Infection and Functional Modulation of Human Monocytes and Macrophages by Varicella-Zoster Virus

Varicella Zoster Virus Downregulates Expression of the Nonclassical Antigen Presentation Molecule CD1d

BACKGROUND

The nonclassical antigen presentation molecule CD1d presents lipid antigens to invariant natural killer T (iNKT) cells. Activation of these cells triggers a rapid cytokine response providing an interface between innate and adaptive immune responses. The importance of CD1d and iNKT cells in varicella zoster virus (VZV) infection has been emphasized by clinical reports of individuals with CD1d or iNKT cell deficiencies experiencing severe, disseminated varicella postvaccination.

METHODS

Three strains of VZV (VZV-S, rOka, and VZV rOka-66S) were used to infect Jurkat cells. Flow cytometry of VZV- and mock-infected cells assessed the modulatory impact of VZV on CD1d protein. Infected cell supernatant and transwell co-culture experiments explored the role of soluble factors in VZV-mediated immunomodulation. CD1d transcripts were assessed by reverse-transcription polymerase chain reaction.

RESULTS

Surface and intracellular flow cytometry demonstrated that CD1d was strikingly downregulated by VZV-S and rOka in both infected and VZV antigen-negative cells compared to mock. CD1d downregulation is cell-contact dependent and CD1d transcripts are targeted by VZV. Mechanistic investigations using rOka-66S (unable to express the viral kinase ORF66) implicate this protein in CD1d modulation in infected cells.

CONCLUSIONS

VZV implements multiple mechanisms targeting both CD1d transcript and protein. This provides evidence of VZV interaction with and manipulation of the CD1d-iNKT cell axis.

Varicella Zoster Virus disrupts MAIT cell polyfunctional effector responses

Mucosal-associated invariant T (MAIT) cells are unconventional T cells that respond to riboflavin biosynthesis and cytokines through TCR-dependent and -independent pathways, respectively. MAIT cell activation plays an immunoprotective role against several pathogens, however the functional capacity of MAIT cells following direct infection or exposure to infectious agents remains poorly defined. We investigated the impact of Varicella Zoster Virus (VZV) on blood-derived MAIT cells and report virus-mediated impairment of activation, cytokine production, and altered transcription factor expression by VZV infected (antigen+) and VZV exposed (antigen-) MAIT cells in response to TCR-dependent and -independent stimulation. Furthermore, we reveal that suppression of VZV exposed (antigen-) MAIT cells is not mediated by a soluble factor from neighbouring VZV infected (antigen+) MAIT cells. Finally, we demonstrate that VZV impairs the cytolytic potential of MAIT cells in response to riboflavin synthesising bacteria. In summary, we report a virus-mediated immune-evasion strategy that disarms MAIT cell responses.

Viral modulation of type II interferon increases T cell adhesion and virus spread

During primary varicella zoster virus (VZV) infection, infected lymphocytes drive primary viremia, causing systemic dissemination throughout the host, including the skin. This results in cytokine expression, including interferons (IFNs), which partly limit infection. VZV also spreads from skin keratinocytes to lymphocytes prior to secondary viremia. It is not clear how VZV achieves this while evading the cytokine response. Here, we show that VZV glycoprotein C (gC) binds IFN-γ and modifies its activity, increasing the expression of a subset of IFN-stimulated genes (ISGs), including intercellular adhesion molecule 1 (ICAM1), chemokines and immunomodulatory genes. The higher ICAM1 protein level at the plasma membrane of keratinocytes facilitates lymphocyte function-associated antigen 1-dependent T cell adhesion and expression of gC during infection increases VZV spread to peripheral blood mononuclear cells. This constitutes the discovery of a strategy to modulate IFN-γ activity, upregulating a subset of ISGs, promoting enhanced lymphocyte adhesion and virus spread.

Varicella zoster virus-induced autophagy in human neuronal and hematopoietic cells exerts antiviral activity

Autophagy is a degradational pathway with pivotal roles in cellular homeostasis and survival, including protection of neurons in the central nervous system (CNS). The significance of autophagy as antiviral defense mechanism is recognized and some viruses hijack and modulate this process to their advantage in certain cell types. Here, we present data demonstrating that the human neurotropic herpesvirus varicella zoster virus (VZV) induces autophagy in human SH-SY5Y neuronal cells, in which the pathway exerts antiviral activity. Productively VZV-infected SH-SY5Y cells showed increased LC3-I-LC3-II conversion as well as co-localization of the viral glycoprotein E and the autophagy receptor p62. The activation of autophagy was dependent on a functional viral genome. Interestingly, inducers of autophagy reduced viral transcription, whereas inhibition of autophagy increased viral transcript expression. Finally, the genotype of patients with severe ocular and brain VZV infection were analyzed to identify potential autophagy-associated inborn errors of immunity. Two patients expressing genetic variants in the autophagy genes ULK1 and MAP1LC3B2, respectively, were identified. Notably, cells of both patients showed reduced autophagy, alongside enhanced viral replication and death of VZV-infected cells. In conclusion, these results demonstrate a neuro-protective role for autophagy in the context of VZV infection and suggest that failure to mount an autophagy response is a potential predisposing factor for development of severe VZV disease.

Creating the "Dew Drop on a Rose Petal": the Molecular Pathogenesis of Varicella-Zoster Virus Skin Lesions

Varicella-zoster virus (VZV) is a human alphaherpesvirus that causes varicella (chicken pox) as the primary infection in a susceptible host. Varicella is very contagious through its transmission by direct contact with vesicular skin lesions that contain high titers of infectious virus and respiratory droplets. While the clinical manifestations of primary VZV infection are well recognized, defining the molecular mechanisms that drive VZV pathogenesis in the naive host before adaptive antiviral immunity is induced has been a challenge due to species specificity. This review focuses on advances made in identifying the differentiated human host cells targeted by VZV to cause varicella, the processes involved in viral takeover of these heterogenous cell types, and the host cell countermeasures that typically culminate in a benign illness. This work has revealed many unexpected and multifaceted mechanisms used by VZV to achieve its high prevalence and persistence in the human population.

Lack of strong innate immune reactivity renders macrophages alone unable to control productive Varicella-Zoster Virus infection in an isogenic human iPSC-derived neuronal co-culture model

With Varicella-Zoster Virus (VZV) being an exclusive human pathogen, human induced pluripotent stem cell (hiPSC)-derived neural cell culture models are an emerging tool to investigate VZV neuro-immune interactions. Using a compartmentalized hiPSC-derived neuronal model allowing axonal VZV infection, we previously demonstrated that paracrine interferon (IFN)-α2 signalling is required to activate a broad spectrum of interferon-stimulated genes able to counteract a productive VZV infection in hiPSC-neurons. In this new study, we now investigated whether innate immune signalling by VZV-challenged macrophages was able to orchestrate an antiviral immune response in VZV-infected hiPSC-neurons. In order to establish an isogenic hiPSC-neuron/hiPSC-macrophage co-culture model, hiPSC-macrophages were generated and characterised for phenotype, gene expression, cytokine production and phagocytic capacity. Even though immunological competence of hiPSC-macrophages was shown following stimulation with the poly(dA:dT) or treatment with IFN-α2, hiPSC-macrophages in co-culture with VZV-infected hiPSC-neurons were unable to mount an antiviral immune response capable of suppressing a productive neuronal VZV infection. Subsequently, a comprehensive RNA-Seq analysis confirmed the lack of strong immune responsiveness by hiPSC-neurons and hiPSC-macrophages upon, respectively, VZV infection or challenge. This may suggest the need of other cell types, like T-cells or other innate immune cells, to (co-)orchestrate an efficient antiviral immune response against VZV-infected neurons.

Differential immunophenotype of circulating monocytes from pregnant women in response to viral ligands

BACKGROUND

Viral infections during pregnancy can have deleterious effects on mothers and their offspring. Monocytes participate in the maternal host defense against invading viruses; however, whether pregnancy alters monocyte responses is still under investigation. Herein, we undertook a comprehensive in vitro study of peripheral monocytes to characterize the differences in phenotype and interferon release driven by viral ligands between pregnant and non-pregnant women.

METHODS

Peripheral blood was collected from third-trimester pregnant (n = 20) or non-pregnant (n = 20, controls) women. Peripheral blood mononuclear cells were isolated and exposed to R848 (TLR7/TLR8 agonist), Gardiquimod (TLR7 agonist), Poly(I:C) (HMW) VacciGrade™ (TLR3 agonist), Poly(I:C) (HMW) LyoVec™ (RIG-I/MDA-5 agonist), or ODN2216 (TLR9 agonist) for 24 h. Cells and supernatants were collected for monocyte phenotyping and immunoassays to detect specific interferons, respectively.

RESULTS

The proportions of classical (CD14^hiCD16^-), intermediate (CD14^hiCD16⁺), non-classical (CD14^loCD16⁺), and CD14^loCD16^- monocytes were differentially affected between pregnant and non-pregnant women in response to TLR3 stimulation. The proportions of pregnancy-derived monocytes expressing adhesion molecules (Basigin and PSGL-1) or the chemokine receptors CCR5 and CCR2 were diminished in response to TLR7/TLR8 stimulation, while the proportions of CCR5^- monocytes were increased. Such differences were found to be primarily driven by TLR8 signaling, rather than TLR7. Moreover, the proportions of monocytes expressing the chemokine receptor CXCR1 were increased during pregnancy in response to poly(I:C) stimulation through TLR3, but not RIG-I/MDA-5. By contrast, pregnancy-specific changes in the monocyte response to TLR9 stimulation were not observed. Notably, the soluble interferon response to viral stimulation by mononuclear cells was not diminished in pregnancy.

CONCLUSIONS

Our data provide insight into the differential responsiveness of pregnancy-derived monocytes to ssRNA and dsRNA, mainly driven by TLR8 and membrane-bound TLR3, which may help to explain the increased susceptibility of pregnant women to adverse outcomes resulting from viral infection as observed during recent and historic pandemics.

Varicella Zoster Virus infects mucosal associated Invariant T cells

Introduction

Mucosal Associated Invariant T (MAIT) cells are innate-like T cells that respond to conserved pathogen-derived vitamin B metabolites presented by the MHC class I related-1 molecule (MR1) antigen presentation pathway. Whilst viruses do not synthesize these metabolites, we have reported that varicella zoster virus (VZV) profoundly suppresses MR1 expression, implicating this virus in manipulation of the MR1:MAIT cell axis. During primary infection, the lymphotropism of VZV is likely to be instrumental in hematogenous dissemination of virus to gain access to cutaneous sites where it clinically manifests as varicella (chickenpox). However, MAIT cells, which are found in the blood and at mucosal and other organ sites, have yet to be examined in the context of VZV infection. The goal of this study was to examine any direct impact of VZV on MAIT cells.

Methods

Using flow cytometry, we interrogated whether primary blood derived MAIT cells are permissive to infection by VZV whilst further analysing differential levels of infection between various MAIT cell subpopulations. Changes in cell surface extravasation, skin homing, activation and proliferation markers after VZV infection of MAIT cells was also assessed via flow cytometry. Finally the capacity of MAIT cells to transfer infectious virus was tested through an infectious center assay and imaged via fluorescence microscopy.

Results

We identify primary blood-derived MAIT cells as being permissive to VZV infection. A consequence of VZV infection of MAIT cells was their capacity to transfer infectious virus to other permissive cells, consistent with MAIT cells supporting productive infection. When subgrouping MAIT cells by their co- expression of a variety cell surface markers, there was a higher proportion of VZV infected MAIT cells co-expressing CD4+ and CD4+/CD8+ MAIT cells compared to the more phenotypically dominant CD8+ MAIT cells, whereas infection was not associated with differences in co-expression of CD56 (MAIT cell subset with enhanced responsiveness to innate cytokine stimulation), CD27 (co-stimulatory) or PD-1 (immune checkpoint). Infected MAIT cells retained high expression of CCR2, CCR5, CCR6, CLA and CCR4, indicating a potentially intact capacity for transendothelial migration, extravasation and trafficking to skin sites. Infected MAIT cells also displayed increased expression of CD69 (early activation) and CD71 (proliferation) markers.

Discussion

These data identify MAIT cells as being permissive to VZV infection and identify impacts of such infection on co- expressed functional markers.

Herpes Zoster and association with pulp necrosis and development of apical periodontitis - a review and presentation of two case reports

The varicella zoster virus as an aetiological agent for endodontic disease is not a well-recognised entity despite several published case reports. While advances in DNA molecular analysis techniques (PCR) have contributed to the current understanding of the potential role of the varicella zoster virus in the initiation and progression of endodontic disease, a review indicates a need for ongoing research. Case reports are presented of two female patients with a history of herpes zoster who developed pulp necrosis, with one patient progressing to apical periodontitis. Both patients received non-surgical endodontic therapy, followed by intra-coronal bleaching in one of the patients due to tooth discolouration which developed during the prodromal and acute phases of the herpes zoster infection. Clinical and radiographic examinations at 23 and 22 years, respectively, showed the affected teeth to be retained in an asymptomatic and aesthetically satisfactory state with no radiographic evidence of apical pathosis.

Quantitative proteomics of small numbers of closely-related cells: Selection of the optimal method for a clinical setting

Mass spectrometry (MS)-based proteomics profiling has undoubtedly increased the knowledge about cellular processes and functions. However, its applicability for paucicellular sample analyses is currently limited. Although new approaches have been developed for single-cell studies, most of them have not (yet) been standardized and/or require highly specific (often home-built) devices, thereby limiting their broad implementation, particularly in non-specialized settings. To select an optimal MS-oriented proteomics approach applicable in translational research and clinical settings, we assessed 10 different sample preparation procedures in paucicellular samples of closely-related cell types. Particularly, five cell lysis protocols using different chemistries and mechanical forces were combined with two sample clean-up techniques (C18 filter- and SP3-based), followed by tandem mass tag (TMT)-based protein quantification. The evaluation was structured in three phases: first, cell lines from hematopoietic (THP-1) and non-hematopoietic (HT-29) origins were used to test the approaches showing the combination of a urea-based lysis buffer with the SP3 bead-based clean-up system as the best performer. Parameters such as reproducibility, accessibility, spatial distribution, ease of use, processing time and cost were considered. In the second phase, the performance of the method was tested on maturation-related cell populations: three different monocyte subsets from peripheral blood and, for the first time, macrophages/microglia (MAC) from glioblastoma samples, together with T cells from both tissues. The analysis of 50,000 cells down to only 2,500 cells revealed different protein expression profiles associated with the distinct cell populations. Accordingly, a closer relationship was observed between non-classical monocytes and MAC, with the latter showing the co-expression of M1 and M2 macrophage markers, although pro-tumoral and anti-inflammatory proteins were more represented. In the third phase, the results were validated by high-end spectral flow cytometry on paired monocyte/MAC samples to further determine the sensitivity of the MS approach selected. Finally, the feasibility of the method was proven in 194 additional samples corresponding to 38 different cell types, including cells from different tissue origins, cellular lineages, maturation stages and stimuli. In summary, we selected a reproducible, easy-to-implement sample preparation method for MS-based proteomic characterization of paucicellular samples, also applicable in the setting of functionally closely-related cell populations.

Th1 regulatory events by infectious pathogens, herpes zoster and herpes simplex viruses: prospects for therapeutic options for atopic eczema

Infections caused by viral and bacterial pathogens are typically perceived as harmful, such as in cases of herpes zoster and herpes simplex virus infections. However, clinical observation of an improvement in atopic skin lesions upon herpes virus infection has been noted, particularly at the site of varicella and Kaposi’s varicelliform eruption. Th1 immune cells and cytokines, mobilized and induced for protection against infectious pathogens, are expected to improve Th2 dominant atopic symptoms. This study focuses on Th1 immunoregulatory events mediated by infectious pathogens, particularly herpes viruses. Immunoregulatory events induced by herpes viruses may have a potential therapeutic value for treating atopic eczema.

Varicella-Zoster virus ORF9 is an antagonist of the DNA sensor cGAS

Varicella-Zoster virus (VZV) causes chickenpox and shingles. Although the infection is associated with severe morbidity in some individuals, molecular mechanisms that determine innate immune responses remain poorly defined. We found that the cGAS/STING DNA sensing pathway was required for type I interferon (IFN) induction during VZV infection and that recognition of VZV by cGAS restricted its replication. Screening of a VZV ORF expression library identified the essential VZV tegument protein ORF9 as a cGAS antagonist. Ectopically or virally expressed ORF9 bound to endogenous cGAS leading to reduced type I IFN responses to transfected DNA. Confocal microscopy revealed co-localisation of cGAS and ORF9. ORF9 and cGAS also interacted directly in a cell-free system and phase-separated together with DNA. Furthermore, ORF9 inhibited cGAMP production by cGAS. Taken together, these results reveal the importance of the cGAS/STING DNA sensing pathway for VZV recognition and identify a VZV immune antagonist that partially but directly interferes with DNA sensing via cGAS.

Varicella Zoster Virus Impairs Expression of the Nonclassical Major Histocompatibility Complex Class I-Related Gene Protein (MR1)

The antigen presentation molecule MR1 (major histocompatibility complex, class I-related) presents ligands derived from the riboflavin (vitamin B) synthesis pathway, which is not present in mammalian species or viruses, to mucosal-associated invariant T (MAIT) cells. In this study, we demonstrate that varicella zoster virus (VZV) profoundly suppresses MR1 expression. We show that VZV targets the intracellular reservoir of immature MR1 for degradation, while preexisting, ligand-bound cell surface MR1 is protected from such targeting, thereby highlighting an intricate temporal relationship between infection and ligand availability. We also identify VZV open reading frame (ORF) 66 as functioning to suppress MR1 expression when this viral protein is expressed during transient transfection, but this is not apparent during infection with a VZV mutant virus lacking ORF66 expression. This indicates that VZV is likely to encode multiple viral genes that target MR1. Overall, we identify an immunomodulatory function of VZV whereby infection suppresses the MR1 biosynthesis pathway.

The ubiquitous role of spleen tyrosine kinase (Syk) in gut diseases: From mucosal immunity to targeted therapy

Spleen tyrosine kinase (Syk) is a cytoplasmic non-receptor protein tyrosine kinase expressed in a variety of cells and play crucial roles in signal transduction. Syk mediates downstream signaling by recruiting to the dually phosphorylated immunoreceptor tyrosine-based activation motifs (ITAMs) of the transmembrane adaptor molecule or the receptor chain itself. In gut diseases, Syk is observed to be expressed in intestinal epithelial cells, monocytes/macrophages, dendritic cells and mast cells. Activation of Syk in these cells can modulate intestinal mucosal immune response by promoting inflammatory cytokines and chemokines production, thus regulating gut homeostasis. Due to the restriction of specificity and selectivity for the development of Syk inhibitors, only a few such inhibitors are available in gut diseases, including intestinal ischemia/reperfusion damage, infectious disease, inflammatory bowel disease, etc. The promising outcomes of Syk inhibitors from both preclinical and clinical studies have shown to attenuate the progression of gut diseases thereby indicating a great potential in the development of Syk targeted therapy for treatment of gut diseases. This review depicts the characterization of Syk, summarizes the signal pathways of Syk, and discusses its potential targeted therapy for gut diseases.

Viral Respiratory Pathogens and Lung Injury

Several viruses target the human respiratory tract, causing different clinical manifestations spanning from mild upper airway involvement to life-threatening acute respiratory distress syndrome (ARDS). As dramatically evident in the ongoing SARS-CoV-2 pandemic, the clinical picture is not always easily predictable due to the combined effect of direct viral and indirect patient-specific immune-mediated damage. In this review, we discuss the main RNA (orthomyxoviruses, paramyxoviruses, and coronaviruses) and DNA (adenoviruses, herpesviruses, and bocaviruses) viruses with respiratory tropism and their mechanisms of direct and indirect cell damage. We analyze the thin line existing between a protective immune response, capable of limiting viral replication, and an unbalanced, dysregulated immune activation often leading to the most severe complication. Our comprehension of the molecular mechanisms involved is increasing and this should pave the way for the development and clinical use of new tailored immune-based antiviral strategies.

The frequency of interleukin-1β-producing monocytes is significantly associated with varicella-zoster responses of nursing home residents

Previous studies have demonstrated that the status of the T cell compartment and inflammation-related factors are associated with the immunogenicity of the varicella-zoster virus (VZV) vaccine in older adults; however, little is known about the roles of other immune cell subsets known to influence the generation and maintenance of immunological memory. Responses to a live-attenuated VZV vaccine were studied in relation to peripheral blood mononuclear cell (PBMC) composition and function in a sample of 30 nursing home residents (aged 80-99 years). Interferon-gamma enzyme-linked immunospot (ELISPOT) was used to measure VZV responses at baseline and 6 weeks following vaccination, and associations were sought with the frequencies of monocytes and T, B and natural killer (NK) cells and the production and secretion of cytokines following their ex-vivo stimulation with different agents. While only the frequency of interleukin (IL)-6⁺ CD14⁺ monocytes was inversely associated with post-vaccination VZV response, amounts of IL-1β, IL-10, IL-17A and tumour necrosis factor (TNF) secreted by PBMCs and the frequency of IL-1β⁺ CD14⁺ monocytes was positively correlated with pre-vaccination VZV response. Furthermore, both bivariate correlation and causal mediation analyses supported the notion that IL-1β⁺ CD14⁺ monocytes were significant mediators of the associations between IL-1β and TNF secretion by PBMCs and pre-vaccination VZV responses. Our findings implicate a strong cytokine response mediated by inflammatory IL-1β⁺ monocytes in coordinating responses of long-lived VZV-reactive memory T cells, but with an opposing effect of IL-6⁺ CD14⁺ monocytes. Whether monocyte status promotes or inhibits the induction and/or maintenance of these memory T cells later in life has yet to be determined.

Herpes zoster (shingles) complicating the course of COVID19 infection

Different skin presentations and patterns of cutaneous signs were reported in COVID19 patients. Varicella-zoster virus (VZV) infection is responsible for two very common skin conditions. Varicella (chickenpox) is the initial presentation for infection with VZV and is characterized by a diffuse vesicular rash. It is after this initial attack, that VZV remains latent in the dorsal root ganglia before reactivating to present as herpes zoster (HZ) in middle age groups. Cutaneous skin findings remain to be emerging every day as a marker or a complication of COVID 19. We report a case of HZ complication in a 44 years old COVID 19 positive male.

Varicella zoster virus encodes a viral decoy RHIM to inhibit cell death

Herpesviruses are known to encode a number of inhibitors of host cell death, including RIP Homotypic Interaction Motif (RHIM)-containing proteins. Varicella zoster virus (VZV) is a member of the alphaherpesvirus subfamily and is responsible for causing chickenpox and shingles. We have identified a novel viral RHIM in the VZV capsid triplex protein, open reading frame (ORF) 20, that acts as a host cell death inhibitor. Like the human cellular RHIMs in RIPK1 and RIPK3 that stabilise the necrosome in TNF-induced necroptosis, and the viral RHIM in M45 from murine cytomegalovirus that inhibits cell death, the ORF20 RHIM is capable of forming fibrillar functional amyloid complexes. Notably, the ORF20 RHIM forms hybrid amyloid complexes with human ZBP1, a cytoplasmic sensor of viral nucleic acid. Although VZV can inhibit TNF-induced necroptosis, the ORF20 RHIM does not appear to be responsible for this inhibition. In contrast, the ZBP1 pathway is identified as important for VZV infection. Mutation of the ORF20 RHIM renders the virus incapable of efficient spread in ZBP1-expressing HT-29 cells, an effect which can be reversed by the inhibition of caspases. Therefore we conclude that the VZV ORF20 RHIM is important for preventing ZBP1-driven apoptosis during VZV infection, and propose that it mediates this effect by sequestering ZBP1 into decoy amyloid assemblies.

RIP homotypic interaction motifs (RHIMs) are found in host proteins that can signal for programmed cell death and in viral proteins that can prevent it. Complexes stabilized by intermolecular interactions involving RHIMs have a fibrillar amyloid structure. We have identified a novel RHIM within the ORF20 protein expressed by Varicella zoster virus (VZV) that forms amyloid-based complexes with human cellular RHIMs. Whereas other herpesvirus RHIMs inhibit necroptosis, this new VZV RHIM targets the host RHIM-containing protein ZBP1 to inhibit apoptosis during infection. This is the first study to demonstrate the importance of the ZBP1 pathway in VZV infection and to identify the role of a viral RHIM in apoptosis inhibition. It broadens our understanding of host defense pathways and demonstrates how a decoy amyloid strategy is employed by pathogens to circumvent the host response.

Manipulation of the Innate Immune Response by Varicella Zoster Virus

Varicella zoster virus (VZV) is the causative agent of chickenpox (varicella) and shingles (herpes zoster). VZV and other members of the herpesvirus family are distinguished by their ability to establish a latent infection, with the potential to reactivate and spread virus to other susceptible individuals. This lifelong relationship continually subjects VZV to the host immune system and as such VZV has evolved a plethora of strategies to evade and manipulate the immune response. This review will focus on our current understanding of the innate anti-viral control mechanisms faced by VZV. We will also discuss the diverse array of strategies employed by VZV to regulate these innate immune responses and highlight new knowledge on the interactions between VZV and human innate immune cells.

Virology Downunder, a meeting commentary from the 2019 Lorne Infection and Immunity Conference, Australia

The aim of this article is to summarise the virology content presented at the 9th Lorne Infection and Immunity Conference, Australia, in February 2019. The broad program included virology as a key theme, and the commentary herein highlights several key virology presentations at the meeting.

Modeling Varicella Zoster Virus Persistence and Reactivation - Closer to Resolving a Perplexing Persistent State

The latent state of the human herpesvirus varicella zoster virus (VZV) has remained enigmatic and controversial. While it is well substantiated that VZV persistence is established in neurons after the primary infection (varicella or chickenpox), we know little of the types of neurons harboring latent virus genomes, if all can potentially reactivate, what exactly drives the reactivation process, and the role of immunity in the control of latency. Viral gene expression during latency has been particularly difficult to resolve, although very recent advances indicate that it is more restrictive than was once thought. We do not yet understand how genes expressed in latency function in the maintenance and reactivation processes. Model systems of latency are needed to pursue these questions. This has been especially challenging for VZV because the development of in vivo models of VZV infection has proven difficult. Given that up to one third of the population will clinically reactivate VZV to develop herpes zoster (shingles) and suffer from its common long term problematic sequelae, there is still a need for both in vivo and in vitro model systems. This review will summarize the evolution of models of VZV persistence and address insights that have arisen from the establishment of new in vitro human neuron culture systems that not only harbor a latent state, but permit experimental reactivation and renewed virus production. These models will be discussed in light of the recent data gleaned from the study of VZV latency in human cadaver ganglia.

Polyinosinic-polycytidylic acid induces innate immune responses via Toll-like receptor 3 in human ovarian granulosa cells

The ovary can be infected by a variety of viruses, which may come from the female reproductive tract or the peritoneum. The innate immune responses to viral infection in the human ovary are poorly understood. The present study demonstrated that human ovarian granulosa cells had innate immune activity in response to viral RNA challenge through Toll-like receptor 3 (TLR3) activation. TLR3 was constitutively expressed in the human ovary and predominantly located in granulosa cells of developmental follicles at all stages. Polyinosinic-polycytidylic acid [poly (I:C)], a synthetic viral double-stranded RNA analog, induced innate immune responses in human ovarian granulosa cells and affected endocrine function. Poly (I:C) significantly upregulated proinflammatory cytokines, including tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-1β and type I interferon (IFN-α/β), and the innate immune responses were significantly reduced by blocking TLR3 signaling. Furthermore, poly (I:C) induced antiviral genes expression, including 2'-5'-oligoadenylate synthetase, Mx GTPase 1, IFN-stimulating gene 15 and double-stranded RNA-activated protein kinase R. In contrast, the expression of P450 aromatase and inhibin was dramatically inhibited by poly (I:C). Both silencing of TLR3 and neutralizing TNF-α reversed the inhibitory effect of poly (I:C) on P450 aromatase and inhibin expression. Our study demonstrates that granulosa cells play a potential role in innate immune protection against viral infection in the normal human ovary, and the innate immune response perturbs cell endocrine function.