A new microtubule-stabilizing agent shows potent antiviral effects against African swine fever virus with no cytotoxicity

Structure-based discovery and rational design of microtubule-targeting agents

Microtubule-targeting agents (MTAs) have demonstrated remarkable efficacy as antitumor, antifungal, antiparasitic, and herbicidal agents, finding applications in the clinical, veterinary, and agrochemical industry. Recent advances in tubulin and microtubule structural biology have provided powerful tools that pave the way for the rational design of innovative small-molecule MTAs for future basic and applied life science applications. In this mini-review, we present the current status of the tubulin and microtubule structural biology field, the recent impact it had on the discovery and rational design of MTAs, and exciting avenues for future MTA research.

Identification of several African swine fever virus replication inhibitors by screening of a library of FDA-approved drugs

African swine fever (ASF) caused by African swine fever virus (ASFV) is a highly infectious and lethal swine disease. Currently, there is only one novel approved vaccine and no antiviral drugs for ASFV. In the study, a high-throughput screening of an FDA-approved drug library was performed to identify several drugs against ASFV infection in primary porcine alveolar macrophages. Triapine and cytarabine hydrochloride were identified as ASFV infection inhibitors in a dose-dependent manner. The two drugs executed their antiviral activity during the replication stage of ASFV. Furthermore, molecular docking studies showed that triapine might interact with the active center Fe2+ in the small subunit of ASFV ribonucleotide reductase while cytarabine hydrochloride metabolite might interact with three residues (Arg589, Lys593, and Lys631) of ASFV DNA polymerase to block new DNA chain extension. Taken together, our results suggest that triapine and cytarabine hydrochloride displayed significant antiviral activity against ASFV in vitro.

Brequinar inhibits African swine fever virus replication in vitro by activating ferroptosis

BACKGROUND

African swine fever virus (ASFV) is one of the most fatal swine etiological agents and has a huge economic impact on the global pork industry. Given that no effective vaccines or anti-ASFV drugs are available, there remains a pressing need for novel anti-ASFV drugs. This study aimed to investigate the anti-African swine fever virus (ASFV) activity of brequinar, a DHODH inhibitor.

METHODS

The anti-ASFV activity of brequinar was investigated using IFA, HAD, HAD50, qRT-PCR, and western blotting assays. The western blotting assay was used to investigate whether brequinar inhibits ASFV replication by killing ASFV particles directly or by acting on cell factors. The confocal microscopy and western blotting assays were used to investigate whether brequinar inhibits ASFV replication by activating ferroptosis.

RESULTS

In this study, brequinar was found to effectively inhibit ASFV replication ex vivo in porcine alveolar macrophages (PAMs) in a dose-dependent manner. In kinetic studies, brequinar was found to maintain ASFV inhibition from 24 to 72 hpi. Mechanistically, the time-of-addition assay showed that brequinar exerted anti-ASFV activity in all treatment modes, including pre-, co-, and post-treatment rather than directly killing ASFV particles. Notably, FerroOrange, Mito-FerroGreen, and Liperfluo staining experiments showed that brequinar increased the accumulation of intracellular iron, mitochondrial iron, and lipid peroxides, respectively. Furthermore, we also found that ferroptosis agonist cisplatin treatment inhibited ASFV replication in a dose-dependent manner and the inhibitory effect of brequinar on ASFV was partially reversed by the ferroptosis inhibitor ferrostatin-1, suggesting that brequinar activates ferroptosis to inhibit ASFV replication. Interestingly, exogenous uridine supplementation attenuated the anti-ASFV activity of brequinar, indicating that brequinar inhibits ASFV replication by inhibiting DHODH activity and the depletion of intracellular pyrimidine pools; however, the induction of ferroptosis by brequinar treatment was not reversed by exogenous uridine supplementation, suggesting that brequinar activation of ferroptosis is not related to the metabolic function of pyrimidines.

CONCLUSIONS

Our data confirm that brequinar displays potent antiviral activity against ASFV in vitro and reveal the mechanism by which brequinar inhibits ASFV replication by activating ferroptosis, independent of inhibiting pyrimidine synthesis, providing novel targets for the development of anti-ASFV drugs.

Bridging the Gap: Can COVID-19 Research Help Combat African Swine Fever?

African swine fever (ASF) is a highly contagious and economically devastating disease affecting domestic pigs and wild boar, caused by African swine fever virus (ASFV). Despite being harmless to humans, ASF poses significant challenges to the swine industry, due to sudden losses and trade restrictions. The ongoing COVID-19 pandemic has spurred an unparalleled global research effort, yielding remarkable advancements across scientific disciplines. In this review, we explore the potential technological spillover from COVID-19 research into ASF. Specifically, we assess the applicability of the diagnostic tools, vaccine development strategies, and biosecurity measures developed for COVID-19 for combating ASF. Additionally, we discuss the lessons learned from the pandemic in terms of surveillance systems and their implications for managing ASF. By bridging the gap between COVID-19 and ASF research, we highlight the potential for interdisciplinary collaboration and technological spillovers in the battle against ASF.

Theaflavin inhibits African swine fever virus replication by disrupting lipid metabolism through activation of the AMPK signaling pathway in virto

African swine fever virus (ASFV) is the etiological agent of African swine fever (ASF), which is one of the most harmful swine diseases in the pig industry because of its nearly 100% mortality rate in domestic pigs and results in incalculable economic loss. Ever since ASF was initially reported, scientists have worked to develop anti-ASF vaccines; however, currently no clinically effective vaccine for ASF is available. Therefore, the development of novel measures to prevent ASFV infection and transmission is essential. In this study, we aimed to investigate the anti-ASF activity of theaflavin (TF), a natural compound mainly isolated from black tea. We found that TF potently inhibited ASFV replication at non-cytotoxic concentrations ex vivo in primary porcine alveolar macrophages (PAMs). Mechanistically, we found that TF inhibited ASFV replication by acting on cells rather than interacting directly with ASFV to inhibit viral replication. Further, we found that TF upregulated the AMPK (5'-AMP-activated protein kinase) signaling pathway in ASFV-infected and uninfected cells, and treatment with the AMPK agonist MK8722 upregulated the AMPK signaling pathway and inhibited ASFV proliferation in a dose-dependent manner. Notably, the effects of TF on AMPK activation and ASFV inhibition were partially reversed by the AMPK inhibitor dorsomorphin. In addition, we found that TF down-regulated the expression of genes related to lipid synthesis and decreased the intracellular accumulation of total cholesterol and total triglycerides in ASFV-infected cells, suggesting that TF may inhibit ASFV replication by disrupting lipid metabolism. In summary, our results demonstrated that TF is an ASFV infection inhibitor and revealed the mechanism by which ASFV replication is inhibited, providing a novel mechanism and potential lead compound for the development of anti-ASFV drugs.

Dihydromyricetin inhibits African swine fever virus replication by downregulating toll-like receptor 4-dependent pyroptosis in vitro

African swine fever (ASF), caused by ASF virus (ASFV) infection, poses a huge threat to the pork industry owing to ineffective preventive and control measures. Hence, there is an urgent need to develop strategies, including antiviral drugs targeting ASFV, for preventing ASFV spread. This study aimed to identify novel compounds with anti-ASFV activity. To this end, we screened a small chemical library of 102 compounds, among which the natural flavonoid dihydromyricetin (DHM) exhibited the most potent anti-ASFV activity. DHM treatment inhibited ASFV replication in a dose- and time-dependent manner. Furthermore, it inhibited porcine reproductive and respiratory syndrome virus and swine influenza virus replication, which suggested that DHM exerts broad-spectrum antiviral effects. Mechanistically, DHM treatment inhibited ASFV replication in various ways in the time-to-addition assay, including pre-, co-, and post-treatment. Moreover, DHM treatment reduced the levels of ASFV-induced inflammatory mediators by regulating the TLR4/MyD88/MAPK/NF-κB signaling pathway. Meanwhile, DHM treatment reduced the ASFV-induced accumulation of reactive oxygen species, further minimizing pyroptosis by inhibiting the ASFV-induced NLRP3 inflammasome activation. Interestingly, the effects of DHM on ASFV were partly reversed by treatment with polyphyllin VI (a pyroptosis agonist) and RS 09 TFA (a TLR4 agonist), suggesting that DHM inhibits pyroptosis by regulating TLR4 signaling. Furthermore, targeting TLR4 with resatorvid (a specific inhibitor of TLR4) and small interfering RNA against TLR4 impaired ASFV replication. Taken together, these results reveal the anti-ASFV activity of DHM and the underlying mechanism of action, providing a potential compound for developing antiviral drugs targeting ASFV.

Identification of Potential miRNA-mRNA Regulatory Network Associated with Regulating Immunity and Metabolism in Pigs Induced by ASFV Infection

African swine fever (ASF) is a devastating infectious disease in domestic pigs caused by African swine fever virus (ASFV) with a mortality rate of about 100%. However, the understanding of the interaction between ASFV and host is still not clear. In this study, the expression differences and functional analysis of microRNA (miRNA) in porcine peripheral blood lymphocytes of ASFV infected pigs and healthy pigs were compared based on Illumina high-throughput sequencing, then the GO and KEGG signal pathways were analyzed. The miRNA related to immunity and inflammation were screened, and the regulatory network of miRNA-mRNA was drawn. A total of 70 differentially expressed miRNAs were found (p ≤ 0.05). Of these, 45 were upregulated and 25 were downregulated in ASFV-infected pigs vs. healthy pigs. A total of 8179 mRNA genes targeted by these 70 differentially expressed miRNA were predicted, of which 1447 mRNA genes were targeted by ssc-miR-2320-5p. Five differentially expressed miRNA were validated by RT-qPCR, which were consistent with the RNA-Seq results. The GO analysis revealed that a total of 30 gene functions were significantly enriched, including 7 molecular functions (MF), 13 cellular components (CC), and 10 biological processes (BP). The KEGG enrichment analysis revealed that the differentially expressed genes were significantly enriched in pathways related to immunity, inflammation, and various metabolic processes, in which a total of two downregulated miRNAs after infection and eight upregulated miRNAs related to immunity and inflammation were screened in ASFV-infected pigs vs. healthy pigs. The network of miRNA-mRNA showed that the mRNA target genes were strongly regulated by ssc-miR-214, ssc-miR-199b-3p, and ssc-miR-199a-3p. The mRNA target genes were enriched into the MAPK signaling pathway, Toll-like receptor signaling pathway, TNF signaling pathway, and IL-17 signaling pathway by using a KEGG enrichment analysis. Therefore, ASFV could regulate immunity and metabolism-related pathways in infected pigs by inducing differential expression of miRNAs. These results provided a new basis for further elucidating the interactions between ASFV and the host as well as the immunity regulation mechanisms of ASFV, which will be conducive to better controlling ASF.

Berbamine Hydrochloride Inhibits African Swine Fever Virus Infection In Vitro

African swine fever virus (ASFV) causes a viral disease in swine with a mortality rate of approximately 100%, threatening the global pig industry's economic development. However, vaccines are not yet commercially available, and other antiviral therapeutics, such as antiviral drugs, are urgently needed. In this study, berbamine hydrochloride, a natural bis-benzylisoquinoline alkaloid isolated from the traditional Chinese herb Berberis amurensis, showed significant antiviral activity against ASFV. The 50% cytotoxic concentration (CC₅₀) of berbamine hydrochloride in porcine alveolar macrophages (PAMs) was 27.89 μM. The antiviral activity assay demonstrated that berbamine hydrochloride inhibits ASFV in a dose-dependent manner. In addition, a 4.14 log TCID₅₀ decrease in the viral titre resulting from non-cytotoxic berbamine hydrochloride was found. Moreover, the antiviral activity of berbamine hydrochloride was maintained for 48h and took effect at multiplicities of infection (MOI) of 0.01, 0.1, and 1. The time-of-addition analysis revealed an inhibitory effect throughout the entire virus life-cycle. A subsequent viral entry assay verified that berbamine hydrochloride blocks the early stage of ASFV infection. Moreover, similar anti-ASFV activity of berbamine hydrochloride was also found in PK-15 and 3D4/21 cells. In summary, these results indicate that berbamine hydrochloride is an effective anti-ASFV natural product and may be considered a novel antiviral drug.

In vitro and in vivo antiviral activity of nucleoside analogue cHPMPC against African swine fever virus replication

African swine fever virus (ASFV) causes a haemorrhagic disease affecting wild boar and domestic pigs which can result in morbidity and fatality rates of up to 100%. ASFV is a large double-stranded DNA virus which replicates predominantly in the cell cytoplasm and codes for its replication and transcription machinery. No vaccine is widely available and control depends on early detection, culling of infected herds and adherence to biosecurity measures. In this study the small molecule nucleoside analogue, cyclic cidofovir (cHPMPC), was evaluated for its ability to inhibit replication of four different ASFV genotypes in primary porcine macrophages. Time of addition studies demonstrated that cHPMPC effectively inhibits ASFV replication and late gene expression when added pre-infection or early post-infection but not when added at late times, suggesting the drug target may be the virus DNA polymerase, or the RNA polymerase involved in late transcription. Oral administration of cHPMPC delayed onset of clinical signs and significantly reduced viral titres in blood and tissues of treated pigs. These results indicate that cHPMPC is a promising compound for further development to control ASFV outbreaks.

Synthesis of 1-Amino-3-oxo-2,7-naphthyridines via Smiles Rearrangement: A New Approach in the Field of Chemistry of Heterocyclic Compounds

In this paper we describe an efficient method for the synthesis of new heterocyclic systems: furo[2,3-c]-2,7-naphthyridines 6, as well as a new method for the preparation of 1,3-diamino-2,7-naphthyridines 11. For the first time, a Smiles rearrangement was carried out in the 2,7-naphthyridine series, thus gaining the opportunity to synthesize 1-amino-3-oxo-2,7-naphthyridines 4, which are the starting compounds for obtaining furo[2,3-c]-2,7-naphthyridines. The cyclization of alkoxyacetamides 9 proceeds via two different processes: the expected formation of furo[2,3-c]-2,7-naphthyridines 10 and the ‘unexpected’ formation of 1,3-diamino-2,7-naphthyridines 11 (via a Smiles type rearrangement).

Antiviral activity of brequinar against African swine fever virus infection in vitro

African swine fever virus (ASFV) is a double-stranded DNA virus that causes an acute and hemorrhagic disease in domestic swine, resulting in significant economic losses to the global porcine industry. The lack of vaccines and antiviral drugs highlights the urgent need for antiviral studies against ASFV. Here, we report that brequinar (BQR), which is a specific inhibitor of dihydroorotate dehydrogenase, robustly inhibits ASFV replication in Vero cells, as well as in porcine macrophages. We demonstrate that BQR exerts its antiviral activity in a dose-dependent manner through the depletion of pyrimidine pool. Although BQR does not affect the synthesis of an early viral protein, pI215L, the synthesis of late viral proteins, p17 and p72, is suppressed in the presence of BQR. We also show that BQR is able to induce cellular antiviral response in ASFV-infected macrophages by enhancing the expression of interferon-stimulated genes. Taken together, our study reveals that targeting nucleotide biosynthesis represents a promising strategy for developing antiviral agents against ASFV.

Virus-Induced Membrane Fusion in Neurodegenerative Disorders

A growing body of epidemiological and research data has associated neurotropic viruses with accelerated brain aging and increased risk of neurodegenerative disorders. Many viruses replicate optimally in senescent cells, as they offer a hospitable microenvironment with persistently elevated cytosolic calcium, abundant intracellular iron, and low interferon type I. As cell-cell fusion is a major driver of cellular senescence, many viruses have developed the ability to promote this phenotype by forming syncytia. Cell-cell fusion is associated with immunosuppression mediated by phosphatidylserine externalization that enable viruses to evade host defenses. In hosts, virus-induced immune dysfunction and premature cellular senescence may predispose to neurodegenerative disorders. This concept is supported by novel studies that found postinfectious cognitive dysfunction in several viral illnesses, including human immunodeficiency virus-1, herpes simplex virus-1, and SARS-CoV-2. Virus-induced pathological syncytia may provide a unified framework for conceptualizing neuronal cell cycle reentry, aneuploidy, somatic mosaicism, viral spreading of pathological Tau and elimination of viable synapses and neurons by neurotoxic astrocytes and microglia. In this narrative review, we take a closer look at cell-cell fusion and vesicular merger in the pathogenesis of neurodegenerative disorders. We present a "decentralized" information processing model that conceptualizes neurodegeneration as a systemic illness, triggered by cytoskeletal pathology. We also discuss strategies for reversing cell-cell fusion, including, TMEM16F inhibitors, calcium channel blockers, senolytics, and tubulin stabilizing agents. Finally, going beyond neurodegeneration, we examine the potential benefit of harnessing fusion as a therapeutic strategy in regenerative medicine.