Artemisia argyi Levl.et Vant Extract (AALE) and Parthenolide Suppress Respiratory Syncytial Virus (RSV) via the RIG-I/TLR3 Pathway In Vivo and In Vitro.

Background: Respiratory syncytial virus (RSV) is a leading global pathogen of acute lower respiratory tract infection, posing significant risks to infants, the elderly, and immunocompromised patients. Artemisia argyi Levl.et Vant Extract (AALE) and its active components have a variety of pharmacological effects, but their anti-RSV potential remains unclear. The aim of this study is to investigate the anti-RSV activity of AALE and parthenolide and its underlying mechanisms. Methods: Cell counting kit-8 (CCK-8) assay was used to determine the anti-RSV activities of AALE and parthenolide. Time-of-addition assay and phase of action analysis were used to explore the effect of drugs on the viral replication cycle. Quantitative polymerase chain reaction (qRCR), immunofluorescence (IF) and Western blot (WB) were used to investigate the effects of AALE and parthenolide on RSV-F gene and protein and on RIG-I/TLR-3 pathway related molecules in vitro. In vivo antiviral efficacy was verified by hematoxylin-eosin (HE) staining for lung histopathology, quantitative real-time PCR (qPCR) quantification of RSV-F, RIG-I, TLR-3, IRF3, IL-6, and IFN-β gene expression in lung tissues, and enzyme-linked immunosorbent assay (ELISA) for serum IL-6 and IFN-β levels. Results: AALE exhibited the strongest anti-RSV activity among the extracts (SI = 27.6), while parthenolide was the most potent monomeric compound (SI = 8.19). In vitro, both AALE and parthenolide were effective in the co-treatment and post-treatment models, reducing RSV-F gene and F protein levels in infected cells. Furthermore, they alleviated RSV infection by regulating RIG-I and TLR-3 pathway-related genes and proteins. In vivo, AALE and parthenolide suppressed lung index and RSV proliferation, attenuated lung injury, and down-regulated RIG-I, TLR-3, IRF3, IL-6, and IFN-β expression in the lungs of RSV-infected mice. Conclusions: AALE and its component parthenolide can inhibit the invasion and replication of RSV, making it a potential candidate for the treatment of RSV-related diseases.