Whole-Genome Characterization of Rare Artiodactyl-Like G10P [14] and G8P [14] Rotavirus a Strains Detected in Pediatric Gastroenteritis Cases in Hokkaido Prefecture, Japan.

Rotavirus alphagastroenteritidis (RVA) is the leading cause of acute gastroenteritis in young children worldwide, as well as in a wide range of animal species. In 2020 and 2022, we identified three unusual RVA strains in pediatric gastroenteritis patients in Hokkaido Prefecture, Japan, using next-generation sequencing: one G10P[14] strain (Ni20-23) and two G8P[14] strains (Ni20-37 and To22-1). All three strains possessed the genotype constellation G10/G8-P[14]-I2-R2-C2-M2-A3-N2-T6-E2-H3. Phylogenetic analyses of these 11 genome segments indicated that the strains were artiodactyl-like RVAs. However, no genome segment exhibited > 98% nucleotide identity among the three strains, suggesting that they originated from distinct artiodactyl RVA strains. Furthermore, no previously reported artiodactyl RVA strain showed > 90% nucleotide identity across all 11 segments; thus, the direct animal origins of these strains remain unclear. As observed in these strains, nearly all artiodactyl-like RVAs previously detected in humans have carried the VP4 genotype P[14], indicating a potential role of P[14] in facilitating cross-species transmission. One strain (To22-1/G8P[14]) was detected in a child who had received two doses of Rotarix (G1P[8] monovalent vaccine). Comparative amino acid analysis of VP4 between the To22-1/G8P[14] strain and the P[8] Rotarix vaccine strain revealed substitutions at 18 of 37 (48.6%) known antigenic epitope sites, suggesting a potential antigenic mismatch. Continued surveillance and further studies are warranted to elucidate the mechanisms underlying interspecies transmission of artiodactyl-like P[14] RVAs and to assess the effectiveness of current vaccines against such strains.