Researchers from Germany and the U.K. developed 'lite' versions of SARS-CoV-2 to safely study its infectious behavior in a lab. They discovered that the virus's spikes serve like a switchblade, allowing it to conceal from the human immune system more easily.
The particles, termed "synthetic minimal virions," are made up of modules built from the ground up to provide insights into important aspects of the virus but lack the ability to work together as an infectious unit.
The namesake corona (crown) of spikes projecting from the virus's coat was the first mechanism the team looked at.
Since the pandemic erupted in early 2020, virologists have been trying to figure out how these projections aid the disease in its quest to survive and multiply.
It's becoming obvious that the proteins are both a boon and a bane for the small intruder.
To its advantage, the spikes work as a key for a type of cellular lock known as an ACE2 receptor, deceiving tissues into allowing the virus passage.
However, the proteins are an easily recognized trait for antibodies to grab onto and cause a clean-out. We even base vaccines on its predominance, giving naive, uninfected immune systems a sense of its shape in order to better prepare them for a real infection.
It turns out that the cunning coronavirus has picked up a few tricks over the years that help it get past this issue.
The scientists were interested in how certain fatty acid-type immune components interact with the spikes to cause inflammation.
Previous studies had identified a part of the spike where immune molecules clung. Given how resistant this region was to change, it's reasonable to infer it's a critical structure for the virus's survival.
We now understand why. When the immune molecule grabbed on, the spike underwent a structural change, effectively folding itself away, according to the researchers.
This makes breaking into any surrounding cells much more difficult. However, in this shape, the virus has a more difficult time attracting antibodies.
"By 'ducking down' ... the spike protein upon binding of inflammatory fatty acids, the virus becomes less visible to the immune system," Oskar Staufer, formerly from the Max Planck Institute for Medical Research and currently working at the University of Oxford, said.
"This could be a mechanism to avoid detection by the host and a strong immune response for a longer period of time and increase total infection efficiency."
It's a glimpse into a destructive virus that continues to surprise us, as well as a glimpse into how synthetic models like this could help us reduce the pathogen's long-term impact on populations around the world.
This research was published in Nature Communications.
