Genomic changes detected after serial passages in cell culture of virulent human G1P[8] rotaviruses

• Substitutions in VP4 and NSP4 were detected after serial passages in cell culture.
• Substitution of aa 385 in VP4 was located putative fusion domain.
• Substitution of aa 45 in NSP4 was located outside of enterotoxin domain.
• These substitutions in VP4 and NSP4 were also found in progenitor of Rotarix.

Serial passages of a virulent mouse rotavirus in cell cultures caused a loss of virulence in mice. To gain insight into the genomic mutations in human rotavirus during cell culture and its attenuation in humans, we serially passaged three wild type human G1P[8] rotavirus strains (Wa, DC3695, DC5685) derived from diarrheal stool samples up to 60 times in two different cell cultures (human colon adenocarcinoma cell line: HT29, and primary African green monkey kidney cells: primary AGMK). We sequenced the whole genomes of 60 times-passaged strains and compared them with those of the original viruses. Most substitutions were detected in VP4, followed by substitutions in VP7 and NSP4 genes. Substitution at amino acid 385 in the putative VP4 fusion domain and substitution T45M in NSP4 genes were detected in all AGMK-passaged strains, respectively. These genomic changes are likely to correlate with a loss of rotavirus virulence in humans.