Investigation of varicella-zoster virus (VZV) is important epidemiologically, and determination of its prevalence rate in human trigeminal ganglia is important to provide surveillance data. To date, studies on VZV detection in trigeminal ganglia have used specimens obtained from a relatively limited number of cadavers. This study attempted to detect VZV DNA as well as Herpes simplex virus type 1 (HSV-1) DNA by the polymerase chain reaction (PCR) from 414 samples of trigeminal ganglia obtained from 207 cadavers selected at random. The detection rate was examined to determine whether there were significant differences in the positive rate between the left and right trigeminal ganglia, males and females, and among age groups. A relationship was found between the positive rates for VZV and HSV-1. VZV DNA was detected in 391 of the trigeminal ganglia (94.4%) and 201 of the cadavers (97.1%) in 121/124 males and 80/83 females. HSV-1 DNA was detected in 251 of the samples (60.6%) and 134 of the cadavers (64.7%) in 72/124 males and 62/83 females. There was no significant difference for either virus in the detection rates between the left and right trigeminal ganglia and males and females. Age and positivity for HSV-1, but not VZV, showed a significant relationship. All 134 cadavers positive for HSV-1 were also positive for VZV. VZV and HSV-1 become latent in bilateral trigeminal ganglia, and are not affected by gender. The prevalence of HSV-1 was greater in advanced age, and the HSV-1-positive rate was correlated with the VZV-positive rate.

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.

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Personal identification using DNA typing of formalin-fixed tissue is very important in the forensic sciences. However, few studies have been conducted to determine the detection limit of DNA typing of formalin fixation time in samples using the AmpFℓSTR(®) Identifiler(®) PCR Amplification Kit (Identifiler Kit). We collected samples from five cadavers submitted for forensic autopsies, and fixed them either in a 10% formalin solution, or in a 10% neutral-buffered formalin solution. The amount of template DNA for polymerase chain reaction (PCR) amplification and the detection limit of DNA typing for the Identifiler Kit were determined. When tissues were fixed in 10% formalin, 10 ng of DNA template was required for successful genotyping even after three-hour fixation and 100 ng was required after one-week fixation for PCR amplification. However, when tissues were fixed in 10% neutral-buffered formalin, the required amount of DNA template was 1 ng for a fixation time of three hours to three days and 125 ng for three months. Fixation time in neutral-buffered formalin was longer for successful PCR than that in formalin solution. Dropout was more common with increasing formalin fixation time. These results suggest that neutral-buffered formalin is preferred to formalin for fixation of tissues if they are to be subjected to DNA typing and that tissues fixed with neutral-buffered formalin can be used for DNA typing using the Identifiler Kit unless the fixation time exceeds one month.