Molecular Anatomy of Influenza Virus Detailed

[Anne]

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http://www.nih.gov/news/pr/dec2006/niams-29.htm

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</td> </tr> </tbody></table> <table> <tbody><tr> <td>Molecular Anatomy of Influenza Virus Detailed Scientists at the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), part of the National Institutes of Health in Bethesda, Md., and colleagues at the University of Virginia in Charlottesville have succeeded in imaging, in unprecedented detail, the virus that causes influenza.
A team of researchers led by NIAMS? Alasdair Steven, Ph.D., working with a version of the seasonal H3N2 strain of influenza A virus, has been able to distinguish five different kinds of influenza virus particles in the same isolate (sample) and map the distribution of molecules in each of them. This breakthrough has the potential to identify particular features of highly virulent strains, and to provide insight into how antibodies inactivate the virus, and how viruses recognize susceptible cells and enter them in the act of infection.
<table align="left" border="0" cellpadding="2" cellspacing="2" width="185"> <tbody><tr> <td width="360"></td> </tr> <tr> <td align="left">Photo Caption: The three-dimensional structure of influenza virus from electron tomography. The viruses are about 120 nanometers ?
about one ten thousandth of
a millimeter ? in diameter.</td> </tr> </tbody></table> ?Being able to visualize influenza virus particles should boost our efforts to prepare for a possible pandemic flu attack,? says NIAMS Director Stephen I. Katz, M.D., Ph.D. ?This work will allow us to ?know our enemy? much better.?
One of the difficulties that has hampered structural studies of influenza virus is that no two virus particles are the same. In this fundamental respect, it differs from other viruses; poliovirus, for example, has a coat that is identical in each virus particle, allowing it to be studied by crystallography.
The research team used electron tomography (ET) to make its discovery. ET is a novel, three-dimensional imaging method based on the same principle as the well-known clinical imaging technique called computerized axial tomography, but it is performed in an electron microscope on a microminiaturized scale.
The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the Department of Health and Human Services? National Institutes of Health, is to support research into the causes, treatment and prevention of arthritis and musculoskeletal and skin diseases; the training of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. For more information about NIAMS, call the information clearinghouse at (301) 495-4484 or (877) 22-NIAMS (free call) or visit the NIAMS Web site at http://www.niams.nih.gov.
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</td> </tr> </tbody></table> <hr noshade="noshade" size="1"> Reference: Harris A, et al. Influenza virus pleiomorphy characterized by cryoelectron tomography. PNAS 2006;103(50):19123-19127.

here the original " abstract"

Published online before print December 4, 2006, 10.1073/pnas.0607614103
PNAS | December 12, 2006 | vol. 103 | no. 50 | 19123-19127


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BIOLOGICAL SCIENCES / MICROBIOLOGY
Influenza virus pleiomorphy characterized by cryoelectron tomography
<nobr>Audray Harris^*</nobr>, <nobr>Giovanni Cardone^*</nobr>, <nobr>Dennis C. Winkler^*</nobr>, <nobr>J. Bernard Heymann^*</nobr>, <nobr>Matthew Brecher</nobr>, <nobr>Judith M. White</nobr>, and <nobr>Alasdair C. Steven^*^,</nobr>
*Laboratory of Structural Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892; and Department of Microbiology, University of Virginia, Charlottesville, VA 22908
Edited by Peter Palese, Mount Sinai School of Medicine, New York, NY, and approved October 13, 2006 (received for review September 7, 2006)

<!-- ABS --> Influenza virus remains a global health threat, with millionsof infections annually and the impending threat that a strainof avian influenza may develop into a human pandemic. Despiteits importance as a pathogen, little is known about the virusstructure, in part because of its intrinsic structural variability(pleiomorphy): the primary distinction is between sphericaland elongated particles, but both vary in size. Pleiomorphyhas thwarted structural analysis by image reconstruction ofelectron micrographs based on averaging many identical particles.In this study, we used cryoelectron tomography to visualizethe 3D structures of 110 individual virions of the X-31 (H3N2)strain of influenza A. The tomograms distinguish two kinds ofglycoprotein spikes [hemagglutinin (HA) and neuraminidase (NA)]in the viral envelope, resolve the matrix protein layer liningthe envelope, and depict internal configurations of ribonucleoprotein(RNP) complexes. They also reveal the stems that link the glycoproteinectodomains to the membrane and interactions among the glycoproteins,the matrix, and the RNPs that presumably control the buddingof nascent virions from host cells. Five classes of virions,four spherical and one elongated, are distinguished by featuresof their matrix layer and RNP organization. Some virions havesubstantial gaps in their matrix layer ("molecular fontanels"),and others appear to lack a matrix layer entirely, suggestingthe existence of an alternative budding pathway in which matrixprotein is minimally involved.

envelope glycoproteins | matrix protein | ribonucleoprotein particles | virus assembly | virus structure