The Morphology and Assembly of Respiratory Syncytial Virus Revealed by Cryo-Electron Tomography

Abstract

Human respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract disease in young children. With repeat infections throughout life, it can also cause substantial disease in the elderly and in adults with compromised cardiac, pulmonary and immune systems. RSV is a pleomorphic enveloped RNA virus in the Pneumoviridae family. Recently, the three-dimensional (3D) structure of purified RSV particles has been elucidated, revealing three distinct morphological categories: spherical, asymmetric, and filamentous. However, the native 3D structure of RSV particles associated with or released from infected cells has yet to be investigated. In this study, we have established an optimized system for studying RSV structure by imaging RSV-infected cells on transmission electron microscopy (TEM) grids by cryo-electron tomography (cryo-ET). Our results demonstrate that RSV is filamentous across several virus strains and cell lines by cryo-ET, cryo-immuno EM, and thin section TEM techniques. The viral filament length varies from 0.5 to 12 μm and the average filament diameter is approximately 130 nm. Taking advantage of the whole cell tomography technique, we have resolved various stages of RSV assembly. Collectively, our results can facilitate the understanding of viral morphogenesis in RSV and other pleomorphic enveloped viruses.

More Than Just a Barrier: The Immune Functions of the Airway Epithelium in Asthma Pathogenesis

“…Larger particles of about 100 nm and above, on the other hand, are efficiently blocked by the PCL (53). Hence, viruses such as RSV, HMPV, influenza and parainfluenza viruses, adenovirus or coronavirus, which are in this size range (64)(65)(66)(67), should be hindered efficiently by the PCL to infect the host. Yet, those viruses often are associated with respiratory infections and asthma exacerbations (68,69).…”

Structures of enveloped virions determined by cryogenic electron microscopy and tomography

“…The matrix protein (M) of MeV has been observed, using whole-cell cryo-ET and STA, to form a well-ordered lattice that lines the inner leaflet of the plasma or virion membrane of MeV-infected cells and released virus particles, respectively (Ke et al, 2018b). The M protein has also been shown to interact with the cytoplasmic or intravirionic tails of the envelope glycoproteins and the helical ribonucleoprotein (RNP) (Ke et al, 2018b).…”

“…The matrix protein (M) of MeV has been observed, using whole-cell cryo-ET and STA, to form a well-ordered lattice that lines the inner leaflet of the plasma or virion membrane of MeV-infected cells and released virus particles, respectively (Ke et al, 2018b). The M protein has also been shown to interact with the cytoplasmic or intravirionic tails of the envelope glycoproteins and the helical ribonucleoprotein (RNP) (Ke et al, 2018b). In contrast, purified MeV virions were observed to contain $30 nm tubular structures composed of M protein tightly coating the inner RNP, but without M protein present at the membrane (Brown et al, 1987;Liljeroos et al, 2011).…”

“…For example, members of Togaviridae, such as Semliki Forest virus (SFV), harbor an icosahedrally symmetric nucleocapsid (Fuller et al, 1995). Finally, many, but not all, enveloped viruses have a matrix protein directly under the envelope (Ke et al, 2018b;Li et al, 2016a).…”

“…of Arenaviridae such as Lassa virus (LASV) , Coronaviridae such as severe acute respiratory syndrome-related coronavirus (SARS-CoV) (Neuman et al, 2006), and Paramyxoviridae such as measles virus (MeV) (Ke et al, 2018b). (I) A filamentous virion with envelope glycoprotein spikes and internal matrix layer.…”