Persistent infection of cultured mammalian cells by Japanese encephalitis virus.

Persistent infections were established by serial undiluted passage of flavivirus Japanese encephalitis virus in a line of rabbit kidney cells (MA-111). The persistently infected cells resembled uninfected cells in most respects. Low levels of infectious virions were released from a small percentage of cells, and a larger and more variable percentage was shown to possess viral antigen by fluorescent-antibody staining. Released viruses were shown to interfere with replication of wild-type Japanese encephalitis virus. Persistently infected MA-111 cells could not be superinfected with homologous wild-type Japanese encephalitis virus but could be superinfected with two heterologous viruses. Transfer of cell culture medium from persistently infected MA-111 cells to a line of African green monkey kidney cells (Vero) resulted in similar persistent infections in the latter cells. Temperature sensitivity and host-cell interferon production were not involved in establishment or maintenance of persistence. Determination of ratios of physical particles to infectious particles revealed that many defective, noninfectious viruses were present, suggesting that defective interfering particles may be responsible for persistency.