A proposal for a common nomenclature for viral clades that form the species varicella-zoster virus: summary of VZV Nomenclature Meeting 2008, Barts and the London School of Medicine and Dentistry, 24-25 July 2008

Abstract

Varicella-zoster virus (VZV), the cause of chickenpox and zoster, was the first human herpesvirus to be sequenced fully and the first for which vaccines have been licensed and widely used. Three groups have published genotyping schemes based on single nucleotide polymorphisms (SNPs) and, between them, have identified five distinct phylogenetic clades, with an additional two putative clades. Sequencing of over 23 whole VZV genomes from around the world further refined the phylogenetic distinctions between SNP genotypes. Widespread surveillance in countries in which the varicella vaccine is now in use and the difficulties posed by three unique genotyping approaches prompted an international meeting, at which a common nomenclature based on phylogenetic clades was agreed upon. In this paper, we review the original genotyping schemes and discuss the basis for a novel common nomenclature for VZV strains. We propose a minimum set of SNPs that we recommend should be used to genotype these viruses. Finally, we suggest criteria by which novel clades can be recognized.

Varicella zoster virus infection

“…Viral genomic studies have identified five viral clades and their geographical distribution: clades 1, 3 and 5 are of European origin; clade 2 includes Asian strains such as the parental Oka strain, from which varicella and zoster vaccines were derived; and clade 4 contains African strains 8 . Varicella epidemiology and disease burden have been studied primarily in developed countries.…”

Revisiting the genotyping scheme for varicella-zoster viruses based on whole-genome comparisons

“…VZV nomenclature currently recognizes nine clades, six established clades designated by Arabic numerals 1 to 6, and three provisional clades designated by the Roman numerals VII, VIII and IX [3,4]. In accordance with the nomenclature system proposed in 2008, two WGSs are needed to redesignate a provisional clade as established.…”

“…Prior to the availability of high-throughput NGS, genotyping strategies relied on targeted sequencing of informative SNPs. Several groups published methods for identifying VZV clades using targeted SNP analysis that were useful for discriminating the seven clades recognized at that time [3,6]. Those methods are now unsuitable for the reliable discrimination of the currently recognized VZV clades.…”

Seropositivity of Varicella zoster virus in vaccinated Korean children and MAV vaccine group

“…While clades 1, 3, and 5 are common in Europe, clade 2 is most widely distributed in Japan and East Asia. [4][5][6] To prevent varicella, the Oka strain varicella vaccine was developed in Japan in 1974, and the MAV strain varicella vaccine was developed in Korea in 1993. Both vaccines contain live attenuated viruses that cluster in clade 2.…”

“…Varicella usually affects children aged 2-8 y. [1][2][3] Based on the universal nomenclature for VZV, VZV is categorized into 5 clades (clades [1][2][3][4][5]. While clades 1, 3, and 5 are common in Europe, clade 2 is most widely distributed in Japan and East Asia.…”