Determination of the geographical origin of unidentified cadavers based on geographical differences in genotype of varicella–zoster virus

Abstract

A new method was developed for determining the geographical origin of unidentified cadavers by examining the genome of varicella-zoster virus (VZV), which resides latently throughout life in most individuals and the genotypes which show distinct geographical distribution. VZV DNA samples extracted from the trigeminal ganglia of 62 cadavers (59 from Japan, and 1 each from the United Kingdom, Mongolia, and Pakistan) submitted for medico-legal autopsy were examined. Sequencing was performed on a 358-bp region in the open reading frame (ORF) 22 containing four single nucleotide polymorphisms (SNPs) and a 419-bp region in ORF 62 containing 2 SNPs in the VZV genome. Using these SNP markers, the VZV genome was classified into the nine genotypes described previously. Phylogenetic tree analysis was also undertaken for the sequenced regions and for the 22 existing VZV strains described previously. In addition, 21 samples were subcloned for detection of co-infection. The VZV genome was classified successfully into nine genotypes using four SNPs in ORF 22 and two SNPs in ORF 62 as markers. Among Japanese cadavers, 57 carried genotype J, 1 carried genotype M1, and 1 carried genotype M2. The British and the Mongolian cadavers carried genotype E1 and the Pakistani cadaver carried M1. Phylogenetic tree analysis showed that VZV strains can be classified into different genotypes with high bootstrap values. None of the subcloned samples showed evidence of co-infection. These results suggest that valuable additional information for determining the geographical origin of unidentified cadavers can be provided by examining the VZV genome.