Inhibition of hRSV replication and infection by carnosic acid. (A) A549 cells were treated with carnosic acid at various times before and after virus inoculation. Inhibitory effects were analyzed by measuring the synthesis of RNA for viral F and NS2 proteins. (B) Cells were treated with carnosic acid for 1 hour. After washing five times with PBS to remove carnosic acid, cells were infected with hRSV A2 for 1 hour as follows: Car-, cells infected with hRSV without carnosic acid; Car+, cells infected with hRSV inoculum containing carnosic acid, then washed with PBS before further incubation; Car++, cells infected with hRSV inoculum containing carnosic acid and then further incubated in carnosic acid-containing media. Forty-eight hours after infection, viral protein synthesis was analyzed by RT-qPCR. All the experiments were performed in triplicate and data represent means ± SD. * p < 0.05 versus Mock-treated (Mock). ** p < 0.01 versus Mock-treated (Mock). A.U.: Arbitrary unit.