Pseudorabies Virus Pathogenesis Research Articles

Insight into the Interaction Mechanism of Pseudorabies Virus Infection

The pseudorabies virus (PRV), also known as suid alphaherpesvirus 1 (SuAHV-1), has garnered significant attention due to its broad host range and the economic losses it incurs in the swine industry. This review aims to provide a comprehensive understanding of the intricate virus–host interactions during PRV infection, focusing on the evasion strategies of the virus against the host responses. We also summarize the mechanisms by which PRV manipulates the host cell machinery to facilitate its replication and spread, while simultaneously evading detection and clearance by the immune system. Furthermore, we discuss the latest advancements, such as metabolic, autophagic, and apoptotic pathways in studying these interactions, highlighting the role of various cellular factors and pathways in elucidating virus–host dynamics. By integrating these insights, the article aims to provide a comprehensive overview of the molecular mechanisms underlying PRV pathogenesis and host response, paving the way for the development of novel therapeutic strategies against this virus.

The heat shock protein DNAJB8 inhibits pseudorabies virus replication by autophagy

Pseudorabies virus (PRV) effectively utilizes numerous host proteins and pathways to establish a successful infection. Consequently, it becomes imperative to investigate novel host factors implicated in viral infections to gain a deeper understanding of PRV pathogenesis. In this study, we reveal that the host heat shock protein, DNAJB8, functions as a negative regulator in PRV replication. Our findings indicated that both mRNA and protein levels of DNAJB8 were downregulated in cells infected with PRV. Further analysis demonstrated that overexpressing DNAJB8 suppressed PRV replication, whereas its knockdown enhanced viral replication. From a mechanistic perspective, DNAJB8 promoted cellular autophagy, subsequently impeding viral replication. Additionally, we discovered that the transcription factor SOX30 regulated DNAJB8 expression, thereby influencing viral replication. Collectively, these findings enhance our comprehension of the roles played by DNAJB8 and SOX30 in viral replication, broadening our knowledge of virus-host interactions.

Pseudorabies virus upregulates low-density lipoprotein receptors to facilitate viral entry.

Pseudorabies virus (PRV) is the causative agent of Aujeszky's disease in pigs. The low-density lipoprotein receptor (LDLR) is a transcriptional target of the sterol-regulatory element-binding proteins (SREBPs) and participates in the uptake of LDL-derived cholesterol. However, the involvement of LDLR in PRV infection has not been well characterized. We observed an increased expression level of LDLR mRNA in PRV-infected 3D4/21, PK-15, HeLa, RAW264.7, and L929 cells. The LDLR protein level was also upregulated by PRV infection in PK-15 cells and in murine lung and brain. The treatment of cells with the SREBP inhibitor, fatostatin, or with SREBP2-specific small interfering RNA prevented the PRV-induced upregulation of LDLR expression as well as viral protein expression and progeny virus production. This suggested that PRV activated SREBPs to induce LDLR expression. Furthermore, interference in LDLR expression affected PRV proliferation, while LDLR overexpression promoted it. This indicated that LDLR was involved in PRV infection. The study also demonstrated that LDLR participated in PRV invasions. The overexpression of LDLR or inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9), which binds to LDLR and targets it for lysosomal degradation, significantly enhanced PRV attachment and entry. Mechanistically, LDLR interacted with PRV on the plasma membrane, and pretreatment of cells with LDLR antibodies was able to neutralize viral entry. An in vivo study indicated that the treatment of mice with the PCSK9 inhibitor SBC-115076 promoted PRV proliferation. The data from the study indicate that PRV hijacks LDLR for viral entry through the activation of SREBPs.IMPORTANCEPseudorabies virus (PRV) is a herpesvirus that primarily manifests as fever, pruritus, and encephalomyelitis in various domestic and wild animals. Owing to its lifelong latent infection characteristics, PRV outbreaks have led to significant financial setbacks in the global pig industry. There is evidence that PRV variant strains can infect humans, thereby crossing the species barrier. Therefore, gaining deeper insights into PRV pathogenesis and developing updated strategies to contain its spread are critical. This study posits that the low-density lipoprotein receptor (LDLR) could be a co-receptor for PRV infection. Hence, strategies targeting LDLR may provide a promising avenue for the development of effective PRV vaccines and therapeutic interventions.

Pseudorabies virus causes splenic injury via inducing oxidative stress and apoptosis related factors in mice

Pseudorabies virus (PRV) is an immunosuppressive virus that causes significant damage to the pig industry. This study aimed to investigate the effects of PRV on oxidative stress and apoptotic related in the spleen of mice to provide basis knowledge for further research on the pathogenesis of PRV in mice model. 36 mice were randomly two groups, the control group which only received 200 μL PBS and infection group which was subcutaneously infected with 200 μL of 1 × 103 TCID50/100 μL PRV, respectively. Spleen tissues in each group were collected for further experiments at 48, 72, and 96 h post-infection (hpi). Pathological observation was performed by hematoxylin and eosin Y staining. Biochemical and Flow cytometry methods were used to determine the reactive oxygen species profile and apoptosis of the spleen post-infection and apoptosis detection. In addition, q-PCR and Western blot were adopted to measure the apoptotic conditions of the spleen infected with PRV. The results indicated that the reactive oxygen species (ROS) level in the PRV infection group was remarkedly increased (p < 0.01) at a time-dependent pattern. Furthermore, the Malondialdehyde levels in the spleen of mice in the infection group increased (p < 0.01) in a time-dependent mode. However, the activity of Catalase, Superoxide dismutase, and glutathione peroxidase and the content of Glutathione in the infection group were decreased with the control group (p < 0.01) at a time-dependent manner. In addition, the ratio of splenocyte apoptosis in the infection group significantly increased (p < 0.01) in a time-dependent manner. In conclusion, PRV infection causes apoptosis of the spleen via oxidative stress in mice.

Acute transcriptomic changes in murine RAW 264.7 cells following pseudorabies virus infection.

Next-generation sequencing enables the evaluation of gene expression changes resulting from virus-host interactions at the RNA level. Pseudorabies virus (PRV) causes substantial economic loss in the swine industry. Recent research has revealed that PRV can be transmitted to and infect humans as well. To identify physiopathological and pathological responses post-PRV infection, we characterized transcriptomic changes in the murine RAW 264.7 cell line over the course of 36 h. In total, 156, 153, and 190 differentially expressed genes were identified at 2 h, 12 h, and 36 h, respectively. Seven differentially expressed genes (Trim27, Ccdc117, Mrps12, Ccl4, Cerkl, Ubald1, and Hmga1-rs1) were present across all treatment groups. Our findings expand our knowledge of gene regulation and immune response following PRV infection. These differentially expressed genes can subsequently improve our understanding of PRV pathogenesis.

Comparative proteomic analysis of PK15 swine kidney cells infected with a pseudorabies pathogenic variant and the Bartha-K/61 vaccine strain.

Pseudorabies virus (PRV) is the causative agent of Aujeszky's disease and is communicable across species. In particular, the emergence of PRV variants in 2011 have resulted in serious economic losses to the Chinese pig industry. In this study, we used tandem mass tag (TMT) quantitative protein analysis to identify differentially expressed proteins between the PRV variant strain SD-2017 and the vaccine strain Bartha-K/61 in the swine kidney cell line PK15. Overall, we identified 4690 proteins for SD-2017 infection compared with the mock-infected control cells. We found 162 differentially expressed cellular proteins including 41 up- and 121 down-regulated proteins. SD-2017-infected PK15cells differential proteins were primarily related to gap junctions, the phagosome, antigen processing and presentation, cell adhesion molecules and peroxisome pathways. Compared to Bartha-K/61-infected PK15cells, SD-2017-infected cells displayed differentially expressed proteins involved in tryptophan metabolism, mitophagy and Notch signaling. Western blot analysis of MARK2, TSR1 and TMED1 three representative proteins validated the reliability of the TMT data. This study is an initial at-tempt to compare the proteomes of PK15cells infected by a PRV variant and a vaccine strain using TMT technology to provide new insights into the mechanisms of PRV pathogenesis and immune evasion.

Pseudorabies Virus: From Pathogenesis to Prevention Strategies.

Pseudorabies (PR), also called Aujeszky’s disease (AD), is a highly infectious viral disease which is caused by pseudorabies virus (PRV). It has been nearly 200 years since the first PR case occurred. Currently, the virus can infect human beings and various mammals, including pigs, sheep, dogs, rabbits, rodents, cattle and cats, and among them, pigs are the only natural host of PRV infection. PRV is characterized by reproductive failure in pregnant sows, nervous disorders in newborn piglets, and respiratory distress in growing pigs, resulting in serious economic losses to the pig industry worldwide. Due to the extensive application of the attenuated vaccine containing the Bartha-K61 strain, PR was well controlled. With the variation of PRV strain, PR re-emerged and rapidly spread in some countries, especially China. Although researchers have been committed to the design of diagnostic methods and the development of vaccines in recent years, PR is still an important infectious disease and is widely prevalent in the global pig industry. In this review, we introduce the structural composition and life cycle of PRV virions and then discuss the latest findings on PRV pathogenesis, following the molecular characteristic of PRV and the summary of existing diagnosis methods. Subsequently, we also focus on the latest clinical progress in the prevention and control of PRV infection via the development of vaccines, traditional herbal medicines and novel small RNAs. Lastly, we provide an outlook on PRV eradication.

Metabolomics Analysis of PK-15 Cells with Pseudorabies Virus Infection Based on UHPLC-QE-MS.

Viruses depend on the metabolic mechanisms of the host to support viral replication. We utilize an approach based on ultra-high-performance liquid chromatography/Q Exactive HF-X Hybrid Quadrupole-Orbitrap Mass (UHPLC-QE-MS) to analyze the metabolic changes in PK-15 cells induced by the infections of the pseudorabies virus (PRV) variant strain and Bartha K61 strain. Infections with PRV markedly changed lots of metabolites, when compared to the uninfected cell group. Additionally, most of the differentially expressed metabolites belonged to glycerophospholipid metabolism, sphingolipid metabolism, purine metabolism, and pyrimidine metabolism. Lipid metabolites account for the highest proportion (around 35%). The results suggest that those alterations may be in favor of virion formation and genome amplification to promote PRV replication. Different PRV strains showed similar results. An understanding of PRV-induced metabolic reprogramming will provide valuable information for further studies on PRV pathogenesis and the development of antiviral therapy strategies.

Host Zinc-finger CCHC-type containing protein 3 inhibits pseudorabies virus proliferation by regulating type I interferon signaling

Zinc finger CCHC-type containing protein 3 (ZCCHC3) acts as an antiviral factor that interacts with RIG-I and cGAS to modulate innate signaling against viral infections. Here, we investigated the role of porcine ZCCHC3 during pseudorabies virus (PRV) proliferation. We found that porcine ZCCHC3 plays an inhibitory role in the proliferation of PRV by regulating cellular innate immune responses. Further, overexpression of ZCCHC3 inhibited gB protein levels and viral titers, whereas knockdown of ZCCHC3 promoted viral growth. ZCCHC3 overexpression increased IFN-β expression to upregulate downstream gene expression, thus leading to the suppression of viral replication. However, PRV infection reduced the endogenous expression of ZCCHC3 in permissive cells. Importantly, PRV-encoded UL13 and UL24 proteins were identified to inhibit the expression of ZCCHC3, thus antagonizing its antiviral effect. Collectively, our data underscore the important role of ZCCHC3 against PRV infection and promote understandings of viral proteins in PRV pathogenesis.

Neuropeptide S and its receptor NPSR enhance the susceptibility of hosts to pseudorabies virus infection

The neuropeptide S (NPS) and its receptor (NPSR) represent a signaling system in the brain. Increased levels of NPS and NPSR have been observed in PK15 cells and murine brains in response to pseudorabies virus (PRV) infection, but it remains unclear whether elevated levels of NPS and NPSR are involved in the pathogenic process of PRV infection. In this study, the activities of both NPS and NPSR during PRV pathogenesis were explored in vitro and in vivo by reverse transcription polymerase chain reaction (RT–PCR), PCR, real-time quantitative RT–PCR (qRT–PCR), qPCR, TCID50, and Western blotting methods. NPSR-deficient cells were less susceptible to PRV infection, as evidenced by decreased viral production and PRV-glycoprotein E (gE) expression. In vitro studies showed that exogenous NPS promoted the expression of interleukin 6 (IL-6) mRNA but inhibited interferon β (IFN-β) mRNA expression in PK15 cells after PRV infection. In vivo studies showed that NPS-treated mice were highly susceptible to PRV infection, with decreased survival rates and body weights. In addition, NPS-treated mice showed elevated levels of IL-6 mRNA and STAT3 phosphorylation. However, the expression of IFN-β mRNA was greatly decreased after virus challenge. Contrasting results were obtained from the NPSR-ir-treated groups, which further highlighted the effects of NPS. This study revealed that NPS-treated hosts are more susceptible to PRV infection than controls. Moreover, excessive IL-6/STAT3 and defective IFN-β responses in NPS-treated mice may contribute to the pathogenesis of PRV.

Cytokine storms and pyroptosis are primarily responsible for the rapid death of mice infected with pseudorabies virus.

Pseudorabies virus (PRV), the causative agent of Aujeszky's disease, is one of the most harmful pathogens to the pig industry. PRV can infect and kill a variety of mammals. Nevertheless, the underlying pathogenesis related to PRV is still unclear. This study aims to investigate the pathogenesis induced by PRV in a mouse model. The mice infected with the PRV-HLJ strain developed severe clinical manifestations at 36 h post-infection (hpi), and mortality occurred within 48–72 hpi. Hematoxylin-eosin staining and qRT-PCR methods were used to detect the pathological damage and expression of cytokines related to an immune reaction in brain tissue, respectively. The cytokine storms caused by IFN-α, IFN-β, TNF-α, IL-1β, IL-6 and IL-18 were related to the histopathological changes induced by PRV. This pattern of cytokine secretion depicts an image of typical cytokine storms, characterized by dysregulated secretion of pro-inflammatory cytokines and imbalanced pro-inflammatory and anti-inflammatory responses. In addition, the pyroptosis pathway was also activated by PRV by elevating the expression levels of nod-like receptor protein 3, Caspase-1, Gasdermin-D and interleukin-1β/18. These findings provide a way for further understanding the molecular basis in PRV pathogenesis.

Pseudorabies virus UL24 antagonizes OASL-mediated antiviral effect

Oligoadenylate synthetases-like (OASL) protein exerts various effects on DNA and RNA viruses by inhibiting cGAS-mediated IFN production and by enhancing RIG-I-mediated IFN induction, respectively. In this study, we aimed to examine the role of OASL in pseudorabies virus (PRV) proliferation and investigate the function of the PRV UL24 protein in cellular innate immunity. We found that OASL regulates PRV proliferation by enhancing RIG-I signaling. PRV infection decreased the expression of OASL at both the mRNA and protein levels in PK15 and HeLa cells. OASL expression suppressed the proliferation of PRV in a RIG-I-dependent manner and boosted RIG-I-mediated IFN expression as well as IFN-stimulated gene (ISG) induction. In contrast, knockdown of OASL enhanced PRV proliferation and reduced RIG-I signaling. However, the PRV UL24 protein was found to impair RIG-I signaling, thus inhibiting transcription of IFN and ISGs. In addition, the UL24 protein reduced RIG-I-induced expression of endogenous OASL in an IRF3-dependent manner, thereby antagonizing the OASL antiviral effect. Taken together, our findings characterize the role of OASL in PRV proliferation and provide new insights into the role of UL24 in PRV pathogenesis.

The full-length microRNA cluster in the intron of large latency transcript is associated with the virulence of pseudorabies virus

Pseudorabies virus (PRV), the etiological pathogen of Aujeszky's disease, belongs to the Alphaherpesvirus subfamily. Large latency transcript (LLT), the most abundant PRV transcript, harbors a ~ 4.6 kb microRNA (miRNA) cluster-encoding intron. To investigate the function of the LLT miRNA cluster during the life cycle of PRV, we generated a miRNA cluster mutation virus (PRV-∆miR cluster) and revertant virus. Analysis of the growth kinetics of PRV-ΔmiR cluster-infected cells revealed significantly smaller plaques and lower titers than the wild-type and revertant viruses. The mutation virus exhibited increased IE180 and decreased EP0 expression. The clinical symptoms observed in mice infected with PRV-ΔmiR cluster revealed that the miRNA cluster is involved in the pathogenesis of PRV. Physical parameters, virus shedding assays, and the SN50 titers revealed that the miRNA cluster enhances PRV virulence in pigs. Collectively, our findings suggest that the full-length miRNA cluster is involved in PRV replication and virulence.

Alpha/beta interferon receptor deficiency in mice significantly enhances susceptibility of the animals to pseudorabies virus infection

Pseudorabies virus, one of the neurotropic viruses, can infect numerous mammals. In particular, pseudorabies virus infection of swine occurs worldwide, and is a major threat to swine industry. However, the mechanism underlying the interaction between pseudorabies virus and host innate immune system is not fully understood. Here, we investigated the involvement of interferon α/β (IFN-α/β) receptor (IFNAR) in the pathogenesis of pseudorabies virus in a mouse model. The results showed that IFNAR-deficient (IFNAR−/−) mice were highly susceptible to the virus infection, as evidenced by markedly reduced survival rate of infected animals and increased viral replication. The expression of IFN-α/β and relevant interferon-stimulated genes in IFNAR−/− mice was significantly lower than that in wild-type (WT) littermates after the viral infection. Moreover, in response to the virus challenge, IFNAR−/− mice displayed elevated levels of inflammatory cytokines including interleukin 6 (IL-6) and IL-1β, and IFNAR−/− cells showed increased phosphorylation of STAT3. Collectively, these data reveal that the IFNAR−/− mice are more sensitive to pseudorabies virus infection than WT animals, and excessive IL-6/STAT3 response in IFNAR−/− mice may contribute to the pathogenesis. Our findings suggest that type I IFNs/IFNAR-dependent homeostatic control of the innate immunity is required for host defense against pseudorabies virus infection.

Suppression of apoptosis by pseudorabies virus Us3 protein kinase through the activation of PI3-K/Akt and NF-κB pathways

The pseudorabies virus (PRV) is a major viral disease that causes huge economic loss in the pig industry globally. Most viruses have been found to generate anti-apoptotic factors that facilitate cell survival in the early stages of infection. This study aimed to investigate the anti-apoptotic effects of PRV and study the underlying mechanisms in the early stage of infection. We investigated and compared whether the two PRV Us3 isoforms, Us3a and Us3b, could block apoptosis induced by virus infection, and further identified molecules involved in the signaling pathways. Our results demonstrated that PRV elicits 3-phosphoinositide dependent protein kinase-1/phosphatidylinositide 3-kinases/Akt (PDK-1/PI3-K/Akt)- and nuclear factor-κB (NF-κB)-dependent signaling in the early stage of infection. Inhibition of the PI3-K/Akt or NF-κB pathway enhanced cell death but no effect was observed on virus replication or PRV gene expression. Transiently-expressed GFP- or His-tagged PRV Us3a and Us3b cDNA protect cells against PRV-, avian reovirus- or bovine ephemeral fever virus-induced apoptosis in the cell lines. Us3a and Us3b transient over-expression upregulated several anti-apopototic signaling events, and the anti-apoptosis activity of Us3a is greater than that of Us3b. Kinase activity-deficient point or double point mutated Us3a lost the kinase activity of Us3a, which showed that kinase activity is required for the anti-apoptosis effect of Us3. Akt and NF-κB activation still occurred in UV-inactivated PRV- and cycloheximide-treated cells. In vivo study showed that PRV-infected trigeminal ganglion increases the expression of anti-apoptosis signaling molecules, including Akt, PDK-1 and IκBα, which is a similar result to that seen in the in vitro experiments. Our study suggests that signaling mechanisms may play important roles in PRV pathogenesis.

Glycoprotein G from pseudorabies virus binds to chemokines with high affinity and inhibits their function

Pseudorabies virus (PRV), also known as suid herpesvirus, is the aetiological agent of Aujeszky's disease in swine. In other animals, except higher-order primates, PRV infection is often fatal. The mechanisms of PRV pathogenesis and immune modulation are largely unknown. PRV codes for 11 glycoproteins. Among them, glycoprotein G (gG) is the most abundant PRV protein found in the supernatant of PRV-infected cell cultures. PRV-gG has low amino acid sequence similarity with gG from other animal alphaherpesviruses and its function is unknown. gG from other animal alphaherpesviruses, with the exception of at least equine herpesvirus 4, binds to chemokines. We show here that PRV-gG binds to the human chemokine CL1 and several CC and CXC human chemokines with high affinity. Chemokine-binding activity can be detected in the supernatants of PRV-infected cell cultures, and insertional inactivation of the gene encoding gG from the PRV genome results in loss of chemokine-binding activity. Binding of PRV-gG to chemokines inhibits chemokine-mediated cell migration, suggesting a role for PRV-gG in immune evasion.

Infection of the mammalian nervous system by pseudorabies virus (PRV)

Pseudorabies virus (PRV) is an alphaherpesvirus that causes a disease of economic impact in swine. Studies on the molecular biology and pathogenesis of PRV are well advanced. PRV has a striking neurotropism and can establish latent infections in the peripheral and central nervous system. Many parallels exist between PRV pathogenesis in animals and the neurotropic human herpesviruses. Since work can be done with the natural host, model systems can be evaluated directly—something difficult, if not impossible, to do with the human viruses. This review focuses on the ability of PRV to infect the mammalian nervous system, with a specific emphasis on transneuronal spread, the host response to neuronal infection and latency.

The influence of porcine recombinant interferon- 1 on pseudorabies virus infection of porcine nasal mucosa in vitro

To determine the effect of interferon (IFN) on the pathogenesis of pseudorabies virus (PRV), porcine nasal mucosal explants were first treated with recombinant porcine methionyl-IFN-alpha 1 and then infected with one of three strains of PRV. The stroma of treated mucosal explants were protected against infection with virulent PRV or PRV of intermediate virulence because the infection was restricted to the epithelial cells. In contrast, untreated mucosal explants were readily infected by virulent PRV or PRV of intermediate virulence; the infection spread from epithelial cells to stromal fibroblasts. Avirulent PRV infection was restricted to the epithelial cells of treated and untreated mucosal explants. IFN treatment limited the extent of all three PRV infections in the epithelial cells. Cultured porcine fibroblasts and porcine kidney cells were also treated with IFN and subsequently infected with PRV; infection was prevented in most porcine fibroblasts and the virus yield from porcine kidney cells was reduced. Budding of virulent PRV nucleocapsids through the inner nuclear membrane was observed more frequently in treated than in untreated mucosal explants were enveloped virus particles accumulated between the inner and outer nuclear membranes, indicating that the membrane-associated events of PRV replication had been affected. We conclude that IFN-alpha protects stromal fibroblasts against PRV infection and reduces virus replication in epithelial cells.