Licochalcone A regulates viral IRES activity to inhibit enterovirus replication

Enterovirus D68 (EV-D68), belonging to the genus Enterovirus of the Picornavirus family, is an emerging pathogen that can cause neurological and respiratory diseases in children. However, there is little understanding of the pathogenesis of EV-D68, and no effective vaccine or drug for the prevention or treatment of the diseases caused by this virus is available. Autophagy is a cellular process that targets cytoplasmic proteins or organelles to the lysosomes for degradation. Enteroviruses strategically harness the host autophagy pathway to facilitate the completion of their life cycle. Therefore, we selected an autophagy compound library to screen for autophagy-related compounds that may affect viral growth. By using the neutralization screening assay, we identified a compound, 'licochalcone A' that significantly inhibited EV-D68 replication. To investigate the mechanism by which licochalcone A inhibits EV-D68 replication and to identify the viral life cycle stage it inhibits, the time-of-addition, viral attachment, viral entry, and dual-luciferase reporter assays were performed. The results of the time-of-addition assay showed that licochalcone A, a characteristic chalcone found in liquorice roots and widely used in traditional Chinese medicine, inhibits EV-D68 replication during the early stages of the viral life cycle, while those of the dual-luciferase reporter assay showed that licochalcone A does not regulate viral attachment and entry, but inhibits EV-D68 IRES-dependent translation. Licochalcone A also inhibited enterovirus A71 and coxsackievirus B3 but did not significantly inhibit dengue virus 2 or human coronavirus 229E replication. Licochalcone A regulates IRES translation to inhibit EV-D68 viral replication.