Why Omicron could be the latest ‘worrying’ variant

The question of whether the virus are alive remains controversial but, like all living things, however, they evolve. This fact became very clear during the pandemic, With l’emergence regular of new variants of concern coming to shake up the news.

Some of these variants were found to be more efficient than others at spreading from person to person, and eventually became dominant by supplanting slower versions of SARS-CoV-2, the virus responsible for the disease. Covid-19.

This improved propagation capacity has been attributed to mutations in the spike protein – projections in the form of mushroom on the surface of the virus – which allow it to bind more strongly to ACE2 receptors. ACE2s are receptors located on the surface of our cells, such as those lining our airways, to which the virus attaches to enter and begin to replicate.

These mutations allowed the Alpha then Delta variants to become dominant at the global level. And the scientists expect the same to happen with Omicron.

A virus however, cannot improve indefinitely.

Omicron, “best” possible version of SARS-CoV-2?

The laws of biochemistry cause SARS-CoV-2 to eventually develop a protein Spike binder to ACE2 as strongly as possible. From there the speed the virus’s spread will no longer be limited by its ability to attach to our cells; other factors will limit its diffusion, such as the replication speed of its genome, how much it can enter the cell and how much new virus an infected human can produce and disseminate.

In principle, all these factors should eventually evolve towards maximum performance.

Has Omicron achieved this apogee ? There is currently no reason to believe so … So-called “gain-of-function” studies, which examine the changes SARS-CoV-2 needs to spread more efficiently, have identified many mutations that would improve the ability of the Spike protein to bind to our cells that Omicron does not have. In addition, improvements could still be made in other aspects of the virus life cycle, such as genome replication, as I mentioned above.

But suppose for a moment that Omicron is indeed the “ultimate” variant, the one with maximum propagation capacity …

Indeed, perhaps the laws of probability genetic do they mean that SARS-CoV-2 can hardly do better? In the same way that zebras have not developedeyes on the back of their head to avoid predators, it is plausible that the Covid virus cannot reach its theoretical maximum because it would have to obtain all the necessary potential mutations at the same time – which would be too improbable.

But even in a scenario where Omicron would be the best variant in terms of spread between humans, new variants will continue to appear in an attempt to bypass our immune defenses.

After a viral infection, the immune system adapts by producing antibodies, which attach themselves to the intruder to neutralize it, and killer T cells, which destroy infected cells. The antibody are small molecules proteins that specifically recognize certain portions of the virus, and killer T cells also recognize infected cells by their altered form. SARS-CoV-2 may attempt to evade the immune system by changing enough so that its “appearance” is no longer recognized by our defense cells.

This is why Omicron is apparently so successful at infecting people who are already immune, by vaccination or a previous infection: mutations that allow its Spike protein to better bind to our ACE2 also reduce the capacity of antibodies recognize the virus and neutralize it.

On the other hand, the Pfizer data suggests that T cells should respond similarly to Omicron and previous variants. This matches the observation that the new variant has a lower death rate in South Africa, where most people are immune.

This is an important point: a past exposure therefore still seems to protect against the most serious forms of disease and death. We are therefore in a “compromise” situation, where the virus can replicate itself and reinfect former patients, but where we are not as seriously ill as the first time.

Possible future

This is where the most likely future of this virus lies – and us. Even if he behaves like a professional player and ends up maximizing all of his stats, there is no reason to believe that he will not be controlled and knocked out by the immune system. Mutations that improve its ability to propagate do not significantly increase the number of deaths.

This virus to the best of its ability might then just continue to mutate in a random fashion, changing enough over time to become unrecognizable to the immune system’s adapted defenses and allowing re-infections.

We could have a season of Covid each winter, in the same way that we already have a season of flu at the same time. The flu virus may also exhibit a similar pattern of mutation over time, known as “Antigenic drift”, resulting in re-infections. The new annual viruses of influenza are not necessarily better (more efficient) than the previous year, but simply different enough.

Perhaps the best argument for this possibility for SARS-CoV-2 is thatthere is already a neighboring coronavirus, HCoV-229E, which has evolved in this direction and is one of the responsible for our colds.

Omicron will therefore not be the final variant … but it could be the last variant known as “worrying” according to WHO terminology. If we are lucky, and we must remember that the evolution of this pandemic is difficult to predict, SARS-CoV-2 could become a endemic virus which slowly mutates over the years.

The resulting disease could become mild, as previous exposure (s) may create a immunity capable of reducing the likelihood of hospitalization and death. Most people would then be infected for the first time as children, which could happen before or after a vaccine, and subsequent re-infections would hardly be noticed …

A group of scientists will nevertheless continue to monitor the genetic modifications of SARS-CoV-2 – as long as the new variants remain of no concern. Until a next virus in turn crosses the cash.