Prevalence and molecular characterization of G1P[8] human rotaviruses possessing DS-1-like VP6, NSP4, and NSP5/6 in Japan.

During a survey of human rotaviruses in Okayama Prefecture, Japan in the 2011-2012 rotavirus season (between September 2011 and August 2012), G3P[8] was found to be a predominant genotype overall. However, G1P[8] emerged in the latter half of the season. To clarify the genetic background of the G1P[8] strains, the VP7, VP4, VP6, NSP4, and NSP5/6 genes of the strains were sequenced and genotyped. As a result, it was demonstrated that the strains with two different genotype constellations (G1-P[8]-I1-E1-H1 and G1-P[8]-I2-E2-H2) prevailed in the season. The G1P[8] strains possessing the DS-1-like VP6, NSP4, and NSP5/6 genes (the DS-1-like G1P[8] strains), which should reveal a short electropherotype, were originated from possible intergenogroup reassortment events. The DS-1-like G1P[8] strains accounted for 74.1% of all G1P[8] strains and were detected continuously throughout the season but not in the preceding season, indicating the possibility of new introduction and rapid spreading of these strains in the 2011-2012 season. The results suggest that the intergenogroup reassortants, considered generally unstable, can spread rapidly and become relevant.