A screening study identified decitabine as an inhibitor of Equid Herpesvirus 4 that enhances the innate antiviral response

Equid herpesvirus 4 (EHV-4) is a frequent respiratory pathogen of the horse. EHV-4 sporadically induces abortion or neonatal death and although not clearly demonstrated its involvement in neurological forms is strongly suspected. Despite preventive treatments using vaccines against EHV-1/EHV-4, the resurgence of α-EHV infection still constitutes an important threat to the horse industry. Yet very few studies have been conducted on the search for antiviral molecules against EHV-4. A screening of 42 antiviral compounds was performed in vitro on E. Derm cells infected with EHV-4 405/76 reference strain (VR2230). Formation of cytopathic effects was monitored by Real-Time Cell Analysis (RTCA) and the viral load was quantified by qPCR. Aciclovir, the most widely used antiviral in vivo against alpha-herpesviruses, does not appear to be effective against EHV-4 in vitro. Potential antiviral activities were confirmed for 8 molecules (idoxuridine, vidarabine, pritelivir, cidofovir, valganciclovir, ganciclovir, aphidicolin, and decitabine). Decitabine is the most potent compound against EHV-4 in vitro. A transcriptomic analysis revealed an increase of expression of different genes implicated in IFN response. Decitabine (DTB) seems to activate the immune antiviral pathway. Comparison of gene expression in dermal horse cells after 18 hours for cells infected or not with EHV-4 virus and/or treated with decitabine