Respiratory syncytial virus (RSV) bronchiolitis causes substantial morbidity and mortality in young children, but insight into the burden of RSV bronchiolitis on pediatric intensive care units (PICUs) is limited. We aimed to determine the burden of RSV bronchiolitis on the PICUs in the Netherlands. Therefore, we identified all children ≤ 24 months of age with RSV bronchiolitis between 2003 and 2016 from a nationwide PICU registry. Subsequently we manually checked their patient records for correct diagnosis and collected patient characteristics, additional clinical data, respiratory support modes, and outcome. In total, 2161 children were admitted to the PICU for RSV bronchiolitis. The annual number of admissions increased significantly during the study period (β 4.05, SE 1.27, p = 0.01), and this increase was mostly driven by increased admissions in children up to 3 months old. Concomitantly, non-invasive respiratory support significantly increased (β 7.71, SE 0.92, p < 0.01), in particular the use of high flow nasal cannula (HFNC) (β 6.69, SE 0.96, p < 0.01), whereas the use of invasive ventilation remained stable.Conclusion: The burden of severe RSV bronchiolitis on PICUs has increased in the Netherlands. Concomitantly, the use of non-invasive respiratory support, especially HFNC, has increased. What is Known:• RSV bronchiolitis is a major cause of childhood morbidity and mortality and may require pediatric intensive care unit admission.• The field of pediatric critical care for severe bronchiolitis has changed due to increased non-invasive respiratory support options. What is New:• The burden of RSV bronchiolitis for the Dutch PICUs has increased. These data inform future strategic PICU resource planning and implementation of RSV preventive strategies.• There was a significant increase in the use of high flow nasal cannula at the PICU, but the use of invasive mechanical ventilation did not decrease.

Although a marked increase in the reporting of wheezing symptoms since the mid1970s has been described, the underlying immunopathology of the different wheezing phenotypes has not been clarified. Since differences in gene expression might be involved, the objective of the present study was to identify gene expression profiles in CD4+ T-cells from two distinct infant wheezing phenotypes.The gene expression profiles of peripheral CD4+ T-cells were compared by means of microarray analysis of six transient wheezers, six persistent wheezers and seven healthy controls. The differentially expressed genes were subsequently validated by RT-PCR.The differential gene expression profiles reflected common immunological pathways involved in apoptosis or proliferation of T-cells. Furthermore, both wheezing phenotypes showed decreased expression of the complement component 5 receptor 1 gene, a gene involved in the regulation of bronchial responsiveness. Moreover, differences in gene expression profiles were found in genes involved in the immune response against respiratory syncytial virus, such as those encoding signal transducer and activator of transcription 1 and an inflammatory mediator showing enhanced production in asthma (prostaglandin E 2 receptor 2).The present findings suggest that clinical symptoms of wheeze are reflected in common immunological pathways, whereas differences between wheezing phenotypes are, in part, reflected in distinct gene expression profiles.

BackgroundTo prevent harmful autoimmunity most immune responses to self proteins are controlled by central and peripheral tolerance. T cells specific for a limited set of self-proteins such as human heat shock protein 60 (HSP60) may contribute to peripheral tolerance. It is not known whether HSP60-specific T cells are present at birth and thus may play a role in neonatal tolerance. We studied whether self-HSP60 reactive T cells are present in cord blood, and if so, what phenotype these cells have.Methodology/Principal FindingsCord blood mononuclear cells (CBMC) of healthy, full term neonates (n = 21), were cultured with HSP60 and Tetanus Toxoid (TT) to study antigen specific proliferation, cytokine secretion and up-regulation of surface markers. The functional capacity of HSP60-induced T cells was determined with in vitro suppression assays. Stimulation of CBMC with HSP60 led to CD4+ T cell proliferation and the production of various cytokines, most notably IL-10, Interferon-gamma, and IL-6. HSP60-induced T cells expressed FOXP3 and suppressed effector T cell responses in vitro.ConclusionSelf-reactive HSP60 specific T cells are already present at birth. Upon stimulation with self-HSP60 these cells proliferate, produce cytokines and express FOXP3. These cells function as suppressor cells in vitro and thus they may be involved in the regulation of neonatal immune responses.

RationaleSevere acute asthma (SAA) can be fatal, but is often preventable. We previously observed in a retrospective cohort study, a three-fold increase in SAA paediatric intensive care (PICU) admissions between 2003 and 2013 in the Netherlands, with a significant increase during those years of numbers of children without treatment of inhaled corticosteroids (ICS).ObjectivesTo determine whether steroid-naïve children are at higher risk of PICU admission among those hospitalised for SAA. Furthermore, we included the secondary risk factors tobacco smoke exposure, allergic sensitisation, previous admissions and viral infections.MethodsA prospective, nationwide multicentre study of children with SAA (2–18 years) admitted to all Dutch PICUs and four general wards between 2016 and 2018. Potential risk factors for PICU admission were assessed using logistic regression analyses.Measurements and main results110 PICU and 111 general ward patients were included. The proportion of steroid-naïve children did not differ significantly between PICU and ward patients. PICU children were significantly older and more exposed to tobacco smoke, with symptoms >1 week prior to admission. Viral susceptibility was not a significant risk factor for PICU admission.ConclusionsChildren with SAA admitted to a PICU were comparable to those admitted to a general ward with respect to ICS treatment prior to admission. Preventable risk factors for PICU admission were >7 days of symptoms without adjustment of therapy and exposure to tobacco smoke. Physicians who treat children with asthma must be aware of these risk factors.