Characterization of an unusual DS-1-like G8P[8] rotavirus strain from Japan in 2017: Evolution of emerging DS-1-like G8P[8] strains through reassortment.

The emergence of unusual DS-1-like intergenogroup reassortant rotaviruses having the bovine-like G8 genotype (DS-1-like G8P[8] strains) has been reported from several Asian countries. During the rotavirus surveillance program in Japan in 2017, a DS-1-like G8P[8] strain (RVA/Human-wt/JPN/SO1162/2017/G8P[8]) was identified in 43 rotavirus-positive stool samples. Strain SO1162 was shown to have a unique genotype constellation including both genogroup 1 and 2 genes: G8-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Phylogenetic analysis revealed that the VP1 gene of strain SO1162 appeared to have originated from DS-1-like G1P[8] strains from Thailand and Vietnam, while the remaining 10 genes were closely related to those of the previously reported DS-1-like G8P[8] strains. Thus, strain SO1162 was suggested to be a reassortant that acquired the VP1 gene from Southeast Asian DS-1-like G1P[8] strains on the genetic background of co-circulating DS-1-like G8P[8] strains. Our findings will provide important insights into the evolutionary dynamics of emerging DS-1-like G8P[8] strains.