Tropism of varicella-zoster virus for human tonsillar CD4(+) T lymphocytes that express activation, memory, and skin homing markers

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.

The mechanisms of nerve injury caused by viral infection in the occurrence of gastrointestinal motility disorder-related diseases

Gastrointestinal motility refers to the peristalsis and contractility of gastrointestinal muscles, including the force and frequency of gastrointestinal muscle contraction. Gastrointestinal motility maintains the normal digestive function of the human body and is a critical component of the physiological function of the digestive tract. At present, gastrointestinal motility disorder-related diseases are gradually affecting human production and life. In recent years, it has been consistently reported that the enteric nervous system has a coordinating and controlling role in gastrointestinal motility. Motility disorders are closely related to functional or anatomical changes in the gastrointestinal nervous system. At the same time, some viral infections, such as herpes simplex virus and varicella-zoster virus infections, can cause damage to the gastrointestinal nervous system. Therefore, this paper describes the mechanisms of viral infection in the gastrointestinal nervous system and the associated clinical manifestations. Studies have indicated that the means by which viruses can cause the infection of the enteric nervous system are various, including retrograde transport, hematogenous transmission and centrifugal transmission from the central nervous system. When viruses infect the enteric nervous system, they can cause clinical symptoms, such as abdominal pain, abdominal distension, early satiation, belching, diarrhea, and constipation, by recruiting macrophages, lymphocytes and neutrophils and regulating intestinal microbes. The findings of several case‒control studies suggest that viruses are the cause of some gastrointestinal motility disorders. It is concluded that one of the causes of gastrointestinal motility disorders is viral infection of the enteric nervous system. In such disorders, the relationships between viruses and nerves remain to be studied more deeply. Further studies are necessary to evaluate whether prophylactic antiviral therapy is feasible in gastrointestinal motility disorders.

[Transverse myelitis and cauda equina syndrome followed by varicella in a patient with varicella-zoster virus infection]

A 74-year-old man was admitted to our hospital with complaints of weakness in the lower extremities, urinary retention for 10 days, and generalized vesicular rash for 7 days. Spinal magnetic resonance imaging showed contrast enhancement at the Th12-L1 level of the spinal cord and cauda equina. Serum and cerebrospinal fluid varicella-zoster virus (VZV)-immunoglobulin (Ig) G antibody titers were markedly elevated, and VZV-IgM was detected in cerebrospinal fluid. The patient was diagnosed with VZV transverse myelitis and cauda equina syndrome with subsequent varicella and was treated with acyclovir and prednisolone. Two months later, muscle weakness, and dysuria had almost completely resolved. We hypothesize that latent VZV in the ganglia reactivated and caused transverse myelitis, which subsequently spread to the body via the bloodstream, resulting in the development of varicella.

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.

A Rare Case of Varicella-Zoster Virus Encephalitis Presenting With Lost Ability to Play the Piano in an Immunocompetent Pediatric Patient

Varicella-zoster virus (VZV) is a member of the alpha-herpesvirus family, which can occasionally cause severe neurological complications such as encephalitis. In this case report, we discuss a rare finding of VZV encephalitis in which an immunocompetent pediatric patient, vaccinated against varicella, presented with altered mental status and no vesicular rash. A 15-year-old male presented to the Emergency Department with progressively worsening altered mental status over the past three days. The patient's mother stated that he was exhibiting frequent memory lapses as well as the sudden loss of the ability to play the piano. After admission to the pediatric general floor, lumbar puncture was performed and cerebrospinal fluid analysis returned positive for VZV, confirmed by polymerase chain reaction. The patient was then started on intravenous (IV) acyclovir at a dose of 650 mg every 8 hours to treat VZV-induced encephalitis. While the patient continued to have intermittent episodes of confusion and headaches, his overall condition improved, and by day 4, he was able to resume playing the piano and ukulele. The patient was discharged on day 8 with no home medications, and a follow-up with this primary care physician was scheduled. This patient is one of only four recorded cases of VZV encephalitis in immunocompetent children. It is extremely rare to encounter pediatric patients with this diagnosis and, as such, can elude physicians when developing differential diagnoses. If VZV is suspected, a lumbar puncture should be performed promptly, and, if confirmed, IV acyclovir should be started. Furthermore, this case highlights the need for future research with regard to VZV and potential predisposing factors in immunocompetent patients.

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

During primary infection, varicella zoster virus (VZV) infects epithelial cells in the respiratory lymphoid organs and mucosa. Subsequent infection of lymphocytes, T cells in particular, causes primary viremia allowing systemic spread throughout the host, including the skin. This results in the expression of cytokines, including interferons (IFNs) which partly limit primary infection. VZV also spreads from skin keratinocytes to lymphocytes prior to secondary viremia. How VZV infects lymphocytes from epithelial cells while evading the cytokine response has not been fully established. Here, we show that VZV glycoprotein C (gC) binds IFN-γ and modifies its activity. Transcriptomic analysis revealed that gC in combination with IFN-γ increased the expression of a small subset of IFN-stimulated genes (ISGs), including intercellular adhesion molecule 1 (ICAM1), as well as several chemokines and immunomodulatory genes. The higher ICAM1 protein level at the plasma membrane of epithelial cells resulted in lymphocyte function-associated antigen 1 (LFA-1)-dependent T cell adhesion. This gC activity required a stable interaction with IFN-γ and signalling through the IFN-γ receptor. Finally, the presence of gC during infection increased VZV spread from epithelial cells to peripheral blood mononuclear cells. This constitutes the discovery of a novel strategy to modulate the activity of IFN-γ, inducing the expression of a subset of ISGs, leading to enhanced T cell adhesion and virus spread.

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.

A simple transwell-based infection system for obtaining pure populations of VZV-infected cells

Varicella-Zoster virus (VZV) is a human herpesvirus and causes chickenpox and shingles. Research into its molecular virology has been hampered by a lack of methods for generation of high-titre, cell-free infectious virus preparations. VZV propagation and infection in vitro are therefore commonly achieved by co-culture of uninfected 'target' cells with infected 'inoculum' cells. A major drawback of this approach is that it results in mixed cell populations after infection. To overcome this limitation we developed a transwell-based VZV infection system. Infected inoculum cells and uninfected target cells are spatially separated by a transwell membrane. While cell-cell contact and VZV spread can occur through membrane pores, the two cell populations do not mix. This simple protocol requires no special instrumentation or reagents. We successfully used this system for infection of a range of target cells and obtained pure populations for downstream analyses such as flow cytometry and RT-qPCR. In sum, we developed a broadly applicable approach to study the molecular and cellular biology as well as host-pathogen interactions of VZV.

G-quadruplexes formed by Varicella-Zoster virus reiteration sequences suppress expression of glycoprotein C and regulate viral cell-to-cell spread

G-quadruplex (G4) formed by repetitive guanosine-rich sequences plays important roles in diverse cellular processes; however, its roles in viral infection are not fully understood. In this study, we investigated the genome-wide distribution of G4-forming sequences (G4 motifs) in Varicella-Zoster virus (VZV) and found that G4 motifs are enriched in the internal repeat short and the terminal repeat short regions flanking the unique short region and also in some reiteration (R) sequence regions. A high density of G4 motifs in the R2 region was found on the template strand of ORF14, which encodes glycoprotein C (gC), a virulent factor for viral growth in skin. Analyses such as circular dichroism spectroscopy, thermal difference spectra, and native polyacrylamide gel electrophoresis with oligodeoxynucleotides demonstrated that several G4 motifs in ORF14 form stable G4 structures. In transfection assays, gC expression from the G4-disrupted ORF14 gene was increased at the transcriptional level and became more resistant to suppression by G4-ligand treatment. The recombinant virus containing the G4-disrupted ORF14 gene expressed a higher level of gC mRNA, while it showed a slightly reduced growth. This G4-disrupted ORF14 virus produced smaller plaques than the wild-type virus. Our results demonstrate that G4 formation via reiteration sequences suppresses gC expression during VZV infection and regulates viral cell-to-cell spread.

The Biology of Varicella-Zoster Virus Replication in the Skin

The replication of varicella-zoster virus (VZV) in skin is critical to its pathogenesis and spread. Primary infection causes chickenpox, which is characterised by centrally distributed skin blistering lesions that are rich in infectious virus. Cell-free virus in the cutaneous blistering lesions not only spreads to cause further cases, but infects sensory nerve endings, leading to the establishment of lifelong latency in sensory and autonomic ganglia. The reactivation of virus to cause herpes zoster is again characterised by localised painful skin blistering rash containing infectious virus. The development of in vitro and in vivo models of VZV skin replication has revealed aspects of VZV replication and pathogenesis in this important target organ and improved our understanding of the vaccine strain vOKa attenuation. In this review, we outline the current knowledge on VZV interaction with host signalling pathways, the viral association with proteins associated with epidermal terminal differentiation, and how these interconnect with the VZV life cycle to facilitate viral replication and shedding.

Stroke-like Symptoms as Presenting Signs of Varicella Zoster Meningitis in an Immunocompetent Adult

Varicella zoster is one of the common causes of aseptic meningitis, typically seen in immunosuppressed individuals and rarely in the immunocompetent. The varicella zoster virus (VZV) infection is normally associated with a dermatomal rash in the abdomen with spread to the back. The small prevalence of VZV in immunocompetent individuals may be due to lack of recognition; thus, it is always important to keep it in mind when meningitis is in the differential. Here, we present a case of varicella zoster meningitis in an immunocompetent adult presenting with slurred speech, dizziness, and episodes of confusion.

Varicella Zoster Virus Neuronal Latency and Reactivation Modeled in Vitro

Latency and reactivation in neurons are critical aspects of VZV pathogenesis that have historically been difficult to investigate. Viral genomes are retained in many human ganglia after the primary infection, varicella; and about one-third of the naturally infected VZV seropositive population reactivates latent virus, which most often clinically manifests as herpes zoster (HZ or Shingles). HZ is frequently complicated by acute and chronic debilitating pain for which there remains a need for more effective treatment options. Understanding of the latent state is likely to be essential in the design of strategies to reduce reactivation. Experimentally addressing VZV latency has been difficult because of the strict human species specificity of VZV and the fact that until recently, experimental reactivation had not been achieved. We do not yet know the neuron subtypes that harbor latent genomes, whether all can potentially reactivate, what the drivers of VZV reactivation are, and how immunity interplays with the latent state to control reactivation. However, recent advances have enabled a picture of VZV latency to start to emerge. The first is the ability to detect the latent viral genome and its expression in human ganglionic tissues with extraordinary sensitivity. The second, the subject of this chapter, is the development of in vitro human neuron systems permitting the modeling of latent states that can be experimentally reactivated. This review will summarize recent advances of in vitro models of neuronal VZV latency and reactivation, the limitations of the current systems, and discuss outstanding questions and future directions regarding these processes using these and yet to be developed models. Results obtained from the in vitro models to date will also be discussed in light of the recent data gleaned from studies of VZV latency and gene expression learned from human cadaver ganglia, especially the discovery of VZV latency transcripts that seem to parallel the long-studied latency-associated transcripts of other neurotropic alphaherpesviruses.

Increased frequency of HLA-A*02 in patients with atherosclerosis is associated with VZV seropositivity

BACKGROUND

HLA molecules are inherited key molecules in the immune inflammation and specific responses to environmental pathogens. We investigated the association of HLA-A alleles with Varicella zoster virus (VZV) seropositivity in patients with atherosclerosis (AS).

MATERIALS AND METHODS

Plasma Anti-VZV IgG and molecular HLA type were detected in 203 (100 AS⁺ and 103 AS^-) individuals.

RESULTS

Of 100 AS⁺ individuals, 66 were anti-VZV⁺ and 34 were anti-VZV^-. Of 103 age/sex-matched AS^- individuals, 59 were anti-VZV⁺ and 44 were anti-VZV^-. Anti-VZV-IgG in AS⁺ cases was higher than AS^- controls (p = .034). The mean anti-VZV IgG in HLA-A*02⁺AS⁺ individuals was higher than HLA-A*02⁺AS^- controls (p < .001). HLA-A*02 was associated with VZV-seropositivity (p = .01) in AS⁺ patients. A higher frequency of HLA-A*02-allele in AS⁺ patients compared to AS^- controls (p = .015) and an accumulation of HLA-A*02-allele in AS⁺ anti-VZV⁺ group (33.3%, p = .004) was observed.

CONCLUSIONS

HLA-A alleles and immune responses to VZV are associated with clinical atherosclerosis.

Insights into the pathogenesis of varicella viruses

Purpose of review

Varicella zoster virus (VZV) is a highly contagious, neurotropic alpha herpes virus that causes varicella (chickenpox). VZV establishes lifelong latency in the sensory ganglia from which it can reactivate to induce herpes zoster (HZ), a painful disease that primarily affects older individuals and those who are immune-suppressed. Given that VZV infection is highly specific to humans, developing a reliable in vivo model that recapitulates the hallmarks of VZV infection has been challenging. Simian Varicella Virus (SVV) infection in nonhuman primates reproduces the cardinal features of VZV infections in humans and allows the study of varicella virus pathogenesis in the natural host. In this review, we summarize our current knowledge about genomic and virion structure of varicelloviruses as well as viral pathogenesis and antiviral immune responses during acute infection, latency and reactivation. We also examine the immune evasion mechanisms developed by varicelloviruses to escape the host immune responses and the current vaccines available for protecting individuals against chickenpox and herpes zoster.

Recent findings

Data from recent studies suggest that infected T cells are important for viral dissemination to the cutaneous sites of infection as well as site of latency and that a viral latency-associated transcript might play a role in the transition from lytic infection to latency and then reactivation.

Summary

Recent studies have provided exciting insights into mechanisms of varicelloviruses pathogenesis such as the critical role of T cells in VZV/SVV dissemination from the respiratory mucosa to the skin and the sensory ganglia; the ability of VZV/SVV to interfere with host defense; and the identification of VLT transcripts in latently infected ganglia. However, our understanding of these phenomena remains poorly understood. Therefore, it is critical that we continue to investigate host-pathogen interactions during varicelloviruses infection. These studies will lead to a deeper understanding of VZV biology as well as novel aspects of cell biology.

Viral Load and Cell Tropism During Early Latent Equid Herpesvirus 1 Infection Differ Over Time in Lymphoid and Neural Tissue Samples From Experimentally Infected Horses

Upper respiratory tract infections with Equid Herpesvirus 1 (EHV-1) typically result in a peripheral blood mononuclear cell-associated viremia, which can lead to vasculopathy in the central nervous system. Primary EHV-1 infection also likely establishes latency in trigeminal ganglia (TG) via retrograde axonal transport and in respiratory tract-associated lymphatic tissue. However, latency establishment and reactivation are poorly understood. To characterize the pathogenesis of EHV-1 latency establishment and maintenance, two separate groups of yearling horses were experimentally infected intranasally with EHV-1, strain Ab4, and euthanized 30 days post infection (dpi), (n = 9) and 70 dpi (n = 6). During necropsy, TG, sympathetic trunk (ST), retropharyngeal and mesenteric lymph nodes (RLn, MesLn) and kidney samples were collected. Viral DNA was detected by quantitative PCR (qPCR) in TG, ST, RLn, and MesLn samples in horses 30 and 70 dpi. The number of positive TG, RLn and MesLn samples was reduced when comparing horses 30 and 70 dpi and the viral copy number in TG and RLn significantly declined from 30 to 70 dpi. EHV-1 late gene glycoprotein B reverse transcriptase PCR and IHC results for viral protein were consistently negative, thus lytic replication was excluded in the present study. Mild inflammation could be detected in all neural tissue samples and inflammatory infiltrates mainly consisted of CD3+ T-lymphocytes (T-cells), frequently localized in close proximity to neuronal cell bodies. To identify latently infected cell types, in situ hybridization (ISH, RNAScope®) detecting viral DNA was used on selected qPCR- positive neural tissue sections. In ganglia 30 dpi, EHV-1 ISH signal was located in the neurons of TG and ST, but also in non-neuronal support or interstitial cells surrounding the neuron. In contrast, distinct EHV-1 signal could only be observed in neurons of TG 70 dpi. Overall, detection of latent EHV-1 in abdominal tissue samples and non-neuronal cell localization suggests, that EHV-1 uses T-cells during viremia as alternative route toward latency locations in addition to retrograde neuronal transport. We therefore hypothesize that EHV-1 follows the same latency pathways as its close relative human pathogen Varicella Zoster Virus.

The Use of Single Cell Mass Cytometry to Define the Molecular Mechanisms of Varicella-Zoster Virus Lymphotropism

Unraveling the heterogeneity in biological systems provides the key to understanding of the fundamental dynamics that regulate host pathogen relationships at the single cell level. While most studies have determined virus-host cell interactions using cultured cells in bulk, recent advances in deep protein profiling from single cells enable the understanding of the dynamic response equilibrium of single cells even within the same cell types. Mass cytometry allows the simultaneous detection of multiple proteins in single cells, which helps to evaluate alterations in multiple signaling networks that work in tandem in deciding the response of a cell to the presence of a pathogen or other stimulus. In applying this technique to studying varicella zoster virus (VZV), it was possible to better understand the molecular basis for lymphotropism of the virus and how virus-induced effects on T cells promoted skin tropism. While the ability of VZV to manifest itself in the skin is well established, how the virus is transported to the skin and causes the characteristic VZV skin lesions was not well elucidated. Through mass cytometry analysis of VZV-infected tonsil T cells, we were able to observe that VZV unleashes a “remodeling” program in the infected T cells that not only makes these T cells more skin tropic but also at the same time induces changes that make these T cells unlikely to respond to immune stimulation during the journey to the skin.

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.

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.

Varicella Zoster Meningitis with Hypoglycorrhachia on Cerebrospinal Fluid (CSF) Analysis in a Young Immunocompetent Host without a Rash

BACKGROUND Varicella zoster virus (VZV) is a common viral infection, with primary infection presenting as fevers and pruritic vesicular rash. After staying dormant in the dorsal root ganglia, reactivation can lead to secondary infection. Meningitis is a rare a complication of VZV infection. CASE REPORT We report a case of a 44-year-old woman with no past medical history, presenting with severe frontal headache without meningeal signs or fevers, found to have VZV meningitis. CSF analysis revealed hypoglycorrhachia and she was treated successfully with combination of intravenous acyclovir and oral valacyclovir. CONCLUSIONS VZV meningitis can present with subtle clinical signs and symptoms and should be considered as a possible etiology for headaches without identifiable cause.

Prevalence of human herpesviruses infections in nonmalignant tonsils: The SPLIT study

OBJECTIVE

To assess the prevalence of all known human herpesviruses (HHV) in tonsils of an age-stratified large sample of immunocompetent children and adults.

METHODS

Patients undergoing tonsillectomy for benign indications were recruited in 19 French hospitals. After resection, the entire outer surfaces of right and left half tonsils were extensively brushed. A highly sensitive species-specific multiplex assay was used to detect herpes simplex virus 1 (HSV1), HSV2, Epstein-Barr virus (EBV; types 1 and 2), and human cytomegalovirus (CMV) DNA in 688, as well as varicella zoster virus (VZV), HHV6A, HHV6B, HHV7, and Kaposi's sarcoma-associated herpesvirus (KSHV) DNA in a subset of 440 tonsil brushings.

RESULTS

Overall 85% of tonsil brushing samples were infected with at least one HHV species. HHV7 and EBV were the most prevalent (≈70%), followed by HHV6B (≈50%), HSV1, CMV, VZV (≈2%), and KSHV and HSV2 (<1%), while HHV6A was not detected. EBV prevalence was significantly higher in adults than in children, whereas it was opposite for HHV6B and VZV. No difference in HHV prevalence was observed by sex. In multivariate analysis, EBV detection was associated with age greater than or equal to 15 years (prevalence ratio [PR] = 1.8; 95% confidence interval [CI]: 1.5-2.3) and marginally with tobacco smoking (PR = 1.2; 95% CI: 1.1-1.3).

CONCLUSION

Differing patterns of HHV infection in tonsils in a large age-stratified population were described. This study is by far the largest available and shows that EBV, HHV6B, and HHV7 are commonly detected in the tonsils in both men and women, in contrast to other HHVs.

Equine Herpesvirus 1 Bridles T Lymphocytes To Reach Its Target Organs

Equine herpesvirus 1 (EHV1) is an ancestral alphaherpesvirus that is related to herpes simplex virus 1 and causes respiratory, reproductive, and neurological disorders in Equidae. EHV1 is indisputably a master at exploiting leukocytes to reach its target organs, accordingly evading the host immunity. However, the role of T lymphocytes in cell-associated viremia remains poorly understood. Here we show that activated T lymphocytes efficiently become infected and support viral replication despite the presence of protective immunity. We demonstrate a restricted expression of viral proteins on the surfaces of infected T cells, which prevents immune recognition. In addition, we indicate a hampered release of progeny, which results in the accumulation of nucleocapsids in the T cell nucleus. Upon engagement with the target endothelium, late viral proteins orchestrate viral synapse formation and viral transfer to the contact cell. Our findings have significant implications for the understanding of EHV1 pathogenesis, which is essential for developing innovative therapies to prevent the devastating clinical symptoms of infection.

Equine herpesvirus 1 (EHV1) replicates in the respiratory epithelium and disseminates through the body via a cell-associated viremia in leukocytes, despite the presence of neutralizing antibodies. “Hijacked” leukocytes, previously identified as monocytic cells and T lymphocytes, transmit EHV1 to endothelial cells of the endometrium or central nervous system, causing reproductive (abortigenic variants) or neurological (neurological variants) disorders. In the present study, we questioned the potential route of EHV1 infection of T lymphocytes and how EHV1 misuses T lymphocytes as a vehicle to reach the endothelium of the target organs in the absence or presence of immune surveillance. Viral replication was evaluated in activated and quiescent primary T lymphocytes, and the results demonstrated increased infection of activated versus quiescent, CD4⁺ versus CD8⁺, and blood- versus lymph node-derived T cells. Moreover, primarily infected respiratory epithelial cells and circulating monocytic cells efficiently transferred virions to T lymphocytes in the presence of neutralizing antibodies. Albeit T-lymphocytes express all classes of viral proteins early in infection, the expression of viral glycoproteins on their cell surface was restricted. In addition, the release of viral progeny was hampered, resulting in the accumulation of viral nucleocapsids in the T cell nucleus. During contact of infected T lymphocytes with endothelial cells, a late viral protein(s) orchestrates T cell polarization and synapse formation, followed by anterograde dynein-mediated transport and transfer of viral progeny to the engaged cell. This represents a sophisticated but efficient immune evasion strategy to allow transfer of progeny virus from T lymphocytes to adjacent target cells. These results demonstrate that T lymphocytes are susceptible to EHV1 infection and that cell-cell contact transmits infectious virus to and from T lymphocytes.

IMPORTANCE Equine herpesvirus 1 (EHV1) is an ancestral alphaherpesvirus that is related to herpes simplex virus 1 and causes respiratory, reproductive, and neurological disorders in Equidae. EHV1 is indisputably a master at exploiting leukocytes to reach its target organs, accordingly evading the host immunity. However, the role of T lymphocytes in cell-associated viremia remains poorly understood. Here we show that activated T lymphocytes efficiently become infected and support viral replication despite the presence of protective immunity. We demonstrate a restricted expression of viral proteins on the surfaces of infected T cells, which prevents immune recognition. In addition, we indicate a hampered release of progeny, which results in the accumulation of nucleocapsids in the T cell nucleus. Upon engagement with the target endothelium, late viral proteins orchestrate viral synapse formation and viral transfer to the contact cell. Our findings have significant implications for the understanding of EHV1 pathogenesis, which is essential for developing innovative therapies to prevent the devastating clinical symptoms of infection.

Varicella zoster virus productively infects human peripheral blood mononuclear cells to modulate expression of immunoinhibitory proteins and blocking PD-L1 enhances virus-specific CD8+ T cell effector function

Varicella zoster virus (VZV) is a lymphotropic alpha-herpesvirinae subfamily member that produces varicella on primary infection and causes zoster, vascular disease and vision loss upon reactivation from latency. VZV-infected peripheral blood mononuclear cells (PBMCs) disseminate virus to distal organs to produce clinical disease. To assess immune evasion strategies elicited by VZV that may contribute to dissemination of infection, human PBMCs and VZV-specific CD8+ T cells (V-CD8+) were mock- or VZV-infected and analyzed for immunoinhibitory protein PD-1, PD-L1, PD-L2, CTLA-4, LAG-3 and TIM-3 expression using flow cytometry. All VZV-infected PBMCs (monocytes, NK, NKT, B cells, CD4+ and CD8+ T cells) and V-CD8+ showed significant elevations in PD-L1 expression compared to uninfected cells. VZV induced PD-L2 expression in B cells and V-CD8+. Only VZV-infected CD8+ T cells, NKT cells and V-CD8+ upregulated PD-1 expression, the immunoinhibitory receptor for PD-L1/PD-L2. VZV induced CTLA-4 expression only in V-CD8+ and no significant changes in LAG-3 or TIM-3 expression were observed in V-CD8+ or PBMC T cells. To test whether PD-L1, PD-L2 or CTLA-4 regulates V-CD8+ effector function, autologous PBMCs were VZV-infected and co-cultured with V-CD8+ cells in the presence of blocking antibodies against PD-L1, PD-L2 or CTLA-4; ELISAs revealed significant elevations in IFNγ only upon blocking of PD-L1. Together, these results identified additional immune cells that are permissive to VZV infection (monocytes, B cells and NKT cells); along with a novel mechanism for inhibiting CD8+ T cell effector function through induction of PD-L1 expression.

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

Varicella-zoster virus (VZV) is associated with viremia during primary infection that is presumed to stem from infection of circulating immune cells. While VZV has been shown to be capable of infecting a number of different subsets of circulating immune cells, such as T cells, dendritic cells, and NK cells, less is known about the interaction between VZV and monocytes. Here, we demonstrate that blood-derived human monocytes are permissive to VZV replication in vitro VZV-infected monocytes exhibited each temporal class of VZV gene expression, as evidenced by immunofluorescent staining. VZV virions were observed on the cell surface and viral nucleocapsids were observed in the nucleus of VZV-infected monocytes by scanning electron microscopy. In addition, VZV-infected monocytes were able to transfer infectious virus to human fibroblasts. Infected monocytes displayed impaired dextran-mediated endocytosis, and cell surface immunophenotyping revealed the downregulation of CD14, HLA-DR, CD11b, and the macrophage colony-stimulating factor (M-CSF) receptor. Analysis of the impact of VZV infection on M-CSF-stimulated monocyte-to-macrophage differentiation demonstrated the loss of cell viability, indicating that VZV-infected monocytes were unable to differentiate into viable macrophages. In contrast, macrophages differentiated from monocytes prior to exposure to VZV were highly permissive to infection. This study defines the permissiveness of these myeloid cell types to productive VZV infection and identifies the functional impairment of VZV-infected monocytes.IMPORTANCE Primary VZV infection results in the widespread dissemination of the virus throughout the host. Viral transportation is known to be directly influenced by susceptible immune cells in the circulation. Moreover, infection of immune cells by VZV results in attenuation of the antiviral mechanisms used to control infection and limit spread. Here, we provide evidence that human monocytes, which are highly abundant in the circulation, are permissive to productive VZV infection. Furthermore, monocyte-derived macrophages were also highly permissive to VZV infection, although VZV-infected monocytes were unable to differentiate into macrophages. Exploring the relationships between VZV and permissive immune cells, such as human monocytes and macrophages, elucidates novel immune evasion strategies and provides further insight into the control that VZV has over the immune system.

T Lymphocytes as Measurable Targets of Protection and Vaccination Against Viral Disorders

Continuous epidemiological surveillance of existing and emerging viruses and their associated disorders is gaining importance in light of their abilities to cause unpredictable outbreaks as a result of increased travel and vaccination choices by steadily growing and aging populations. Close surveillance of outbreaks and herd immunity are also at the forefront, even in industrialized countries, where previously eradicated viruses are now at risk of re-emergence due to instances of strain recombination, contractions in viral vector geographies, and from their potential use as agents of bioterrorism. There is a great need for the rational design of current and future vaccines targeting viruses, with a strong focus on vaccine targeting of adaptive immune effector memory T cells as the gold standard of immunity conferring long-lived protection against a wide variety of pathogens and malignancies. Here, we review viruses that have historically caused large outbreaks and severe lethal disorders, including respiratory, gastric, skin, hepatic, neurologic, and hemorrhagic fevers. To observe trends in vaccinology against these viral disorders, we describe viral genetic, replication, transmission, and tropism, host-immune evasion strategies, and the epidemiology and health risks of their associated syndromes. We focus on immunity generated against both natural infection and vaccination, where a steady shift in conferred vaccination immunogenicity is observed from quantifying activated and proliferating, long-lived effector memory T cell subsets, as the prominent biomarkers of long-term immunity against viruses and their associated disorders causing high morbidity and mortality rates.

Varicella-Zoster Virus and the Enteric Nervous System

Varicella zoster virus (VZV) infects and becomes latent in sensory, enteric, and other autonomic neurons during the viremia of varicella. Reactivation of VZV in neurons that project to the skin causes the rash of zoster; however, reactivation of VZV in enteric neurons can cause a painful gastrointestinal disorder ("enteric zoster") without cutaneous manifestations. Detection of VZV DNA in saliva of patients with gastrointestinal symptoms may suggest enteric zoster. This diagnosis is reinforced by observing a response to antiviral therapy and can be confirmed by detecting VZV gene products in intestinal mucosal biopsies. We developed an in vivo guinea pig model that may be useful in studies of VZV latency and reactivation. VZV-infected lymphocytes are used to induce latent infection in sensory and enteric neurons; evidence suggests that exosomes and stimulator of interferon genes (STING) may, by preventing proliferation play roles in the establishment of neuronal latency.

Molecular Aspects of Varicella-Zoster Virus Latency

Primary varicella-zoster virus (VZV) infection causes varicella (chickenpox) and the establishment of a lifelong latent infection in ganglionic neurons. VZV reactivates in about one-third of infected individuals to cause herpes zoster, often accompanied by neurological complications. The restricted host range of VZV and, until recently, a lack of suitable in vitro models have seriously hampered molecular studies of VZV latency. Nevertheless, recent technological advances facilitated a series of exciting studies that resulted in the discovery of a VZV latency-associated transcript (VLT) and provide novel insights into our understanding of VZV latency and factors that may initiate reactivation. Deducing the function(s) of VLT and the molecular mechanisms involved should now be considered a priority to improve our understanding of factors that govern VZV latency and reactivation. In this review, we summarize the implications of recent discoveries in the VZV latency field from both a virus and host perspective and provide a roadmap for future studies.

Varicella zoster virus productively infects human natural killer cells and manipulates phenotype

Varicella zoster virus (VZV) is a ubiquitous human alphaherpesvirus, responsible for varicella upon primary infection and herpes zoster following reactivation from latency. To establish lifelong infection, VZV employs strategies to evade and manipulate the immune system to its advantage in disseminating virus. As innate lymphocytes, natural killer (NK) cells are part of the early immune response to infection, and have been implicated in controlling VZV infection in patients. Understanding of how VZV directly interacts with NK cells, however, has not been investigated in detail. In this study, we provide the first evidence that VZV is capable of infecting human NK cells from peripheral blood in vitro. VZV infection of NK cells is productive, supporting the full kinetic cascade of viral gene expression and producing new infectious virus which was transmitted to epithelial cells in culture. We determined by flow cytometry that NK cell infection with VZV was not only preferential for the mature CD56^dim NK cell subset, but also drove acquisition of the terminally-differentiated maturity marker CD57. Interpretation of high dimensional flow cytometry data with tSNE analysis revealed that culture of NK cells with VZV also induced a potent loss of expression of the low-affinity IgG Fc receptor CD16 on the cell surface. Notably, VZV infection of NK cells upregulated surface expression of chemokine receptors associated with trafficking to the skin –a crucial site in VZV disease where highly infectious lesions develop. We demonstrate that VZV actively manipulates the NK cell phenotype through productive infection, and propose a potential role for NK cells in VZV pathogenesis.

Varicella zoster virus (VZV) is a pervasive pathogen, causing chickenpox during primary infection and shingles when the virus reactivates from latency. VZV is therefore a lifelong infection for humans, warranting investigation of how this virus interacts with the immune system. One of the first immune cells to respond to viral infection are natural killer (NK) cells, yet little is known about how VZV interacts with NK cells. We demonstrate for the first time that VZV infects human blood NK cells and can use them to pass on infection to other cells in culture. Furthermore, VZV displays a predilection for infecting mature NK cells, and amplifies expression of receptors that would promote trafficking to the skin– the site of highly infectious lesions during chickenpox and shingles. Our findings suggest a role for NK cells in VZV disease and enhances our understanding of how lifelong infections interact with the human immune system.

Simian Varicella Virus Infects Enteric Neurons and α4β7 Integrin-Expressing Gut-Tropic T-Cells in Nonhuman Primates

The pathogenesis of enteric zoster, a rare debilitating complication of reactivation of latent varicella-zoster virus (VZV) in the enteric nervous system (ENS), is largely unknown. Infection of monkeys with the closely related Varicellovirus simian varicella virus (SVV) mimics VZV disease in humans. In this study, we determined the applicability of the SVV nonhuman primate model to study Varicellovirus infection of the ENS. We confirmed VZV infection of the gut in latently infected adults and demonstrated that SVV DNA was similarly present in gut of monkeys latently infected with SVV using quantitative real-time PCR. In situ analyses showed that enteric neurons expressed SVV open reading frame (ORF) 63 RNA, but not viral nucleocapsid proteins, suggestive of latent ENS infection. During primary infection, SVV-infected T-cells were detected in gut-draining mesenteric lymph nodes and located in close vicinity to enteric nerves in the gut. Furthermore, flow cytometric analysis of blood from acutely SVV-infected monkeys demonstrated that virus-infected T-cells expressed the gut-homing receptor α4β7 integrin. Collectively, the data demonstrate that SVV infects ENS neurons during primary infection and supports the role of T-cells in virus dissemination to the gut. Because SVV reactivation can be experimentally induced, the SVV nonhuman primate model holds great potential to study the pathogenesis of enteric zoster.

Increased risk of herpes zoster in patients with psoriasis: A population-based retrospective cohort study

Objectives

The risk of herpes zoster (HZ) between patients with psoriasis receiving and not receiving systemic therapy has received increasing attention. This study investigated the association of psoriasis with the risk of HZ.

Methods

We conducted a population-based retrospective cohort study by using the Taiwan National Health Insurance Research Database. The psoriasis cohort consisted of 4077 patients with newly diagnosed psoriasis between 2000 and 2006. Each patient with psoriasis was frequency-matched with four people without psoriasis, by sex, age and index year. (nonpsoriasis cohort; 16308 subjects). Patients who received systemic therapy were classified as having severe psoriasis, whereas those who did not receive systemic therapy were classified as having mild psoriasis. The Cox proportional hazards regression analysis was conducted to estimate the association between psoriasis and HZ risk.

Results

The overall incidence density rate of HZ in the psoriasis cohort than in the nonpsoriasis cohort (4.50 vs. 3.44 per 1,000 person-years), with a multivariable Cox proportional hazards model measured adjusted HR of 1.29 [95% confidence interval (CI) = 1.07–1.56]. In additional, compared with the nonpsoriasis cohort, the risk of HZ was higher in the severe psoriasis cohort than in the nonpsoriasis cohort (adjusted hazard ratio [HR], 1.61; 95% confidence interval [CI], 1.15–2.27). The comparison between psoriasis and nonpsoriasis cohorts revealed a greatest magnitude risk of HZ in women (adjusted HR, 1.36; 95% CI, 1.04–1.79), study participants in the age group of 20–39 years (adjusted HR, 1.77; 95% CI, 1.17–2.66), and study participants without any comorbidities (adjusted HR, 1.37; 95% CI, 1.02–1.84).

Conclusions

Our results suggest that psoriasis is associated with an increased risk of HZ, which involves differences in sex and age. Although systemic therapy may have a major role in the risk of HZ, the intrinsic factors of psoriasis cannot be excluded.

Simian varicella virus causes robust transcriptional changes in T cells that support viral replication

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T cells play a major role in varicella viruses dissemination to ganglia and skin.

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SVV infection of T cells increases the expression of cell cycle genes.

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SVV infection downregulates genes important for antigen presentation in T cells.

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SVV T cell infection disrupts expression of genes vital for metabolism and immunity.

Varicella zoster virus (VZV) causes varicella (chickenpox) during acute infection. Several studies have shown that T cells are early and preferential targets of VZV infection that play a critical role in disseminating VZV in to the skin and ganglia. However, the transcriptional changes that occur in VZV-infected T cells remain unclear due to limited access to clinical samples and robust translational animal models. In this study, we used a nonhuman primate model of VZV infection where rhesus macaques are infected with the closely related Simian Varicella Virus (SVV) to provide novel insights into VZV-T cell interactions. RNA sequencing of bronchial alveolar lavage-resident T cells isolated from infected rhesus macaques show that SVV infection alters expression of genes important for regulation of gene expression, cell cycle progression, metabolism, and antiviral immunity. These data provide insight into cellular processes that may support viral replication, facilitate SVV dissemination, and evade host defense.

Varicella zoster virus glycoprotein C increases chemokine-mediated leukocyte migration

Varicella zoster virus (VZV) is a highly prevalent human pathogen that establishes latency in neurons of the peripheral nervous system. Primary infection causes varicella whereas reactivation results in zoster, which is often followed by chronic pain in adults. Following infection of epithelial cells in the respiratory tract, VZV spreads within the host by hijacking leukocytes, including T cells, in the tonsils and other regional lymph nodes, and modifying their activity. In spite of its importance in pathogenesis, the mechanism of dissemination remains poorly understood. Here we addressed the influence of VZV on leukocyte migration and found that the purified recombinant soluble ectodomain of VZV glycoprotein C (rSgC) binds chemokines with high affinity. Functional experiments show that VZV rSgC potentiates chemokine activity, enhancing the migration of monocyte and T cell lines and, most importantly, human tonsillar leukocytes at low chemokine concentrations. Binding and potentiation of chemokine activity occurs through the C-terminal part of gC ectodomain, containing predicted immunoglobulin-like domains. The mechanism of action of VZV rSgC requires interaction with the chemokine and signalling through the chemokine receptor. Finally, we show that VZV viral particles enhance chemokine-dependent T cell migration and that gC is partially required for this activity. We propose that VZV gC activity facilitates the recruitment and subsequent infection of leukocytes and thereby enhances VZV systemic dissemination in humans.

Varicella zoster virus (VZV) causes two main pathologies in humans, chickenpox during primary infection, and shingles following reactivation. The latter is a painful condition that is often followed by chronic pain in a large numbers of shingles patients. Despite the existence of a vaccine, shingles-related complications cause expenses of more than $1 billion per year in the USA alone. Following primary infection, the virus infects leukocytes including T cells, spreading to the skin causing chickenpox. Direct infection of neurons from leukocytes has also been postulated. Given the relevance of leukocytes in VZV biology and the importance of chemokines in directing their migration, we investigated whether VZV modulates the function of chemokines. Our results show that VZV glycoprotein C potentiates the activity of chemokines, inducing higher migration of human leukocytes at low chemokine concentration. This may attract additional susceptible leukocytes to the site of infection enhancing virus spread and pathogenesis.

Risk Factors for Aseptic Meningitis in Herpes Zoster Patients

Background

Herpes zoster (HZ) is caused by reactivation of latent varicella-zoster virus (VZV) infection. HZ-associated aseptic meningitis, a rare complication of HZ, can require hospitalization and a long treatment period.

Objective

A retrospective study was performed to identify potential factors associated with HZ-associated aseptic meningitis development.

Methods

We included all outpatients and patients admitted in the neurology and dermatology departments of a single tertiary center, who were diagnosed with HZ for two years. Among 818 patients, 578 patients were eligible for analysis.

Results

The demographics and potential risk factors were compared between the uncomplicated HZ group (n=554) and aseptic meningitis group (n=24). Among the potential factors, the dermatological distribution of skin rash and gender showed statistically significantly different between the two groups. Patients with craniocervical distribution of HZ accounted for 87.5% (n=21) of the aseptic meningitis group and 54.3% (n=301) of the uncomplicated HZ group (p=0.043). The aseptic meningitis group had more men (66.7%, n=16) than the uncomplicated HZ group (42.8%, n=237, p=0.033). Patients with craniocervical distribution had an odds ratio (OR) of 5.884 (p=0.001) for developing aseptic meningitis when compared with the other dermatome involvements. Additional logistic regression analysis resulted in a fading between gender difference (p=0.050) and craniocervical involvement having an OR of 5.667 for aseptic meningitis (p=0.006).

Conclusion

In HZ patients, skin rash with craniocervical distribution and male gender were associated with a higher risk of aseptic meningitis.

Herpes zoster and the search for an effective vaccine

Primary infection with varicella zoster virus (VZV), an exclusively human neurotrophic alphaherpsesvirus, results in varicella, known more commonly as chickenpox. Like other alphaherpesviruses, VZV establishes latency in the sensory ganglia and can reactivate to cause herpes zoster (also known as shingles), a painful and debilitating disease, especially in elderly and immunocompromised individuals. The overall incidence of herpes zoster in Europe and the United States is three per 1000 people, but increases sharply after 60 years of age to 10 per 1000 people. Zostavax® is a vaccine approved by the Federal Drug Administration for the prevention of herpes zoster. Unfortunately, this vaccine reduces the incidence of disease by only 51% and the incidence of post-herpetic neuralgia by 66·5% when administered to those aged 60 and older. Moreover, it is contraindicated for individuals who are immunocompromised or receiving immunosuppressant treatments, although they are at higher risk for herpes zoster compared to immune-competent older individuals. This paper reviews VZV pathogenesis, host responses and current vaccines available to prevent herpes zoster.

Acute Simian Varicella Virus Infection Causes Robust and Sustained Changes in Gene Expression in the Sensory Ganglia

Primary infection with varicella-zoster virus (VZV), a neurotropic alphaherpesvirus, results in varicella. VZV establishes latency in the sensory ganglia and can reactivate later in life to cause herpes zoster. The relationship between VZV and its host during acute infection in the sensory ganglia is not well understood due to limited access to clinical specimens. Intrabronchial inoculation of rhesus macaques with simian varicella virus (SVV) recapitulates the hallmarks of VZV infection in humans. We leveraged this animal model to characterize the host-pathogen interactions in the ganglia during both acute and latent infection by measuring both viral and host transcriptomes on days postinfection (dpi) 3, 7, 10, 14, and 100. SVV DNA and transcripts were detected in sensory ganglia 3 dpi, before the appearance of rash. CD4 and CD8 T cells were also detected in the sensory ganglia 3 dpi. Moreover, lung-resident T cells isolated from the same animals 3 dpi also harbored SVV DNA and transcripts, suggesting that T cells may be responsible for trafficking SVV to the ganglia. Transcriptome sequencing (RNA-Seq) analysis showed that cessation of viral transcription 7 dpi coincides with a robust antiviral innate immune response in the ganglia. Interestingly, a significant number of genes that play a critical role in nervous system development and function remained downregulated into latency. These studies provide novel insights into host-pathogen interactions in the sensory ganglia during acute varicella and demonstrate that SVV infection results in profound and sustained changes in neuronal gene expression.

IMPORTANCE

Many aspects of VZV infection of sensory ganglia remain poorly understood, due to limited access to human specimens and the fact that VZV is strictly a human virus. Infection of rhesus macaques with simian varicella virus (SVV), a homolog of VZV, provides a robust model of the human disease. Using this model, we show that SVV reaches the ganglia early after infection, most likely by T cells, and that the induction of a robust innate immune response correlates with cessation of virus transcription. We also report significant changes in the expression of genes that play an important role in neuronal function. Importantly, these changes persist long after viral replication ceases. Given the homology between SVV and VZV, and the genetic and physiological similarities between rhesus macaques and humans, our results provide novel insight into the interactions between VZV and its human host and explain some of the neurological consequences of VZV infection.

Risk Factors for Herpes Zoster Among Adults

Background. The causes of varicella-zoster virus reactivation and herpes zoster (HZ) are largely unknown. We assessed potential risk factors for HZ, the data for which cannot be obtained from the medical sector.

Methods. We conducted a matched case-control study. We established active surveillance in Olmsted County, Minnesota to identify HZ occurring among persons age ≥50 years during 2010–2011. Cases were confirmed by medical record review. Herpes zoster-free controls were age- and sex-matched to cases. Risk factor data were obtained by telephone interview.

Results. We enrolled 389 HZ case patients and 511 matched controls; the median age was 65 and 66 years, respectively. Herpes zoster was associated with family history of HZ (adjusted odds ratio [aOR] = 1.65); association was highest with first-degree or multiple relatives (aOR = 1.87 and 3.08, respectively). Herpes zoster was also associated with prior HZ episodes (aOR = 1.82), sleep disturbance (aOR = 2.52), depression (aOR = 3.81), and recent weight loss (aOR = 1.95). Stress was a risk factor for HZ (aOR = 2.80), whereas a dose-response relationship was not noted. All associations indicated were statistically significant (P < .05). Herpes zoster was not associated with trauma, smoking, tonsillectomy, diet, or reported exposure to pesticides or herbicides (P > .1).

Conclusions. We identified several important risk factors for HZ; however, the key attributable causes of HZ remain unknown.

Type I interferon inhibits varicella-zoster virus replication by interfering with the dynamic interaction between mediator and IE62 within replication compartments

Background

Varicella-zoster virus (VZV) is the causative agent of varicella and zoster. The immediate-early protein, IE62 is the predominant VZ virion tegument protein, transactivating the expression of all kinetic classes of VZV genes. IE62 is localized to punctae that form DNA replication compartments in the nuclei of VZV infected cells. The morphological changes and the increase in the size of replication compartments that express IE62 are correlated with production of VZ virions. Mammalian Mediator serves as a coactivator of IE62 and functions by bridging DNA-binding transcription factors¸ RNA polymerase II (RNAP II) and their target DNAs for VZV replication. While VZV is highly sensitive to type I interferons (IFNs), how IFN-α inhibits early events during VZV replication is poorly understood.

Results

In this study, we performed in situ analysis to investigate the effects of IFN-α on the dynamic interactions of IE62 with the Mediator MED25 subunit and the RNAP II negative regulator cycle-dependent kinase 8 (CDK8) in VZV infected cells by confocal immunofluorescence. We found that in addition to dose-dependent inhibition of the yields of infectious virus by IFN treatment, IFN-α prominently impeded the development of large IE62⁺ nuclear compartments and significantly decreased transcription of VZV genes. Both the expression level and stable recruitment of MED25 to IE62⁺ replication compartments were inhibited by IFN-α. While IFN-α treatment upregulated CDK8 expression, redistribution and recruitment of CDK8 to IE62⁺ replication compartments in infected cells was not affected by VZV.

Conclusion

IFN-α exerts multiple inhibitory activities against virus infections. In this study, we provide visionary demonstration that continuous translocation of MED25 into VZV replication compartments ensures production of virions. IFN-α greatly impedes the formation of a stable complex between IE62 and the Mediator complex thereby suppresses VZV gene transcription. Our demonstration that IFN-α-induced antiviral effect against VZV infection is through inhibiting the reorganization of nuclear components uncovers a novel function of IFN-α. Targeting the interaction between IE62 and MED25 may offer a novel approach to the development of antiviral agents against VZV infection.

Modulation of host CD59 expression by varicella-zoster virus in human xenografts in vivo

Varicella-zoster virus (VZV) is the causative agent of both chickenpox (varicella) and shingles (zoster). VZV survives host defenses, even with an intact immune system, and disseminates in the host before causing disease. To date, several diverse immunomodulatory strategies used by VZV to undermine host immunity have been identified; however, few studies have addressed the complement evasion strategies used by this virus. Here, we show that expression of CD59, which is a key member of host regulators of complement activation (RCA), is significantly upregulated in response to VZV infection in human T cells and dorsal root ganglia (DRG) but not in human skin xenografts in SCID-hu mice in vivo. This is the first report demonstrating that VZV infection upregulates host CD59 expression in a tissue-specific manner in vivo, which may aid VZV in complement evasion and pathogenesis.

Dissecting the Molecular Mechanisms of the Tropism of Varicella-Zoster Virus for Human T Cells

Studies of varicella-zoster virus (VZV) tropism for T cells support their role in viral transport to the skin during primary infection. Multiparametric single-cell mass cytometry demonstrates that, instead of preferentially infecting skin-homing T cells, VZV alters cell signaling and remodels surface proteins to enhance T cell skin trafficking. Viral proteins dispensable in skin, such as that encoded by open reading frame 66, are necessary in T cells. Interference with VZV T cell tropism may offer novel strategies for drug and vaccine design.

Single cell mass cytometry reveals remodeling of human T cell phenotypes by varicella zoster virus

The recent application of mass cytometry (CyTOF) to biology provides a 'systems' approach to monitor concurrent changes in multiple host cell factors at the single cell level. We used CyTOF to evaluate T cells infected with varicella zoster virus (VZV) infection, documenting virus-mediated phenotypic and functional changes caused by this T cell tropic human herpesvirus. Here we summarize our findings using two complementary panels of antibodies against surface and intracellular signaling proteins to elucidate the consequences of VZV-mediated perturbations on the surface and in signaling networks of infected T cells. CyTOF data was analyzed by several statistical, analytical and visualization tools including hierarchical clustering, orthogonal scaling, SPADE, viSNE, and SLIDE. Data from the mass cytometry studies demonstrated that VZV infection led to 'remodeling' of the surface architecture of T cells, promoting skin trafficking phenotypes and associated with concomitant activation of T-cell receptor and PI3-kinase pathways. This method offers a novel approach for understanding viral interactions with differentiated host cells important for pathogenesis.

Varicella zoster virus infection

Infection with varicella zoster virus (VZV) causes varicella (chickenpox), which can be severe in immunocompromised individuals, infants and adults. Primary infection is followed by latency in ganglionic neurons. During this period, no virus particles are produced and no obvious neuronal damage occurs. Reactivation of the virus leads to virus replication, which causes zoster (shingles) in tissues innervated by the involved neurons, inflammation and cell death - a process that can lead to persistent radicular pain (postherpetic neuralgia). The pathogenesis of postherpetic neuralgia is unknown and it is difficult to treat. Furthermore, other zoster complications can develop, including myelitis, cranial nerve palsies, meningitis, stroke (vasculopathy), retinitis, and gastroenterological infections such as ulcers, pancreatitis and hepatitis. VZV is the only human herpesvirus for which highly effective vaccines are available. After varicella or vaccination, both wild-type and vaccine-type VZV establish latency, and long-term immunity to varicella develops. However, immunity does not protect against reactivation. Thus, two vaccines are used: one to prevent varicella and one to prevent zoster. In this Primer we discuss the pathogenesis, diagnosis, treatment, and prevention of VZV infections, with an emphasis on the molecular events that regulate these diseases. For an illustrated summary of this Primer, visit: http://go.nature.com/14xVI1.

Differential expression of Marek's disease virus (MDV) late proteins during in vitro and in situ replication: role for pUL47 in regulation of the MDV UL46-UL49 gene locus

Marek's disease virus (MDV) is a lymphotropic alphaherpesvirus that replicates in a highly cell-associated manner in vitro. Production of infectious cell-free virus only occurs in feather follicle epithelial (FFE) cells of infected chicken skins. Previously, we described differential expression for a core alphaherpesvirus protein, pUL47 that was found to be abundantly expressed in FFE cells of infected chickens, while barely detectable during in vitro propagation. Here, we further examined the dynamics of expression of four tegument proteins within the UL46-49 locus during in vitro and in situ replication. All four proteins examined were expressed abundantly in situ, whereas both pUL47 and pUL48 expression were barely detectable in vitro. Replacement of the putative UL47 and UL48 promoters with the minimal cytomegalovirus promoter enhanced mRNA and protein expression in vitro. Interestingly, enhanced expression of pUL47 resulted in increased UL46, UL48, and UL49 transcripts that resulted in increased pUL46 and pUL48 expression.

Pathogenesis of varicelloviruses in primates

Varicelloviruses in primates comprise the prototypic human varicella-zoster virus (VZV) and its non-human primate homologue, simian varicella virus (SVV). Both viruses cause varicella as a primary infection, establish latency in ganglionic neurons and reactivate later in life to cause herpes zoster in their respective hosts. VZV is endemic worldwide and, although varicella is usually a benign disease in childhood, VZV reactivation is a significant cause of neurological disease in the elderly and in immunocompromised individuals. The pathogenesis of VZV infection remains ill-defined, mostly due to the species restriction of VZV that impedes studies in experimental animal models. SVV infection of non-human primates parallels virological, clinical, pathological and immunological features of human VZV infection, thereby providing an excellent model to study the pathogenesis of varicella and herpes zoster in its natural host. In this review, we discuss recent studies that provided novel insight in both the virus and host factors involved in the three elementary stages of Varicellovirus infection in primates: primary infection, latency and reactivation.

Abortive intrabronchial infection of rhesus macaques with varicella-zoster virus provides partial protection against simian varicella virus challenge

Varicella-zoster virus (VZV) is a human neurotropic alphaherpesvirus and the etiological agent of varicella (chickenpox) and herpes zoster (HZ, shingles). Previously, inoculation of monkeys via the subcutaneous, intratracheal, intravenous, or oral-nasal-conjunctival routes did not recapitulate all the hallmarks of VZV infection, including varicella, immunity, latency, and reactivation. Intrabronchial inoculation of rhesus macaques (RMs) with simian varicella virus (SVV), a homolog of VZV, recapitulates virologic and immunologic hallmarks of VZV infection in humans. Given that VZV is acquired primarily via the respiratory route, we investigated whether intrabronchial inoculation of RMs with VZV would result in a robust model. Despite the lack of varicella and viral replication in either the lungs or whole blood, all four RMs generated an immune response characterized by the generation of VZV-specific antibodies and T cells. Two of 4 VZV-inoculated RMs were challenged with SVV to determine cross-protection. VZV-immune RMs displayed no varicella rash and had lower SVV viral loads and earlier and stronger humoral and cellular immune responses than controls. In contrast to the results for SVV DNA, no VZV DNA was detected in sensory ganglia at necropsy. In summary, following an abortive VZV infection, RMs developed an adaptive immune response that conferred partial protection against SVV challenge. These data suggest that a replication-incompetent VZV vaccine that does not establish latency may provide sufficient protection against VZV disease and that VZV vaccination of RMs followed by SVV challenge provides a model to evaluate new vaccines and therapeutics against VZV.

IMPORTANCE

Although VZV vaccine strain Oka is attenuated, it can cause mild varicella, establish latency, and in rare cases, reactivate to cause herpes zoster (HZ). Moreover, studies suggest that the HZ vaccine (Zostavax) only confers short-lived immunity. The development of more efficacious vaccines would be facilitated by a robust animal model of VZV infection. The data presented in this report show that intrabronchial inoculation of rhesus macaques (RMs) with VZV resulted in an abortive VZV infection. Nevertheless, all animals generated a humoral and cellular immune response that conferred partial cross-protection against simian varicella virus (SVV) challenge. Additionally, VZV DNA was not detected in the sensory ganglia, suggesting that viremia might be required for the establishment of latency. Therefore, VZV vaccination of RMs followed by SVV challenge is a model that will support the development of vaccines that boost protective T cell responses against VZV.

Intrabronchial infection of rhesus macaques with simian varicella virus results in a robust immune response in the lungs

Varicella-zoster virus (VZV) is the etiological agent of varicella (chickenpox) and herpes zoster (shingles). Primary VZV infection is believed to occur via the inhalation of virus either in respiratory droplets or from shedding varicella lesions or by direct contact with infectious vesicular fluid. However, the ensuing immune response in the lungs remains incompletely understood. We have shown that intrabronchial inoculation of rhesus macaques with simian varicella virus (SVV), a homolog of VZV, recapitulates the hallmarks of acute and latent VZV infection in humans. In this study, we performed an in-depth analysis of the host immune response to acute SVV infection in the lungs and peripheral blood. We report that acute SVV infection results in a robust innate immune response in the lungs, characterized by the production of inflammatory cytokines, chemokines, and growth factors as well as an increased frequency of plasmacytoid dendritic cells (DCs) that corresponded with alpha interferon (IFN-α) production and a rapid decrease in viral loads in the lungs. This is followed by T and B cell proliferation, antibody production, T cell differentiation, and cytokine production, which correlate with the complete cessation of viral replication. Although terminally differentiated CD8 T cells became the predominant T cell population in bronchoalveolar lavage cells, a higher percentage of CD4 T cells were SVV specific, which suggests a critical role for these cells in the resolution of primary SVV infection in the lungs. Given the homology between SVV and VZV, our data provide insight into the immune response to VZV within the lung.

IMPORTANCE

Although primary VZV infection occurs primarily via the respiratory route, the host response in the lungs and its contribution to the cessation of viral replication and establishment of latency remain poorly understood. The difficulty in accessing lung tissue and washes from individuals infected with VZV has hampered efforts to address this knowledge gap. SVV infection of rhesus macaques is an important model of VZV infection of humans; therefore, we utilized this animal model to gain a comprehensive view of the kinetics of the immune response to SVV in the lung and its relationship to the resolution of acute infection in respiratory tissues. These data not only advance our understanding of host immunity to VZV, a critical step in developing new vaccines, but also provide additional insight into immunity to respiratory pathogens.

Single-cell mass cytometry analysis of human tonsil T cell remodeling by varicella zoster virus

Although pathogens must infect differentiated host cells that exhibit substantial diversity, documenting the consequences of infection against this heterogeneity is challenging. Single-cell mass cytometry permits deep profiling based on combinatorial expression of surface and intracellular proteins. We used this method to investigate varicella-zoster virus (VZV) infection of tonsil T cells, which mediate viral transport to skin. Our results indicate that VZV induces a continuum of changes regardless of basal phenotypic and functional T cell characteristics. Contrary to the premise that VZV selectively infects T cells with skin trafficking profiles, VZV infection altered T cell surface proteins to enhance or induce these properties. Zap70 and Akt signaling pathways that trigger such surface changes were activated in VZV-infected naive and memory cells by a T cell receptor (TCR)-independent process. Single-cell mass cytometry is likely to be broadly relevant for demonstrating how intracellular pathogens modulate differentiated cells to support pathogenesis in the natural host.

The cytoplasmic domain of varicella-zoster virus glycoprotein H regulates syncytia formation and skin pathogenesis

The conserved herpesvirus fusion complex consists of glycoproteins gB, gH, and gL which is critical for virion envelope fusion with the cell membrane during entry. For Varicella Zoster Virus (VZV), the complex is necessary for cell-cell fusion and presumed to mediate entry. VZV causes syncytia formation via cell-cell fusion in skin and in sensory ganglia during VZV reactivation, leading to neuronal damage, a potential contributory factor for the debilitating condition of postherpetic neuralgia. The gH cytoplasmic domain (gHcyt) is linked to the regulation of gB/gH-gL-mediated cell fusion as demonstrated by increased cell fusion in vitro by an eight amino acid (aa834-841) truncation of the gHcyt. The gHcyt regulation was identified to be dependent on the physical presence of the domain, and not of specific motifs or biochemical properties as substitution of aa834-841 with V5, cMyc, and hydrophobic or hydrophilic sequences did not affect fusion. The importance of the gHcyt length was corroborated by stepwise deletions of aa834-841 causing incremental increases in cell fusion, independent of gH surface expression and endocytosis. Consistent with the fusion assay, truncating the gHcyt in the viral genome caused exaggerated syncytia formation and significant reduction in viral titers. Importantly, infection of human skin xenografts in SCID mice was severely impaired by the truncation while maintaining the gHcyt length with the V5 substitution preserved typical replication in vitro and in skin. A role for the gHcyt in modulating the functions of the gB cytoplasmic domain (gBcyt) is proposed as the gHcyt truncation substantially enhanced cell fusion in the presence of the gB[Y881F] mutation. The significant reduction in skin infection caused by hyperfusogenic mutations in either the gHcyt or gBcyt demonstrates that both domains are critical for regulating syncytia formation and failure to control cell fusion, rather than enhancing viral spread, is severely detrimental to VZV pathogenesis.

Varicella zoster virus (VZV) infects the human population globally, causing chickenpox in children and shingles in adults. While those afflicted with shingles experience severe pain that might last from weeks to months, the cause is not known. Biopsies of VZV infected skin and specimens of nerve ganglia collected at autopsy from patients with shingles at the time of death contain multi-nucleated cells, indicating that the virus is able to cause fusion between infected cells. Since the destruction of nerve cells that results from this process is likely to contribute to the pain associated with shingles, it is important to understand how the virus causes infected cells to fuse. We find that VZV cell-cell fusion is regulated by the intracellular facing domain of glycoprotein H (gH), a viral protein present on the surface of infected cells. This regulation was dependent upon the physical length of the domain, not a specific sequence. Loss of this regulation increased cell-cell fusion causing the formation of larger multi-nucleated cells that limited the ability of the virus to effectively spread in human skin. Our study provides new insight into how VZV manipulates host cells during infection and controls the spread of the virus in tissues.

Clinical and molecular aspects of the live attenuated Oka varicella vaccine

VZV is a ubiquitous member of the Herpesviridae family that causes varicella (chicken pox) and herpes zoster (shingles). Both manifestations can cause great morbidity and mortality and are therefore of significant economic burden. The introduction of varicella vaccination as part of childhood immunization programs has resulted in a remarkable decline in varicella incidence, and associated hospitalizations and deaths, particularly in the USA. The vaccine preparation, vOka, is a live attenuated virus produced by serial passage of a wild-type clinical isolate termed pOka in human and guinea pig cell lines. Although vOka is clinically attenuated, it can cause mild varicella, establish latency, and reactivate to cause herpes zoster. Sequence analysis has shown that vOka differs from pOka by at least 42 loci; however, not all genomes possess the novel vOka change at all positions, creating a heterogeneous population of genetically distinct haplotypes. This, together with the extreme cell-associated nature of VZV replication in cell culture and the lack of an animal model, in which the complete VZV life cycle can be replicated, has limited studies into the molecular basis for vOka attenuation. Comparative studies of vOka with pOka replication in T cells, dorsal root ganglia, and skin indicate that attenuation likely involves multiple mutations within ORF 62 and several other genes. This article presents an overview of the clinical aspects of the vaccine and current progress on understanding the molecular mechanisms that account for the clinical phenotype of reduced virulence.