A color advances on the Risiko table. It is the English variant that conquers territories. But what is the secret weapon of the most contagious coronavirus strain? Since its emergence on September 20 in Kent, one of the mutations on the spike – the tip of the crown – has been looked at in position 501. “With the new conformation, the arm that attaches to our cells is more stable. It is easier for the virus to infect us “,” he explains Massimo Ciccozzi, professor of medical statistics and epidemiology of the Campus Bio-Medico of Rome. But the same 501 mutation is present in the South African, Brazilian and Nigerian variants. Yet no one has turboed like the English one, codenamed B.1.1.7. Nor, by going to look at the virus in the laboratory, the secret weapon thanks to which the British strain manages to infect us best has emerged clearly.
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In the scientific journal CellIn recent days, virologists from the Chinese Centers for Disease Control published a study in which they remark, surprisingly, that the mutation in position 501 does not make the coronavirus more contagious, in contact with human cells grown in vitro. “It’s a solid study, but it disagrees with everything we knew so far,” he comments Francesco Broccolo, professor of Microbiology at the University of Milano Bicocca. That the English variant is more contagious, in fact, is more than evident from the epidemiological data: where it arrives, it tends inexorably to replace the original strains. Its prevalence increases from week to week, inexorably.
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But the fact that no lab has so far been able to unravel the secret of the British variant’s success is an indicator of our limits in nailing the killer coronavirus to its responsibilities. “The Chinese study, for example, used pseudoviruses, that is viral surrogates created in the laboratory with the mutated spike protein. However, it is possible to insert only three mutations at a time. So it becomes difficult to understand what is the synergy of all the mutations that are. present in the variants, “explains Broccolo.
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A first qualitative leap, previously, the coronavirus had made with the mutation in position 614. “It was the first that we have observed and it has already increased infectivity compared to the Wuhan coronavirus“, explains Broccolo. Emerged in Beijing, from there it arrived in Europe, taken over in Italy in February by Ciccozzi, the 614 was probably the gasoline that set off the wave of last March in Northern Italy. From our country, the spark then traveled to the rest of the world, helping to set off the wave of autumn spread across the globe. In those months, however, variant monitoring was not yet widespread. The first laboratory studies of the 614 came in September, 8 months after its discovery. They confirmed that the mutation makes the coronavirus capable of infecting our cells 13 times faster than the Wuhan virus. Despite this, the English variant is replacing it in a few months, with an assertiveness that does not seem to admit replicas.
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And that it may not be confined to the world of men. The Chinese study on Cell in fact it opens up a new scenario to our gaze. “Colleagues have seen that the 501 mutation does not make the virus more infectious in contact with human cells. But it increases its contagiousness by 4 times in contact with mouse cells – explains Broccolo – and not only. Also in the model. animal, Sars-Cov2 evolves rapidly and within a few replicates acquires new mutations that make it more lethal “. The story of the pandemic, therefore, may not end with human herd immunity. “The mouse could become a reservoir of the virus, causing it to mutate and then see it return to us, in a series of spillovers destined to regenerate continuously”. It is a worst case scenario, the result of only speculation. But it shows us that the coronavirus pathways are numerous. And his strategies are still far from clear to our eyes.
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