PREFERENTIAL SELECTION OF HETEROLOGOUS G3-VP7 GENE IN THE GENETIC BACKGROUND OF SIMIAN ROTAVIRUS SA11 DETECTED BY USING A HOMOTYPIC SINGLE-VP7 GENE-SUBSTITUTION REASSORTANT

Introduction of segmented genomes into virion is an important process in viral replication of rotavirus. We previously studied the assortmen t of the VP7 gene segment (encoding outer capsid protein VP7) in the g enetic background of simian rotavirus SA11 (G serotype 3, G3) and foun d the preferential selection of homologous G3 VP7 gene over VP7 gene o f heterologous G serotype (G1, G2 or G4). In the present study, in ord er to clarify whether or not VP7 gene derived from different G3 rotavi rus (heterologous G3-VP7 gene) is also preferentially selected in the SA11 background, a single-VP7 gene-substitution reassortant was prepar ed from SA11 through multiple steps of coinfection with rotaviruses in vitro. The isolated reassortant, SNR1, possessed VP7 gene derived fro m canine G3 rotavirus K9 and all other gene segments of SA11 origin, a nd showed an identical growth characteristic to that of SA11. Amino ac id sequence of K9 VP7 gene showed a high degree of identity (93.6%) to SA11 VP7 gene. In analysis by mixed infection and multiple passages o f SNR1 and a single VP7 gene (with G1, G2 or G4 specificity) reassorta nt in the SA11 background, the G3-VP7 gene became predominant at early passage numbers. However, in mixed infection with SA11 and SNR1, homo logous G3-VP7 gene (SA11-VP7 gene) was preferentially selected into pr ogenies over heterologous one (K9-VP7 gene). These results together wi th our previous findings suggested that G3-VP7 gene, irrespective of o rigin of species, was functionally adapted to the genetic background o f SA11, although the homologous gene had a better fit with other SA11 genes than did heterologous one, providing suggestions for efficacious ness of multivalent reassortant rotavirus vaccine. (C) 1998 Elsevier S cience B.V. All rights reserved.