral load, and peripheral blood samples for measurement of cytokine/chemokine concentrations. The study endpoints were (i) requiring supplemental oxygen therapy, and (ii) non-invasive ventilation, intensive care, or died within 30 days of admission. We performed multivariable logistic regression models to identify independent variables for severe disease.

RESULTS

We enrolled 71 hospitalized patients and 10 outpatients treated for RSV infection (median age 75 years, 51% male, and 74% with comorbidities). Among hospitalized patients, 61% required supplemental oxygen therapy, and 18% had severe disease requiring non-invasive ventilation or intensive care, or died within 30 days. Inflammatory cytokine/chemokines IL-6, CXCL8/IL-8, CXCL9/MIG and CXCL10/IP-10 increased significantly during the acute phase of illness. IL-6 concentration was independently associated with severe disease after adjusting for confounding factors. RSV viral load was not associated with disease severity throughout the course of illness.

CONCLUSION

Host inflammatory response is a major marker of severe disease in older adults with RSV infection.

Systematic review on the association between respiratory virus real-time PCR cycle threshold values and clinical presentation or outcomes

Objectives

It is unclear whether real-time (rt)-PCR cycle threshold (Ct) values can be utilized to guide clinical and infection-control decisions. This systematic review assesses the association between respiratory pathogen rt-PCR Ct values and clinical presentation or outcomes.

Methods

We searched MEDLINE, EMBASE and Cochrane library databases on 14–17 January 2020 for studies reporting the presence or absence of an association between Ct values and clinical presentation or outcomes, excluding animal studies, reviews, meta-analyses, and non-English language studies.

Results

Among 33 studies identified (reporting on between 9 and 4918 participants by pathogen), influenza (n = 11 studies; 4918 participants), human rhinovirus (HRV, n = 11; 2012) and respiratory syncytial virus (RSV, n = 8; 3290) were the most-studied pathogens. Low influenza Ct values were associated with mortality in 1/3 studies, with increased disease severity/duration or ICU admission in 3/9, and with increased hospitalization or length of hospital stay (LOS) in 1/6. Low HRV Ct values were associated with increased disease severity/duration or ICU admission in 3/10 studies, and with increased hospitalization or LOS in 1/3. Low RSV Ct values were associated with increased disease severity/duration or ICU admission in 3/6 studies, and with increased hospitalization or LOS in 4/4. Contradictory associations were also identified for other respiratory pathogens.

Conclusions

Respiratory infection Ct values may inform clinical and infection-control decisions. However, the study heterogeneity observed in this review highlights the need for standardized workflows to utilize Ct values as a proxy of genomic load and confirm their value for respiratory infection management.

Comparison of Mid-Turbinate and Nasopharyngeal Specimens for Molecular Detection of SARS-CoV-2 Among Symptomatic Outpatients at a Pediatric Drive-Through Testing Site

BACKGROUND

Nasopharyngeal (NP) specimen testing by reverse transcriptase polymerase chain reaction (RT-PCR) is the standard of care for detecting SARS-CoV-2. Data comparing the sensitivity and specificity of the NP specimen to the less invasive, mid-turbinate (MT) nasal specimen in children are limited.

METHODS

Paired clinical NP and research MT specimens were collected from children <18 years with respiratory symptoms and tested by molecular assays to detect SARS-CoV-2 RNA. Sensitivity, specificity, and agreement (Cohen's kappa [κ]) were calculated for research MT specimens compared to the clinical NP specimens.

RESULTS

Out of 907 children, 569 (62.7%) had parental consent and child assent when appropriate to participate and provided paired MT and NP specimens a median of 4 days after symptom onset (range 1-14 days). 16.5% (n = 94) of MT specimens were positive for SARS-CoV-2 compared with 20.0% (n = 114) of NP specimens. The sensitivity of research MT compared to clinical NP specimens was 82.5% (95% CI: 74.2%, 88.9%), specificity was 100.0% (95% CI: 99.2%, 100.0%), and overall agreement was 96.1% (κ = 0.87). The sensitivity of MT specimens decreased with time from 100% (95% CI: 59.0%, 100.0%) on day 1 of illness to 82.1% (95% CI: 73.8%, 88.7%) within 14 days of illness onset; sensitivity was generally >90% when specimens were collected within the first week of illness.

CONCLUSION

MT specimens, particularly those collected within the first week of illness, have moderately reduced sensitivity and equivalent specificity to less-tolerated NP specimens in pediatric outpatients. MT specimen use in children may represent a viable alternative to NP specimen collection.

Epidemiology of respiratory syncytial virus in a community birth cohort of infants in the first 2 years of life

Respiratory syncytial virus (RSV) is the most common virus identified in children hospitalised with acute respiratory infections. However, less is known about RSV in community settings. This report describes RSV epidemiology in the community, including acute illness episodes, healthcare burden, and risk factors in Australian children during the first 2-years of life. A community-based, birth cohort from Brisbane, Australia, followed children until their second birthday. Parents completed daily respiratory symptom and illness-burden diaries. Weekly parent-collected nasal swabs were analysed for RSV by real-time polymerase chain reaction assays. Serum RSV-neutralising antibodies were assayed at age 3 years. Overall, 158 children provided 11,216 swabs, of which 104 were RSV-positive (85 incident episodes). RSV incidence in the first 2 years of life was 0.46 (95% CI = 0.37-0.58) episodes per child-year. Incidence increased with age and formal childcare attendance and was highest in autumn. Of 82 episodes linked with symptom data, 60 (73.2%) were symptomatic, 28 (34.1%) received community-based medical care, and 2 (2.4%) led to hospitalisation. Viral load was higher in symptomatic than asymptomatic infections. In 72 children, RSV-specific antibody seroprevalence was 94.4% at age 3 years.Conclusion: RSV incidence increased after age 6-months with approximately three-quarters of infections symptomatic and most infections treated in the community. What is known •RSV is a major cause of hospitalisation for acute lower respiratory infections in infants and young children, especially in the first 6 months of life. •However, limited data exist on the overall burden in young children at the community level. What is new •RSV incidence in the community increases after age 6 months, and by 3 years, most children have been infected. •About one-quarter of RSV infections were asymptomatic in children aged < 2 years, and approximately 60% of children with RSV-related symptoms had a healthcare contact of any kind with most managed within the community.

Immune profiles provide insights into respiratory syncytial virus disease severity in young children

Respiratory syncytial virus (RSV) is associated with major morbidity in infants, although most cases result in mild disease. The pathogenesis of the disease is incompletely understood, especially the determining factors of disease severity. A better characterization of these factors may help with development of RSV vaccines and antivirals. Hence, identification of a "safe and protective" immunoprofile induced by natural RSV infection could be used as a as a surrogate of ideal vaccine-elicited responses in future clinical trials. In this study, we integrated blood transcriptional and cell immune profiling, RSV loads, and clinical data to identify factors associated with a mild disease phenotype in a cohort of 190 children <2 years of age. Children with mild disease (outpatients) showed higher RSV loads, greater induction of interferon (IFN) and plasma cell genes, and decreased expression of inflammation and neutrophil genes versus children with severe disease (inpatients). Additionally, only infants with severe disease had increased numbers of HLA-DR^low monocytes, not present in outpatients. Multivariable analyses confirmed that IFN overexpression was associated with decreased odds of hospitalization, whereas increased numbers of HLA-DR^low monocytes were associated with increased risk of hospitalization. These findings suggest that robust innate immune responses are associated with mild RSV infection in infants.

Integrated omics endotyping of infants with respiratory syncytial virus bronchiolitis and risk of childhood asthma

Respiratory syncytial virus (RSV) bronchiolitis is not only the leading cause of hospitalization in U.S. infants, but also a major risk factor for asthma development. While emerging evidence suggests clinical heterogeneity within RSV bronchiolitis, little is known about its biologically-distinct endotypes. Here, we integrated clinical, virus, airway microbiome (species-level), transcriptome, and metabolome data of 221 infants hospitalized with RSV bronchiolitis in a multicentre prospective cohort study. We identified four biologically- and clinically-meaningful endotypes: A) clinicalclassicmicrobiomeM. nonliquefaciensinflammationIFN-intermediate, B) clinicalatopicmicrobiomeS. pneumoniae/M. catarrhalisinflammationIFN-high, C) clinicalseveremicrobiomemixedinflammationIFN-low, and D) clinicalnon-atopicmicrobiomeM.catarrhalisinflammationIL-6. Particularly, compared with endotype A infants, endotype B infants-who are characterized by a high proportion of IgE sensitization and rhinovirus coinfection, S. pneumoniae/M. catarrhalis codominance, and high IFN-α and -γ response-had a significantly higher risk for developing asthma (9% vs. 38%; OR, 6.00: 95%CI, 2.08-21.9; P = 0.002). Our findings provide an evidence base for the early identification of high-risk children during a critical period of airway development.

Viral load of respiratory syncytial virus among children from primary care and hospital settings admitted to a university hospital in Brazil (2009-2013)

Respiratory syncytial virus (RSV) is a relevant cause of acute respiratory infection among children. Viral replication and immune conditions may account for severity. RSV viral load (VL) was assessed in 486 children (290 hospitalized and 196 from primary care) attended at São Paulo Hospital from 2009 to 2013. VL was calculated by real-time reverse transcription-polymerase chain reaction and expressed in Log10 RNA copies/mL. Coinfection with rhinovirus (RV) and influenza A virus was also tested. Young children (<1 year of age) had a higher mean VL than older children at primary care (6.35 and 4.34 Log10 RNA copies/mL, respectively; P = .0006). Conversely, hospitalized children ≥2 years of age, presented higher mean VL compared with the same age children of primary care (6.10 and 4.26, respectively; P = .0024). RV was the most codetected virus in RSV positive patients (20% from primary care and 14% in hospitalized), and influenza A virus was found in 11% of primary care and 0.4% in hospitalized children with RSV, without RSV VL association (P = .2903). These findings may guide future therapies and immunization policies considering the role of viral load on clinical presentation among older hospitalized children and also the change of infection transmissions.

Epidemiology of Bronchiolitis in Hospitalized Infants at Tawam Hospital, Al Ain, United Arab Emirates

Background

Bronchiolitis is the commonest lower respiratory tract infection, found worldwide in children < 2 years of age. Over sixty percent of cases are caused by Respiratory Syncytial Virus (RSV). The disease is known to have significant morbidity, mortality and health care costs. Its seasonal variability, manifestations and complications vary between countries. The aim of this study was to determine the epidemiological and clinical characteristics of infants hospitalized with bronchiolitis in Al Ain City, United Arab Emirates.

Methods

Retrospective observational chart review was made of an unselected cohort of infants ≤ 2 years admitted to the pediatric department of Tawam hospital over a 3-year period and discharged with the diagnosis of bronchiolitis. Epidemiological data and risk factors were analyzed.

Results

RSV was the commonest pathogen (51%). Hospitalizations occurred year-round but increased significantly in December and January. The patients' median age was 5.8 months with a male predominance (male:female ratio of 1.5:1.0). The mean age at admission was 6.6 months and presentation occurred, on average, 2.9 days after the onset of the symptoms. The majority (94%) had respiratory distress on presentation. Chest x-ray was performed in 80% of the patients. Most children received bronchodilator therapy and oxygen therapy was administered to 42%. The mean duration of hospital stay was 3 days.

Conclusion

Bronchiolitis remains a common reason for hospital admission and carries significant morbidity. RSV is the primarily responsible virus for hospital admissions and morbidity.A better understanding of the burden of bronchiolitis in our setting would enable better planning and use of hospital resources to minimize its short and long-term sequelae.

Seasonality, molecular epidemiology, and virulence of Respiratory Syncytial Virus (RSV): A perspective into the Brazilian Influenza Surveillance Program

Background

Respiratory Syncytial Virus (RSV) is the main cause of pediatric morbidity and mortality. The complex evolution of RSV creates a need for worldwide surveillance, which may assist in the understanding of multiple viral aspects.

Objectives

This study aimed to investigate RSV features under the Brazilian Influenza Surveillance Program, evaluating the role of viral load and genetic diversity in disease severity and the influence of climatic factors in viral seasonality.

Methodology

We have investigated the prevalence of RSV in children up to 3 years of age with severe acute respiratory infection (SARI) in the state of Espirito Santo (ES), Brazil, from 2016 to 2018. RT-qPCR allowed for viral detection and viral load quantification, to evaluate association with clinical features and mapping of local viral seasonality. Gene G sequencing and phylogenetic reconstruction demonstrated local genetic diversity.

Results

Of 632 evaluated cases, 56% were caused by RSV, with both subtypes A and B co-circulating throughout the years. A discrete inverse association between average temperature and viral circulation was observed. No correlation between viral load and disease severity was observed, but children infected with RSV-A presented a higher clinical severity score (CSS), stayed longer in the hospital, and required intensive care, and ventilatory support more frequently than those infected by RSV-B. Regarding RSV diversity, some local genetic groups were observed within the main genotypes circulation RSV-A ON1 and RSV-B BA, with strains showing modifications in the G gene amino acid chain.

Conclusion

Local RSV studies using the Brazilian Influenza Surveillance Program are relevant as they can bring useful information to the global RSV surveillance. Understanding seasonality, virulence, and genetic diversity can aid in the development and suitability of antiviral drugs, vaccines, and assist in the administration of prophylactic strategies.

The Association between Weather Conditions and Admissions to the Paediatric Intensive Care Unit for Respiratory Syncytial Virus Bronchiolitis

Respiratory syncytial virus (RSV) bronchiolitis is a leading cause of global child morbidity and mortality. Every year, seasonal RSV outbreaks put high pressure on paediatric intensive care units (PICUs) worldwide, including in the Netherlands, and this burden appears to be increasing. Weather conditions have a strong influence on RSV activity, and climate change has been proposed as a potential important determinant of future RSV-related health care utilisation. In this national study spanning a total of 13 years with 2161 PICU admissions for RSV bronchiolitis, we aimed (1) to identify meteorological variables that were associated with the number of PICU admissions for RSV bronchiolitis in the Netherlands and (2) to determine if longitudinal changes in these variables occurred over time as a possible explanation for the observed increase in PICU burden. Poisson regression modelling was used to identify weather variables (aggregated in months and weeks) that predicted PICU admissions, and linear regression analysis was used to assess changes in the weather over time. Maximum temperature and global radiation best predicted PICU admissions, with global radiation showing the most stable strength of effect in both month and week data. However, we did not observe a significant change in these weather variables over the 13-year time period. Based on our study, we could not identify changing weather conditions as a potential contributing factor to the increased RSV-related PICU burden in the Netherlands.

Detection of respiratory syncytial virus defective genomes in nasal secretions is associated with distinct clinical outcomes

Respiratory syncytial virus (RSV) causes respiratory illness in children, immunosuppressed individuals and the elderly. However, the viral factors influencing the clinical outcome of RSV infections remain poorly defined. Defective viral genomes (DVGs) can suppress virus replication by competing for viral proteins and by stimulating antiviral immunity. We studied the association between detection of DVGs of the copy-back type and disease severity in three RSV A-confirmed cohorts. In hospitalized children, detection of DVGs in respiratory samples at or around the time of admission associated strongly with more severe disease, higher viral load and a stronger pro-inflammatory response. Interestingly, in experimentally infected adults, the presence of DVGs in respiratory secretions differentially associated with RSV disease severity depending on when DVGs were detected. Detection of DVGs early after infection associated with low viral loads and mild disease, whereas detection of DVGs late after infection, especially if DVGs were present for prolonged periods, associated with high viral loads and severe disease. Taken together, we demonstrate that the kinetics of DVG accumulation and duration could predict clinical outcome of RSV A infection in humans, and thus could be used as a prognostic tool to identify patients at risk of worse clinical disease.

Association of Viral Load With Disease Severity in Outpatient Children With Respiratory Syncytial Virus Infection

BACKGROUND

There are scarce data on whether viral load affects the severity of respiratory syncytial virus (RSV) disease in outpatient children.

METHODS

We analyzed the association between viral load and disease severity among children who participated in a prospective cohort study of respiratory infections. The children were examined and nasal swabs for the detection of RSV were obtained during each respiratory illness. Quantification of RSV load was based on the cycle threshold (Ct) value. For the primary analysis, the children were divided into 2 groups: higher (Ct < 27) and lower viral load (Ct ≥ 27).

RESULTS

Among 201 episodes of RSV infection, children with higher viral load had significantly longer median durations of rhinitis (8 vs 6 days; P = .0008), cough (8 vs 6 days; P = .034), fever (2 vs 1 days; P = .018), and any symptom (10 vs 8 days; P = .024) than those with lower viral load. There were statistically significant negative correlations between the Ct values and durations of all measured symptoms.

CONCLUSIONS

Our findings support the concept that viral load drives the severity of RSV disease in children. Reducing the viral load by RSV antivirals might provide substantial benefits to outpatient children.

Age-dependent Interactions Among Clinical Characteristics, Viral Loads and Disease Severity in Young Children With Respiratory Syncytial Virus Infection

BACKGROUND

Age-dependent differences in clinical presentation and viral loads in infants and young children with respiratory syncytial virus (RSV) infection, and their correlation with disease severity are poorly defined.

METHODS

Previously healthy children <2 years old with mild (outpatients) and severe (inpatients) RSV infection were enrolled and viral loads measured by polymerase chain reaction in nasopharyngeal swabs. Patients were stratified by age in 0-<3, 3-6 and >6-24 months, and multivariable analyses were performed to identify clinical and viral factors associated with severe disease.

RESULTS

From 2014 to 2018, we enrolled 534 children with RSV infection, 130 outpatients with mild RSV infection and 404 inpatients with severe RSV disease. Median duration of illness was 4 days for both groups, yet viral loads were higher in outpatients than in inpatients (P < 0.001). In bivariate analyses, wheezing was more frequent in outpatients of older age (>3 months) than in inpatients (P < 0.01), while fever was more common in inpatients than outpatients (P < 0.01) and its frequency increased with age. Adjusted analyses confirmed that increased work of breathing and fever were consistently associated with hospitalization irrespective of age, while wheezing in infants >3 months, and higher RSV loads in children >6-24 months were independently associated with reduced disease severity.

CONCLUSIONS

Age had a significant impact defining the interactions among viral loads, specific clinical manifestations and disease severity in children with RSV infection. These observations highlight the importance of patient stratification when evaluating interventions against RSV.

The importance of viral load in the severity of acute bronchiolitis in hospitalized infants

OBJECTIVE

The relationship between viral load and the clinical evolution of bronchiolitis is controversial. Therefore, we aimed to analyze viral loads in infants hospitalized for bronchiolitis.

METHODS

We tested for the presence of human respiratory syncytial virus (HRSV) or human rhinovirus (HRV) using quantitative molecular tests of nasopharyngeal secretions and recorded severity outcomes.

RESULTS

We included 70 infants [49 (70%) HRSV, 9 (13%) HRV and 12 (17%) HRSV+HRV]. There were no differences among the groups according to the outcomes analyzed individually. Clinical scores showed greater severity in the isolated HRSV infection group. A higher isolated HRSV viral load was associated with more prolonged ventilatory support, oxygen therapy, and hospitalization days, even after adjustment for the age and period of nasopharyngeal secretion collection. In the co-infection groups, there was a longer duration of oxygen therapy when the HRSV viral load was predominant. Isolated HRV infection and co-infection with a predominance of HRV were not associated with severity.

CONCLUSION

Higher HRSV viral load in isolated infections and the predominance of HRSV in co-infections, independent of viral load, were associated with greater severity. These results contribute to the development of therapeutic and prophylactic approaches and a greater understanding of the pathophysiology of bronchiolitis.

Enterovirus genomic load and disease severity among children hospitalised with hand, foot and mouth disease

BACKGROUND

Examining associations between viral genomic loads of enteroviruses and clinical severity is important for promoting and improving development of antiviral drugs related to hand, foot and mouth disease (HFMD).

METHODS

Throat swabs were collected from HFMD cases at acute phase of illness using a standardized technique in a prospective study. The viral genomic load was categorized into low, medium, and high groups using parameters of real-time reverse transcription-polymerase chain reaction. The clinical severities were assessed with four indicators, respectively.

FINDINGS

We analysed 1109 HFMD cases, including 538 children with CV-A6, 231 with CV-A16, 156 with EV-A71, 78 with CV-A10, 59 with CV-A4, and 47 with CV-A2. EV-A71 genomic load categories were associated with risks of diagnoses of CNS complications (p = 0.016), requiring systemic corticosteroids or IVIG (p = 0.011), intensive care unit admission (p = 0.002) and length of hospital stay over 5 days (p = 0.048). In the multivariate analyses, point estimates of adjusted odds ratio (OR) tended to increase with viral genomic loads for all four severe outcomes and ORs of highest viral genomic load were all significantly larger than one for EV-A71.

INTERPRETATION

HFMD clinical severities positively associate with viral genomic loads of EV-A71 in throat swabs. Specific antiviral drugs should be developed to reduce enterovirus load and to alleviate the clinical severities for HFMD cases.

FUNDING

National Science Fund for Distinguished Young Scholars.