Morphology of Influenza B/Lee/40 Determined by Cryo-Electron Microscopy

Abstract

Cryo-electron microscopy projection image analysis and tomography is used to describe the overall architecture of influenza B/Lee/40. Algebraic reconstruction techniques with utilization of volume elements (blobs) are employed to reconstruct tomograms of this pleomorphic virus and distinguish viral surface spikes. The purpose of this research is to examine the architecture of influenza type B virions by cryo-electron tomography and projection image analysis. The aims are to explore the degree of ribonucleoprotein disorder in irregular shaped virions; and to quantify the number and distribution of glycoprotein surface spikes (hemagglutinin and neuraminidase) on influenza B. Projection image analysis of virion morphology shows that the majority (∼83%) of virions are spherical with an average diameter of 134±19 nm. The aspherical virions are larger (average diameter = 155±47 nm), exhibit disruption of the ribonucleoproteins, and show a partial loss of surface protein spikes. A count of glycoprotein spikes indicates that a typical 130 nm diameter type B virion contains ∼460 surface spikes. Configuration of the ribonucleoproteins and surface glycoprotein spikes are visualized in tomogram reconstructions and EM densities visualize extensions of the spikes into the matrix. The importance of the viral matrix in organization of virus structure through interaction with the ribonucleoproteins and the anchoring of the glycoprotein spikes to the matrix is demonstrated.

Identification of Influenza A/PR/8/34 Donor Viruses Imparting High Hemagglutinin Yields to Candidate Vaccine Viruses in Eggs

“…The impact of virion morphology on the stability of particles during manufacturing is not well understood but vaccine manufacturers prefer candidate vaccine viruses that yield spherical particles [47]. Unstable filamentous virions are produced as a result of mutations in the M2 cytoplasmic tail [48].…”

Identification of cis-acting packaging signals in the coding regions of the influenza B virus HA gene segment

“…Further experiments using labelled vRNPs (Lakdawala et al, 2014) could address this. Furthermore, while electron microscopic comparisons of vRNP structural arrangement in influenza A and B virions might suggest different mechanisms of genome packaging between the two viruses (Katz et al, 2014;Noda et al, 2006), our results suggest a similar mechanism of cis-acting RNA signal-mediated packaging is employed by both viruses. The difference in vRNP arrangement is likely due to vRNA-vRNA interactions differing between the two viruses, leading to the more twisted vRNP complex observed in influenza B viruses.…”

“…Electron microscopic analysis of influenza A virus particles demonstrated that the vRNPs are arranged in a highly ordered '7+1' orientation in which all segments align in a circular fashion with one segment in the centre (Noda et al, 2006). However, recent evidence suggests that this does not occur in influenza B viruses, as the vRNPs appear to twist around each other (Katz et al, 2014). This suggests that influenza A and B viruses potentially adopt different mechanisms for genome packaging.…”

Classification of polyhedral shapes from individual anisotropically resolved cryo-electron tomography reconstructions

“…Shape identification can thus be achieved by classifying the observed incomplete PG (which can be subject to measurement error) to one of the reference polyhedra. Apart from BMCs, these techniques could potentially also be applied to other biological objects exhibiting polyhedral structure, such as several types of viruses [ 1 , 7 , 9 , 10 ] and protein complexes such as clathrin [ 11 ].…”