Genotypic selection following coinfection of cultured cells with subgroup 1 and subgroup 2 human rotaviruses.

The purpose of this study was to determine why identifiable reassortants between subgroup 1 and subgroup 2 rotaviruses have been so rarely isolated from human specimens. Cultured cells were coinfected with pairs of subgroup 1 and 2 human rotaviruses and passaged multiple times to simulate natural reassortant formation and selection in vivo. After coinfection of MA-104 cells with subgroup 1 (DS-1) and subgroup 2 (either Wa or P) strains, approximately 14% of the plaque-picked progeny were shown to be reassortants. During multiple passages of these coinfected cultures, however, complete (Wa virus coinfection) or nearly complete (P virus coinfection) loss of detectable DS-1 segments from progeny was observed. Thus, when all segments of the subgroup 2 viruses were present in coinfected cultures, these segments dominated in the selected progeny. Coinfection with subgroup 1-subgroup 2 rotavirus reassortants and the DS-1 strain followed by multiple passages, however, resulted in complete loss of some segments from the subgroup 2 strains originally present in the reassortants. Therefore, segments from the parental subgroup 2 viruses appeared to be selected in toto during multiple passages because they were dominant as a group, not because individual segments of these viruses were consistently favoured over their subgroup 1 virus counterparts.