Effect of cantharidin, cephalotaxine and homoharringtonine on "in vitro" models of hepatitis B virus (HBV) and bovine viral diarrhoea virus (BVDV) replication.

The effect as antiviral agents versus viral hepatitis B and C of three compounds purified from natural products commonly used as remedies in traditional Chinese medicine, cantharidin, cephalotaxine and homoharingtonine, was investigated. To assess the activity of these compounds against flavivirus, we used bovine viral diarrhoea virus (BVDV) as a surrogate for hepatitis C virus (HCV). Anti-BVDV activity was determined by reduction in BVDV-RNA production and protection of infected embryonic bovine trachea (EBTr) cells against the cytopathic effect of BVDV. The effect versus hepatitis B virus (HBV) was investigated by measuring HBsAg and HBV-DNA release from hepatoblastoma HepG2 2.2.15 cells infected with HBV. As positive control we used the standard anti-HBV and anti-HCV drugs, lamivudine and ribavirin, respectively. Up to 100 microM lamivudine and ribavirin did not induce cell toxicity, whereas they induced dose-dependent anti-HBV and anti-BVDV effects, respectively. In the same range, cantharidin, cephalotaxine and homoharringtonine induced toxicity in EBTr cells and had no protective effect against BVDV. In contrast, they were able to inhibit HBV production at concentrations 10- to 100-fold lower than those inducing cell toxicity, which suggests that they are useless for the treatment of infection by flaviviruses, but potentially useful in combined therapy against hepatitis B.

Antiviral effect of artemisinin from Artemisia annua against a model member of the Flaviviridae family, the bovine viral diarrhoea virus (BVDV).

The antiviral activity versus flaviviruses of artemisinin, a safe drug obtained from Artemisia annua and commonly used to treat malaria, has been investigated using as an IN VITRO model bovine epithelial cells from embryonic trachea (EBTr) infected with the cytopathic strain Oregon C24V, of bovine viral diarrhoea virus (BVDV), which is a member of the Flaviviridae family. Antiviral activity was estimated by the degree of protection against the cytopathic effect of BVDV on host cells and by the reduction in BVDV-RNA release to the culture medium. To induce an intermediate cytopathic effect in non-treated cells, EBTr cells were first exposed to BVDV for 48 h and then incubated with virus-free medium for 72 h. Ribavirin and artemisinin (up to 100 microM) induced no toxicity in host cells, whereas a slight degree of toxicity was observed for IFN-alpha at concentrations above 10 U/mL up to 100 U/mL. Treatment of infected cells with IFN-alpha, ribavirin and artemisinin markedly reduced BVDV-induced cell death. A combination of these drugs resulted in an additive protective effect. These drugs induced a significant reduction in the production/release of BVDV virions by infected EBTr cells; there was also an additive effect when combinations of them were assayed. These results suggest a potential usefulness of artemisinin in combination with current pharmacological therapy for the treatment of human and veterinary infections by flaviviruses.