Herpes simplex virus 2 modulates apoptosis and stimulates NF-kappaB nuclear translocation during infection in human epithelial HEp-2 cells

Several Alphaherpesviruses Interact Similarly with the NF-κB Pathway and Suppress NF-κB-Dependent Gene Expression

Alphaherpesvirus infection is associated with attenuation of different aspects of the host innate immune response that is elicited to confine primary infections at the mucosal epithelia. Here, we report that infection of epithelial cells with several alphaherpesviruses of different species, including herpes simplex virus 1 and 2 (HSV-1 and HSV-2), feline alphaherpesvirus 1 (FHV-1), and bovine alphaherpesvirus 1 (BoHV-1) results in the inactivation of the responses driven by the nuclear factor kappa B (NF-κB) pathway, considered a pillar of the innate immune response. The mode to interact with and circumvent NF-κB-driven responses in infected epithelial cells is seemingly conserved in human, feline, and porcine alphaherpesviruses, consisting of a persistent activation of the NF-κB cascade but a potent repression of NF-κB-dependent transcription activity, which relies on replication of viral genomes. However, BoHV-1 apparently deviates from the other investigated members of the taxon in this respect, as BoHV-1-infected epithelial cells do not display the persistent NF-κB activation observed for the other alphaherpesviruses. In conclusion, this study suggests that inhibition of NF-κB transcription activity is a strategy used by several alphaherpesviruses to prevent NF-κB-driven responses in infected epithelial cells. IMPORTANCE The current study provides a side-by-side comparison of the interaction of different alphaherpesviruses with NF-κB, a key and central player in the (proinflammatory) innate host response, in infected nontransformed epithelial cell lines. We report that all studied viruses prevent expression of the hallmark NF-κB-dependent gene IκB, often but not always via similar strategies, pointing to suppression of NF-κB-dependent host gene expression in infected epithelial cells as a common and therefore likely important aspect of alphaherpesviruses.

Inhibitory activity and mechanism of silver nanoparticles against herpes simplex virus type 1

Herpes simplex virus type 1 (HSV-1) is a common pathogen that infects 50-90% of the world's population and causes a variety of diseases, some of which can be life-threatening. Silver nanoparticles (AgNPs) have been shown to have broad-spectrum antiviral activity. In this study, we investigated the activity of AgNPs against HSV-1 and found that AgNPs effectively inhibited plaque formation and HSV-1 progeny production, reduced the genomic load, and interfered with HSV-1 mRNA expression and protein synthesis. Transmission electron microscopy showed that AgNPs interacted with HSV-1 and altered the shape of the viral particles. Furthermore, AgNPs affected the entry of HSV-1 into cells as well as their release and cell-to-cell spread. AgNPs were also found to downregulate the expression of pro-inflammatory cytokines upon HSV-1 infection. Combined treatment with AgNPs and acyclovir (ACV) confirmed that AgNPs significantly enhanced the inhibitory effect of ACV against HSV-1. Our findings may contribute to an understanding of the mechanism of the antiviral effect of AgNPs against HSV-1 and help to provide a theoretical basis for their clinical application.

JieZe-1 Alleviates HSV-2 Infection-Induced Genital Herpes in Balb/c Mice by Inhibiting Cell Apoptosis via Inducing Autophagy

Objectives: Genital herpes (GH) is a common sexually transmitted disease mainly caused by herpes simplex virus 2 (HSV-2). JieZe-1 (JZ-1) is an in-hospital prescription that has been used in Tongji Hospital for many years to treat various lower female genital tract infectious diseases. Our previous study showed that JZ-1 can protect against HSV-2 infection in vitro by inducing autophagy. However, whether JZ-1 can protect against HSV-2 infection in vivo, and the underlying mechanisms involved still remain unclear. Therefore, this study was designed to address above questions. Methods: 8-week-old female balb/c mice were injected intravaginally with HSV-2 to establish GH model. The symptom score, body weight, and histological examination were recorded to assess the animal model of HSV-2 infected and the therapeutic effect of JZ-1. Inflammatory response was determined by detecting inflammatory cells infiltration and local cytokines levels. After then, under autophagy inhibitor chloroquine application, we measured the levels of cell apoptosis and autophagy and investigated the relationship between enhanced autophagy and cell apoptosis. Next, the classic PI3K/Akt/mTOR axis was examined, and in vitro experiment was carried out for further verification. Results: Our results showed that JZ-1 administration significantly reduces symptom score, increases weight gain and alleviates histological damage in HSV-2 infection-induced GH in balb/c mice. JZ-1 administration obviously ameliorates inflammatory responses with reduced T-lymphocytes, T helper cells, macrophages and neutrophils infiltration, and local IL-1β, IL-6, TNF-α and CCL2 levels. HSV-2 infection leads to massive cell apoptosis, which was also restored by JZ-1. Meanwhile, we found that HSV-2 infection blocks autophagic flux in vivo and JZ-1 administration induces autophagy. After chloroquine application, it was observed that the inhibition of autophagy is strongly associated with increased cell apoptosis, whereas the promotion of autophagy remarkedly decreases apoptosis. These results suggested that JZ-1 inhibits cell apoptosis in GH by inducing autophagy, which was further supported in later in vitro experiment. Additionally, PI3K/Akt/mTOR signaling pathway was also downregulated by JZ-1 administration. Conclusion: Our data demonstrated that JZ-1 can alleviate HSV-2 infection-induced GH in balb/c mice by inhibiting cell apoptosis via inducing autophagy, and the underlying mechanisms may be associated with the inhibition of PI3K/Akt/mTOR pathway.

Herpes Simplex Virus Type 2 Glycoprotein D Inhibits NF-κB Activation by Interacting with p65

NF-κB plays a crucial role in regulating cell proliferation, inflammation, apoptosis, and immune responses. HSV type 2 (HSV-2) is one of the most predominant sexually transmitted pathogens worldwide, and its infection increases the risk of HIV type 1 (HIV-1) acquisition and transmission. HSV-2 glycoprotein D (gD), highly homologous to HSV-1 gD, is essential for viral adhesion, fusion, entry, and spread. It is known that HSV-1 gD can bind herpesvirus entry mediator (HVEM) to trigger NF-κB activation and thereby facilitate viral replication at the early stage of infection. In this study, we found that purified HSV-2 gD triggered NF-κB activation at the early stage of infection, whereas ectopic expression of HSV-2 gD significantly downregulated TNF-α-induced NF-κB activity as well as TNF-α-induced IL-6 and IL-8 expression. Mechanistically, HSV-2 gD inhibited NF-κB, but not IFN-regulatory factor 3 (IRF3), activation and suppressed NF-κB activation mediated by overexpression of TNFR-associated factor 2 (TRAF2), IκB kinase α (IKKα), IKKβ, or p65. Coimmunoprecipitation and binding kinetic analyses demonstrated that HSV-2 gD directly bound to the NF-κB subunit p65 and abolished the nuclear translocation of p65 upon TNF-α stimulation. Mutational analyses further revealed that HSV-2 gD interacted with the region spanning aa 19-187 of p65. Findings in this study together demonstrate that HSV-2 gD interacts with p65 to regulate p65 subcellular localization and thereby prevents NF-κB-dependent gene expression, which may contribute to HSV-2 immune evasion and pathogenesis.

Pseudorabies Virus Infection of Epithelial Cells Leads to Persistent but Aberrant Activation of the NF-κB Pathway, Inhibiting Hallmark NF-κB-Induced Proinflammatory Gene Expression

The nuclear factor kappa B (NF-κB) is a potent transcription factor, activation of which typically results in robust proinflammatory signaling and triggering of fast negative feedback modulators to avoid excessive inflammatory responses. Here, we report that infection of epithelial cells, including primary porcine respiratory epithelial cells, with the porcine alphaherpesvirus pseudorabies virus (PRV) results in the gradual and persistent activation of NF-κB, illustrated by proteasome-dependent degradation of the inhibitory NF-κB regulator IκB and nuclear translocation and phosphorylation of the NF-κB subunit p65. PRV-induced persistent activation of NF-κB does not result in expression of negative feedback loop genes, like the gene for IκBα or A20, and does not trigger expression of prototypical proinflammatory genes, like the gene for tumor necrosis factor alpha (TNF-α) or interleukin-6 (IL-6). In addition, PRV infection inhibits TNF-α-induced canonical NF-κB activation. Hence, PRV infection triggers persistent NF-κB activation in an unorthodox way and dramatically modulates the NF-κB signaling axis, preventing typical proinflammatory gene expression and the responsiveness of cells to canonical NF-κB signaling, which may aid the virus in modulating early proinflammatory responses in the infected host.IMPORTANCE The NF-κB transcription factor is activated via different key inflammatory pathways and typically results in the fast expression of several proinflammatory genes as well as negative feedback loop genes to prevent excessive inflammation. In the current report, we describe that infection of cells with the porcine alphaherpesvirus pseudorabies virus (PRV) triggers a gradual and persistent aberrant activation of NF-κB, which does not result in expression of hallmark proinflammatory or negative feedback loop genes. In addition, although PRV-induced NF-κB activation shares some mechanistic features with canonical NF-κB activation, it also shows remarkable differences; e.g., it is largely independent of the canonical IκB kinase (IKK) and even renders infected cells resistant to canonical NF-κB activation by the inflammatory cytokine TNF-α. Aberrant PRV-induced NF-κB activation may therefore paradoxically serve as a viral immune evasion strategy and may represent an important tool to unravel currently unknown mechanisms and consequences of NF-κB activation.

Analysis of the anti-apoptotic v-Bcl2 and v-Flip genes and effect on in vitro programmed cell death of Argentinean isolates of bovine gammaherpesvirus 4 (BoHV-4)

Some viruses encode inhibitory factors of apoptosis during infection to prolong cell viability and then to achieve a higher production of viral progeny or facilitate persistent infections. There is evidence that some gammaherpesviruses, including BoHV-4, carry genes that can both inhibit or induce apoptosis. BoHV-4 possesses two genes (ORF16 and ORF71) that code for proteins with anti-apoptotic functions, such as v-Bcl2 and v-Flip, respectively. Thus, it is relevant to study BoHV-4 in relation to the modulation of apoptosis in infected cells as a strategy for persistence in the host. The objective of this work was to analyze whether variations in v-Flip and v- Bcl2 of six phylogenetically divergent Argentinean isolates of BoHV-4 can influence the capacity of these strains to induce apoptosis in cell cultures. In this study, variations were mainly detected in the v-Flip gene and protein of the BoHV-4 strains belonging to genotype 3. Thus, it is possible to infer that sequence variations could be associated with some BoHV-4 genotype. Induction of apoptosis was not a significant event for any of the genetically distinct local isolates of BoHV-4 and there was not an evident relationship between the variability of both genes with the apoptotic effect of the phylogenetically distinct strains.

NF-κB-Dependent Production of ROS and Restriction of HSV-1 Infection in U937 Monocytic Cells

Herpes simplex virus 1 (HSV-1) can infect a wide range of cell types, including cells of the adaptive and innate immunity but, normally, it completes a fully-permissive replication cycle only in epithelial or neural cells. Complex mechanisms controlling this delicate balance in immune cells and consequent restriction of HSV-1 infection in these cells have not been completely elucidated. We have recently demonstrated that the transcription factor nuclear factor kappa B (NF-κB) can act as a main permissiveness regulator of HSV-1 infection in monocytic cells, however, mediators involved in this regulation have not been identified. To better define mechanisms involved in this phenomenon and, particularly, the possible involvement of ROS, wild type U937 cells or U937 cells stably transfected with a dominant-negative (DN) IκB-mutant and selenium-containing compounds, as anti-oxidants, were utilized. The main results can be summarized as follows. HSV-1 infection induces an immediate ROS production in U937 monocytic cells that can efficiently activate NF-κB but not in DN-IκB-mutant cells. Treatment with selenium-containing antioxidants efficiently inhibited HSV-1-induced ROS generation while producing increased levels of HSV-1 replication and a reduction of HSV-1-induced NF-κB activation in U937 monocytic cells. Our results suggest a scenario in which an efficient NF-κB-dependent ROS production in response to infection could contribute in limiting HSV-1 replication in monocytes/macrophages, thus avoiding possible irreparable damage to the innate immune system of the host during HSV-1 infection.

Anti-HSV Activity of Kuwanon X from Mulberry Leaves with Genes Expression Inhibitory and HSV-1 Induced NF-κB Deactivated Properties

Six stilbene derivatives isolated from Mulberry leaves including Kuwanon X, Mulberrofuran C, Mulberrofuran G, Moracin C, Moracin M 3'-O-b-glucopyranoside and Moracin M were found to have antiviral effects against herpes simplex virus type 1 and 2 (HSV-1 and HSV-2) at different potencies except for Mulberrofuran G. Kuwanon X exhibited the greatest activity against HSV-1 15577 and clinical strains and HSV-2 strain 333 with IC₅₀ values of 2.2, 1.5 and 2.5 µg/mL, respectively. Further study revealed that Kuwanon X did not inactivate cell-free HSV-1 particles, but inhibited cellular adsorption and penetration of HSV-1 viral particles. Following viral penetration, Kuwanon X reduced the expression of HSV-1 IE and L genes, and decreased the synthesis of HSV-1 DNA. Furthermore, it was demonstrated that Kuwanon X inhibited the HSV-1-induced nuclear factor (NF)-κB activation through blocking the nuclear translocation and DNA binding of NF-κB. These results suggest that Kuwanon X exerts anti-HSV activity through multiple modes and could be a potential candidate for the therapy of HSV infection.

HSV-1-induced activation of NF-κB protects U937 monocytic cells against both virus replication and apoptosis

The transcription factor nuclear factor-kappa B (NF-κB) is a crucial player of the antiviral innate response. Intriguingly, however, NF-κB activation is assumed to favour herpes simplex virus (HSV) infection rather than restrict it. Apoptosis, a form of innate response to viruses, is completely inhibited by HSV in fully permissive cells, but not in cells incapable to fully sustain HSV replication, such as immunocompetent cells. To resolve the intricate interplay among NF-κB signalling, apoptosis and permissiveness to HSV-1 in monocytic cells, we utilized U937 monocytic cells in which NF-κB activation was inhibited by expressing a dominant-negative IκBα. Surprisingly, viral production was increased in monocytic cells in which NF-κB was inhibited. Moreover, inhibition of NF-κB led to increased apoptosis following HSV-1 infection, associated with lysosomal membrane permeabilization. High expression of late viral proteins and induction of apoptosis occurred in distinct cells. Transcriptional analysis of known innate response genes by real-time quantitative reverse transcription-PCR excluded a contribution of the assayed genes to the observed phenomena. Thus, in monocytic cells NF-κB activation simultaneously serves as an innate process to restrict viral replication as well as a mechanism to limit the damage of an excessive apoptotic response to HSV-1 infection. This finding may clarify mechanisms controlling HSV-1 infection in monocytic cells.

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.

The Telomerase Inhibitor MST-312 Interferes with Multiple Steps in the Herpes Simplex Virus Life Cycle

The life cycle of herpes simplex virus (HSV) has the potential to be further manipulated to yield novel, more effective therapeutic treatments. Recent research has demonstrated that HSV-1 can increase telomerase activity and that expression of the catalytic component of telomerase, telomerase reverse transcriptase (TERT), alters sensitivity to HSV-dependent apoptosis. Telomerase is a cellular enzyme that synthesizes nucleotide repeats at the ends of chromosomes (telomeres), which prevents shortening of the 3' ends of DNA with each cell division. Once telomeres reach a critical length, cells undergo senescence and apoptosis. Here, we used a cell-permeable, reversible inhibitor of the telomerase enzyme, MST-312, to investigate telomerase activity during HSV infection. Human mammary epithelial cells immortalized through TERT expression and human carcinoma HEp-2 cells were infected with the KOS1.1 strain of HSV-1 in the presence of MST-312. MST-312 treatment reduced the number of cells displaying a cytopathic effect and the accumulation of immediate early and late viral proteins. Moreover, the presence of 20 μM to 100 μM MST-312 during infection led to a 2.5- to 5.5-log10 decrease in viral titers. MST-312 also inhibited the replication of HSV-2 and a recent clinical isolate of HSV-1. Additionally, we determined that MST-312 has the largest impact on viral events that take place prior to 5 h postinfection (hpi). Furthermore, MST-312 treatment inhibited virus replication, as measured by adsorption assays and quantification of genome replication. Together, these findings demonstrate that MST-312 interferes with the HSV life cycle. Further investigation into the mechanism for MST-312 is warranted and may provide novel targets for HSV therapies.

IMPORTANCE

Herpes simplex virus (HSV) infections can lead to cold sores, blindness, and brain damage. Identification of host factors that are important for the virus life cycle may provide novel targets for HSV antivirals. One such factor, telomerase, is the cellular enzyme that synthesizes DNA repeats at the ends of chromosomes during replication to prevent DNA shortening. In this study, we investigate role of telomerase in HSV infection. The data demonstrate that the telomerase inhibitor MST-312 suppressed HSV replication at multiple steps of viral infection.

Anti-inflammatory functions of Houttuynia cordata Thunb. and its compounds: A perspective on its potential role in rheumatoid arthritis

The aim of this review was to take a look at the anti-inflammatory functions of Houttuynia cordata Thunb. (HCT) that have been illustrated in the literature and to explore new fields in which HCT could be used in the future. The use of HCT has been described in broad inflammatory domains, where it has exhibited a variety of activities, including antiviral, antibacterial, antiparasitic and immunostimulant activity, with high efficiency, mild features and definite therapeutic effects. The numerous anti-inflammatory functions of HCT have demonstrated that HCT has wide application prospects. New uses of HCT and the full extent of its utilization await further investigation. The basic pathological change of rheumatoid arthritis (RA) is synovial proliferation which leads to joint destruction in the long-term. There are types of drugs that have been used clinically for patients with RA, however, due to their side-effects or high prices their broad usage is limited. A safe and low-cost drug is urgently required to be developed for the clinical usage of patients with RA. Thus, HCT has the potential to be a good candidate in the treatment of rheumatoid arthritis.

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.

Fas/FasL pathway participates in resolution of mucosal inflammatory response early during HSV-2 infection

Apoptotic cell death is critical for maintaining integrity of the epithelia as well as for removal of the virus infected cells. We assessed the role of Fas/FasL-dependent pathway in apoptosis of genital epithelium during HSV-2 infection using a murine model of HSV-2 infection applied to C57BL6, MRL-Fas(lpr)/J (Fas-/-) and C3-Fasl(gld)/J (FasL-/-) mice and an in vitro model of HSV-2 infection in monocyte RAW 264.7 and keratinocyte 291.03C cell cultures and peritoneal macrophages. In contrast to keratinocyte in vitro cultures, HSV-2 infection of the monocytic cell cultures led to early induction of apoptosis. HSV-2 infection of peritoneal macrophages isolated from Fas- and FasL-deficient mice showed decreased activation of apoptosis, which could be further blocked by caspase-9 inhibitor. Infection of Fas and FasL-deficient mice increased the percentage of apoptotic cells and activation of caspase-9 in the vaginal tissue in comparison to C57BL6 wild type strain. Furthermore, Fas and FasL-deficient mice showed increased infiltration of neutrophiles in the vaginal mucosal epithelium at 3 and 7 day of infection in contrast to HSV-2 infected wild-type mice. Our results show that while the Fas/FasL pathway during HSV-2 infection of the vaginal epithelium plays an important role in controlling early local inflammatory response, mitochondrial apoptotic pathway also becomes activated by the inflammatory reaction.

HSV-2 regulates monocyte inflammatory response via the Fas/FasL pathway

Monocytic cells represent important cellular elements of the innate and adaptive immune responses in viral infections. We assessed the role of Fas/FasL in promoting monocyte apoptosis during HSV-2 infection by using an in vitro model based on the murine RAW 264.7 monocytic cell line and an in vivo murine model of HSV-2 infection applied to C57BL6, MRL-Fas^lpr/J (Fas−/−) and C3-Fasl^gld/J (FasL−/−) mice. HSV-2 infection of the monocytic cell line led to early induction of apoptosis, with no protective expression of anti-apoptotic Bcl-2. HSV-2 infected monocytes up-regulated Fas and FasL expression early during in vitro infection but were susceptible to Fas induced apoptosis. The vaginal monocytes in the HSV-2 murine model of infection up-regulated FasL expression and were susceptible to Fas induced apoptosis. HSV-2 infection of Fas and FasL- deficient mice led to decreased apoptosis of monocytes and impaired recruitment of NK, CD4+ and CD8+ T cells within the infection sites. The vaginal lavages of HSV-2 infected Fas and FasL- deficient showed decreased production of CXCL9, CXCL10 and TNF-α in comparison to HSV-2 infected wild-type mice strain. The decreased recruitment of immune competent cells was accompanied by delayed virus clearance from the infected tissue. Triggering of the Fas receptor on HSV-2 infected monocytes in vitro up-regulated the expression of CXCL9 chemokines and the cytokine TNF-α. Our study provides novel insights on the role of Fas/FasL pathway not only in apoptosis of monocytes but also in regulating local immune response by monocytes during HSV-2 infection.

Expression of inhibitor of growth 4 by HSV1716 improves oncolytic potency and enhances efficacy

We have isolated and characterized a novel variant of the replication-competent oncolytic HSV1716 that expresses inhibitor of growth 4 (Ing4) (HSV1716Ing4). We demonstrate that Ing4 expression enhances progeny output during HSV1716 infection of human tumor cells both in vitro and in vivo, thereby significantly augmenting its oncolytic potency. In tissue culture, compared with HSV1716, HSV1716Ing4 produced significantly higher numbers of infectious progeny in human squamous cell carcinoma (SCC), breast, ovarian, prostate and colorectal cancer cell lines. Immediate-early expression of Ing4 was crucial for this effect and an intact Ing4 was required as there was no enhanced progeny production with HSV1716 variants that expressed Ing4 mutants lacking the C-terminal plant homeodomain domain or conserved nuclear localization signals. In mouse xenograft models of SCC, ovarian and breast cancer, HSV1716Ing4 was significantly more efficacious than HSV1716 with at least 1000-fold more infectious virus found in tumors after HSV1716Ing4 treatment compared with tumors from HSV1716 treatment. Using a sensitive herpes simplex virus type 1 (HSV-1) PCR, virus DNA was only detected in tumors and was not detected in the DNA extracted from any organs of the injected mice demonstrating that, like HSV1716, HSV1716Ing4 replication is exclusively restricted to tumor cells. Our results suggest that the potential for enhanced tumor destruction by oncolytic HSV expressing Ing4 merits clinical investigation.

The virion host shutoff protein of herpes simplex virus 1 blocks the replication-independent activation of NF-κB in dendritic cells in the absence of type I interferon signaling

Immune evasion is a defining feature of the virus-host relationship. During infection, herpes simplex virus type 1 (HSV-1) utilizes multiple proteins to manipulate the host immune response. In the present study, we investigated the mechanism by which the virion host shutoff (vhs) protein blocks the activation of dendritic cells (DCs). Previously, we found that coinfection of wild-type HSV-1 with a panel of RNA viruses resulted in a block to DC activation that was attributable to vhs. These observations led us to hypothesize that the vhs-mediated inhibition was dependent on signaling through the RIG-I-like receptor (RLR) signaling pathway. By examining DCs generated from MAVS (IPS-1) knockout (KO) mice, we determined that RLR/MAVS signaling is not essential for the DC response to HSV-1. We also evaluated the requirement for the type I interferon (IFN) signaling pathway in DC activation following infection with HSV-1 and found that stimulation of DCs with wild-type HSV-1 required intact type I IFN signaling for the production of cytokines, whereas the vhs deletion (vhs(-)) mutant virus activated DCs without the need for exogenous IFN signaling. Comparisons of transcription factor activation in DCs infected with wild-type HSV and the vhs(-) mutant virus revealed that NF-κB activation was inhibited by vhs in the early phase of the infection. In contrast, IRF3 activation was not influenced by vhs. In these studies, measurement of proinflammatory cytokines and type I IFN release from the infected DCs reflected the activation status of these transcription factors. Taken together, the work presented here (i) describes a novel role for the vhs protein as an inhibitor of the early activation of NF-κB during HSV-1 infection of DCs and (ii) offers a mechanistic explanation of how this protein interferes with DC activation.

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.

Role of Fas/FasL in regulation of inflammation in vaginal tissue during HSV-2 infection

To assess the role of Fas in lesion development during genital HSV-2 infection, we used a well-established HSV-2 murine model applied to MRL-Fas(lpr)/J (Fas-/-) and C3-Fasl(gld)/J (FasL-/-) C57BL6 mice. In vitro infection of murine keratinocytes and epithelial cells was used to clarify molecular details of HSV-2 infection. Despite upregulation of Fas and FasL, HSV-2-infected keratinocytes and epithelial cells showed a moderate level of apoptosis due to upregulated expression of the anti-apoptotic factors Bcl-2, Akt kinase and NF-κB. Inflammatory lesions within the HSV-2-infected epithelium of C57BL6 mice consisted of infected cells upregulating Fas, FasL and Bcl-2, uninfected cells upregulating Fas and neutrophils expressing both Fas and FasL. Apoptosis was detected in HSV-2-infected cells and to even higher extent in non-infected cells surrounding HSV-2 infection sites. HSV-2 infection of Fas- and FasL-deficient mice led to increased apoptosis and stronger recruitment of neutrophils within the infection sites. We conclude that the Fas pathway participates in regulation of inflammatory response in the vaginal epithelium at the initial stage of HSV-2 infection.

Cellular players in the herpes simplex virus dependent apoptosis balancing act

Apoptosis is triggered as an intrinsic defense against numerous viral infections. Almost every virus encodes apoptotic modulators, and the herpes simplex viruses (HSV) are no exception. During HSV infection, there is an intricate balance between pro- and anti-apoptotic factors that delays apoptotic death until the virus has replicated. Perturbations in the apoptotic balance can cause premature cell death and have the potential to dramatically alter the outcome of infection. Recently, certain cellular genes have been shown to regulate sensitivity to HSV-dependent apoptosis. This review summarizes current knowledge of the cellular genes that impact the apoptotic balance during HSV infection.

Detection of herpes simplex virus dependent apoptosis

Subversion of the host response to virus infection is a universal theme of virology and viral immunology. Multiple mechanisms are in place to limit virus spread on behalf of the host, yet through evolution, viruses have adapted to either weaken or eliminate the effects of these host factors. Cell death or apoptosis is one such example of a host response to viral infection. As such, experimental techniques that enable analysis of viruses (and viral genes) involved in triggering, blocking, or perhaps augmenting this process represent important tools for virologists, immunologists, and cell biologists. Presented here are a series of techniques developed in our lab for the analysis of apoptosis that occurs as a consequence of herpes simplex virus type 1 infection.

The herpes simplex virus-induced demise of keratinocytes is associated with a dysregulated pattern of p63 expression

p63 plays a pivotal role in the development and maintenance of stratified epithelial tissues. In an effort to gain insight into the pathogenic mechanisms of skin infections caused by HSV-1 and HSV-2, we determined the patterns of p63 expression in primary keratinocytes and in the HaCaT cell line. The levels of DeltaNp63alpha and a 50kDa p73 isoform were decreased, Bax-alpha remained unaffected, while the expressions of the Bax-beta, TAp63gamma and a 44.5kDa p73 isoform were highly increased in both HSV-1-infected HaCaT cells and primary keratinocytes. In contrast, in response to HSV-2 infection the levels of DeltaNp63alpha, a 50kDa p73 isoform and a 44.5kDa p73 protein were decreased, Bax-alpha and TAp63gamma remained unaffected, while the expression of Bax-beta was slightly increased. The knockdown of TAp63 expression enhanced the viability of HSV-1-infected cells. Thus, HSV-1 and HSV-2 modulate the patterns of p63 and Bax expression in a serotype-specific manner. The dysregulated pattern of p63 expression observed in HSV-infected keratinocytes may comprise part of a mechanism by which these viruses perturb the functions of keratinocytes and lead to their demise.

TNF-alpha mediates pseudorabies virus-induced apoptosis via the activation of p38 MAPK and JNK/SAPK signaling

PRV infection causes apoptosis in vitro and in vivo. However, the significance of PRV-induced apoptosis and its signaling pathways is still unknown. This work investigates the role of MAPK pathways in mediating PRV-induced apoptosis. Flow cytometry, apoptosis ELISA and western blotting using antibodies against cleaved caspase-3, -6 and PARP demonstrated that PRV induces apoptosis in a time- and dose-dependent manner. p38 and JNK/SAPK inhibitors significantly protected cells from PRV-induced apoptosis. Inhibitor treatment did not affect Us3a gene transcription and progeny virus production. Western blotting revealed that PRV activates p38 and JNK/SAPK signaling. Inhibition of NF-kappaB had no effect on PRV-mediated apoptosis. Non-replicative PRV failed to activate p38 and JNK/SAPK or induce apoptosis. PRV infection increases TNF-alpha transcription, translation and secretion, as well as TNF-alpha receptor expression. Inhibition of p38 and JNK/SAPK reduced PRV-induced TNF-alpha up-regulation. Neutralization assay confirmed that TNF-alpha is a key mediator involved in PRV-induced apoptosis.

Bamboo culm extract supplementation elevates HDL-cholesterol and ameliorates oxidative stress in C57BL/6 mice fed atherogenic diet

Previously, we reported that bamboo culms possess a stronger antioxidative capacity than bamboo leaves in vitro. In this study, we investigated whether bamboo culm extract (BCE) supplementation ameliorates oxidative stress and hepatic nuclear factor kappaB (NF kappa B) activation in C57BL/6 mice fed an atherogenic diet. In addition, the effect of BCE supplementation on plasma lipid levels of the animals was tested. The mice were randomly assigned to a normal diet, an atherogenic diet (control), or an atherogenic diet supplemented with 1% (wt/wt) BCE or 3% (wt/wt) BCE for 16 weeks. Atherogenic diet-induced oxidative stress, measured by hepatic thiobarbituric acid-reactive substances and protein carbonyls, was significantly lower in the BCE-supplemented groups than in the control (P < .05). Total antioxidative capacity was elevated in the BCE groups, along with greater activities of antioxidative enzymes such as superoxide dismutase and catalase, compared to the control or normal groups (P < .05). The hepatic NF kappa B binding activities were significantly lower in the BCE groups as well (P < .05). The high-density lipoprotein-cholesterol level was significantly elevated by BCE supplementation (P < .05), whereas the effects of BCE on triglyceride and total cholesterol were inconsistent. Results from this study suggest that BCE supplementation may lessen oxidative stress via a series of changes, including a reinforced antioxidant system, and also suggest that the lowered oxidative stress status may down-regulate the activation of inflammatory mediators.

Herpesvirus tegument protein activates NF-kappaB signaling through the TRAF6 adaptor protein

Viruses remodel the host cell to optimize their replication both by delivery of virion proteins into the cell and by de novo expression of viral proteins. The HSV particle contains several proteins that function to prepare the host cell for viral replication, including the VP16 transcriptional activator protein and virion host shutoff protein. HSV infection activates NF-kappaB pathways through Toll-like receptor (TLR) 2 and non-TLR pathways, and NF-kappaB activity is required for efficient viral replication. In a screen of the HSV proteome, we observed that the HSV U(L)37 tegument protein activates NF-kappaB signaling in a TLR2-independent manner. Expression of U(L)37 in transfected cells leads to IkappaB degradation and activation of both reporter genes and the endogenous IL-8 gene. This activation requires TNF receptor-associated factor 6 (TRAF6), and U(L)37 contains a TRAF6-binding domain that is required for interaction with TRAF6 and activation of NF-kappaB. A mutant virus encoding U(L)37 with an altered TRAF6-binding site shows reduced NF-kappaB activation in the early phase of infection. Therefore, the HSV U(L)37 virion structural protein can activate NF-kappaB through TRAF6. Activation of NF-kappaB by a virion tegument protein that is delivered into the host cell cytoplasm during viral entry represents a mechanism for activation of this pathway by a virus.

Herpes simplex virus type 1 ICP4 deletion mutant virus d120 infection failed to induce apoptosis in nerve growth factor-differentiated PC12 cells

It has been suggested that terminally differentiated neuronal cells and mitotic cells respond differently in many aspects to herpes simplex virus type 1 (HSV-1) infection. The ICP4-deleted, Us3-defective, HSV-1 mutant strain d120 induces classical apoptosis in a variety of mitotic cell lines. Its behavior in postmitotic cells is not known. Here the authors report that mutant d120 virus failed to induce apoptosis in neuronal-like, nerve growth factor (NGF)-differentiated PC12 cells. More strikingly, rather than inducing apoptosis, d120 infection prolonged the life of nondividing NGF-differentiated PC12 cells in the culture flask. The virus genome had a half-life of 30 days. Unlike in other cells, such as Vero, neither wild-type nor d120 infection of NGF-differentiated PC12 cells induced the nuclear factor (NF)-kappa B p65 pathway, which has been associated with virus-induced apoptosis. Thus, the authors demonstrate, for the first time, that a potent apoptosis inducer mutant d120 failed to induce apoptosis in neuronal-like NGF-differentiated PC12 cells, unlike a number of other cell lines studied. The possible mechanisms involved in the failure of d120 to induce apoptosis in neuronal-like NGF-differentiated PC12 cells are discussed.

Susceptibility of cancer cells to herpes simplex virus-dependent apoptosis

Apoptosis has recently been associated with herpes simplex virus 1 (HSV-1) latency and disease severity. There is an intricate balance between pro- and anti-apoptotic processes during HSV-1 infection. When anti-apoptotic pathways are suppressed, this balance is upset and the cells die by apoptosis, referred to here as HSV-1-dependent apoptosis (HDAP). It has been observed previously that HeLa cancer cells exhibit an enhanced sensitivity to HDAP. Here, a series of specific patient-derived cancer cells was utilized to investigate the cell-type specificity of HDAP. The results showed that a human mammary tumour cell line was sensitive to HDAP, whilst syngeneic normal cells were resistant. Furthermore, low-passage-number primary human mammary epithelial cells were resistant to HDAP. When the susceptibility of human colon, brain, breast and cervical cancer cells was assessed, the only cells insensitive to HDAP were those resistant to all environmental stimuli tested. This implies that the HDAP resistance was probably due to mutations in the cellular apoptotic machinery. Thus, the susceptibility of cancer cells to HDAP requires that they possess a functional ability to undergo programmed cell death.

Herpes simplex virus blocks Fas-mediated apoptosis independent of viral activation of NF-kappaB in human epithelial HEp-2 cells

The goal of our study was to characterize the apoptotic response of herpes simplex virus (HSV)-infected, human epithelial HEp-2 cells to extrinsic treatments through the Fas receptor. Initially, we defined the Fas response of these cells. We found the following: (1) Treatment of HEp-2 cells with anti-Fas antibody or Fas ligand (FasL) alone did not induce apoptosis. (2) In addition, these inducers did not activate NF-kappaB in these cells. (3) The addition of cycloheximide (CHX) during these treatments caused a dramatic increase in programmed cell death. (4) HEp-2 cells infected with HSV for 6 h prior to anti-Fas plus CHX treatment were nonapoptotic, and (5) these cells possessed nuclear NFkappaB. (6) HSV blocked anti-Fas or FasL plus CHX-induced apoptosis in HEp-2 cells that stably expressed a dominant-negative form of IkappaBalpha. These results indicate that HSV infection can block the process of Fas-mediated apoptosis through a mechanism that is independent of viral activation of NFkappaB. Our findings help define the molecular mechanisms involved in HSV evasion of the cytokine-driven, innate immune response in human epithelial cells.

Herpes simplex virus blocks apoptosis by precluding mitochondrial cytochrome c release independent of caspase activation in infected human epithelial cells

Expression of HSV-1 genes leads to the induction of apoptosis in human epithelial HEp-2 cells but the subsequent synthesis of infected cell protein prevents the process from killing the cells. Thus, viruses unable to produce appropriate prevention factors are apoptotic. We now report that the addition of either a pancaspase inhibitor or caspase-9-specific inhibitor prevented cells infected with an apoptotic HSV-1 virus from undergoing cell death. This result indicated that HSV-1-dependent apoptosis proceeds through the mitochondrial apoptotic pathway. However, the pancaspase inhibitor did not prevent the release of cytochrome c from mitochondria, implying that caspase activation is not required for this induction of cytochrome c release by HSV-1. The release of cytochrome c was first detected at 9 hpi while caspase-9, caspase-3 and PARP processing were detected at 12 hpi. Finally, Bax accumulated at mitochondria during apoptotic, but not wild type HSV-1 infection. Together, these findings indicate that HSV-1 blocks apoptosis by precluding mitochondrial cytochrome c release in a caspase-independent manner and suggest Bax as a target in infected human epithelial cells.

ICP0 gene expression is a herpes simplex virus type 1 apoptotic trigger

Apoptosis is a highly regulated programmed cell death process which is activated during normal development and by various stimuli, such as viral infection, which disturb cellular metabolism and physiology. That herpes simplex virus type 1 (HSV-1) induces apoptosis but then prevents its killing of infected cells is well-established. However, little is known about the viral factor/event which triggers the apoptotic process. We previously reported that infections with either (i) a temperature-sensitive virus at its nonpermissive temperature which does not inject viral DNA into nuclei or (ii) various UV-inactivated wild-type viruses do not result in the induction of apoptosis (C. M. Sanfilippo, F. N. W. Chirimuuta, and J. A. Blaho, J. Virol. 78:224-239, 2004). This indicates that virus receptor binding/attachment to cells, membrane fusion, virion disassembly/tegument dispersal, virion RNAs, and capsid translocation to nuclei are not responsible for induction and implicates viral immediate-early (IE) gene expression in the process. Here, we systematically evaluated the contribution of each IE gene to the stimulation of apoptosis. Using a series of viruses individually deleted for alpha27, alpha4, and alpha22, we determined that these genes are not required for apoptosis induction but rather that their products play roles in its prevention, likely through regulatory effects. Sole expression of alpha0 acted as an "apoptoxin" that was necessary and sufficient to trigger the cell death cascade. Importantly, results using a recombinant virus which contains a stop codon in alpha0 showed that it was not the ICP0 protein which acted as the apoptotic inducer. Based on these findings, we propose that alpha0 gene expression acts as an initial inducer of apoptosis during HSV-1 infection. This represents the first description of apoptosis induction in infected cells triggered as a result of expression of a single viral gene. Expression of apoptotic viral genes is a unique mechanism through which human pathogens may modulate interactions with their host cells.

Apoptosis During Herpes Simplex Virus Infection

Herpes simplex virus (HSV) infection triggers apoptosis in infected cells. However, proteins synthesized later in infected cells prevent apoptotic cell death from ensuing. In vivo data showing that apoptosis accompanies herpes stromal keratitis and encephalitis suggest that apoptotic modulation plays a role in the development of herpetic disease. Tremendous progress has been made toward identifying the viral factors that are responsible for inducing and inhibiting apoptosis during infection. However, the mechanisms whereby they act are still largely unknown. Recent studies have illustrated a wide diversity in the cellular response to HSV-triggered apoptosis, emphasizing the importance of host factors in this process. Together, these findings indicate that apoptosis during HSV infection represents an important virus-host interaction process, which likely influences viral pathogenesis.