[Inhibition of the pseudorabies virus (Suis herpesvirus 1) by an antiviral agent isolated from the leaves of Melia azedarach].

A partially purified extract from fresh green leaves of Melia azedarach L prevents the replication of Pseudorabies virus (Suid herpesvirus, (PrV)) in Vero cells. Monolayers of VEro cells were fully protected against PrV CPE when an appropriate concentration of the antiviral compound was added to the culture medium after virus adsorption and remained during 72 h. By contrast, if cells were pretreated with the same amount of antiviral during 18 h before infection, CPE produced by PrV was only slightly reduced. The antiviral activity of the compound specifically affect PrV multiplication since it was found that no toxic effects on cells were observed at the concentrations assayed which inhibited virus yield by 99%. The effect or the antiviral on adsorption or penetration steps was investigated. Neither the number or viral particles that penetrate nor the amount of unadsorbed virus were the same in treated and non-treated cultures. In order to determine whether an early of late step of intracellular virus replication was inhibited, the extract was added at different times post-infection and the virus yield was determined. The production of infectious virus decreased almost 3 log when the compound was added up to 4 h. p.i. According to these results we postulate that an early stage of virus replication, probably beta-messenger expression is inhibited.