Naturally occurring plant flavonoids are a promising class of antiviral agents to inhibit African swine fever virus (ASFV), which causes highly fatal disease in pigs and is a major threat to the swine industry. Currently known flavonoids with anti-ASFV activity demonstrate a wide range of antiviral mechanisms, which motivates exploration of new antiviral candidates within this class. The objective of this study was to determine whether other flavonoids may significantly inhibit ASFV infection in vitro. We performed a cell-based library screen of 90 flavonoids. Our screening method allowed us to track the development of virus-induced cytopathic effect by MTT in the presence of tested flavonoids. This screening method was shown to be robust for hit identification, with an average Z-factor of 0.683. We identified nine compounds that inhibit ASFV Ba71V strain in Vero cells. Among them, kaempferol was the most potent and exhibited dose-dependent inhibition, which occurred through a virostatic effect. Time-of-addition studies revealed that kaempferol acts on the entry and post-entry stages of the ASFV replication cycle and impairs viral protein and DNA synthesis. It was further identified that kaempferol induces autophagy in ASFV-infected Vero cells, which is related to its antiviral activity and could be partially abrogated by the addition of an autophagy inhibitor. Kaempferol also exhibited dose-dependent inhibition of a highly virulent ASFV Arm/07 isolate in porcine macrophages. Together, these findings support that kaempferol is a promising anti-ASFV agent and has a distinct antiviral mechanism compared to other anti-ASFV flavonoids.

African swine fever virus (ASFV) is the causal agent of a highly fatal disease of domestic swine for which no effective vaccines and antiviral drugs are available. Recently, it has been shown that microtubule-targeting agents hamper the infection cycle of different viruses, raising the idea that microtubules can be potential host targets for antiviral drug development. In this study, we conducted in silico screening against the colchicine binding site (CBS) of tubulin and found three new compounds with anti-ASFV activity. The most promising antiviral compound (6b) reduced ASFV replication in a dose-dependent manner (IC 50 =19.5 µM) with no cellular (CC 50 > 500 µM) and animal (white mice) toxicity (up to 100 mg/kg). Results also revealed that compound 6b interfered with ASFV attachment, internalization and egress, with time-of-addition assays, showing that compound 6b has higher antiviral effects when added within 2 to 8 hours postinfection. This compound significantly inhibited viral DNA replication and disrupted viral protein synthesis. Experiments with ASFV-infected porcine macrophages disclosed that antiviral effects of the compound 6b were similar to its effects in Vero cells. Tubulin polymerization assay and confocal microscopy demonstrated that compound 6b promoted tubulin polymerization, acting as a microtubule-stabilizing, rather than a destabilizing agent in cells. The docking and molecular dynamic simulations demonstrated that compound 6b could interact with the taxane binding site. In conclusion, this work emphasizes the idea that microtubules have an essential role during the ASFV replication cycle and can be targets for drug development.

Our interest in this article is to investigate different approaches to enantiosemy in English. In the coverage of a variety of viewpoints introduced in the present article, reference is made to well-established traditional and most recent perspectives and approaches provided by both European and Russian scholars with the view of elucidating different principles of classification. The data for the analysis are extracted from different dictionaries and British National Corpus in order to find distinct motivated meanings between opposite senses in the semantic structure of enantiosemic words. The analysis of the data enables us to reveal some regularities of antonymic relations which make it possible to regard them as special cases of polysemy in English. For this reason we consider it crucial to disclose integral and differentiating semes, as well as different potential semes, which give rise to different associations.