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Virology and veterinary bacteriology researchers at the Swiss University of Bern have succeeded in cloning the novel SARS CoV-2 coronavirus. The scientists were able to recreate the coronavirus from synthetic DNA (deoxyribonucleic acid) in the high-security laboratory of the Institute of Virology and Immunology (IVI) of the Federal Food Safety and Veterinary Office (FSVO) in Mittelhäusern and at the Vetsuisse Faculty of the University of Bern. Corona samples can now be tested worldwide with these clones. This will also help discover drugs that will combat the viral disease and in the development of vaccines.

How the virus was cloned

Viruses, like parasites, depend on a host cell in order to reproduce. The viruses invade the body’s cells and reprogram them so that they produce new viruses. These are then spread further, for instance through infection from droplets. The scientists in Bern have now reproduced segments of the coronavirus genome from synthetic DNA. These were then introduced into yeast cells. There they were reassembled by means of what is referred to as transformation-associated recombination (TAR) cloning.

This resulted in a yeast artificial chromosome (YAC) on which the genetic information of the virus was stored. In the next step, infectious RNA was reproduced in vitro without yeast cells. This was done with the help of  T7 RNA polymerase. This RNA was introduced into animal cells, where new, synthetic coronaviruses were then replicated. As in clones. And all this was accomplished in record time. “We replicated the virus within the space of a week,”, notes Professor Volker Thiel from the Institute of Virology and Immunology (IVI).

First test successful

The scientists report that the system of yeast cells was developed in Bern and has now proved its worth for the first time during an epidemic. “We have optimized this system to allow us to clone coronaviruses and other viruses quickly,” explains Prof. Jörg Jores from the Institute of Veterinary Bacteriology at the University of Bern. This method enables a rapid response to novel and fast-spreading viruses and their properties in real-time. In other words, during an outbreak.

The final results of the study were published in the academic journal Nature. This was after the provisional results had already been posted on a preprint server where it underwent scientific discussion is. The researchers state that the synthetic viruses cloned in Bern have enabled a major step forward in the diagnosis of patient samples and the development of new active substances. Viruses are especially difficult to clone because they are smaller than the smallest bacteria and extremely mutable. “Our model system that uses yeast cells shows that it is ideally suited for reconstructing coronaviruses and other viruses,” Volker Thiel adds.

This method developed by the Swiss researchers will also be suitable in the future for combating other extremely infectious viruses. Moreover, the scientists have already received numerous requests from companies and other researchers to test potential active substances against the SARS-CoV-2 coronavirus at the high-security laboratory.