Isolation and characterization of BK virus-transformed hamster cells

BK virus (BKV) was used to transform baby hamster kidney (HK) and hamster embryo fibroblast (HE) cells in culture. Six clones of each of the BKV-transformed HK and HE cells were isolated and characterized with respect to a number of biological properties. None of the cloned lines was found to produce infectious BKV, and all 12 lines were shown to contain BKVT antigen, to have a lower serum dependency for growth and to grow to higher saturation densities than the corresponding untransformed cells, to have higher plating efficiencies than control cells, to have acquired the ability to produce colonies in soft agar, and to produce progressively growing tumors when injected subcutaneously into weanling hamsters. Differences were found to exist among the cell lines of each group with respect to these parameters, and, in general, transformed HK cells have a lower serum dependency, grow to higher saturation densities, and have higher plating efficiencies and a greater capacity to produce colonies in soft agar than do the transformed HE cells. Infection of secondary cultures of HE cells with various input multiplicities of BKV showed that transformation is a multiplicity-dependent phenomenon and can be achieved with an input multiplicity as low as 3 PFU/cell.