Three subtypes were found in coronavirus. They increased its infectivity – Science

TASS, May 20. Molecular biologists analyzed the genomes of several thousand strains of SARS-CoV-2 and came to the conclusion that the virus was divided into three separate lines, each of which has its own set of mutations in key genes. Preliminary research results published in the electronic scientific library bioRxiv.

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“Our observations show that now three different SARS-CoV-2 lines circulate in the world in parallel, which are significantly different from each other in terms of epidemiology. For example, line C, which is characterized by a high growth rate, appeared in Europe at the end February. Characteristic for it mutations are located in those parts of the genome of the virus that are directly responsible for its reproduction and penetration into cells, “the scientists write.

From the first days of the outbreak of coronavirus infection, scientists are trying to understand which way and how its pathogen, the SARS-CoV-2 coronavirus, is evolving. Today it is known that mutations in it accumulate at about the same rate as the flu virus, however, scientists cannot yet understand what these mutations can lead to.

In particular, in early March, Chinese biologists said that the virus could split into two subtypes, S and L. They differ in the severity of symptoms and the speed of spread. Other scientists doubted this, noting that changes in the general gene pool of the virus could occur due to various random processes, and not because of real differences in the infectiousness of these subtypes of SARS-CoV-2.

A group of molecular biologists led by Michael Charleston, an associate professor at the University of Tasmania at Hobart, analyzed and compared several thousand new-type coronavirus genomes that have been transcribed over the past four months. According to the results of the work, scientists proposed to divide the coronavirus into three separate lines.

Global virus evolution

For this study, scientists developed a special technique with which they evaluated the epidemiological and evolutionary significance of each mutation in the SARS-CoV-2 genes. Thanks to this, scientists found out how the accumulation of such changes affected the contagiousness of the virus and the speed of its spread throughout the Earth.

As it turned out, the virus can be divided into three separate lines that differ both in infectivity and other biological properties, and in how they spread to different corners of the Earth. The first two of them, which the scientists called “line A” and “line B”, are similar in their properties to the subtypes S and L that Chinese scientists had previously proposed.

Researchers note that they differ only slightly from each other. These varieties appeared in the early days of the epidemic, back in November or December 2019. Initially, “line A” and “line B” spread throughout China, but subsequently they ended up in other Asian countries and on the west coast of the United States.

The third subtype of coronavirus, “line C”, appeared much later, in late February. It originated in Europe and differs from the other two in the set of significant mutations in the S gene, which is responsible for the penetration of SARS-CoV-2 into human cells, and in the ORF1ab gene, which is critical for the reproduction of the virus.

The researchers noted that these changes not only increased the infectivity of the virus, but also made it more variable, accelerating the process of accumulation of mutations in its genome. The advent of Line C, as Charleston and colleagues suggest, explains why the virus began to spread rapidly across Europe in early March. Now this line is the most common type of virus in the world.

At the same time, researchers do not exclude that the “C line” could spread so quickly across Europe due to random factors, for example, because it was the first to penetrate its territory and was able to gain a foothold there. According to the researchers, subsequent observations of their distribution, especially in countries of the Middle East, for which there is almost no data, will show which of these two hypotheses is closer to the truth.

It should be added that the article was not reviewed by independent experts and editors of scientific journals, as is usually the case in such cases. Therefore, conclusions from it and similar articles should be treated with caution.

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