Immunohistochemical detection of intra-neuronal VZV proteins in snap-frozen human ganglia is confounded by antibodies directed against blood group A1-associated antigens

Varicella-zoster virus proteome-wide T-cell screening demonstrates low prevalence of virus-specific CD8 T-cells in latently infected human trigeminal ganglia

BACKGROUND

Trigeminal ganglia (TG) neurons are an important site of lifelong latent varicella-zoster virus (VZV) infection. Although VZV-specific T-cells are considered pivotal to control virus reactivation, their protective role at the site of latency remains uncharacterized.

METHODS

Paired blood and TG specimens were obtained from ten latent VZV-infected adults, of which nine were co-infected with herpes simplex virus type 1 (HSV-1). Short-term TG-derived T-cell lines (TG-TCL), generated by mitogenic stimulation of TG-derived T-cells, were probed for HSV-1- and VZV-specific T-cells using flow cytometry. We also performed VZV proteome-wide screening of TG-TCL to determine the fine antigenic specificity of VZV reactive T-cells. Finally, the relationship between T-cells and latent HSV-1 and VZV infections in TG was analyzed by reverse transcription quantitative PCR (RT-qPCR) and in situ analysis for T-cell proteins and latent viral transcripts.

RESULTS

VZV proteome-wide analysis of ten TG-TCL identified two VZV antigens recognized by CD8 T-cells in two separate subjects. The first was an HSV-1/VZV cross-reactive CD8 T-cell epitope, whereas the second TG harbored CD8 T-cells reactive with VZV specifically and not the homologous peptide in HSV-1. In silico analysis showed that HSV-1/VZV cross reactivity of TG-derived CD8 T-cells reactive with ten previously identified HSV-1 epitopes was unlikely, suggesting that HSV-1/VZV cross-reactive T-cells are not a common feature in dually infected TG. Finally, no association was detected between T-cell infiltration and VZV latency transcript abundance in TG by RT-qPCR or in situ analyses.

CONCLUSIONS

The low presence of VZV- compared to HSV-1-specific CD8 T-cells in human TG suggests that VZV reactive CD8 T-cells play a limited role in maintaining VZV latency.

Selective retention of virus-specific tissue-resident T cells in healed skin after recovery from herpes zoster

Herpes zoster is a localized skin infection caused by reactivation of latent varicella-zoster virus. Tissue-resident T cells likely control skin infections. Zoster provides a unique opportunity to determine if focal reinfection of human skin boosts local or disseminated antigen-specific tissue-resident T cells. Here, we show virus-specific T cells are retained over one year in serial samples of rash site and contralateral unaffected skin of individuals recovered from zoster. Consistent with zoster resolution, viral DNA is largely undetectable on skin from day 90 and virus-specific B and T cells decline in blood. In skin, there is selective infiltration and long-term persistence of varicella-zoster virus-specific T cells in the rash site relative to the contralateral site. The skin T cell infiltrates express the canonical tissue-resident T cell markers CD69 and CD103. These findings show that zoster promotes spatially-restricted long-term retention of antigen-specific tissue-resident T cells in previously infected skin.

A Guide to Preclinical Models of Zoster-Associated Pain and Postherpetic Neuralgia

Reactivation of latent varicella-zoster virus (VZV) causes herpes zoster (HZ), which is commonly accompanied by acute pain and pruritus over the time course of a zosteriform rash. Although the rash and associated pain are self-limiting, a considerable fraction of HZ cases will subsequently develop debilitating chronic pain states termed postherpetic neuralgia (PHN). How VZV causes acute pain and the mechanisms underlying the transition to PHN are far from clear. The human-specific nature of VZV has made in vivo modeling of pain following reactivation difficult to study because no single animal can reproduce reactivated VZV disease as observed in the clinic. Investigations of VZV pathogenesis following primary infection have benefited greatly from human tissues harbored in immune-deficient mice, but modeling of acute and chronic pain requires an intact nervous system with the capability of transmitting ascending and descending sensory signals. Several groups have found that subcutaneous VZV inoculation of the rat induces prolonged and measurable changes in nociceptive behavior, indicating sensitivity that partially mimics the development of mechanical allodynia and thermal hyperalgesia seen in HZ and PHN patients. Although it is not a model of reactivation, the rat is beginning to inform how VZV infection can evoke a pain response and induce long-lasting alterations to nociception. In this review, we will summarize the rat pain models from a practical perspective and discuss avenues that have opened for testing of novel treatments for both zoster-associated pain and chronic PHN conditions, which remain in critical need of effective therapies.

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.

No Evidence of Varicella-Zoster Virus Infection in Temporal Artery Biopsies of Anterior Ischemic Optic Neuropathy Patients With and Without Giant Cell Arteritis

Background

To test the hypothesis that varicella-zoster virus (VZV) infection contributes to temporal arteritis pathogenesis, comprehensive in situ analysis was performed on temporal artery biopsies of 38 anterior ischemic optic neuropathy (AION) patients, including 14 (37%) with giant cell arteritis.

Methods

Biopsies were completely sectioned, and, on average, 146 serial sections per patient were stained for VZV glycoprotein E.

Results

Four of 38 AION patients showed VZV glycoprotein E staining, but VZV infection was not confirmed by staining for VZV IE63 protein and VZV-specific polymerase chain reaction on adjacent sections.

Conclusions

This study refutes the premise that VZV is casually related to AION with and without giant cell arteritis.

Varicella-zoster virus VLT-ORF63 fusion transcript induces broad viral gene expression during reactivation from neuronal latency

Varicella-zoster virus (VZV) establishes lifelong neuronal latency in most humans world-wide, reactivating in one-third to cause herpes zoster and occasionally chronic pain. How VZV establishes, maintains and reactivates from latency is largely unknown. VZV transcription during latency is restricted to the latency-associated transcript (VLT) and RNA 63 (encoding ORF63) in naturally VZV-infected human trigeminal ganglia (TG). While significantly more abundant, VLT levels positively correlated with RNA 63 suggesting co-regulated transcription during latency. Here, we identify VLT-ORF63 fusion transcripts and confirm VLT-ORF63, but not RNA 63, expression in human TG neurons. During in vitro latency, VLT is transcribed, whereas VLT-ORF63 expression is induced by reactivation stimuli. One isoform of VLT-ORF63, encoding a fusion protein combining VLT and ORF63 proteins, induces broad viral gene transcription. Collectively, our findings show that VZV expresses a unique set of VLT-ORF63 transcripts, potentially involved in the transition from latency to lytic VZV infection.

Current In Vivo Models of Varicella-Zoster Virus Neurotropism

Varicella-zoster virus (VZV), an exclusively human herpesvirus, causes chickenpox and establishes a latent infection in ganglia, reactivating decades later to produce zoster and associated neurological complications. An understanding of VZV neurotropism in humans has long been hampered by the lack of an adequate animal model. For example, experimental inoculation of VZV in small animals including guinea pigs and cotton rats results in the infection of ganglia but not a rash. The severe combined immune deficient human (SCID-hu) model allows the study of VZV neurotropism for human neural sub-populations. Simian varicella virus (SVV) infection of rhesus macaques (RM) closely resembles both human primary VZV infection and reactivation, with analyses at early times after infection providing valuable information about the extent of viral replication and the host immune responses. Indeed, a critical role for CD4 T-cell immunity during acute SVV infection as well as reactivation has emerged based on studies using RM. Herein we discuss the results of efforts from different groups to establish an animal model of VZV neurotropism.

Current In Vitro Models to Study Varicella Zoster Virus Latency and Reactivation

Varicella zoster virus (VZV) is a highly prevalent human pathogen that causes varicella (chicken pox) during primary infection and establishes latency in peripheral neurons. Symptomatic reactivation often presents as zoster (shingles), but it has also been linked to life-threatening diseases such as encephalitis, vasculopathy and meningitis. Zoster may be followed by postherpetic neuralgia, neuropathic pain lasting after resolution of the rash. The mechanisms of varicella zoster virus (VZV) latency and reactivation are not well characterized. This is in part due to the human-specific nature of VZV that precludes the use of most animal and animal-derived neuronal models. Recently, in vitro models of VZV latency and reactivation using human neurons derived from stem cells have been established facilitating an understanding of the mechanisms leading to VZV latency and reactivation. From the models, c-Jun N-terminal kinase (JNK), phosphoinositide 3-kinase (PI3K) and nerve growth factor (NGF) have all been implicated as potential modulators of VZV latency/reactivation. Additionally, it was shown that the vaccine-strain of VZV is impaired for reactivation. These models may also aid in the generation of prophylactic and therapeutic strategies to treat VZV-associated pathologies. This review summarizes and analyzes the current human neuronal models used to study VZV latency and reactivation, and provides some strategies for their improvement.

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.

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.

A spliced latency-associated VZV transcript maps antisense to the viral transactivator gene 61

Varicella-zoster virus (VZV), an alphaherpesvirus, establishes lifelong latent infection in the neurons of >90% humans worldwide, reactivating in one-third to cause shingles, debilitating pain and stroke. How VZV maintains latency remains unclear. Here, using ultra-deep virus-enriched RNA sequencing of latently infected human trigeminal ganglia (TG), we demonstrate the consistent expression of a spliced VZV mRNA, antisense to VZV open reading frame 61 (ORF61). The spliced VZV latency-associated transcript (VLT) is expressed in human TG neurons and encodes a protein with late kinetics in productively infected cells in vitro and in shingles skin lesions. Whereas multiple alternatively spliced VLT isoforms (VLT_ly) are expressed during lytic infection, a single unique VLT isoform, which specifically suppresses ORF61 gene expression in co-transfected cells, predominates in latently VZV-infected human TG. The discovery of VLT links VZV with the other better characterized human and animal neurotropic alphaherpesviruses and provides insights into VZV latency.

Varicella-zoster virus (VZV) establishes lifelong infection in the majority of the population, but mechanisms underlying latency remain unclear. Here, the authors use ultra-deep RNA sequencing, enriched for viral RNAs, of latently infected human trigeminal ganglia and identify a spliced, latency-associated VZV mRNA.

Vaccine Development for Varicella-Zoster Virus

Varicella-zoster virus (VZV) is the first and only human herpesvirus for which a licensed live attenuated vaccine, vOka, has been developed. vOka has highly safe and effective profiles; however, worldwide herd immunity against VZV has not yet been established and it is far from eradication. Despite the successful reduction in the burden of VZV-related illness by the introduction of the vaccine, some concerns about vOka critically prevent worldwide acceptance and establishment of herd immunity, and difficulties in addressing these criticisms often relate to its ill-defined mechanism of attenuation. Advances in scientific technologies have been applied in the VZV research field and have contributed toward uncovering the mechanism of vOka attenuation as well as VZV biology at the molecular level. A subunit vaccine targeting single VZV glycoprotein, rationally designed based on the virological and immunological research, has great potential to improve the strategy for eradication of VZV infection in combination with vOka.

Patterns of BAP1 protein expression provide insights into prognostic significance and the biology of uveal melanoma

Uveal melanoma (UM) is a rare aggressive intraocular tumour with a propensity for liver metastases, occurring in ∼50% of patients. The tumour suppressor BAP1 is considered to be key in UM progression. Herein, we present the largest study to date investigating cellular expression patterns of BAP1 protein in 165 UMs, correlating these patterns to prognosis. Full clinical, histological, genetic, and follow‐up data were available for all patients. BAP1 gene sequencing was performed on a subset of 26 cases. An independent cohort of 14 UMs was examined for comparison. Loss of nuclear BAP1 (nBAP1) protein expression was observed in 54% (88/165) UMs. nBAP1 expression proved to be a significant independent prognostic parameter: it identified two subgroups within monosomy 3 (M3) UM, which are known to have a high risk of metastasis. Strikingly, nBAP1‐positiveM3 UMs were associated with prolonged survival compared to nBAP1‐negative M3 UMs (Log rank, p = 0.014). nBAP1 protein loss did not correlate with a BAP1 mutation in 23% (6/26) of the UMs analysed. Cytoplasmic BAP1 protein (cBAP1) expression was also observed in UM: although appearing ‘predominantly diffuse’ in most nBAP1‐negative UM, a distinct ‘focal perinuclear’ expression pattern – localized immediately adjacent to the cis Golgi – was seen in 31% (18/59). These tumours tended to carry loss‐of‐function BAP1 mutations. Our study demonstrates loss of nBAP1 expression to be the strongest prognostic marker in UM, confirming its importance in UM progression. Our data suggest that non‐genetic mechanisms account for nBAP1 loss in a small number of UMs. In addition, we describe a subset of nBAP1‐negative UM, in which BAP1 is sequestered in perinuclear bodies, most likely within Golgi, warranting further mechanistic investigation.

In vitro system using human neurons demonstrates that varicella-zoster vaccine virus is impaired for reactivation, but not latency

Varicella-zoster virus (VZV) establishes latency in human sensory and cranial nerve ganglia during primary infection (varicella), and the virus can reactivate and cause zoster after primary infection. The mechanism of how the virus establishes and maintains latency and how it reactivates is poorly understood, largely due to the lack of robust models. We found that axonal infection of neurons derived from hESCs in a microfluidic device with cell-free parental Oka (POka) VZV resulted in latent infection with inability to detect several viral mRNAs by reverse transcriptase-quantitative PCR, no production of infectious virus, and maintenance of the viral DNA genome in endless configuration, consistent with an episome configuration. With deep sequencing, however, multiple viral mRNAs were detected. Treatment of the latently infected neurons with Ab to NGF resulted in production of infectious virus in about 25% of the latently infected cultures. Axonal infection of neurons with vaccine Oka (VOka) VZV resulted in a latent infection similar to infection with POka; however, in contrast to POka, VOka-infected neurons were markedly impaired for reactivation after treatment with Ab to NGF. In addition, viral transcription was markedly reduced in neurons latently infected with VOka compared with POka. Our in vitro system recapitulates both VZV latency and reactivation in vivo and may be used to study viral vaccines for their ability to establish latency and reactivate.

Neuronal changes induced by Varicella Zoster Virus in a rat model of postherpetic neuralgia

A significant fraction of patients with herpes zoster, caused by Varicella Zoster Virus (VZV), experience chronic pain termed postherpetic neuralgia (PHN). VZV-inoculated rats develop prolonged nocifensive behaviors and serve as a model of PHN. We demonstrate that primary rat cultures show a post-entry block for VZV replication, suggesting the rat is not fully permissive. However, footpads of VZV infected animals show reduced peripheral innervation and innervating dorsal root ganglia (DRG) contained VZV DNA and transcripts of candidate immediate early and early genes. The VZV-infected DRG showed changes in host gene expression patterns, with 84 up-regulated and 116 down-regulated genes seen in gene array studies. qRT-PCR validated the modulation of nociception-associated genes Ntrk2, Trpv1, and Calca (CGRP). The data suggests that VZV inoculation of the rat results in a single round, incomplete infection that is sufficient to induce pain behaviors, and this involves infection of and changes induced in neuronal populations.

A comparison of herpes simplex virus type 1 and varicella-zoster virus latency and reactivation

Herpes simplex virus type 1 (HSV-1; human herpesvirus 1) and varicella-zoster virus (VZV; human herpesvirus 3) are human neurotropic alphaherpesviruses that cause lifelong infections in ganglia. Following primary infection and establishment of latency, HSV-1 reactivation typically results in herpes labialis (cold sores), but can occur frequently elsewhere on the body at the site of primary infection (e.g. whitlow), particularly at the genitals. Rarely, HSV-1 reactivation can cause encephalitis; however, a third of the cases of HSV-1 encephalitis are associated with HSV-1 primary infection. Primary VZV infection causes varicella (chickenpox) following which latent virus may reactivate decades later to produce herpes zoster (shingles), as well as an increasingly recognized number of subacute, acute and chronic neurological conditions. Following primary infection, both viruses establish a latent infection in neuronal cells in human peripheral ganglia. However, the detailed mechanisms of viral latency and reactivation have yet to be unravelled. In both cases latent viral DNA exists in an 'end-less' state where the ends of the virus genome are joined to form structures consistent with unit length episomes and concatemers, from which viral gene transcription is restricted. In latently infected ganglia, the most abundantly detected HSV-1 RNAs are the spliced products originating from the primary latency associated transcript (LAT). This primary LAT is an 8.3 kb unstable transcript from which two stable (1.5 and 2.0 kb) introns are spliced. Transcripts mapping to 12 VZV genes have been detected in human ganglia removed at autopsy; however, it is difficult to ascribe these as transcripts present during latent infection as early-stage virus reactivation may have transpired in the post-mortem time period in the ganglia. Nonetheless, low-level transcription of VZV ORF63 has been repeatedly detected in multiple ganglia removed as close to death as possible. There is increasing evidence that HSV-1 and VZV latency is epigenetically regulated. In vitro models that permit pathway analysis and identification of both epigenetic modulations and global transcriptional mechanisms of HSV-1 and VZV latency hold much promise for our future understanding in this complex area. This review summarizes the molecular biology of HSV-1 and VZV latency and reactivation, and also presents future directions for study.

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.

Presence of a neo-epitope and absence of amyloid beta and tau protein in degenerative hippocampal granules of aged mice

Clustered pathological granules related to a degenerative process appear and increase progressively with age in the hippocampus of numerous mouse strains. We describe herein the presence of a neo-epitope of carbohydrate nature in these granules, which is not present in other brain areas and thus constitutes a new marker of these degenerative structures. We also found that this epitope is recognised by a contaminant IgM present in several antibodies obtained from mouse ascites and from both mouse and rabbit sera. These findings entail the need to revise the high number of components that are thought to be present in the granules, such as the controversial β-amyloid peptides described in the granules of senescence-accelerated mouse prone-8 (SAMP8) mice. Characterisation of the composition of SAMP8 granules, taking into account the presence of the neo-epitope and the contaminant IgM, showed that granules do not contain either β-amyloid peptides or tau protein. The presence of the neo-epitope in the granules but not in other brain areas opens up a new direction in the study of the neurodegenerative processes associated with age. The SAMP8 strain, in which the progression of the granules is enhanced, may be a useful model for this purpose.

Pathogenesis and current approaches to control of varicella-zoster virus infections

Varicella-zoster virus (VZV) was once thought to be a fairly innocuous pathogen. That view is no longer tenable. The morbidity and mortality due to the primary and secondary diseases that VZV causes, varicella and herpes zoster (HZ), are significant. Fortunately, modern advances, including an available vaccine to prevent varicella, a therapeutic vaccine to diminish the incidence and ameliorate sequelae of HZ, effective antiviral drugs, a better understanding of VZV pathogenesis, and advances in diagnostic virology have made it possible to control VZV in the United States. Occult forms of VZV-induced disease have been recognized, including zoster sine herpete and enteric zoster, which have expanded the field. Future progress should include development of more effective vaccines to prevent HZ and a more complete understanding of the consequences of VZV latency in the enteric nervous system.

T-Cell tropism of simian varicella virus during primary infection

Varicella-zoster virus (VZV) causes varicella, establishes a life-long latent infection of ganglia and reactivates to cause herpes zoster. The cell types that transport VZV from the respiratory tract to skin and ganglia during primary infection are unknown. Clinical, pathological, virological and immunological features of simian varicella virus (SVV) infection of non-human primates parallel those of primary VZV infection in humans. To identify the host cell types involved in virus dissemination and pathology, we infected African green monkeys intratracheally with recombinant SVV expressing enhanced green fluorescent protein (SVV-EGFP) and with wild-type SVV (SVV-wt) as a control. The SVV-infected cell types and virus kinetics were determined by flow cytometry and immunohistochemistry, and virus culture and SVV-specific real-time PCR, respectively. All monkeys developed fever and skin rash. Except for pneumonitis, pathology produced by SVV-EGFP was less compared to SVV-wt. In lungs, SVV infected alveolar myeloid cells and T-cells. During viremia the virus preferentially infected memory T-cells, initially central memory T-cells and subsequently effector memory T-cells. In early non-vesicular stages of varicella, SVV was seen mainly in perivascular skin infiltrates composed of macrophages, dendritic cells, dendrocytes and memory T-cells, implicating hematogenous spread. In ganglia, SVV was found primarily in neurons and occasionally in memory T-cells adjacent to neurons. In conclusion, the data suggest the role of memory T-cells in disseminating SVV to its target organs during primary infection of its natural and immunocompetent host.

Varicella-zoster virus (VZV) causes varicella, establishes life-long latent infection in ganglia and reactivates later in life to cause zoster. VZV is acquired via the respiratory route, with skin rash occurring up to 3 weeks after exposure. The cell types that transport VZV to skin and ganglia during primary infection are unknown. Simian varicella virus (SVV) infection of non-human primates mimics clinical, pathological and immunological features of human VZV infection. African green monkeys were infected with recombinant SVV expressing enhanced green fluorescent protein (SVV-EGFP) or wild-type SVV (SVV-wt) as a control. By visualizing SVV-EGFP−infected cells in the living animal and in tissue samples, we identified the virus-infected cell types in blood, lungs, skin and ganglia during primary infection. Our data demonstrate that during viremia, SVV predominantly infects peripheral blood memory T-cells. Detection of SVV-infected memory T-cells in lungs, in early varicella skin lesions and also, albeit to a lesser extent, in ganglia suggests a role for memory T-cells in transporting virus to these organs. Our study provides novel insights into the cell types involved in virus dissemination and the overall pathology of varicella in a non-human primate model.

T-cell immunity to human alphaherpesviruses

Human alphaherpesviruses (αHHV) - herpes simplex virus type 1 (HSV-1), HSV-2, and varicella-zoster virus (VZV) - infect mucosal epithelial cells, establish a lifelong latent infection of sensory neurons, and reactivate intermittingly to cause recrudescent disease. Although chronic αHHV infections co-exist with brisk T-cell responses, T-cell immune suppression is associated with worsened recurrent infection. Induction of αHHV-specific T-cell immunity is complex and results in poly-specific CD4 and CD8 T-cell responses in peripheral blood. Specific T-cells are localized to ganglia during the chronic phase of HSV infection and to several infected areas during recurrences, and persist long after viral clearance. These recent advances hold promise in the design of new vaccine candidates.

Comprehensive analysis of varicella-zoster virus proteins using a new monoclonal antibody collection

Varicella-zoster virus (VZV) is the etiological agent of chickenpox and shingles. Due to the virus's restricted host and cell type tropism and the lack of tools for VZV proteomics, it is one of the least-characterized human herpesviruses. We generated 251 monoclonal antibodies (MAbs) against 59 of the 71 (83%) currently known unique VZV proteins to characterize VZV protein expression in vitro and in situ. Using this new set of MAbs, 44 viral proteins were detected by Western blotting (WB) and indirect immunofluorescence (IF); 13 were detected by WB only, and 2 were detected by IF only. A large proportion of viral proteins was analyzed for the first time in the context of virus infection. Our study revealed the subcellular localization of 46 proteins, 14 of which were analyzed in detail by confocal microscopy. Seven viral proteins were analyzed in time course experiments and showed a cascade-like temporal gene expression pattern similar to those of other herpesviruses. Furthermore, selected MAbs tested positive on human skin lesions by using immunohistochemistry, demonstrating the wide applicability of the MAb collection. Finally, a significant portion of the VZV-specific antibodies reacted with orthologs of simian varicella virus (SVV), thus enabling the systematic analysis of varicella in a nonhuman primate model system. In summary, this study provides insight into the potential function of numerous VZV proteins and novel tools to systematically study VZV and SVV pathogenesis.