How dangerous is the new mutation of sars-cov-2 virus?An international team of researchers from the Swiss Institute of Virology and immunoprophylaxis (IVI) and the University of Bern in Switzerland, the Centers for Disease Control and prevention in the United States, and the Friedrich rofler Institute in Germany,developmentA method to evaluate the transmissibility of new virus mutants was proposed.
Before the emergence of new coronavirus variants, such as the British variant b.1.1.7, the sars-cov-2 variant known as d614g had mutated from the original pathogen that caused the sars-cov-2 pandemic. D614g has rapidly spread to become the largest number of variants in the world, and this d614g variant is retained in all new variants. An international team, including researchers from Bern, has been able to demonstrate in laboratory and animal models why the d614g variant is superior to the original sars-cov-2 virus. "Our approach also allows us to better and faster describe emerging variants, such as the British variant b.1.1.7," said Volker Thiel of the Institute of Virology and Immunology (IVI), one of the four main authors of the study.
The results are important for assessing the risk of rampant new mutants, as they show how the adaptive advantages of viral variants lead to higher transmission. Scientists released the first results earlier, allowing scientific discussions on so-called preprint servers. The results have been published in full in the journal Nature. The d614g variant carries a spike glycoprotein mutation, which makes it easier for the virus to dock with human cells.
IVI and the David E. Wentworth Laboratory of the Centers for Disease Control and prevention in Atlanta first demonstrated that the d614g variant binds more strongly and replicates faster than the original virus in human cell cultures from the upper respiratory tract and nose. The increased replication rate of d614g variant was also confirmed in vivo, and a new mouse model was described for the first time in this study. These experiments were also carried out by the charaf benarafa team at IVI.
It is better to study the transmission of sars-cov-2 virus in other animals than in mice. Hamster and ferret are very mature in infection research, and they are particularly suitable animal models. To compare the two variants, the scientists injected an equal amount of mixture of the original version of sars-cov-2 virus and the d614g variant into each animal's nose under mild anesthesia. One day later, the experimentally infected animal was resettled with another healthy "sentinel" animal of the same species to assess the spread of direct competition between the two variants. The scientists repeated the experiment with a total of six pairs of animals. In almost all sentinel animals, the proportion of sars-cov-2 virus transmitted was largely occupied by d614g variants in the early stage.
Martin beer's team from the Federal Institute of animal health and the Friedrich Loeffler Institute used the latest sequencing and PCR techniques to differentiate the variants at Greifswald Insel RIEMS (d). Our study stands out because we are able to clearly identify more efficient transmission of mutant variants compared directly to the original variants, "Volker Thiel said.
Adaptability test of further mutation
This method can even be used to detect any single mutation or specific combination of mutations that exist in some virus variants in circulation. IVI relies on cloning technology developed in Bern a year ago, and sars-cov-2 virus can replicate accurately in the laboratory. Taking the British virus as an example, it is understood that there is not only one virus, but also more than 14 kinds of mutations, 8 of which occur in the spike glycoprotein. Therefore, with the help of cloning technology, the mutation of any number of variants can be reproduced and used to compete with each other in established cell cultures and animal models. The results showed how a single mutation affected the adaptability and transmissibility of the new variant. "Our testing strategy allows us to quickly check why other emerging virus variants have been established," olker Thiel said.
Similar research projects on infectious pathogens can also be carried out in the future at the newly established center for infectious diseases and Immunology (mcidi) of the University of Berne.