CONTINUOUS PRODUCTION OF MINUTE VIRUS OF MICE BY AN UNTRANSFORMED VARIANT OF FISHER RAT FIBROBLAST (FR3T3)

Many tumour cells are killed by the lytic replication of the autonomou s parvoviruses H-1 and minute virus of mice (MVMp), whereas most untra nsformed cells (although they take up these viruses efficiently) are r esistant, i.e. they do not produce infectious virus and are not lysed. Therefore, cells able to continuously produce large quantities of inf ectious virus have not yet been described. We have isolated such cells from the resistant cell line FR3T3 (Fisher rat fibroblast). These cel ls (called FR3T3C) produce infectious MVMp virions without being detec tably lysed. Furthermore, a persistently infected population (R100FR3T 3C) was generated by repetitive infection of FR3T3C cells with MVMp. I ndeed, R100FR3T3C cells were successfully cultivated for two years and continuously produced infectious virus. Seventeen clones of R100FR3T3 C cells isolated by limiting dilution produced infectious virions, ind icating that in the R100FR3T3C cell population, virus production was n ot limited to a few cells. These cell lines may be useful for the prod uction of MVMp and for the generation of a cell line for the packaging of recombinant viral genomes.