title: Ultracentrifugation deforms unfixed influenza A virions.
abstract: Negatively stained influenza virions sometimes show irregular morphology and are often referred to as pleomorphic. However, this irregular morphology has not been visualized when ultrathin-section transmission and scanning electron microscopies are used. This study focused on the effects of ultracentrifugation on influenza A virion morphology, as negative staining often involves ultracentrifugation to concentrate or purify virions. The morphologies of unfixed, glutaraldehyde-fixed and osmium tetroxide-fixed virions were quantitatively compared before and after ultracentrifugation, and it was found that, without chemical fixation, approximately 30% of virions were altered from oval to irregular shapes following ultracentrifugation. By contrast, most glutaraldehyde-fixed virions remained uniformly elliptical, even after ultracentrifugation. When a virus with an 11 aa deletion at the C terminus of its M2 cytoplasmic tail was ultracentrifuged, its morphology was appreciably deformed compared with that of the wild-type virus. These results demonstrate that the native morphology of influenza A virions is regular but is disrupted by ultracentrifugation, and that the cytoplasmic tail of M2 is important for virion integrity.
authors.affiliation: Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan.
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Sugita
authors.affiliation: Department of Special Pathogens, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Noda
authors.affiliation: Medical Proteomics Laboratory, Institute of Medical Science, University of Tokyo, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sagara
authors.affiliation: ERATO Infection-Induced Host Responses Project, Saitama 332-0012, Japan.|Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan.|Department of Special Pathogens, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan.|Department of Pathological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kawaoka
mesh_terms: D000818:Animals; D002642:Chick Embryo; D005404:Fixatives / Q000378:metabolism; D005976:Glutaral / Q000378:metabolism; D009980:Influenza A virus / Q000302:isolation & purification / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009993:Osmium Tetroxide / Q000378:metabolism; D014461:Ultracentrifugation; D014771:Virion / Q000302:isolation & purification / Q000648:ultrastructure*
chemical_list: D005404:Fixatives; D009993:Osmium Tetroxide; D005976:Glutaral