Persistent infection of rabies virus (HEP-Flury strain) in human neuroblastoma cells capable of producing interferon

Abstract

Apparent interferon-mediated persistent infection of rabies virus (HEP-Flury strain) was established in a human neuroblastoma SYM-I (clone K-104) cell line, which had the ability to produce interferon. This infection produced variable but small amounts of progeny virus and interferon (up to 100 IU/ml), and resisted superinfection with vesicular stomatitis virus (VSV) and Sindbis virus as well as homologous rabies virus. The treatment of this infection with anti-interferon antibody stimulated virus replication and extensive c.p.e. However, some cells survived and grew rapidly without any sign of c.p.e. These produced increased amounts (100 to 1000 times) of infectious and DI particles in the presence of anti-interferon antibody, becoming susceptible to superinfection with VSV but remaining resistant to the original rabies virus. Small plaque mutants appeared and replaced the original virus during the long-term cultivation of the persistent infection. Several mutants tested were all identified as Sdi (DI-resistant) mutants, suggesting that the persisting viruses were endowed by the Sdi mutation with a selective advantage over the original virus even in interferon-mediated persistent infections.