Analysis of Repeat Units in the R2 Region among Different Oka Varicella-Zoster Virus Vaccine Strains and Wild-Type Strains in Germany

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Abstract
The present study compared the number of R2 repeat units in six different Oka strains and in 54 varicella-zoster virus (VZV) wild-type strains isolated from patients with varicella or zoster in Germany. The R2 genomic region was characterized by polymerase chain reaction and sequencing methods. Five VZV Oka vaccine strains showed a number of seven 42-bp units and, in one, eight repeats were found. In 11 VZV wild-type strains isolated from patients with varicella, the copy number ranged between four and eight, and in 43 strains from zoster a similar range between four and nine copies was observed. About 80% of all strains showed between five and seven repeated units. More than one third of strains revealed seven repeats like Oka. The size of the R2 repeat region can also be different in single Oka vaccine strains. In German VZV wild-type strains, the R2 fragment seems to be not as variable as in Japanese wild-type strains.