Varicella Zoster Virus Induces Nuclear Translocation of the Neurokinin-1 Receptor, Promoting Lamellipodia Formation and Viral Spread in Spinal Astrocytes

Suppression of the host antiviral response by non-infectious varicella zoster virus extracellular vesicles

Varicella zoster virus (VZV) reactivates from ganglionic sensory neurons to produce herpes zoster (shingles) in a unilateral dermatomal distribution, typically in the thoracic region. Reactivation not only heightens the risk of stroke and other neurological complications but also increases susceptibility to co-infections with various viral and bacterial pathogens at sites distant from the original infection. The mechanism by which VZV results in complications remote from the initial foci remains unclear. Small extracellular vesicles (sEVs) are membranous signaling structures that can deliver proteins and nucleic acids to modify the function of distal cells and tissues during normal physiological conditions. Although viruses have been documented to exploit the sEV machinery to propagate infection, the role of non-infectious sEVs released from VZV-infected neurons in viral spread and disease has not been studied. Using multi-omic approaches, we characterized the content of sEVs released from VZV-infected human sensory neurons (VZV sEVs). One viral protein was detected (immediate-early 62), as well as numerous immunosuppressive and vascular disease-associated host proteins and miRNAs that were absent in sEVs from uninfected neurons. Notably, VZV sEVs are non-infectious yet transcriptionally altered primary human cells, suppressing the antiviral type 1 interferon response and promoting neuroinvasion of a secondary pathogen in vivo. These results challenge our understanding of VZV infection, proposing that the virus may contribute to distant pathologies through non-infectious sEVs beyond the primary infection site. Furthermore, this study provides a previously undescribed immune-evasion mechanism induced by VZV that highlights the significance of non-infectious sEVs in early VZV pathogenesis.

IMPORTANCE

Varicella zoster virus (VZV) is a ubiquitous human virus that predominantly spreads by direct cell-cell contact and requires efficient and immediate host immune evasion strategies to spread. The mechanisms of immune evasion prior to virion entry have not been fully elucidated and represent a critical gap in our complete understanding of VZV pathogenesis. This study describes a previously unreported antiviral evasion strategy employed by VZV through the exploitation of the infected host cell's small extracellular vesicle (sEV) machinery. These findings suggest that non-infectious VZV sEVs could travel throughout the body, affecting cells remote from the site of infection and challenging the current understanding of VZV clinical disease, which has focused on local effects and direct infection. The significance of these sEVs in early VZV pathogenesis highlights the importance of further investigating their role in viral spread and secondary disease development to reduce systemic complications following VZV infections.

Trigeminal Postherpetic Neuralgia: From Pathophysiology to Treatment

PURPOSE OF REVIEW

Trigeminal postherpetic neuralgia (TG-PHN) is a neuropathic pain condition complicating herpes zoster (HZ) attributed to the trigeminal nerve. It poses significant challenges due to its persistent and debilitating nature. This review explores the clinical characteristics of TG-PHN, analyzes its pathophysiological underpinnings, and addresses existent and potential therapies.

RECENT FINDINGS

TG-PHN is one of the most common and complex PHN locations. It has distinguishing clinical and pathophysiological characteristics, starting with viral triggered injuries to the trigeminal ganglion (TG) and peripheral tissue and involving the ascending and descending brain modulation pathways. Current therapies include vaccines, oral and topical medications, and interventional approaches, like nerve blocks and neurostimulation. This review covers TG-PHN's clinical and physiological components, treatment options, and potential future targets for improved management. By exploring the complexities of this condition, we aim to contribute to developing more effective and targeted therapies for patients suffering from trigeminal PHN.

Advances in the research and application of neurokinin-1 receptor antagonists

Recently, the substance P (SP)/neurokinin-1 receptor (NK-1R) system has been found to be involved in various human pathophysiological disorders including the symptoms of coronavirus disease 2019 (COVID-19). Besides, studies in the oncological field have demonstrated an intricate correlation between the upregulation of NK-1R and the activation of SP/NK-1R system with the progression of multiple carcinoma types and poor clinical prognosis. These findings indicate that the modulation of SP/NK-1R system with NK-1R antagonists can be a potential broad-spectrum antitumor strategy. This review updates the latest potential and applications of NK-1R antagonists in the treatment of human diseases and cancers, as well as the underlying mechanisms. Furthermore, the strategies to improve the bioavailability and efficacy of NK-1R antagonist drugs are summarized, such as solid dispersion systems, nanonization, and nanoencapsulation. As a radiopharmaceutical therapeutic, the NK-1R antagonist aprepitant was originally developed as radioligand receptor to target NK-1R-overexpressing tumors. However, combining NK-1R antagonists with other drugs can produce a synergistic effect, thereby enhancing the therapeutic effect, alleviating the symptoms, and improving patients quality of life in several diseases and cancers.

Role of Intracellular Amyloid β as Pathway Modulator, Biomarker, and Therapy Target

The β- and γ-secretase-driven cleavage of the amyloid precursor protein (APP) gives rise to the amyloid β peptide, which is believed to be the main driver of neurodegeneration in Alzheimer’s disease (AD). As it is prominently detectable in extracellular plaques in post-mortem AD brain samples, research in recent decades focused on the pathological role of extracellular amyloid β aggregation, widely neglecting the potential meaning of very early generation of amyloid β inside the cell. In the last few years, the importance of intracellular amyloid β (iAβ) as a strong player in neurodegeneration has been indicated by a rising number of studies. In this review, iAβ is highlighted as a crucial APP cleavage fragment, able to manipulate intracellular pathways and foster neurodegeneration. We demonstrate its relevance as a pathological marker and shed light on initial studies aiming to modulate iAβ through pharmacological treatment, which has been shown to have beneficial effects on cognitive properties in animal models. Finally, we display the relevance of viral infections on iAβ generation and point out future directions urgently needed to manifest the potential relevance of iAβ in Alzheimer’s disease.

VZV Infection of Primary Human Adrenal Cortical Cells Produces a Proinflammatory Environment without Cell Death

Virus infection of adrenal glands can disrupt secretion of mineralocorticoids, glucocorticoids, and sex hormones from the cortex and catecholamines from the medulla, leading to a constellation of symptoms such as fatigue, dizziness, weight loss, nausea, and muscle and joint pain. Specifically, varicella zoster virus (VZV) can produce bilateral adrenal hemorrhage and adrenal insufficiency during primary infection or following reactivation. However, the mechanisms by which VZV affects the adrenal glands are not well-characterized. Herein, we determined if primary human adrenal cortical cells (HAdCCs) infected with VZV support viral replication and produce a proinflammatory environment. Quantitative PCR showed VZV DNA increasing over time in HAdCCs, yet no cell death was seen at 3 days post-infection by TUNEL staining or Western Blot analysis with PARP and caspase 9 antibodies. Compared to conditioned supernatant from mock-infected cells, supernatant from VZV-infected cells contained significantly elevated IL-6, IL-8, IL-12p70, IL-13, IL-4, and TNF-α. Overall, VZV can productively infect adrenal cortical cells in the absence of cell death, suggesting that these cells may be a potential reservoir for ongoing viral replication and proinflammatory cytokine production, leading to chronic adrenalitis and dysfunction.

Targeted RNA Sequencing of VZV-Infected Brain Vascular Adventitial Fibroblasts Indicates That Amyloid May Be Involved in VZV Vasculopathy

BACKGROUND AND OBJECTIVES

Compared with stroke controls, patients with varicella zoster virus (VZV) vasculopathy have increased amyloid in CSF, along with increased amylin (islet amyloid polypeptide [IAPP]) and anti-VZV antibodies. Thus, we examined the gene expression profiles of VZV-infected primary human brain vascular adventitial fibroblasts (HBVAFs), one of the initial arterial cells infected in VZV vasculopathy, to determine whether they are a potential source of amyloid that can disrupt vasculature and potentiate inflammation.

METHODS

Mock- and VZV-infected quiescent HBVAFs were harvested at 3 days postinfection. Targeted RNA sequencing of the whole-human transcriptome (BioSpyder Technologies, TempO-Seq) was conducted followed by gene set enrichment and pathway analysis. Selected pathways unique to VZV-infected cells were confirmed by enzyme-linked immunoassays, migration assays, and immunofluorescence analysis (IFA) that included antibodies against amylin and amyloid-beta, as well as amyloid staining by Thioflavin-T.

RESULTS

Compared with mock, VZV-infected HBVAFs had significantly enriched gene expression pathways involved in vascular remodeling and vascular diseases; confirmatory studies showed secretion of matrix metalloproteinase-3 and -10, as well increased migration of infected cells and uninfected cells when exposed to conditioned media from VZV-infected cells. In addition, significantly enriched pathways involved in amyloid-associated diseases (diabetes mellitus, amyloidosis, and Alzheimer disease), tauopathy, and progressive neurologic disorder were identified; predicted upstream regulators included amyloid precursor protein, apolipoprotein E, microtubule-associated protein tau, presenilin 1, and IAPP. Confirmatory IFA showed that VZV-infected HBVAFs contained amyloidogenic peptides (amyloid-beta and amylin) and intracellular amyloid.

DISCUSSION

Gene expression profiles and pathway enrichment analysis of VZV-infected HBVAFs, as well as phenotypic studies, reveal features of pathologic vascular remodeling (e.g., increased cell migration and changes in the extracellular matrix) that can contribute to cerebrovascular disease. Furthermore, the discovery of amyloid-associated transcriptional pathways and intracellular amyloid deposition in HBVAFs raise the possibility that VZV vasculopathy is an amyloid disease. Amyloid deposition may contribute to cell death and loss of vascular wall integrity, as well as potentiate chronic inflammation in VZV vasculopathy, with disease severity and recurrence determined by the host's ability to clear virus infection and amyloid deposition and by the coexistence of other amyloid-associated diseases (i.e., Alzheimer disease and diabetes mellitus).

Amylin, Aβ42, and Amyloid in Varicella Zoster Virus Vasculopathy Cerebrospinal Fluid and Infected Vascular Cells

BACKGROUND

Varicella zoster virus (VZV) vasculopathy is characterized by persistent arterial inflammation leading to stroke. Studies show that VZV induces amyloid formation that may aggravate vasculitis. Thus, we determined if VZV central nervous system infection produces amyloid.

METHODS

Aβ peptides, amylin, and amyloid were measured in cerebrospinal fluid (CSF) from 16 VZV vasculopathy subjects and 36 stroke controls. To determine if infection induced amyloid deposition, mock- and VZV-infected quiescent primary human perineurial cells (qHPNCs), present in vasculature, were analyzed for intracellular amyloidogenic transcripts/proteins and amyloid. Supernatants were assayed for amyloidogenic peptides and ability to induce amyloid formation. To determine amylin's function during infection, amylin was knocked down with small interfering RNA and viral complementary DNA (cDNA) was quantitated.

RESULTS

Compared to controls, VZV vasculopathy CSF had increased amyloid that positively correlated with amylin and anti-VZV antibody levels; Aβ40 was reduced and Aβ42 unchanged. Intracellular amylin, Aβ42, and amyloid were seen only in VZV-infected qHPNCs. VZV-infected supernatant formed amyloid fibrils following addition of amyloidogenic peptides. Amylin knockdown decreased viral cDNA.

CONCLUSIONS

VZV infection increased levels of amyloidogenic peptides and amyloid in CSF and qHPNCs, indicating that VZV-induced amyloid deposition may contribute to persistent arterial inflammation in VZV vasculopathy. In addition, we identified a novel proviral function of amylin.

Varicella-Zoster Virus Infection of Primary Human Spinal Astrocytes Produces Intracellular Amylin, Amyloid-β, and an Amyloidogenic Extracellular Environment

BACKGROUND

Herpes zoster is linked to amyloid-associated diseases, including dementia, macular degeneration, and diabetes mellitus, in epidemiological studies. Thus, we examined whether varicella-zoster virus (VZV)-infected cells produce amyloid.

METHODS

Production of intracellular amyloidogenic proteins (amylin, amyloid precursor protein [APP], and amyloid-β [Aβ]) and amyloid, as well as extracellular amylin, Aβ, and amyloid, was compared between mock- and VZV-infected quiescent primary human spinal astrocytes (qHA-sps). The ability of supernatant from infected cells to induce amylin or Aβ42 aggregation was quantitated. Finally, the amyloidogenic activity of viral peptides was examined.

RESULTS

VZV-infected qHA-sps, but not mock-infected qHA-sps, contained intracellular amylin, APP, and/or Aβ, and amyloid. No differences in extracellular amylin, Aβ40, or Aβ42 were detected, yet only supernatant from VZV-infected cells induced amylin aggregation and, to a lesser extent, Aβ42 aggregation into amyloid fibrils. VZV glycoprotein B (gB) peptides assembled into fibrils and catalyzed amylin and Aβ42 aggregation.

CONCLUSIONS

VZV-infected qHA-sps produced intracellular amyloid and their extracellular environment promoted aggregation of cellular peptides into amyloid fibrils that may be due, in part, to VZV gB peptides. These findings suggest that together with host and other environmental factors, VZV infection may increase the toxic amyloid burden and contribute to amyloid-associated disease progression.

Varicella Zoster Virus Induces Differential Cell-Type Specific Responses in Human Corneal Epithelial Cells and Keratocytes

Purpose

While VZV DNA and antigen have been detected in acute and chronic VZV keratitis, it is unclear whether productive infection of corneal cells is ongoing or whether residual, noninfectious VZV antigens elicit inflammation. Herein, we examined VZV-infected primary human corneal epithelial cells (HCECs) and keratocytes (HKs) to elucidate the pathogenesis of VZV keratitis.

Methods

HCECs and HKs were mock- or VZV infected. Seven days later, cells were examined for morphology, proinflammatory cytokine and matrix metalloproteinase (MMP) release, ability to recruit peripheral blood mononuclear cells (PBMCs) and neutrophils, and MMP substrate cleavage.

Results

Both cell types synthesized infectious virus. VZV-infected HCECs proliferated, whereas VZV-infected HKs died. Compared to mock-infected cells, VZV-infected HCECs secreted significantly more IL-6, IL-8, IL-10, and IL-12p70 that were confirmed at the transcript level, and MMP-1 and MMP-9; conditioned supernatant attracted PBMCs and neutrophils and cleaved MMP substrates. In contrast, VZV-infected HKs suppressed cytokine secretion except for IL-8, which attracted neutrophils, and suppressed MMP release and substrate cleavage.

Conclusions

Overall, VZV-infected HCECs recapitulate findings of VZV keratitis with respect to epithelial cell proliferation, pseudodendrite formation and creation of a proinflammatory environment, providing an in vitro model for VZV infection of corneal epithelial cells. Furthermore, the proliferation and persistence of VZV-infected HCECs suggest that these cells may serve as viral reservoirs if immune clearance is incomplete. Finally, the finding that VZV-infected HKs die and suppress most proinflammatory cytokines and MMPs may explain the widespread death of these cells with unchecked viral spread due to ineffective recruitment of PBMCs.

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.

Varicella zoster virus differentially alters morphology and suppresses proinflammatory cytokines in primary human spinal cord and hippocampal astrocytes

BACKGROUND

Varicella zoster virus (VZV) is a ubiquitous alphaherpesvirus that produces varicella and zoster. VZV can infect multiple cell types in the spinal cord and brain, including astrocytes, producing myelopathy and encephalopathy. While studies of VZV-astrocyte interactions are sparse, a recent report showed that quiescent primary human spinal cord astrocytes (qHA-sps) did not appear activated morphologically during VZV infection. Since astrocytes play a critical role in host defenses during viral infections of the central nervous system, we examined the cytokine responses of qHA-sps and quiescent primary human hippocampal astrocytes (qHA-hps) to VZV infection in vitro, as well as the ability of conditioned supernatant to recruit immune cells.

METHODS

At 3 days post-infection, mock- and VZV-infected qHA-sps and qHA-hps were examined for morphological changes by immunofluorescence antibody assay using antibodies directed against glial fibrillary acidic protein and VZV. Conditioned supernatants were analyzed for proinflammatory cytokines [interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, IL-13, interferon-gamma, and tumor necrosis factor-α] using the Meso Scale Discovery multiplex ELISA platform. Finally, the ability of conditioned supernatants to attract peripheral blood mononuclear cells (PBMCs) was determined using a chemotaxis assay. Quiescent primary human perineurial cells (qHPNCs) served as a control for VZV-induced cytokine production and PBMC migration. To confirm that the astrocytes have the ability to increase cytokine secretion, qHA-sps and qHA-hps were treated with IL-1β and examined for morphological changes and IL-6 secretion.

RESULTS

VZV-infected qHA-sps displayed extensive cellular processes, whereas VZV-infected qHA-hps became swollen and clustered together. Astrocytes had the capacity to secrete IL-6 in response to IL-1β. Compared to mock-infected cells, VZV-infected qHA-sps showed significantly reduced secretion of IL-2, IL-4, IL-6, IL-12p70, and IL-13, while VZV-infected qHA-hps showed significantly reduced IL-8 secretion. In contrast, levels of all 10 cytokines examined were significantly increased in VZV-infected qHPNCs. Consistent with these results, conditioned supernatant from VZV-infected qHPNCs, but not that from VZV-infected qHA-sps and qHA-hps, recruited PBMCs.

CONCLUSIONS

VZV-infected qHA-sps and qHA-hps have distinct morphological alterations and patterns of proinflammatory cytokine suppression that could contribute to ineffective viral clearance in VZV myelopathy and encephalopathy, respectively.