Rhinovirus impairs the immune response of alveolar macrophages to facilitate Streptococcus pneumonia infection.

Pneumonia is one important cause of mortality in neonates. However, the mechanism remains still unclear. Viral infection greatly enhances the morbidity of Streptococcus pneumonia. In this study, we tried to understand how human rhinovirus (HRV) would accelerate Streptococcus pneumonia infection. Alveolar macrophages (AMs) were isolated from neonatal mice. Cytokine concentrations were detected using ELISA. The phagocytosis of Streptococcus pneumonia by AMs was indicated by immunofluorescence. Toll-like receptor 3 (TLR3) and CD68 expression in isolated AMs or infected mice were determined by western blot or immunochemistry. The mortality was explored using Kaplan-Meier analysis. HRV infection enhanced cytokine release by AMs, and decreased Streptococcus pneumonia-induced TNF-α, IL-1β and IL-6 release by AMs, while has no influence on IL-10 release. HRV infection impaired phagocytosis of Streptococcus pneumonia in AMs. Mechanically, HRV infection up-regulated TLR3 expression in AMs. Mortality and pneumococcal burden decreased in TLR3-/- neonatal mice and inflammation and phagocytosis were restored in TLR3-/- AMs. Neonatal rhinovirus impairs the immune response of alveolar macrophages to facilitate Streptococcus pneumonia infection via TLR3 signaling.
(© FEMS 2020.)