Protoporphyrin IX targets viral spike glycoproteins to inactivate Akabane virus

Akabane virus (AKAV), an emerging arthropod-borne <i>Orthobunyavirus</i>, is a significant pathogen of ruminants which causes severe congenital abnormalities and recurrent outbreaks in China and other Asian countries. However, no effective therapeutic options are available. In this study, structure-based virtual screening was performed using an FDA-approved compound library to identify potential compounds targeting the AKAV Gc protein. Ten candidate compounds were identified based on their high-affinity binding to the Gc protein. Among these ten candidates, Protoporphyrin IX (PPIX) demonstrated the most potent inhibitory effect on AKAV replication <i>in vitro</i>. Subsequent dose-response assays confirmed the antiviral efficacy of PPIX. Additionally, PPIX demonstrated antiviral activity at the pre-entry stage of infection. Notably, co-incubation of PPIX with AKAV virions resulted in rapid inactivation of the virus. Further experiments revealed that PPIX inactivates AKAV through direct binding to the Gc glycoprotein, leading to the disruption of its spike structure. <i>In vivo</i> experiments showed that pre-incubation of PPIX with AKAV can effectively inhibit the infectivity and pathogenicity of AKAV in sucking mice. Our findings demonstrate that PPIX exerts potent virucidal activity against AKAV both in vitro and in vivo, underscoring its potential potential use in preventing AKAV infection.