Replication of Influenza A and B Viruses in Human Diploid Cells

Abstract

Under optimal conditions, of high multiplicities of infection and with trypsin included in the medium throughout the incubation period, high yields of infectious influenza A and B viruses (106-5 p.f.u./ml) and of antigenically active haemagglutinin (HA) (1 ug/HA/106 cells) were produced in human diploid MRC-5 cells. Budding virus particles were seen as spherical or short rod-like protrusions on the surface of the infected cells, and also on cell filopodia. Virus-induced cytoplasmic and nuclear inclusions were present in infected cells. This virus—human cell system may be suitable for studies of influenza virus persistence and for production of immunologically active HA antigen.