Isolation of Rhizoma Paridis saponins as novel entry inhibitors of Crimean-Congo hemorrhagic fever virus.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a highly pathogenic bunyavirus, causing Crimean-Congo hemorrhagic fever (CCHF) in humans with high morbidity and mortality. Currently, there are no licensed antiviral drugs or vaccines against CCHFV, emphasizing the critical need to develop novel antiviral agents. The entry process is the initial step during the viral life cycle, and has provided an attractive target for novel antiviral development. In the present study, we developed a high-throughput screening approach based on the CCHFV glycoprotein (Gn/Gc)-based HIV-1 pseudoviruses, in order to discover novel CCHFV entry inhibitors. As a pilot, a library consisting of 500 pre-purified fractions of traditional Chinese medicine was screened, and it was identified that multi-fractions of Rhizoma Paridis exhibited inhibitory effects against CCHFV entry. Next, bioactivity-guided isolation was performed and a range of Rhizoma Paridis saponins were characterized as potential anti-CCHFV actives. Moreover, the antiviral activities of both Rhizoma Paridis extracts and the saponin derivatives were validated by a cell-based assay using authentic viruses. Mechanistic studies further demonstrated that Rhizoma Paridis saponins act by targeting host factors. In summary, this study provides a promising new strategy for CCHF treatment that deserves further development in the future.