RESUMEN
Aim: To develop a simple, inexpensive antiviral screening assay, applicable to SARS-CoV-2, using a plate-based bioassay approach to assess the in-vitro activity of compounds against HCoV-OC43. Background(s): Despite the successful deployment of vaccines against SARS-CoV-2 there remains a need for effective antivirals for acute infection treatment. A distinct problem facing the search for new anti-coronavirus compounds is the cost of antiviral screening, compounded by the biosecurity concerns of live SARSCoV- 2 culture. In concert with low pathogenic surrogate virus use, the resazurin reduction assay, which is often employed for compound cytotoxicity assessments can be employed for safe, rapid and inexpensive antiviral screening. Method(s): In-vitro cell based resazurin reduction assays were optimised using remdesivir as a control compound for the assessment of anti-HCoV-OC43 activity. Following optimisation, 246 purified natural compounds from the University of Western Australia's compound collection,were screened using the resazurin bioassay as a primary screen, under pre-treatment and cotreatment conditions. Five compounds, which demonstrated anti- HCoV-OC43 activity, were chosen for secondary screening with dose responses determined using qRT-PCR. Result(s): Primary screens of the 246 compounds using the resazurin bioassay identified five compounds with a relative viral inhibition >60% and a relative cell viability >70% (Table 1). The Z factor of the pre-treatment and co-treatment assays was >0.5 (average +/- SD;0.85 +/- 0.07, 0.91 +/- 0.03 respectively). Further dose response analysis of the top five compounds identified one compound with an IC50 value <10 muM. Conclusion(s): The method developed is an appropriate primary screening tool for the identification of novel compounds with anti-HCoV-OC43 activity.Copyright © 2023 Southern Society for Clinical Investigation.