Objective To study the mechanism of respiratory syncytial virus(RSV) induced the expression of indoleamine 2

3dioxygenase (IDO) in monocytes. Methods Monocytes were infected with RSV in vitro

or signal pathway inhibitor were preincubated with monocytes for 1 hour and then RSV were added

the level of IDO was detected by RTPCR and enzymelinked immunosorbent assay(ELISA). Results After RSV infection

the mRNA and protein levels of IDO by monocytes were significantly increased(P<0.05)

which was in a time dependent manner.In addition

RSVinduced the expression of IDO by monocytes was significantly decreased after pre-incubated by the TLR3 or NF-κB inhibitor (P<0.01)

but such effect was not observed when monocytes were pre-incubated with the TLR7/8/9 inhibitor

RIGI inhibitor

PI3K inhibitor

JNK inhibitor and MEK1/2 inhibitor. Conclusion RSV can induce the expression of IDO in monocytes via TLR3NFκB signal pathway

which may be involved in the development of RSVrelated diseases.