Effect of HMGB1 on monocyte immune function in respiratory syncytial virus bronchiolitis

Expression of high mobility group protein box 1 (HMGB1) in children with respiratory syncytial virus bronchiolitis and its effect on the inflammatory function of monocytes were investigated. A total of 30 cases of respiratory syncytial viral bronchitis and 30 cases of healthy persons from physical examination were collected from January 2017 to September 2019 in the pediatric department of Xuzhou Children's Hospital, Xuzhou Medical University. HMGB1 expression level in plasma was detected by ELISA. All participants in the study were followed up for 18 months. Human recombinant respiratory syncytial virus (RSV)-A2 virus was used to infect human bronchial epithelial cell line 16HBE, and cell culture supernatant was collected to detect HMGB1. Transwell plate was used to co-culture infected or no-infection groups of epithelial cells and monocytes THP-1. Western blot was used to detect the level of Toll-like receptor (TLR)4 and TLR7 in monocytes. HMGB1 expression level in peripheral blood of children with bronchiolitis was significantly increased compared with that in healthy controls (P<0.0001), and was significantly correlated with the severity of the children's condition (P<0.01). The expression level of HMGB1 was significantly correlated with the number of monocytes, lymphocytes and CRP expression level. HMGB1 was also significantly increased in cell culture supernatant compared with no-infection group (P<0.0001). TLR4 expression in monocytes could be activated by the virus infected cell lines. Follow-up results showed that children with bronchiolitis had a higher incidence of asthma within 18 months (P<0.05). The independent risk factors for children to develop asthma were age, number of monocytes and HMGB1 level. HMGB1 is highly expressed in peripheral blood of children with respiratory syncytial virus bronchitis, and RSV epithelial cells can activate TLR4 expression in monocytes, suggesting that HMGB1 plays an important role in monocyte mediated immune inflammation. HMGB1 expression level is related to the development of asthma in children, which is of great significance for understanding the pathogenesis of bronchiolitis and suggesting the prognosis of children.