Coronavirus variants: how dangerous can they become?

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Right now, the Brazilian P.1 variant of the SARS-CoV-2 coronavirus is undermining the country’s entire health system and causing widespread fear across the world. Will the vaccines be effective enough against these new variants? According to some experts, the Brazilian variant is more virulent than the original strain, but no more than the B.1.1.7 variant from the UK, which alone is causing a surge in infections and deaths around the world. When is it going to end? Could even more dangerous variants appear?

While all hopes of getting out of this pandemic rest mainly on vaccines, whose effectiveness has been proven on the original strains, new variants have started to emerge here and there, at an almost worrying rate. But is this concern justified? How long will this “game of new variants” last?

The US government has developed a classification system that now defines three classes of SARS-CoV-2 variants: variants of interest, variants of concern, and high-incidence variants. The variants that are currently making the headlines, namely the Brazilian (P1), the British (B.1.1.7) and the South African (B.1.351), have all been classified as ‘variants of concern’ ( VOC, for Variants of Concern).

Step 1: Understand why the new variants are more infectious

The evolution of a virus depends on different factors, each of which has an influence on its ability to thrive, to spread. Like any biological entity with a reproductive capacity, these factors are: transmissibility, escape of immunity (natural or vaccine) and lethality. Of these properties, transmissibility is the most important for the virus. Fortunately, SARS-CoV-2 is much less deadly than many other viruses, but it has infected and killed many more people simply because it spreads much better.

To this day, researchers are still not sure exactly why the B.1.1.7 variant is at least 50% more transmissible than the other variants, says Joe Grove of University College London, whose recent study suggests that the Spike proteins (advanced) on its surface are somewhat more stable and efficient than those of other variants at penetrating human cells.

Step 2: observe nature and predict evolution

The bad news is that Grove has found that the Spike protein from a coronavirus isolated from pangolins is about 100 times more efficient at entering human cells, suggesting that SARS-CoV-2 may still evolve. and become even more transmissible. ” Until recently, SARS-CoV-2 did not live in humans », He explains. ” Now it is being optimized for humans and there is no reason to think it will end there “.

Coronavirus identified in pangolins is about 100 times more efficient at entering our cells than the one that causes COVID-19 “. But Grove points out that we can’t be sure that changes to the Spike protein alone are responsible for greater transmissibility, not least because he didn’t use live viruses in his experiments. , because he wanted to avoid any risk of escape.

The next factor is immune evasion … Our immune system protects us in two main ways. It produces T lymphocytes which detect and destroy infected cells before the virus can replicate, and antibodies, which bind to the virus to prevent it from infecting cells.

Structure of SARS-CoV-2 and its spike protein “Spike”.

The most effective antibodies, called neutralizing antibodies, bind to the part of the Spike protein that helps the virus get into cells. This means that mutations in this region can allow the virus to escape antibodies to some extent, which has happened with the B.1.351 variant first spotted in South Africa and with the P.1 variant. , observed for the first time in Brazil.

Step 3: define the boundaries and draw a conclusion

But there are limits to the future evolution of the virus … ” The Spike protein is a machine with moving parts that have important roles Grove explains. If mutations occur and break the machine, the virus can no longer infect cells. It would also be much more difficult for the virus to escape the T cell response, as its escape mechanism remains effective as long as the T cells recognize at least part of the virus.

For this reason, resistance to T cells should progress much slower than resistance to antibodies, giving us time to modify vaccines if necessary. ” It seems difficult for the virus to escape T cells completely Says Andreas Bergthaler, from the Molecular Medicine Research Center in Austria.

Next comes lethality. There is growing evidence showing that the B.1.1.7 variant is slightly more lethal than the older variants. “ There is a reasonable possibility that it could even get worse Says Aris Katzourakis of the University of Oxford.

Although it is often said that viruses evolve to be less deadly, there is no reason to think that will be the case with SARS-CoV-2, Katzourakis says. ” The virus can easily be transmitted before killing its hosts. So there is not much selective pressure for this virus to become less virulent. », He explains.

The good news is that the vaccines are working even better than expected, and the coronavirus is unlikely to be able to escape vaccine protection completely in the near future. As more people gain immunity, many experts still believe the virus could become, like other existing human coronaviruses, a simple cold virus.

But since most people have not yet been vaccinated, we are still a long way off, and vaccines may need to be changed more than once to remain effective. As a result, “this evolutionary back-and-forth game with the virus will last for some time,” concludes Grove.

To overcome this virus, it therefore seems obvious that it will be necessary to arm yourself with patience, and above all with discipline and perseverance. Compliance with current health measures and vaccination will be crucial to resume an (almost) normal life as quickly as possible. A secondary vaccination within one or two years is highly likely, in order to cover any new problematic variants. If all goes well, it is possible to hope for a return to normalcy by 2022-2023.

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