Vaccination against mutations: how to stop the emergence of new types of coronavirus

But there are other dangers if humans do not interrupt the evolution of the virus.

Yelena Ivanova

"Much more is known about the coronavirus today than scientists knew a year ago. The virus is under the influence of natural selection. It acquires mutations that make it more adaptable to life and reproduction. During this time, the original Wuhan version practically disappeared, it was replaced first by "alpha" and then by "delta"", - says Georgy Bazykin, Doctor of Biological Sciences, Professor of Skoltech, Head of the Molecular Evolution Sector of the Institute for Information Transmission Problems of the Russian Academy of Sciences, Georgy Bazykin, in an interview with the YouTube channel Chas science" .

The molecular clock concept says that the accumulation of mutations occurs at a more or less constant rate. In the coronavirus, mutations occur continuously, at least once every 2-3 weeks in one evolving lineage. But what exactly changes are taking place is not known for certain.

Maybe there are only 5 such mutations in his genome, he acquires all 5 and after that he finds himself on the top of the mountain of his fitness, and further from the top of the mountain he cannot go anywhere. Or it may turn out that he has an infinite number of mutations at his disposal. During all further evolution, he will accumulate more and more of them. And it seems that things are heading towards the second scenario than the first.

The measles virus, for example, practically does not evolve adaptively, so people who can get sick from it get about the same variant as 30 years ago. That is why measles can be vaccinated once - and for life.

With the flu, things are much more complicated. The influenza virus is constantly changing rapidly and acquires mutations that enable it to quickly adapt to the conditions of human immunity. Georgy Bazykin suggests that the coronavirus is more similar to the influenza virus in terms of adaptability. But its rate is higher than that of the flu, and the rate of accumulation of mutations is lower. Now there is a clear understanding of which variant of the coronavirus won.

- Delta destroyed all the diversity accumulated by the virus during the epidemic. Therefore, we can expect that the entire evolution of this virus in the human population will be among the descendants of the delta, says Bazykin.

The Russian situation is not much different from the world one. Russian scientists, unlike their Western counterparts, do not have a lot of data on the virus sequences. If in the United States and Great Britain, researchers have counted more than a million sequences, in Russia this figure did not exceed ten thousand. This means that Western scientists can discover new variants much earlier than in our country. In other words, our researchers will only notice a new species when it cannot be overlooked.

The emergence of radically new options occurs in a very short time. One possibility is the evolution of a virus in a person with a suppressed immune system. For example, we are talking about a cancer patient in which the coronavirus lives for several months. Such a case was observed by Georgy Bazykin and his colleagues from the Institute of Influenza and the Pavlov Hospital in St. Petersburg.

This was patient C. During the year of her illness, a large number of new mutations were acquired. When a virus evolves within one person, combinations may arise that pose an epidemiological danger.

In this case, we are not talking about "long covid", when the patient is struggling with the consequences of the body's reaction to covid, and the virus itself is no longer in the body. The point is that with suppressed immunity, viruses - influenza, human immunodeficiency or covid - can live in one person for many months. And then it becomes possible to accumulate a large number of mutations and the emergence of a "mutant" with new properties.

New variants arise when one person becomes infected with two different variants. As Professor Bazykin says, options can "get married" and make "kids." These "kids" will carry chunks of genetic information from both "parents". This process is called "reassortment" for influenza and "recombination" for coronavirus.

- This is the mechanism that, as we know from influenza, can lead to the emergence of a variant with radically new properties. All major influenza pandemics of the 20th and 21st century have been caused by reassortant mixed variants. This is understandable - this is something radically new from the point of view of our immune system.

The professor refers to the research that was carried out in Laos. Scientists have isolated viruses from bats that were very close to the human coronavirus, which was not previously known. This variety of variants shows that the human coronavirus, even before it jumped from animals to humans, is a descendant of several recombination events, and its genome is mosaic.

- We still do not know which animals jumped into humans, but now we see closer relatives of our human coronavirus. It turned out that our human coronavirus is the descendant of many recombination events. This poses some threat because there are two problems here. - says the scientist.

The first problem, according to Georgy Bazykin, is that the coronavirus will continue to recombine the different variants that are now in the human population. But the danger here is not very big, because human coronaviruses are similar to each other.

Another hypothesis is much more dangerous. The exchange of coronaviruses between humans and other animal species is fairly easy. Not yet, but this exchange could create fertile ground for recombination between the human coronavirus and some other variants that are now circulating among animals. This raises concerns if we focus on the influenza virus, says Georgy Bazykin.

There is only one way to counter this - to stop the evolution of the coronavirus, to make it as small as possible. To do this, you need to cut the transmission routes of the coronavirus, prevent it from changing and acquire mutations that are useful for it and harmful to us.

"Vaccination reduces the likelihood that you yourself will become infected. It is smaller, but it makes it less likely that you will infect someone else if you become infected. Thus, you cut these chains. It's the same with wearing masks, it's the same with whatever non-pharmaceutical restraints we have at our disposal. This improves the epidemiological situation, but it also improves the evolutionary situation of the virus", - concludes Georgy Bazykin.