Measles virus persistence in a hamster brain cell line: cyclical fluctuation of viral expression during serial passages.

Measles virus persistence in a hamster brain cell line was examined for the appearance of viral antigens and for the synthesis of infectious virus, viral RNA, and virus-specific proteins during 19 serial passages. Cyclical fluctuation was detected at all levels of measles virus replication. After reaching the maximal activity at the passages 9 to 11 viral synthesis diminished rapidly, being lowest after 2 to 3 subsequent passages. No release of infectious virus was detected at the passages 14 and 15 and only 20% of the cells contained measles virus antigens when tested by immunofluorescence. After the nonproductive phase, the cells released virus again and the number of antigen-positive cells increased. The alternation in the amount of the measles virus-specific proteins and viral RNA correlated directly with the parameters mentioned above. No apparent defects in the synthesis of individual viral proteins were observed.