The significance of positive controls in testing the oncogenic potential of cell material for virus vaccine production.

For all the parts involved in the production and control of virus vaccine it is important that controls of the cell material should be carried out under optimal conditions for the detection of any abnormal characteristics of the cells. The experiments reported here attempt to establish some of the optimal parameters for testing out the tumor-inducing properties of a human diploid cell culture. All experiments were carried out on 6-week old Syrian hamsters and the main objectives were: (i) to devise an optimal immunosupression scheme and (ii) to find a more suitable positive control for testing the oncogenic potential of the human diploid cells. The anti-hamster lymphocyte serum proved to be a more potent immunosuppresser than hydrocortisone succinate as seen from the development of tumors following injections with KB cells; this scheme was subsequently used in assessing the usefulness of KB and Swiss-12 cells as positive controls. The experiments lend support to the suggestion that a heteroploid fibroblastic culture (such as Swiss-12) should become a standard positive control since not only are the tumors so obtained larger and less prone to early necrosis but, more important, they bear a closer resemblance to the kind of tumors likely to be induced by the diploid cell cultures being tested.