Primary infections with the varicella-zoster virus (VZV) result
in varicella, while latent reactivation leads to herpes zoster.
Both varicella and zoster can be prevented by live attenuated
vaccines. There have been reports suggesting that both clinical
VZV strains and those in vaccine preparations are genetically
polymorphic, containing mixtures of both wild-type
and vaccine-type sequences at certain vaccine-specific sites.
In this study, the genetic polymorphism of the VZV genome
was examined by analyzing the frequencies of minor alleles
at each nucleotide position. Next-generation sequencing of
the clinical VZV strain YC02 passaged in an in vitro cell culture
was used to identify genetically polymorphic sites (GPS),
where the minor allele frequency (MAF) exceeded 5%. The
number of GPS increased by 7.3-fold at high passages (p100)
when compared to low passages (p17), although the average
MAF remained similar. GPS were found in 6 open reading
frames (ORFs) in p17, 35, and 54 ORFs in p60 and p100, respectively.
GPS were found more frequently in the dispensable
gene group than the essential gene group, but the average MAF
was greater in the essential gene group. The most common
two major/minor base pairs were A/g and T/c. GPS were found
in all three passages at 16 positions, all located in the reiterated
(R) region. The population diversity as measured by Shannon
entropy increased in p60 and p100. However, the entropy
remained unchanged in the R regions.
Citations
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