Peculiarities of the virus-host cell relationship in a calf kidney cell line persistently infected with measles virus.

Persistent infection with measles virus established in a calf kidney cell line differed in some features from other measles virus carrier systems. After a variable life span, ranging from 50 to 1100 days, six of the chronically infected cell lines showed an evolution towards lytic infection. Only one of these lines, the K-2 cell line, exhibited marked morphological, growth and chromosomal alterations suggesting in vitro cellular transformation. The transformed K-2 cells released infectious measles virus with several modified biological parameters. Persistent infection was not due to the accumulation of thermosensitive mutants or defective particles. The role of the host-cell factor and of the selection of the virus population during its passage in RV cells are discussed.