Establishment and characterization of a carrier cell culture producing high titres of polyoma JC virus.

This report concerns a carrier cell culture (designated JCI) infected persistently with JC virus (JCV). Immunostaining with an anti-JCV antiserum revealed that JCI was a carrier culture in which only a small fraction of the cells (approximately 1.5%) produced the virus. The JCV titre was increased strikingly by incubating confluent JCI cells for 4-6 days in medium containing a low concentration of fetal bovine serum (2%). Viral genomes cloned from the persistently infected JCI cells were heterogeneous with respect to size, but most clones had an alteration of the same regulatory region (designated CR-JCI). Transfection experiments with a chimeric JCV DNA (Mad-1/CR-JCI), in which the regulatory region was CR-JCI and the other region was derived from an infectious JCV (Mad-1) DNA, showed that CR-JCI was less efficient in inducing viral growth than the regulatory regions of IMR-32-adapted JCVs. The transfected cells could be readily subcultured, and they continued to produce JCV. It is concluded that a decrease in the activity of the JCV regulatory region is of importance for the maintenance of the carrier state of JCI cells.