Characterziation of JC polyomavirus derived from COS-IMRb cells.

JC polyomavirus (JCPyV) causes progressive multifocal leukoencephalopathy (PML), a demyelinating disease of the central nervous system in immunocompromised patients. Study of PML-type JCPyV in vitro has been limited due to difficulty in efficient propagation of the virus in cultured cells. In this study, we carried out long term cultivation of COS-7 cells (designated as COS-IMRb cells) transfected with PML type M1-IMRb, an adapted viral DNA with a rearranged non-coding control region (NCCR). The JCPyV derived from COS-IMRb cells was characterized by analyzing viral replication, amount of virus by hemagglutination (HA), production of viral protein 1 (VP1), and structure of the NCCR. HA assays indicated that a high amount of PML type JCPyV was present in COS-IMRb cells. Immunostaining showed that VP1-positive cells were a small population in COS-IMRb cells that represented a JCPyV carrier cell culture. Sequencing analysis of the NCCR of JCPyV after long-term cultivation showed that the NCCR of M1-IMRb was conserved in COS-IMRb cells without any point mutation. The JCPyV genomic DNA derived from a clone of COS-IMRb-3 cells was detected by Southern blotting as a single band of approximately 5.1 kbp without deletion. These findings support that COS-IMRb-3 cells may offer a useful tool for screening anti-JCPyV drugs.