Evaluation of formulations to improve SARS-CoV-2 viability and thermostability after lyophilisation.

In the context of the COVID-19 pandemic, virus collections such as EVA-GLOBAL play a key role in the supply of viruses and related products for research. Freeze-drying techniques for viruses represent a method of choice for the preservation of strains and their distribution without the need for a demanding cold chain. Here, we describe an optimised lyophilisation protocol usable for SARS-CoV-2 strains that improves preservation and thermostability. We show that sucrose used as an adjuvant represents a simple and efficient stabilizer providing increased protection for long-term preservation and shipment of the virus under different climatic conditions.

Favipiravir strikes the SARS-CoV-2 at its Achilles heel, the RNA polymerase.

The ongoing Corona Virus Disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has emphasized the urgent need for antiviral therapeutics. The viral RNA-dependent-RNA-polymerase (RdRp) is a promising target with polymerase inhibitors successfully used for the treatment of several viral diseases. Here we show that Favipiravir exerts an antiviral effect as a nucleotide analogue through a combination of chain termination, slowed RNA synthesis and lethal mutagenesis. The SARS-CoV RdRp complex is at least 10-fold more active than any other viral RdRp known. It possesses both unusually high nucleotide incorporation rates and high-error rates allowing facile insertion of Favipiravir into viral RNA, provoking C-to-U and G-to-A transitions in the already low cytosine content SARS-CoV-2 genome. The coronavirus RdRp complex represents an Achilles heel for SARS-CoV, supporting nucleoside analogues as promising candidates for the treatment of COVID-19.