An electron microscopic study of changes at the surface of influenza-infected cells as revealed by ferritin-conjugated antibodies.

The sequence of events associated with liberation of the PR8 strain of influenza virus at the surface of chorioallantoic membranes (CAM) was studied by means of ferritin-conjugated antibodies, one of which was specific for the V antigen of the virus and the other for host cell antigen. With an input multiplicity of approximately 0.001 per cell, viral progeny were first detected by infectivity titrations and electron-microscopy after 12 and 13 hours, respectively. As infection proceeded, viral antigen progressively accumulated at the cell surface, while host cell antigen diminished in amount. It was concluded that normal host cell protein did not constitute an integral part of the surface structure of the virus.