In vitro activity of Paris polyphylla smith against enterovirus 71 and coxsackievirus B3 and its immune modulation.

Enterovirus 71 (EV71) and coxsackievirus B3 (CVB3) have resulted in severe pathogenesis caused by the host's immune response, including the cytokine cascade. Paris polyphylla Smith is a folk medicinal plant in Asia traditionally prescribed for the reduction of pain and elimination of poisoning. In this study, we investigated the anti-EV71 and CVB3 activity of P. polyphylla Smith as well as its immune modulation. The IC(50) for the P. polyphylla Smith 95% ethanol extract against EV71 and CVB3 were 12.5-23% and 99-156% of that of ribavirin, a positive control. Prevention of viral infection, viral inactivation, and anti-viral replication effects against both EV71 and CVB3 were demonstrated by the extract, the anti-viral replication effect being dominant. The extract significantly increased IL-6 production in both EV71- and CVB3-infected cells. A high correlation was possibly demonstrated between the high amounts of IL-6 induction in the EV71 and CVB3-infected cells and the anti-viral replication activity of the extract. In conclusion, good anti-EV71 and CVB3 activity was observed in the P. polyphylla Smith 95% ethanol extract. The high amounts of IL-6 induction in the virus-infected cells played a key role in the anti-viral activity of the extract.