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Whereas most infants infected with respiratory syncytial virus (RSV) show no or only mild symptoms, an estimated 3 million children under five are hospitalized annually due to RSV disease. This study aimed to investigate biological mechanisms and associated biomarkers underlying RSV disease heterogeneity in young infants, enabling the potential to objectively categorize RSV‐infected infants according to their medical needs. Immunophenotypic and functional profiling demonstrated the emergence of immature and progenitor‐like neutrophils, proliferative monocytes (HLA‐DRLow, Ki67+), impaired antigen‐presenting function, downregulation of T cell response and low abundance of HLA‐DRLow B cells in severe RSV disease. HLA‐DRLow monocytes were found as a hallmark of RSV‐infected infants requiring hospitalization. Complementary transcriptomics identified genes associated with disease severity and pointed to the emergency myelopoiesis response. These results shed new light on mechanisms underlying the pathogenesis and development of severe RSV disease and identified potential new candidate biomarkers for patient stratification. [ABSTRACT FROM AUTHOR]

Trans-epithelial migration and physical interaction are required for full activation of neutrophils during in vitro RSV infection. [ABSTRACT FROM AUTHOR]

Rationale: Respiratory syncytial virus (RSV) bronchiolitis is a major cause of morbidity and mortality in infancy. Severe disease is believed to result from uncontrolled viral replication, an excessive immune response, or both.Objectives: To determine RSV load and immune mediator levels in nasal mucosal lining fluid by serial sampling of nasal fluids from cases of moderate and severe bronchiolitis over the course of infection.Methods: Infants with viral bronchiolitis necessitating admission (n = 55) were recruited from a pediatric center during 2016 and 2017. Of these, 30 were RSV infected (18 "moderate" and 12 mechanically ventilated "severe"). Nasal fluids were sampled frequently over time using nasosorption devices and nasopharyngeal aspiration. Hierarchical clustering of time-weighted averages was performed to investigate cytokine and chemokine levels, and gene expression profiling was conducted.Measurements and Main Results: Unexpectedly, cases with severe RSV bronchiolitis had lower nasal viral loads and reduced IFN-γ and C-C chemokine ligand 5/RANTES (regulated upon activation, normal T cell expressed and secreted) levels than those with moderate disease, especially when allowance was made for disease duration (all P < 0.05). Reduced cytokine/chemokine levels in severe disease were also seen in children with other viral infections. Gene expression analysis of nasopharyngeal aspiration samples (n = 43) confirmed reduced type-I IFN gene expression in severe bronchiolitis accompanied by enhanced expression of MUC5AC and IL17A.Conclusions: Infants with severe RSV bronchiolitis have lower nasal viral load, CXCL10 (C-X-C motif chemokine ligand 10)/IP-10, and type-I IFN levels than moderately ill children, but enhanced MUC5AC (mucin-5AC) and IL17A gene expression in nasal cells. [ABSTRACT FROM AUTHOR]

The article offers information on the Infantile bronchiolitis is a major scourge of early childhood, and winter outbreaks that fill the pediatric wards with wearisome regularity. It mentions that most infants will be infected by respiratory syncytial virus (RSV) before their second birthday; and also mentions that animal models have advanced our understanding of the pathogenesis of bronchiolitis.

Background: Existing respiratory mucosal sampling methods are flawed, particularly in a pediatric bronchiolitis setting.Methods: Twenty-four infants with bronchiolitis were recruited: 12 were respiratory syncytial virus (RSV)-positive, 12 were RSV-negative. Infants were sampled by nasosorption and nasopharyngeal aspiration (NPA).Results: Nasosorption was well tolerated and identified all RSV+ samples. RSV load measured by nasosorption (but not NPA) correlated with length of hospital stay (P = .04) and requirement for mechanical ventilation (P = .03). Nasosorption (but not NPA) levels of interferon γ, interleukin 1β, CCL5/RANTES, and interleukin 10 (IL-10) were elevated in RSV+ bronchiolitis (all P < .05), furthermore CCL5 and IL-10 correlated with RSV load (P < .05).Conclusions: Nasosorption allowed measurement of RSV load and the mucosal inflammatory response in infants. [ABSTRACT FROM AUTHOR]

The article describes a hitherto unknown inhibitory effect of chemokine ligand 4 (CXCL4) on respiratory syncytial virus (RSV) infection, replication, and disease. Topics include CXCL4 inhibited replication of Enterovirus 71 (EV71) and Herpes simplex virus 1 (HSV1); and CXCL4 protects against RSV infection through inhibition of RSV attachment to heparan sulfate (HS) on the surface of target cells.

The article presents a research on Neutrophilic inflammation in the respiratory mucosa predisposes to respiratory syncytial virus (RSV) infection. Topics include Variable transmissions govern by the immune status of the host, such as the presence of specific protective antibodies or T cells; and antibodies and T cells have limited efficacy against pathogens with pandemic potential but the intrinsic and innate mechanisms underlying protection when people being exposed to these viruses.