Scientists from the USA and Switzerland have created a non-contagious copy of SARS-CoV-2.

American and Swiss researchers have created replicons of coronavirus – self-replicating RNAs that are identical to the virus, but they are not contagious. The scientists’ article was published in the journal Science.

To study the effect of such a contagious virus as SARS-CoV-2, specialists are forced to do this in compliance with strict protocols in biosafety laboratories. Replicons that copy almost every aspect of the virus’ life cycle can simplify their work. They are usually created by cloning the RNA genome into DNA fragments in test tubes, from which synthetic RNAs are then obtained. But the coronavirus RNA is extremely long.

Therefore, researchers from Berne and Rockefeller Universities, led by the Nobel laureate in Physiology or Medicine in 2020, Charles Rice, applied a different approach: fragments of the coronavirus genome were “collected” in small fragments, but not in test tubes, but in baker’s yeast. The resulting genome contains all the necessary information for virus replication – except for the “instructions” for assembling the S-protein, which allows the virus to penetrate and infect cells.

However, this protein is the main object of a large number of coronavirus studies. To get around this obstacle, the researchers expressed the S-protein in parallel with the replicon. The resulting particles can penetrate cells, but in their infectability, they are limited to one cycle of the life of the virus.

Virologists hope that their replicons will help scientists find out many previously unknown details of the coronavirus and test the effectiveness of drugs against COVID-19. So, in one of the experiments, scientists tested the effect of remdesivir on replicon. “We found that it suppresses replicon in the same concentrations as the real virus. This shows that the replicon system can be a reliable alternative to SARS-CoV-2 in the testing of various drugs,” said the first author of the work Inna Ricardo Lux.