Characteristics of a persistent respiratory syncytial virus infection in HeLa cells

Abstract Persistent infection with respiratory syncytial (RS) virus has been established in HeLa cells. The persistently infected cell line (HeLa RS ) continues to produce virus (RSpi) at low levels after 230 passages during 3 years. The cells are morphologically similar to the parental HeLa cell line, and susceptible to vesicular stomatitis virus, but resist superinfection with standard RS virus (RS wt ). The block in RS wt replication is not at attachment. Although infectious center and immunofluorescence assays suggested that only 5 to 30% of the cells in the culture were infected, 30 of 32 clones isolated from HeLa RS contained some cells with virus antigen and 23 of those clones produced virus. All the clones, including the 2 that appeared not to be infected, were more resistant to RS wt than HeLa. The clones that produced virus were significantly more resistant than the others. RS pi is a small-plaque mutant, but not a temperature-sensitive mutant, of RS wt . Although prior infection of HeLa with RS pi interferes with RS wt replication, the interference appears not to be caused by defective interfering particles, but by RS pi virions. RS pi initiates a persistent infection in HeLa only after a cytolytic phase similar to that which preceded the establishment of HeLa RS .