Persistent infection with human cytomegalovirus in a lymphoblastoid cell line.

Cells from a line of human lymphocytes originating from a leukemic patient were persistently infected with human cytomegalovirus (HCMV). The infected culture has persistently yielded HCMV with titers ranging from 2 × 10⁴ to 3 × 10⁵ PFU/ml over a period of 1 year. Infectious center and fluorescent antigen assays and electron microscopic examination indicated that 1–10% of the cells were infected. It appears that persistent infection is due to a balance between release of virus and the growth of uninfected cells rather than to a defective or temperature-sensitive mutant of HCMV. The treatment of persistently infected cultures with anti-HCMV serum resulted in curing the virus infection. Cured cells in culture grew at the same rate as normal uninfected cells and became resistant to HCMV infection and relatively resistant to HSV infection.