Persistent infections in salmonid fish cells with infectious pancreatic necrosis virus (IPNV)*

Abstract. Two cell lines that are persistently infected with IPN virus have been established. Viral persistence in the cultures was demonstrated by the detection of infectious virus (10²-10^5,5 TCID/ml₅₀) in the culture fluids, by specific immunofluorescence, and by their resistance to superinfection by homologous virus. The growth, rate of these cells was indistinguishable from normal, uninfected cells. Virus stocks harvested from persistently infected cultures contained a greater proportion of defective, interfering particles than those from lytically infected cells which suggests that these particles may be responsible for the maintenance of these carrier cultures.