Predominance of DS-1-like G8P[8] rotavirus reassortant strains in children hospitalized with acute gastroenteritis in Thailand, 2018-2020.

Rotavirus A (RVA) is an important cause of acute gastroenteritis (AGE) in children. This study aims to investigate the molecular epidemiology of RVA in children hospitalized with AGE in Chiang Rai, Thailand in 2018-2020 by reverse transcription polymerase chain reaction. Of 302 samples, RVA was detected in 11.6% (35 samples): 11.3% (19/168) in 2018-2019 and 11.9% (16/134) in 2019-2020. G8P[8] was the predominant genotype at 68.4% in 2018-2019 and 81.2% in 2019-2020. G1P[8] (15.8%), G2P[4] (5.3%), G3P[8] (10.5%) in 2018-2019, and G9P[8] (18.8%) in 2019-2020 were also detected. Whole-genome analysis of G8P[8] revealed a DS-1-like genetic backbone: G8-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Phylogenetically, the VP7 genes of G8P[8] clustered in a major lineage with previously published 51 DS-1-like G8P[8] reference strains, closely related to 13 G8P[8] strains from Thailand and China. These G8P[8] strains contained two unique amino acid substitutions (A125S and N147D) in the VP7 antigenic epitopes. In addition, the VP1 and NSP2 genes of G8P[8] clustered in lineages separated from the DS-1-like G8P[8] reference strains with a high genetic divergence but were closely related to G1P[8], G2P[4], G3P[8], or G9P[8]. Several amino acid differences were observed in the VP7 and VP8* antigenic epitopes of G8P[8] compared with RVA vaccine strains. Homology modeling confirmed that these different amino acid residues were located on the surface-exposed area of the structure. Taken together, the genetic analysis clearly defines the Chiang Rai DS-1-like G8P[8] strains as a novel reassortant strain that might have evolved genetically through reassortment events and consequently received their VP1 and NSP2 genes from locally cocirculating-RVA genotypes.