Ultrahigh-resolution scanning electron microscopy of MDCK cells infected with influenza viruses

Ultrahigh-resolution scanning electron microscopy of MDCK cells infected with influenza viruses was carried out by the uncoated uranyl acetate staining preparation method. Ridge-like protrusions were detected on virus particles and were considered to be an indication of aggregated glycoprotein spikes. Bundles of filamentous virus particles along with bacillary virus particles were encountered on MDCK cells infected with freshly isolated strains of type A virus. Filamentous virus particles that were twisted like ropes were observed on MDCK cells infected with strains of type B virus.