Immortality of cell cultures derived from brains of mice and hamsters infected with Creutzfeldt-Jakob disease agent.

Isolates from six patients with Creutzfeldt-Jakob disease (CJD) were injected into various strains of hamsters and mice, and the infective agent was propagated. Serially passaged cultures were established from these CJD agent-infected brains and from uninfected control brains. All healthy cultures (21 out of 21) from CJD agent-infected brains became immortal and/or transformed. In contrast only 3 out of 13 normal brain cultures became immortal, and the rest died out with serial propagation in vitro. The fact that permanent cell lines were readily derived from multiple rodent strains and all CJD isolates tested suggests that a transforming capability is an intrinsic property of CJD agents. This conclusion is supported by demonstrations of in vitro cell transformation by CJD infectious brain fractions. Although the molecular mechanism of transformation events associated with the CJD agent is not presently known, a provocative possibility is that the CJD agent has a direct effect on the host genome by mechanisms analogous to those known for slowly oncogenic retroviruses.