Objective: To study the lung tissue TLR4 expression and airway hyperresponsiveness(AHR) in the mice infected by respiratory syncytial virus(RSV).Methods:16 clean

6 weeks old BALB/c mice were divided into two groups equally(RSV group and control).One week after RSV infection

AHR was detected by inhaling the increased concentration of methacholine

TLR4 mRNA expression was measured by RT-PCR methods

and the correlation between AHR and TLR4 expression was also analyzed.Results:An important difference was detected in two groups’ airway resistance when the inhaled concentration of methacholine was 3.2g/L(P<0.01).The TLR4/β-actin was 0.361±0.102 and 0.239±0.055 respectively in RSV group and control group and there was a statistically significance(P<0.05).The expression of TLR4 mRNA was positively correlated with the airway hyperresponsiveness when the inhaled methacholine concentration reached 3.2g/L(r=0.721

P<0.05).Conclusion:The lung tissue expression of TLR4 mRNA and AHR were increased in the mice infected by RSV and they were positively correlated.