Coronavirus: will there be more dangerous mutations?

How high incidences and increasing immunity to SARS-CoV-2 can cause us to struggle with more virus variants. And why vaccinations are still useful

Whether the British, the South African or the Brazilian variant - reports of new variants of Sars-CoV-2 have been increasing for months. The fear is that the coronavirus could mutate in such a way that neither the vaccines nor a survived infection protect against renewed infection and disease. Or the virus could become even more contagious or deadly.

It is normal for viruses to mutate. In order to reproduce, viruses smuggle their genetic information into a host cell. During the replication of the virus genetic material, which is necessary for the virus to multiply, small copying errors occur and so the genetic code of the virus changes. This doesn't always make the virus more dangerous. Viruses that are less contagious are often created. But these do not prevail. Only those variants that have an advantage over the others can spread well. For example because they are more contagious. Certain circumstances can encourage dangerous variants to arise.

Exchanging mutations in the event of double infections are rare

The following scenario is rather unlikely: In the case of infections, the coronavirus encounters another variant of SARS-CoV-2 in a host, exchanges genes with it and suddenly acquires many new mutations. "That is rather rare," says the virologist Friedemann Weber from the University of Giessen. “In terms of timing, the two infections would then have to occur almost simultaneously. Because if one variant attacks the host earlier, a certain immunity arises that can offer protection from the second variant. "

Higher incidences lead to more variants

Another driver of mutations worries researchers much more. The saying “it's the masses” also applies to mutations. The sheer accumulation of virus generations that have arisen has contributed mathematically and statistically to a wide range of variants in more than 140 million confirmed infections worldwide. "Higher incidences mean that more of the virus is present in the environment ", says the physician Luka Cicin-Sain from the Helmholtz Center for Infection Research in Braunschweig. Even with a low mutation rate, more mutations can simply occur due to the mass of viruses." A high incidence makes it easier for that the virus evolves and then advantageous mutations are selected. "

More contagious variants are gaining ground

Beneficial mutations include those that make the virus more contagious. The British variant B.1.1.7 now dominates in Germany. the infection process. The reason for this is probably that they have changes in the genetic material for a surface protein, the so-called spike protein. With this protein, the virus docks onto the surface of body cells. This change seems to make it easier for the virus to attach to cells and infect them.

"Such mutations give the virus the opportunity to spread better," says Cicin-Sain. It is difficult to say whether further more contagious virus variants will appear in Germany in the future. In the past, the virus has already managed to become more infectious twice. "Hopefully there aren't any more ways for the virus to infect us better," says Cicin-Sain.

Escape mutations: The virus escapes the immune system

Mutations can not only make the virus more contagious, but in very rare cases also enable it to escape the immune system, even if the immune system has already become acquainted with an earlier variant of the virus or a vaccine. Researchers then speak of escape mutations. They are favored by increased pressure on the virus in the course of increasing immunity in the population. Viruses that can also infect people who have already contracted another variant of the virus or who have been vaccinated against it can multiply better than others because they have more hosts available. "Vaccinations, but also natural immunization in the course of an infection, increase the selection pressure for the virus," says Luka Cicin-Sain. This can encourage the spread of escape variants. They are genetically modified in such a way that they are no longer recognized by the defense substances (antibodies) of the immune system against the previous variants. For the virus, it is irrelevant whether antibodies were produced by a vaccination or by an infection. “In both cases, mutations then have advantages that the antibodies cannot recognize,” says Cicin-Sain.

Researchers from the Leibniz Institute for Primate Research in Göttingen reported on specific escape options. In their study, neutralizing antibodies used in the treatment of COVID-19 were ineffective in both the South African variant B.1.351 and the Brazilian variant P.1.

According to Friedemann Weber, the Brazilian and South African variants could spread more widely as a result of the vaccinations in Germany. Because they are no longer recognized by the antibodies as well as the original variant and the British variant and could thus prevail over them. "That can happen, but I do not expect a sharp increase," said Weber. Because the immune response is not just about antibodies, but also about T cells. These belong to the white blood cells and, for example, track down cells infected by the virus in order to destroy them. They can also reduce the viral load and, above all, seem to protect against a severe course, says the virologist. "Despite the virus variants, you are not defenseless with a vaccination."

Updates to the immune system

But what about completely new dangerous variants in the future? "New variants will certainly appear as long as the virus is spread around the world," says Friedemann Weber. The variants are perhaps a bit more contagious and the immune protection probably has to be updated again and again. A booster vaccination that takes new variants into account could therefore be necessary. "According to all that we know so far, a complete loss of an existing immunity is not to be expected."

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