Abstract: Objective To study the relationship between the expression of microrNA-93-5P and T-helper 1 (Th1)/T-helper 2 (Th2) balance in peripheral blood of children with respiratory syncytial virus (RSV) lower respiratory tract infection.  
Methods A total of 58 children with RSV lower respiratory tract infection who were registered and treated in the Department of Pediatrics of our hospital were selected as the RSV group, and 60 age- and gender-matched healthy children were selected as the control group. The serum miR-93-5p level was detected by real-time quantitative polymerase chain reaction (RT-qPCR). The percentage of Th1 and Th2 were counted by flow cytometry, and the expression of Th1/Th2 was calculated. The levels of interleukin (IL)-2, IL-4, IL-10 and interferon-γ (IFN-γ) were detected by enzyme linked immunosorbent assay (ELISA), and the relationship between miR-93-5p and Th1/Th2 was analyzed by Spearman. Logistics regression analysis was performed to analyze the risk factors of RSV lower respiratory tract infection. 
Results The level of miR-93-5p in RSV group was higher than that in control group (P＜0.05). Th1 and Th1/Th2 in RSV group were lower than those in control group (P＜0.05), while Th2 in RSV group was higher than that in control group; the levels of IL-2 and IFN-γ were lower in RSV group than in the control group (P＜0.05). The levels of IL-4 and IL-10 in RSV group were higher than those in control group (P＜0.05). miR-93-5p inRSV group was negatively correlated with IL-2, IFN-γ and Th1/Th2 ratio (P＜0.05), and positively correlated with IL-4 and IL-10 (P＜0.05). Logistic regression analysis showed that high level of miR-93-5p and low level of Th1/Th2 were risk factors for RSV lower respiratory tract infection (P＜0.05). 
Conclusion Mir-93-5P is highly expressed in peripheral blood of children with RSV lower respiratory tract infection, and its high expression may be closely related to Th1/Th2 balance. 

Key words: respiratory syncytial viruses, respiratory tract infections, MiR-93-5 p, Th1/Th2 balance