Rotavirus temperature-sensitive mutants are genetically stable and participate in reassortment during mixed infection of mice

Abstract

Mixed and single infections of 7-day-old suckling mice with SA11 temperature-sensitive (ts) mutants and RRV wild-type were examined to determine if selection against ts mutations occurred in the suckling mouse model. Single infections with ts mutants indicated that mutant replication was restricted relative to wild-type and that disease was similarly reduced. Revertant (ts+) progeny did not appear to be selected during infection. Mixed infection with ts mutant and RRV wild-type revealed a reduction in the replication of RRV suggesting that the ts mutants displayed an interference phenotype in vivo similar to that observed in vitro. However, reduced replication of the RRV parent in mixed infection did not result in a significant reduction in disease relative to RRV infection. When progeny from the mixed infections were isolated at the permissive temperature both ts and ts+ progeny were observed, and the genome segments of these progeny segregated in a manner consistent with the temperature phenotype of each progeny clone and the location of the ts mutation determined in vitro. Selection of ts+ progeny from mixed infected mice at nonpermissive temperature yielded either the RRV parent or ts+ reassortants. The segregation of genome segments in these ts+ reassortant progeny was consistent with the location of the ts lesion determined previously in vitro. These results indicate the following with respect to infection of suckling mice with ts mutants: (1) ts lesions are genetically stable and are not selected against during in vivo infection, (2) ts mutants cause disease with reduced severity, (3) ts mutants interfere with the replication of wild-type virus in vivo but not with the severity of disease, and (4) mixed infection of suckling mice may be useful in genetic studies with rotaviruses not adapted to growth in cultured cells.