[Establishment and analysis of cell culture infected persistently with JC virus].

JC polyomavirus (JCV) is the causative agent of a demyelinating disease in the central nervous system, known as progressive multifocal leukoencephalopathy. Since it is difficult to propagate JCV in vitro, many laboratories have attempted to develop cell lines permissive for replication of JCV. It was recently reported that serial passage of JCV (strain Mad-1) in a human neuroblastoma cell line (IMR-32 cells) generated JCV variants (M1-IMRa, -IMRb, -IMRc) adapted to the growth in IMR-32 cells. We obtained a persistently-infected cell culture, designated JCI cells, by continued subcultivation of IMR-32 cells which had been infected with these adapted variants. To understand the mechanism by which the carrier state was maintained, we molecularly cloned multiple JCV DNAs from JCI cells. Sequencing of the cloned DNAs revealed that a majority of the clones had the same altered regulatory sequence which was probably generated from M1-IMRa. A DNA transfection experiment using a chimeric JCV DNA, in which the regulatory region was derived from JCI and the other region from Mad-1, showed that the JCI regulatory region was less efficient in inducing virus production in IMR-32 cells. Therefore, it could be concluded that the regulatory region is primarily important for maintaining the carrier state in JCI cells. Although JCI cells contained a significant amount of JCV, the yield of JCV could remarkably be increased by incubating a confluent JCI culture in a medium with a low serum concentration. Thus, JCI cells should greatly facilitate the production of JCV for future studies of the virus.