If it takes two weeks to understand if the Omicron variant manages to escape the vaccines, as has been said several times since the first report from South Africa arrived, it is because this is the time required by the two tests to obtain the answer. . On this basis, vaccine companies will be able to decide whether or not to update the vaccines.
The two possible tests, which are probably already underway in many laboratories around the world, are based on the analysis of the antibodies present in the sera obtained from vaccinated subjects and on the analysis of the behavior of T lymphocytes, i.e. of the immune cells linked to the so-called induced memory. . “These are two types of experiments which, in different ways, will allow us to understand the tightness of current vaccines”, notes the virologist Francesco Broccolo, of the University of Milan Bicocca.
The first group includes the “seroneutralization tests”, which use sera obtained from vaccinated subjects and allow us to see how the antibodies are or are not able to neutralize the Omicron virus. “For this purpose – he observes – the Omicron variant of the SarsCoV2 virus can be used, but this is a risky path as it requires its isolation on cell cultures with production of Omicron variant viral stocks, or pseudoviruses can be used, ie inert modified viruses, including all 35 mutations of the Omicron variant “. By putting the virus in contact with the antibodies contained in the sera of the vaccinated subjects for different titles, it is possible to observe whether or not the variant manages to escape the neutralizing antibodies induced by the vaccine. The second test bench is a flow cytometry test to verify the efficiency of the memory of T lymphocytes, that is, cell-mediated immunity: “it could be more plastic and protect from the Omicron variant. In this case we go to see if, at contact with the Spike antigen of the new variant, the memory T lymphocytes are still able to recognize it despite the differences present between the Spike protein of the Omicron and that of the vaccine, measuring the specific production of interferon following antigenic stimulation “, explains the virologist. The technique that allows you to check if this happens and to what extent is called Elispot (from the English Enzyme-Linked immunoSPOT): “It is a widely used approach to measure the response of cellular memory,” he observes.
“Both of these types of experiments take about two weeks,” he adds. It would also be interesting to measure the response of T lymphocytes of patients who have had the disease to evaluate cell-mediated protection in subjects who have had the disease. “From an epidemiological point of view, meanwhile, the percentage of infections from Omicron variant with respect to Delta in vaccinated people. Most likely, Broccolo notes, “sequencing should not be necessary for everyone to get the answer: considering that Delta is by far the most widespread, multitarget molecular swabs already allow to identify a suspect Omicron variant case “. The latter has in fact a characteristic that the tests can recognize as it is present only in the Alpha variant, now practically disappeared: it is deletion 69-70.” If the tests identify this deletion, then – he concludes the expert – confirmation could be sought in sequencing. “
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Source From: Ansa
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