In vitro transformation elicited by Creutzfeldt-Jakob-infected brain material

Previous studies indicated that tissue culture cells derived from Creutzfeldt-Jakob disease (CJD) brains possess neoplastic properties. In order to see if CJD brain material could itself transform cells in vitro, BALB/C-3T3 and normal hamster brain monolayer cultures were exposed to whole brain homogenate or synaptosomal-mitochondrial fractions derived from CJD or control brains. Cells were exposed for seven days to CJD or control brain material, washed, and then passaged at weekly intervals. Transformation was evaluated by loss of contact inhibition, replication of cells with absent or low serum content of the medium and significant colony formation in soft agar. Seven parallel experiments were done, and six were viable. All cultures exposed to CJD material containing greater than or equal to 10(4) LD50 infectious units were positive for transformation (five of six studies); the single negative experiment contained only 2 X 10(3) infectious units. Definitive transformation could be observed at 12-16 weeks after application of both mouse and hamster CJD material. BALB/C-3T3 cells exposed to control hamster or mouse brain material were studied for greater than 120 passages in vitro and showed no comparable changes or evidence of spontaneous transformation, i.e. they required serum for replication and produced essentially no colonies in soft agar. Similarly, a normal adult hamster brain culture exposed to control brain material showed no evidence of transformation, whereas the identically passaged normal brain culture exposed to CJD material not only became a permanent line, able to grow in soft agar, but also was capable of producing tumors in nude mice. Thus CJD transformation was not confined to special potentials of "permanent" BALB/C-3T3 cells. These experiments suggest that a genomic alteration can be effected by CJD material.