Molecular identification of a G2 rotavirus that provided a G1P[4] mono-reassortant with a DS-1-like genotype constellation.

The segmented nature of the rotavirus genome provides an opportunity for the virus to reassort upon co-infection of more than one rotavirus strain. Previously, two G1P[4] strains isolated from children with diarrhoea, AU64, and AU67, were shown by RNA-RNA hybridization to be a VP7 mono-reassortant possessing a DS-1 genogroup background. However, the origin of the parental G2 strain was not sought for at that time. The aim of this study, therefore, was to identify the G2 strain that provided AU64/AU67 with the DS-1-like genotype constellation. By carefully comparing the genomic RNA migration patterns on polyacrylamide gels of strains circulating at the same and nearby geographic locations around the time of the mono-reassortant detection (1989), a G2 strain designated 88H449 was shown to possess 10 genome segments co-migrating with those of AU64. Sequencing of all genome segments of AU64 and 88H449 showed that those two strains were 99.6-100% identical at the nucleotide level in all except the VP7 gene, indicating that the parental G2 strain that provided AU64 with the 10 genome segments was a sibling of 88H449. Sequencing of the VP7 genes of 36 G1P[8] strains circulating locally between 1981 and 1990 revealed the presence of strains bearing diverse VP7 sequences among which the closest nucleotide identity to AU64 was 98.6% and the closest amino acid identity in the major antigenic regions was 100%. This unusual mono-reassortant was concluded to be the result of a contemporary reassosrtment event occurring between locally co-circulating strains.