The Organisation of Ebola Virus Reveals a Capacity for Extensive, Modular Polyploidy

Abstract

BackgroundFiloviruses, including Ebola virus, are unusual in being filamentous animal viruses. Structural data on the arrangement, stoichiometry and organisation of the component molecules of filoviruses has until now been lacking, partially due to the need to work under level 4 biological containment. The present study provides unique insights into the structure of this deadly pathogen.Methodology and Principal FindingsWe have investigated the structure of Ebola virus using a combination of cryo-electron microscopy, cryo-electron tomography, sub-tomogram averaging, and single particle image processing. Here we report the three-dimensional structure and architecture of Ebola virus and establish that multiple copies of the RNA genome can be packaged to produce polyploid virus particles, through an extreme degree of length polymorphism. We show that the helical Ebola virus inner nucleocapsid containing RNA and nucleoprotein is stabilized by an outer layer of VP24-VP35 bridges. Elucidation of the structure of the membrane-associated glycoprotein in its native state indicates that the putative receptor-binding site is occluded within the molecule, while a major neutralizing epitope is exposed on its surface proximal to the viral envelope. The matrix protein VP40 forms a regular lattice within the envelope, although its contacts with the nucleocapsid are irregular.ConclusionsThe results of this study demonstrate a modular organization in Ebola virus that accommodates a well-ordered, symmetrical nucleocapsid within a flexible, tubular membrane envelope.

Aquabirnavirus polyploidy: a new strategy to modulate virulence?

“…Polyploidy has also been found in several non-icosahedral virus families (e.g. families Paramyxoviridae, Orthomyxoviridae and Filoviridae), which use it to modulate their virulence (Enami et al, 1991;Rager et al, 2002;Beniac et al, 2012). Therefore, our first objective was to determine whether aquabirnaviruses could also be polyploid.…”

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“…The viral RNA genome is encapsidated by the NP and together with L, the L cofactor VP35 and the transcriptional activator VP30, as well as VP24, which form a central nucleocapsid in the virus particle. 10 The structure of Ebola virus NP, VP35, VP30 and L are responsible for replication and transcription of viral RNA, while VP40 and VP24 are responsible for assembly, budding and release of virion particles.…”

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“…It should be noted that from the physical viewpoint most of viruses can be considered as nanoparticles, since their linear dimensions are close to 100 nm [12][13][14]. As it is well known, viruses have various shapes, so the spherical shape was chosen as the simplest one to be calculated, and since the shape of such widespread viruses as Human Immunodeficiency Virus (HIV) and Influenza Virus is the same.…”