The appearance of new variants they have been a cause for concern since the start of the pandemic. To date, there are five qualified by the World Health Organization (WHO) as ‘worrying’. Ómicron, detected for the first time in South Africa, is the last: before it they were Alpha, Beta, Gamma and Delta.
The main characteristic of this variant is that it has more than fifty mutations, of which at least 30 are found in protein S, known as the entrance key to the human organism. “Ómicron has something that had never been seen“, explained to AS Nuria Campillo, scientist of the CSIC. This variant, in addition to being highly contagious, has the particularity of partially escape the vaccine.
Something that worries experts, although a recent finding may represent an important advance against it. An international team of scientists has achieved identify antibodies that neutralize both Ómicron and other variants of the coronavirus. What these antibodies do is target specific areas of protein S, which remain unchanged while viruses mutate.
May lead to new vaccines
“This finding tells us that by targeting antibodies that target these highly conserved spike protein sites, there is a way to overcome the continuing evolution of the virus, “explains David Veesler, lead author of the study and investigator at the Howard Hughes Medical Institute. Thanks to the identification of these “Broadly neutralizing” antibodies, new vaccines and treatments could be developed with them, they would be able to combat variants that arise in the future, as well as the current one.
The mutations present in the spicule protein reaches 37, with which it is used to bind to cells and infect them. It is, as various experts have confirmed astonished, an excessive amount compared to others. “Other variants had mutations a few at a time, which is normal in the evolution of a virus, not this “, commented the CSIC expert in this regard.
It is believed that thanks to this large number of mutations would explain the very high capacity to infect, even in people vaccinated or who had previously overcome the infection. “How has this affected constellation of mutations in the spike protein of the omicron variant to its ability to bind to cells And of evading the antibody responses of the immune system? “Veesler’s team wondered.
Simulation of mutations
To analyze how these mutations affected, experts created a non-replicating virus (pseudovirus), in order for it to produce S proteins on its surface, just as SARS-CoV-2 does. After that, they created this pseudovirus with S proteins with Omicron’s own mutations, but also of other previous variants of the pandemic, indicates the study published in Nature.
First they observed the capacity of all versions of spike protein to bind to the protein on the surface of human body cells, which the virus uses to enter it: the receptor of the angiotensin converting enzyme-2 (ACE2). And in these tests they discovered that Ómicron is capable of binding to the protein 2.4 times better than the mutation of the virus isolated at the beginning of the pandemic. “This is not a huge increase, but in the SARS outbreak of 2002-2003, mutations in the spike protein that increased affinity were associated with increased transmissibility and infectivity“, reveals the expert.
New antibodies
Of the authorized-for-use antibody treatments initially employed, all but one had no activity against Ómicron, or it was very small. Sotrovimab was the exception, with a neutralizing activity that was reduced between two and three times. Something that led the experts to try a broader range of antibodies, identifying up to four types of antibodies who retained their ability to fight Omicron.
These are targeting four areas of protein S that are in the SARS-CoV-2 variants, but also in other coronaviruses such as sarbecoviruses. Specific areas that perform essential work that the protein would lose if mutated. They are therefore called “conserved”. According to Veesler, this finding suggests that the development of vaccines and other treatments with antibodies directed at these regions can be effective against different variants.
Vaccine against infection
Another avenue of analysis of the study has to do with the effectiveness of antibodies against previous isolates of the virus to protect it from Ómicron. For this, various antibodies were used: patients who had been infected with other versions of the virus, who had been vaccinated against different variants and, a third, from patients who had been infected and then vaccinated.
Those infected by previous variants and had received the vaccine had a reduced ability to block the infection. Who received Janssen, Sputnik V or Sinopharm had little or no capacity to block the entry of omicron into cells. For their part, those who received Moderna, Pfizer or AstraZeneca had antibodies with a certain neutralizing capacity, although reduced between 20 and 40 times, more than compared to any other variant.
For their part, those who had recovered from infection and then vaccinated had reduced activity, although with a smaller reduction, of about five times, which reflects the usefulness of the vaccine after overcoming the disease. And compared to a group of kidney dialysis patients, who had received a third booster dose, the reduction was only four times. “This demonstrates that a third dose is very, very helpful against omicronVeesler explains.
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