Abstract

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.

Highlights

  • Most adults worldwide are infected with the neurotropic human alphaherpesvirus, varicella-zoster virus (VZV) [1]

  • This led to his famous hypothesis that: “Following the primary infection, virus becomes latent in the sensory ganglia, where it can be reactivated from time to time” [4]

  • It is composed of two unique segments, termed unique long (UL ) and unique short (US ), that are flanked by inverted terminal repeat (TR) and internal repeat (IR) structures with high G + C contents

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Summary

Introduction

Most adults worldwide are infected with the neurotropic human alphaherpesvirus, varicella-zoster virus (VZV) [1]. Hope-Simpson, suggested that “herpes zoster is a spontaneous manifestation of varicella infection” This observation was based on a careful examination of ~3500 patients, including 192 HZ cases, who visited his practice over a 16-year period, combined with cautious reading of the available anatomical and epidemiological literature regarding. This led to his famous hypothesis that: “Following the primary infection (chickenpox), virus becomes latent in the sensory ganglia, where it can be reactivated from time to time (herpes zoster)” [4]. Eighteen years later, this hypothesis was proven by Dr Donald Gilden’s crucial discovery of VZV DNA in latently infected human ganglia [5]. We limit this review to only include studies of VZV latency in which there is a demonstrable lack of infectious virus production and/or any observable pathology

Structure and Genomic Organization of VZV
Coding Potential of the VZV Genome
VZV Gene Expression during Productive Infection
Stability of the VZV Genome
Sites of VZV Latency
Entry of VZV into the Peripheral Nervous System
Transcriptional Repression of Latent VZV Genomes
VZV Transcription in Human Ganglia
Comparison of VZV Latency In Vivo and In Vitro
Epigenetic Silencing of the Latent VZV Genome
The Varicella Zoster Virus Latency-Associated Transcripts
Comparison of VLT and LATs of Related Alphaherpesviruses
VZV Reactivation
Satellite Glial Cells and Innate Immunity
T-Cell Immunity
Findings
Future Perspectives
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