There are at least 26 species of animals, which can come in contact with man, that have the potential characteristics to be infected with SARS-CoV-2. The University College London team has reduced the list of 215 possible species to two dozen, where it will now be possible to confirm whether they are actually infected and whether they have the capacity to transmit the virus. The results were published, this Monday, in the scientific journal Scientific Reports, of the Nature group.
The story begins with a key and a lock. Since the key is protein S (spike), which gives the virus its crowned air, and the lock is the ACE2 protein, which is on the surface of the cells that the virus will infect. Added to this is the bolt, the TMPRSS2 protein, which breaks the spike in two and allows the virus to enter cells.
Perhaps from experience you know that the keys do not always fit perfectly into the locks and that they can either open the door easily, or have some difficulty or not open the door at all. This is what the British team analyzed. But with a slight difference: imagine that it was a magnetic key and lock, whose potential to work together would be greater the longer they were able to stay connected (that is, they depended on the strength of the magnet). Like this, ACE2 proteins with greater affinity for protein S would, at the outset, be more likely to be infected.
Not that the researchers equipped themselves with SARS-CoV-2 and cells from the 215 animals, but knowing the structure of the virus S protein and the ACE2 and TMPRSS2 proteins of each species, they managed to assemble them as a puzzle on the computer and see which connected to each other and whether the connection was stable or not.
“This type of modeling is relatively accurate. More than a few years ago ”, says Celso Cunha, virologist at the Institute of Hygiene and Tropical Medicine, to the Observer.
It was already known that the ACE2 protein remained more or less conserved throughout evolution. That is, several animals have this protein on the surface of cells and it is quite similar between different species. In the case of man, it has the greatest similarities with great primates (such as gorillas, chimpanzees or orangutans), but also with sheep. Among the 26 animals that have the most different proteins are, for example, pigs and foxes. In general, there seems to be little affinity with birds, reptiles or fish.
The 26 species of mammals with the highest affinity for SAR-CoV-2 can potentially come into contact with man – Lam et al. (2020) Scientific Reports
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The researchers have shown that there are 26 animals that can be infected, but we must now demonstrate it in the laboratory. “SARS-CoV-2 infections have been reported in the real world in cats, lions and tigers, dogs and mink. And animal infection studies have also identified cats and dogs as hosts, as well as ferrets, monkeys and marmosets, ”wrote the article’s authors.
“This virus is able to bind to the recipient [diz o estudo]. And that means just that: it is able to enter the cell. It does not mean that within the cells it was possible to replicate with the same efficiency ”, explains Celso Cunha, who did not participate in the study.
Having confirmation that the key works in the lock does not tell us, as Celso Cunha says, what the virus is capable of doing inside the cell. Is that although the ACE2 protein is similar between several species, the cell components that allow the virus to replicate – like a 3D industrial photocopier – can differ greatly from those in human cells. Therefore, they may not be able to copy the virus and there is little chance that the virus will cause a disease.
Then it also depends on the cells that have the right lock for SARS-CoV-2 – the ACE2 protein. In humans, this type of receptor exists in several organs, which explains the associated complications in the heart or at the neurological level, for example. But in other animals it may not be so.
Finally, a virus can enter the cell, use the industrial photocopier, but then have no way to get out and infect other organisms – that is, to transmit itself, spreading the disease. In man, it is said, SARS-CoV-2 “adapted well and quickly and multiplies effectively”, explains Celso Cunha.
“In summary, our work does not aim to provide an absolute measure of the risk of infection. Instead, it should be considered as an efficient method to track a large number of animals and suggest a possible susceptibility and, thus, guide new studies ”, write the study authors.
Thus, there are still many “ifs” about the danger that these animals can pose to humans, but one thing is certain: if the virus managed to travel from the bat to the man, become highly effective using the human photocopier and found a way leaving the host to infect another, can do it again.
Tools like the one used by the British team do not allow to end viruses that originate in animals, nor to assess the risk of infection, but they are a quick and much less expensive way to select the best candidates.
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