PREFERENTIAL SELECTION OF SPECIFIC ROTAVIRUS GENE SEGMENTS IN COINFECTION AND MULTIPLE PASSAGES WITH REASSORTANT VIRUSES AND THEIR PARENTALSTRAIN

We previously reported non-random selections of human rotavirus (HRV) Wa genes 2 and 5 in reassortant formation between HRV strains Wa and H N126 under selection pressure with neutralizing monoclonal antibodies. In order to study whether or not these genes are preferentially selec ted in the genetic background of a parental strain HN126 in vitro with out selection pressures, coinfection and multiple passage experiments were performed between HN126 and one of three reassortants, C1, C1T an d C1F; C1 possessed genes 2 and 5 derived from Wa and the other genes derived from HN126, while C1T and C1F were single gene reassortants ha ving Wa gene 2 or Wa gene 5 in the genetic background of HN126, respec tively. When MA-104 cells were coinfected with the same infectious uni ts of HN126 and C1, Wa genes 2 and 5 of reassortant C1 became predomin ant within 10 repeated passages, although Wa gene 5 was selected more preferably than Wa gene 2. Similar results were obtained under differe nt experimental conditions in which different doses of parental strain s or different type of cells were used. Also, in coinfections of MA-10 4 cells with HN126 and C1T, or HN126 and C1F, Wa gene 2 or Wa gene 5 b ecame predominant at the sixth passage. Analysis of viral growth curve s indicated that two reassortants, C1 and C1F, replicated to a titre h igher than HN126, while no difference in viral growth was observed bet ween C1T and HN126. These results indicated that in the genetic backgr ound of HN126, Wa gene 5 might provide viruses with a growth advantage compared with its HN126 counterpart, while Wa gene 2 might be prefere ntially selected into reassortant clones through its greater functiona l capacity for assortment during viral replication.