Inhibition of both A- and B-type hRSV by carnosic acid. Effects of carnosic acid on the synthesis of viral proteins from hRSV B/KR virus were analyzed by RT-qPCR. A549 cells were treated with carnosic acid 1 hour prior to infection. Twelve and twenty-four hours after virus infection, RNA levels of each viral protein were quantified by RT-qPCR using type-specific primers. NS2-specific primers (A) and G protein-specific primers (B) are used to assay antiviral activity against hRSV B/KR. All the experiments were performed in triplicate and data represent means ± SD. ** p < 0.01 versus Mock-treated (Mock). A.U.: Arbitrary unit.