Rescue of BKV from BKV-transformed hamster, rat, and mouse cells: correlation with levels of nonintegrated viral DNA.

Infectious BKV was rescued from 39 of 40 lines of virus-free, BKV-transformed hamster, rat, and mouse cells, which had been either maintained continuously in culture or reestablished in culture after one or more passage in the appropriate host, by Sendai virus-catalyzed fusion with permissive cells. Striking differences were observed among the 39 lines with respect to the efficiency of virus rescue. Fourteen of the lines were examined for the presence of nonintegrated viral DNA by dot-blot hybridization. The values obtained, which ranged from less than 1 to 2880 viral genome equivalents/cell, reveal a strong correlation between the efficiencies with which BKV can be rescued from these lines and the amounts of free viral DNA that they contain.