ABSTRACT
BACKGROUND: African swine fever virus (ASFV) is a major threat to pig production and the lack of effective vaccines underscores the need to develop robust antiviral countermeasures. Pathologically, a significant elevation in pro-inflammatory cytokine production is associated with ASFV infection in pigs and there is high interest in identifying dual-acting natural compounds that exhibit antiviral and anti-inflammatory activities. METHODS: Using the laboratory-adapted ASFV BA71V strain, we screened a library of 297 natural, anti-inflammatory compounds to identify promising candidates that protected Vero cells against virus-induced cytopathic effect (CPE). Virus yield reduction, virucidal, and cell cytotoxicity experiments were performed on positive hits and two lead compounds were further characterized in dose-dependent assays along with time-of-addition, time-of-removal, virus entry, and viral protein synthesis assays. The antiviral effects of the two lead compounds on mitigating virulent ASFV infection in porcine macrophages (PAMs) were also tested using similar methods, and the ability to inhibit pro-inflammatory cytokine production during virulent ASFV infection was assessed by enzyme-linked immunosorbent assay (ELISA). RESULTS: The screen identified five compounds that inhibited ASFV-induced CPE by greater than 50% and virus yield reduction experiments showed that two of these compounds, tetrandrine and berbamine, exhibited particularly high levels of anti-ASFV activity. Mechanistic analysis confirmed that both compounds potently inhibited early stages of ASFV infection and that the compounds also inhibited infection of PAMs by the virulent ASFV Arm/07 isolate. Importantly, during ASFV infection in PAM cells, both compounds markedly reduced the production of pro-inflammatory cytokines involved in disease pathogenesis while tetrandrine had a greater and more sustained anti-inflammatory effect than berbamine. CONCLUSIONS: Together, these findings support that dual-acting natural compounds with antiviral and anti-inflammatory properties hold promise as preventative and therapeutic agents to combat ASFV infection by simultaneously inhibiting viral replication and reducing virus-induced cytokine production.