Coronavirus shape alters infection ability

SARS-CoV-2, the virus responsible for the COVID-19 pandemic, is typically portrayed as a sphere with protruding spikes. However, under a microscope, these viruses are more often elliptical than circular.

Kanso et al. developed a theory to examine how the shape of SARS-CoV-2 affects its transport properties, and thus its ability to infect a cell. They studied a range of possible shapes because it’s unknown whether coronavirus is prolate (a spheroid elongated at the poles), oblate (a spheroid flattened at the poles), or a mixture of both.

The virus is non-motile and relies on the rotational component of its own random thermal motion to initiate infection. The authors calculated rotational diffusivity, a property that determines how well a virus aligns its spikes to targets on a cell’s surface, for viruses with different shapes and numbers of spikes. They found rotational diffusivity decreases for oblate and prolate viruses.

“The shape of the COVID particle matters because each shape gives a different value for the rotational diffusivity of the virus,” said author Mona Kanso. “The virus moves from place to place in our bodies through the blood. But to infect a cell, rotational diffusivity is what tells us how fast, how slow, and whether the virus can attach.”

While a suspension of purely spherical coronaviruses is Newtonian, or has a constant viscosity, these models showed prolate or oblate viruses will form a non-Newtonian suspension.

“This goes hand in hand with the virus’s ability to infect,” said author Jeff Giacomin.

In the body, coronaviruses tend to stick to each other. Next, the researchers will study properties of these SARS-CoV-2 interdigitated clusters.

Source: “Coronavirus pleomorphism,” by M. A. Kanso, M. Naime, V. Chaurasia, K. Tontiwattanakul, E. Fried, and A. J. Giacomin, Physics of Fluids (2022). The article can be accessed at https://doi.org/10.1063/5.0094771 .