Multiplication and plaque assay of influenza viruses in a continuous cell line (G2) of human origin

Summary Serial propagation of strains of all types of influenza viruses proved to be possible in a continuous cell line derived from a human bone carcinoma. This is the second continuous human cell line in which influenza viruses can be serially propagated. The concentration of influenza viruses in this cell line, G2, was essentially equivalent to the infectivity obtained in embryonated eggs. Clear-cut cytopathogenicity of the infected G2 cells did not occur. Viral antigenicity as determined by serum-virus hemagglutination-inhibition tests was not altered by the cell culture passage. Plaque assay of influenza viruses which had been serially propagated in G2 cell cultures was a simple procedure and the results were reproducible enough for practical application.