Herpes simplex virus 1 infection induces activation and subsequent inhibition of the IFI16 and NLRP3 inflammasomes. J Virol. 2013;87:5005-5018. [PMID: 23427152 DOI: 10.1128/jvi.00082-13]

Interleukin 1β receptor and synaptic dysfunction in recurrent brain infection with Herpes simplex virus type-1

Several experimental evidence suggests a link between brain Herpes simplex virus type-1 infection and the occurrence of Alzheimer's disease. However, the molecular mechanisms underlying this association are not completely understood. Among the molecular mediators of synaptic and cognitive dysfunction occurring after Herpes simplex virus type-1 infection and reactivation in the brain neuroinflammatory cytokines seem to occupy a central role. Here, we specifically reviewed literature reports dealing with the impact of neuroinflammation on synaptic dysfunction observed after recurrent Herpes simplex virus type-1 reactivation in the brain, highlighting the role of interleukins and, in particular, interleukin 1β as a possible target against Herpes simplex virus type-1-induced neuronal dysfunctions.

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

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

Overexpression of NLRP12 enhances antiviral immunity and alleviates herpes simplex keratitis via pyroptosis/IL-18/IFN-γ signaling

Herpes simplex keratitis (HSK) is a blinding disease caused by herpes simplex virus type 1 (HSV-1) infection, and rapid eradication of the virus from the affected cornea is imperative. Nod-like receptors (NLRs) are intracellular innate immune sensors closely associated with cell death, inflammation and immune responses. In this study, we investigated the role of NLRP12 in the antiviral immunology in HSK and the underlying mechanisms. We found that NLRP12 expression was significantly decreased in HSV-1-infected human corneal epithelial cells (HCE-Ts) and HSK mouse corneas. Overexpression of NLRP12 significantly reduced viral replication in infected HCE-Ts and functioned through inflammasome-mediated pyroptosis and downstream IL-18-IFN-γ axis. In HSK mouse models, overexpression of NLRP12 reduced viral replication in the cornea and alleviated HSK symptoms. This resulted from enhanced antiviral immune responses including the activation of specific immune cells in both the cornea and the draining lymph nodes. Specifically, the NLRP12-IL-18-IFN-γ axis regulated the interaction between infected corneal epithelial cells and macrophages. In conclusion, our study identified a role of NLRP12 in mediating pyroptosis and regulating antiviral immune responses. This novel finding opens the possibilities of NLRP12 as a viable target in the therapeutic strategies for HSV-1 infection.

Progress on H2B as a multifunctional protein related to pathogens

Histone H2B is a member of the core histones, which together with other histones form the nucleosome, the basic structural unit of chromosomes. As scientists delve deeper into histones, researchers gradually realize that histone H2B is not only an important part of nucleosomes, but also plays a momentous role in regulating gene transcription, acting as a receptor and antimicrobial action outside the nucleus. There are a variety of epigenetically modified sites in the H2B tail rich in arginine and lysine, which can occur in ubiquitination, phosphorylation, methylation, acetylation, etc. When stimulated by foreign factors such as bacteria, viruses or parasites, histone H2B can act as a receptor for the recognition of these pathogens, and induce an intrinsic immune response to enhance host defense. In addition, the extrachromosomal histone H2B is also an important anti-microorganism agent, which may be the key to the development of antibiotics in the future. This review aims to summarize the interaction between histone H2B and etiological agents and explore the role of H2B in epigenetic modifications, receptors and antimicrobial activity.

Herpes Simplex Virus ICP27 Protein Inhibits AIM 2-Dependent Inflammasome Influencing Pro-Inflammatory Cytokines Release in Human Pigment Epithelial Cells (hTert-RPE 1)

Although Herpes simplex virus type 1 (HSV-1) has been deeply studied, significant gaps remain in the fundamental understanding of HSV-host interactions: our work focused on studying the Infected Cell Protein 27 (ICP27) as an inhibitor of the Absent-in-melanoma-2 (AIM 2) inflammasome pathway, leading to reduced pro-inflammatory cytokines that influence the activation of a protective innate immune response to infection. To assess the inhibition of the inflammasome by the ICP27, hTert-immortalized Retinal Pigment Epithelial cells (hTert-RPE 1) infected with HSV-1 wild type were compared to HSV-1 lacking functional ICP27 (HSV-1∆ICP27) infected cells. The activation of the inflammasome by HSV-1∆ICP27 was demonstrated by quantifying the gene and protein expression of the inflammasome constituents using real-time PCR and Western blot. The detection of the cleavage of the pro-caspase-1 into the active form was performed by using a bioluminescent assay, while the quantification of interleukins 1β (IL-1β) and 18 (IL-18)released in the supernatant was quantified using an ELISA assay. The data showed that the presence of the ICP27 expressed by HSV-1 induces, in contrast to HSV-1∆ICP27 vector, a significant downregulation of AIM 2 inflammasome constituent proteins and, consequently, the release of pro-inflammatory interleukins into the extracellular environment reducing an effective response in counteracting infection.

MNDA, a PYHIN factor involved in transcriptional regulation and apoptosis control in leukocytes

Inflammation control is critical during the innate immune response. Such response is triggered by the detection of molecules originating from pathogens or damaged host cells by pattern-recognition receptors (PRRs). PRRs subsequently initiate intra-cellular signalling through different pathways, resulting in i) the production of inflammatory cytokines, including type I interferon (IFN), and ii) the initiation of a cascade of events that promote both immediate host responses as well as adaptive immune responses. All human PYRIN and HIN-200 domains (PYHIN) protein family members were initially proposed to be PRRs, although this view has been challenged by reports that revealed their impact on other cellular mechanisms. Of relevance here, the human PYHIN factor myeloid nuclear differentiation antigen (MNDA) has recently been shown to directly control the transcription of genes encoding factors that regulate programmed cell death and inflammation. While MNDA is mainly found in the nucleus of leukocytes of both myeloid (neutrophils and monocytes) and lymphoid (B-cell) origin, its subcellular localization has been shown to be modulated in response to genotoxic agents that induce apoptosis and by bacterial constituents, mediators of inflammation. Prior studies have noted the importance of MNDA as a marker for certain forms of lymphoma, and as a clinical prognostic factor for hematopoietic diseases characterized by defective regulation of apoptosis. Abnormal expression of MNDA has also been associated with altered levels of cytokines and other inflammatory mediators. Refining our comprehension of the regulatory mechanisms governing the expression of MNDA and other PYHIN proteins, as well as enhancing our definition of their molecular functions, could significantly influence the management and treatment strategies of numerous human diseases. Here, we review the current state of knowledge regarding PYHIN proteins and their role in innate and adaptive immune responses. Emphasis will be placed on the regulation, function, and relevance of MNDA expression in the control of gene transcription and RNA stability during cell death and inflammation.

Advances in the mechanism of inflammasomes activation in herpes virus infection

Herpesviruses, prevalent DNA viruses with a double-stranded structure, establish enduring infections and play a part in various diseases. Despite their deployment of multiple tactics to evade the immune system, both localized and systemic inflammatory responses are triggered by the innate immune system's recognition of them. Recent progress has offered more profound understandings of the mechanisms behind the activation of the innate immune system by herpesviruses, specifically through inflammatory signaling. This process encompasses the initiation of an intracellular nucleoprotein complex, the inflammasome associated with inflammation.Following activation, proinflammatory cytokines such as IL-1β and IL-18 are released by the inflammasome, concurrently instigating a programmed pathway for cell death. Despite the structural resemblances between herpesviruses, the distinctive methods of inflammatory activation and the ensuing outcomes in diseases linked to the virus exhibit variations.The objective of this review is to emphasize both the similarities and differences in the mechanisms of inflammatory activation among herpesviruses, elucidating their significance in diseases resulting from these viral infections.Additionally, it identifies areas requiring further research to comprehensively grasp the impact of this crucial innate immune signaling pathway on the pathogenesis of these prevalent viruses.

The role of pyroptosis in viral infection

Pyroptosis, also known as inflammatory necrosis, is a form of programmed cell death, which is an important natural immune response. Pyroptosis plays a major role in combating pathogenic infections. The mechanism of pyroptosis is distinct from other forms of cell death and is characterized by its dependence on inflammatory caspases (mainly caspases 1, 4, 5, and 11). Activation of NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammatory vesicles is involved in caspase-1 activation and cleavage, which in turn triggers cleavage and multimerization of multiple gasdermin family members, including gasdermin-D (GSDMD). This further leads to cell perforation and cellular distension, causing cell membrane rupture, resulting in a massive efflux of cell contents, which triggers inflammatory reactions. In recent years, detailed study of viral diseases, has demonstrated that pyroptosis is closely associated with the development of viral diseases. This article focuses on the mechanism of pyroptosis and the connection between pyroptosis and viral infection.

Multi-targeted loss of the antigen presentation molecule MR1 during HSV-1 and HSV-2 infection

The major histocompatibility complex (MHC), Class-I-related (MR1) molecule presents microbiome-synthesized metabolites to Mucosal-associated invariant T (MAIT) cells, present at sites of herpes simplex virus (HSV) infection. During HSV type 1 (HSV-1) infection there is a profound and rapid loss of MR1, in part due to expression of unique short 3 protein. Here we show that virion host shutoff RNase protein downregulates MR1 protein, through loss of MR1 transcripts. Furthermore, a third viral protein, infected cell protein 22, also downregulates MR1, but not classical MHC-I molecules. This occurs early in the MR1 trafficking pathway through proteasomal degradation. Finally, HSV-2 infection results in the loss of MR1 transcripts, and intracellular and surface MR1 protein, comparable to that seen during HSV-1 infection. Thus HSV coordinates a multifaceted attack on the MR1 antigen presentation pathway, potentially protecting infected cells from MAIT cell T cell receptor-mediated detection at sites of primary infection and reactivation.

ER stress induces caspase-2-tBID-GSDME-dependent cell death in neurons lytically infected with herpes simplex virus type 2

Neurotropic viruses, including herpes simplex virus (HSV) types 1 and 2, have the capacity to infect neurons and can cause severe diseases. This is associated with neuronal cell death, which may contribute to morbidity or even mortality if the infection is not controlled. However, the mechanistic details of HSV-induced neuronal cell death remain enigmatic. Here, we report that lytic HSV-2 infection of human neuron-like SH-SY5Y cells and primary human and murine brain cells leads to cell death mediated by gasdermin E (GSDME). HSV-2-induced GSDME-mediated cell death occurs downstream of replication-induced endoplasmic reticulum stress driven by inositol-requiring kinase 1α (IRE1α), leading to activation of caspase-2, cleavage of the pro-apoptotic protein BH3-interacting domain death agonist (BID), and mitochondria-dependent activation of caspase-3. Finally, necrotic neurons released alarmins, which activated inflammatory responses in human iPSC-derived microglia. In conclusion, lytic HSV infection in neurons activates an ER stress-driven pathway to execute GSDME-mediated cell death and promote inflammation.

PRRSV inhibited the proliferation of CSFV by inducing IL-1β maturation via NLRP3 inflammasome activation

PRRSV and CSFV are both common infectious pathogens in porcine populations, posing significant threats to the healthy development of the porcine industry. Vaccine immunization is the main way to prevent and control these two diseases. Increasing studies have demonstrated that there is an interaction between PRRSV co-infection and CSFV vaccine immune failure. To investigate the effect of PRRSV infection on CSFV proliferation and its molecular mechanism, the proliferation dynamics of PRRSV/CSFV, the NLRP3 inflammasome components, and IL-1β expression levels were detected in PRRSV/CSFV alone- or co-infection. Subsequently, the relationship between inflammasome activation, IL-1β expression, and CSFV proliferation was analyzed through the construction of an inflammasome activation model, specific siRNA interference, and specific inhibitor treatment. The results showed that CSFV infection had a poor regulatory effect on NLRP3 inflammasome activation and IL-1β maturation, but PRRSV and CSFV co-infection could significantly up-regulate the expression of NLRP3 and ASC, induce Caspase-1 activation, and promote IL-1β maturation. It was further determined that NLRP3 inflammasome components played important roles in IL-1β maturation and inhibiting CSFV proliferation by PRRSV. Additional experiments indicated that PRRSV replication is essential for NLRP3 inflammasome activation, IL-1β maturation, and CSFV proliferation inhibition. More importantly, NLRP3 inflammasome activation is regulated by the TLR4-MyD88-NF-κB pathways. In conclusion, PRRSV infection induced IL-1β maturation by activating the NLRP3 inflammasome through the TLR4-MyD88-NF-κB pathways and then inhibited the proliferation of CSFV. These data further improved the theoretical basis for PRRSV inducing inflammatory factors and leading to the failure of CSFV immunization.

Pseudorabies virus infection activates the NLRP3 and IFI16 inflammasomes to trigger pyroptosis

Pseudorabies virus (PRV) preferably invades neural tissue and various organs, whereupon may result in multisystemic lesions. Pyroptosis mediated by proteolytic cleavage of gasdermin D (GSDMD) by inflammatory caspases (caspase-1/4/5/11), is closely associated with the activation of inflammasomes, a multiprotein proinflammatory complex. However, further studies on the mechanisms regarding PRV-induced pyroptosis in its natural host are required. Herein, it is demonstrated that PRV infection triggered GSDMD- not GSDME-mediated pyroptosis in porcine alveolar macrophage cells, resulting in increased secretion of IL-1β and LDH. During this process, caspase-1 was activated and participated in the cleaving of GSDMD. Interestingly, we found that the viral replication process or protein production is required to induce pyroptotic cell death. Also, our findings showed that PRV triggered NLRP3 inflammasome activation, which was associated with the production of reactive oxygen species (ROS) and potassium efflux. In addition to the NLRP3 inflammasome, the IFI16 inflammasome was also activated. Importantly, the NLRP3- and IFI16- inflammasomes were both involved in pyroptosis during PRV infection. Finally, we observed that the cleaved GSDMD, activated caspase-1, increased IFI16 levels, and elevated NLRP3 protein in PRV-infected tissues (brain and lung), supporting the occurrence of pyroptosis and the activation of NLRP3- and IFI16- inflammasome in PRV-infected pigs. This research advances our understanding of the PRV-mediated inflammatory response and cell death pathways, providing a deeper knowledge of effective treatments for pseudorabies.

Effects of AIM2 and IFI16 on Infectious Diseases and Inflammation

Both absent in melanoma 2 (AIM2) and interferon-inducible protein 16 (IFI16) are intracellular innate immune receptors that recognize double-stranded DNA released during pathogenic infection, leading to the assembly of the inflammasome. The assembly of the inflammasome results in the secretion of bioactive interleukin (IL)-1β and IL-18 and induces cell death through an inflammatory process called pyroptosis. Although the AIM2 inflammasome is generally harmful in the context of some aseptic inflammatory illnesses, it plays a protective role in infectious diseases. During inflammatory processes, there is competition between IFI16 and AIM2. In this review, we explore the impacts of IFI16 and AIM2 in infectious disease and aseptic inflammation, respectively, and how they compete.

The NLRP3 inflammasome in viral infection (Review)

The interplay between pathogen and host determines the immune response during viral infection. The Nod‑like receptor (NLR) protein 3 inflammasome is a multiprotein complex that induces the activation of inflammatory caspases and the release of IL‑1β, which play an important role in the innate immune responses. In the present review, the mechanisms of the NLR family pyrin domain containing 3 inflammasome activation and its dysregulation in viral infection were addressed.

IFI16 phase separation via multi-phosphorylation drives innate immune signaling

The interferon inducible protein 16 (IFI16) is a prominent sensor of nuclear pathogenic DNA, initiating innate immune signaling and suppressing viral transcription. However, little is known about mechanisms that initiate IFI16 antiviral functions or its regulation within the host DNA-filled nucleus. Here, we provide in vitro and in vivo evidence to establish that IFI16 undergoes liquid-liquid phase separation (LLPS) nucleated by DNA. IFI16 binding to viral DNA initiates LLPS and induction of cytokines during herpes simplex virus type 1 (HSV-1) infection. Multiple phosphorylation sites within an intrinsically disordered region (IDR) function combinatorially to activate IFI16 LLPS, facilitating filamentation. Regulated by CDK2 and GSK3β, IDR phosphorylation provides a toggle between active and inactive IFI16 and the decoupling of IFI16-mediated cytokine expression from repression of viral transcription. These findings show how IFI16 switch-like phase transitions are achieved with temporal resolution for immune signaling and, more broadly, the multi-layered regulation of nuclear DNA sensors.

Race between virus and inflammasomes: inhibition or escape, intervention and therapy

The inflammasome is a multiprotein complex that further regulates cell pyroptosis and inflammation by activating caspase-1. The assembly and activation of inflammasome are associated with a variety of diseases. Accumulative studies have shown that inflammasome is a key modulator of the host's defense response to viral infection. Indeed, it has been established that activation of inflammasome occurs during viral infection. At the same time, the host has evolved a variety of corresponding mechanisms to inhibit unnecessary inflammasome activation. Therefore, here, we review and summarize the latest research progress on the interaction between inflammosomes and viruses, highlight the assembly and activation of inflammosome in related cells after viral infection, as well as the corresponding molecular regulatory mechanisms, and elucidate the effects of this activation on virus immune escape and host innate and adaptive immune defenses. Finally, we also discuss the potential therapeutic strategies to prevent and/or ameliorate viral infection-related diseases via targeting inflammasomes and its products.

HSV-1 selectively packs the transcription factor Oct-1 into EVs to facilitate its infection

HSV-1 hijacks the cellular vesicular secretion system and promotes the secretion of extracellular vesicles (EVs) from infected cells. This is believed to facilitate the maturation, secretion, intracellular transportation and immune evasion of the virus. Intriguingly, previous studies have shown that noninfectious EVs from HSV-1-infected cells exert antiviral effects on HSV-1 and have identified host restrictive factors, such as STING, CD63, and Sp100 packed in these lipid bilayer-enclosed vesicles. Octamer-binding transcription factor-1 (Oct-1) is shown here to be a pro-viral cargo in non-virion-containing EVs during HSV-1 infection and serves to facilitate virus dissemination. Specifically, during HSV-1 infection, the nuclear localized transcription factor Oct-1 displayed punctate cytosolic staining that frequently colocalized with VP16 and was increasingly secreted into the extracellular space. HSV-1 grown in cells bereft of Oct-1 (Oct-1 KO) was significantly less efficient at transcribing viral genes during the next round of infection. In fact, HSV-1 promoted increased exportation of Oct-1 in non-virion-containing EVs, but not the other VP16-induced complex (VIC) component HCF-1, and EV-associated Oct-1 was promptly imported into the nucleus of recipient cells to facilitate the next round of HSV-1 infection. Interestingly, we also found that EVs from HSV-1-infected cells primed cells for infection by another RNA virus, vesicular stomatitis virus. In summary, this investigation reports one of the first pro-viral host proteins packed into EVs during HSV-1 infection and underlines the heterogenetic nature and complexity of these noninfectious double-lipid particles.

Recent advances in ZBP1-derived PANoptosis against viral infections

Innate immunity is an important first line of defense against pathogens, including viruses. These pathogen- and damage-associated molecular patterns (PAMPs and DAMPs, respectively), resulting in the induction of inflammatory cell death, are detected by specific innate immune sensors. Recently, Z-DNA binding protein 1 (ZBP1), also called the DNA-dependent activator of IFN regulatory factor (DAI) or DLM1, is reported to regulate inflammatory cell death as a central mediator during viral infection. ZBP1 is an interferon (IFN)-inducible gene that contains two Z-form nucleic acid-binding domains (Zα1 and Zα2) in the N-terminus and two receptor-interacting protein homotypic interaction motifs (RHIM1 and RHIM2) in the middle, which interact with other proteins with the RHIM domain. By sensing the entry of viral RNA, ZBP1 induces PANoptosis, which protects host cells against viral infections, such as influenza A virus (IAV) and herpes simplex virus (HSV1). However, some viruses, particularly coronaviruses (CoVs), induce PANoptosis to hyperactivate the immune system, leading to cytokine storm, organ failure, tissue damage, and even death. In this review, we discuss the molecular mechanism of ZBP1-derived PANoptosis and pro-inflammatory cytokines that influence the double-edged sword of results in the host cell. Understanding the ZBP1-derived PANoptosis mechanism may be critical for improving therapeutic strategies.

When herpes simplex virus encephalitis meets antiviral innate immunity

Herpes simplex virus (HSV) is the most common pathogen of infectious encephalitis, accounting for nearly half of the confirmed cases of encephalitis. Its clinical symptoms are often atypical. HSV PCR in cerebrospinal fluid is helpful for diagnosis, and the prognosis is usually satisfactory after regular antiviral treatment. Interestingly, some patients with recurrent encephalitis have little antiviral effect. HSV PCR in cerebrospinal fluid is negative, but glucocorticoid has a significant effect after treatment. Specific antibodies, such as the NMDA receptor antibody, the GABA receptor antibody, and even some unknown antibodies, can be isolated from cerebrospinal fluid, proving that the immune system contributes to recurrent encephalitis, but the specific mechanism is still unclear. Based on recent studies, we attempt to summarize the relationship between herpes simplex encephalitis and innate immunity, providing more clues for researchers to explore this field further.

Pyroptosis in Antiviral Immunity

Pyroptosis is a form of lytic, programmed cell death that functions as an innate immune effector mechanism to facilitate host defense against pathogenic microorganisms, including viruses. This type of proinflammatory cell death is orchestrated by proteolytic activation of human or mouse caspase-1, mouse caspase-11 and human caspase-4 and caspase-5 in response to infectious and inflammatory stimuli. Induction of pyroptosis requires either a canonical inflammasome responsible for caspase-1 activation or a noncanonical complex composed of caspase-11 in mice or caspase-4 or caspase-5 in humans. Recent studies have identified the pore-forming protein gasdermin D, a substrate of these inflammatory caspases, as an executioner of pyroptosis. The membrane pores formed by gasdermin D facilitate release of proinflammatory cytokines IL-1β and IL-18 and consequent biologic effects of these cytokines together with other released components. Pyroptosis, like other forms of programmed cell death, helps eliminate infected cells and thereby restricts the replicative niche, undermining survival and proliferation of intracellular pathogens. This includes viruses as well as bacteria, where ample evidence supports a critical role for inflammasome effector functions and cell death in host defense. Viruses have evolved their own mechanisms to modulate inflammasome signaling and pyroptosis. Here, we review the current literature regarding the role of pyroptosis in antiviral immune responses.

Whole blood transcriptome analysis in dairy calves experimentally challenged with bovine herpesvirus 1 (BoHV-1) and comparison to a bovine respiratory syncytial virus (BRSV) challenge

Bovine herpesvirus 1 (BoHV-1), is associated with several clinical syndromes in cattle, among which bovine respiratory disease (BRD) is of particular significance. Despite the importance of the disease, there is a lack of information on the molecular response to infection via experimental challenge with BoHV-1. The objective of this study was to investigate the whole-blood transcriptome of dairy calves experimentally challenged with BoHV-1. A secondary objective was to compare the gene expression results between two separate BRD pathogens using data from a similar challenge study with BRSV. Holstein-Friesian calves (mean age (SD) = 149.2 (23.8) days; mean weight (SD) = 174.6 (21.3) kg) were either administered BoHV-1 inoculate (1 × 10⁷/mL × 8.5 mL) (n = 12) or were mock challenged with sterile phosphate buffered saline (n = 6). Clinical signs were recorded daily from day (d) -1 to d 6 (post-challenge), and whole blood was collected in Tempus RNA tubes on d six post-challenge for RNA-sequencing. There were 488 differentially expressed (DE) genes (p < 0.05, False Discovery rate (FDR) < 0.10, fold change ≥2) between the two treatments. Enriched KEGG pathways (p < 0.05, FDR <0.05); included Influenza A, Cytokine-cytokine receptor interaction and NOD-like receptor signalling. Significant gene ontology terms (p < 0.05, FDR <0.05) included defence response to virus and inflammatory response. Genes that are highly DE in key pathways are potential therapeutic targets for the treatment of BoHV-1 infection. A comparison to data from a similar study with BRSV identified both similarities and differences in the immune response to differing BRD pathogens.

The CARD8 inflammasome in HIV infection

The biggest challenge to immune control of HIV infection is the rapid within-host viral evolution, which allows selection of viral variants that escape from T cell and antibody recognition. Thus, it is impossible to clear HIV infection without targeting "immutable" components of the virus. Unlike the adaptive immune system that recognizes cognate epitopes, the CARD8 inflammasome senses the essential enzymatic activity of the HIV-1 protease, which is immutable for the virus. Hence, all subtypes of HIV clinical isolates can be recognized by CARD8. In HIV-infected cells, the viral protease is expressed as a subunit of the viral Gag-Pol polyprotein and remains functionally inactive prior to viral budding. A class of anti-HIV drugs, the non-nucleoside reverse transcriptase inhibitors (NNRTIs), can promote Gag-pol dimerization and subsequent premature intracellular activation of the viral protease. NNRTI treatment triggers CARD8 inflammasome activation, which leads to pyroptosis of HIV-infected CD4⁺ T cells and macrophages. Targeting the CARD8 inflammasome can be a potent and broadly effective strategy for HIV eradication.

Inflammasomes in Human Immunodeficiency Virus Type 1 Infection

Innate immune responses are the host's first line of defense against human immunodeficiency virus type 1 (HIV-1) infection, with pattern recognition receptors detecting viral specific pathogen-associated molecular patterns and initiating antiviral responses. In response to HIV-1 nucleic acids or proteins, some pattern recognition receptors have the ability to assemble a large multiprotein complex called the inflammasome, which triggers pro-inflammatory cytokine release and a form of lytic programmed cell death called pyroptosis. Here, we review our current understanding of the mechanism of the inflammasome in sensing HIV-1 infection. Furthermore, we discuss the contribution of inflammasome activation in HIV-1 pathogenesis as well as potential strategies of targeting inflammasome activation for the treatment of HIV-1 infection.

Promiscuous Inflammasomes: The False Dichotomy of RNA/DNA Virus-Induced Inflammasome Activation and Pyroptosis

It is well-known that viruses activate various inflammasomes, which can initiate the programmed cell death pathway known as pyroptosis, subsequently leading to cell lysis and release of inflammatory cytokines IL-1β and IL-18. This pathway can be triggered by various sensors, including, but not limited to, NLRP3, AIM2, IFI16, RIG-I, and NLRC4. Many viruses are known either to activate or inhibit inflammasomes as a part of the innate immune response or as a mechanism of pathogenesis. Early research in the field of virus-induced pyroptosis suggested a dichotomy, with RNA viruses activating the NLRP3 inflammasome and DNA viruses activating the AIM2 inflammasome. More recent research has shown that this dichotomy may not be as distinct as once thought. It seems many viruses activate multiple inflammasome sensors. Here, we detail which viruses fit the dichotomy as well as many that appear to defy this clearly false dichotomy. It seems likely that most, if not all, viruses activate multiple inflammasome sensors, and future research should focus on expanding our understanding of inflammasome activation in a variety of tissue types as well as virus activation of multiple inflammasomes, challenging biases that stemmed from early literature in this field. Here, we review primarily research performed on human viruses but also include details regarding animal viruses whenever possible.

Role of Caspases and Gasdermin A during HSV-1 Infection in Mice

Herpes simplex virus type 1 (HSV-1) infection can manifest locally as mucocutaneous lesions or keratitis and can also spread to the central nervous system to cause encephalitis. HSV-1 establishes a lifelong latent infection and neither cure nor vaccine is currently available. The innate immune response is the first line of defense against infection. Caspases and gasdermins are important components of innate immunity. Caspases are a family of cysteine proteases, most of which mediate regulated cell death. Gasdermins are a family of pore-forming proteins that trigger lytic cell death. To determine whether caspases or gasdermins contribute to innate immune defenses against HSV-1, we screened mice deficient in specific cell death genes. Our results indicate a modest role for caspase-6 in defense against HSV-1. Further, Asc–/–Casp1/11–/– mice also had a modest increased susceptibility to HSV-1 infection. Caspase-7, -8, and -14 did not have a notable role in controlling HSV-1 infection. We generated Gsdma1-Gsdma2-Gsdma3 triple knockout mice, which also had normal susceptibility to HSV-1. We confirmed that the previously published importance of RIPK3 during systemic HSV-1 infection also holds true during skin infection. Overall, our data highlight that as a successful pathogen, HSV-1 has multiple ways to evade host innate immune responses.

Pseudorabies Virus EP0 Antagonizes the Type I Interferon Response via Inhibiting IRF9 Transcription

The alphaherpesvirus pseudorabies virus (PRV) is the etiologic agent of swine Aujeszky's disease, which can cause huge economic losses to the pig industry. PRV can overcome a type I interferon (IFN)-induced antiviral state in host cells through its encoded EP0 protein. However, the exact role of EP0 in this process is poorly defined. Here, we report that EP0 transcriptionally represses IFN regulatory factor 9 (IRF9), a critical component in the IFN signaling pathway, thereby reducing the cellular levels of IRF9 and inhibiting IFN-induced gene transcription. This activity of EP0 is mediated by its C-terminal region independently of the RING domain. Moreover, compared with EP0 wild-type PRV, EP0-deficient PRV loses the ability to efficiently decrease cellular IRF9, while reintroducing the C-terminal region of EP0 back into the EP0-deficient virus restores the activity. Together, these results suggest that EP0 can transcriptionally modulate IRF9-mediated antiviral pathways through its C-terminal region, contributing to PRV innate immune evasion. IMPORTANCE Alphaherpesviruses can establish lifelong infections and cause many diseases in humans and animals. Pseudorabies virus (PRV) is a swine alphaherpesvirus that threatens pig production. Using PRV as a model, we found that alphaherpesvirus can utilize its encoded early protein EP0 to inhibit the IFN-induced upregulation of antiviral proteins by reducing the basal expression levels of IRF9 through repressing its transcription. Our findings reveal a mechanism employed by alphaherpesvirus to evade the immune response and indicate that EP0 is an important viral protein in pathogenesis and a potential target for antiviral drug development.

Herpes Simplex Virus 1 Induces Microglia Gasdermin D-Dependent Pyroptosis Through Activating the NLR Family Pyrin Domain Containing 3 Inflammasome

Herpes simplex virus type 1 (HSV-1) is a highly prevalent virus in humans and causes severe forms of inflammation, such as herpes simplex encephalitis (HSE). Pyroptosis is a new inflammatory cell death triggered by inflammasome and cysteine-requiring aspartate protease-1 (caspase-1) activation. Nonetheless, HSV-1 induces encephalitis, and cell death mechanisms are not understood. In this study, we confirmed for the first time that the DNA virus HSV-1 triggers Gasdermin D-dependent pyroptosis by activating NLR family pyrin domain containing 3 (NLRP3) inflammasomes in mouse microglia, leading to mature IL-1β production and active caspase-1 (p10) release. Inhibition of microglial NLRP3 inflammasome activation suppressed HSV-1-induced Gasdermin D-dependent pyroptosis. In addition, NLRP3 and IL-1β expression levels were significantly increased in the mouse model of herpes simplex encephalitis compared with normal mice without viral infection. Collectively, our data revealed that the activation of inflammasomes and GSDMD-dependent pyroptosis is the mechanism of HSV-1 inducing inflammation and provides treatment targets for viral inflammation.

Programmed Cell Death-Dependent Host Defense in Ocular Herpes Simplex Virus Infection

Herpes simplex virus type 1 (HSV1) remains one of the most ubiquitous human pathogens on earth. The classical presentation of HSV1 infection occurs as a recurrent lesions of the oral mucosa commonly refer to as the common cold sore. However, HSV1 also is responsible for a range of ocular diseases in immunocompetent persons that are of medical importance, causing vision loss that may result in blindness. These include a recurrent corneal disease, herpes stromal keratitis, and a retinal disease, acute retinal necrosis, for which clinically relevant animal models exist. Diverse host immune mechanisms mediate control over herpesviruses, sustaining lifelong latency in neurons. Programmed cell death (PCD) pathways including apoptosis, necroptosis, and pyroptosis serve as an innate immune mechanism that eliminates virus-infected cells and regulates infection-associated inflammation during virus invasion. These different types of cell death operate under distinct regulatory mechanisms but all server to curtail virus infection. Herpesviruses, including HSV1, have evolved numerous cell death evasion strategies that restrict the hosts ability to control PCD to subvert clearance of infection and modulate inflammation. In this review, we discuss the key studies that have contributed to our current knowledge of cell death pathways manipulated by HSV1 and relate the contributions of cell death to infection and potential ocular disease outcomes.

The Interplay between Viruses and Host DNA Sensors

DNA virus infections are often lifelong and can cause serious diseases in their hosts. Their recognition by the sensors of the innate immune system represents the front line of host defence. Understanding the molecular mechanisms of innate immunity responses is an important prerequisite for the design of effective antivirotics. This review focuses on the present state of knowledge surrounding the mechanisms of viral DNA genome sensing and the main induced pathways of innate immunity responses. The studies that have been performed to date indicate that herpesviruses, adenoviruses, and polyomaviruses are sensed by various DNA sensors. In non-immune cells, STING pathways have been shown to be activated by cGAS, IFI16, DDX41, or DNA-PK. The activation of TLR9 has mainly been described in pDCs and in other immune cells. Importantly, studies on herpesviruses have unveiled novel participants (BRCA1, H2B, or DNA-PK) in the IFI16 sensing pathway. Polyomavirus studies have revealed that, in addition to viral DNA, micronuclei are released into the cytosol due to genotoxic stress. Papillomaviruses, HBV, and HIV have been shown to evade DNA sensing by sophisticated intracellular trafficking, unique cell tropism, and viral or cellular protein actions that prevent or block DNA sensing. Further research is required to fully understand the interplay between viruses and DNA sensors.

Herpesviruses and Inflammasomes: One Sensor Does Not Fit All

Herpesviruses are ubiquitous double-stranded DNA viruses that cause lifelong infections and are associated with a variety of diseases. While they have evolved multiple mechanisms to evade the immune system, they are all recognized by the innate immune system, which can lead to both localized and systemic inflammation. A more recently appreciated mechanism of herpesvirus innate immune activation is through inflammasome signaling. The inflammasome is an intracellular multiprotein complex that, when activated, leads to the release of proinflammatory cytokines, including IL-1β and IL-18, and activation of the inflammatory programed cell death pathway known as pyroptosis. Despite the herpesviruses sharing a similar structure, their mechanisms of inflammasome activation and the consequences of inflammasome activation in cases of virus-associated disease are not uniform. This review will highlight the similarities and differences among herpesviruses with regard to their mechanisms of inflammasome activation and impacts on diseases caused by herpesviruses. Furthermore, it will identify areas where additional studies are warranted to better understand the impact of this important innate immune signaling program on the pathogenesis of these common viruses.

Role of Mitochondrial Nucleic Acid Sensing Pathways in Health and Patho-Physiology

Mitochondria, in symbiosis with the host cell, carry out a wide variety of functions from generating energy, regulating the metabolic processes, cell death to inflammation. The most prominent function of mitochondria relies on the oxidative phosphorylation (OXPHOS) system. OXPHOS heavily influences the mitochondrial-nuclear communication through a plethora of interconnected signaling pathways. Additionally, owing to the bacterial ancestry, mitochondria also harbor a large number of Damage Associated Molecular Patterns (DAMPs). These molecules relay the information about the state of the mitochondrial health and dysfunction to the innate immune system. Consequently, depending on the intracellular or extracellular nature of detection, different inflammatory pathways are elicited. One group of DAMPs, the mitochondrial nucleic acids, hijack the antiviral DNA or RNA sensing mechanisms such as the cGAS/STING and RIG-1/MAVS pathways. A pro-inflammatory response is invoked by these signals predominantly through type I interferon (T1-IFN) cytokines. This affects a wide range of organ systems which exhibit clinical presentations of auto-immune disorders. Interestingly, tumor cells too, have devised ingenious ways to use the mitochondrial DNA mediated cGAS-STING-IRF3 response to promote neoplastic transformations and develop tumor micro-environments. Thus, mitochondrial nucleic acid-sensing pathways are fundamental in understanding the source and nature of disease initiation and development. Apart from the pathological interest, recent studies also attempt to delineate the structural considerations for the release of nucleic acids across the mitochondrial membranes. Hence, this review presents a comprehensive overview of the different aspects of mitochondrial nucleic acid-sensing. It attempts to summarize the nature of the molecular patterns involved, their release and recognition in the cytoplasm and signaling. Finally, a major emphasis is given to elaborate the resulting patho-physiologies.

Activation and Immune Regulation Mechanisms of PYHIN Family During Microbial Infection

The innate immune system defenses against pathogen infections via patten-recognition receptors (PRRs). PRRs initiate immune responses by recognizing pathogen-associated molecular patterns (PAMPs), including peptidoglycan, lipopolysaccharide, and nucleic acids. Several nucleic acid sensors or families have been identified, such as RIG-I-like receptors (RLRs), Toll-like receptors (TLRs), cyclic GMP-AMP synthase (cGAS), and PYHIN family receptors. In recent years, the PYHIN family cytosolic DNA receptors have increased attention because of their important roles in initiating innate immune responses. The family members in humans include Absent in melanoma 2 (AIM2), IFN-γ inducible protein 16 (IFI16), interferon-inducible protein X (IFIX), and myeloid cell nuclear differentiation antigen (MNDA). The PYHIN family members are also identified in mice, including AIM2, p202, p203, p204, and p205. Herein, we summarize recent advances in understanding the activation and immune regulation mechanisms of the PYHIN family during microbial infection. Furthermore, structural characterizations of AIM2, IFI16, p202, and p204 provide more accurate insights into the signaling mechanisms of PYHIN family receptors. Overall, the molecular details will facilitate the development of reagents to defense against viral infections.

Functions and roles of IFIX, a member of the human HIN-200 family, in human diseases

Pyrin and hematopoietic expression, interferon-inducible nature, and nuclear localization (HIN) domain family member 1 (PYHIN1), also known as IFIX, belongs to the family of pyrin proteins. This family includes structurally and functionally related mouse (e.g., p202, p203, and p204 proteins) and human (e.g., the interferon-inducible protein 16, absent in melanoma 2 protein, myeloid cell nuclear differentiation antigen, and pyrin and HIN domain family 1 or IFIX) proteins. The IFIX protein belongs to the HIN-200 family of interferon-inducible proteins that have a 200-amino acid signature motif at their C-termini. The increased expression of pyrin proteins in most cell types inhibits cell cycle control and modulates cell survival. Consistent with this role for pyrin proteins, IFIX is a potential antiviral DNA sensor that is essential for immune responses, the detection of viral DNA in the nucleus and cytoplasm, and the binding of foreign DNA via its HIN domain in a sequence non-specific manner. By promoting the ubiquitination and subsequent degradation of MDM2, IFIX acts as a tumor suppressor, thereby leading to p53/TP53 stabilization, HDAC1 regulation via the ubiquitin-proteasome pathway, and tumor-cell-specific silencing of the maspin gene. These data demonstrate that the potential molecular mechanism(s) underlying the action of the IFIX protein might be associated with the development of human diseases, such as viral infections, malignant tumors, and autoimmune diseases. This review summarizes the current insights into IFIX functions and how its regulation affects the outcomes of various human diseases.

The evolution of regulated cell death pathways in animals and their evasion by pathogens

The coevolution of host-pathogen interactions underlies many human physiological traits associated with protection from or susceptibility to infections. Among the mechanisms that animals utilize to control infections are the regulated cell death pathways of pyroptosis, apoptosis, and necroptosis. Over the course of evolution these pathways have become intricate and complex, coevolving with microbes that infect animal hosts. Microbes, in turn, have evolved strategies to interfere with the pathways of regulated cell death to avoid eradication by the host. Here, we present an overview of the mechanisms of regulated cell death in Animalia and the strategies devised by pathogens to interfere with these processes. We review the molecular pathways of regulated cell death, their roles in infection, and how they are perturbed by viruses and bacteria, providing insights into the coevolution of host-pathogen interactions and cell death pathways.

Modulation of Ubiquitin Signaling in Innate Immune Response by Herpesviruses

The ubiquitin proteasome system (UPS) is a protein degradation machinery that is crucial for cellular homeostasis in eukaryotes. Therefore, it is not surprising that the UPS coordinates almost all host cellular processes, including host-pathogen interactions. This protein degradation machinery acts predominantly by tagging substrate proteins designated for degradation with a ubiquitin molecule. These ubiquitin tags have been involved at various steps of the innate immune response. Hence, herpesviruses have evolved ways to antagonize the host defense mechanisms by targeting UPS components such as ubiquitin E3 ligases and deubiquitinases (DUBs) that establish a productive infection. This review delineates how herpesviruses usurp the critical roles of ubiquitin E3 ligases and DUBs in innate immune response to escape host-antiviral immune response, with particular focus on retinoic acid-inducible gene I (RIG-I)-like receptors (RLR), cyclic-GMP-AMP (cGAMP) synthase (cGAS), stimulator of interferon (IFN) genes (STING) pathways, and inflammasome signaling.

Disrupting Neurons and Glial Cells Oneness in the Brain-The Possible Causal Role of Herpes Simplex Virus Type 1 (HSV-1) in Alzheimer's Disease

Current data strongly suggest herpes simplex virus type 1 (HSV-1) infection in the brain as a contributing factor to Alzheimer's disease (AD). The consequences of HSV-1 brain infection are multilateral, not only are neurons and glial cells damaged, but modifications also occur in their environment, preventing the transmission of signals and fulfillment of homeostatic and immune functions, which can greatly contribute to the development of disease. In this review, we discuss the pathological alterations in the central nervous system (CNS) cells that occur, following HSV-1 infection. We describe the changes in neurons, astrocytes, microglia, and oligodendrocytes related to the production of inflammatory factors, transition of glial cells into a reactive state, oxidative damage, Aβ secretion, tau hyperphosphorylation, apoptosis, and autophagy. Further, HSV-1 infection can affect processes observed during brain aging, and advanced age favors HSV-1 reactivation as well as the entry of the virus into the brain. The host activates pattern recognition receptors (PRRs) for an effective antiviral response during HSV-1 brain infection, which primarily engages type I interferons (IFNs). Future studies regarding the influence of innate immune deficits on AD development, as well as supporting the neuroprotective properties of glial cells, would reveal valuable information on how to harness cytotoxic inflammatory milieu to counter AD initiation and progression.

Targeting Inflammasome Activation in COVID-19: Delivery of RNA Interference-Based Therapeutic Molecules

Mortality and morbidity associated with COVID-19 continue to be significantly high worldwide, owing to the absence of effective treatment strategies. The emergence of different variants of SARS-CoV-2 is also a considerable source of concern and has led to challenges in the development of better prevention and treatment strategies, including vaccines. Immune dysregulation due to pro-inflammatory mediators has worsened the situation in COVID-19 patients. Inflammasomes play a critical role in modulating pro-inflammatory cytokines in the pathogenesis of COVID-19 and their activation is associated with poor clinical outcomes. Numerous preclinical and clinical trials for COVID-19 treatment using different approaches are currently underway. Targeting different inflammasomes to reduce the cytokine storm, and its associated complications, in COVID-19 patients is a new area of research. Non-coding RNAs, targeting inflammasome activation, may serve as an effective treatment strategy. However, the efficacy of these therapeutic agents is highly dependent on the delivery system. MicroRNAs and long non-coding RNAs, in conjunction with an efficient delivery vehicle, present a potential strategy for regulating NLRP3 activity through various RNA interference (RNAi) mechanisms. In this regard, the use of nanomaterials and other vehicle types for the delivery of RNAi-based therapeutic molecules for COVID-19 may serve as a novel approach for enhancing drug efficacy. The present review briefly summarizes immune dysregulation and its consequences, the roles of different non-coding RNAs in regulating the NLRP3 inflammasome, distinct types of vectors for their delivery, and potential therapeutic targets of microRNA for treatment of COVID-19.

Pathogenesis and virulence of herpes simplex virus

Two of the most prevalent human viruses worldwide, herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2, respectively), cause a variety of diseases, including cold sores, genital herpes, herpes stromal keratitis, meningitis and encephalitis. The intrinsic, innate and adaptive immune responses are key to control HSV, and the virus has developed mechanisms to evade them. The immune response can also contribute to pathogenesis, as observed in stromal keratitis and encephalitis. The fact that certain individuals are more prone than others to suffer severe disease upon HSV infection can be partially explained by the existence of genetic polymorphisms in humans. Like all herpesviruses, HSV has two replication cycles: lytic and latent. During lytic replication HSV produces infectious viral particles to infect other cells and organisms, while during latency there is limited gene expression and lack of infectious virus particles. HSV establishes latency in neurons and can cause disease both during primary infection and upon reactivation. The mechanisms leading to latency and reactivation and which are the viral and host factors controlling these processes are not completely understood. Here we review the HSV life cycle, the interaction of HSV with the immune system and three of the best-studied pathologies: Herpes stromal keratitis, herpes simplex encephalitis and genital herpes. We also discuss the potential association between HSV-1 infection and Alzheimer's disease.

cGAS-STING-mediated sensing pathways in DNA and RNA virus infections: crosstalk with other sensing pathways

Viruses cause a variety of diseases in humans and other organisms. The most important defense mechanism against viral infections is initiated when the viral genome is sensed by host proteins, and this results in interferon production and pro-inflammatory cytokine responses. The sensing of the viral genome or its replication intermediates within host cells is mediated by cytosolic proteins. For example, cGAS and IFI16 recognize non-self DNA, and RIG-I and MDA5 recognize non-self RNA. Once these sensors are activated, they trigger a cascade of reactions activating downstream molecules, which eventually results in the transcriptional activation of type I and III interferons, which play a critical role in suppressing viral propagation, either by directly limiting their replication or by inducing host cells to inhibit viral protein synthesis. The immune response against viruses relies solely upon sensing of viral genomes and their downstream signaling molecules. Although DNA and RNA viruses are sensed by distinct classes of receptor proteins, there is a possibility of overlap between the viral DNA and viral RNA sensing mechanisms. In this review, we focus on various host sensing molecules and discuss the associated signaling pathways that are activated in response to different viral infections. We further highlight the possibility of crosstalk between the cGAS-STING and the RIG-I-MAVS pathways to limit viral infections. This comprehensive review delineates the mechanisms by which different viruses evade host cellular responses to sustain within the host cells.

Procaspase-1 patrolled to the nucleus of proatherogenic lipid LPC-activated human aortic endothelial cells induces ROS promoter CYP1B1 and strong inflammation

To determine the roles of nuclear localization of pro-caspase-1 in human aortic endothelial cells (HAECs) activated by proatherogenic lipid lysophosphatidylcholine (LPC), we examined cytosolic and nuclear localization of pro-caspase-1, identified nuclear export signal (NES) in pro-caspase-1 and sequenced RNAs. We made the following findings: 1) LPC increases nuclear localization of procaspase-1 in HAECs. 2) Nuclear pro-caspase-1 exports back to the cytosol, which is facilitated by a leptomycin B-inhibited mechanism. 3) Increased nuclear localization of pro-caspase-1 by a new NES peptide inhibitor upregulates inflammatory genes in oxidative stress and Th17 pathways; and SUMO activator N106 enhances nuclear localization of pro-caspase-1 and caspase-1 activation (p20) in the nucleus. 4) LPC plus caspase-1 enzymatic inhibitor upregulates inflammatory genes with hypercytokinemia/hyperchemokinemia and interferon pathways, suggesting a novel capsase-1 enzyme-independent inflammatory mechanism. 5) LPC in combination with NES inhibitor and caspase-1 inhibitor upregulate inflammatory gene expression that regulate Th17 activation, endotheli-1 signaling, p38-, and ERK- MAPK pathways. To examine two hallmarks of endothelial activation such as secretomes and membrane protein signaling, LPC plus NES inhibitor upregulate 57 canonical secretomic genes and 76 exosome secretomic genes, respectively, promoting four pathways including Th17, IL-17 promoted cytokines, interferon signaling and cholesterol biosynthesis. LPC with NES inhibitor also promote inflammation via upregulating ROS promoter CYP1B1 and 11 clusters of differentiation (CD) membrane protein pathways. Mechanistically, all the LPC plus NES inhibitor-induced genes are significantly downregulated in CYP1B1-deficient microarray, suggesting that nuclear caspase-1-induced CYP1B1 promotes strong inflammation. These transcriptomic results provide novel insights on the roles of nuclear caspase-1 in sensing DAMPs, inducing ROS promoter CYP1B1 and in regulating a large number of genes that mediate HAEC activation and inflammation. These findings will lead to future development of novel therapeutics for cardiovascular diseases (CVD), inflammations, infections, transplantation, autoimmune disease and cancers. (total words: 284).

The Crucial Role of NLRP3 Inflammasome in Viral Infection-Associated Fibrosing Interstitial Lung Diseases

Idiopathic pulmonary fibrosis (IPF), one of the most common fibrosing interstitial lung diseases (ILD), is a chronic-age-related respiratory disease that rises from repeated micro-injury of the alveolar epithelium. Environmental influences, intrinsic factors, genetic and epigenetic risk factors that lead to chronic inflammation might be implicated in the development of IPF. The exact triggers that initiate the fibrotic response in IPF remain enigmatic, but there is now increasing evidence supporting the role of chronic exposure of viral infection. During viral infection, activation of the NLRP3 inflammasome by integrating multiple cellular and molecular signaling implicates robust inflammation, fibroblast proliferation, activation of myofibroblast, matrix deposition, and aberrant epithelial-mesenchymal function. Overall, the crosstalk of the NLRP3 inflammasome and viruses can activate immune responses and inflammasome-associated molecules in the development, progression, and exacerbation of IPF.

Local Immune Control of Latent Herpes Simplex Virus Type 1 in Ganglia of Mice and Man

Herpes simplex virus type 1 (HSV-1) is a prevalent human pathogen. HSV-1 genomes persist in trigeminal ganglia neuronal nuclei as chromatinized episomes, while epithelial cells are typically killed by lytic infection. Fluctuations in anti-viral responses, broadly defined, may underlay periodic reactivations. The ganglionic immune response to HSV-1 infection includes cell-intrinsic responses in neurons, innate sensing by several cell types, and the infiltration and persistence of antigen-specific T-cells. The mechanisms specifying the contrasting fates of HSV-1 in neurons and epithelial cells may include differential genome silencing and chromatinization, dictated by variation in access of immune modulating viral tegument proteins to the cell body, and protection of neurons by autophagy. Innate responses have the capacity of recruiting additional immune cells and paracrine activity on parenchymal cells, for example via chemokines and type I interferons. In both mice and humans, HSV-1-specific CD8 and CD4 T-cells are recruited to ganglia, with mechanistic studies suggesting active roles in immune surveillance and control of reactivation. In this review we focus mainly on HSV-1 and the TG, comparing and contrasting where possible observational, interventional, and in vitro studies between humans and animal hosts.

Rational Design of Live-Attenuated Vaccines against Herpes Simplex Viruses

Diseases caused by human herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) affect millions of people worldwide and range from fatal encephalitis in neonates and herpes keratitis to orofacial and genital herpes, among other manifestations. The viruses can be shed efficiently by asymptomatic carriers, causing increased rates of infection. Viral transmission occurs through direct contact of mucosal surfaces followed by initial replication of the incoming virus in skin tissues. Subsequently, the viruses infect sensory neurons in the trigeminal and lumbosacral dorsal root ganglia, where they are primarily maintained in a transcriptionally repressed state termed "latency", which persists for the lifetime of the host. HSV DNA has also been detected in other sympathetic ganglia. Periodically, latent viruses can reactivate, causing ulcerative and often painful lesions primarily at the site of primary infection and proximal sites. In the United States, recurrent genital herpes alone accounts for more than a billion dollars in direct medical costs per year, while there are much higher costs associated with the socio-economic aspects of diseased patients, such as loss of productivity due to mental anguish. Currently, there are no effective FDA-approved vaccines for either prophylactic or therapeutic treatment of human herpes simplex infections, while several recent clinical trials have failed to achieve their endpoint goals. Historically, live-attenuated vaccines have successfully combated viral diseases, including polio, influenza, measles, and smallpox. Vaccines aimed to protect against the devastation of smallpox led to the most significant achievement in medical history: the eradication of human disease by vaccination. Recently, novel approaches toward developing safe and effective live-attenuated vaccines have demonstrated high efficacy in various preclinical models of herpetic disease. This next generation of live-attenuated vaccines has been tailored to minimize vaccine-associated side effects and promote effective and long-lasting immune responses. The ultimate goal is to prevent or reduce primary infections (prophylactic vaccines) or reduce the frequency and severity of disease associated with reactivation events (therapeutic vaccines). These vaccines' "rational" design is based on our current understanding of the immunopathogenesis of herpesviral infections that guide the development of vaccines that generate robust and protective immune responses. This review covers recent advances in the development of herpes simplex vaccines and the current state of ongoing clinical trials in pursuit of an effective vaccine against herpes simplex virus infections and associated diseases.

Encephalitis Due to Co-Infection with Cytomegalovirus and Herpes Simplex Virus Type 2 in a Patient with Acquired Immunodeficiency Syndrome

BACKGROUND Opportunistic infections are commonly seen in immunocompromised patients. Here, we present an interesting case of a patient with poorly controlled human immunodeficiency virus (HIV) infection who presented with multiple opportunistic infections. CASE REPORT A 44-year-old woman with medical history of HIV infection (CD4 <20 cells/µl, viral load 172 996 copies/ml), presented with symptoms of headache for 2 days and changes in mentation. She was recently treated for pulmonary mycobacterium avium complex infection. Her physical examination revealed normal breath sounds and her abdominal examination was unremarkable. She did not have any focal neurological deficits, nuchal rigidity, or papilledema on examination. Computed tomography (CT) head was negative for any acute lesions. She was empirically started on vancomycin and piperacillin-tazobactam. Due to persistent symptoms, a lumbar puncture was performed, which revealed elevated total proteins in CSF, and a viral polymerase chain reaction test was positive for herpes simplex virus type 2 (HSV-2) and cytomegalovirus (CMV). Magnetic resonance imaging of the brain showed mild enhancement of the ventricular lining. She was treated with acyclovir, which was later changed to ganciclovir, with resulting clinical improvement. The patient had clinical improvement and was discharged home. CONCLUSIONS Multiple opportunistic co-infections should be considered in patients with poorly controlled HIV infection.

Endothelial Immunity Trained by Coronavirus Infections, DAMP Stimulations and Regulated by Anti-Oxidant NRF2 May Contribute to Inflammations, Myelopoiesis, COVID-19 Cytokine Storms and Thromboembolism

To characterize transcriptomic changes in endothelial cells (ECs) infected by coronaviruses, and stimulated by DAMPs, the expressions of 1311 innate immune regulatomic genes (IGs) were examined in 28 EC microarray datasets with 7 monocyte datasets as controls. We made the following findings: The majority of IGs are upregulated in the first 12 hours post-infection (PI), and maintained until 48 hours PI in human microvascular EC infected by middle east respiratory syndrome-coronavirus (MERS-CoV) (an EC model for COVID-19). The expressions of IGs are modulated in 21 human EC transcriptomic datasets by various PAMPs/DAMPs, including LPS, LPC, shear stress, hyperlipidemia and oxLDL. Upregulation of many IGs such as nucleic acid sensors are shared between ECs infected by MERS-CoV and those stimulated by PAMPs and DAMPs. Human heart EC and mouse aortic EC express all four types of coronavirus receptors such as ANPEP, CEACAM1, ACE2, DPP4 and virus entry facilitator TMPRSS2 (heart EC); most of coronavirus replication-transcription protein complexes are expressed in HMEC, which contribute to viremia, thromboembolism, and cardiovascular comorbidities of COVID-19. ECs have novel trained immunity (TI), in which subsequent inflammation is enhanced. Upregulated proinflammatory cytokines such as TNFα, IL6, CSF1 and CSF3 and TI marker IL-32 as well as TI metabolic enzymes and epigenetic enzymes indicate TI function in HMEC infected by MERS-CoV, which may drive cytokine storms. Upregulated CSF1 and CSF3 demonstrate a novel function of ECs in promoting myelopoiesis. Mechanistically, the ER stress and ROS, together with decreased mitochondrial OXPHOS complexes, facilitate a proinflammatory response and TI. Additionally, an increase of the regulators of mitotic catastrophe cell death, apoptosis, ferroptosis, inflammasomes-driven pyroptosis in ECs infected with MERS-CoV and the upregulation of pro-thrombogenic factors increase thromboembolism potential. Finally, NRF2-suppressed ROS regulate innate immune responses, TI, thrombosis, EC inflammation and death. These transcriptomic results provide novel insights on the roles of ECs in coronavirus infections such as COVID-19, cardiovascular diseases (CVD), inflammation, transplantation, autoimmune disease and cancers.

Host immune response in chronic hepatitis C infection: involvement of cytokines and inflammasomes

Chronic liver disease is a major health issue worldwide and chronic hepatitis C (CHC) is associated with an increased risk of cirrhosis and hepatocellular carcinoma (HCC). There is evidence that the hepatitis C virus (HCV) infection is correlated with immune senescence by way of immune activation and chronic inflammation, which lead to increased metabolic and cardiovascular risk, as well as progressive liver damage. Both the innate and adaptive immunity are firmly tied to the prognosis of an infection with HCV and its response to antiviral therapy. HCV is therefore associated with increased pro-inflammatory status, heightened production of cytokines, prolonged systemic inflammation, as well as increased morbidity and mortality, mainly due to the progression of hepatic fibrosis and HCC, but also secondary to cardiovascular diseases. Viral hepatic pathology is increasingly considered a disease that is no longer merely limited to the liver, but one with multiple metabolic consequences. Numerous in vitro studies, using experimental models of acute or chronic inflammation of the liver, has brought new information on immunopathological mechanisms resulting from viral infections and have highlighted the importance of involving complex structures, inflammasomes complex, in these mechanisms, in addition to the involvement of numerous proinflammatory cytokines. Beyond obtaining a sustained viral response and halting the aforementioned hepatic fibrosis, the current therapeutic “treat-to-target” strategies are presently focused on immune-mediated and metabolic disorders, to improve the quality of life and long-term prognosis of CHC patients.

Merkel Cell Polyomavirus Infection Induces an Antiviral Innate Immune Response in Human Dermal Fibroblasts

Merkel cell polyomavirus (MCPyV) infects most of the human population asymptomatically, but in rare cases it leads to a highly aggressive skin cancer called Merkel cell carcinoma (MCC). MCC incidence is much higher in aging and immunocompromised populations. The epidemiology of MCC suggests that dysbiosis between the host immune response and the MCPyV infectious cycle could contribute to the development of MCPyV-associated MCC. Insufficient restriction of MCPyV by normal cellular processes, for example, could promote the incidental oncogenic MCPyV integration events and/or entry into the original cell of MCC. Progress toward understanding MCPyV biology has been hindered by its narrow cellular tropism. Our discovery that primary human dermal fibroblasts (HDFs) support MCPyV infection has made it possible to closely model cellular responses to different stages of the infectious cycle. The present study reveals that the onset of MCPyV replication and early gene expression induces an inflammatory cytokine and interferon-stimulated gene (ISG) response. The cGAS-STING pathway, in coordination with NF-κB, mediates induction of this innate immune gene expression program. Further, silencing of cGAS or NF-κB pathway factors led to elevated MCPyV replication. We also discovered that the PYHIN protein IFI16 localizes to MCPyV replication centers but does not contribute to the induction of ISGs. Instead, IFI16 upregulates inflammatory cytokines in response to MCPyV infection by an alternative mechanism. The work described herein establishes a foundation for exploring how changes to the skin microenvironment induced by aging or immunodeficiency might alter the fate of MCPyV and its host cell to encourage carcinogenesis. IMPORTANCE MCC has a high rate of mortality and an increasing incidence. Immune-checkpoint therapies have improved the prognosis of patients with metastatic MCC. Still, a significant proportion of the patients fail to respond to immune-checkpoint therapies or have a medical need for iatrogenic immune-suppression. A greater understanding of MCPyV biology could inform targeted therapies for MCPyV-associated MCC. Moreover, cellular events preceding MCC oncogenesis remain largely unknown. The present study aims to explore how MCPyV interfaces with innate immunity during its infectious cycle. We describe how MCPyV replication and/or transcription elicit an innate immune response via cGAS-STING, NF-κB, and IFI16. We also explore the effects of this response on MCPyV replication. Our findings illustrate how healthy cellular conditions may allow low-level infection that evades immune destruction until highly active replication is restricted by host responses. Conversely, pathological conditions could result in unbridled MCPyV replication that licenses MCC tumorigenesis.

Evasion of Intracellular DNA Sensing by Human Herpesviruses

Sensing of viral constituents is the first and critical step in the host innate immune defense against viruses. In mammalian cells, there are a variety of pathogen recognition receptors (PRRs) that detect diverse pathogen-associated molecular patterns (PAMPs) including viral RNA and DNA. In the past decade, a number of host DNA sensors have been discovered and the underlying sensing mechanisms have been elucidated. Herpesviruses belong to a large family of enveloped DNA viruses. They are successful pathogens whose elaborate immune evasion mechanisms contribute to high prevalence of infection among their hosts. The three subfamilies of herpesviruses have all been found to employ diverse and overlapping strategies to interfere with host DNA sensing. These strategies include masking viral DNA or the DNA sensor, degradation of the DNA sensor, and post-transcriptional modification of the DNA sensor or its adaptor protein. In this review, we will discuss the current state of our knowledge on how human herpesviruses use these strategies to evade DNA-induced immune responses. Comprehensive understanding of herpesvirus immune-evasion mechanisms will aid in the development of vaccines and antivirals for herpesvirus-associated diseases.

Host Innate Immune Response and Viral Immune Evasion During Alphaherpesvirus Infection

Both the development of the mammalian innate immune system and the antagonistic strategies acquired by alphaherpesviruses to dismantle it have been shaped by co-evolving virus-host interactions over millions of years. Here, we review mechanisms employed by mammalian cells to detect pathogen molecules, such as viral glycoproteins and nucleic acids, and induce innate immune signaling upon infection with alphaherpesviruses. We further explore strategies acquired by these viruses to bypass immune detection and activation, thereby supporting virus replication and spread. Finally, we discuss the contributions of advanced 'omics' and microscopy methods to these discoveries in immune signaling and highlight emerging technologies that can help to further our understanding of the dynamic interplay between host innate immune responses and virus immune evasion.