A coronavirus discovered in a Brazilian bat has a feature that closely resembles one found in SARS-CoV-2.
The virus was identified in a bat of the species Pteronotus parnellii sampled in Brazil. Researchers were able to reconstruct its complete genome, in other words, all of its genetic instructions. They then compared it with already known coronaviruses to determine its place within their broad family.
A Pteronotus parnellii bat photographed in Mexico.
Credit: Lily_Trujillo, CC BY-SA 4.0, via Wikimedia Commons.
The result indicates a relationship with the catalogued groups. This virus belongs to the betacoronaviruses, like SARS-CoV-2, which causes COVID-19, and the MERS virus. However, it is different enough from the five recognized subgroups for the authors to propose placing it in a new subgenus.
One detail of its Spike protein particularly attracted attention. This protein forms the spikes on the surface of the coronavirus and is involved when it enters a cell. Before functioning fully, some Spike proteins can be cut at a precise location by an enzyme found in the host, called furin.
The Brazilian virus does indeed possess a site where furin can carry out this cleavage. At that location, its sequence is written RDAR. That of SARS-CoV-2 is RRAR: only one of the four units making up this short motif differs. The researchers' experiments confirm that the site of the new virus can indeed be cleaved by furin.
This resemblance does not mean that the two viruses have the same capabilities. The ability to infect a person depends on many other factors, including the virus's ability to recognize human cells and multiply within them. The study reports no human infection caused by this bat coronavirus.
To understand the origin of this feature, the scientists compared the structure of several Spike proteins. Other bat betacoronaviruses also possess cleavage sites located in the same place. This region therefore appears able to accommodate such sequences during evolution without preventing the protein from functioning.
This discovery also provides rare data on South American coronaviruses. Their genetic diversity remains less well documented than that of viruses studied in Asia, Africa, or Europe. Sampling more species and regions makes it possible to better understand the forms already present in nature.
Researchers must now determine the biological properties of this new lineage, beyond its genome and cleavage site. This work may clarify which cells it can infect and whether the observed characteristics actually play a role in its possible transmission to other species.