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The Omicron variant of COVID-19 keep changing. One study conducted by a group of US researchers and published on November 22 in the journal Cell Host & Microbe has analysedthrough experiments in vitro and computational simulations, the ability of some subvariants currently in circulation to escape the immune response in people who have been vaccinated or who have recently contracted Covid-19. From this research they would be three sub-lineages emerged which appear more effective than others in evading neutralization by the antibodies present in the serum of the individuals who were included in the study. Let’s see how the study was conducted and what it tells us again.
Identikit of the three subvariants
BQ.1 and BQ.1.1 (the second also called “Cerberus”) are very similar to each other (with only one amino acid that differentiates them) and derive from the subvariant Omicron BA.4/5. Instead, BA.2.75.2 comes from the sub-lineage BA.2.75also called “Centaurus” and which we had already talked about. All three, BQ.1, BQ.1.1 and BA.2.75.2, are included in the WHO list of the Omicron subvariants currently under monitoring.
I study
The group of researchers used a type of experiment developed in previous publications, which allows it to to analyze in vitroor through studies carried out on cell culturesthe certain capabilities variants to evade neutralization by the immune response. In particular, the authors used pseudovirusesa sort of “models” consisting of a viral nucleus unable to actually cause the infection and studded on its surface by the different versions of the SARS-CoV2 spike proteincontaining the mutations identified in their respective subvariants. In this case, the pseudoviruses have been put in contact with serum samples arising from people who had recently received the booster dose of one of the mRNA vaccines (Pfizer/BioNTech or Moderna) or they had recently contracted the infection. Of the Omicron subvariants currently in circulation and tested in the study, the three aforementioned are those that have shown the greatest ability to evade neutralization by the antibodies present in the serum samples tested.
Both thanks to the experiments carried out in vitro and thanks to computational models, the research group would have identified the N460K and F486S mutations as crucial to the increased capacity, respectively, of BQ.1 and BQ.1.1, and of BA.2.75.2. to evade the immune response.
The possible limitations
The researchers themselves point out that a possible limitation the fact that he used some pseudoviruses in their experiments, rather than the “real” viruses. However, the authors write, previous studies carried out by the same or other research groups have demonstrated theeffectiveness of this type of approach in determining the ability of SARS-CoV2 and its variants to evade or not the neutralization by the antibodies with which it comes into contact. Furthermore, it is not known whether the subvariants under consideration also use other “access routes” in the process of infection of our cells, in addition to those already identified for Omicron and for the sub-lineages studied so far. This, the authors write, It will be possibly confirmed in future studies.
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