Herpes simplex virus type 1 infection stimulates p38/c-Jun N-terminal mitogen-activated protein kinase pathways and activates transcription factor AP-1

A viral E3 ubiquitin ligase produced by herpes simplex virus 1 inhibits the NLRP1 inflammasome

Guard proteins initiate defense mechanisms upon sensing pathogen-encoded virulence factors. Successful viral pathogens likely inhibit guard protein activity, but these interactions have been largely undefined. Here, we demonstrate that the human pathogen herpes simplex virus 1 (HSV-1) stimulates and inhibits an antiviral pathway initiated by NLRP1, a guard protein that induces inflammasome formation and pyroptotic cell death when activated. Notably, HSV-1 infection of human keratinocytes promotes posttranslational modifications to NLRP1, consistent with MAPK-dependent NLRP1 activation, but does not result in downstream inflammasome formation. We identify infected cell protein 0 (ICP0) as the critical HSV-1 protein that is necessary and sufficient for inhibition of the NLRP1 pathway. Mechanistically, ICP0's cytoplasmic localization and function as an E3 ubiquitin ligase prevents proteasomal degradation of the auto-inhibitory NT-NLRP1 fragment, thereby preventing inflammasome formation. Further, we demonstrate that inhibiting this inflammasome is important for promoting HSV-1 replication. Thus, we have established a mechanism by which HSV-1 overcomes a guard-mediated antiviral defense strategy in humans.

Multimodal Therapy Approaches for NUT Carcinoma by Dual Combination of Oncolytic Virus Talimogene Laherparepvec with Small Molecule Inhibitors

NUT (nuclear-protein-in-testis) carcinoma (NC) is a highly aggressive tumor disease. Given that current treatment regimens offer a median survival of six months only, it is likely that this type of tumor requires an extended multimodal treatment approach to improve prognosis. In an earlier case report, we could show that an oncolytic herpes simplex virus (T-VEC) is functional in NC patients. To identify further combination partners for T-VEC, we have investigated the anti-tumoral effects of T-VEC and five different small molecule inhibitors (SMIs) alone and in combination in human NC cell lines. Dual combinations were found to result in higher rates of tumor cell reductions when compared to the respective monotherapy as demonstrated by viability assays and real-time tumor cell growth monitoring. Interestingly, we found that the combination of T-VEC with SMIs resulted in both stronger and earlier reductions in the expression of c-Myc, a main driver of NC cell proliferation, when compared to T-VEC monotherapy. These results indicate the great potential of combinatorial therapies using oncolytic viruses and SMIs to control the highly aggressive behavior of NC cancers and probably will pave the way for innovative multimodal clinical studies in the near future.

c-Jun signaling during initial HSV-1 infection modulates latency to enhance later reactivation in addition to directly promoting the progression to full reactivation

Herpes simplex virus-1 (HSV-1) establishes a latent infection in peripheral neurons and periodically reactivates to permit transmission, which can result in clinical manifestations. Viral transactivators required for lytic infection are largely absent during latent infection, and therefore, HSV-1 relies on the co-option of neuronal host signaling pathways to initiate its gene expression. The activation of the neuronal c-Jun N-terminal kinase (JNK) cell stress pathway is central to initiating biphasic reactivation in response to multiple stimuli. However, how host factors work with JNK to stimulate the initial wave of gene expression (known as Phase I) or the progression to full Phase II reactivation remains unclear. Here, we found that c-Jun, the primary target downstream of neuronal JNK cell stress signaling, functions during reactivation but not during the JNK-mediated initiation of Phase I gene expression. Instead, c-Jun was required to transition from Phase I to full HSV-1 reactivation and was detected in viral replication compartments of reactivating neurons. Interestingly, we also identified a role for both c-Jun and enhanced neuronal stress during initial neuronal infection in promoting a more reactivation-competent form of HSV-1 latency. Therefore, c-Jun functions at multiple stages during the HSV latent infection of neurons to promote reactivation but not during the initial JNK-dependent Phase I. Importantly, by demonstrating that initial infection conditions can contribute to later reactivation abilities, this study highlights the potential for latently infected neurons to maintain a molecular scar of previous exposure to neuronal stressors.IMPORTANCEThe molecular mechanisms that regulate the reactivation of herpes simplex virus-1 (HSV-1) from latent infection are unknown. The host transcription and pioneer factor c-Jun is the main target of the JNK cell stress pathway that is known to be important in exit of HSV from latency. Surprisingly, we found that c-Jun does not act with JNK during exit from latency but instead promotes the transition to full reactivation. Moreover, c-Jun and enhanced neuronal stress during initial neuronal infection promoted a more reactivation-competent form of HSV-1 latency. c-Jun, therefore, functions at multiple stages during HSV-1 latent infection of neurons to promote reactivation. Importantly, this study contributes to a growing body of evidence that de novo HSV-1 infection conditions can modulate latent infection and impact future reactivation events, raising important questions on the clinical impact of stress during initial HSV-1 acquisition on future reactivation events and consequences.

c-Jun Signaling During Initial HSV-1 Infection Modulates Latency to Enhance Later Reactivation in addition to Directly Promoting the Progression to Full Reactivation

Herpes simplex virus-1 (HSV-1) establishes a latent infection in peripheral neurons and can periodically reactivate to permit transmission and clinical manifestations. Viral transactivators required for lytic infection are largely absent during latent infection and therefore HSV-1 relies on the co-option of neuronal host signaling pathways to initiate its gene expression. Activation of the neuronal c-Jun N-terminal kinase (JNK) cell stress pathway is central to initiating biphasic reactivation in response to multiple stimuli. However, how host factors work with JNK to stimulate the initial wave of gene expression (known as Phase I) or the progression to full, Phase II reactivation remains unclear. Here, we found that c-Jun, the primary target downstream of neuronal JNK cell stress signaling, functions during reactivation but not during the JNK-mediated initiation of Phase I gene expression. Instead, c-Jun was required for the transition from Phase I to full HSV-1 reactivation and was detected in viral replication compartments of reactivating neurons. Interestingly, we also identified a role for both c-Jun and enhanced neuronal stress during initial neuronal infection in promoting a more reactivation-competent form of HSV-1 latency. Therefore, c-Jun functions at multiple stages during HSV latent infection of neurons to promote reactivation. Importantly, by demonstrating that initial infection conditions can contribute to later reactivation abilities, this study highlights the potential for latently infected neurons to maintain a molecular scar of previous exposure to neuronal stressors.

HSV-1 Infection Induces a Downstream Shift of Promoter-Proximal Pausing for Host Genes

Herpes simplex virus 1 (HSV-1) infection exerts a profound shutoff of host gene expression at multiple levels. Recently, HSV-1 infection was reported to also impact promoter-proximal RNA polymerase II (Pol II) pausing, a key step in the eukaryotic transcription cycle, with decreased and increased Pol II pausing observed for activated and repressed genes, respectively. Here, we demonstrate that HSV-1 infection induces more complex alterations in promoter-proximal pausing than previously suspected for the vast majority of cellular genes. While pausing is generally retained, it is shifted to more downstream and less well-positioned sites for most host genes. The downstream shift of Pol II pausing was established between 1.5 and 3 h of infection, remained stable until at least 6 hours postinfection, and was observed in the absence of ICP22. The shift in Pol II pausing does not result from alternative de novo transcription initiation at downstream sites or read-in transcription originating from disruption of transcription termination of upstream genes. The use of downstream secondary pause sites associated with +1 nucleosomes was previously observed upon negative elongation factor (NELF) depletion. However, downstream shifts of Pol II pausing in HSV-1 infection were much more pronounced than observed upon NELF depletion. Thus, our study reveals a novel aspect in which HSV-1 infection fundamentally reshapes host transcriptional processes, providing new insights into the regulation of promoter-proximal Pol II pausing in eukaryotic cells. IMPORTANCE This study provides a genome-wide analysis of changes in promoter-proximal polymerase II (Pol II) pausing on host genes induced by HSV-1 infection. It shows that standard measures of pausing, i.e., pausing indices, do not properly capture the complex and unsuspected alterations in Pol II pausing occurring in HSV-1 infection. Instead of a reduction of pausing with increased elongation, as suggested by pausing index analysis, HSV-1 infection leads to a shift of pausing to downstream and less well-positioned sites than in uninfected cells for the majority of host genes. Thus, HSV-1 infection fundamentally reshapes a key regulatory step at the beginning of the host transcriptional cycle on a genome-wide scale.

Resistance evolution against host-directed antiviral agents: Buffalopox virus switches to use p38-ϒ under long-term selective pressure of an inhibitor targeting p38-α

Host-dependency factors have increasingly been targeted to minimize antiviral drug resistance. In this study, we have demonstrated that inhibition of p38 mitogen-activated protein kinase (a cellular protein) suppresses buffalopox virus (BPXV) protein synthesis by targeting p38-MNK1-eIF4E signaling pathway. In order to provide insights into the evolution of drug resistance, we selected resistant mutants by long-term sequential passages (P; n = 60) in the presence of p38 inhibitor (SB239063). The P60-SB239063 virus exhibited significant resistance to SB239063 as compared to the P60-Control virus. To provide mechanistic insights on the acquisition of resistance by BPXV-P60-SB239063, we generated p38-α and p38-ϒ (isoforms of p38) knockout Vero cells by CRISPR/Cas9-mediated genome editing. It was demonstrated that unlike the wild type (WT) virus which is dependent on p38-α isoform, the resistant virus (BPXV-P60-SB239063) switches over to use p38-ϒ so as to efficiently replicate in the target cells. This is a rare evidence wherein a virus was shown to bypass the dependency on a critical cellular factor under selective pressure of a drug.

Phospho-proteomics identifies a critical role of ATF2 in pseudorabies virus replication

Pseudorabies virus (PRV), an etiological agent of pseudorabies in livestock, has negatively affected the porcine industry all over the world. Epithelial cells are reported as the first site of PRV infection. However, the role of host proteins and its related signaling pathways in PRV replication is largely unclear. In this study, we performed a quantitative phosphoproteomics screening on PRV-infected porcine kidney (PK-15) epithelial cells. Totally 5723 phosphopeptides, corresponding to 2180 proteins, were obtained, and the phosphorylated states of 810 proteins were significantly different in PRV-infected cells compared with mock-infected cells (P ​< ​0.05). GO and KEGG analysis revealed that these differentially expressed phosphorylated proteins were predominantly related to RNA transport and MAPK signaling pathways. Further functional studies of NF-κB, transcription activator factor-2 (ATF2), MAX and SOS genes in MAPK signaling pathway were analyzed using RNA interference (RNAi) knockdown. It showed that only ATF2-knockdown reduces both PRV titer and viral genome copy number. JNK pathway inhibition and CRISPR/Cas9 gene knockout showed that ATF2 was required for the effective replication of PRV, especially during the biogenesis of viral genome DNA. Subsequently, by overexpression of the ATF2 gene and point mutation of the amino acid positions 69/71 of ATF2, it was further demonstrated that the phosphorylation of ATF2 promoted PRV replication. These findings suggest that ATF2 may provide potential therapeutic target for inhibiting PRV infection.

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Phosphoproteomic profiling of PRV-infected PK-15 ​cells with iTRAQ-quantification.

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JNK pathway regulates ATF2 phosphorylation and PRV replication.

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Phosphorylation of ATF2 promotes PRV replication.

p38 activation and viral infection

Viruses completely rely on the energy and metabolic systems of host cells for life activities. Viral infections usually lead to cytopathic effects and host diseases. To date, there are still no specific clinical vaccines or drugs against most viral infections. Therefore, understanding the molecular and cellular mechanisms of viral infections is of great significance to prevent and treat viral diseases. A variety of viral infections are related to the p38 MAPK signalling pathway, and p38 is an important host factor in virus-infected cells. Here, we introduce the different signalling pathways of p38 activation and then summarise how different viruses induce p38 phosphorylation. Finally, we provide a general summary of the effect of p38 activation on virus replication. Our review provides integrated data on p38 activation and viral infections and describes the potential application of targeting p38 as an antiviral strategy.

The novel ORFV protein ORFV113 activates LPA-p38 signaling

Viruses have evolved mechanisms to subvert critical cellular signaling pathways that regulate a wide range of cellular functions, including cell differentiation, proliferation and chemotaxis, and innate immune responses. Here, we describe a novel ORFV protein, ORFV113, that interacts with the G protein-coupled receptor Lysophosphatidic acid receptor 1 (LPA1). Consistent with its interaction with LPA1, ORFV113 enhances p38 kinase phosphorylation in ORFV infected cells in vitro and in vivo, and in cells transiently expressing ORFV113 or treated with soluble ORFV113. Infection of cells with virus lacking ORFV113 (OV-IA82Δ113) significantly decreased p38 phosphorylation and viral plaque size. Infection of cells with ORFV in the presence of a p38 kinase inhibitor markedly diminished ORFV replication, highlighting importance of p38 signaling during ORFV infection. ORFV113 enhancement of p38 activation was prevented in cells in which LPA1 expression was knocked down and in cells treated with LPA1 inhibitor. Infection of sheep with OV-IA82Δ113 led to a strikingly attenuated disease phenotype, indicating that ORFV113 is a major virulence determinant in the natural host. Notably, ORFV113 represents the first viral protein that modulates p38 signaling via interaction with LPA1 receptor.

The Roles of c-Jun N-Terminal Kinase (JNK) in Infectious Diseases

c-Jun N-terminal kinases (JNKs) are among the most crucial mitogen-activated protein kinases (MAPKs) and regulate various cellular processes, including cell proliferation, apoptosis, autophagy, and inflammation. Microbes heavily rely on cellular signaling pathways for their effective replication; hence, JNKs may play important roles in infectious diseases. In this review, we describe the basic signaling properties of MAPKs and JNKs in apoptosis, autophagy, and inflammasome activation. Furthermore, we discuss the roles of JNKs in various infectious diseases induced by viruses, bacteria, fungi, and parasites, as well as their potential to serve as targets for the development of therapeutic agents for infectious diseases. We expect this review to expand our understanding of the JNK signaling pathway’s role in infectious diseases and provide important clues for the prevention and treatment of infectious diseases.

Importance of experimental information (metadata) for archived sequence data: case of specific gene bias due to lag time between sample harvest and RNA protection in RNA sequencing

Large volumes of high-throughput sequencing data have been submitted to the Sequencing Read Archive (SRA). The lack of experimental metadata associated with the data makes reuse and understanding data quality very difficult. In the case of RNA sequencing (RNA-Seq), which reveals the presence and quantity of RNA in a biological sample at any moment, it is necessary to consider that gene expression responds over a short time interval (several seconds to a few minutes) in many organisms. Therefore, to isolate RNA that accurately reflects the transcriptome at the point of harvest, raw biological samples should be processed by freezing in liquid nitrogen, immersing in RNA stabilization reagent or lysing and homogenizing in RNA lysis buffer containing guanidine thiocyanate as soon as possible. As the number of samples handled simultaneously increases, the time until the RNA is protected can increase. Here, to evaluate the effect of different lag times in RNA protection on RNA-Seq data, we harvested CHO-S cells after 3, 5, 6, and 7 days of cultivation, added RNA lysis buffer in a time course of 15, 30, 45, and 60 min after harvest, and conducted RNA-Seq. These RNA samples showed high RNA integrity number (RIN) values indicating non-degraded RNA, and sequence data from libraries prepared with these RNA samples was of high quality according to FastQC. We observed that, at the same cultivation day, global trends of gene expression were similar across the time course of addition of RNA lysis buffer; however, the expression of some genes was significantly different between the time-course samples of the same cultivation day; most of these differentially expressed genes were related to apoptosis. We conclude that the time lag between sample harvest and RNA protection influences gene expression of specific genes. It is, therefore, necessary to know not only RIN values of RNA and the quality of the sequence data but also how the experiment was performed when acquiring RNA-Seq data from the database.

Engagement of Neurotropic Viruses in Fast Axonal Transport: Mechanisms, Potential Role of Host Kinases and Implications for Neuronal Dysfunction

Much remains unknown about mechanisms sustaining the various stages in the life cycle of neurotropic viruses. An understanding of those mechanisms operating before their replication and propagation could advance the development of effective anti-viral strategies. Here, we review our current knowledge of strategies used by neurotropic viruses to undergo bidirectional movement along axons. We discuss how the invasion strategies used by specific viruses might influence their mode of interaction with selected components of the host’s fast axonal transport (FAT) machinery, including specialized membrane-bounded organelles and microtubule-based motor proteins. As part of this discussion, we provide a critical evaluation of various reported interactions among viral and motor proteins and highlight limitations of some in vitro approaches that led to their identification. Based on a large body of evidence documenting activation of host kinases by neurotropic viruses, and on recent work revealing regulation of FAT through phosphorylation-based mechanisms, we posit a potential role of host kinases on the engagement of viruses in retrograde FAT. Finally, we briefly describe recent evidence linking aberrant activation of kinase pathways to deficits in FAT and neuronal degeneration in the context of human neurodegenerative diseases. Based on these findings, we speculate that neurotoxicity elicited by viral infection may involve deregulation of host kinases involved in the regulation of FAT and other cellular processes sustaining neuronal function and survival.

Cellular and Viral Determinants of HSV-1 Entry and Intracellular Transport towards Nucleus of Infected Cells

HSV-1 employs cellular motor proteins and modulates kinase pathways to facilitate intracellular virion capsid transport. Previously, we and others have shown that the Akt inhibitor miltefosine inhibited virus entry. Herein, we show that the protein kinase C inhibitors staurosporine (STS) and gouml inhibited HSV-1 entry into Vero cells, and that miltefosine prevents HSV-1 capsid transport toward the nucleus. We have reported that the HSV-1 UL37 tegument protein interacts with the dynein motor complex during virus entry and virion egress, while others have shown that the UL37/UL36 protein complex binds dynein and kinesin causing a saltatory movement of capsids in neuronal axons. Co-immoprecipitation experiments confirmed previous findings from our laboratory that the UL37 protein interacted with the dynein intermediate chain (DIC) at early times post infection. This UL37-DIC interaction was concurrent with DIC phosphorylation in infected, but not mock-infected cells. Miltefosine inhibited dynein phosphorylation when added before, but not after virus entry. Inhibition of motor accessory protein dynactins (DCTN2, DCTN3), the adaptor proteins EB1 and the Bicaudal D homolog 2 (BICD2) expression using lentiviruses expressing specific shRNAs, inhibited intracellular transport of virion capsids toward the nucleus of human neuroblastoma (SK-N-SH) cells. Co-immunoprecipitation experiments revealed that the major capsid protein Vp5 interacted with dynactins (DCTN1/p150 and DCTN4/p62) and the end-binding protein (EB1) at early times post infection. These results show that Akt and kinase C are involved in virus entry and intracellular transport of virion capsids, but not in dynein activation via phosphorylation. Importantly, both the UL37 and Vp5 viral proteins are involved in dynein-dependent transport of virion capsids to the nuclei of infected cells.Importance. Herpes simplex virus type-1 enter either via fusion at the plasma membranes or endocytosis depositing the virion capsids into the cytoplasm of infected cells. The viral capsids utilize the dynein motor complex to move toward the nuclei of infected cells using the microtubular network. This work shows that inhibitors of the Akt kinase and kinase C inhibit not only viral entry into cells but also virion capsid transport toward the nucleus. In addition, the work reveals that the virion protein ICP5 (VP5) interacts with the dynein cofactor dynactin, while the UL37 protein interacts with the dynein intermediate chain (DIC). Importantly, neither Akt nor Kinase C was found to be responsible for phosphorylation/activation of dynein indicating that other cellular or viral kinases may be involved.

Effects of epigallocatechin-3-gallate and acyclovir on herpes simplex virus type 1 infection in oral epithelial cells

BACKGROUND/PURPOSE

Herpes simplex virus type 1 (HSV-1) is the pathogenic agent of human diseases, including gingivostomatitis and herpes labialis. The anti-viral activities of the tea polyphenol, epigallocatechin-3-gallate (EGCG), have been demonstrated. This study examined the combined effects of EGCG and the antiviral drug, acyclovir (ACV), on infection of HSV-1 in oral epithelial cells.

METHODS

Cell viability was examined using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide. Viral yields were determined using the plaque assay. Viral proteins were detected using Western blotting analysis or confocal laser scanning microscopy. Viral DNA was detected using the real-time polymerase chain reaction.

RESULTS

Cytotoxic effects of HSV-1 on the viability of oral epithelial cells were evidently reduced in the presence of EGCG (25 μg/ml) or/and ACV (50 μg/ml). Viral yields were also significantly reduced by treatment of cells with EGCG or/and ACV. Expression of viral immediate early protein, infected cell protein 0 (ICP0), was greatly inhibited when cells were treated with EGCG. Combined effects of EGCG and ACV were more evident for the expression of viral thymidine kinase, ICP5 and glycoprotein D. EGCG, but not ACV, significantly reduced the levels of viral particles and viral DNA during viral entry phase. However, at 20 h post infection, the intracellular viral DNA was evidently reduced in HSV-1 infected cells treated with EGCG and ACV. Moreover, the stimulatory effects of HSV-1 on phosphorylation of c-Jun N-terminal kinase could be reduced by ACV.

CONCLUSION

The results demonstrated the additive effects of EGCG and ACV on HSV-1 infection in oral epithelial cells.

TUDCA inhibits HSV-1 replication by the modulating unfolded protein response pathway

Tauroursodeoxycholic acid (TUDCA), an endogenous bile acid, was used to protect liver function through antiapoptosis or reducing endoplasmic reticulum stress (ER stress). Previous studies showed that ER stress was modulated by herpes simplex virus types 1 (HSV-1) infection to facilitate viral replication. Here, we investigated the effect of TUDCA on HSV-1 infection of HEC-1-A cells and showed that both replication and multiplication of the virus were inhibited by TUDCA in a dose dependent manner. Unfolded protein response was induced to deliver stress signals from ER to nucleus. We found that TUDCA alleviated activating transcription factor 6 branch inhibition, partially enhanced protein kinase RNA-like ER kinase pathway activation, and repressed inositol-requiring protein 1α arm activation significantly in infected cells. The findings of this study suggest that TUDCA inhibits HSV-1 replication through ER stress pathway, which may provide a potential therapeutic strategy for HSV-1 infection.

Implications of TORCH Diseases in Retinal Development-Special Focus on Congenital Toxoplasmosis

There are certain critical periods during pregnancy when the fetus is at high risk for exposure to teratogens. Some microorganisms, including Toxoplasma gondii, are known to exhibit teratogenic effects, interfering with fetal development and causing irreversible disturbances. T. gondii is an obligate intracellular parasite and the etiological agent of Toxoplasmosis, a zoonosis that affects one third of the world's population. Although congenital infection can cause severe fetal damage, the injury extension depends on the gestational period of infection, among other factors, like parasite genotype and host immunity. This parasite invades the Central Nervous System (CNS), forming tissue cysts, and can interfere with neurodevelopment, leading to frequent neurological abnormalities associated with T. gondii infection. Therefore, T. gondii is included in the TORCH complex of infectious diseases that may lead to neurological malformations (Toxoplasmosis, Others, Rubella, Cytomegalovirus, and Herpes). The retina is part of CNS, as it is derived from the diencephalon. Except for astrocytes and microglia, retinal cells originate from multipotent neural progenitors. After cell cycle exit, cells migrate to specific layers, undergo morphological and neurochemical differentiation, form synapses and establish their circuits. The retina is organized in nuclear layers intercalated by plexus, responsible for translating and preprocessing light stimuli and for sending this information to the brain visual nuclei for image perception. Ocular toxoplasmosis (OT) is a very debilitating condition and may present high severity in areas in which virulent strains are found. However, little is known about the effect of congenital infection on the biology of retinal progenitors/ immature cells and how this infection may affect the development of this tissue. In this context, this study reviews the effects that congenital infections may cause to the developing retina and the cellular and molecular aspects of these diseases, with special focus on congenital OT.

Wogonin inhibits in vitro herpes simplex virus type 1 and 2 infection by modulating cellular NF-κB and MAPK pathways

BACKGROUND

Wogonin, a natural flavonoid-like chemical compound, exhibits anti-inflammatory, antitumor, antiviral, neuroprotective, and anxiolytic effects by modulating a variety of cellular signaling pathways including PI3K-Akt, p53, nuclear factor κB (NF-κB), mitogen-activated protein kinase (MAPK) pathways. In this study, its antiviral effect against herpes simplex virus (HSV) type 1 and 2 (HSV-1 and HSV-2) replication was investigated.

RESULTS

Wogonin suppressed HSV-2-induced cytopathic effect (CPE) and reduced viral mRNA transcription, viral protein synthesis, and infectious virion particle titers in a dose-dependent manner. A time-of-drug-addition assay demonstrated that wogonin acted as a postentry viral inhibitor. Wogonin also significantly reduced HSV-induced NF-κB and MAPK pathway activation, which has previously been demonstrated to be important for viral replication.

CONCLUSIONS

Our results suggest that the anti-herpes effect of wogonin may be mediated by modulation of cellular NF-κB and JNK/p38 MAPK pathways and imply that wogonin may be useful as an anti-HSV agent.

The AP-1 pathway; A key regulator of cellular transformation modulated by oncogenic viruses

Cancer progression is critically associated with modulation of host cell signaling pathways. Activator protein-1 (AP-1) signaling is one such pathway whose deregulation renders the host more susceptible to cancer development. Oncogenic viruses, including hepatitis B virus, hepatitis C virus, human papilloma virus, Epstein-Barr virus, human T-cell lymphotropic virus type 1, and Kaposi's sarcoma-associated herpes virus, are common causes of cancer. This review discusses how these oncoviruses by acting through various aspects of the host cell signaling machinery such as the AP-1 pathway might affect oncoviral tumorigenesis, replication, and pathogenesis. The review also briefly considers how the pathway might be targeted during infections with these oncogenic viruses.

Herpes Simplex Virus 1 Infection Promotes the Growth of a Subpopulation of Tumor Cells in Three-Dimensional Uveal Melanoma Cultures

Cancer cells are exposed to HSV-1 during oncolytic virotherapy with the intention of killing tumor cells. Our observations reported here suggest that potential dangers of HSV-1 oncolytic therapy include promotion of growth of some tumor cells. Furthermore, our findings raise the possibility that HSV-1 infection of neoplastic cells during natural infections or vaccinations may promote the growth of tumors. Our study indicates that HSV-1 infection of 3D tumor cell cultures provides an experimental platform in which mechanisms of HSV-1-mediated promotion of tumor cell growth can be effectively studied.

Herpes simplex virus 1 (HSV-1)-mediated oncolytic therapy is an emerging cancer treatment modality with potential effectiveness against a variety of malignancies. To better understand the interaction of HSV-1 with neoplastic cells, we inoculated three-dimensional (3D) cultures of human uveal melanoma cells with HSV-1. 3D melanoma cultures were established by placing tumor cells on the surface of a Matrigel matrix, which was followed by the growth of tumor cells on the matrix surface and invasion of the Matrigel matrix by some tumor cells to form multicellular tumor spheroids within the matrix. When established 3D melanoma cultures were inoculated with HSV-1 by placing virus on the surface of cultures, virus infection caused extensive death of melanoma cells growing on the surface of the 3D matrix and significantly decreased the number of tumor cell spheroids within the matrix. However, HSV-1 infection did not lead to a complete destruction of tumor cells in the 3D cultures during a 17-day observation period and, surprisingly, HSV-1 infection promoted the growth of some melanoma cells within the matrix as determined by the significantly increased size of residual viable multicellular tumor spheroids in virus-inoculated 3D cultures at 17 days after virus inoculation. Acyclovir treatment inhibited HSV-1-induced tumor cell killing but did not block the virus infection-induced increase in spheroid size. These findings suggest that although HSV-1 oncolytic virotherapy may cause extensive tumor cell killing, it may also be associated with the unintended promotion of the growth of some tumor cells.

IMPORTANCE Cancer cells are exposed to HSV-1 during oncolytic virotherapy with the intention of killing tumor cells. Our observations reported here suggest that potential dangers of HSV-1 oncolytic therapy include promotion of growth of some tumor cells. Furthermore, our findings raise the possibility that HSV-1 infection of neoplastic cells during natural infections or vaccinations may promote the growth of tumors. Our study indicates that HSV-1 infection of 3D tumor cell cultures provides an experimental platform in which mechanisms of HSV-1-mediated promotion of tumor cell growth can be effectively studied.

Programmed cell death: the battlefield between the host and alpha-herpesviruses and a potential avenue for cancer treatment

Programed cell death is an antiviral mechanism by which the host limits viral replication and protects uninfected cells. Many viruses encode proteins resistant to programed cell death to escape the host immune defenses, which indicates that programed cell death is more favorable for the host immune defense. Alpha-herpesviruses are pathogens that widely affect the health of humans and animals in different communities worldwide. Alpha-herpesviruses can induce apoptosis, autophagy and necroptosis through different molecular mechanisms. This review concisely illustrates the different pathways of apoptosis, autophagy, and necroptosis induced by alpha-herpesviruses. These pathways influence viral infection and replication and are a potential avenue for cancer treatment. This review will increase our understanding of the role of programed cell death in the host immune defense and provides new possibilities for cancer treatment.

NFκB-mediated activation of the cellular FUT3, 5 and 6 gene cluster by herpes simplex virus type 1

Herpes simplex virus type 1 has the ability to induce expression of a human gene cluster located on chromosome 19 upon infection. This gene cluster contains three fucosyltransferases (encoded by FUT3, FUT5 and FUT6) with the ability to add a fucose to an N-acetylglucosamine residue. Little is known regarding the transcriptional activation of these three genes in human cells. Intriguingly, herpes simplex virus type 1 activates all three genes simultaneously during infection, a situation not observed in uninfected tissue, pointing towards a virus specific mechanism for transcriptional activation. The aim of this study was to define the underlying mechanism for the herpes simplex virus type 1 activation of FUT3, FUT5 and FUT6 transcription. The transcriptional activation of the FUT-gene cluster on chromosome 19 in fibroblasts was specific, not involving adjacent genes. Moreover, inhibition of NFκB signaling through panepoxydone treatment significantly decreased the induction of FUT3, FUT5 and FUT6 transcriptional activation, as did siRNA targeting of p65, in herpes simplex virus type 1 infected fibroblasts. NFκB and p65 signaling appears to play an important role in the regulation of FUT3, FUT5 and FUT6 transcriptional activation by herpes simplex virus type 1 although additional, unidentified, viral factors might account for part of the mechanism as direct interferon mediated stimulation of NFκB was not sufficient to induce the fucosyltransferase encoding gene cluster in uninfected cells.

Widespread activation of antisense transcription of the host genome during herpes simplex virus 1 infection

Background

Herpesviruses can infect a wide range of animal species. Herpes simplex virus 1 (HSV-1) is one of the eight herpesviruses that can infect humans and is prevalent worldwide. Herpesviruses have evolved multiple ways to adapt the infected cells to their needs, but knowledge about these transcriptional and post-transcriptional modifications is sparse.

Results

Here, we show that HSV-1 induces the expression of about 1000 antisense transcripts from the human host cell genome. A subset of these is also activated by the closely related varicella zoster virus. Antisense transcripts originate either at gene promoters or within the gene body, and they show different susceptibility to the inhibition of early and immediate early viral gene expression. Overexpression of the major viral transcription factor ICP4 is sufficient to turn on a subset of antisense transcripts. Histone marks around transcription start sites of HSV-1-induced and constitutively transcribed antisense transcripts are highly similar, indicating that the genetic loci are already poised to transcribe these novel RNAs. Furthermore, an antisense transcript overlapping with the BBC3 gene (also known as PUMA) transcriptionally silences this potent inducer of apoptosis in cis.

Conclusions

We show for the first time that a virus induces widespread antisense transcription of the host cell genome. We provide evidence that HSV-1 uses this to downregulate a strong inducer of apoptosis. Our findings open new perspectives on global and specific alterations of host cell transcription by viruses.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-017-1329-5) contains supplementary material, which is available to authorized users.

Opposite Roles of RNase and Kinase Activities of Inositol-Requiring Enzyme 1 (IRE1) on HSV-1 Replication

In response to the endoplasmic reticulum (ER) stress induced by herpes simplex virus type 1 (HSV-1) infection, host cells activate the unfolded protein response (UPR) to reduce the protein-folding burden in the ER. The regulation of UPR upon HSV-1 infection is complex, and the downstream effectors can be detrimental to viral replication. Therefore, HSV-1 copes with the UPR to create a beneficial environment for its replication. UPR has three branches, including protein kinase RNA (PKR)-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1), and activated transcription factor 6 (ATF6). IRE1α is the most conserved branch of UPR which has both RNase and kinase activities. Previous studies have shown that IRE1α RNase activity was inactivated during HSV-1 infection. However, the effect of the two activities of IRE1α on HSV-1 replication remains unknown. Results in this study showed that IRE1α expression was up-regulated during HSV-1 infection. We found that in HEC-1-A cells, increasing RNase activity, or inhibiting kinase activity of IRE1α led to viral suppression, indicating that the kinase activity of IRE1α was beneficial, while the RNase activity was detrimental to viral replication. Further evidence showed that the kinase activity of IRE1α leads to the activation of the JNK (c-Jun N-terminal kinases) pathway, which enhances viral replication. Taken together, our evidence suggests that IRE1α is involved in HSV-1 replication, and its RNase and kinase activities play differential roles during viral infection.

Role of the JNK Pathway in Varicella-Zoster Virus Lytic Infection and Reactivation

Mechanisms of neuronal infection by varicella-zoster virus (VZV) have been challenging to study due to the relatively strict human tropism of the virus and the paucity of tractable experimental models. Cellular mitogen-activated protein kinases (MAPKs) have been shown to play a role in VZV infection of nonneuronal cells, with distinct consequences for infectivity in different cell types. Here, we utilize several human neuronal culture systems to investigate the role of one such MAPK, the c-Jun N-terminal kinase (JNK), in VZV lytic infection and reactivation. We find that the JNK pathway is specifically activated following infection of human embryonic stem cell-derived neurons and that this activation of JNK is essential for efficient viral protein expression and replication. Inhibition of the JNK pathway blocked viral replication in a manner distinct from that of acyclovir, and an acyclovir-resistant VZV isolate was as sensitive to the effects of JNK inhibition as an acyclovir-sensitive VZV isolate in neurons. Moreover, in a microfluidic-based human neuronal model of viral latency and reactivation, we found that inhibition of the JNK pathway resulted in a marked reduction in reactivation of VZV. Finally, we utilized a novel technique to efficiently generate cells expressing markers of human sensory neurons from neural crest cells and established a critical role for the JNK pathway in infection of these cells. In summary, the JNK pathway plays an important role in lytic infection and reactivation of VZV in physiologically relevant cell types and may provide an alternative target for antiviral therapy.IMPORTANCE Varicella-zoster virus (VZV) has infected over 90% of people worldwide. While primary infection leads to the typically self-limiting condition of chickenpox, the virus can remain dormant in the nervous system and may reactivate later in life, leading to shingles or inflammatory diseases of the nervous system and eye with potentially severe consequences. Here, we take advantage of newer stem cell-based technologies to study the mechanisms by which VZV infects human neurons. We find that the c-Jun N-terminal kinase (JNK) pathway is activated by VZV infection and that blockade of this pathway limits lytic replication (as occurs during primary infection). In addition, JNK inhibition limits viral reactivation, exhibiting parallels with herpes simplex virus reactivation. The identification of the role of the JNK pathway in VZV infection of neurons reveals potential avenues for the development of alternate antiviral drugs.

G Protein-Coupled Receptor Kinases in the Inflammatory Response and Signaling

G protein-coupled receptor kinases (GRKs) are serine/threonine kinases that regulate a large and diverse class of G protein-coupled receptors (GPCRs). Through GRK phosphorylation and β-arrestin recruitment, GPCRs are desensitized and their signal terminated. Recent work on these kinases has expanded their role from canonical GPCR regulation to include noncanonical regulation of non-GPCR and nonreceptor substrates through phosphorylation as well as via scaffolding functions. Owing to these and other regulatory roles, GRKs have been shown to play a critical role in the outcome of a variety of physiological and pathophysiological processes including chemotaxis, signaling, migration, inflammatory gene expression, etc. This diverse set of functions for these proteins makes them popular targets for therapeutics. Role for these kinases in inflammation and inflammatory disease is an evolving area of research currently pursued in many laboratories. In this review, we describe the current state of knowledge on various GRKs pertaining to their role in inflammation and inflammatory diseases.

BX-795 inhibits HSV-1 and HSV-2 replication by blocking the JNK/p38 pathways without interfering with PDK1 activity in host cells

BX-795 is an inhibitor of 3-phosphoinositide-dependent kinase 1 (PDK1), but also a potent inhibitor of the IKK-related kinase, TANKbinding kinase 1 (TBK1) and IKKɛ. In this study we attempted to elucidate the molecular mechanism(s) underlying the inhibition of BX-795 on Herpes simplex virus (HSV) replication. HEC-1-A or Vero cells were treated with BX-795 and infected with HSV-1 or HSV-2 for different periods. BX-795 (3.125-25 μmol/L) dose-dependently suppressed HSV-2 replication, and displayed a low cytotoxicity to the host cells. BX-795 treatment dose-dependently suppressed the expression of two HSV immediate-early (IE) genes (ICP0 and ICP27) and the late gene (gD) at 12 h postinfection. HSV-2 infection resulted in the activation of PI3K and Akt in the host cells, and BX-795 treatment inhibited HSV-2-induced Akt phosphorylation and activation. However, the blockage of PI3K/Akt/mTOR with LY294002 and rapamycin did not affect HSV-2 replication. HSV-2 infection increased the phosphorylation of JNK and p38, and reduced ERK phosphorylation at 8 h postinfection in the host cells; BX-795 treatment inhibited HSV-2-induced activation of JNK and p38 MAP kinase as well as the phosphorylation of c-Jun and ATF-2, the downstream targets of JNK and p38 MAP kinase. Furthermore, SB203580 (a p38 inhibitor) or SP600125 (a JNK inhibitor) dose-dependently inhibited the viral replication in the host cells, whereas PD98059 (an ERK inhibitor) was not effective. Moreover, BX-795 blocked PMA-stimulated c-Jun activation as well as HSV-2-mediated c-Jun nuclear translocation. BX-795 dose-dependently inhibited HSV-2, PMA, TNF-α-stimulated AP-1 activation, but not HSV-induced NF-κB activation. Overexpression of p38/JNK attenuated the inhibitory effect of BX-795 on HSV replication. BX-795 completely blocked HSV-2-induced MKK4 phosphorylation, suggesting that BX-795 acting upstream of JNK and p38 MAP kinase. In conclusion, this study identifies the anti-HSV activity of BX-795 and its targeting of the JNK/p38 MAP kinase pathways in host cells.

The activation of p38MAPK and JNK pathways in bovine herpesvirus 1 infected MDBK cells

We have shown previously that BHV-1 infection activates Erk1/2 signaling. Here, we show that BHV-1 provoked an early-stage transient and late-stage sustained activation of JNK, p38MAPK and c-Jun signaling in MDBK cells. C-Jun phosphorylation was dependent on JNK. These early events were partially due to the viral entry process. Unexpectedly, reactive oxygen species were not involved in the later activation phase. Interestingly, only activated JNK facilitated the viral multiplication identified through both chemical inhibitor and siRNA. Collectively, this study provides insight into our understanding of early stages of BHV-1 infection.

CyHV-2 ORF104 activates the p38 MAPK pathway

Cyprinid herpesvirus 2 (CyHV-2) is the pathogen responsible for herpesviral hematopoietic necrosis disease, which causes huge losses on aquaculture. So far the studies of CyHV-2 mainly focus on the identification and detection of this virus, but little is known about the role of specific CyHV-2 genes in the infection process. Based on the genomic information, CyHV-2 ORF104 encodes a kinase-like protein, which is highly conserved among the three CyHVs. Our study was initiated to investigate the role of kinase-like protein ORF104 during virus infection. Subcellular localization study showed that ORF104 was mainly expressed in the nucleus in both human HEK293T and fish EPC cells. However, deletion of the putative nuclear localization signal of ORF104 (ORF104M) resulted in the cytoplasmic distribution in HEK293T. We then examined whether MAPKs were involved in the ORF104-mediated signaling pathway by overexpressing ORF104 and ORF104M in HEK293T. Overexpression of ORF104 and ORF104M resulted in the up-regulation of p38 phosphorylation, but not JNK or ERK, indicating that ORF104 specifically activates p38 signaling pathway. In vivo study showed that CyHV-2 infection enhanced p38 phosphorylation in gibel carp (Carassius auratus gibelio). Interestingly, p38 inhibitor SB203580 strongly reduced fish death caused by CyHV-2 infection. Therefore, our study for the first time reveals the function of ORF104 during CyHV-2 infection, indicating that ORF104 is a potential vaccine candidate for CyHV-2.

Pedilanthus tithymaloides Inhibits HSV Infection by Modulating NF-κB Signaling

Pedilanthus tithymaloides (PT), a widely used ethnomedicinal plant, has been employed to treat a number of skin conditions. To extend its utility and to fully exploit its medicinal potential, we have evaluated the in vitro antiviral activity of a methanolic extract of PT leaves and its isolated compounds against Herpes Simplex Virus type 2 (HSV-2). Bioactivity-guided studies revealed that the extract and one of its constituents, luteolin, had potent antiviral activity against wild-type and clinical isolates of HSV-2 (EC₅₀ 48.5–52.6 and 22.4–27.5 μg/ml, respectively), with nearly complete inhibition at 86.5–101.8 and 40.2–49.6 μg/ml, respectively. The inhibitory effect was significant (p<0.001) when the drug was added 2 h prior to infection, and was effective up to 4 h post-infection. As viral replication requires NF-κB activation, we examined whether the observed extract-induced inhibition of HSV-2 was related to NF-κB inhibition. Interestingly, we observed that treatment of HSV-2-infected cells with extract or luteolin suppressed NF-κB activation. Although NF-κB, JNK and MAPK activation was compromised during HSV replication, neither the extract nor luteolin affected HSV-2-induced JNK1/2 and MAPK activation. Moreover, the PT leaf extract and luteolin potently down-regulated the expression of tumor necrosis factor (TNF)-α, Interleukin (IL)-1β, IL-6, NO and iNOS and the production of gamma interferon (IFN-γ), which are directly involved in controlling the NF-κB signaling pathway. Thus, our results indicate that both PT leaf extract and luteolin modulate the NF-κB signaling pathway, resulting in the inhibition of HSV-2 replication.

Differential Reovirus-Specific and Herpesvirus-Specific Activator Protein 1 Activation of Secretogranin II Leads to Altered Virus Secretion

Viruses utilize host cell machinery for propagation and manage to evade cellular host defense mechanisms in the process. Much remains unknown regarding how the host responds to viral infection. We recently performed global proteomic screens of mammalian reovirus TIL- and T3D-infected and herpesvirus (herpes simplex virus 1 [HSV-1])-infected HEK293 cells. The nonenveloped RNA reoviruses caused an upregulation, whereas the enveloped DNA HSV-1 caused a downregulation, of cellular secretogranin II (SCG2). SCG2, a member of the granin family that functions in hormonal peptide sorting into secretory vesicles, has not been linked to virus infections previously. We confirmed SCG2 upregulation and found SCG2 phosphorylation by 18 h postinfection (hpi) in reovirus-infected cells. We also found a decrease in the amount of reovirus secretion from SCG2 knockdown cells. Similar analyses of cells infected with HSV-1 showed an increase in the amount of secreted virus. Analysis of the stress-activated protein kinase (SAPK)/Jun N-terminal protein kinase (JNK) pathway indicated that each virus activates different pathways leading to activator protein 1 (AP-1) activation, which is the known SCG2 transcription activator. We conclude from these experiments that the negative correlation between SCG2 quantity and virus secretion for both viruses indicates a virus-specific role for SCG2 during infection.

IMPORTANCE

Mammalian reoviruses affect the gastrointestinal system or cause respiratory infections in humans. Recent work has shown that all mammalian reovirus strains (most specifically T3D) may be useful oncolytic agents. The ubiquitous herpes simplex viruses cause common sores in mucosal areas of their host and have coevolved with hosts over many years. Both of these virus species are prototypical representatives of their viral families, and investigation of these viruses can lead to further knowledge of how they and the other more pathogenic members of their respective families interact with the host. Here we show that secretogranin II (SCG2), a protein not previously studied in the context of virus infections, alters virus output in a virus-specific manner and that the quantity of SCG2 is inversely related to amounts of infectious-virus secretion. Herpesviruses may target this protein to facilitate enhanced virus release from the host.

G-protein-coupled receptor kinases in inflammation and disease

G-protein-coupled receptor kinases (GRKs) are serine/threonine protein kinases originally discovered for their role in G-protein-coupled receptor (GPCR) phosphorylation. Recent studies have demonstrated a much broader function for this kinase family including phosphorylation of cytosolic substrates involved in cell signaling pathways stimulated by GPCRs, as well as by non-GPCRs. In addition, GRKs modulate signaling via phosphorylation-independent functions. Because of these various biochemical functions, GRKs have been shown to affect critical physiological and pathophysiological processes, and thus are considered as drug targets in diseases such as heart failure. Role of GRKs in inflammation and inflammatory diseases is an evolving area of research and several studies including work from our lab in the recent years have demonstrated critical role of GRKs in the immune system. In this review, we discuss the classical and the newly emerging functions of GRKs in the immune system and their role in inflammation and disease processes.

AP-1 Transcription Factor Serves as a Molecular Switch between Chlamydia pneumoniae Replication and Persistence

Chlamydia pneumoniae is a Gram-negative bacterium that causes acute or chronic respiratory infections. As obligate intracellular pathogens, chlamydiae efficiently manipulate host cell processes to ensure their intracellular development. Here we focused on the interaction of chlamydiae with the host cell transcription factor activator protein 1 (AP-1) and its consequence on chlamydial development. During Chlamydia pneumoniae infection, the expression and activity of AP-1 family proteins c-Jun, c-Fos, and ATF-2 were regulated in a time- and dose-dependent manner. We observed that the c-Jun protein and its phosphorylation level significantly increased during C. pneumoniae development. Small interfering RNA knockdown of the c-Jun protein in HEp-2 cells reduced the chlamydial load, resulting in smaller inclusions and significantly lower chlamydial recovery. Furthermore, inhibition of the c-Jun-containing AP-1 complexes using tanshinone IIA changed the replicative infection phenotype into a persistent one. Tanshinone IIA-dependent persistence was characterized by smaller, aberrant inclusions, a strong decrease in the chlamydial load, and significantly reduced chlamydial recovery, as well as by the reversibility of the reduced recovery after the removal of tanshinone IIA. Interestingly, not only was tanshinone IIA treatment accompanied by a significant decrease of ATP levels, but fluorescence live cell imaging analysis by two-photon microscopy revealed that tanshinone IIA treatment also resulted in a decreased fluorescence lifetime of protein-bound NAD(P)H inside the chlamydial inclusion, indicating that chlamydial reticulate bodies have decreased metabolic activity. In all, these data demonstrate that the AP-1 transcription factor is involved in C. pneumoniae development, with tanshinone IIA treatment resulting in persistence.

γ₁34.5-deleted HSV-1-expressing human cytomegalovirus IRS1 gene kills human glioblastoma cells as efficiently as wild-type HSV-1 in normoxia or hypoxia

Pathophysiological hypoxia, which fosters the glioma stem-like cell (GSC) phenotype, is present in high-grade gliomas and has been linked to tumor development, invasiveness and resistance to chemotherapy and radiation. Oncolytic virotherapy with engineered herpes simplex virus-1 (HSV-1) is a promising therapy for glioblastoma; however, the efficacy of γ(1)34.5-deleted HSVs, which have been used in clinical trials, was diminished in hypoxia. We investigated the ability of a chimeric human cytolomegalovirus (HCMV)/HSV-1 virus, which expresses the human CMV protein kinase R evasion gene IRS1 and is in preparation for clinical trials, to infect and kill adult and pediatric patient-derived glioblastoma xenografts in hypoxia and normoxia. Infectivity, cytotoxicity and viral recovery were significantly greater with the chimeric virus compared with the γ(1)34.5-deleted virus, regardless of oxygen tension. The chimeric virus infected and killed CD133+ GSCs similarly to wild-type HSV-1. Increased activation of mitogen-activated protein kinase p38 and its substrate heat-shock protein 27 (Hsp27) was seen after viral infection in normoxia compared with hypoxia. Hsp27 knockdown or p38 inhibition reduced virus recovery, indicating that the p38 pathway has a role in the reduced efficacy of the γ(1)34.5-deleted virus in hypoxia. Taken together, these findings demonstrate that chimeric HCMV/HSV-1 efficiently targets both CD133+ GSCs and glioma cells in hypoxia.

Identification of a c-Jun homolog from Litopenaeus vannamei as a downstream substrate of JNK in response to WSSV infection

c-Jun, a major substrate of c-Jun N-terminal kinase (JNK), participates in regulating gene transcription in response to various stimuli, including cytokines, stress signals, bacterial and viral infection. Results from our previous studies suggested that Litopenaeus vannamei JNK (LvJNK) could be utilized by white spot syndrome virus (WSSV) to facilitate viral replication and gene expression. In this article, a c-Jun homolog from Litopenaeus vannamei (designated as Lvc-Jun) was cloned and its role in WSSV infection was studied. Sequence analysis displayed that Lvc-Jun was a novel homolog of c-Jun family, which contained characteristic Jun and basic leucine zipper (bZIP) domains, and two conserved serine phosphorylation sites (Ser49/59). Semi-quantitative RT-PCR analysis showed that Lvc-Jun mRNAs were expressed in all examined tissues. Further investigation determined that Lvc-Jun was located in the nucleus through self-interaction and its phosphorylation levels could be reduced by JNK inhibitor, suggesting that Lvc-Jun could be regulated by LvJNK through phosphorylation and function as a transcription regulator in a homodimer. During the process of WSSV infection, the transcription levels of Lvc-Jun were up-regulated associating with the raising expression and phosphorylation levels of its protein. Moreover, TPA (12-O-tetradecanoylphorbol-13-acetate), a potent inducer of c-Jun, could remarkably promote viral immediate-early gene wsv069 transcription in crayfish hemocytes. Conclusively, our results provided experimental evidences that Lvc-Jun was engaged in WSSV infection and further implied that JNK-c-Jun signaling pathway might be important for WSSV replication and viral gene expression.

Downregulation of cellular c-Jun N-terminal protein kinase and NF-κB activation by berberine may result in inhibition of herpes simplex virus replication

Berberine is a quaternary ammonium salt from the protoberberine group of isoquinoline alkaloids. Some reports show that berberine exhibits anti-inflammatory, antitumor, and antiviral properties by modulating multiple cellular signaling pathways, including p53, nuclear factor κB (NF-κB), and mitogen-activated protein kinase. In the present study, we investigated the antiviral effect of berberine against herpes simplex virus (HSV) infection. Current antiherpes medicines such as acyclovir can lessen the recurring activation when used early at infection but are unable to prevent or cure infections where treatment has selected for resistant mutants. In searching for new antiviral agents against herpesvirus infection, we found that berberine reduced viral RNA transcription, protein synthesis, and virus titers in a dose-dependent manner. To elucidate the mechanism of its antiviral activity, the effect of berberine on the individual steps of viral replication cycle of HSV was investigated via time-of-drug addition assay. We found that berberine acted at the early stage of HSV replication cycle, between viral attachment/entry and genomic DNA replication, probably at the immediate-early gene expression stage. We further demonstrated that berberine significantly reduced HSV-induced NF-κB activation, as well as IκB-α degradation and p65 nuclear translocation. Moreover, we found that berberine also depressed HSV-induced c-Jun N-terminal kinase (JNK) phosphorylation but had little effect on p38 phosphorylation. Our results suggest that the berberine inhibition of HSV infection may be mediated through modulating cellular JNK and NF-κB pathways.

TRAF2 facilitates vaccinia virus replication by promoting rapid virus entry

Tumor necrosis factor receptor (TNFR)-associated factor 2 (TRAF2) is a pivotal intracellular mediator of signaling pathways downstream of TNFR1 and -2 with known pro- and antiviral effects. We investigated its role in the replication of the prototype poxvirus vaccinia virus (VACV). Loss of TRAF2 expression, either through small interfering RNA treatment of HeLa cells or through genetic knockout in murine embryonic fibroblasts (MEFs), led to significant reductions in VACV growth following low-multiplicity infection. In single-cycle infections, there was delayed production of both early and late VACV proteins as well as accelerated virus-induced alterations to cell morphology, indicating that TRAF2 influences early stages of virus replication. Consistent with an early role, uncoating assays showed normal virus attachment but delayed virus entry in the absence of TRAF2. Although alterations to c-Jun N-terminal kinase (JNK) signaling were apparent in VACV-infected TRAF2^−/− MEFs, treatment of wild-type cells with a JNK inhibitor did not affect virus entry. Instead, treatment with an inhibitor of endosomal acidification greatly reduced virus entry into TRAF2^−/− MEFs, suggesting that VACV is reliant on the endosomal route of entry in the absence of TRAF2. Thus, TRAF2 is a proviral factor for VACV that plays a role in promoting efficient viral entry, most likely via the plasma membrane.

IMPORTANCE Tumor necrosis factor receptor-associated factors (TRAFs) are key facilitators of intracellular signaling with roles in innate and adaptive immunity and stress responses. We have discovered that TRAF2 is a proviral factor in vaccinia virus replication in both HeLa cells and mouse embryonic fibroblasts and that its influence is exercised through promotion of efficient virus entry.

Zinc ionophores pyrithione inhibits herpes simplex virus replication through interfering with proteasome function and NF-κB activation

Pyrithione (PT), known as a zinc ionophore, is effective against several pathogens from the Streptococcus and Staphylococcus genera. The antiviral activity of PT was also reported against a number of RNA viruses. In this paper, we showed that PT could effectively inhibit herpes simplex virus types 1 and 2 (HSV-1 and HSV-2). PT inhibited HSV late gene (Glycoprotein D, gD) expression and the production of viral progeny, and this action was dependent on Zn(2+). Further studies showed that PT suppressed the expression of HSV immediate early (IE) gene, the infected cell polypeptide 4 (ICP4), but had less effect on another regulatory IE protein, ICP0. It was found that PT treatment could interfere with cellular ubiquitin-proteasome system (UPS), leading to the inhibition of HSV-2-induced IκB-α degradation to inhibit NF-κB activation and enhanced promyelocytic leukemia protein (PML) stability in nucleus. However, PT did not show direct inhibition of 26S proteasome activity. Instead, it induced Zn(2+) influx, which facilitated the dysregulation of UPS and the accumulation of intracellular ubiquitin-conjugates. UPS inhibition by PT caused disruption of IκB-α degradation and NF-κB activation thus leading to marked reduction of viral titer.

Pyrrolidine dithiocarbamate inhibits herpes simplex virus 1 and 2 replication, and its activity may be mediated through dysregulation of the ubiquitin-proteasome system

Pyrrolidine dithiocarbamate (PDTC) is widely used as an antioxidant or an NF-κB inhibitor. It has been reported to inhibit the replication of human rhinoviruses, poliovirus, coxsackievirus, and influenza virus. In this paper, we report that PDTC could inhibit the replication of herpes simplex virus 1 and 2 (HSV-1 and HSV-2). PDTC suppressed the expression of HSV-1 and HSV-2 viral immediate early (IE) and late (membrane protein gD) genes and the production of viral progeny. This antiviral property was mediated by the dithiocarbamate moiety of PDTC and required the presence of Zn(2+). Although PDTC could potently block reactive oxygen species (ROS) generation, it was found that this property did not contribute to its anti-HSV activity. PDTC showed no activity in disrupting the mitogen-activated protein kinase (MAPK) pathway activation induced by viral infection that was vital for the virus's propagation. We found that PDTC modulated cellular ubiquitination and, furthermore, influenced HSV-2-induced IκB-α degradation to inhibit NF-κB activation and enhanced PML stability in the nucleus, resulting in the inhibition of viral gene expression. These results suggested that the antiviral activity of PDTC might be mediated by its dysregulation of the cellular ubiquitin-proteasome system (UPS).

Anti-rotaviral effects of Glycyrrhiza uralensis extract in piglets with rotavirus diarrhea

Background

Since rotavirus is one of the leading pathogens that cause severe gastroenteritis and represents a serious threat to human and animal health, researchers have been searching for cheap, safe, and effective anti-rotaviral drugs. There is a widespread of interest in using natural products as antiviral agents, and among them, licorice derived from Glycyrrhiza spp. has exerted antiviral properties against several viruses. In this study, anti-rotaviral efficacy of Glycyrrhiza uralensis extract (GUE) as an effective and cheaper remedy without side-effects was evaluated in colostrums-deprived piglets after induction of rotavirus diarrhea.

Methods

Colostrums-deprived piglets were inoculated with porcine rotavirus K85 (G5P[7]) strain. On the onset of diarrhea, piglets were treated with different concentration of GUE. To evaluate the antiviral efficacy of GUE, fecal consistency score, fecal virus shedding and histological changes of the small intestine, mRNA expression levels of inflammation-related cytokines (IL8, IL10, IFN-β, IFN-γ and TNF-α), signaling molecules (p38 and JNK), and transcription factor (NFκB) in the small intestine and spleen were determined.

Results

Among the dosages (100-400 mg/ml) administrated to animals, 400 mg/ml of GUE cured diarrhea, and markedly improved small intestinal lesion score and fecal virus shedding. mRNA expression levels of inflammation-related cytokines (IL8, IL10, IFN-β, IFN-γ and TNF-α), signaling molecules (p38 and JNK), and transcription factor (NFκB) in the small intestine and spleen were markedly increased in animals with RVA-induced diarrhea, but dose- dependently decreased in GUE treated animals after RVA-induced diarrhea.

Conclusions

GUE cures rotaviral enteritis by coordinating antiviral and anti-inflammatory effects. Therapy of this herbal medicine can be a viable medication for curing rotaviral enteritis in animals and humans.

Transcription factor complex AP-1 mediates inflammation initiated by Chlamydia pneumoniae infection

Chlamydia pneumoniae is responsible for a high prevalence of respiratory infections worldwide and has been implicated in atherosclerosis. Inflammation is regulated by transcription factor (TF) networks. Yet, the core TF network triggered by chlamydiae remains largely unknown. Primary human coronary artery endothelial cells were mock-infected or infected with C. pneumoniae to generate human transcriptome data throughout the chlamydial developmental cycle. Using systems network analysis, the predominant TF network involved receptor, binding and adhesion and immune response complexes. Cells transfected with interfering RNA against activator protein-1 (AP-1) members FOS, FOSB, JUN and JUNB had significantly decreased expression and protein levels of inflammatory mediators interleukin (IL)6, IL8, CD38 and tumour necrosis factor compared with controls. These mediators have been shown to be associated with C. pneumoniae disease. Expression of AP-1 components was regulated by MAPK3K8, a MAPK pathway component. Additionally, knock-down of JUN and FOS showed significantly decreased expression of Toll-like receptor (TLR)3 during infection, implicating JUN and FOS in TLR3 regulation. TLR3 stimulation led to elevated IL8. These findings suggest that C. pneumoniae initiates signalling via TLR3 and MAPK that activate AP-1, a known immune activator in other bacteria not previously shown for chlamydiae, triggering inflammation linked to C. pneumoniae disease.

A novel JNK from Litopenaeus vannamei involved in white spot syndrome virus infection

The c-Jun N-terminal kinase (JNK), a member of MAP kinases, is a serine/threonine-specific protein kinase which responds to extracellular stimuli and regulate various cellular activities. It is well documented in innate immune responses and reported to be involved in various viral infections of mammals. In present study, we cloned JNK homolog in a crustacean, Litopenaeus vannamei (designated as LvJNK) and studied its role in white spot syndrome virus (WSSV) infection. Sequence analysis displayed that LvJNK shared high similarity with other members of the JNK subfamily, including the conserved TPY motif and serine/threonine protein kinase (S_TKc) domain. Western blot analysis showed that the activation of LvJNK took place in WSSV infection. LvJnk silencing mediated by specific dsRNA in shrimps could significantly inhibit the proliferation of the virus. Moreover, inhibition of shrimp JNK signaling pathway by specific inhibitor resulted in the reduction of WSSV replication and the delay of WSSV gene transcription. These results indicate for the first time that shrimp JNK is activated in response to WSSV infection and WSSV could benefit from JNK activation. It may facilitate our understanding of the molecular mechanism of virus infection and provided a potential target for preventing the WSSV infection.

Suppression of extracellular signal-regulated kinase activity in herpes simplex virus 1-infected cells by the Us3 protein kinase

Host mitogen-activated protein kinases (MAPKs) are deregulated by herpes simplex virus 1 (HSV-1). Unlike p38 MAPK and Jun N-terminal protein kinase (JNK), which require ICP27 for their activation early in infection, extracellular signal-regulated kinase (ERK) activity is suppressed by an unknown mechanism. Here, we establish that HSV-1-induced suppression of ERK activity requires viral gene expression, occurs with delayed-early kinetics, and requires the functional virus-encoded Us3 Ser/Thr protein kinase. Finally, Us3 expression in uninfected cells was necessary and sufficient to suppress ERK activity in the absence of any other virus-encoded gene products. This demonstrates that inhibition of ERK activity in HSV-1-infected cells is an intrinsic Us3 function and defines a new role for this alphaherpesvirus Us3 kinase in regulating MAPK activation in infected cells.

Activation of NF-κB in CD8+ dendritic cells Ex Vivo by the γ134.5 null mutant correlates with immunity against herpes simplex virus 1

The γ(1)34.5 protein of herpes simplex viruses (HSV) is essential for virulence. Accordingly, an HSV mutant lacking γ(1)34.5 is attenuated in vivo. Despite its vaccine potential, the mechanism by which the γ(1)34.5 null mutant triggers protective immunity is unknown. In this report we show that vaccination with the γ(1)34.5 null mutant protects against lethal challenge from wild-type virus via IκB kinase in dendritic cells (DCs), which sense virus-associated molecular patterns. Unlike mock-treated DCs, DCs primed with the γ(1)34.5 null mutant ex vivo mediate resistance to wild-type HSV after adoptive transfer into naïve mice. Furthermore, the γ(1)34.5 null mutant activates IκB kinase, which facilitates p65/RelA phosphorylation and nuclear translocation, resulting in DC maturation. While unable to produce infectious virus in DCs, this mutant virus expresses early and late genes. In its abortive infection, the γ(1)34.5 null mutant induces protective immunity more effectively in CD8(+) DCs than in CD8(-) DCs. This is mirrored by a higher level of interleukin-6 (IL-6) and IL-12 secretion by CD8(+) DCs than CD8(-) DCs. Remarkably, inhibition of p65/RelA phosphorylation or nuclear translocation in CD8(+) DCs disrupts protective immunity. These results suggest that engagement of the γ(1)34.5 null mutant with CD8(+) DCs elicits innate immunity to activate NF-κB, which translates into protective immunity.

The role of MAPK in CD4(+) T cells toll-like receptor 9-mediated signaling following HHV-6 infection

Human herpesvirus-6 (HHV-6) is an important immunosuppressive and immunomodulatory virus that primarily infects immune cells (mainly CD4(+) T cells) and strongly suppresses the proliferation of infected cells. Toll-like receptors are pattern-recognition receptors essential for the development of an appropriate innate immune defense against infection. To understand the role of CD4(+) T cells in the innate response to HHV-6 infection and the involvement of TLRs, we used an in vitro infection model and observed that the infection of CD4(+) T cells resulted in the activation of JNK/SAPK via up-regulation of toll-like receptor 9 (TLR9). Associated with JNK activation, annexin V-PI staining indicated that HHV-6A was a strong inducer of apoptosis. Apoptotic response associated cytokines, IL-6 and TNF-α also induced by HHV-6A infection.

Sensing herpes: more than toll

To launch an effective antiviral immune response, cells must recognize the virus, activate a cytokine response, and initiate inflammatory processes. Herpes simplex virus 1 (HSV-1) and HSV-2 are nuclear-replicating viruses composed of a double-stranded DNA genome plus glycoproteins that are incorporated into a lipid bilayer envelope that surrounds an icosahedral capsid. Several novel receptors that mediate innate recognition of HSV and that activate the innate immune response have been identified in recent years. The host-virus interactions that lead to type I interferon (IFN), type III IFN, and cytokine production include cellular recognition of viral envelope and structural proteins, recognition of viral genomic DNA and recognition of virus-derived double-stranded RNAs. Such RNAs can interact with cellular pattern-recognition receptors, including Toll-like receptors and a number of cytoplasmic and nuclear receptors for virus DNA and virus-derived RNAs. In this review, I present a systematic overview of innate cellular recognition of HSV infection that leads to immune activation, and I discuss the implications of the known cell-host interactions. In addition, I discuss the use of innate stimulation to improve anti-HSV treatment and vaccine response and I discuss future research aims.

Infectious bursal disease virus-induced activation of JNK signaling pathway is required for virus replication and correlates with virus-induced apoptosis

The Jun NH2-terminal kinase (JNK) which serves as an important component of cellular signal transduction pathways has been shown to regulate many viral infections. The present study demonstrated for the first time that infectious bursal disease virus (IBDV), the causative agent of a highly contagious disease in chickens, can activate JNK1/2 pathway in IBDV-infected cells dependent upon viral replication. IBDV-induced JNK1/2 activation causes its downstream target c-Jun phosphorylation, which kinetically paralleled JNK1/2 activation. Investigations into the mechanism of JNK1/2 regulation revealed that inhibition of JNK1/2 activation leads to reduced viral progeny release, which is associated with decreased viral transcription and lower virus protein expression, and thereby limiting apoptotic cell death as evidenced by blockage of Bax activation, cytochrome c release, and caspase activation. These data suggest that the JNK pathway plays an important role in the IBDV replication and contributes to virus-mediated changes in host cells.

Houttuynia cordata blocks HSV infection through inhibition of NF-κB activation

Houttuynia cordata Thunb. is a medicinal plant widely used in folk medicine in several Asian countries. It has been reported that a water extract of H. cordata exhibits activity against herpes simplex virus (HSV) and the virus of severe acute respiratory syndrome (SARS), although the mechanisms are not fully understood yet. Previous studies have demonstrated absolute requirement of NF-κB activation for efficient replication of HSV-1 and HSV-2 and inhibition of NF-κB activation has been shown to suppress HSV infection. Here we show that a hot water extract of H. cordata (HCWE) inhibits HSV-2 infection through inhibition of NF-κB activation. The IC₅₀ was estimated at 50 μg/ml of lyophilized HCWE powder. At 150 and 450 μg/ml, HCWE blocked infectious HSV-2 production by more than 3 and 4 logs, respectively. The inhibitory activity was concomitant with an inhibition of NF-κB activation by HSV-2 infection. Although activation of NF-κB and Erk MAPK has been implicated for HSV replication and growth, HCWE showed no effect on HSV-2-induced Erk activation. Furthermore, we show that treatment with quercetin, quercitrin or isoquercitrin, major water extractable flavonoids from H. cordata, significantly blocked HSV-2 infection. These results together demonstrated that H. cordata blocks HSV-2 infection through inhibition of NF-κB activation.

Lytic HSV-1 infection induces the multifunctional transcription factor Early Growth Response-1 (EGR-1) in rabbit corneal cells

BACKGROUND

Herpes simplex virus type-1 (HSV-1) infections can cause a number of diseases ranging from simple cold sores to dangerous keratitis and lethal encephalitis. The interaction between virus and host cells, critical for viral replication, is being extensively investigated by many laboratories. In this study, we tested the hypothesis that HSV-1 lytic infection triggers the expression of important multi-functional transcription factor Egr1. The mechanisms of induction are mediated, at least in part, by signaling pathways such as NFκB and CREB.

METHODS

SIRC, VERO, and 293HEK cell lines were infected with HSV-1, and the Egr-1 transcript and protein were detected by RT-PCR and Western blot, respectively. The localization and expression profile of Egr-1 were investigated further by immunofluorescence microscopy analyses. The recruitment of transcription factors to the Egr-1 promoter during infection was studied by chromatin immunoprecipitation (ChIP). Various inhibitors and dominant-negative mutant were used to assess the mechanisms of Egr-1 induction and their effects were addressed by immunofluorescence microscopy.

RESULTS

Western blot analyses showed that Egr-1 was absent in uninfected cells; however, the protein was detected 24-72 hours post treatment, and the response was directly proportional to the titer of the virus used for infection. Using recombinant HSV-1 expressing EGFP, Egr-1 was detected only in the infected cells. ChIP assays demonstrated that NFкB and cAMP response element binding protein (CREB) were recruited to the Egr-1 promoter upon infection. Additional studies showed that inhibitors of NFкB and dominant-negative CREB repressed the Egr-1 induction by HSV-1 infection.

CONCLUSION

Collectively, these results demonstrate that Egr-1 is expressed rapidly upon HSV-1 infection and that this novel induction could be due to the NFкB/CREB-mediated transactivation. Egr-1 induction might play a key role in the viral gene expression, replication, inflammation, and the disease progression.