CHANGING VIRAL SUSCEPTIBILITY OF A HUMAN CELL LINE IN CONTINUOUS CULTIVATION : I. PRODUCTION OF INFECTIVE VIRUS IN A VARIANT OF THE CHANG CONJUNCTIVAL CELL FOLLOWING INFECTION WITH SWINE OR N-WS INFLUENZA VIRUSES

During its serial transfer and cultivation in this laboratory, a human conjunctival cell line (Chang) was observed to change in morphology. Concurrently no change was noted in the susceptibility of the cells to viruses capable of infecting the original cell line. However, it was noted that the derived variant cell line had acquired susceptibility to the induction of cytopathic effects and incomplete virus formation by several strains of influenza viruses. It was then discovered that swine influenza virus and the N-WS strain of influenza A virus could be serially propagated in the derived cell line with production of infective virus. The swine virus required adaptation, but the N-WS strain did not. N-WS and swine influenza viruses multiply with infective virus formation only in the variant conjunctival cell and in no other cell line. Antigenic, cytologic, and virologic evidence is presented that the influenza virus-susceptible variant cell is of human origin and is not a contaminating cell exogenously introduced. Transition of a cell line from complete insusceptibility to susceptibility to virus infection and multiplication has not been described previously.