Independent and cooperative antiviral actions of beta interferon and gamma interferon against herpes simplex virus replication in primary human fibroblasts

Transcriptional synergy in human aortic endothelial cells is vulnerable to combination p300/CBP and BET bromodomain inhibition

Combinatorial signaling by proinflammatory cytokines synergizes to exacerbate toxicity to cells and tissue injury during acute infections. To explore synergism at the gene-regulatory level, we investigated the dynamics of transcription and chromatin signaling in response to dual cytokines by integrating nascent RNA imaging mass spectrometry, RNA sequencing, amplification-independent mRNA quantification, assay for transposase-accessible chromatin using sequencing (ATAC-seq), and transcription factor profiling. Costimulation with interferon-gamma (IFNγ) and tumor necrosis factor alpha (TNFα) synergistically induced a small subset of genes, including the chemokines CXCL9, -10, and -11. Gene induction coincided with increased chromatin accessibility at non-coding regions enriched for p65 and STAT1 binding sites. To discover coactivator dependencies, we conducted a targeted chemogenomic screen of transcriptional inhibitors followed by modeling of inhibitor dose-response curves. These results identified high efficacy of either p300/CREB-binding protein (CBP) or bromodomain and extra-terminal (BET) bromodomain inhibitors to disrupt induction of synergy genes. Combination p300/CBP and BET bromodomain inhibition at half-maximal inhibitory concentrations (subIC50) synergistically abrogated IFNγ/TNFα-induced chemokine gene and protein levels.

Immunomodulatory Role of Interferons in Viral and Bacterial Infections

Interferons are a group of immunomodulatory substances produced by the human immune system in response to the presence of pathogens, especially during viral and bacterial infections. Their remarkably diverse mechanisms of action help the immune system fight infections by activating hundreds of genes involved in signal transduction pathways. In this review, we focus on discussing the interplay between the IFN system and seven medically important and challenging viruses (herpes simplex virus (HSV), influenza, hepatitis C virus (HCV), lymphocytic choriomeningitis virus (LCMV), human immunodeficiency virus (HIV), Epstein-Barr virus (EBV), and SARS-CoV coronavirus) to highlight the diversity of viral strategies. In addition, the available data also suggest that IFNs play an important role in the course of bacterial infections. Research is currently underway to identify and elucidate the exact role of specific genes and effector pathways in generating the antimicrobial response mediated by IFNs. Despite the numerous studies on the role of interferons in antimicrobial responses, many interdisciplinary studies are still needed to understand and optimize their use in personalized therapeutics.

IRF3 inhibits IFN-γ-mediated restriction of intracellular pathogens in macrophages independently of IFNAR

Macrophages use an array of innate immune sensors to detect intracellular pathogens and to tailor effective antimicrobial responses. In addition, extrinsic activation with the cytokine IFN-γ is often required as well to tip the scales of the host-pathogen balance toward pathogen restriction. However, little is known about how host-pathogen sensing impacts the antimicrobial IFN-γ-activated state. It was observed that in the absence of IRF3, a key downstream component of pathogen sensing pathways, IFN-γ-primed macrophages more efficiently restricted the intracellular bacterium Legionella pneumophila and the intracellular protozoan parasite Trypanosoma cruzi. This effect did not require IFNAR, the receptor for Type I IFNs known to be induced by IRF3, nor the sensing adaptors MyD88/TRIF, MAVS, or STING. This effect also did not involve differential activation of STAT1, the major signaling protein downstream of both Type 1 and Type 2 IFN receptors. IRF3-deficient macrophages displayed a significantly altered IFN-γ-induced gene expression program, with up-regulation of microbial restriction factors such as Nos2. Finally, we found that IFN-γ-primed but not unprimed macrophages largely excluded the activated form of IRF3 from the nucleus following bacterial infection. These data are consistent with a relationship of mutual inhibition between IRF3 and IFN-γ-activated programs, possibly as a component of a partially reversible mechanism for modulating the activity of potent innate immune effectors (such as Nos2) in the context of intracellular infection.

Saga of monokines in shaping tumour-immune microenvironment: Origin to execution

Cellular communication mediated by cytokines is an important mechanism dictating immune responses, their cross talk and final immune output. Cytokines play a major role in dictating the immune outcome to cancer by regulating the events of development, differentiation and activation of innate immune cells. Cytokines are pleiotropic in nature, hence understanding their role individually or as member of network cytokines is critical to delineate their role in tumour immunity. Tumour systemically manipulates the immune system to evade and escape immune recognition for their uncontrollable growth and metastasis. The developing tumour comprise a large and diverse set of myeloid cells which are vulnerable to manipulation by the tumour-microenvironment. The innate immune cells of the monocytic lineage skew the fate of the adaptive immune cells and thus dictating cancer elimination or progression. Targeting cells at tumour cite is preposterous owing to their tight network, poor reach and abundance of immunosuppressive mechanisms. Monocytic lineage-derived cytokines (monokines) play crucial role in tumour regression or progression by either directly killing the tumour cells with TNFα or promoting its growth by TGFβ. In addition, the monokines like IL-12, IL-1β, IL-6, IL-10 and TGFβ direct the adaptive immune cells to secrete anti-tumour cytokines, TNFα, IFNγ, perforin and granzyme or pro-tumour cytokines, IL-10 and TGFβ. In this review, we elucidate the roles of monokines in dictating the fate of tumour by regulating responses at various stages of generation, differentiation and activation of immune cells along with the extensive cross talk. We have attempted to delineate the synergy and antagonism of major monokines among themselves or with tumour-derived or adaptive immune cytokines. The review provides an update on the possibilities of placing monokines to potential practical use as cytokine therapy against cancer.

Distinct populations of antigen-specific tissue-resident CD8+ T cells in human cervix mucosa

The ectocervix is part of the lower female reproductive tract (FRT), which is susceptible to sexually transmitted infections (STIs). Comprehensive knowledge of the phenotypes and T cell receptor (TCR) repertoire of tissue-resident memory T cells (TRMs) in the human FRT is lacking. We took single-cell RNA-Seq approaches to simultaneously define gene expression and TCR clonotypes of the human ectocervix. There were significantly more CD8+ than CD4+ T cells. Unsupervised clustering and trajectory analysis identified distinct populations of CD8+ T cells with IFNGhiGZMBloCD69hiCD103lo or IFNGloGZMBhiCD69medCD103hi phenotypes. Little overlap was seen between their TCR repertoires. Immunofluorescence staining showed that CD103+CD8+ TRMs were preferentially localized in the epithelium, whereas CD69+CD8+ TRMs were distributed evenly in the epithelium and stroma. Ex vivo assays indicated that up to 14% of cervical CD8+ TRM clonotypes were HSV-2 reactive in HSV-2-seropositive persons, reflecting physiologically relevant localization. Our studies identified subgroups of CD8+ TRMs in the human ectocervix that exhibited distinct expression of antiviral defense and tissue residency markers, anatomic locations, and TCR repertoires that target anatomically relevant viral antigens. Optimization of the location, number, and function of FRT TRMs is an important approach for improving host defenses to STIs.

Independent and Correlated Role of Apolipoprotein E ɛ4 Genotype and Herpes Simplex Virus Type 1 in Alzheimer's Disease

The ɛ4 allele of the Apolipoprotein E (APOE) gene in individuals infected by Herpes simplex virus type 1 (HSV-1) has been demonstrated to be a risk factor in Alzheimer's disease (AD). APOE-ɛ4 reduces the levels of neuronal cholesterol, interferes with the transportation of cholesterol, impairs repair of synapses, decreases the clearance of neurotoxic peptide amyloid-β (Aβ), and promotes the deposition of amyloid plaque, and eventually may cause development of AD. HSV-1 enters host cells and can infect the olfactory system, trigeminal ganglia, entorhinal cortex, and hippocampus, and may cause AD-like pathological changes. The lifecycle of HSV-1 goes through a long latent phase. HSV-1 induces neurotropic cytokine expression with pro-inflammatory action and inhibits antiviral cytokine production in AD. It should be noted that interferons display antiviral activity in HSV-1-infected AD patients. Reactivated HSV-1 is associated with infectious burden in cognitive decline and AD. Finally, HSV-1 DNA has been confirmed as present in human brains and is associated with APOEɛ4 in AD. HSV-1 and APOEɛ4 increase the risk of AD and relate to abnormal autophagy, higher concentrations of HSV-1 DNA in AD, and formation of Aβ plaques and neurofibrillary tangles.

A dissection of SARS‑CoV2 with clinical implications (Review)

We are being confronted with the most consequential pandemic since the Spanish flu of 1918‑1920 to the extent that never before have 4 billion people quarantined simultaneously; to address this global challenge we bring to the forefront the options for medical treatment and summarize SARS‑CoV2 structure and functions, immune responses and known treatments. Based on literature and our own experience we propose new interventions, including the use of amiodarone, simvastatin, pioglitazone and curcumin. In mild infections (sore throat, cough) we advocate prompt local treatment for the naso‑pharynx (inhalations; aerosols; nebulizers); for moderate to severe infections we propose a tried‑and‑true treatment: the combination of arginine and ascorbate, administered orally or intravenously. The material is organized in three sections: i) Clinical aspects of COVID‑19; acute respiratory distress syndrome (ARDS); known treatments; ii) Structure and functions of SARS‑CoV2 and proposed antiviral drugs; iii) The combination of arginine‑ascorbate.

Tissue-resident T cell-derived cytokines eliminate herpes simplex virus-2-infected cells

The mechanisms underlying rapid elimination of herpes simplex virus-2 (HSV-2) in the human genital tract despite low CD8+ and CD4+ tissue-resident T cell (Trm cell) density are unknown. We analyzed shedding episodes during chronic HSV-2 infection; viral clearance always predominated within 24 hours of detection even when viral load exceeded 1 × 107 HSV DNA copies, and surges in granzyme B and IFN-γ occurred within the early hours after reactivation and correlated with local viral load. We next developed an agent-based mathematical model of an HSV-2 genital ulcer to integrate mechanistic observations of Trm cells in in situ proliferation, trafficking, cytolytic effects, and cytokine alarm signaling from murine studies with viral kinetics, histopathology, and lesion size data from humans. A sufficiently high density of HSV-2-specific Trm cells predicted rapid elimination of infected cells, but our data suggest that such Trm cell densities are relatively uncommon in infected tissues. At lower, more commonly observed Trm cell densities, Trm cells must initiate a rapidly diffusing, polyfunctional cytokine response with activation of bystander T cells in order to eliminate a majority of infected cells and eradicate briskly spreading HSV-2 infection.

Effect of exogenous expression of IFN-γ on the new world alphavirus replication and infection

Aim: IFN-γ plays an important role in control of the old world alphavirus infection. However, the role of IFN-γ in the infection by the new world alphaviruses is not well characterized. Materials & methods: Ad5-mIFN-γ, a recombinant, replication-deficient human adenovirus, was constructed to express mouse IFN-γ (mIFN-γ) and a mouse, lethal challenge model of the new world alphavirus western equine encephalitis virus (WEEV) was used. Results: A single-dose injection of Ad5-mIFN-γ produced a high level of mIFN-γ in mice. Cells inoculated with Ad5-mIFN-γ restricted the replication of WEEV. A single-dose injection of Ad5-mIFN-γ delayed the WEEV infection and extended the survival time in mice. Conclusion: IFN-γ restricts the WEEV infection.

Radiotherapy-induced reactivation of neurotrophic human herpes viruses: Overview and management

PURPOSE

Infection by Human Herpes Viruses (HHV) types 1-3, are prevalent throughout the world. It is known that radiotherapy can reactivate HHVs, but it is unclear how and to what extent reactivations can interact with or affect radiotherapeutic efficacy, patient outcomes and mortality risk. Herein, we aim to summarize what is known about Herpes Simplex Virus (HSV)-1,2 and Varicella Zoster Virus (VZV) pathophysiology as it relates to tumor biology, radiotherapy, chemo-radiotherapy, diagnosis and management so as to optimize cancer treatment in the setting of active HHV infection. Our secondary aim is to emphasize the need for further research to elucidate the potential adverse effects of active HHV infection in irradiated tumor tissue and to design optimal management strategies to incorporate into cancer management guidelines.

MATERIALS AND METHODS

The literature regarding herpetic infection, herpetic reactivation, and recurrence occurring during radiotherapy and that regarding treatment guidelines for herpetic infections are reviewed. We aim to provide the oncologist with a reference for the infectious dangers of herpetic reactivation in patients under their care and well established methods for prevention, diagnosis, and treatment of such infections. Pain management is also considered.

CONCLUSIONS

In the radiotherapeutic setting, serologic assays for HSV-1 and HSV-2 are feasible and can alert the clinician to patients at risk for viral reactivation. RT-PCR is specific in identifying the exact viral culprit and is the preferred diagnostic method to measure interventional efficacy. It can also differentiate between herpetic infection and radionecrosis. The MicroTrak^® HSV1/HSV2/VZV staining kit has high sensitivity and specificity in acute lesions, is also the most rapid means to confirm diagnosis. Herpetic reactivation and recurrences during radiotherapy can cause interruptions, cessations, or prolongations of the radiotherapeutic course, thus decreasing the biologically effective dose, to sub-therapeutic levels. Active HHV infection within the treatment volume results in increased tumor radio-resistance and potentially sub-therapeutic care if left untreated. Visceral reactivations may result in fatality and therefore, a high index of suspicion is important to identify these active infections. The fact that such infections may be mistaken for acute and/or late radiation effects, leading to less than optimal treatment decisions, makes knowledge of this problem even more relevant. To minimize the risk of these sequelae, prompt anti-viral therapy is recommended, lasting the course of radiotherapy.

Constitutive IFNα/β signaling maintains expression of signaling intermediaries for efficient cytokine responses

Interferons (IFNs) are a family of immunoregulatory cytokines with important roles in anti-viral and anti-tumor responses. Type I and II IFNs bind distinct receptors and are associated with different stages of the immune response. There is however, considerable crosstalk between these two cytokines with enhancement of IFNγ responses following IFNα/β priming and loss of IFNα/β receptor (IFNAR) resulting in diminished IFNγ responses. In this study, we sought to define the mechanism of crosstalk between the type I and II IFNs. Our previous reports demonstrated reduced expression of the canonically activated transcription factor signal transducer and activator of transcription (STAT)1, in cells lacking the IFNAR α chain (IFNAR1). Therefore, we used microarray analysis to determine whether reconstitution of STAT1 in IFNAR1-deficient cells was sufficient to restore IFNγ responses. We identified several biological pathways, including the MHC class I antigen presentation pathway, in which STAT1 reconstitution was able to significantly rescue IFNγ-mediated gene regulation in Ifnar1 (-/-) cells. Notably, we also found that in addition to low basal expression of STAT1, cells lacking the IFNAR1 also had aberrant expression of multiple other transcription factors and signaling intermediaries. The studies described herein demonstrate that basal and regulated expression of signaling intermediaries is a mechanism for crosstalk between cytokines including type I and II IFNs.

The neuropathogenic T953 strain of equine herpesvirus-1 inhibits type-I IFN mediated antiviral activity in equine endothelial cells

Equine herpesvirus-1 (EHV-1) infects equine endothelial cells (EECs) lining the small blood vessels in the central nervous system. However, the effect of type I IFN on EHV-1 replication in the EECs is not well studied. Thus, the primary objective of this study was to investigate the effect of type-I IFN on the replication of the neuropathogenic T953 strain of EHV-1 in vitro in EECs. The initial data showed that the EHV-1 was partly resistant to the biological effect of exogenously supplied recombinant equine IFN-α. Subsequent investigation into the mechanism of resistance showed that EHV-1 infection of EECs interfered with the STAT-1 phosphorylation through which type-I IFN exerts its antiviral effect. Immunofluorescence staining showed interference with the translocation of STAT-1 molecules from cytoplasm to nucleus confirming the virus mediated suppression of STAT-1 activation. Downstream of the JAK-STAT signaling, EHV-1 infection inhibited expression of cellular antiviral proteins including IFN-stimulated gene 56 (ISG56) and viperin. Taken together these findings suggest that the neuropathogenic T953 strain of EHV-1 evades the host innate immune response by inhibiting IFN and this may provide some insight into the pathogenesis of EHV-1 infection.

Kinetic Differences and Synergistic Antiviral Effects Between Type I and Type III Interferon Signaling Indicate Pathway Independence

The spread of acute respiratory viral infections is controlled by type I and III interferon (IFN) signaling. While the mechanisms of type I IFN signaling have been studied in detail, features that distinguish type III IFN signaling remain poorly understood. Type III IFNs play an essential role in limiting infections of intestinal and respiratory epithelial surfaces; however, type III IFNs have been shown to activate similar genes to type I IFNs, raising the question of how these IFNs differ and their signals interact. We measured the kinetics of type I and III IFN activation, functional stability, and downstream antiviral responses on A549 human lung epithelial cells. Similar kinetics were found for transcriptional upregulation and secretion of type I and III IFNs in response to infection by an RNA virus, peaking at 12 h postinfection, and both protein types had similar stabilities with functional half-lives extending beyond 2 days. Both IFNs activated potent cellular antiviral responses; however, responses to type III IFNs were delayed by 2-6 h relative to type I IFN responses. Combined treatments with type I and III IFNs produced enhanced antiviral effects, and quantitative analysis of these data with a Bliss interaction model provides evidence for independence of type I and III IFN downstream signaling pathways. This novel synergistic interaction has therapeutic implications for treatment of respiratory virus infections.

Type I IFN family members: similarity, differences and interaction

Interferons (IFN) are key cytokines with multifaceted antiviral and cell-modulatory properties. Three distinct types of IFN are recognized (I-III) based on structural features, receptor usage, cellular source and biological activities. The action of IFNs is mediated by a complex, partially overlapping, transcriptional program initiated by the interaction with specific receptors. Genetic diversity, with polymorphisms and mutations, can modulate the extent of IFN responses and the susceptibility to infections. Almost all viruses developed mechanisms to subvert the IFN response, involving both IFN induction and effector mechanisms. Interactions between IFN types may occur, for both antiviral and cell-modulatory effects, in a complex interplay, involving both synergistic and antagonistic effects. Interferon-associated diseases, not related to virus infections may occur, some of them frequently observed in IFN-treated patients. On the whole, IFNs are pleiotropic biologic response modifiers, that, upon activation of thousands genes, induce a broad spectrum of activities, regulating cell cycle, differentiation, plasma membrane molecules, release of mediators, etc., that can be relevant for cell proliferation, innate and adaptive immunity, hematopoiesis, angiogenesis and other body functions.

A nucleic-acid hydrolyzing single chain antibody confers resistance to DNA virus infection in hela cells and C57BL/6 mice

Viral protein neutralizing antibodies have been developed but they are limited only to the targeted virus and are often susceptible to antigenic drift. Here, we present an alternative strategy for creating virus-resistant cells and animals by ectopic expression of a nucleic acid hydrolyzing catalytic 3D8 single chain variable fragment (scFv), which has both DNase and RNase activities. HeLa cells (SCH7072) expressing 3D8 scFv acquired significant resistance to DNA viruses. Virus challenging with Herpes simplex virus (HSV) in 3D8 scFv transgenic cells and fluorescence resonance energy transfer (FRET) assay based on direct DNA cleavage analysis revealed that the induced resistance in HeLa cells was acquired by the nucleic acid hydrolyzing catalytic activity of 3D8 scFv. In addition, pseudorabies virus (PRV) infection in WT C57BL/6 mice was lethal, whereas transgenic mice (STG90) that expressed high levels of 3D8 scFv mRNA in liver, muscle, and brain showed a 56% survival rate 5 days after PRV intramuscular infection. The antiviral effects against DNA viruses conferred by 3D8 scFv expression in HeLa cells as well as an in vivo mouse system can be attributed to the nuclease activity that inhibits viral genome DNA replication in the nucleus and/or viral mRNA translation in the cytoplasm. Our results demonstrate that the nucleic-acid hydrolyzing activity of 3D8 scFv confers viral resistance to DNA viruses in vitro in HeLa cells and in an in vivo mouse system.

Most strategies for developing virus-resistant transgenic cells and animals are based on the concept of virus-derived resistance, in which dysfunctional virus-derived products are expressed to interfere with the pathogenic process of the virus in transgenic cells or animals. However, these viral protein targeting approaches are limited because they only target specific viruses and are susceptible to viral mutations. We describe a novel strategy that targets the viral genome itself, rather than viral gene products, to generate virus-resistant transgenic cells and animals. We functionally expressed 3D8 scFv which has both DNase and RNase activities, in HeLa cells and transgenic mice. We found that the transgenic cells and mice acquired complete resistance to two DNA viruses (HSV and PRV) without accumulating the virus, and showed delayed onset of disease symptoms. The antiviral effects against DNA viruses demonstrated in this study were caused by (1) DNase activity of 3D8 scFv in the nucleus, which inhibited DNA replication or RNA transcription and (2) 3D8 scFv RNase activity in the cytoplasm, which blocked protein translation. This strategy may facilitate control of a broad spectrum of viruses, including viruses uncharacterized at the molecular level, regardless of their genome type or variations in gene products.

A role for human brain pericytes in neuroinflammation

BACKGROUND

Brain inflammation plays a key role in neurological disease. Although much research has been conducted investigating inflammatory events in animal models, potential differences in human brain versus rodent models makes it imperative that we also study these phenomena in human cells and tissue.

METHODS

Primary human brain cell cultures were generated from biopsy tissue of patients undergoing surgery for drug-resistant epilepsy. Cells were treated with pro-inflammatory compounds IFNγ, TNFα, IL-1β, and LPS, and chemokines IP-10 and MCP-1 were measured by immunocytochemistry, western blot, and qRT-PCR. Microarray analysis was also performed on late passage cultures treated with vehicle or IFNγ and IL-1β.

RESULTS

Early passage human brain cell cultures were a mixture of microglia, astrocytes, fibroblasts and pericytes. Later passage cultures contained proliferating fibroblasts and pericytes only. Under basal culture conditions all cell types showed cytoplasmic NFκB indicating that they were in a non-activated state. Expression of IP-10 and MCP-1 were significantly increased in response to pro-inflammatory stimuli. The two chemokines were expressed in mixed cultures as well as cultures of fibroblasts and pericytes only. The expression of IP-10 and MCP-1 were regulated at the mRNA and protein level, and both were secreted into cell culture media. NFκB nuclear translocation was also detected in response to pro-inflammatory cues (except IFNγ) in all cell types. Microarray analysis of brain pericytes also revealed widespread changes in gene expression in response to the combination of IFNγ and IL-1β treatment including interleukins, chemokines, cellular adhesion molecules and much more.

CONCLUSIONS

Adult human brain cells are sensitive to cytokine challenge. As expected 'classical' brain immune cells, such as microglia and astrocytes, responded to cytokine challenge but of even more interest, brain pericytes also responded to such challenge with a rich repertoire of gene expression. Immune activation of brain pericytes may play an important role in communicating inflammatory signals to and within the brain interior and may also be involved in blood brain barrier (BBB) disruption . Targeting brain pericytes, as well as microglia and astrocytes, may provide novel opportunities for reducing brain inflammation and maintaining BBB function and brain homeostasis in human brain disease.

Antiviral activity of Rheum palmatum methanol extract and chrysophanol against Japanese encephalitis virus

Rheum palmatum, Chinese traditional herb, exhibits a great variety of anti-cancer and anti-viruses properties. This study rates antiviral activity of R. palmatum extracts and its components against Japanese encephalitis virus (JEV) in vitro. Methanol extract of R. palmatum contained higher levels of aloe emodin, chrysophanol, rhein, emodin and physcion than water extract. Methanol extract (IC₅₀ = 15.04 μg/ml) exhibited more potent inhibitory effects on JEV plaque reduction than water extract (IC₅₀ = 51.41 μg/ml). Meanwhile, IC₅₀ values determined by plaque reduction assay were 15.82 μg/ml for chrysophanol and 17.39 μg/ml for aloe-emodin, respectively. Virucidal activity of agents correlated with anti-JEV activity, while virucidal IC₅₀ values were 7.58 μg/ml for methanol extract, 17.36 μg/ml for water extract, 0.75 μg/ml for chrysophanol and 0.46 μg/ml for aloe-emodin, respectively. In addition, 10 μg/ml of extract, chrysophanol or aloe emodin caused 90 % inhibition of JEV yields in cells and significantly activated gamma activated sequence-driven promoters. Hence, methanol extract of R. palmatum and chrysophanol with high therapeutic index might be useful for development of antiviral agents against JEV.

STAT2 and IRF9: Beyond ISGF3

Cytokine signaling is mediated by the combinatorial usage of seven STAT proteins that form homo- or heterodimers involved in the regulation of specific transcriptional programs. Among STATs, STAT2 is classically known to dimerize with STAT1 and together with IRF9 forms the ISGF3 transcription factor complex that has long been considered a hallmark of activation by type I and type III interferons. However, accumulating evidence reveal distinct facets of STAT2 and IRF9 activity mediated by the segregation in alternative STAT1-independent complexes/pathways that are thought to trigger different transcriptional programs. The goal of this review is to summarize our current knowledge of the stimuli, regulatory mechanisms, and function of these alternative pathways.

The interdependent, overlapping, and differential roles of type I and II IFNs in the pathogenesis of experimental autoimmune encephalomyelitis

Type I IFNs (IFN-α and IFN-β) and type II IFN (IFN-γ) mediate both regulation and inflammation in multiple sclerosis, neuromyelitis optica, and in experimental autoimmune encephalomyelitis (EAE). However, the underlying mechanism for these Janus-like activities of type I and II IFNs in neuroinflammation remains unclear. Although endogenous type I IFN signaling provides a protective response in neuroinflammation, we find that when IFN-γ signaling is ablated, type I IFNs drive inflammation, resulting in exacerbated EAE. IFN-γ has a disease stage-specific opposing function in EAE. Treatment of mice with IFN-γ during the initiation phase of EAE leads to enhanced severity of disease. In contrast, IFN-γ treatment during the effector phase attenuated disease. This immunosuppressive activity of IFN-γ required functional type I IFN signaling. In IFN-α/β receptor-deficient mice, IFN-γ treatment during effector phase of EAE exacerbated disease. Using an adoptive transfer EAE model, we found that T cell-intrinsic type I and II IFN signals are simultaneously required to establish chronic EAE by encephalitogenic Th1 cells. However, in Th17 cells loss of either IFN signals leads to the development of a severe chronic disease. The data imply that type I and II IFN signals have independent but nonredundant roles in restraining encephalitogenic Th17 cells in vivo. Collectively, our data show that type I and II IFNs function in an integrated manner to regulate pathogenesis in EAE.

Cytokine synergy: an underappreciated contributor to innate anti-viral immunity

Inflammatory cytokines, such as tumor necrosis factor and the members of the interferon family, are potent mediators of the innate anti-viral immune response. The intracellular anti-viral states resulting from treatment of cultured cells with each of these molecules independently has been well studied; but, within complex tissues, the early inflammatory response is likely mediated by simultaneously expressed mixtures of these, and other, protective anti-viral cytokines. Such cytokine mixtures have been shown to induce potently synergistic anti-viral responses in vitro which are more complex than the simple summation of the individual cytokine response profiles. The physiological role of this 'cytokine synergy', however, remains largely unappreciated in vivo. This brief commentary will attempt to summarize the potential effects and mechanisms of anti-viral cytokine synergy as well as present several 'real-world' applications where this phenomenon might play an important role.

An effector phenotype of CD8+ T cells at the junction epithelium during clinical quiescence of herpes simplex virus 2 infection

Herpes simplex virus 2 infection is characterized by cycles of viral quiescence and reactivation. CD8(+) T cells persist at the site of viral reactivation, at the genital dermal-epidermal junction contiguous to neuronal endings of sensory neurons, for several months after herpes lesion resolution. To evaluate whether these resident CD8(+) T cells frequently encounter HSV antigen even during times of asymptomatic viral infection, we analyzed the transcriptional output of CD8(+) T cells captured by laser microdissection from human genital skin biopsy specimens during the clinically quiescent period of 8 weeks after lesion resolution. These CD8(+) T cells expressed a characteristic set of genes distinct from those of three separate control cell populations, and network and pathway analyses revealed that these T cells significantly upregulated antiviral genes such as GZMB, PRF1, INFG, IL-32, and LTA, carbohydrate and lipid metabolism-related genes such as GLUT-1, and chemotaxis and recruitment genes such as CCL5 and CCR1, suggesting a possible feedback mechanism for the recruitment of CD8(+) T cells to the site of infection. Many of these transcripts are known to have half-lives of <48 h, suggesting that cognate antigen is released frequently into the mucosa and that resident CD8(+) T cells act as functional effectors in controlling viral spread.

Microarray analysis of gene expression in West Nile virus-infected human retinal pigment epithelium

PURPOSE

To identify key genes differentially expressed in the human retinal pigment epithelium (hRPE) following low-level West Nile virus (WNV) infection.

METHODS

Primary hRPE and retinal pigment epithelium cell line (ARPE-19) cells were infected with WNV (multiplicity of infection 1). RNA extracted from mock-infected and WNV-infected cells was assessed for differential expression of genes using Affymetrix microarray. Quantitative real-time PCR analysis of 23 genes was used to validate the microarray results.

RESULTS

Functional annotation clustering of the microarray data showed that gene clusters involved in immune and antiviral responses ranked highly, involving genes such as chemokine (C-C motif) ligand 2 (CCL2), chemokine (C-C motif) ligand 5 (CCL5), chemokine (C-X-C motif) ligand 10 (CXCL10), and toll like receptor 3 (TLR3). In conjunction with the quantitative real-time PCR analysis, other novel genes regulated by WNV infection included indoleamine 2,3-dioxygenase (IDO1), genes involved in the transforming growth factor-β pathway (bone morphogenetic protein and activin membrane-bound inhibitor homolog [BAMBI] and activating transcription factor 3 [ATF3]), and genes involved in apoptosis (tumor necrosis factor receptor superfamily, member 10d [TNFRSF10D]). WNV-infected RPE did not produce any interferon-γ, suggesting that IDO1 is induced by other soluble factors, by the virus alone, or both.

CONCLUSIONS

Low-level WNV infection of hRPE cells induced expression of genes that are typically associated with the host cell response to virus infection. We also identified other genes, including IDO1 and BAMBI, that may influence the RPE and therefore outer blood-retinal barrier integrity during ocular infection and inflammation, or are associated with degeneration, as seen for example in aging.

Mucosal host immune response predicts the severity and duration of herpes simplex virus-2 genital tract shedding episodes

Herpes simplex virus-2 (HSV-2) shedding episodes in humans vary markedly in duration and virologic titer within an infected person over time, an observation that is unexplained. To evaluate whether host or virological factors more closely accounted for this variability, we combined measures of viral replication and CD8(+) lymphocyte density in genital biopsies, with a stochastic mathematical model of HSV-2 infection. Model simulations reproduced quantities of virus and duration of shedding detected in 1,003 episodes among 386 persons. In the simulations, local CD8(+) lymphocyte density in the mucosa at episode onset predicted peak HSV DNA copy number and whether genital lesions or subclinical shedding occurred. High density of CD8(+) T cells in the mucosa correlated with decreased infected cell lifespan and fewer infected epithelial cells before episode clearance. If infected cell lifespan increased by 15 min because of CD8(+) lymphocyte decay, then there was potential for a thousandfold increase in the number of infected cells. The model suggests that the rate of containment of infected cells by the peripheral mucosal immune system is the major driver of duration and severity of HSV-2 reactivation in the immunocompetent host.

Mechanisms employed by herpes simplex virus 1 to inhibit the interferon response

The interferon (IFN) family of cytokines constitutes potent inducers of innate antiviral responses that also influence adaptive immune processes. Despite eliciting such formidable cellular defense responses, viruses have evolved ways to interfere with the IFN response. Herpes simplex virus 1 (HSV-1) is an enveloped, dsDNA virus and a member of the herpesvirus family. Like other herpesvirus family members, HSV-1 has become highly specialized for its host and establishes a lifelong infection by undergoing latency within neurons. A leading reason for the success of HSV-1 as a pathogen results from its ability to evade the IFN response. Specifically, HSV-1 encodes several proteins that function to inhibit both IFN production and subsequent signal transduction. This review will identify and summarize the current understanding of viral proteins encoded by HSV-1 involved in the evasion of the IFN response.

Evasion of the mucosal innate immune system by herpes simplex virus type 2

Understanding the mechanisms by which herpes simplex virus (HSV) evades host immune defenses is critical to defining new approaches for therapy and prevention. We performed transcriptional analyses and immunocytochemistry on sequential biopsy specimens of lesional tissue from the acute through the posthealing phases of recurrent mucocutaneous HSV-2 infection. Histological analysis of these biopsy specimens during the acute stage revealed a massive infiltration of T cells, as well as monocytes/macrophages, a large amount of myeloid, and a small number of plasmacytoid dendritic cells, in the dermis of these lesional biopsy specimens. Type I interferon (IFN-beta and IFN-alpha) was poorly expressed and gamma IFN (IFN-gamma) potently induced during time periods in which we detected abundant amounts of HSV-2 antigens and HSV-2 RNA. IFN-stimulated genes were also markedly upregulated, with expression patterns that more closely matched those in primary human fibroblasts treated by IFN-gamma than those in fibroblasts treated by IFN-beta. Transcriptional arrays of the same lesional biopsy sites during healing and at 2 and 4 weeks posthealing revealed no HSV nucleic acids or antigen; however, there was persistent expression of IFN-gamma, with very low levels of IFN-beta and IFN-alpha. The findings of extremely low levels of IFN-alpha and IFN-beta, despite the presence of a large number of cells capable of synthesizing these substances, suggest a potent alteration in host defense during HSV-2 infection in vivo. HSV-2's blockade of the innate immune system's production of type I IFN may be a major factor in allowing the virus to break through host mucosal defenses.

Antiviral therapy for herpesvirus central nervous system infections: neonatal herpes simplex virus infection, herpes simplex encephalitis, and congenital cytomegalovirus infection

Herpesvirus infections of the central nervous system (CNS) are a significant cause of morbidity and mortality, including long-term neurologic sequelae. Among the family of herpesviruses, the most significant CNS infections are due to herpes simplex virus (HSV) and cytomegalovirus (CMV). The onset of HSV CNS infection can occur in neonates as well as older children and adults. CNS infection associated with CMV occurs predominantly in the perinatal period, but may also be seen rarely in children and adults, especially in immunocompromised individuals. Although advances in antiviral agents have led to improved outcomes, there is still a need for more effective treatments.

The addition of tumor necrosis factor plus beta interferon induces a novel synergistic antiviral state against poxviruses in primary human fibroblasts

Tumor necrosis factor (TNF) and members of the interferon (IFN) family have been shown to independently inhibit the replication of a variety of viruses. In addition, previous reports have shown that treatment with various combinations of these antiviral cytokines induces a synergistic antiviral state that can be significantly more potent than addition of any of these cytokines alone. The mechanism of this cytokine synergy and its effects on global gene expression, however, are not well characterized. Here, we use DNA microarray analysis to demonstrate that treatment of uninfected primary human fibroblasts with TNF plus IFN-beta induces a distinct synergistic state characterized by significant perturbations of several hundred genes which are coinduced by the individual cytokines alone, as well as the induction of more than 850 novel host cell genes. This synergy is mediated directly by the two ligands, not by intermediate secreted factors, and is necessary and sufficient to completely block the productive replication and spread of myxoma virus in human fibroblasts. In contrast, the replication of two other poxviruses, vaccinia virus and tanapox virus, are only partially inhibited in these cells by the synergistic antiviral state, whereas the spread of both of these viruses to neighboring cells was efficiently blocked. Taken together, our data indicate that the combination of TNF and IFN-beta induces a novel synergistic antiviral state that is highly distinct from that induced by either cytokine alone.

Virogenomics: the virus-host interaction revisited

Genomics tools allow us to assess gene expression ‘genome wide’ providing an unprecedented view on the host-side of the virus–host interaction. The success of the application of these tools crucially depends on our ability to reduce the total information load while increasing the information density of the data collected. In addition to the advanced data analysis algorithms, gene annotation-pathway databases, and theoretical models, specifically designed sets of complementary experiments are crucial in translating the collected genomics data into palatable knowledge. A better understanding of the molecular basis of virus–host interactions will support the rational design of improved and novel intervention strategies for viral infections.

Tumor necrosis factor and interferon: cytokines in harmony

Individually, tumor necrosis factor (TNF) and the various interferons frequently display strong antiviral activities. Certain combinations of these cytokines, however, induce a synergistic antiviral state which is distinct from that induced by either one alone. This novel synergistic antiviral state likely occurs through several possible mechanisms, involves multiple signaling pathways, and inhibits a wider range of viruses than the individual cytokines alone. While underappreciated when first discovered, this synergistic phenomenon is proving to be of a much broader scope than initially thought. More work is needed to refine our understanding of this observation and its physiological implications for anti-pathogen responses.