Persistent infections of green monkey kidney cells initiated with temperature-sensitive mutants of simian virus 40

Abstract

An early SV40 temperature-sensitive ( ts) mutant, tsA58, and a late mutant, tsB11, each expressed homotypie interference in CV-1 cells coinfected with WT. Interference required the functional activities of the mutant genomes and resulted from a competitive interaction between the mutants and WT. Another late mutant, tsD101 did not display interference activity. Nevertheless, each of the is mutants promoted the survival of CV-1 cells coinfected with WT at 37° and, consequently, facilitated the establishment of persistent infections. Each of the mutants was also more able than WT to establish persistent infections under conditions of single infection. Only a few percent of the cells in these persistent infections produced the SV40 T or V antigens and clonal isolates from these systems contained both antigen-producing and nonproducing cells. These systems were resistant to superinfection with WT SV40 but were completely susceptible to vesicular stomatitis virus. There was a rapid selection for ts + virus in the persistent infections initiated by mixed infection with the ts mutants and WT. The proportion of ts + virus also increased, although somewhat more slowly, in the systems initiated by infection with the mutants alone. Defective interfering (DI) particles were detected in some stocks by yield reduction assays. Many viral genomes in stocks displaying DI particle activity contained multiple BglI cleavage sites, indicating that they possess reiterations of the origin for DNA replication.