Varicella-Zoster Virus

Viral Characteristics

Varicella-zoster virus (VZV) is a human-restricted alphaherpesvirus of the genus Varicellovirus. The VZV genome is a linear double-stranded DNA molecule of 125,000 base pairs (including a unique long region of 105,000 bp and a unique short region of 5232 bp, as well as internal repeat and terminal repeat regions). VZV particles are pleomorphic to spherical in shape, 150-200 nm in diameter and are composed of three proteinous layers: a nucleocapsid containing the viral double-stranded DNA (dsDNA) genome, a tegument layer, consisting of numerous proteins of both viral and host origin surrounding the nucleocapsid, and an envelope comprising a host-derived lipid bilayer inserted with viral glycoproteins facing outwards.

Fig.1 Structure of VZV virion. (Depledge, 2018)

Pathogenesis

There are three phases to VZV infection (primary infection, latency and reactivation), developing its biphasic mode of survival as chickenpox (varicella, primary infection) and shingles (reactivation). VZV is known to utilize a variety of binding sites and receptors to gain access to cells and to spread from an infected cell to an uninfected neighbor. Primary VZV infection results from droplet transmission at the airway epithelium, having an incubation period of 10-21 days. Primary VZV infection causes viremia in T-lymphocytes. Viremia induces a characteristic skin rash. During varicella, retrograde transport from the skin can enable VZV to reach sensory neurons in the dorsal root ganglion (DRG) and, from there, the neurons of the enteric nervous system (ENS). Later on, VZV reactivation from dorsal nerve ganglia causes antegrade travel of the virus to cause the dermatomal disease of herpes in a restricted dermatomal distribution.

Fig.2 Different phases of VZV infection. (Gershon, 2015)

Epidemiology

• Varicella

Varicella is transmitted by touching or breathing in the virus particles that come from varicella blisters, and possibly through tiny droplets from infected people that get into the air after they breathe or talk. Varicella occurs worldwide and is endemic in populations of sufficient size to sustain year-round transmission, with epidemics occurring every 2-3 years. Varicella shows a strong seasonal pattern, with peak incidence during winter and spring or the cool, dry season. Outbreaks occur commonly in settings where children congregate.

• Zoster

Zoster epidemiology has been described almost exclusively from developed countries with long life expectancies. The incidence and severity of zoster increase with age due to declining cell-mediated immunity to VZV. By the age of 85 years, >50% of the population reports at least one episode of zoster.

Prevention

There are two types of VZV vaccines

• Varicella vaccines include varilrix in the United Kingdom, varivax in the United States of America (USA), and the combined measles, mumps and rubella and varicella vaccine, all of which contain live-attenuated Oka strain of VZV.
• Zoster vaccines include zostavax and herpes zoster/subunit vaccine. Zostavax is the only herpes zoster vaccine that is currently approved in Europe and the USA. It contains the live attenuated VZV Oka stain and it is given as one injection subcutaneously.

Anti-VZV Products and Services

With years of experience in the field of antibody development, Creative Biolabs has successfully developed a platform with advanced optimization for anti-virus antibody generation. We provide a series of anti-VZV antibodies for hot targets including gE, gH, gL, gII and gIII protein. Our custom antibody services are fast, flexible, reliable and comprehensive to optimize results for your experiment. For further information and to discuss your project needs, please feel free to contact us.

References

1. Depledge, D.P.; et al. Molecular Aspects of Varicella-Zoster Virus Latency. Viruses. 2018, 10(7): 349.
2. Gershon, A. A.; et al. Varicella zoster virus infection. Nat Rev Dis Primers. 2015, 1: 15016.

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