Sequencing of 21 Varicella-Zoster Virus Genomes Reveals Two Novel Genotypes and Evidence of Recombination

Abstract

Genotyping of 21 varicella-zoster virus (VZV) strains using a scattered single nucleotide polymorphism (SNP) method revealed ambiguous SNPs and two nontypeable isolates. For a further genetic characterization, the genomes of all strains were sequenced using the 454 technology. Almost-complete genome sequences were assembled, and most remaining gaps were closed with Sanger sequencing. Phylogenetic analysis of 42 genomes revealed five established and two novel VZV genotypes, provisionally termed VIII and IX. Genotypes VIII and IX are distinct from the previously reported provisional genotypes VI and VII as judged from the SNP pattern. The alignments showed evidence of ancient recombination events in the phylogeny of clade 4 and recent recombinations within single strains: 3/2005 (clade 1), 11 and 405/2007 (clade 3), 8 and DR (clade 4), CA123 and 413/2000 (clade 5), and strains of the novel genotypes VIII and IX. Bayesian tree inference of the thymidine kinase and the polymerase genes of the VZV clades and other varicelloviruses revealed that VZV radiation began some 110,000 years ago, which correlates with the out-of-Africa dispersal of modern humans. The split of ancestral clades 2/4 and 1/3/5/VIII/IX shows the greatest node height.