A team of virologists and bacterioologists from the University of Bern (Switzerland) have cloned the new coronavirus (SARS-CoV-2) in a high-security laboratory. Synthetic clones are being used by research groups around the world to analyze virus samples, find antiviral drugs and develop vaccines as quickly as possible without using samples from patients. The study has been published in the journal Nature .
The scientists, led by Volker Thiel and Joerg Jores, from the University of Bern, used the coronavirus sequence obtained in January as a standard. They divided the genome into fragments and commissioned a biotech company to synthesize fourteen DNA sequences. The company provided twelve of the fourteen, but the other two were obtained from samples from a person infected with SARS-CoV-2. The copies of DNA (deoxyribonucleic acid) that contained parts of the coronavirus genome were introduced into Brewer’s yeast cells ( Saccharomyces cerevisiae ) and assembled into a complete copy, finally obtaining an artificial yeast chromosome that carried the genetic information of the coronavirus. They then used them to produce infectious coronaviruses. All this was carried out in the high security laboratory of the Institute of Virology and Immunology (IVI) of the Federal Office for Food and Veterinary Safety (FSVO) in Mittelhäusern and in the Vetsuisse Faculty of the University of Bern.
“We replicated the virus in the space of a week,” said Professor Volker Thiel of the Institute of Virology and Immunology. The experts used a yeast cell system developed in Bern that, for the first time in history, has proven its worth in an epidemic situation like this. “We have optimized this system to allow us to quickly clone coronaviruses and other viruses,” adds Professor Jörg Jores from the Institute of Veterinary Bacteriology at the University of Bern. The Bern method allows a rapid response to new and fast-spreading viruses and their characteristics in real time, that is, during an outbreak, so it could be used in the future to combat other highly infectious viruses.
It does not matter?
The synthetic version of SARS-CoV-2 looks a lot like the real thing; however, the researchers observed some differences in replication. While it is true that some viruses can be cloned using a method that uses Escherichia coli bacteria for this purpose, coronaviruses can be difficult to clone using this technique. Hence, the researchers sought an alternative method using yeast cells previously developed at the University of Bern, known as transformation-associated recombination.
Viruses are just genetic material , be it DNA or RNA, wrapped in a protein coat. In the case of SARS-CoV-2, genome sequencing has shown that its “genetic code” consists of a single-stranded RNA molecule of approximately 30,000 bases containing 15 genes. To put us in context, the human genome is in the form of a double helix of DNA molecules made up of around 6.4 billion bases and with around 25,000 genes.
When infectious outbreaks occur, it takes precious time to obtain virus samples and take them to laboratories, and the transport of these agents is often considered too dangerous, which is why this method is so valuable, because it will allow the authorities Healthcare, pharmaceutical companies and research laboratories gain access to clinical samples without the need to transport viral samples from another location.
Referencia: Tran Thi Nhu Thao et al. Rapid reconstruction of SARS-CoV-2 using a synthetic genomics platform, Nature (2020). DOI: 10.1038/s41586-020-2294-9
