21 Oct 2020   |   Network Updates   |   Update from The Spanish National Research Council (CSIC)
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CSIC joins team developing infective clone of SARS-CoV-2 to study its molecular biology

Researchers from the Higher Council for Scientific Research (CSIC) have joined an international team to develop a fundamental tool to study the SARS-CoV-2 coronavirus.

The team has managed to generate an infective clone of SARS-CoV-2, which could enable scientists learnessential details of the viral cycle and its pathogenicity of the novel coronavirus, as well as to develop new antiviral treatments and live attenuated vaccines. The results have been published in the journal mBio .

The study was coordinatedby Luis Martínez-Sobrido, researcher at the Texas Institute for Biomedical Research in the United States. He was joined by scientists Fernando Almazán, the National Center for Biotechnology (CNB-CSIC), and Juan Carlos de la Torre, from the Scripps Research Institute of San Diego (La Joya, United States).

"The generation of infective clones of viruses belonging to the coronavirus family presents several technical difficulties due to the large size of the viral genome (around 30 kilobases) and the toxicity of certain sequences of the viral genome when they are amplified in bacteria", explains Fernando Almazán, contributor to the article.

“This work has resorted to the use of bacterial artificial chromosomes for the generation of a stable infective clone of SARS-CoV-2, since these plasmids allow cloning of large exogenous sequences and minimize toxicity problems. This technology has previously been successfully applied to generate infective clones of other coronaviruses and other viruses such as Zika ”, adds the researcher.

In this system, from synthetic DNA fragments that span the complete genome of the virus, a DNA copy of the viral genome is generated that is assembled on the bacterial artificial chromosome under the control of a promoter recognized by the cellular machinery. Subsequently, the generated infective clone is introduced into the cell, where it is transcribed by the cellular machinery, generating copies of the viral genome that initiate the infection cycle and give rise to infective viral particles.

Martínez-Sobrido highlights: "while the clones generated by other systems are more unstable, and require multiple plasmids, the use of bacterial artificial chromosomes allows the use of a single plasmid to generate synthetic viruses in cell cultures". In addition, "these clones are a powerful tool to learn details of the biology of SARS-CoV-2, such as what are the cellular factors that the virus needs in its expansion, a way to identify therapeutic targets, analyze the effectiveness of new antivirals and facilitate the development of live attenuated vaccines ”. Researchers have verified the stability of the virus produced and the effects of infection in hamsters, where they have observed that the pathogenicity and infectivity capacity is similar to that of the original virus.

Fernando Almazán points out the usefulness of this system for the genetic manipulation of the virus, the development of analysis systems to determine the effectiveness of new antivirals, and the elimination of virulence factors that lead to the production of live attenuated vaccines.

This article was first published on 20 October by CSIC.

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