Isobavachalcone inhibits Pseudorabies virus by impairing virus-induced cell-to-cell fusion

Pseudorabies virus (PRV) is an important pathogen that threatens the global swine industry. Currently, there is no effective drug that can clinically prevent or treat PRV infections. Isobavachalcone (IBC), a natural chalcone compound derived from Psoralea corylifolia, displays multiple biological activities, such as antibacterial, antifungal, and anticancer activities. Recently, it was found that IBC exhibited antiviral activity against an RNA virus, porcine reproductive and respiratory syndrome virus (PRRSV), in vitro. In the current study, we further demonstrated for the first time that IBC has a strong inhibitory effect on PRV. Through a viral luciferase expression assay, we showed that the inhibition step occurs mainly in the late stage of viral replication. Finally, via a cell-to-cell fusion assay, we demonstrated that IBC inhibits PRV by blocking virus-mediated cell fusion. Thus, IBC may be a candidate for further therapeutic evaluation against PRV infection in vivo.