Defining Age-specific Relationships of Respiratory Syncytial Virus and Rhinovirus Species in Hospitalized Children With Acute Wheeze

Real time monitoring of respiratory viral infections in cohort studies using a smartphone app

Cohort studies investigating respiratory disease pathogenesis aim to pair mechanistic investigations with longitudinal virus detection but are limited by the burden of methods tracking illness over time. In this study, we explored the utility of a purpose-built AERIAL TempTracker smartphone app to assess real-time data collection and adherence monitoring and overall burden to participants, while identifying symptomatic respiratory illnesses in two birth cohort studies. We observed strong adherence with daily app usage over the six-month study period, with positive feedback from participant families. A total of 648 symptomatic respiratory illness events were identified with significant variability between individuals in the frequency, duration, and virus detected. Collectively, our data show that a smartphone app provides a reliable method to capture the longitudinal virus data in cohort studies which facilitates the understanding of early life infections in chronic respiratory disease development.

Impaired interferon response in plasmacytoid dendritic cells from children with persistent wheeze

BACKGROUND

Impaired interferon response and allergic sensitization may contribute to virus-induced wheeze and asthma development in young children. Plasmacytoid dendritic cells (pDCs) play a key role in antiviral immunity as critical producers of type I interferons. pDCs also express the high-affinity IgE receptor through which type I interferon production may be negatively regulated. Whether antiviral function of pDCs is associated with recurrent episodes of wheeze in young children is not well understood.

OBJECTIVE

We sought to evaluate the phenotype and function of circulating pDCs in children with a longitudinally defined wheezing phenotype.

METHODS

We performed multiparameter flow cytometry on PBMCs from 38 children presenting to the emergency department with an acute episode of respiratory wheeze and 19 controls. RNA sequencing on isolated pDCs from the same individuals was also performed. For each subject, their longitudinal exacerbation phenotype was determined using the Western Australia public hospital database.

RESULTS

We observed a significant depletion of circulating pDCs in young children with a persistent phenotype of wheeze. The same individuals also displayed upregulation of the FcεRI on their pDCs. Based on transcriptomic analysis, pDCs from these individuals did not mount a robust systemic antiviral response as observed in children who displayed a nonrecurrent wheezing phenotype.

CONCLUSIONS

Our data suggest that circulating pDC phenotype and function are altered in young children with a persistent longitudinal exacerbation phenotype. Expression of high-affinity IgE receptor is increased and their function as major interferon producers is impaired during acute exacerbations of wheeze.

Patterns of Non-influenza Respiratory Viruses Among Severe Acute Respiratory Infection Cases in Burkina Faso: A Surveillance Study

BACKGROUND

Although influenza viruses cause only one-fifth of severe acute respiratory infections (SARI) in Burkina Faso, the other viral causes of SARI remain poorly investigated to inform clinical and preventive decision making.

METHODS

Between 2016 and 2019, we prospectively enrolled inpatients meeting the World Health Organization (WHO) case definition of SARI in Burkina Faso. Results of viral etiologies among inpatients tested negative for influenza using the Fast Track Diagnostics Respiratory Kits (FTD-33) were reported.

RESULTS

Of 1541 specimens tested, at least one respiratory virus was detected in 76.1% of the 1231 specimens negative for influenza virus. Human rhinoviruses (hRVs) were the most detected pathogens (476; 38.7%), followed by human adenoviruses (hAdV) (17.1%, 210/1231), human respiratory syncytial virus (hRSV) (15.4%, 189/1231), enterovirus (EnV) (11.2%, 138/1231), human bocavirus (hBoV) (7.9%, 97/1231), parainfluenza 3 (hPIV3) (6.1%, 75/1231), human metapneumovirus (hMPV) (6.0%,74/1321), parainfluenza 4 (hPIV4) (4.1%, 51/1231), human coronavirus OC43 (hCoV-OC43) (3.4%, 42/1231), human coronavirus HKU1(hCoV-HKU1) (2.7%, 33/1231), human coronavirus NL63 (hCoV-NL63) (2.5%, 31/1231), parainfluenza 1 (hPIV1) (2.0%, 25/1231), parainfluenza 2 (hPIV2) (1.8%, 22/1231), human parechovirus (PeV) (1.1%, 14/1231), and human coronavirus 229E (hCoV-229E) (0.9%, 11/1231). Among SARI cases, infants aged 1-4 years were mostly affected (50.7%; 622/1231), followed by those <1 year of age (35.7%; 438/1231). Most detected pathogens had year-long circulation patterns, with seasonal peaks mainly observed during the cold and dry seasons.

CONCLUSION

Several non-influenza viruses are cause of SARI in Burkina Faso. The integration of the most common pathogens into the routine influenza surveillance system might be beneficial.

The Role of Lung Function in Determining Which Children Develop Asthma

Longitudinal studies have demonstrated that altered indices of airway function, assessed shortly after birth, are a risk factor for the subsequent development of wheezing illnesses and asthma, and that these indices predict airway size and airway wall thickness in adult life. Pre- and postnatal factors that directly alter early airway function, such as extreme prematurity and cigarette smoke, may continue to affect airway function and, hence, the risks for wheeze and asthma. Early airway function and an associated asthma risk may also be indirectly influenced by immune system responses, respiratory viruses, the airway microbiome, genetics, and epigenetics, especially if they affect airway epithelial dysfunction. Few if any interventions, apart from smoking avoidance, have been proven to alter the risks of developing asthma, but vitamin C supplementation to pregnant smokers may help decrease the effects of in utero smoke on offspring lung function. We conclude that airway size and the factors influencing this play an important role in determining the risk for asthma across the lifetime. Progress in asthma prevention is long overdue and this may benefit from carefully designed interventions in well-phenotyped longitudinal birth cohorts with early airway function assessments monitored through to adulthood.

IFN-γ Attenuates Eosinophilic Inflammation but Is Not Essential for Protection against RSV-Enhanced Asthmatic Comorbidity in Adult Mice

The susceptibility to respiratory syncytial virus (RSV) infection in early life has been associated with a deficient T-helper cell type 1 (Th1) response. Conversely, healthy adults generally do not exhibit severe illness from RSV infection. In the current study, we investigated whether Th1 cytokine IFN-γ is essential for protection against RSV and RSV-associated comorbidities in adult mice. We found that, distinct from influenza virus, prior RSV infection does not induce significant IFN-γ production and susceptibility to secondary Streptococcus pneumoniae infection in adult wild-type (WT) mice. In ovalbumin (OVA)-induced asthmatic mice, RSV super-infection increases airway neutrophil recruitment and inflammatory lung damage but has no significant effect on OVA-induced eosinophilia. Compared with WT controls, RSV infection of asthmatic Ifng^−/− mice results in increased airway eosinophil accumulation. However, a comparable increase in eosinophilia was detected in house dust mite (HDM)-induced asthmatic Ifng^−/− mice in the absence of RSV infection. Furthermore, neither WT nor Ifng^−/− mice exhibit apparent eosinophil infiltration during RSV infection alone. Together, these findings indicate that, despite its critical role in limiting eosinophilic inflammation during asthma, IFN-γ is not essential for protection against RSV-induced exacerbation of asthmatic inflammation in adult mice.

Personal Network Inference Unveils Heterogeneous Immune Response Patterns to Viral Infection in Children with Acute Wheezing

Human rhinovirus (RV)-induced exacerbations of asthma and wheeze are a major cause of emergency room presentations and hospital admissions among children. Previous studies have shown that immune response patterns during these exacerbations are heterogeneous and are characterized by the presence or absence of robust interferon responses. Molecular phenotypes of asthma are usually identified by cluster analysis of gene expression levels. This approach however is limited, since genes do not exist in isolation, but rather work together in networks. Here, we employed personal network inference to characterize exacerbation response patterns and unveil molecular phenotypes based on variations in network structure. We found that personal gene network patterns were dominated by two major network structures, consisting of interferon-response versus FCER1G-associated networks. Cluster analysis of these structures divided children into subgroups, differing in the prevalence of atopy but not RV species. These network structures were also observed in an independent cohort of children with virus-induced asthma exacerbations sampled over a time course, where we showed that the FCER1G-associated networks were mainly observed at late time points (days four-six) during the acute illness. The ratio of interferon- and FCER1G-associated gene network responses was able to predict recurrence, with low interferon being associated with increased risk of readmission. These findings demonstrate the applicability of personal network inference for biomarker discovery and therapeutic target identification in the context of acute asthma which focuses on variations in network structure.