Three forms of AU-1 like human rotaviruses differentiated by their overall genomic constellation and by the sequence of their VP8*

Summary

Insight into the origin of human rotaviruses carrying the AU-1 VP4 allele was gained by examining their genomic RNA constellation using RNA–RNA hybridization and by sequencing the VP8^* portion (nucleotides 1–750) of their gene 4. AU-1 like viruses isolated in Israel from children attending outpatient clinics were classified into three sub-genogroups based on RNA–RNA hybridization analysis: Subgenogroup 1 consists of two strains (Ro-5829 and Ro-5960) which belong to the AU-1 genogroup, since all their 11 segments hybridized to AU-1 segments. Subgenogroup 2 consists of one reassortant virus (Ro-5193) of which seven RNA segments hybridized to AU-1 segments and the remaining four segments hybridized to NCDV (bovine rotavirus). Subgenogroup 3 consists of four reassortant viruses (Ro-6460, Ro-6584, Ro-6784 and Ro-7044) which had a common genome constellation: only four of their RNA segments hybridized to AU-1 and the other seven segments hybridized to NCDV segments. Sequence analysis of the VP8^* gene also revealed a three level pattern of homology with the AU-1 prototype and the local AU-1-like strains which was consistent with the overall genomic (RNA–RNA) constellation: Subgenogroup 1 had 98–98.1% homology with the AU-1 prototype; Subgenogroup 2 had 96.8% homology with the AU-1 prototype and 95.6–96.7% homology with Subgenogroup 1; Subgenogroup 3 had 95.3–95.6% homology with the prototype AU-1 and 93.4–94.3% homology with Subgenogroup 1. Possible evolutionary pathways are discussed.