Since the appearance of the new coronavirus that causes the COVID-19 disease, a multitude of conspiracy theories have not stopped growing that affirm that this virus is a biological weapon intentionally disseminated from a laboratory (Chinese or American, depending on who states the charge). The ideas are very disparate, from genetic manipulation with the aim of making a “clean” of the aging population in China to the creation of the virus to later profit from the commercialization of a vaccine. Some of the more elaborate theories also introduce dispersal from airplanes (the famous chemtrails ) and directed by 5G.
Although the health authorities have denied this type of idea from the beginning, hoaxes and fake news run faster than ever on social networks. Who has not had a conversation about this in any of their WhatsApp groups?
Now, in a letter published in Nature Medicine and signed by scientists from different universities in the United Kingdom, the United States and Australia, the natural origin of SARS-CoV-2 is demonstrated based on the analysis of its genome and comparing it with the other six coronaviruses that They cause diseases in humans, especially the one most similar to it: SARS-CoV.
Based on the structural and biochemical studies published so far on the coronavirus, the scientists look at two of its most notable characteristics and which presumably would be the cause of its high infectivity. On the one hand, SARS-CoV-2 appears to have a high affinity for a receptor on human cells called ACE2. And secondly, its spike protein (S) – the one that binds to the receptors of the cell it infects – first needs to be cleaved by an enzyme from the host, which in this case is a furin.
Mutations at the coreceptor binding site
The authors explain that the most variable part in the genome of the coronavirus family is precisely that area that must bind to the human cell receptor. For SARS-CoV type viruses, it is known that there are six fundamental amino acids that are going to determine what type of cells they can bind to and therefore infect.
Studies published so far tell us that SARS-CoV-2 possesses a binding site with high affinity for the ACE2 receptor in humans and other animal species. However, as the authors show by doing a computer simulation, the union is far from perfect. In other words, despite the high affinity for the human ACE2 receptor, said affinity could be even higher (and, therefore, the virus would have a much higher infectious capacity).
This fact leads the authors to conclude that the virus cannot be a weapon manufactured in a laboratory, or a virus genetically manipulated to be more aggressive since, if it were, would it not make more sense that its binding capacity was the most appropriate solution optimal? We would speak, therefore, of mutations achieved through natural selection.
Genomics of the cleavage site
As we have already commented, the protein (S) of the virus has a so-called ‘cleavage site’ that must break an enzyme from the host to allow cell attachment and subsequent infection. The molecular characteristics of this cleavage site are unique to the new virus and do not resemble those of other coronaviruses that affect humans . In addition, it has certain characteristics that are typical of viruses that at a certain moment make the jump from other animals to man.
The authors argue that, if it is a virus manipulated in the laboratory, its basic molecular structure should be more similar to that of other human coronaviruses, something simpler than using a virus that affects animals as a starting point.
SARS-CoV-2 Origin Scenarios
The authors conclude that it is highly unlikely that the new coronavirus was artificially created in a laboratory. Regarding its origin, there are two possible scenarios: that natural selection has operated before the passage from other animals to man, or that it has done so afterwards.
Scientists believe that it would be convenient to obtain the sequencing of viruses similar to SARS-CoV-2 that infect other animals , as this will provide a lot of information about the selection process that has led to the current form. “Identifying a possible SARS-CoV-2 intermediate host, as well as sequencing the virus from very early cases, would be equally very informative,” the experts conclude.
