A high-content screening platform for antiviral drug discovery using a recombinant African swine fever virus

Abstract African swine fever (ASF), caused by African swine fever virus (ASFV), is a devastating disease of domestic pigs with mortality rates approaching 100%, leading to severe global economic losses. No effective vaccines or antivirals are available, highlighting the urgent need for novel therapeutic strategies and efficient screening tools. We developed a recombinant ASFV-expressing dual reporter ( mCherry and NanoLuc ), rASFV_mChNluc, and established a high-content screening (HCS) platform optimized for cost-effective, low-labor analysis via the mCherry reporter. The assay demonstrated excellent robustness (Z′-factor = 0.669±0.064) and successfully verified the activity of the known ASFV inhibitor AraC, confirming inhibition at the postinfection stage. Screening of an in-house fungal extract library (493 extracts) identified 25 hits (5.07%) that reduced viral infectivity to < 5%. Extracts from the insect fungi Beauveria neobassiana and Samsoniella aurantia showed potent activity, with an SI > 62.81 (EC₅₀ = 1.99±0.71 µg/mL) and an SI > 42.92 (EC₅₀ = 11.65±2.99 µg/mL), respectively. Time-of-addition assays indicated that B. neobassiana acts at multiple replication stages, whereas S. aurantia targets the postinfection stage. This study establishes a robust ASFV HCS platform for efficient high-throughput antiviral discovery and highlights fungi as a promising source of novel ASFV inhibitors.