Reassortant Formation and Selection Following Coinfection of Cultured Cells with Subgroup 2 Human Rotaviruses

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Abstract
Reassortant formation following coinfection has been suggested as a mechanism of evolution of rotaviruses. This study was designed to examine the selection of reassortants following coinfection of cultured cells with pairs of subgroup 2 human rotaviruses. The three pairs studied (Wa .times. P, CJN .times. 31, 62 .times. 69) were chosen to maximize the number of RNA segments that could be electrophoretically distinguished. After coinfection and multiple passages, reproducible selection of reassortants was observed with each pair. Although more segments were selected from the virus of a pair that grew to higher titre, certain segments were selected independently of the relative growth properties or multiplicities of infection of the coinfecting viruses; selection of other segments was dependent on both. In determining the time and cause of selection it was found that no selection of genomic RNA segments was detectable prior to or during viral particle assembly in coinfected cells. However, selection was evident within the infectious progeny population after a single cycle of replication. Therefore, selection of specific reassortants following coinfection was apparently due to differences in the infectivities of progeny viruses and not in their assembly. This implies that these infectivities were a function of the parental origin of specific genomic segments.