Rapid luminescence-based screening method for SARS- CoV-2 inhibitors discovery

Abstract

The COVID-19 pandemic has emphasized the necessity for rapid and adaptable drug screening platforms against live pathogenic viruses that require high levels of biosafety containment. Conventional antiviral testing is time-consuming and labor-intensive. Here, we outline the design and validation of a semi-automated drug-screening platform for SARS-CoV-2 that utilizes multiple liquid handlers, a stable A549 cell line expressing ACE2 and TMPRSS2 receptors, and a recombinant SARS-CoV-2 strain harboring the nano-luciferase gene. This platform allows for accelerated low-, mid-, and high-throughput screenings by bypassing the virus inactivation and the staining steps compared to assays utilizing fluorescent reporter viruses or immunofluorescence. First, we demonstrated that the luminescence signal obtained at 24 h post-infection is robust and can be used as a surrogate for fluorescent reporter viruses and immunofluorescence assays that require 48 h incubation post infection. We confirmed the susceptibility of the reporter virus to a panel of reference drugs and validated the luminescence signal in 96- and 384-well plates in accordance with NIH criteria for high-throughput screening. The validation assays showed reproducible results, robust Z factor of ≥0.5, and a coefficient of variation of <20% achieved in both 96 and 384-well plate formats. Lastly, we assessed the assay's performance by screening 240 compounds from the MMV Global Health Library, using the 384-well plate format and remdesivir as a control compound. The single point screening resulted in the identification of 48 hits that inhibited more than 50% of the viral growth. We selected the 15 most active compounds to evaluate their inhibitory concentration and their cytotoxicity, which resulted in the confirmation of the 3 most potent and least toxic compounds that were never reported as antivirals. These results confirm that our platform can be reliably employed for rapid drug screening against SARS-CoV-2 and can be easily adapted to other nano-luciferase reporter viruses.