Structure, dynamics and nanomechanics of wild-type and alpha-variant SARS-CoV-2 virions

Abstract

SARS-CoV-2 is the agent behind the COVID-19 pandemic. The virus displays a corona-shaped layer of spikes which are important in the infection process. Variants of the virus possess increased infectivity, but the exact mechanisms behind this phenomenon are not fully understood. Here we imaged and mechanically manipulated individual, wild (Wuhan)-type and alpha (British)-variant SARS-CoV-2 virions with atomic force microscopy. We observed that the virion surface displays a dynamic brush owing conceivably to the flexibility and rapid rotational and translational motion of spikes. The virus particles are highly compliant, and they recover from severe mechanical perturbations. The global structure of the virions is surprisingly temperature resistant, but the spikes are progressively removed from the virus surface upon increasing the thermal exposure. The alpha variant virions appear to be significantly smaller in their radii than the wild type virus particles. Considering that the surface and volume of the spherical virions scale with the second and third power of the radius, respectively, our results reveal an increased specific surface (surface/volume ratio) in the alpha-variant virus particles. Thus, while the infectivity of SARS-CoV-2 relies on the dynamics and the mechanics of the virus, it may be influenced by the specific surface as well. SARS-CoV-2 is the agent behind the COVID-19 pandemic. The virus displays a corona-shaped layer of spikes which are important in the infection process. Variants of the virus possess increased infectivity, but the exact mechanisms behind this phenomenon are not fully understood. Here we imaged and mechanically manipulated individual, wild (Wuhan)-type and alpha (British)-variant SARS-CoV-2 virions with atomic force microscopy. We observed that the virion surface displays a dynamic brush owing conceivably to the flexibility and rapid rotational and translational motion of spikes. The virus particles are highly compliant, and they recover from severe mechanical perturbations. The global structure of the virions is surprisingly temperature resistant, but the spikes are progressively removed from the virus surface upon increasing the thermal exposure. The alpha variant virions appear to be significantly smaller in their radii than the wild type virus particles. Considering that the surface and volume of the spherical virions scale with the second and third power of the radius, respectively, our results reveal an increased specific surface (surface/volume ratio) in the alpha-variant virus particles. Thus, while the infectivity of SARS-CoV-2 relies on the dynamics and the mechanics of the virus, it may be influenced by the specific surface as well.