Ultracentrifugation deforms unfixed influenza A virions.

The Journal of general virology (2011-07-29)
Yukihiko Sugita, Takeshi Noda, Hiroshi Sagara, Yoshihiro Kawaoka
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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Osmium tetroxide, ReagentPlus®, 99.8%
Sigma-Aldrich
Osmium tetroxide, Sealed ampule.
Sigma-Aldrich
Osmium tetroxide solution, suitable for electron microscopy, 4% in H2O
Sigma-Aldrich
Osmium tetroxide solution, 4 wt. % in H2O
Sigma-Aldrich
Osmium tetroxide solution, 2.5 wt. % in tert-butanol
Sigma-Aldrich
Osmium tetroxide solution, suitable for electron microscopy, 2% in H2O
Sigma-Aldrich
Osmium tetroxide, ACS reagent, ≥98.0%
Sigma-Aldrich
Os EnCat® 40, extent of labeling: 0.3 mmol/g Os loading