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Viruses "hijack" cellular metabolism to complete their proliferation. Glucose is an important source of energy and carbon in the synthesis of precursor molecules in host cells, and its metabolism is regulated dramatically during virus infection. Here, we reviewed the mechanism of virus infection that alters glucose transport, expression of glucose metabolism-related genes (glycolysis, pentose phosphate pathway, gluconeogenesis) in cells, as well as islet cells and insulin receptors. It provides references for study of virus-altering cellular glucose metabolism.

Infectious spleen and kidney necrosis virus (ISKNV) has brought huge economic loss to the aquaculture industry. Through interfering with the viral replication and proliferation process that depends on host cells, its pathogenicity can be effectively reduced. In this study, we investigated the role of asparagine metabolites in ISKNV proliferation. The results showed that ISKNV infection up-regulated the expression of some key enzymes of the asparagine metabolic pathway in Chinese perch brain (CPB) cells. These key enzymes, including glutamic oxaloacetic transaminase 1/2 (GOT1/2) and malate dehydrogenase1/2 (MDH1/2) associated with the malate-aspartate shuttle (MAS) pathway and asparagine synthetase (ASNS) involved in the asparagine biosynthesis pathway, were up-regulated during ISKNV replication and release stages. In addition, results showed that the production of ISKNV was significantly reduced by inhibiting the MAS pathway or reducing the expression of ASNS by 1.3-fold and 0.6-fold, respectively, indicating that asparagine was a critical limiting metabolite for ISKNV protein synthesis. Furthermore, when asparagine was added to the medium without glutamine, ISKNV copy number was restored to 92% of that in the complete medium, indicating that ISKNV could be fully rescued from the absence of glutamine by supplementing asparagine. The above results indicated that asparagine was a critical factor in limiting the effective replication of ISKNV, which provided a new idea for the treatment of aquatic viral diseases. [ABSTRACT FROM AUTHOR]

The disease caused by Largemouth bass ranavirus (LMBV) is one of the most severe viral diseases in largemouth bass (Micropterus salmoides). It is crucial to evaluate the genetic resistance of largemouth bass to LMBV and develop markers for disease-resistance breeding. In this study, 100 individuals (45 resistant and 55 susceptible) were sequenced and evaluated for resistance to LMBV and a total of 2,579,770 variant sites (SNPs-single-nucleotide polymorphisms (SNPs) and insertions–deletions (InDels)) were identified. A total of 2348 SNPs-InDels and 1018 putative candidate genes associated with LMBV resistance were identified by genome-wide association analyses (GWAS). Furthermore, GO and KEGG analyses revealed that the 10 candidate genes (MHC II, p38 MAPK, AMPK, SGK1, FOXO3, FOXO6, S1PR1, IL7R, RBL2, and GADD45) were related to intestinal immune network for IgA production pathway and FoxO signaling pathway. The acquisition of candidate genes related to resistance will help to explore the molecular mechanism of resistance to LMBV in largemouth bass. The potential polymorphic markers identified in this study are important molecular markers for disease resistance breeding in largemouth bass. [ABSTRACT FROM AUTHOR]

Background: Vaccinations are still the most effective means of preventing and controlling fish viral diseases, and cells are an important substrate for the production of a viral vaccine. Therefore, the rapid-stable growth and virus sensitivity of cells are urgently needed. Methods: Chinese perch brain 100th passage (CPB p100) were acclimated in a low serum with 5% FBS L-15 for 50 passages, then transferred to 8% FBS L-15 for 150 passages. Additionally, the morphology and cell type of CPB 300th passage (CPB p300) cells were identified. We analyzed the transfection efficiency and virus sensitivity of CPB p300 cells, and then optimized the conditions of ISKNV, SCRV, and LMBV multiplication in CPB cells. Results: CPB p300 cells were more homogeneous, and the spread diameter (20–30) µm in CPB p300 cells became the dominant population. The doubling time of CPB p300 was 1.5 times shorter than that of CPB p100.However, multiplication rate of CPB p300 was 1.37 times higher than CPB p100. CPB p300 cells were susceptible to ISKNV, SCRV, and LMBV, and the optimal conditions of ISKNV, SCRV, and LMBV multiplication were simultaneous incubation, 0.6 × 105 cells/cm2 and MOI = 0.1; infection at 48 h, 0.8 × 105 cells/cm2 and MOI = 0.01; simultaneous incubation, 0.7 × 105 cells/cm2 and MOI = 0.05, respectively. The time and economic costs of ISKNV, SCRV, and LMBV multiplication in CPB p300 cells were significantly reduced. Conclusions: The acquisition of CPB p300 cells laid a good material foundation for the production of ISKNV, SCRV, and LMBV vaccines. [ABSTRACT FROM AUTHOR]

Mandarin fish (Siniperca chuatsi) is one of the important cultured fish species in China. Infectious spleen and kidney necrosis virus (ISKNV) and Siniperca Chuatsi rhabdovirus (SCRV) have hindered the development of mandarin fish farming industry. Vaccination is the most effective method for control of viral diseases, however viral vaccine production requires the large-scale culture of cells. Herein, a suspension culture system of Chinese perch brain cell (CPB) was developed on Cytodex 1 microcarrier in a stirred bioreactor. Firstly, CPB cells were cultured using Cytodex 1 microcarrier in 125 mL stirring flasks. With the optimum operational parameters, CPB cells grew well, distributed uniformly, and could fully cover the microcarriers. Then, CPB cells were digested with trypsin and expanded step-by-step with different expansion ratios from the 125 mL stirring bottle to a 500 mL stirring bottle, and finally to a 3-L bioreactor. Results showed that with an expansion ratio of 1:3, we achieved a high cell density level (2.25 × 106 cells/mL) with an efficient use of the microcarriers, which also confirmed the data obtained from the 125 mL stirring flask. Moreover, obvious cytopathic effects (CPE) were observed in the suspended CPB cells post-infection with ISKNV and SCRV. This study provided a large-scale culture system of CPB cells for virus vaccine production. [ABSTRACT FROM AUTHOR]

The tripartite motif (TRIM) proteins play critical roles in viral infection by modulating innate immunity. However, the molecular and antiviral activity of TRIM59 in mandrain fish is not fully understood. In present study, we cloned and sequenced the TRIM59 core sequence and explored its characteristics in Mandarin fish. The Siniperca chuatsi TRIM59 (scTRIM59) showed relatively high expression in immune-related organs. scTRIM59 expression was significantly down-regulated post ISKNV infection in vivo and vitro, but up-regulated at the early stages of SCRV infection in CPB cells. The overexpression of scTRIM59 inhibited ISKNV and SCRV infection, but decreased the expression of IRF3/IRF7-mediated signal genes. However, knockdown of scTRIM59 promoted the ISKNV and SCRV infection, but increased the expression of IRF3/IRF7-mediated signal genes. Those results indicated that scTRIM59 negatively regulated ISKNV, SCRV infection and IRF3/IRF7-mediated signal genes. This study provided new ideas about the function of scTRIM59. • scTRIM59 was widely expressed in the tissues of mandarin fish, especially in immune organs. • scTRIM59 expression was down-regulated post ISKNV infection, however, scTRIM59 was up-regulated post SCRV infection. • scTRIM59 negatively regulated ISKNV, SCRV infection and IRF3/IRF7-mediated signal genes. [ABSTRACT FROM AUTHOR]

Viral diseases have caused great economic losses to the aquaculture industry. However, there are currently no specific drugs to treat these diseases. Herein, we utilized Siniperca chuatsi as an experimental model, and successfully extracted two tissue factor pathway inhibitors (TFPIs) that were highly distributed in different tissues. We then designed four novel peptides based on the TFPIs, named TS20, TS25, TS16, and TS30. Among them, TS25 and TS30 showed good biosafety and high antiviral activity. Further studies showed that TS25 and TS30 exerted their antiviral functions by preventing viruses from invading Chinese perch brain (CPB) cells and disrupting Siniperca chuatsi rhabdovirus (SCRV)/ Siniperca chuatsi ranairidovirus (SCRIV) viral structures. Additionally, compared with the control group, TS25 and TS30 could significantly reduce the mortality of Siniperca chuatsi , the relative protection rates of TS25 against SCRV and SCRIV were 71.25 % and 53.85 % respectively, and the relative protection rate of TS30 against SCRIV was 69.23 %, indicating that they also had significant antiviral activity in vivo. This study provided an approach for designing peptides with biosafety and antiviral activity based on host proteins, which had potential applications in the prevention and treatment of viral diseases. [Display omitted] • Novel TS25 and TS30 peptides designed based on TFPIs from Siniperca chuatsi. • TS25 and TS30 showed good biosafety and high antiviral activity. • TS25 and TS30 produced antiviral functions by preventing viruses from invading cells and disrupting viral structures. • TS25 and TS30 could significantly reduce the mortality of Siniperca chuatsi. [ABSTRACT FROM AUTHOR]

The PI3K/AKT/p53 signaling pathway is activated by various types of cellular stimuli or pathogenic infection, and then regulates fundamental cellular functions to combat these stimulations. Here, we studied the meaningful roles of PI3K/AKT/p53 in regulating cellular machine such as autophagy, immune responses, as well as antiviral activity in Chinese perch brain (CPB) cells infected by infectious spleen and kidney necrosis virus (ISKNV), which is an agent caused devastating losses in mandarin fish (Siniperca chuatsi) industry. We found that ISKNV infection induced up-regulation of host PI3K/AKT/p53 axis, but inhibited autophagy in CPB cells. Interestingly, activation of PI3K/AKT/p53 axis factors trough agonists or overexpression dramatically decreased host autophagy level, inhibited ISKNV replication, and elevated the expression of immune-related genes in CPB cells. In contrast, suppression of PI3K/AKT/p53 pathway by inhibitors or small interfering RNA (siRNA)-mediated gene silence increased the autophagy and ISKNV replication, but down-regulated immune responses in CPB cells. All these results indicate that PI3K/AKT/p53 pathway plays an important role in anti-ISKNV infection and can be used as a new target for controlling ISKNV disease. • ISKNV infection induced up-regulation of PI3K/AKT/p53 axis, but inhibited autophagy in CPB cells. • Activation of PI3K/AKT/p53 axis factors decreased autophagy level and inhibited ISKNV replication in CPB cells. • Suppression of PI3K/AKT/p53 pathway increased the autophagy and ISKNV replication in CPB cells. • The PI3K/AKT/p53 pathway promotes the expression of immune-related genes in ISKNV-infected CPB cells. [ABSTRACT FROM AUTHOR]

Largemouth bass virus disease (LMBV) and Micropterus salmoides rhabdovirus (MSRV) caused great economic losses to the fish industry. Currently, there are no effective drugs against LMBV and MSRV. Many reports have proved that Chinese herbal drugs (CHDs) possessed antiviral activities. Herein, we investigated antiviral activities of 20 CHD active monomers against MSRV and LMBV in vitro. Results testified that quercetin, coumarin, harpaget, magnolol and hypercin had antiviral activities against LMBV, and chlorogenic acid, quercetin, epigoitrin, limomin and magnolol played remarkable antiviral activities against MSRV. Then, two mixtures drugs of CHD active monomers against MSRV and LMBV were tested and showed noteworthy antiviral activities against MSRV and LMBV in vivo and vitro , respectively. Meanwhile, the two mixtures drugs also increased the expression of type I and type III IFN mediated signal genes. Those results indicated that the two mixtures drugs not only directly inhibited viral replication, but also enhanced its antiviral activity by regulating type I and type III IFN production in largemouth bass, which provided a solid foundation for clinical use of the two mixtures drugs against LMBVD and MSRVD. • We selected five chinese herbal drug active monomers against LMBV and MSRV, respectively. • Two mixture of CHD active monomers showed noteworthy antiviral activity against MSRV and LMBV in vivo and vitro, respectively. • Two mixture of CHD active monomers increased the expression of type I and type III IFN mediated signal genes. • Two mixture of CHD active monomerscan be as the green and healthy fishery drugs in the treatment of LMBVD and MSRVD. [ABSTRACT FROM AUTHOR]

Autophagy plays important functions in viral replication and pathogenesis. In this study, we investigated the role of autophagy in the replication of infectious kidney and spleen necrosis virus (ISKNV), an agent that has caused devastating losses in Chinese perch ( Siniperca chuatsi ) industry. We found that ISKNV infection triggered the complete autophagic process, as demonstrated by microtubule-associated protein 1 light chain 3B II (LC3B-II) conversion, an increased accumulation of punctate GFP-LC3-expressing cells, a higher number of autophagosome-double-membrane vesicles in the cytoplasm, and increased levels of autophagic flux in CPB cells. Then, we investigated the role of autophagy in the process of ISKNV replication. Results showed that inducing autophagy by rapamycin promoted ISKNV replication and proteins synthesis but decreased extracellular virus yields. While, blocking autophagosome-lysosome fusion by chloroquine (CQ) promoted infectious virus yields in culture supernatant. These results offer insight into the complex interactions between ISKNV and host cell, providing new insights into viral pathogenesis and antiviral treatment strategies. [ABSTRACT FROM AUTHOR]

Infectious spleen and kidney necrosis virus disease (ISKNVD) caused significant economic losses to the fishery industry. So it is urgent to develop an effective measure for prevention ISKNVD. In this study, we investigated the effects of gefitinib against ISKNV in vitro and vivo. The gefitinib inhibited viral protein synthesis and decreased viral titers with the dose-dependent manner in Chinese perch brain cells (CPB) cells. Gefitinib was observed to inhibit ISKNV infection by blocking ISKNV entry into CPB cells. Interestingly, gefitinib inhibited EGFR/PI3K phosphorylation and suppressed microfilament gathering induced by ISKNV. At the same time, gefitinib inhibited ISKNV infection and decreased pathogenicity of ISKNV in vivo. These results suggested that gefitinib prevented ISKNV infection by blocking virus-mediated endocytosis. This research provided potential of gefitinib for preventing ISKNVD. • Gefitinib inhibited ISKNV infection by blocking ISKNV entry into CPB cells. • Gefitinib prevented ISKNV infection by blocking virus-mediated endocytosis. • Gefitinib inhibited ISKNV infection and decreased the pathogenicity of ISKNV in vivo. • Gefitinib can be used as a blocker for prevention ISKNVD. [ABSTRACT FROM AUTHOR]

In recent years, Siniperca chuatsi rhabdovirus (SCRV) caused serious threats and huge economic losses in Siniperca chuatsi aquaculture industry. Vaccination is the most efficacious and cost-effective strategy to control this viral disease. However, SCRV-QY vaccine quality control is vital for successful prevention. Herein, we generated a pair of high affinity antibodies against SCRV-QY virus and established a double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) for detecting the SCRV-QY antigen amounts. In this assay, monoclonal antibody 4H8 was selected as capture antibody and 4E12 labeled HRP for detector antibody. A standard curve was generated using the SCRV concentration versus OD value with the linear range of concentration of 78.125~5000 ng/ml. The antigen content of 3 batches SCRV-QY inactivated vaccines were quantitatively detected by using the DAS-ELISA. The results showed that antigen contents of SCRV-QY inactivated vaccines were positively correlated with the viral titers. In conclusion, this DAS-ELISA was an accurate, quick and efficacious method for detecting antigen concentration of inactivated SCRV-QY vaccines. • A pair of high affinity antibodies against SCRV-QY virus were generated. • A double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) for detecting the SCRV antigen was established. • A standard curve with the linear range of 78.125~5000 ng/ml was generated using the SCRV concentration versus OD value. • This DAS-ELISA method was accurate, quick and efficacious detection of antigen concentration inactivated SCRV-QY vaccines. [ABSTRACT FROM AUTHOR]

The bluegill sunfish, Lepomis macrochirus , is an important aquacultural and recreational species in southern China because of its excellent taste, rapid growth rate, and good looks. At present, few pathogens are known to affect the bluegill sunfish. However, an iridovirus-like disease recently caused heavy losses to the bluegill sunfish aquaculture industry in Guangdong, China. We report that a virus, designated BSMIV-SD-20171020, was isolated from diseased bluegill sunfish in China. The isolate was efficiently propagated in a Chinese perch brain (CPB) cell line. The cytopathic effect was observed, the MCP gene PCR amplified, and the virus observed with electron microscopy. Its viral titer in CPB cells reached 104.13 TCID 50 mL−1. The mortality rate was 100% when bluegill sunfish were challenged with BSMIV-SD-20171020 at a dose of 103.13 TCID 50 /fish. A histopathological examination revealed basophilic hypertrophied cells in the intestine, liver, and spleen. A nucleotide sequence alignment and phylogenetic analysis of the major capsid protein revealed that isolate BSMIV-SD-20171020 is the species Infectious spleen and kidney necrosis virus (ISKNV), in the genus Megalocytivirus. • The ISKNV-like virus BSMIV-22SD-20171020 was firstly isolated from diseased bluegill sunfish. • The isolate is belonging to genus Megalocytivirus genotype I by MCP genes sequences analysis. • The isolate was pathogenic to the bluegill sunfish, with 100% mortality after viral infection. [ABSTRACT FROM AUTHOR]