Electron Tomography Imaging of the Pandemic H1N1 2009 Influenza Virus
Influenza A virus shows variations in its morphology from being uniform 70 nm enveloped particles to highly pleiomorhic forms extending upto microns. It has been consistently observed that viruses from early passages are filamentous and subsequently adopt a consistent spherical morphology, except for the influenza A/Udorn/72/H3N2 isolate. However, the relation between pleiomorphism and virulence remains incompletely understood. In the present study we examined the morphological features of a pandemic influenza A/H1N1/2009 virus isolate from India grown in second and third passages in both cell culture and eggs using transmission electron microscopy and electron tomography to study the morphology and reconstruct the 3D organization of the virion. The pH1N1 2009 virus we studied showed predominance of extreme pleiomorphic forms in cell cultures when compared with the virus grown in eggs upto the third passage. Our results showed that the spherical forms of the virus had a size range of 110 ± 10 nm with an axial ratio of 1:4. The highly pleomorphic forms exceeded 200 nm. The average length of the hemagglutinin (HA) was 12 nm and the neuraminidase (NA) 15 nm with a 5 nm wide pear-shaped terminal head. Contacts between HA-NA could be visualized in 3D reconstructions. Reconstruction of the matrix protein layer showed discontinuity in the filamentous forms and aggregation towards the terminal ends. Molecular genetic analysis of key amino acids in the helix six domain of the M1 protein of this virus showed K102E and R105K mutation in both the egg and cell culture derived isolates. This is the first report of direct visualization of a pandemic human influenza virus in early isolation stages by electron tomography.
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Document Type: Research Article
Publication date: 2012-03-01
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- Journal of Advanced Microscopy Research (JAMR) provides a forum for rapid dissemination of important developments in high-resolution microscopy techniques to image, characterize and analyze man-made and natural samples; to study physicochemical phenomena such as abrasion, adhesion, corrosion and friction; to perform micro and nanofabrication, lithography, patterning, micro and nanomanipulation; theory and modeling, as well as their applications in all areas of science, engineering, and medicine.
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