Highly efficient inhibition of spring viraemia of carp virus replication in vitro mediated by bavachin, a major constituent of psoralea corlifonia Lynn

Drug delivery system based on metal-organic framework improved 5-Fluorouracil against spring viremia of carp virus

Spring viremia of carp virus (SVCV), as a high pathogenicity pathogen, has seriously restricts the healthy and sustainable development of cyprinid farming industry. In this study, we selected 5-Fluorouracil (5-Fu) as the drug model based on zeolitic imidazolate framework-8 (ZIF-8) to construct a drug delivery system (5-Fu@ZIF-8), and the anti-SVCV activity was detected in vitro and in vivo. The results showed 5-Fu@ZIF-8 was uniform cubic particle with truncated angle and smooth surface, and the particle size was 90 nm. The anti-SVCV activity in vitro results showed that the highest inhibition rate of 5-Fu was 77.93% at 40 mg/L and the inhibitory concentration at half-maximal activity (IC50) was 20.86 mg/L. For 5-Fu@ZIF-8, the highest inhibition rate was 91.36% at 16 mg/L, and the IC50 value was 5.85 mg/L. In addition, the cell viability was increased by 18.1% after 5-Fu treatment. Similarly, after 5-Fu@ZIF-8 treatment, the cell viability increased by 27.3%. Correspondingly, in vivo experimental results showed the viral loads reduced by 18.1% on the days 7 and the survival rate increased to 19.4% at 80 mg/L after 5-Fu treatment. For 5-Fu@ZIF-8, the viral loads reduced by 41.2% and the survival rate increased to 54.8%. Mechanistically, 5-Fu inhibits viral replication by regulating p53 expression and promoting early apoptosis in infected cells. All results indicated that 5-Fu@ZIF-8 improved the anti-SVCV activity; it may be a potential strategy to construct a drug-loaded system with ZIF-8 as a carrier for the prevention and treatment of aquatic diseases.

In Vitro Anti-Rotaviral Activity of Bavachin Isolated from Psoralea corylifolia L. (Fabaceae)

Rotavirus is the main causative agent of viral gastroenteritis among young animals worldwide. Currently, no clinically approved or effective antiviral drugs are available to combat rotavirus infections. Herein, we evaluated the anti-rotaviral activities of extracts and bavachin isolated from Psoralea corylifolia L. (Fabaceae) (P. corylifolia) against the bovine rotavirus G8P[7] and porcine rotavirus G5P[7] in vitro. Two assay strategies were performed: (1) a virucidal assay to reduce viral infectivity by virus neutralization and (2) a post-treatment assay to assess viral replication suppression. The results from the virucidal assay showed that the extracts and bavachin did not exert anti-rotaviral activities. In the follow-up analysis after treatment, bavachin exhibited robust antiviral efficacy, with 50% effective concentration (EC50) values of 10.6 μM (selectivity index [SI] = 2.38) against bovine rotavirus G8P[7] and 13.0 μM (SI = 1.94) against porcine rotavirus G5P[7]. Bavachin strongly suppressed viral RNA synthesis in the early (6 h) and late stages (18 h) after rotaviral infection. These findings strongly suggest that bavachin may have hindered the virions by effectively inhibiting the early stages of the virus replication cycle after rotaviral infection. Furthermore, confocal imaging showed that bavachin suppressed viral protein synthesis, notably that of the rotaviral protein (VP6). These results suggest that bavachin has strong antiviral activity against rotaviruses, inhibits viral replication, and is a candidate natural therapeutic drug targeting rotaviral infection. The utilization of bavachin isolated from P. corylifolia may contribute to decreased mortality rates, lower medication expenses, and enhanced economic viability in domestic farms.

Application of rhein as an immunostimulant controls spring viremia of carp virus infection

In recent years, the exploration of natural compounds possessing both immunostimulatory and antiviral activities has attracted growing attention in aquaculture research. Consequently, the pursuit of identifying natural products exhibiting anti-SVCV potential as immunostimulants holds significant promise, offering a pathway to mitigate the economic ramifications inflicted by SVCV outbreaks in aquaculture settings. Among them, rhein emerges as a particularly compelling contender. Boasting a widespread distribution, well-established extraction methods, and multiple biological activities, it has exhibited the capacity to enhance the antiviral activity of host cells in vitro by blocking the viral internalization process, with a peak inhibition rate of 44.0%. Based on this intervention, rhein inhibited apoptosis and mitochondrial damage triggered by SVCV infection, ultimately producing a significant antiviral effect. Moving beyond the laboratory setting, rhein's efficacy translates effectively into in vivo scenarios. It has demonstrated substantial antiviral potency by increasing the expression of antiviral-related genes, most notably, retinoic acid-inducible gene I (RIG-I), interferon-φ (IFN-φ) and IFN-stimulated gene product 15 (ISG15). In concert with this genetic modulation, rhein efficiently reduces the viral load, precipitating a consequential enhancement in the survival rate of SVCV-infected fish, elevating it to an encouraging 16%. In conclusion, the outcomes of our investigation offer a compelling testament to rhein's potential as a valuable immunomodulator in the battle against SVCV infections in aquaculture, and the remarkable attributes exhibited by rhein underscore its viability for future commercial deployment.

4'-(8-(4-Methylimidazole)-octyloxy)-arctigenin: The first inhibitor of fish rhabdovirus glycoprotein

Spring viraemia of carp virus (SVCV), a highly pathogenic rhabdovirus, could cause spring viraemia of carp (SVC) with up to 90% lethality. Like other rhabdoviruses, the entry of SVCV into susceptible cells was mediated by a single envelope glycoprotein G. Specific inhibitors targeting the glycoprotein were the most effective means to alleviate the epidemic. The programs including SWISS-MODEL, I-TASSER, Phyre2 and AlphaFold2 were used to build a three-dimensional structural model of glycoprotein. The structural comparison between SVCV-G and homology protein VSV-G revealed that the SVCV glycoprotein ectodomain (residues 19 to 466) folded into four distinct domains. Based on the potential small molecule binding sites on glycoprotein surfaces, virtual screening of the anti-SVCV drug libraries was performed using Autodock software and 4'-(8-(4-Methylimidazole)-octyloxy)-arctigenin (MOA) with a high binding affinity was identified. The solubility enhancer tags including trigger factor and maltose binding protein were fused with the ectodomain of glycoprotein, and the target protein with a purity of about 90% was successfully obtained. The interaction confirmation tests revealed that the fluorescence intensity of a characteristic peak induced by the endogenous chromophores in glycoprotein was decreased with the addition of MOA, indicating changes in the microenvironment of glycoprotein. Moreover, the interaction could cause a slight conformational change in glycoprotein, as shown by the content of β-turn, β-folding, and random coil of protein all increased with the decrease of α-helix content after the addition of MOA compound. These results demonstrated that MOA could act as a novel drug against fish rhabdovirus via direct targeting of glycoprotein.

A Scd1-mediated metabolic alteration participates in liver responses to low-dose bavachin

Hepatotoxicity induced by bioactive constituents in traditional Chinese medicines or herbs, such as bavachin (BV) in Fructus Psoraleae, has a prolonged latency to overt drug-induced liver injury in the clinic. Several studies have described BV-induced liver damage and underlying toxicity mechanisms, but little attention has been paid to the deciphering of organisms or cellular responses to BV at no-observed-adverse-effect level, and the underlying molecular mechanisms and specific indicators are also lacking during the asymptomatic phase, making it much harder for early recognition of hepatotoxicity. Here, we treated mice with BV for 7 days and did not detect any abnormalities in biochemical tests, but found subtle steatosis in BV-treated hepatocytes. We then profiled the gene expression of hepatocytes and non-parenchymal cells at single-cell resolution and discovered three types of hepatocyte subsets in the BV-treated liver. Among these, the hepa3 subtype suffered from a vast alteration in lipid metabolism, which was characterized by enhanced expression of apolipoproteins, carboxylesterases, and stearoyl-CoA desaturase 1 (Scd1). In particular, increased Scd1 promoted monounsaturated fatty acids (MUFAs) synthesis and was considered to be related to BV-induced steatosis and polyunsaturated fatty acids (PUFAs) generation, which participates in the initiation of ferroptosis. Additionally, we demonstrated that multiple intrinsic transcription factors, including Srebf1 and Hnf4a, and extrinsic signals from niche cells may regulate the above-mentioned molecular events in BV-treated hepatocytes. Collectively, our study deciphered the features of hepatocytes in response to BV insult, decoded the underlying molecular mechanisms, and suggested that Scd1 could be a hub molecule for the prediction of hepatotoxicity at an early stage.

Antiviral effects of natural small molecules on aquatic rhabdovirus by interfering with early viral replication

Spring viremia of carp virus (SVCV) is globally widespread and poses a serious threat to aquatic ecology and aquaculture due to its broad host range. To develop effective agents to control SVCV infection, we selected 16 naturally active small molecules to assess their anti-SVCV activity. Notably, dihydroartemisinin (DHA) (100 µmol/L) and (S, S)-(+)-tetrandrine (TET) (16 µmol/L) exhibited high antiviral effects in epithelioma papulosum cyprinid (EPC) cells, with inhibitory rates of 70.11% and 73.54%, respectively. The possible antiviral mechanisms were determined as follows: 1. Pre-incubation with DHA and TET decreased viral particle infectivity in fish cells, suggesting that horizontal transmission of SVCV in the aquatic environment was disrupted; 2. Although neither had an effect on viral adhesion, TET (but not DHA) interfered with SVCV entry into host cells (>80%), suggesting that TET may have an antiviral function in early viral replication. For in vivo study, both agents enhanced the survival rate of SVCV-infected zebrafish by 53.3%, significantly decreased viral load, and modulated the expression of antiviral-related genes, indicating that DHA and TET may stimulate the host innate immune response to prevent viral infection. Overall, our findings indicated that DHA and TET had positive effects on suppressing SVCV infection by affecting early-stage viral replication, thus holding great potential as immunostimulants to reduce the risk of aquatic rhabdovirus disease outbreaks.

The effective components of herbal medicines used for prevention and control of fish diseases

The increasing demand for fish consumption has promoted the rapid development of fish aquaculture. With the continuous expansion of culture scale and the deterioration of culture environment, various diseases have broken out frequently, leading to huge economic losses to fish farming. Antibiotics and chemicals are common options to prevent and control of fish diseases, but their use is now restricted or even banned due to serious problems such as drug residues, pathogen resistance, and environmental pollution. Herbs and their extracts have increasingly become promising supplements and alternatives, because of their effectiveness, safety, environmental friendliness and less drug resistance. The application of herbal medicines in prevention and control of fish diseases is mainly attributed to the powerful immune enhancement, antioxidation or direct anti-pathogenic efficacies of their effective components, including mainly polyphenols, polysaccharides, saponins, flavonoids, alkaloids, and essential oils. Recently these herbal active ingredients have been extensively studied for their efficacies in prevention and control of viral, bacterial, parasitic, and fungal diseases in fish. In the present paper, we comprehensively summarize the research progress of the active ingredients of herbal medicines used for prevention and control of fish diseases, especially of their action mechanisms, and highlight the potential application of the herbal medicines in fish aquaculture.

Synthesized Magnolol Derivatives Improve Anti-Micropterus salmoides Rhabdovirus (MSRV) Activity In Vivo

Micropterus salmoides rhabdovirus (MSRV) is a primary viral pathogen in largemouth bass aquaculture, which leads to tremendous economic losses yearly. Currently, there are no approved drugs for the treatment and control of this virus. Our previous studies screened the herb Magnolia officinalis from many traditional Chinese medicines, and we isolated and identified magnolol as its main active compound against multiple rhabdoviruses, including MSRV. On the basis of the structure–activity relationship and pharmacophore model of magnolol, two new magnolol derivatives, namely, hydrogenated magnolol and 2,2′-dimethoxy-magnolol, were designed and synthesized. Their anti-MSRV activities were systematically investigated both in vitro and in vivo. By comparing the half-maximal inhibitory concentration (IC₅₀), it was found that hydrogenated magnolol possessed a higher anti-MSRV activity than magnolol and 2,2′-dimethoxy-magnolol, with an IC₅₀ of 13.37 μM. Furthermore, hydrogenated magnolol exhibited a protective effect on the grass carp ovary (GCO) cell line by reducing the cytopathic effect induced by MSRV. Further studies revealed that hydrogenated magnolol did not directly impact virions or interfere with MSRV adsorption. It worked within the 6–8 h of the phase of virus replication. In vivo treatment of MSRV infection with magnolol and hydrogenated magnolol showed that they significantly improved the survival rate by 44.6% and 62.7%, respectively, compared to MSRV-infected groups. The viral load measured by the expression of viral glycoprotein in the organs including the liver, spleen, and kidney also significantly decreased when fish were intraperitoneally injected at a dose of 20 mg/kg. Altogether, the structural optimization of magnolol via hydrogenation of the propylene groups increased its anti-MSRV activity both in vitro and in vivo. These results may provide a valuable reference for anti-MSRV drug discovery and development in aquaculture.

Review of Medicinal Plants and Active Pharmaceutical Ingredients against Aquatic Pathogenic Viruses

Aquaculture offers a promising source of economic and healthy protein for human consumption, which can improve wellbeing. Viral diseases are the most serious type of diseases affecting aquatic animals and a major obstacle to the development of the aquaculture industry. In the background of antibiotic-free farming, the development and application of antibiotic alternatives has become one of the most important issues in aquaculture. In recent years, many medicinal plants and their active pharmaceutical ingredients have been found to be effective in the treatment and prevention of viral diseases in aquatic animals. Compared with chemical drugs and antibiotics, medicinal plants have fewer side-effects, produce little drug resistance, and exhibit low toxicity to the water environment. Most medicinal plants can effectively improve the growth performance of aquatic animals; thus, they are becoming increasingly valued and widely used in aquaculture. The present review summarizes the promising antiviral activities of medicinal plants and their active pharmaceutical ingredients against aquatic viruses. Furthermore, it also explains their possible mechanisms of action and possible implications in the prevention or treatment of viral diseases in aquaculture. This article could lay the foundation for the future development of harmless drugs for the prevention and control of viral disease outbreaks in aquaculture.

Medicinal plants with anti-SARS-CoV activity repurposing for treatment of COVID-19 infection: A systematic review and meta-analysis

The novel SARS-CoV-2 (severe acute respiratory syndrome coronavirus) has emerged as a significant threat to public health with startling drawbacks in all sectors globally. This study investigates the practicality of some medicinal plants for SARS-CoV-2 therapy using a systematic review and meta-analysis of their reported SARS-CoV-1 inhibitory potencies. Relevant data were systematically gathered from three databases, viz., Web of Science, PubMed and Scopus. The information obtained included botanical information, extraction method and extracts concentrations, as well as the proposed mechanisms. Fourteen articles describing 30 different plants met our eligibility criteria. Random effects model and subgroup analysis were applied to investigate heterogeneity. According to subgroup analysis, the substantial heterogeneity of the estimated mean based on the IC ₅₀ values reporting the most potent anti-SARS-CoV 3C--like protease (3CLpro) inhibitors (10.07 %, p < 0.0001), was significantly higher compared to the most active anti-SARS-CoV papain-like protease (PLpro) inhibitors (6.12 %, p < 0.0001). More importantly, the literature analysis revealed that fruit extracts of Rheum palmatum L. and the compound cryptotanshinone isolated from the root of Salvia miltiorrhiza (IC ₅₀ = 0.8 ± 0.2 μmol L^-1) were excellent candidates for anti--SARS-CoV targeting PLpro. Meanwhile, iguesterin (IC ₅₀ = 2.6 ± 0.6 μmol L^-1) isolated from the bark of Tripterygium regelii emerged as the most excellent candidate for anti-SARS--CoV targeting 3CLpro. The present systematic review and meta-analysis provide valuable and comprehensive information about potential medicinal plants for SARS-CoV-2 inhibition. The chemotypes identified herein can be adopted as a starting point for developing new drugs to contain the novel virus.

In vitro and in vivo inhibition of a novel arctigenin derivative on aquatic rhabdovirus

Spring viraemia of carp virus (SVCV) poses a serious threat to aquaculture industry due to the lack of approved antiviral treatments. Therefore, a novel arctigenin derivative, 4-(2-methylimidazole) octanoxy-arctigenin (MON), was synthesized to assess the antiviral activity against SVCV in vitro and in vivo. The results indicated MON decreased the SVCV glycoprotein (G) gene expression in vitro by a maximum inhibitory rate of > 99% at 3.5 μM. Furthermore, MON showed the protective effect on epithelioma papulosum cyprinid (EPC) cells and considerably decreased the cytopathic effect (CPE). More importantly, MON inhibited SVCV G gene expression levels in vitro at the half-maximal activity (IC₅₀) of 0.18 μM at 48 h. For in vivo studies, MON demonstrated anti-SVCV activity by enhancing the survival rate of zebrafish (Danio rerio) after infection via pelvic fin base injection. These results tended to be consistent with MON decreasing the SVCV titer of infected zebrafish. During this time, viral loads of the spleen and kidney have declined in SVSV-infected zebrafish. Based on the histopathological assay, MON exhibited the high protective effect in the spleen and kidney of SVCV-infected fish. Combined, MON is on track to become a novel agent to address SVCV infection in aquaculture.

Ophiopogon japonicus inhibits white spot syndrome virus proliferation in vivo and enhances immune response in Chinese mitten crab Eriocheir sinensis

White spot syndrome virus (WSSV) is a fatal pathogen threatening global crustacean industry with no commercially available drugs to control. Herbal medicines have been widely used to treat a number of viral infections, which could offer a rich reserve for antiviral drug discovery. Here, we evaluated the inhibition activities of 30 herbal medicines against WSSV in Chinese mitten crab Eriocheir sinensis. A WSSV infection model in E. sinensis was firstly established in order to determine the antiviral effects of the plant extracts and to explore the potential action mechanisms. Results showed that the highest anti-WSSV activity was obtained by the treatment of Ophiopogon japonicus extract (93.03%, 100 mg/kg). O. japonicus treatment decreased viral loads in a dose-dependent manner and significantly improved the survival of WSSV-challenged crabs. O. japonicus reduced the expression of vital genes in viral life cycle in vivo, particularly for the immediate-early stage gene ie1. Further results indicated that O. japonicus could repress the JAK-STAT signaling pathway to block ie1 transcription. Moreover, O. japonicus could modulate certain immune genes such as the myosin, toll-like receptor, crustin, and prophenoloxidase in the interactions between WSSV and crabs. The up-regulated expression of pro-autophagic factors (Gabarap and Atg7) and elevated levels of antioxidant enzymes (SOD, CAT and GSH) suggested that O. japonicus may induce autophagy and attenuate WSSV-induced oxidative stress. Taken together, O. japonicus could inhibit WSSV proliferation and improve the survival of WSSV-challenged crabs. Thus, O. japonicus may have the potential to be developed as a preventive or therapeutic agent against WSSV, and its effective compounds merit further isolation and identification.

Bavachin produces immunoadjuvant activity by targeting the NFAT signaling pathway

BACKGROUND

Bavachin, a flavonoid compound isolated from the seeds and fruits of Psoralea corylifolia l. (family Fabaceae), is used as a traditional medicine in Asia. Indeed, it is reported to have various medicinal functions such as estrogenic and antiinflammatory activities among others. However, to date, the effects of bavachin on T cell activation have yet to be reported.

PURPOSE AND STUDY DESIGN

We aimed to determine the effects of bavachin on the activation of a human T cell line in vitro and on antigen-specific immune responses in mice in vivo.

METHODS

In a nuclear factor of activated T cells (NFAT) activity assay, the Jurkat T cell line expressing a luciferase reporter driven by an NFAT-response element was stimulated with antihuman CD3/CD28 antibody and bavachin. Furthermore, the level of cytokine production was measured in the Jurkat T cell line stimulated with phorbol 12-myristate 13-acetate/ionomycin and bavachin using an IL-2 ELISA and a cytometric bead array assay. For in vivo analyses, mice were subcutaneously immunized with an antigen (ovalbumin protein) and bavachin, and the immune responses of mice were analyzed by FACS analysis, a T cell proliferation assay, a cytokine ELISA, and an antiovalbumin-specific antibody ELISA.

RESULTS

We found that bavachin activated NFAT-mediated transcription in the human T cell line in vitro. In mice, when bavachin was administered with the antigen, an increase in T cell responses and antibody production specific to the antigen was observed.

CONCLUSION

Our results suggest that bavachin has immunoadjuvant and immunomodulation effects, which arise through activation of the NFAT signaling pathway.

Evaluation of the antiviral activity of naringenin, a major constituent of Typha angustifolia, against white spot syndrome virus in crayfish Procambarus clarkii

White spot syndrome virus (WSSV) is a serious pathogen threatening global crustacean aquaculture with no commercially available drugs. Herbal medicines widely used in antiviral research offer a rich reserve for drug discovery. Here, we investigated the inhibitory activity of 13 herbal medicines against WSSV in crayfish Procambarus clarkii and discovered that naringenin (NAR) has potent anti-WSSV activity. In the preliminary screening, the extracts of Typha angustifolia displayed the highest inhibitory activity on WSSV replication (84.62%, 100 mg/kg). Further, NAR, the main active compound of T. angustifolia, showed a much higher inhibition rate (92.85%, 50 mg/kg). NAR repressed WSSV proliferation followed a dose-dependent manner and significantly improved the survival of WSSV-challenged crayfish. Moreover, pre- or post-treatment of NAR displayed a comparable inhibition on the viral loads. NAR decreased the transcriptional levels of vital genes in viral life cycle, particularly for the immediately early-stage gene ie1. Further results showed that NAR could decrease the STAT gene expression to block ie1 transcription. Besides, NAR modulated immune-related gene Hsp70, antioxidant (cMnSOD, mMnSOD, CAT, GST), anti-inflammatory (COX-1, COX-2) and pro-apoptosis-related factors (Bax and BI-1) to inhibit WSSV replication. Overall, these results suggest that NAR may have the potential to be developed as preventive or therapeutic agent against WSSV.

Bavachin exerted anti-neuroinflammatory effects by regulation of A20 ubiquitin-editing complex

Neuroinflammation is a major pathophysiological contributor to the progression of the central nervous system disorders. Bavachin is a natural product belonging to the flavonoid class. The anti-neuroinflammatory effect and the molecular mechanisms are not well understood. In this study, we found bavachin can exert anti-neuroinflammatory effect via inhibition of nuclear factor-kappa B (NF-κB) signaling. We found that bavachin can obviously upregulate the expression of A20 (TNFAIP3) in microglial cells. Further studies suggested siRNA-A20 knockdown treatment can attenuate the inhibitory effects of bavachin on neuroinflammation. We further found bavachin can increase the interaction of ubiquitin-editing enzyme A20 complex including A20, Tax1-binding protein 1 (TAX1BP1) and Itch, the subsequently downregulated the K63-ubiquitination of TNF receptor associated factor 6 (TRAF6) and NF-κB signaling pathway. Altogether, our results indicated that bavachin exerted anti-neuroinflammatory effects through inhibition of NF-κB signaling mediated by regulation of ubiquitin-editing enzyme A20 complex. Our finding has important clinical significance for the potential application of bavachin in the treatment of neurological disorders.

Small Molecule Inhibitors of White Spot Syndrome Virus: Promise in Shrimp Seedling Culture

Rapid production of prawn (Litopenaeus vannamei) under artificial pressure can result in a series of obvious challenges and is vulnerable to serious losses related to aquatic environmental issues and the unrestrained outbreak of white spot syndrome (WSS). However, to date, there are no therapeutic strategies to contain the spread of the virus. Here, we synthesized 27 coumarin derivatives and evaluated their anti-white spot syndrome virus (WSSV) activity in L. vannamei larvae. We demonstrated that electron-withdrawing and electron-giving substituent groups play an important role in reducing toxicity and WSSV replication, respectively. Two coumarin C2 (2-amino-5-oxo-4-(p-tolyl)-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile) and C7 (2-amino-4-(4-chlorophenyl)-5-oxo-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile) were regarded as the most promising anti-WSSV compounds with maximum antiviral response <5% and median effective concentration <10 mg/L. The mortality of WSSV-infected larvae decreased by more than 60% after exposure to C2 and C7. With continuous immersion of C2 and C7 exchange, the mortality further decreased to 40% at 120 h. Additionally, C2 and C7 are the relatively stable in aquacultural water, making these agents suitable for use in inhibiting WSSV horizontal transmission in static aquaculture systems. These results showed the marked advantages of using C2 and C7 in the shrimp industry, and suggest that they hold potential for the treatment and prevention of WSSV infection in shrimp seedling culture.

Study on the 2-Phenylchroman-4-One Derivatives and their anti-MERS-CoV Activities

Study on the 2-phenylchroman-4-one derivatives and their anti-MERS-CoVactivities.

Antiviral activity of anisomycin against spring viraemia of carp virus in epithelioma papulosum cyprini cells and zebrafish

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Anisomycin caused profound inhibition of SVCV replication in EPC cells.

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Anisomycin blocked morphological cell damage caused by SVCV replication.

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Anisomycin suppressed SVCV replication in vivo, resulting in a prolonged survival of infected zebrafish.

Spring viraemia of carp (SVC) caused by spring viraemia of carp virus (SVCV) is an acute and highly lethal viral disease of cyprinid fish. However, effective therapy for SVC is still scarce until now. Here we evaluated the inhibition of anisomycin (Ani), a metabolite produced by Streptomyces griseolus, on the replication of SVCV in vitro and in vivo. Our results demonstrated that Ani could suppress SVCV replication with the maximum inhibitory rate > 95% in epithelioma papulosum cyprini (EPC) cells. And the half maximal inhibitory concentrations (IC₅₀) of Ani on SVCV glycoprotein (G), nucleoprotein (N) and phosphoprotein mRNA expressions were 21.79, 13.13 and 12.24 nM, respectively. Besides, Ani decreased SVCV-induced cytopathic effects and nucleus damages. As expected, Ani also showed a strong anti-SVCV activity in vivo, as indicated by inhibiting viral gene expression and increasing the survival rate of zebrafish. Intraperitoneal injection of Ani increased the survival rate of zebrafish by 30% and markedly inhibited the expressions of G and N mRNA by > 60% in kidney and spleen at day 1 and day 4 post-infection. Results so far suggest that Ani as a powerful agent against SVCV can be applied to the control of SVC in aquaculture.

Antiviral efficiency of a coumarin derivative on spring viremia of carp virus in vivo

Spring viraemia of carp (SVC) in aquaculture is challenging because there are few preventative measures and/or treatments. The previous study demonstrated that an antiviral coumarin derivative, 7-(4-(4-methyl-imidazole))-coumarin (C2), inhibits spring viremia of carp virus (SVCV) infection by targeting Nrf2-ARE signaling pathway in fish cells. Thus, we hypothesized whether C2 may be used as a potential therapeutic agent for controlling SVCV infection in aquaculture. In this study, SVCV infectivity was significantly inhibited in vitro in a dose-dependent manner by preincubation with C2. C2 was verified against SVCV in zebrafish, in which the mortality and viral titer in fish body were decreased. Like other coumarins, C2 was stable with a prolonged inhibitory half-life (3.5 days) at 15 °C in the early stage of SVCV infection. The results show that horizontal transmission of SVCV was reduced by C2 in a static cohabitation challenge model, especially for recipient fish in injection treatment, which suggested that C2 may be suitable as a possible therapeutic agent for SVCV in aquaculture. Overall, this study provides the new insight that a small molecule antiviral drug can be used to control rhabdovirus infection in fish aquacultures.