Scientists have found that Sars-CoV-2 is 1000 times more effective at infecting human cells than the coronavirus found in bats.
Researchers at the Francis Crick Institute in England analyzed the structure of the Sars-CoV-2 spike protein, as well as a similar structure present in another virus in the coronavirus family that infects bats. The findings were shared on Thursday (9) in the journal Nature Structural & Molecular Biology.
Spike proteins are one of the main components of Sars-CoV-2, covering the outer layer of the microorganism and serving as a tool to enter human cells. For this reason, the analysis of these structures is essential if we want to understand the evolution of the new coronavirus and develop a vaccine.
The researchers analyzed the protein using a technique called cryogenic electron microscopy (cryo-EM), capable of delivering very detailed results. They then compared the structure to the spike protein of a bat coronavirus, RaTG13, which is similar to that of Sars-CoV-2.
According to the researchers, although both proteins were more than 97% identical, some significant differences were observed. The main one may be a change in the part of the spike protein in Sars-CoV-2 that connects to a viral receptor in human cells, known as ACE2. Another important variation was observed on the surface that holds the spike proteins together.
“Changes in the virus’ genome, which affect the spike’s structure, therefore have potential to make the virus either more or less able to enter the host’s cell,” explained Antoni Wrobel, co-author of the study and researcher at the Francis Crick Institute, in a statement. “At some point in the evolution of this virus, it seems to have picked up changes, like the differences we found, which made it able to infect humans.”
These differences indicate that the spike proteins of the new coronavirus are more stable and capable of binding about 1,000 times more efficiently to human cells than RaTG13. Based on their findings, the researchers suggest that a microorganism like the one that infects bats is unlikely to be able to infect humans, corroborating the theory that Sars-CoV-2 is the result of a “combination” of multiple coronaviruses.
“The exact process of how SARS-CoV-2 evolved remains unclear and is something many researchers are trying to piece together,” said study co-author Donald Benton. “Our work provides a piece of this puzzle, as it suggests that the virus did not come straight from the bat coronaviruses currently known.”