Objective We aimed to assess the profile of respiratory viruses in young children hospitalized for acute lower respiratory tract infection (ALRI) and its association with disease severity, defined as need for pediatric intensive care unit (PICU) admission. Design Prospective observational cohort study. Setting A tertiary-care university hospital in Brazil. Patients Children younger than three years attending the pediatric emergency room with ALRI who were admitted to the hospital. Interventions None. Measurements and main results Nasopharyngeal aspirates were collected from patients from June 1 st , 2008 to May 31 st , 2009within the first 48 hours of hospitalization. Nasopharyngeal aspirates were tested for 17humanrespiratory viruses by molecular and immunofluorescence based assays. Simple and multiple log-binomial regression models were constructed to assess associations of virus type with a need for PICU admission. Age, prematurity, the presence of an underlying disease and congenital heart disease were covariates. Nasopharyngeal aspirates were positive for at least one virus in 236 patients. Rhinoviruses were detected in 85.6% of samples, with a preponderance of rhinovirus C (RV-C) (61.9%). Respiratory syncytial virus was detected in 59.8% and human coronavirus (HCoV) in 11% of the samples. Co-detections of two to five viruses were found in 78% of the patients. The detection of HCoV alone (adjusted relative risk (RR) 2.18; 95% CI 1.15–4.15) or in co-infection with RV-C (adjusted RR 2.37; 95% CI 1.23–4.58) was independently associated with PICU admission. Conclusions The detection of HCoV alone or in co-infection with RV-C was independently associated with PICU admission in young children hospitalized for ALRI.

Influenza A virus (IAV) targets airway epithelial cells for infection. Large, heavily glycosylated molecules known as tethered mucins extend from the airway epithelial cell surface and may physically restrict pathogen access to underlying cells.

Near-infrared spectroscopy (NIRS) could be a useful continuous, non-invasive technique for monitoring the effect of partial pressure of carbon dioxide (PaCO 2 ) fluctuations in the cerebral circulation during ventilation. The aim of this study was to examine the efficacy of NIRS to detect acute changes in cerebral blood flow following PaCO 2 fluctuations after confirming the autoregulation physiology in piglets. Fourteen piglets (o72 h of life) were studied. Mean arterial blood pressure, oxygen saturation, pH, glycemia, hemoglobin, electrolytes, and temperature were monitored. Eight animals were used to evaluate brain autoregulation, assessing superior cava vein Doppler as a proxy of cerebral blood flow changing mean arterial blood pressure. Another 6 animals were used to assess hypercapnia generated by decreasing ventilatory settings and complementary CO 2 through the ventilator circuit and hypocapnia due to increasing ventilatory settings. Cerebral blood flow was determined by jugular vein blood flow by Doppler and continuously monitored with NIRS. A decrease in PaCO 2 was observed after hyperventilation (47.6±2.4 to 29.0±4.9 mmHg). An increase in PaCO 2 was observed after hypoventilation (48.5±5.5 to 90.4± 25.1 mmHg). A decrease in cerebral blood flow after hyperventilation (21.8 ± 10.4 to 15.1 ± 11.0 mL/min) and an increase after hypoventilation (23.4 ± 8.4 to 38.3 ± 10.5 mL/min) were detected by Doppler ultrasound. A significant correlation was found between cerebral oxygenation and Doppler-derived parameters of blood flow and PaCO 2 . Although cerebral NIRS monitoring is mainly used to detect changes in regional brain oxygenation, modifications in cerebral blood flow following experimental PaCO 2 changes were detected in newborn piglets when no other important variables were modified.

A B S T R A C TBackground: Mechanisms influencing severity of acute lower respiratory infection (ALRI) in children are not established. We aimed to assess the role of inflammatory markers and respiratory viruses in ALRI severity. Methods: Concentrations of interleukin(IL)-33, soluble suppression of tumorigenicity (sST)2, IL-1ß, tumor necrosis factor α, IL-4, IL-6 and IL-8 and types of respiratory viruses were evaluated in children at the first and fifth days after hospital admission. Disease severity was defined as need for mechanical ventilation. Results: Seventy-nine children < 5 years-old were included; 33(41.8%) received mechanical ventilation. No associations between virus type, viral load or co-detections and severity of disease were observed. Detection of IL-33 and sST2 in nasopharyngeal aspirates (NPA) on admission were associated with higher risk for mechanical ventilation (RR = 2.89 and RR = 4.57, respectively). IL-6 and IL-8 concentrations were higher on Day 5 in mechanically ventilated children. IL-6 NPA concentrations decreased from Day 1 to Day 5 in children who did not receive mechanical ventilation. Increase in sST2 NPA concentrations from Day 1 to Day 5 was associated with longer hospital length of stay (p < 0.01). Conclusions: An exacerbated local activation of the IL-33/ST2 axis and persistently high sST2 concentrations over time were associated with severity of viral ALRI in children.

A diverse collection of viral pathogens target airway epithelial cells for infection, with effects ranging from mild upper respiratory tract symptoms to death of the infected individual. Among these pathogens are recently discovered and/or emergent viruses that sometimes fail to infect commonly used, immortalized cell lines and for which infection phenotypes in the respiratory tract remain unknown. Human airway epithelial cultures have been developed over the past several decades and have proven to be a useful model system in culturing hard-to-grow viruses and assaying various features of infection in a physiologically relevant setting. This article includes methods for the generation of well-differentiated human airway epithelial cell cultures at air-liquid interface that recapitulate the mucosal epithelium of the trachea/bronchus in vivo. We further detail inoculation of these cultures with respiratory viruses-specifically rhinovirus, influenza virus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-and provide a protocol for the detection of double-stranded RNA or viral antigen-positive cells by immunofluorescence microscopy. These techniques, together with a post-imaging analysis, can be applied to characterize the efficiency of infection and kinetics of spread within the airway epithelium. Furthermore, these methods can be utilized in conjunction with antibodies against cellular targets to determine cell tropism and colocalization with specific host factors during infection.