Herpes simplex virus selectively induces expression of the CC chemokine RANTES/CCL5 in macrophages through a mechanism dependent on PKR and ICP0

HSV-1 infection-induced herpetic neuralgia involves a CCL5/CCR5-mediated inflammation mechanism

Herpetic-related neuralgia (HN) caused by varicella-zoster virus (VZV) infection is one of the most typical and common neuropathic pain in the clinic. However, the potential mechanisms and therapeutic approaches for the prevention and treatment of HN are still unclear. This study aims to provide a comprehensive understanding of the molecular mechanisms and potential therapeutic targets of HN. We used an HSV-1 infection-induced HN mouse model and screened the differentially expressed genes (DEGs) in the DRG and spinal cord using an RNAseq technique. Moreover, bioinformatics methods were used to figure out the signaling pathways and expression regulation patterns of the DEGs enriched. In addition, quantitative real-time RT-PCR and western blot were carried out to further confirm the expression of DEGs. HSV-1 inoculation in mice resulted in mechanical allodynia, thermal hyperalgesia, and cold allodynia, following the infection of HSV-1 in both DRG and spinal cord. Besides, HSV-1 inoculation induced an up-regulation of ATF3, CGRP, and GAL in DRG and activation of astrocytes and microglia in the spinal cord. Moreover, 639 genes were upregulated, 249 genes were downregulated in DRG, whereas 534 genes were upregulated and 12 genes were downregulated in the spinal cord of mice 7 days after HSV-1 inoculation. GO and KEGG enrichment analysis suggested that immune responses and cytokine-cytokine receptor interaction are involved in DRG and spinal cord neurons in mice after HSV-1 infection. In addition, CCL5 and its receptor CCR5 were significantly upregulated in DRG and spinal cord upon HSV-1 infection in mice. And blockade of CCR5 exhibited a significant analgesic effect and suppressed the upregulation of inflammatory cytokines in DRG and spinal cord induced by HSV-1 infection in mice. HSV-1 infection-induced allodynia and hyperalgesia in mice through dysregulation of immune response and cytokine-cytokine receptor interaction mechanism. Blockade of CCR5 alleviated allodynia and hyperalgesia probably through the suppression of inflammatory cytokines. Therefore, CCR5 could be a therapeutic target for the alleviation of HSV-1 infection-induced HN.

Seneca Valley virus induces proinflammatory cytokine and chemokine response in vitro

Seneca Valley virus (SVV) is an oncolytic virus, which belongs to the Picornaviridae family, that causes blisters on the nose and hooves, affecting the production performance of pigs. However, the function of proinflammatory cytokines and chemokines in SVV infection is still unclear. In our study, SVV infection could induce a high expression of proinflammatory cytokines interleukin (IL)-1α, IL-1β, and tumor necrosis factor α (TNF-α) and chemokines, including chemokine (C-C motif) ligand 2 (CCL2), chemokine (C-C motif) ligand 5 (CCL5), and chemokine (C-X-C motif) ligand 10 (CXCL10). Interfered genes of IL-1α, IL-1β, and TNF-α inhibited virus replication, but interfered genes of CCL2, CCL5, and CXCL10 promoted virus replication. These results indicate that proinflammatory cytokines and chemokines are involved in SVV infection; this will be beneficial to explore the pathogenesis and cytokine therapy of SVV.

Cytomegalovirus and herpes simplex type 1 infections and immunological profile of community-dwelling older adults

Chronic infections, such as cytomegalovirus (CMV) and herpes simplex virus type 1 (HSV-1), contribute to the inflammation process among older adults and are associated with the immunosenescence process. The aim was to identify the immunological profile associated with CMV and HSV-1 infections among older adults. This is a cross-sectional study, carried out with 1492 participants from the Bambuí Cohort Study of Aging - Minas Gerais, Brazil. For analysis purposes, we considered the presence of immunoglobulin G (IgG) for CMV and HSV-1 in the participants' serum, assessed by the enzyme-linked immunosorbent assay (ELISA); outcomes were defined by titration above the median (>160 UR/mL for HSV-1 and >399.5 U/mL for CMV). In order to assess the immunological profile, the following biomarkers were considered: IL-1beta, IL-10, IL-12, TNF, CXCL8, CXCL9, CXCL10, CCL2, CCL5, IL-6 and CRP; the first four being categorized as detectable levels or not, and the others using the Classification and Regression Tree (CART) method. The analysis was adjusted for sociodemographic variables, health behaviors and health conditions. The seroprevalence of anti CMV and anti HSV-1 antibodies was 99.4% and 97.0%, respectively. Higher concentrations of CXCL8 and CCL5 chemokines were associated with lower antibody titers for CMV, and higher concentrations of CXCL9, IL-6 and CRP were associated with higher levels of antibodies to CMV. Moreover, intermediate levels of CXCL10 were also associated with higher levels of antibodies to CMV. In HSV-1 infection, intermediate levels of CXCL9, CCL5 and IL-6 were less likely to have higher antibody titers for this infection. On the other hand, higher levels of CXCL10 and CRP were positively associated with higher antibody titers for HSV-1. The results describe important immunological changes and reinforce the potential effect of CMV and HSV-1 on the immunosenescence process.

Reprint of: Alterations of TRIM21-mRNA expression during monocyte maturation

Tripartite motif-containing protein 21 (TRIM21) play a dual role in the cytoplasm of the cells where it facilitates destruction of some antibody-coated viruses and some bacteria, and initiates synthesis of proinflammatory cytokines. Macrophages and CD16⁺ monocyte subset can particularly participate in a proinflammatory response caused by viral infection, however, the molecular mechanisms underlying these processes are not fully understood. The aim of this study was to determine the level of TRIM21-mRNA expression in monocyte subsets including: classical (CD14⁺⁺CD16^-), intermediate (CD14⁺⁺CD16⁺) and non-classical (CD14⁺CD16⁺⁺) monocytes, as well as during in vitro differentiation of the isolated monocytes towards dendritic cells or macrophages. Our results revealed that the level of TRIM21 mRNA expression was significantly lower in CD16- monocytes, when compared to CD16⁺ cells and the whole monocyte population, yet no significant differences were observed when CD16⁺ population was divided into intermediate and non-classical subsets. More pronounced differences were observed in the case of monocyte-derived macrophages (MDM) and dendritic cells (DCs). TRIM21-mRNA expression level was app. 6-fold higher in DCs, and app. 16-fold higher in MDM (p<0,01), when compared to freshly isolated monocytes. Our results may suggest the new mechanism of increased proinflammatory cytokine production by CD16⁺ (intermediate and non-classical) monocytes and macrophages, at least in patients with acute or chronic infections, caused by enveloped viruses. We suggest that TRIM21 may be one of the factors associated with the "switching on" the proinflammatory programme in CD16⁺ monocytes or monocyte-derived macrophages.

Alterations of TRIM21-mRNA expression during monocyte maturation

Tripartite motif-containing protein 21 (TRIM21) play a dual role in the cytoplasm of the cells where it facilitates destruction of some antibody-coated viruses and some bacteria, and initiates synthesis of proinflammatory cytokines. Macrophages and CD16⁺ monocyte subset can particularly participate in a proinflammatory response caused by viral infection, however, the molecular mechanisms underlying these processes are not fully understood. The aim of this study was to determine the level of TRIM21-mRNA expression in monocyte subsets including: classical (CD14⁺⁺CD16^-), intermediate (CD14⁺⁺CD16⁺) and non-classical (CD14⁺CD16⁺⁺) monocytes, as well as during in vitro differentiation of the isolated monocytes towards dendritic cells or macrophages. Our results revealed that the level of TRIM21 mRNA expression was significantly lower in CD16- monocytes, when compared to CD16⁺ cells and the whole monocyte population, yet no significant differences were observed when CD16⁺ population was divided into intermediate and non-classical subsets. More pronounced differences were observed in the case of monocyte-derived macrophages (MDM) and dendritic cells (DCs). TRIM21-mRNA expression level was app. 6-fold higher in DCs, and app. 16-fold higher in MDM (p<0,01), when compared to freshly isolated monocytes. Our results may suggest the new mechanism of increased proinflammatory cytokine production by CD16⁺ (intermediate and non-classical) monocytes and macrophages, at least in patients with acute or chronic infections, caused by enveloped viruses. We suggest that TRIM21 may be one of the factors associated with the "switching on" the proinflammatory programme in CD16⁺ monocytes or monocyte-derived macrophages.

Oncolytic herpes simplex virus interactions with the host immune system

Oncolytic viruses (OVs), like oncolytic herpes simplex virus (oHSV), are genetically engineered to selectively replicate in and kill cancer cells, while sparing normal cells. Initial OV infection, cell death, and subsequent OV propagation within the tumor microenvironment leads to a cascade of host responses (innate and adaptive), reflective of natural anti-viral immune responses. These host-virus interactions are critical to the balance between OV activities, anti-viral immune responses limiting OV, and induction of anti-tumor immunity. The host response against oHSV is complex, multifaceted, and modulated by the tumor microenvironment and immunosuppression. As a successful pathogen, HSV has multiple mechanisms to evade such host responses. In this review, we will discuss these mechanisms and HSV evasion, and how they impact oHSV therapy.

Characteristic Cytokine and Chemokine Profiles in Encephalitis of Infectious, Immune-Mediated, and Unknown Aetiology

Background

Encephalitis is parenchymal brain inflammation due to infectious or immune-mediated processes. However, in 15–60% the cause remains unknown. This study aimed to determine if the cytokine/chemokine-mediated host response can distinguish infectious from immune-mediated cases, and whether this may give a clue to aetiology in those of unknown cause.

Methods

We measured 38 mediators in serum and cerebrospinal fluid (CSF) of patients from the Health Protection Agency Encephalitis Study. Of serum from 78 patients, 38 had infectious, 20 immune-mediated, and 20 unknown aetiology. Of CSF from 37 patients, 20 had infectious, nine immune-mediated and eight unknown aetiology.

Results

Heat-map analysis of CSF mediator interactions was different for infectious and immune-mediated cases, and that of the unknown aetiology group was similar to the infectious pattern. Higher myeloperoxidase (MPO) concentrations were found in infectious than immune-mediated cases, in serum and CSF (p = 0.01 and p = 0.006). Serum MPO was also higher in unknown than immune-mediated cases (p = 0.03). Multivariate analysis selected serum MPO; classifying 31 (91%) as infectious (p = 0.008) and 17 (85%) as unknown (p = 0.009) as opposed to immune-mediated. CSF data also selected MPO classifying 11 (85%) as infectious as opposed to immune-mediated (p = 0.036). CSF neutrophils were detected in eight (62%) infective and one (14%) immune-mediated cases (p = 0.004); CSF MPO correlated with neutrophils (p<0.0001).

Conclusions

Mediator profiles of infectious aetiology differed from immune-mediated encephalitis; and those of unknown cause were similar to infectious cases, raising the hypothesis of a possible undiagnosed infectious cause. Particularly, neutrophils and MPO merit further investigation.

Proinflammatory cytokines and chemokines - but not interferon-β - produced in response to HSV-2 in primary human genital epithelial cells are associated with viral replication and the presence of the virion host shutoff protein

PROBLEM

It is unknown whether viral replication or viral components that subvert innate responses in other cells, specifically the virion host shutoff (VHS) protein, play a role in determining primary genital epithelial cell (GEC) innate antiviral responses.

METHOD OF STUDY

Cultures of primary female GECs were exposed to wildtype (WT), VHS-deleted (vhsB), or UV-inactivated HSV-2. Antiviral pathway induction was evaluated by measuring nuclear factor-κB (NFκB) translocation by immunofluorescent microscopy. Proinflammatory cytokines, chemokines, and interferon (IFN) were measured by Luminex or ELISA. Biological activity of IFN-β was evaluated via VSV-GFP bioassay, by blocking secreted IFN-β with neutralizing antibodies and by measuring interferon-stimulated genes by RT-PCR.

RESULTS

Proinflammatory cytokines and chemokines were upregulated in primary GECs in response to replication-competent HSV-2, but suppressed in the presence of the VHS protein. In contrast, upregulation of IFN-β depended on viral replication, but was not affected by VHS. However, the IFN-β produced was biologically active and reduced the viral burden.

CONCLUSION

Viral factors such as replication and the presence of the VHS protein play important roles in regulating innate antiviral responses against HSV-2 from primary GECs.

Learning from the messengers: innate sensing of viruses and cytokine regulation of immunity - clues for treatments and vaccines

Virus infections are a major global public health concern, and only via substantial knowledge of virus pathogenesis and antiviral immune responses can we develop and improve medical treatments, and preventive and therapeutic vaccines. Innate immunity and the shaping of efficient early immune responses are essential for control of viral infections. In order to trigger an efficient antiviral defense, the host senses the invading microbe via pattern recognition receptors (PRRs), recognizing distinct conserved pathogen-associated molecular patterns (PAMPs). The innate sensing of the invading virus results in intracellular signal transduction and subsequent production of interferons (IFNs) and proinflammatory cytokines. Cytokines, including IFNs and chemokines, are vital molecules of antiviral defense regulating cell activation, differentiation of cells, and, not least, exerting direct antiviral effects. Cytokines shape and modulate the immune response and IFNs are principle antiviral mediators initiating antiviral response through induction of antiviral proteins. In the present review, I describe and discuss the current knowledge on early virus–host interactions, focusing on early recognition of virus infection and the resulting expression of type I and type III IFNs, proinflammatory cytokines, and intracellular antiviral mediators. In addition, the review elucidates how targeted stimulation of innate sensors, such as toll-like receptors (TLRs) and intracellular RNA and DNA sensors, may be used therapeutically. Moreover, I present and discuss data showing how current antimicrobial therapies, including antibiotics and antiviral medication, may interfere with, or improve, immune response.

Herpesviral infection and Toll-like receptor 2

In the last decade, substantial progress has been made in understanding the molecular mechanisms involved in the initial host responses to viral infections. Herpesviral infections can provoke an inflammatory cytokine response, however, the innate pathogen-sensing mechanisms that transduce the signal for this response are poorly understood. In recent years, it has become increasingly evident that the Toll-like receptors (TLRs), which are germline-encoded pattern recognition receptors (PRRs), function as potent sensors for infection. TLRs can induce the activation of the innate immunity by recruiting specific intracellular adaptor proteins to initiate signaling pathways, which then culminating in activation of the nuclear factor kappa B (NF-κB) and interferon-regulatory factors (IRFs) that control the transcription of genes encoding type I interferon (IFN I) and other inflammatory cytokines. Furthermore, activation of innate immunity is critical for mounting adaptive immune responses. In parallel, common mechanisms used by viruses to counteract TLR-mediated responses or to actively subvert these pathways that block recognition and signaling through TLRs for their own benefit are emerging. Recent findings have demonstrated that TLR2 plays a crucial role in initiating the inflammatory process, and surprisingly that the response TLR2 triggers might be overzealous in its attempt to counter the attack by the virus. In this review, we summarize and discuss the recent advances about the specific role of TLR2 in triggering inflammatory responses in herpesvirus infection and the consequences of the alarms raised in the host that they are assigned to protect.

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.

Functional characterization of the CC chemokine RANTES from Pekin duck (Anas platyrhynchos)

RANTES (Regulated upon Activation, Normal T-cell Expressed and Secreted) is a key pro-inflammatory cytokine that belongs to the CC-group of chemokines. The present study was carried out to functionally characterize the previously identified RANTES homologue in domestic duck (GenBank Accession No. AY641435). Recombinant duck RANTES was expressed in Escherichia coli-based and HEK293T cell-based systems. A tRNA supplementation strategy was required to express the protein in E. coli due to the presence of rare codons. In biological assays using HEK293T cell-expressed protein, RANTES was found to mediate chemotaxis of DT-40 chicken B cells and primary duck splenocytes at a concentration of 0.505μg/ml (0.6μM). Immunostaining of the migrated splenocytes using anti-duck CD4 and CD8 monoclonal antibodies and subsequent flow cytometric analysis showed enhanced chemotaxis of CD8+ cells. The recombinant RANTES exhibited in vitro antiviral activity by inhibiting infection of chicken embryo fibroblast cells with duck enteritis virus (DEV) at the same concentration. The effect could be neutralized by rabbit anti-duck RANTES polyclonal serum. The mechanism seems to be direct on viral particles as evidenced by the need for co-incubation of RANTES with DEV prior to the infection for antiviral activity, and also by the enhanced binding of DEV to E. coli expressed purified RANTES on ELISA-based assays. Our results show that the duck RANTES has overlapping biological properties with its mammalian orthologue, and also has possible functional cross-reactivity with chicken immune cells indicated by the chemotaxis of DT-40 cells.

Trichosanthin affects HSV-1 replication in Hep-2 cells

Trichosanthin (TCS) is a type I ribosome-inactivating protein that inhibits the replication of both human immunodeficiency virus type 1 (HIV-1) and herpes simplex virus type 1 (HSV-1). The mechanism of inhibition is not clear. This investigation explored the effects of TCS on the stages of HSV-1 infection in Hep-2 cells, from attachment to release. We demonstrated that TCS reduced HSV-1 antigen and DNA content and interfered with viral replication as early as 3-15 h after infection. TCS had no effect on HSV-1 attachment, penetration or immediate-early gene expression. However, the expression of early and late genes and virion release were diminished. In summary, this study demonstrates that TCS primarily affects HSV-1 replication in Hep-2 cells during the early to late infection period.

Activation and evasion of innate antiviral immunity by herpes simplex virus

Herpes simplex virus (HSV), a human pathogenic virus, has evolved several strategies to evade the production and function of interferons (IFNs) and cytokines generated by the innate immune system to restrict the virus. Equilibrium exists between the virus and the immune response, and a shift in this delicate balance either restricts the virus or enhances virus spread and tissue damage. Therefore, understanding of the cytokine response generated after HSV infection and the underlying virus-cell interactions is essential to improve our understanding of viral pathogenesis. This review summarizes the current knowledge on induction and evasion of the innate immune response by HSV.

Activation of host antiviral RNA-sensing factors necessary for herpes simplex virus type 1-activated transcription of host cell fucosyltransferase genes FUT3, FUT5, and FUT6 and subsequent expression of sLe(x) in virus-infected cells

Herpes simplex virus type 1 (HSV-1) induces expression of a selectin receptor, the carbohydrate epitope sialyl Lewis X (sLe(x)), at the surface of infected cells. The molecular background to this phenomenon is that a viral immediate early RNA interacts with as yet unidentified host factors, eventually resulting in transcription of three dormant host fucosyltransferase genes (FUT3, FUT5, and FUT6), whose gene products are rate-limiting for synthesis of sLe(x). The aim of the present study was to define the immediate targets for the viral RNA in this process. We found that the Protein Kinase R (PKR) inhibitors 2-aminopurine (2-AP) and C16 inhibited FUT3, FUT5, and FUT6 expression as well as HSV-1-induced expression of sLe(x), indicating a primary role of PKR as a viral RNA target. The PKR-dependent activation of the FUT genes seemed neither to involve PKR effects on translation nor to involve NF-kappaB- or JNK-dependent activation. IMD-0354, known as an inhibitor of the NF-kappaB-activating factor IKK-2, induced FUT transcription via a novel IKK-2-independent mechanism, irrespective of whether the cells were virus-infected or not. Altogether, the results suggested that PKR is the primary target for HSV-1 early RNA during induction of FUT3, FUT5, and FUT6, and that the subsequent steps in the transcriptional activation of these host genes involve a hitherto unknown IMD-0354, yet IKK-2-independent, pathway.

The immune response to herpes simplex virus encephalitis in mice is modulated by dietary vitamin E

Herpes simplex virus encephalitis (HSE) is the most common fatal sporadic encephalitis in humans. HSE is primarily caused by herpes simplex virus (HSV)-1 infection of the brain. HSE results in increased levels of oxidative stress, including the production of reactive oxygen species, free radicals, and neuroinflammation. The most biologically active form of vitamin E (VE) is alpha-tocopherol (alpha-TOC). In cellular membranes, alpha-TOC prevents lipid peroxidation by scavenging free radicals and functioning as an antioxidant. Supplementation with VE has been shown to decrease immunosenescence, improve immune function, and may be neuroprotective. To determine how VE deficiency and VE supplementation would alter the pathogenesis of HSE, we placed weanling male BALB/cByJ mice on VE-deficient (VE-D), VE-adequate (VE-A), or 10x VE-supplemented diets for 4 wk, and then infected the mice intranasally with HSV-1. VE-D mice had more severe symptoms of encephalitis than VE-A mice, including weight loss, keratitis, hunched posture, and morbidity. VE-D mice had increased cytokine and chemokine expression in the brain and increased viral titers. In contrast, VE supplementation failed to decrease cytokine production and had no effect on viral titer. We demonstrated that adequate levels of VE are important in limiting HSE pathology and that 10x supplementation does not enhance protection.

Induction of interleukin-6 in human retinal epithelial cells by an attenuated Herpes simplex virus vector requires viral replication and NFkappaB activation

Gene delivery has potential for treating ocular disease and a number of delivery systems have been tested in animal models. However, several viral vectors have been shown to trigger undesirable transient inflammatory responses in the eye. Previously, it was shown that an attenuated Herpes simplex virus vector (hrR3) transduced numerous cell types in the anterior and posterior segments of monkey eyes, but this was accompanied by inflammation. In the retina, retinal pigment epithelial cells were the predominant cell type transduced by hrR3. IL-6 is an important pro-inflammatory cytokine and may play a role in the response to the hrR3 vector. Infection of human ARPE-19 cells with hrR3 resulted in increased IL-6 expression and secretion 3-4h post-infection. In the presence of acyclovir (70 microM) or in cells infected with UV-inactivated hrR3, IL-6 was not up-regulated indicating viral replication was required. Expression of the HSV-1 alpha and beta genes may be necessary but was not sufficient for NF-kappaB activation and IL-6 up-regulation. The translocation of NF-kappaB into the nucleus also occurred between 3 and 4h post-infection, coincident with increased IL-6 expression. Inhibition of NF-kappaB translocation by an Adenovirus vector expressing a dominant negative IkappaB (AdIkappaBam) inhibited IL-6 up-regulation, indicating that NF-kappaB plays a role in increasing IL-6 expression in APRE-19 cells. The hrR3 virus lacks viral ribonucleotide reductase (RR) activity, thus RR is not required for NF-kappaB activation or IL-6 up-regulation in ARPE-19 cells.

Presence of HSV-1 immediate early genes and clonally expanded T-cells with a memory effector phenotype in human trigeminal ganglia

The latent persistence of herpes simplex virus type 1 (HSV-1) in human trigeminal ganglia (TG) is accompanied by a chronic CD8 T-cell infiltrate. The focus of the current work was to look for HSV-1 transcription activity as a potential trigger of the immune response and to characterize the immune cell infiltrates by this feature. We combined in situ hybridization, laser cutting microscopy, and single cell RT-PCR to demonstrate the expression of the HSV-1 immediate early (IE) genes ICP0 and ICP4 in human trigeminal neurons. Using CDR3 spectratyping, we showed that the infiltrating T-cells are clonally expanded, indicating an antigen-driven immune response. Moreover, the persisting CD8+ T-cells had features of the memory effector phenotype. The voltage-gated potassium channel Kv1.3, a marker of chronic activated memory effector cells, and the chemokines CCL5 and CXCL10 were expressed by a subpopulation of infiltrating cells. The corresponding chemokine receptors CCR5 and CXCR3 were co-expressed on virtually all CD8 T-cells. In addition, T-cells expressed granzymes and perforin. In contrast to animal models of HSV-1 latency, hardly any FoxP3-positive regulatory T-cells were detected in human TG. Thus, HSV-1 IE genes are expressed in human TG and the infiltrating T-cells bear several characteristics that suggest viral antigenic stimulation.

Herpes simplex virus and the chemokines that mediate the inflammation

Herpes simplex viruses (HSV) are highly pervasive pathogens in the human host with a seroconversion rate upwards of 60% worldwide. HSV type 1 (HSV-1) is associated with the disease herpetic stromal keratitis, the leading cause of infectious corneal blindness in the industrialized world. Individuals suffering from genital herpes associated with HSV type 2 (HSV-2) are found to be two- to threefold more susceptible in acquiring human immunodeficiency virus (HIV). The morbidity associated with these infections is principally due to the inflammatory response, the development of lesions, and scarring. Chemokines have become an important aspect in understanding the host immune response to microbial pathogens due in part to the timing of expression. In this paper, we will explore the current understanding of chemokine production as it relates to the orchestration of the immune response to HSV infection.

Distinct roles of protein kinase R and toll-like receptor 3 in the activation of astrocytes by viral stimuli

Impaired immune surveillance and constitutive immunosuppressive properties make the central nervous system (CNS) a particular challenge to immune defense, and require that CNS-resident cells be capable of rapidly recognizing and responding to infection. We have previously shown that astrocytes respond to treatment with a TLR3 ligand, poly I:C, with the upregulation of innate immune functions. In the current study, we examine the activation of innate immune functions of astrocytes by Theiler's murine encephalomyelitis virus (TMEV), a picornavirus, which establishes a persistent infection in the CNS of susceptible strains of mice and leads to the development of an autoimmune demyelinating disease that resembles human multiple sclerosis. Astrocytes infected with TMEV are activated to produce type I interferons, the cytokine IL-6, and chemokines CCL2 and CXCL10. We further examined the mechanisms that are responsible for the activation of astrocytes in response to direct viral infection and treatment with poly I:C. We found that the cytoplasmic dsRNA-activated kinase PKR is important for innate immune responses to TMEV infection, but has no role in their induction by poly I:C delivered extracellularly. In contrast, we found that TLR3 has only a minor role in responses to TMEV infection, but is important for responses to poly I:C. These results highlight the differences between responses induced by direct, nonlytic virus infection and extracellular poly I:C. The activation of astrocytes through these different pathways has implications for the initiation and progression of viral encephalitis and demyelinating diseases such as multiple sclerosis.

Latency of alpha-herpes viruses is accompanied by a chronic inflammation in human trigeminal ganglia but not in dorsal root ganglia

The immune response to latent herpesvirus infections was compared in human trigeminal ganglia (TG) and dorsal root ganglia (DRG) of 15 dead individuals. On the basis of our previous findings, we hypothesized that T-cells would be attracted to sensory neurons latently infected with herpes simplex virus type 1 (HSV-1), but not to those harboring latent varicella zoster virus (VZV). We showed that the TG contain a positive hybridization signal for HSV-1 latency-associated transcript (LAT), whereas the DRG from the same individuals lack detectable LAT. In contrast, immunohistochemistry revealed that latent VZV protein 62 stained positive in the vast majority of all tested TG and DRG. T-cell infiltrates prominently surrounded individual neurons in the TG but not in the DRG. TaqMan polymerase chain reaction also showed higher expression of CD8 and RANTES transcripts in the TG versus DRG. Only the infiltrates in the TG, but not in the DRG, produced RANTES at the protein level. Because it has been shown that RANTES protein is produced only after T-cell receptor stimulation, we assume that T-cell infiltration is associated with antigen recognition in the TG but not in the DRG.

Herpes simplex virus type 1 ICP27-dependent activation of NF-kappaB

The ability of herpes simplex virus type 1 (HSV-1) to activate NF-kappaB has been well documented. Beginning at 3 to 5 h postinfection, HSV-1 induces a robust and persistent nuclear translocation of an NF-kappaB-dependent (p50/p65 heterodimer) DNA binding activity, as measured by electrophoretic mobility shift assay. Activation requires virus binding and entry, as well as de novo infected-cell protein synthesis, and is accompanied by loss of both IkappaBalpha and IkappaBbeta. In this study, we identified loss of IkappaBalpha as a marker of NF-kappaB activation, and infection with mutants with individual immediate-early (IE) regulatory proteins deleted indicated that ICP27 was necessary for IkappaBalpha loss. Analysis of both N-terminal and C-terminal mutants of ICP27 identified the region from amino acids 21 to 63 as being necessary for IkappaBalpha loss. Additional experiments with mutant viruses with combinations of IE genes deleted revealed that the ICP27-dependent mechanism of NF-kappaB activation may be augmented by functional ICP4. We also analyzed two additional markers for NF-kappaB activation, phosphorylation of the p65 subunit on Ser276 and Ser536. Phosphorylation of both serines was induced upon HSV infection and required functional ICP4 and ICP27. Pharmacological inhibitor studies revealed that both IkappaBalpha and Ser276 phosphorylation were dependent on Jun N-terminal protein kinase activity, while Ser536 phosphorylation was not affected during inhibitor treatment. These results demonstrate that there are several layers of regulation of NF-kappaB activation during HSV infection, highlighting the important role that NF-kappaB may play in infection.

Herpes simplex virus infection, with particular reference to the progression and complications of primary herpetic gingivostomatitis

Primary herpetic gingivostomatitis (PHGS) represents the clinically apparent pattern of primary herpes simplex virus (HSV) infection, since the vast majority of other primary infections are symptomless. PHGS is caused predominantly by HSV-1 and affects mainly children. Prodromal symptoms, such as fever, anorexia, irritability, malaise and headache, may occur in advance of disease. The disease presents as numerous pin-head vesicles, which rupture rapidly to form painful irregular ulcerations covered by yellow-grey membranes. Sub-mandibular lymphadenitis, halitosis and refusal to drink are usual concomitant findings. Following resolution of the lesions, the virus travels through the nerve endings to the nerve cells serving the affected area, whereupon it enters a latent state. When the host becomes stressed, the virus replicates and migrates in skin, mucosae and, in rare instances, the central nervous system. A range of morbidities, or even mortality, may then occur, i.e., recurrent HSV infections, which are directly or indirectly associated with PHGS. These pathological entities range from the innocuous herpes labialis to life-threatening meningoencephalitis.

Molecular Pharmacological Phenotyping of EBI2

Epstein-Barr virus (EBV)-induced receptor 2 (EBI2) is an orphan seven-transmembrane (7TM) receptor originally identified as the most up-regulated gene (>200-fold) in EBV-infected cells. Here we show that EBI2 signals with constitutive activity through Galpha(i) as determined by a receptor-mediated inhibition of forskolin-induced cAMP production and an induction of the serum response element-driven transcriptional activity in a pertussis toxin-sensitive manner. Galpha(s) and Galpha(q) were not activated constitutively as determined by the lack of cAMP production, the lack of inositol phosphate turnover, and the lack of activities of the transcription factors: cAMP response element-binding protein and nuclear factor-kappaB. Immunohistochemistry and confocal microscopy of FLAG- and green fluorescent protein-tagged EBI2 revealed cell-surface expression. A putative N-terminal truncated version of EBI2, delta4-EBI2, showed similar expression and signaling through Galpha(i) as full-length EBI2. By using a 32P-labeled EBI2 probe we found a very high expression in lymphoid tissue (spleen and lymph node) and peripheral blood mononuclear cells and a high expression in lung tissue. Real-time PCR of EBV-infected cells showed high expression of EBI2 during latent and lytic infection, in contrast to the EBV-encoded 7TM receptor BILF1, which was induced during lytic infection. EBI2 clustered with the orphan GPR18 by alignment analysis as well as by close proximity in the chromosomal region 13q32.3. Based on the constitutive signaling and cellular expression pattern of EBI2, it is suggested that it may function in conjunction with BILF1 in the reprogramming of the cell during EBV infection.

Induction of cytokine expression by herpes simplex virus in human monocyte-derived macrophages and dendritic cells is dependent on virus replication and is counteracted by ICP27 targeting NF-kappaB and IRF-3

Macrophages and dendritic cells (DCs) play essential roles in host defence against microbial infections. In the present study, it is shown that human monocyte-derived macrophages and DCs express both type I and type III interferons (IFNs) [IFN-alpha, IFN-beta and interleukin 28 (IL-28), IL-29, respectively], tumour necrosis factor alpha and the chemokines CCL5 and CXCL10 after herpes simplex virus 1 (HSV-1) infection. The cytokine-inducing activity of HSV-1 was dependent on viability of the virus, because UV-inactivated virus did not induce a cytokine response. Pretreatment of the cells with IFN-alpha or IL-29 strongly enhanced the HSV-1-induced cytokine response. Both IFN-alpha and IL-29 decreased viral immediate-early (IE) gene infected-cell protein 27 (ICP27) transcription, suggesting that IL-29 possesses antiviral activity against HSV-1 comparable to that of IFN-alpha. Macrophage infection with HSV-1 lacking functional ICP27 (d27-1 virus) resulted in strongly enhanced cytokine mRNA expression and protein production. In contrast, viruses lacking functional IE genes ICP0 and ICP4 induced cytokine responses comparable to those of the wild-type viruses. The activation of transcription factors IRF-3 and NF-kappaB was strongly augmented when macrophages were infected with the ICP27 mutant virus. Altogether, the results demonstrate that HSV-1 both induces and inhibits the antiviral response in human cells and that the type III IFN IL-29, together with IFN-alpha, amplifies the antiviral response against the virus. It is further identified that viral IE-gene expression interferes with the antiviral response in human macrophages and ICP27 is identified as an important viral protein counteracting the early innate immune response.

Abnormal immune response of CCR5-deficient mice to ocular infection with herpes simplex virus type 1

Ocular herpes simplex virus type 1 (HSV-1) infection elicits a strong inflammatory response that is associated with production of the beta chemokines CCL3 and CCL5, which share a common receptor, CCR5. To gain insight into the role of these molecules in ocular immune responses, the corneas of wild-type (WT) and CCR5-deficient (CCR5-/-) mice were infected with HSV-1 and inflammatory parameters were measured. In the absence of CCR5, the early infiltration of neutrophils into the cornea was diminished. Associated with this aberrant leukocyte recruitment, neutrophils in CCR5-/- mice were restricted to the stroma, whereas in WT mice, these cells trafficked to the stroma and epithelial layers of the infected cornea. Virus titres and cytokine/chemokine levels in the infected tissue of these mice were similar for the first 5 days after infection. However, by day 7 post-infection, the CCR5-/- mice showed a significant elevation in the chemokines CCL2, CCL5, CXCL9 and CXCL10 in the trigeminal ganglion and brainstem, as well as a significant increase in virus burden. The increase in chemokine expression was associated with an increase in the infiltration of CD4 and/or CD8 T cells into the trigeminal ganglion and brainstem of CCR5-/- mice. Surprisingly, even though infected CCR5-/- mice were less efficient at controlling the progression of virus replication, there was no difference in mortality. These results suggest that, although CCR5 plays a role in regulating leukocyte trafficking and control of virus burden, compensatory mechanisms are involved in preventing mortality following HSV-1 infection.

A functional annotation of subproteomes in human plasma

The data collected by Human Proteome Organization's Plasma Proteome Pilot project phase was analyzed by members of our working group. Accordingly, a functional annotation of the human plasma proteome was carried out. Here, we report the findings of our analyses. First, bioinformatic analyses were undertaken to determine the likely sources of plasma proteins and to develop a protein interaction network of proteins identified in this project. Second, annotation of these proteins was performed in the context of functional subproteomes involved in the coagulation pathway, the mononuclear phagocytic system, the inflammation pathway, the cardiovascular system, and the liver; as well as the subset of proteins associated with DNA binding activities. Our analyses contributed to the Plasma Proteome Database (http://www.plasmaproteomedatabase.org), an annotated database of plasma proteins identified by HPPP as well as from other published studies. In addition, we address several methodological considerations including the selective enrichment of post-translationally modified proteins by the use of multi-lectin chromatography as well as the use of peptidomic techniques to characterize the low molecular weight proteins in plasma. Furthermore, we have performed additional analyses of peptide identification data to annotate cleavage of signal peptides, sites of intra-membrane proteolysis and post-translational modifications. The HPPP-organized, multi-laboratory effort, as described herein, resulted in much synergy and was essential to the success of this project.

Chemokine Signaling Pathways in Corneal Fibroblasts

Chemokines act as leukocyte chemoattractants with fine specificity for individual leukocyte types. Chemokine activation in infectious and inflammatory conditions of the cornea has been well described and is thought to result from rapid activation of intracellular signaling cascades within corneal cells. Keratocytes, the resident cells of the corneal stroma, capably express a diverse array of chemokine family members. We describe the role of chemokines in corneal inflammation in both human disease and experimental animal models. Understanding the precise molecular signaling mechanisms for regulation of chemokine expression will be integral to the design of strategies for the reduction of detrimental corneal inflammation.

Reduced immune responses after vaccination with a recombinant herpes simplex virus type 1 vector in the presence of antiviral immunity

Due to the continuous need for new vaccines, viral vaccine vectors have become increasingly attractive. In particular, herpes simplex virus type 1 (HSV-1)-based vectors offer many advantages, such as broad cellular tropism, large DNA-packaging capacity and the induction of pro-inflammatory responses. However, despite promising results obtained with HSV-1-derived vectors, the question of whether pre-existing virus-specific host immunity affects vaccine efficacy remains controversial. For this reason, the influence of pre-existing HSV-1-specific immunity on the immune response induced with a replication-defective, recombinant HSV-1 vaccine was investigated in vivo. It was shown that humoral as well as cellular immune responses against a model antigen encoded by the vaccine were strongly diminished in HSV-1-seropositive mice. This inhibition could be observed in mice infected with wild-type HSV-1 or with a replication-defective vector. Although these data clearly indicate that pre-existing antiviral host immunity impairs the efficacy of HSV-1-derived vaccine vectors, they also show that vaccination under these constraints might still be feasible.

Interferon Regulatory Factor 1 Is an Essential and Direct Transcriptional Activator for Interferon γ-induced RANTES/CCl5 Expression in Macrophages

Interferon regulatory factor 1 (IRF-1) is an important transcription factor in interferon gamma (IFNgamma)-mediated signaling in the development and function of NK cells and cytotoxic T lymphocytes. RANTES (regulated on activation normal T cell expressed and secreted; CCL5) is a member of the CC chemokine family of proteins, which is strongly chemoattractant for several important immune cell types in host defense against infectious agents and cancer. However, the role of IFNgamma and IRF-1 in the regulation of RANTES gene expression and their operative mechanisms in macrophages have not been established. We report here that RANTES expression in IRF-1-null mice, primarily in macrophages, in response to carcinogenic stimulation in vivo and in vitro and to IFNgamma but not to lipopolysaccharide in vitro, was markedly decreased. As a result, RANTES-mediated chemoattraction of CCR5(+) target cells was also severely impaired. Adenovirus-mediated gene transduction of IRF-1 in primary macrophages resulted in enhanced RANTES expression. The IFNgamma and IRF1 response element was localized to a TTTTC motif at -147 to -143 of the mouse RANTES promoter, to which endogenous or recombinant IRF-1 can physically bind in vitro and in vivo. This study uncovers a novel IFNgamma-induced pathway in RANTES expression mediated by IRF-1 in macrophages and elucidates an important host defense mechanism against neoplastic transformation.

Viral activation of macrophages through TLR-dependent and -independent pathways

Induction of cytokine production is important for activation of an efficient host defense response. Macrophages constitute an important source of cytokines. In this study we have investigated the virus-cell interactions triggering induction of cytokine expression in macrophages during viral infections. We found that viral entry and viral gene products produced inside the cell are responsible for activation of induction pathways leading to IFN-alphabeta expression, indicating that virus-cell interactions on the cell surface are not enough. Moreover, by the use of cell lines expressing dominant negative versions of TLR-associated adaptor proteins we demonstrate that Toll/IL-1 receptor domain-containing adaptor inducing IFN-beta is dispensable for all virus-induced cytokine expression examined. However, a cell line expressing dominant negative MyD88 revealed the existence of distinct induction pathways because virus-induced expression of RANTES and TNF-alpha was totally blocked in this cell line whereas IFN-alphabeta expression was much less affected in the absence of signaling via MyD88. In support of this, we also found that inhibitory CpG motifs, which block TLR9 signaling inhibited early HSV-2-induced TNF-alpha and RANTES expression dramatically whereas IFN-alphabeta induction was only slightly affected. This suggests that virus activates macrophages through distinct pathways, of which some are dependent on TLRs signaling through MyD88, whereas others seem to be independent of TLR signaling. Finally we demonstrate that IFN-alphabeta induction in HSV-2-infected macrophages requires a functional dsRNA-activated protein kinase molecule because cells expressing a dsRNA-dependent protein kinase version unable to bind dsRNA do not express IFN-alphabeta on infection.

Persistent expression of chemokine and chemokine receptor RNAs at primary and latent sites of herpes simplex virus 1 infection

Inflammatory cytokines and infiltrating T cells are readily detected in herpes simplex virus (HSV) infected mouse cornea and trigeminal ganglia (TG) during the acute phase of infection, and certain cytokines continue to be expressed at lower levels in infected TG during the subsequent latent phase. Recent results have shown that HSV infection activates Toll-like receptor signaling. Thus, we hypothesized that chemokines may be broadly expressed at both primary sites and latent sites of HSV infection for prolonged periods of time. Real-time reverse transcriptase-polymrease chain reaction (RT-PCR) to quantify expression levels of transcripts encoding chemokines and their receptors in cornea and TG following corneal infection. RNAs encoding the inflammatory-type chemokine receptors CCR1, CCR2, CCR5, and CXCR3, which are highly expressed on activated T cells, macrophages and most immature dendritic cells (DC), and the more broadly expressed CCR7, were highly expressed and strongly induced in infected cornea and TG at 3 and 10 days postinfection (dpi). Elevated levels of these RNAs persisted in both cornea and TG during the latent phase at 30 dpi. RNAs for the broadly expressed CXCR4 receptor was induced at 30 dpi but less so at 3 and 10 dpi in both cornea and TG. Transcripts for CCR3 and CCR6, receptors that are not highly expressed on activated T cells or macrophages, also appeared to be induced during acute and latent phases; however, their very low expression levels were near the limit of our detection. RNAs encoding the CCR1 and CCR5 chemokine ligands MIP-1α, MIP-1β and RANTES, and the CCR2 ligand MCP-1 were also strongly induced and persisted in cornea and TG during the latent phase. These and other recent results argue that HSV antigens or DNA can stimulate expression of chemokines, perhaps through activation of Toll-like receptors, for long periods of time at both primary and latent sites of HSV infection. These chemokines recruit activated T cells and other immune cells, including DC, that express chemokine receptors to primary and secondary sites of infection. Prolonged activation of chemokine expression could provide mechanistic explanations for certain aspects of HSV biology and pathogenesis.

Alterations in chemokine expression following Theiler's virus infection and restraint stress

Restraint stress (RS) applied to mice during acute infection with Theiler's virus causes corticosterone-induced immunosuppression. This effect was further investigated by measuring chemokine changes in the spleen and central nervous system (CNS) using an RNase Protection Assay. mRNAs for lymphotactin (Ltn), interferon-induced protein-10 (IP-10), MIP-1 beta, monocyte chemoattractant protein-1 (MCP-1) and TCA-3 were detected in the spleen at day 2 pi, but not in the brain of CBA mice infected with Theiler's virus. Ltn, IP-10 and RANTES were elevated in both the spleen and the brain at day 7 pi, and were significantly decreased by RS in the brain. RS also resulted in decreased inflammation within the CNS.

Suppression of proinflammatory cytokine expression by herpes simplex virus type 1

Viral immune evasion strategies are important for establishment and maintenance of infections. Many viruses are in possession of mechanisms to counteract the antiviral response raised by the infected host. Here we show that a herpes simplex virus type 1 (HSV-1) mutant lacking functional viral protein 16 (VP16)-a tegument protein promoting viral gene expression-induced significantly higher levels of proinflammatory cytokines than wild-type HSV-1. This was observed in several cell lines and primary murine macrophages, as well as in peritoneal cells harvested from mice infected in vivo. The enhanced ability to stimulate cytokine expression in the absence of VP16 was not mediated directly by VP16 but was dependent on the viral immediate-early genes for infected cell protein 4 (ICP4) and ICP27, which are expressed in a VP16-dependent manner during primary HSV infection. The virus appeared to target cellular factors other than interferon-induced double-stranded RNA-activated protein kinase R (PKR), since the virus mutants remained stronger inducers of cytokines in cells stably expressing a dominant-negative mutant form of PKR. Finally, mRNA stability assay revealed a significantly longer half-life for interleukin-6 mRNA after infection with the VP16 mutant than after infection with the wild-type virus. Thus, HSV is able to suppress expression of proinflammatory cytokines by decreasing the stability of mRNAs, thereby potentially impeding the antiviral host response to infection.

Blocking CC chemokine receptor (CCR) 1 and CCR5 during herpes simplex virus type 2 infection in vivo impairs host defence and perturbs the cytokine response

Elimination of viral infections is dependent on rapid recruitment of leucocytes to infected areas. Chemokines constitute a class of cytokines that regulate migration of leucocytes to sites of infection. In this work, the expression and function of CC chemokine receptor (CCR)1 and CCR5 and their ligands during a generalized herpes simplex virus type 2 (HSV-2) infection in mice were studied. Many CCR1 and CCR5 ligands were expressed in infected organs after intraperitoneal infection. In particular, CC chemokine expression in the liver preceded the expression of CCR1 and CCR5, suggesting recruitment of cells bearing these receptors, which correlated with a decrease in viral titres. Administration of Met-RANTES, a CCR1 and CCR5 antagonist, led to impaired antiviral response with significantly higher viral titre in the liver on days 1 and 6 after infection. This observation was accompanied by a decreased and shortened recruitment of natural killer cells to the peritoneum of infected mice treated with the antagonist. Despite this reduced recruitment of antiviral leucocytes in mice receiving Met-RANTES, peritoneal cells from these mice produced markedly enhanced levels of pro-inflammatory cytokines. Altogether, the results suggest that CCR1 and/or CCR5 are important for both viral clearance and eventual control of the immune response.

Latent herpesvirus infection in human trigeminal ganglia causes chronic immune response

The majority of trigeminal ganglia (TGs) are latently infected with alpha-herpesviruses [herpes simplex virus type-1 (HSV-1) and varicella-zoster virus (VZV)]. Whereas HSV-1 periodically reactivates in the TGs, VZV reactivates very rarely. The goal of this study was to determine whether herpesvirus latency is linked to a local immune cell infiltration in human TGs. T cells positive for the CD3 and CD8 markers, and CD68-positive macrophages were found in 30 of 42 examined TGs from 21 healthy individuals. The presence of immune cells correlated constantly with the occurrence of the HSV-1 latency-associated transcript (LAT) and only irregularly with the presence of latent VZV protein. In contrast, uninfected TGs showed no immune cell infiltration. Quantitative RT-PCR revealed that CD8, interferon-gamma, tumor necrosis factor-alpha, IP-10, and RANTES transcripts were significantly induced in TGs latently infected with HSV-1 but not in uninfected TGs. The persisting lymphocytic cell infiltration and the elevated CD8 and cytokine/chemokine expression in the TGs demonstrate for the first time that latent herpesviral infection in humans is accompanied by a chronic inflammatory process at an immunoprivileged site but without any neuronal destruction. The chronic immune response seems to maintain viral latency and influence viral reactivation.

Induction of signaling pathways by herpes simplex virus type 1 through glycoprotein H peptides

Eukaryotic cells respond to extracellular stimuli, such as viruses, by recruiting signal transduction pathways, many of which are mediated through activation of distinct mitogen-activated protein kinase (MAPK) cascades and activation of transductional regulation factors. The best characterized of this pathway are the extracellular signal regulated kinase (ERK), the c-Jun N-terminal kinase/stress activated protein kinase (JNK/SAPK), and the p38 MAPK cascade. Herpes simplex virus type 1 (HSV-1) encodes at least 11 envelope glycoproteins, which alone or in concert play different roles in viral adsorption, entry, cell-to-cell spread, and immune evasion. Of these proteins, three are designated glycoprotein B (gB), glycoprotein D (gD), and the gH/gL heterodimer, are clearly involved in attachment and entry, and therefore possible candidates in inducing early cellular activation.Nevertheless, the precise role of each glycoprotein and the cellular factor involved remain elusive. The signal transduction pathways involved, and the outcome of cellular activation on viral entry or postentry events, are still to be elucidated. To better understand the role of signal transduction pathways and phosphorylation events in HSV-1 entry, synthetic peptides modeled on HSV-1 gH were synthesized and tested for MEK1-MEK2/MAPK cascade activation. Our results show a major involvement of the JNK pathway in the intracellular signal transmission after stimulation with gH HSV-1 peptides.

Caspase-dependent apoptosis in fulminant hepatic failure induced by herpes simplex virus in mice

BACKGROUND/AIMS

Herpes simplex virus (HSV) is known to induce fulminant hepatic failure. The aim of this study is to clarify the molecular basis of liver injury in HSV-induced hepatitis.

METHODS

Immunocompetent mice were inoculated with HSV or ultraviolet-inactivated HSV (UV-HSV) intravenously. Extent of liver injury was evaluated by changes of serum enzymes and histopathology. Apoptosis was assessed by DNA fragmentation and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). Immunohistochemistry for caspase-3 and Fas ligand was performed. Reverse transcriptase-polymerase chain reaction for Fas ligand was also performed.

RESULTS

All mice died of rapid and massive liver cell death after HSV infection, whereas no change was observed in mice after UV-HSV inoculation. The extent of viral replication and DNA fragmentation correlated well with the severity of liver injury. Caspase-3 was activated in the liver after HSV infection, but not UV-HSV. Positive reaction for TUNEL was observed not only in HSV-antigen positive cells but also in HSV-antigen negative cells. Fas ligand was induced in the liver infected with HSV, but not with UV-HSV.

CONCLUSIONS

Caspase-dependent apoptosis is involved in HSV-associated liver injury. Not only viral replication but also non-viral factor such as Fas ligand may facilitate rapid development of this disease.

Herpes simplex virus triggers activation of calcium-signaling pathways

The cellular pathways required for herpes simplex virus (HSV) invasion have not been defined. To test the hypothesis that HSV entry triggers activation of Ca2+-signaling pathways, the effects on intracellular calcium concentration ([Ca2+]i) after exposure of cells to HSV were examined. Exposure to virus results in a rapid and transient increase in [Ca2+]i. Pretreatment of cells with pharmacological agents that block release of inositol 1,4,5-triphosphate (IP3)-sensitive endoplasmic reticulum stores abrogates the response. Moreover, treatment of cells with these pharmacological agents inhibits HSV infection and prevents focal adhesion kinase (FAK) phosphorylation, which occurs within 5 min after viral infection. Viruses deleted in glycoprotein L or glycoprotein D, which bind but do not penetrate, fail to induce a [Ca2+]i response or trigger FAK phosphorylation. Together, these results support a model for HSV infection that requires activation of IP3-responsive Ca2+-signaling pathways and that is associated with FAK phosphorylation. Defining the pathway of viral invasion may lead to new targets for anti-viral therapy.

Induction of RANTES/CCL5 by herpes simplex virus is regulated by nuclear factor kappa B and interferon regulatory factor 3

Chemokines regulate migration of leukocytes to sites of infection. In this work, we have shown that the chemokine RANTES/CCL5 is produced after herpes simplex virus (HSV) infection of macrophages and fibroblasts and provide data on the underlying molecular mechanism. Reporter gene assays showed HSV-induced RANTES production to be regulated at the transcriptional level. Expression of RANTES was blocked by N-tosyl-L-phenylalanine, an inhibitor of the nuclear factor kappa B (NF-kappa B) pathway and also in cell lines stably expressing a dominant-negative mutant of I kappa B kinase beta. Cell lines stably expressing a dominant-negative mutant of interferon regulatory factor 3 (IRF-3) also produced dramatically decreased levels of RANTES after infection compared with the control cell line. In contrast, overexpression of dominant-negative p38 and also treatment with SB203580, an inhibitor of p38, did not significantly affect expression of RANTES. Taken together, these data suggest that HSV induces transcriptional activation of the RANTES gene through the transcription factors NF-kappa B and IRF-3.

Expression and function of chemokines during viral infections: from molecular mechanisms to in vivo function

Recruitment and activation of leukocytes are important for elimination of microbes, including viruses, from infected areas. Chemokines constitute a group of bioactive peptides that regulate leukocyte migration and also contribute to activation of these cells. Chemokines are essential mediators of inflammation and important for control of viral infections. The profile of chemokine expression contributes to shaping the immune response during viral infection, whereas viral subversion of the chemokine system allows the virus to evade antiviral activities of the host. In this review, we discuss the role of chemokines in host-defense against virus infections, and we also look deeper into the virus-cell interactions that trigger chemokine expression as well as the cellular signaling cascades involved.

Activation of NF-kappa B in virus-infected macrophages is dependent on mitochondrial oxidative stress and intracellular calcium: downstream involvement of the kinases TGF-beta-activated kinase 1, mitogen-activated kinase/extracellular signal-regulated kinase kinase 1, and I kappa B kinase

Efficient clearance of virus infections depends on the nature of the host response raised by the infected organism. A proinflammatory cell-mediated immune response is important for elimination of many viruses, including herpesviruses. Macrophages are intimately involved in generation of a proinflammatory response, the initiation of which involves activation of the transcription factor NF-kappaB. However, the mechanisms of HSV-induced NF-kappaB activation are poorly understood. In this study we demonstrate that activation of NF-kappaB by HSV in macrophages is dependent on a functional viral genome and proceeds through a mechanism involving the cellular IkappaB kinase, as well as the upstream kinases TGF-beta-activated kinase 1, mitogen-activated kinase/extracellular signal-regulated kinase kinase 1, and possibly NF-kappaB-inducing kinase. Furthermore, we show that HSV triggers NF-kappaB activation by a signaling pathway involving oxidative stress in mitochondria and intracellular calcium, because specific inhibition of mitochondria-derived reactive oxygen intermediates, as well as mitochondrial calcium channels, prevented NF-kappaB activation. Together, these results point to mitochondria as cellular checkpoints able to initiate NF-kappaB activation after virus infection and also show that the cellular NF-kappaB-regulating kinases IkappaB kinase, TGF-beta-activated kinase 1, mitogen-activated kinase/extracellular signal-regulated kinase kinase 1, and possibly NF-kappaB-inducing kinase, are essential components in the HSV-induced signaling pathway.

Effects of innate immunity on herpes simplex virus and its ability to kill tumor cells

Several clinical trials have or are being performed testing the safety and efficacy of different strains of oncolytic viruses (OV) for malignant cancers. OVs represent either naturally occurring or genetically engineered strains of viruses that exhibit relatively selective replication in tumor cells. Several types of OV have been derived from herpes simplex virus 1 (HSV1). Tumor oncolysis depends on the processes of initial OV infection of tumor, followed by subsequent propagation of OV within the tumor itself. The role of the immune responses in these processes has not been extensively studied. On the contrary, effects of the immune response on the processes of wild-type HSV1 infection and propagation in the central nervous system have been studied and described in detail. The first line of defense against a wild-type HSV1 infection in both naive and immunized individuals is provided by innate humoral (complement, cytokines, chemokines) and cellular (macrophages, neutrophils, NK cells, gammadelta T cells, and interferon-producing cells) responses. These orchestrate the lysis of virions and virus-infected cells as well as provide a link to effective adaptive immunity. The role of innate defenses in curtailing the oncolytic effect of genetically engineered HSV has only recently been studied, but several of the same host responses appear to be operative in limiting anticancer effects by the replicating virus. The importance of this knowledge lies in finding avenues to modulate such initial innate responses, in order to allow for increased oncolysis of tumors while minimizing host toxicity.