G(VP7) SEROTYPE-DEPENDENT PREFERENTIAL VP7 GENE SELECTION DETECTED INTHE GENETIC BACKGROUND OF SIMIAN ROTAVIRUS SA11

We previously found the preferential selection of VP7 gene from a pare nt rotavirus strain SA11 with G serotype 3 (G3) in the sequential pass ages after mixed infection of simian rotavirus SA11 and SA11-human rot avirus single-VP7 gene-substitution reassortants with G1, G2, or G4 sp ecificity. However, it has not been known whether or not VP7 genes der ived from other strains with G3 specificity (G3-VP7 gene) are preferen tially selected in the genetic background of SA11. To address this que stion, mixed infections followed by multiple passages were performed w ith a reassortant SA11-L2/KU-R1 (SKR1) (which possesses VP7 gene deriv ed from G1 human rotavirus KU and other 10 genes of SA11 origin) and o ne of the five G3-rotaviruses, RRV, K9, Yb, AK35, and S3. After the 10 th passage, selection rates of SA11-L2/KU-R1 gene 9 (G1-VP7 gene) and gene 5 (NSP1 gene) reduced considerably (0 to 20.4%) in the clones obt ained from all the coinfection experiments, while all or some of other segments were preferentially selected from SKR1 depending on the pair s of coinfection. When viral growth kinetics was examined, SKR1 exhibi ted better growth and reached a higher titer than any G3 viruses. Alth ough the generated reassortants with VP7 gene and NSP1 gene derived fr om G3 viruses showed almost similar growth kinetics to that of SKR1 du ring the first 20 h of replication, the titers of these reassortants w ere higher than that of SKR1 after 36 h postinfection. The results obt ained in this study suggested that G3-VP7 gene is functionally more ad apted to the genetic background of SA11.