EGCG Restricts PRRSV Proliferation by Disturbing Lipid Metabolism

Intervention strategies targeting virus and host factors against porcine reproductive and respiratory syndrome virus: A systematic review

Porcine reproductive and respiratory syndrome (PRRS) caused by porcine reproductive and respiratory syndrome virus (PRRSV) causes considerable economic losses to the global swine industry every year and seriously hinders the healthy development of this industry. Although tremendous efforts have been made over the past 30 years toward the development of prevention and control strategies against PRRSV infection, to date, treatments with proven efficacy have yet to be available due to our incomplete understanding of the molecular basis and complexity of the infection machinery. This review systematically discusses recent advances in the research and development of anti-PRRSV therapies targeting different stages of the viral life cycle. Furthermore, this review puts forward novel intervention targets and research approaches based on our in-depth exploration of virus-host interactions and the latest biological technologies, which have the potential to complement or transform current anti-PRRSV strategies and become breakthrough points for the control of PRRS in the future.

Porcine reproductive and respiratory syndrome virus activates lipid synthesis through a ROS-dependent AKT/PCK1/INSIG/SREBPs axis

The porcine reproductive and respiratory syndrome virus (PRRSV) is a highly contagious pathogen in pigs. This study aimed to investigate the impact of PRRSV infection on cellular metabolism, particularly focusing on lipid metabolism to understand its role in promoting viral replication. We conducted a metabolic analysis on MARC-145 cells before and after PRRSV infection. Our results demonstrated that the most significant alterations in cellular metabolism, accounting for 40.8 % of total changes, were related to lipid metabolism. These changes were primarily driven by the activation of sterol regulatory-element binding proteins (SREBPs), critical regulators of lipid biosynthesis. To understand the mechanisms behind SREBPs activation by PRRSV, we investigated the involvement of upstream effectors, specifically protein kinase B (AKT) and phosphoenolpyruvate carboxykinase 1 (PCK1). Our findings indicated that PRRSV infection triggered AKT activation, leading to the subsequent activation of PCK1. Activated PCK1 then phosphorylated insulin-induced genes (INSIGs), resulting in their degradation. This degradation facilitated the translocation of SREBPs from the endoplasmic reticulum to the nucleus. Additionally, we observed that PRRSV infection stimulated the production of reactive oxygen species (ROS), which played a critical role in activating AKT. Collectively, our findings demonstrate that PRRSV enhances lipid synthesis through a ROS-dependent AKT/PCK1/INSIG/SREBPs signaling axis, which provides new insights into the metabolic strategies employed by PRRSV.

Molecular mechanisms of EGCG-CSH/n-HA/CMC in promoting osteogenic differentiation and macrophage polarization

2. This research investigates the impact of the EGCG-CSH/n-HA/CMC composite material on bone defect repair, emphasizing its influence on macrophage polarization and osteogenic differentiation of BMSCs. Comprehensive evaluations of the composite's physical and chemical characteristics were performed. BMSC response to the material was tested in vitro for proliferation, migration, and osteogenic potential. An SD rat model was employed for in vivo assessments of bone repair efficacy. Both transcriptional and proteomic analyses were utilized to delineate the mechanisms influencing macrophage behavior and stem cell differentiation. The material maintained excellent structural integrity and significantly promoted BMSC functions critical to bone healing. In vivo results confirmed accelerated bone repair, and molecular analysis highlighted the role of macrophage M2 polarization, particularly through changes in the SIRPA gene and protein expression. EGCG-CSH/n-HA/CMC plays a significant role in enhancing bone repair, with implications for macrophage and BMSC function. Our findings suggest that targeting SIRPA may offer new therapeutic opportunities for bone regeneration.

Let-7f-5p Modulates Lipid Metabolism by Targeting Sterol Regulatory Element-Binding Protein 2 in Response to PRRSV Infection

Porcine reproductive and respiratory syndrome (PRRS) has caused substantial damage to the pig industry. MicroRNAs (miRNAs) were found to play crucial roles in modulating the pathogenesis of PRRS virus (PRRSV). In the present study, we revealed that PRRSV induced let-7f-5p to influence lipid metabolism to regulate PRRSV pathogenesis. A transcriptome analysis of PRRSV-infected PK15CD163 cells transfected with let-7f-5p mimics or negative control (NC) generated 1718 differentially expressed genes, which were primarily associated with lipid metabolism processes. Furthermore, the master regulator of lipogenesis SREBP2 was found to be directly targeted by let-7f-5p using a dual-luciferase reporter system and Western blotting. The findings demonstrate that let-7f-5p modulates lipogenesis by targeting SREBP2, providing novel insights into miRNA-mediated PRRSV pathogenesis and offering a potential antiviral therapeutic target.

Honeysuckle-Derived miR2911 Inhibits Replication of Porcine Reproductive and Respiratory Syndrome Virus by Targeting Viral Gene Regions

The highly abundant and stable antiviral small RNA derived from honeysuckle, known as miR2911, has been shown to play a key role in inhibiting influenza virus infection and SARS-CoV-2 infection. However, whether miR2911 inhibits the replication of porcine reproductive and respiratory syndrome virus (PRRSV) remains unknown. Hence, this study investigated the mechanisms underlying the action of miR2911 during PRRSV infection. Six targets of miR2911 within the PRRSV orf1 (Nsp2: 2459 to 2477, 1871 to 1892, 954 to 977, and 1271 to 1292; Nsp1: 274 to 296 and 822 to 841) were successfully identified by using the miRanda v1.0b software. The miR2911 target sequence was analyzed by target sequence comparison, and only individual base mutations existed in different prevalent strains, and the miR2911 target region was highly conserved among different strains. Subsequently, through the dual luciferase reporter gene assay and miR2911 overexpression assay, it was demonstrated that miR2911 significantly inhibits the replication of PRRSV by targeting regions of PRRSV Nsp1 and Nsp2. These findings offer new insights for the development of novel anti-PRRSV drugs.

Virucidal effects of eucalyptus essential oil on porcine reproductive and respiratory syndrome virus

Currently, the efficacy of vaccination for preventing and controlling PRRSV is insufficient. Therefore, there is an urgent need for novel effective preventive strategies. This study aimed to investigate the antiviral effect of Eucalyptus essential oil (EEO) against PRRSV in vitro. Marc-145 cells were infected with PRRSV (rJXA1-R), and the toxicity of EEO in the cells was measured using the Cell Counting Kit-8 method. Additionally, the antiviral effect of EEO on PRRSV-infected cells was assessed using three treatment methods: drug administration post-PRRSV inoculation (post-treatment), drug administration before PRRSV inoculation (pre-treatment), and simultaneous drug administration and PRRSV inoculation (co-treatment). The EEO could not inhibit virus adsorption and/or replication since post-treatment and pre-treatment did not prevent viral infectivity. However, EEO exerted a significant virucidal effect on PRRSV. When PRRSV-infected cells were treated with 0.0156, 0.0312, and 0.0625% EEO, the cell survival rates were 55.37, 118.96, and 121.67%, respectively, and the titer of progeny virions decreased from 5.77 Log10TCID50 to 5.21 Log10TCID50, 0.55 Log10TCID50, and less than 0.167 Log10TCID50, respectively (where TCID50 is the 50% tissue culture infected dose). The fluorescence intensity of the PRRSV N protein significantly decreased in the indirect immunofluorescence assay. When cells were co-treated with EEO (0.0625%) and PRRSV (1000 TCID50) for 15 min, the viral particles were inactivated, and PRRSV (1000 TCID50) particles loss infectivity when the co-treatment time reached 60 min. In a word, EEO has no obvious therapeutic effect on PRRSV infection, but it can effectively inactivate virus particles and make them lose the ability to infect cells. These findings provide insights for the development and use of EEO to treat PRRS.

Molecular mechanism of autophagy in porcine reproductive and respiratory syndrome virus infection

Porcine reproductive and respiratory syndrome virus (PRRSV), a significant pathogen affecting the swine industry globally, has been shown to manipulate host cell processes, including autophagy, to facilitate its replication and survival within the host. Autophagy, an intracellular degradation process crucial for maintaining cellular homeostasis, can be hijacked by viruses for their own benefit. During PRRSV infection, autophagy plays a complex role, both as a defense mechanism of the host and as a tool exploited by the virus. This review explores the current understanding of the molecular mechanisms underlying autophagy induction under PRRSV infection, its impact on virus replication, and the potential implications for viral pathogenesis and antiviral strategies. By synthesizing the latest research findings, this article aims to enhance our understanding of the intricate relationship between autophagy and PRRSV, paving the way for novel therapeutic approaches against this swine pathogen.

Proteomics analysis of PK-15 cells infected with porcine parvovirus and the effect of PCBP1 on PPV replication

Porcine parvovirus (PPV) is one of the most important pathogens that cause reproductive failure in pigs. However, the pathogenesis of PPV infection remains unclear. Proteomics is a powerful tool to understand the interaction between virus and host cells. In the present study, we analyzed the proteomics of PPV-infected PK-15 cells. A total of 32 and 345 proteins were differentially expressed at the early and replication stages, respectively. Subsequent gene ontology annotation and Kyoto Encyclopedia of Genes and Genomes enrichment analysis showed these differentially expressed proteins were significantly enriched in pathways including toll-like receptor signaling pathway, tumor necrosis factor signaling pathway, and viral carcinogenesis. The expression of poly (rC) binding protein 1 (PCBP1) was observed to decrease after PPV infection. Overexpressed or silenced PCBP1 expression inhibited or promoted PPV infection. Our studies established a foundation for further exploration of the multiplication mechanism of PPV.

IMPORTANCE

Porcine parvovirus (PPV) is a cause of reproductive failure in the swine industry. Our knowledge of PPV remains limited, and there is no effective treatment for PPV infection. Proteomics of PPV-infected PK-15 cells was conducted to identify differentially expressed proteins at 6 hours post-infection (hpi) and 36 hpi. Gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis showed that various pathways participate in PPV infection. Poly (rC) binding protein 1 was confirmed to inhibit PPV replication, which provided potential targets for anti-PPV infection. Our findings improve the understanding of PPV infection and pave the way for future research in this area.

Pseudorabies virus manipulates mitochondrial tryptophanyl-tRNA synthetase 2 for viral replication

The pseudorabies virus (PRV) is identified as a double-helical DNA virus responsible for causing Aujeszky's disease, which results in considerable economic impacts globally. The enzyme tryptophanyl-tRNA synthetase 2 (WARS2), a mitochondrial protein involved in protein synthesis, is recognized for its broad expression and vital role in the translation process. The findings of our study showed an increase in both mRNA and protein levels of WARS2 following PRV infection in both cell cultures and animal models. Suppressing WARS2 expression via RNA interference in PK-15 ​cells led to a reduction in PRV infection rates, whereas enhancing WARS2 expression resulted in increased infection rates. Furthermore, the activation of WARS2 in response to PRV was found to be reliant on the cGAS/STING/TBK1/IRF3 signaling pathway and the interferon-alpha receptor-1, highlighting its regulation via the type I interferon signaling pathway. Further analysis revealed that reducing WARS2 levels hindered PRV's ability to promote protein and lipid synthesis. Our research provides novel evidence that WARS2 facilitates PRV infection through its management of protein and lipid levels, presenting new avenues for developing preventative and therapeutic measures against PRV infections.

Resveratrol and (-)-Epigallocatechin-3-gallate Regulate Lipid Metabolism by Activating the AMPK Pathway in Hepatocytes

The purpose of this study was to explore the effects of Res and EGCG on cell growth, cellular antioxidant levels, and cellular lipid metabolism in hepatocytes. In this experiment, leghorn male hepatoma (LMH) cells were used as hepatocytes. The results showed that 6.25-25 μM Res and EGCG had no adverse effects on cell viability and growth. Meanwhile, with the increasing dosage of Res and EGCG, the contents of total cholesterol (TC), total glyceride (TG), and malondialdehyde (MDA) in hepatocytes decreased significantly (p < 0.05), while the contents of glutathione peroxidase (GSH-Px), total superoxide dismutase (T-SOD), and catalase (CAT) increased significantly (p < 0.05). In addition, western blot results showed that Res and EGCG could significantly increase the expression of p-AMPK protein and reduce the expression of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) protein in hepatocytes (p < 0.05). Moreover, q-PCR results showed that with the increase in Res and EGCG, the expression of cholesterol- and fatty acid synthesis-related genes decreased significantly (p < 0.05). In conclusion, Res and EGCG can increase the antioxidant capacity of hepatocytes and reduce the synthesis of TC and TG in hepatocytes by activating AMPK, thereby regulating lipid metabolism in hepatocytes.

Tissue expression of porcine transient receptor potential mucolipin protein channels and their differential responses to porcine reproductive and respiratory syndrome virus infection in vitro

Introduction

Porcine reproductive and respiratory syndrome virus (PRRSV) infection results in a serious disease, posing a huge economic threat to the global swine industry. The transient receptor potential mucolipin proteins (TRPMLs) have been shown to be strongly associated with virus infection and other physiological processes in humans, but their tissue distribution and responses to PRRSV in pigs remain unknown.

Material and Methods

Quantitative reverse-transcription PCR analysis was undertaken to determine the optimal primer for TRPML expression detection and for quantifying that expression individually in different pig tissue samples. Meat Animal Research Center 145 (MARC-145) monkey kidney cells and the TRPML-specific activator mucolipin synthetic agonist 1 (ML-SA1) were used to reveal the relationship between TRPML and PRRSV-2 infection.

Results

The best primers for each TRPML gene used in a fluorescence-based quantitative method were identified and TRPML1 was found to be highly expressed in the kidneys and liver of pigs, while TRPML2 and TRPML3 were observed to be primarily expressed in the kidney and spleen tissues. The expression of TRPML2 was upregulated with the rise in PRRSV-2 infection titre but not the expression of TRPML1 or TRPML3, and ML-SA1 inhibited PRRSV-2 in a dose-dependent manner.

Conclusion

Our research revealed the gene expression of TRPMLs in pigs and identified that TRPML channels may act as key host factors against PRRSV infection, which could lead to new targets for the prevention and treatment of pig infectious diseases.

Cholesterol depletion inhibits rabies virus infection by restricting viral adsorption and fusion

Rabies is an ancient zoonotic disease caused by the rabies virus (RABV), and a sharp increase in rabies cases and deaths were observed following the COVID-19 pandemic, indicating that it still poses a severe public health threat in most countries in the world. Cholesterol is one of the major lipid components in cells, and the exact role of cholesterol in RABV infection remains unclear. In this study, we initially observed that cellular cholesterol levels were significantly elevated in RABV infected cells, while cholesterol depletion by using methyl-β-cyclodextrin (MβCD) could restrict RABV entry. We further found that decreasing the cholesterol level of the viral envelope could change the bullet-shaped morphology of RABV and dislodge the glycoproteins on its surface to affect RABV entry. Moreover, the depletion of cholesterol could decrease lysosomal cholesterol accumulation to inhibit RABV fusion. Finally, it was found that the depletion of cholesterol by MβCD was due to the increase of oxygen sterol production in RABV-infected cells and the enhancement of cholesterol efflux by activating liver X receptor alpha (LXRα). Together, our study reveals a novel role of cholesterol in RABV infection, providing new insight into explore of effective therapeutics for rabies.

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.

Porcine reproductive and respiratory syndrome virus regulates lipid droplet accumulation in lipid metabolic pathways to promote viral replication

Porcine reproductive and respiratory syndrome (PRRS) is a severe respiratory disease caused by porcine reproductive and respiratory syndrome virus (PRRSV) that can lead to the abortion of pregnant sows and decreased boar semen quality. However, the mechanisms of PRRSV replication in the host have not yet been fully elucidated. As lipid metabolism and lipid droplets (LDs) have been reported to play important roles in the replication of various viruses, we aimed to explore the mechanisms through which LDs affect PRRSV replication. Laser confocal and transmission electron microscopy revealed that PRRSV infection promoted intracellular LD accumulation, which was significantly reduced by treatment with the NF-κB signaling pathway inhibitors BAY11-7082 and metformin hydrochloride (MH). In addition, treatment with a DGAT1 inhibitor significantly reduced the protein expression of Phosphorylated NF-ΚB P65and PIκB and the transcription of IL-1β and IL-8 in the NF-κB signaling pathway. Furthermore, we showed that the reduction of the NF-κB signaling pathway and LDs significantly reduced PRRSV replication. Together, the findings of this study suggest a novel mechanism through which PRRSV regulates the NF-κB signaling pathway to increase LD accumulation and promote viral replication. Moreover, we demonstrated that both BAY11-7082 and MH can reduce PRRSV replication by reducing the NF-κB signaling pathway and LD accumulation. This study lays a theoretical foundation for research on the mechanism of PRRS prevention and control, as well as the research and development of antiviral drugs.

Piceatannol as an Antiviral Inhibitor of PRV Infection In Vitro and In Vivo

Pseudorabies virus (PRV) belongs to the family Herpesviridae. PRV has a wide host range and can cause cytopathic effects (CPEs) in PK-15 cells. Therefore, PRV was used as a model to study the antiviral activity of piceatannol. The results showed that piceatannol could restrain PRV multiplication in PK-15 cells in a dose-dependent manner. The 50% inhibitory concentration (IC₅₀) was 0.0307 mg/mL, and the selectivity index (SI, CC₅₀/IC₅₀) was 3.68. Piceatannol could exert an anti-PRV effect by reducing the transcription level of viral genes, inhibiting PRV-induced apoptosis and elevating the levels of IL-4, TNF-α and IFN-γ in the serum of mice. Animal experiments showed that piceatannol could delay the onset of disease, reduce the viral load in the brain and kidney and reduce the pathological changes in the tissues and organs of the mice to improve the survival rate of the mice (14.3%). Therefore, the anti-PRV activity of piceatannol in vivo and in vitro was systematically evaluated in this study to provide scientific data for developing a new alternative measure for controlling PRV infection.

TMEM41B Is an Interferon-Stimulated Gene That Promotes Pseudorabies Virus Replication

Pseudorabies virus (PRV) is a double-stranded DNA virus that causes Aujeszky's disease and is responsible for economic loss worldwide. Transmembrane protein 41B (TMEM41B) is a novel endoplasmic reticulum (ER)-localized regulator of autophagosome biogenesis and lipid mobilization; however, the role of TMEM41B in regulating PRV replication remains undocumented. In this study, PRV infection was found to upregulate TMEM41B mRNA and protein levels both in vitro and in vivo. For the first time, we found that TMEM41B could be induced by interferon (IFN), suggesting that TMEM41B is an IFN-stimulated gene (ISG). While TMEM41B knockdown suppressed PRV proliferation, TMEM41B overexpression promoted PRV proliferation. We next studied the specific stages of the virus life cycle and found that TMEM41B knockdown affected PRV entry. Mechanistically, we demonstrated that the knockdown of TMEM41B blocked PRV-stimulated expression of the key enzymes involved in lipid synthesis. Additionally, TMEM41B knockdown played a role in the dynamics of lipid-regulated PRV entry-dependent clathrin-coated pits (CCPs). Lipid replenishment restored the CCP dynamic and PRV entry in TMEM41B knockdown cells. Together, our results indicate that TMEM41B plays a role in PRV infection via regulating lipid homeostasis. IMPORTANCE PRV belongs to the alphaherpesvirus subfamily and can establish and maintain a lifelong latent infection in pigs. As such, an intermittent active cycle presents great challenges to the prevention and control of PRV disease and is responsible for serious economic losses to the pig breeding industry. Studies have shown that lipids play a crucial role in PRV proliferation. Thus, the manipulation of lipid metabolism may represent a new perspective for the prevention and treatment of PRV. In this study, we report that the ER transmembrane protein TMEM41B is a novel ISG involved in PRV infection by regulating lipid synthesis. Therefore, our findings indicate that targeting TMEM41B may be a promising approach for the development of PRV vaccines and therapeutics.

Ethyl Gallate Inhibits Bovine Viral Diarrhea Virus by Promoting IFITM3 Expression, Lysosomal Acidification and Protease Activity

Bovine viral diarrhea virus (BVDV) is a highly contagious viral disease which causes economic losses to the cattle industry. Ethyl gallate (EG) is a phenolic acid derivative which has various potentials to modulate the host response to pathogens, such as via antioxidant activity, antibacterial activity, inhibition of the production of cell adhesion factors, and so on. This study aimed to evaluate if EG influences BVDV infection in Madin-Darby Bovine Kidney (MDBK) cells, and to understand the antiviral mechanism. Data indicated that EG effectively inhibited BVDV infection by co-treatment and post-treatment in MDBK cells with noncytotoxic doses. In addition, EG suppressed BVDV infection at an early stage of the viral life cycle by blocking entry and replication steps but not viral attachment and release. Moreover, EG strongly inhibited BVDV infection by promoting interferon-induced transmembrane protein 3 (IFITM3) expression, which localized to the cytoplasm. The protein level of cathepsin B was significantly reduced by BVDV infection, whereas with treatment with EG, it was significantly enhanced. The fluorescence intensities of acridine orange (AO) staining were significantly decreased in BVDV-infected cells but increased in EG-treated cells. Finally, Western blot and immunofluorescence analyses demonstrated that EG treatment significantly enhanced the protein levels of autophagy markers LC3 and p62. Chloroquine (CQ) significantly increased IFITM3 expression, and Rapamycin significantly decreased it. Thus, EG may regulate IFITM3 expression through autophagy. Our results showed that EG could have a solid antiviral activity on BVDV replication in MDBK cells via increased IFITM3 expression, lysosomal acidification, protease activity, and regulated autophagy. EG might have value for further development as an antiviral agent.

Flavonoids as Potential Antiviral Agents for Porcine Viruses

Flavonoids are types of natural substances with phenolic structures isolated from a variety of plants. Flavonoids have antioxidant, anti-inflammatory, anticancer, and antiviral activities. Although most of the research or applications of flavonoids are focused on human diseases, flavonoids also show potential applicability against porcine virus infection. This review focuses on the recent progress in antiviral mechanisms of potential flavonoids against the most common porcine viruses. The mechanism discussed in this paper may provide a theoretical basis for drug screening and application of natural flavonoid compounds and flavonoid-containing herbs to control porcine virus infection and guide the research and development of pig feed additives.