Chronic non-cytopathic infection of human continuous cell lines with mumps virus.

Chronic infection with a vaccine strain of mumps virus (MV) was produced and studied in human cell cultures L-41 and HEp-2. The establishment and course of the infection was not accompanied by cytopathic changes. Among probable protective factors (mechanisms) interferon (IFN) was detected in L-41 culture and defective interfering particles in either cell culture. Their role in the establishment and maintenance of chronic infection was not confirmed, however.