Scientists introduce SARS-CoV-2 phenotype screening for figuring out novel antiviral medicine
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In a current examine posted to the bioRxiv* preprint server, researchers launched a phenotypic screening assay for figuring out compounds with extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) inhibition potential primarily based on caspase 3/7 activation.

Study: Identification of novel antiviral drug candidates utilizing an optimized SARS-CoV-2 phenotypic screening platform. Image Credit: Nhemz/Shutterstock

Several sorts of assays have been developed for the detection of SARS-CoV-2 variants, together with antibody-based assays for SARS-CoV-2 antigen detection and genetically modified assays; nevertheless, the assays have a number of drawbacks, similar to guide dealing with necessities or a slender vary of detection. Therefore, sturdy and broad but easy to carry out cell tradition assays are required to establish anti-SARS-CoV-2 medicine.

About the examine

In the current examine, researchers developed a high-throughput SARS-CoV-2 phenotypic screening assay for figuring out anti-SARS-CoV-2 compounds primarily based on the activation of caspase 3/7.

The human colon adenocarcinoma (Caco-2) cell line Caco-2-F03 was used for the cell tradition experiments. Additionally, Caco-2 cells have been obtained from a number of sources and designated as Caco-2A, -2B, and -2C to discriminate the authors’ unique Caco-2 cell line (Caco-2-F03) from the others. The staff in contrast Caco-2F03 to different cell tradition fashions that could possibly be used for figuring out potential anti-SARS-CoV-2 medicine. 

The susceptibility of Calu-3 (human lung carcinoma cell line), Caco-2-F03, A549-ACE2 (angiotensin-converting enzyme 2) and Vero cells to SARS-CoV-2 strains similar to G614, D614, Alpha, Beta, and Delta have been in contrast and confirmed by S immunostaining. Further, caspase exercise within the Caco-2-F03 cell line contaminated with totally different SARS-CoV-2 isolates was assessed at 24- and 48 hours post-infection (hpi).

The kinase inhibitor library comprising 1796 kinase inhibitors was screened for drug compounds that decreased SARS-CoV-2-induced caspase activation by >90%, together with recognized and potential medicine similar to twin specificity protein kinase (CLK-1), phosphoglycerate dehydrogenase (PHGDH), and colony-stimulating issue 1 receptors (CSFR) inhibitors. Remdesivir (10 µM) was used as a optimistic management. The staff additionally investigated if mixed remedy of NCT-503 and 2DG may additional improve anti-SARS-CoV-2 results in comparison with single drug remedy.

Caspase 3/7 exercise and SARS-CoV-2 S staining by totally different drug candidates have been in comparison with these of medicine with recognized anti-SARS-CoV-2 efficacy similar to remdesivir, EIDD-1931, ribavirin, nirmatrelvir, and nafamostat utilizing G614-infected Caco-2-F03 cells. The validity of caspase 3/7 assay outcomes was confirmed by evaluating anti-SARS-CoV-2 nucleocapsid (N) protein titers and Western Blot evaluation.

Air-liquid interface (ALI) cultures of bronchial epithelial (HBE) cells have been examined for mobile disruption throughout SARS-CoV-2 an infection by transepithelial electrical resistance (TEER) and SARS-CoV-2 cytotoxicity was assessed primarily based on lactic dehydrogenase (LDH) launch. SARS-CoV-2 genomic RNA ranges have been assessed primarily based on copy numbers detected by polymerase chain response (PCR).


Caco-2-F03 demonstrated the perfect efficiency because it contained a secure phenotype vulnerable to SARS-CoV-2 [indicated by high SARS-CoV-2 S levels and cytopathic effect (CPE) formation] and didn’t produce false-positive hits because of drug-induced phospholipidosis. Caco-2-F03 cells remained SARS-CoV-2-permissive for 30 passages with excessive ranges of mobile SARS-CoV, SARS-CoV-2 receptor ACE2 and transmembrane serine protease 2 (TMPRSS2).

Caspase-3/7 confirmed six-fold to eight-fold greater exercise in comparison with caspase-8 and 9, indicating better robustness due to this fact, caspase 3/7 detection was chosen for the screening. Caco-2-F03 cell an infection with totally different SARS-CoV-2 isolates successfully activated caspase 3/7, mirrored by SARS-CoV-2 S and RNA ranges. Caspase 3/7 exercise enabled monitoring of SARS-CoV-2 replication in cell traces similar to Vero cells and replication of human coronaviruses (hCoVs) such because the Middle East Respiratory syndrome CoV (MERS-CoV), HCoV-229E and SARS-CoV in CaCo-2-F03 cells.

Further, SARS-CoV-2-induced caspase 3/7 activation and CPE have been noticed in human pluripotent cardiomyocytes (CMS) and hepatocytes. Caspase 3/7 enabled the analysis of neutralizing antibody (nAb) titers in sera of seven donors obtained 14 days after the second messenger RNA (mRNA)-1273 vaccination. Greater G614 neutralization was noticed than Alpha and Gamma neutralization and the remdesivir-resistant pressure demonstrated enhanced sensitivity to ribavirin and EIDD-1931. Gly671Ser substitution within the RNA polymerase most likely mediated remdesivir resistance.

In the screening, 81 compounds with anti-SARS-CoV-2 exercise have been recognized with probably the most hits by CaMK (calmodulin-dependent protein kinase), mTOR (mammalian goal of rapamycin), ULK (unc-51 like autophagy activating kinase 1), CLK-1, TOPK (T-LAK cell-originated protein kinase), CSF-1R, and PAK (p21-activated kinases). NCT-503 (PHGDH inhibitor) inhibited Delta- and Omicron-induced caspase 3/7 activation and likewise inhibited SARS-CoV-2 replication in ALI cultures and the exercise of NCT-503 elevated on combining with the 2-deoxy-D-glucose (2DG, a hexokinase 2 inhibitor).

Overall, the examine findings confirmed that caspase 3/7 activation by totally different SARS-CoV-2 variants (together with remdesivir-resistant strains and different hCoVs) could possibly be used as a easy phenotypic high-throughput screening platform for figuring out anti-SARS-CoV-2 drug candidates with a broad vary of cell tradition fashions, unbiased of CPE.

*Important discover

bioRxiv publishes preliminary scientific experiences that aren’t peer-reviewed and, due to this fact, shouldn’t be thought to be conclusive, information medical apply/health-related habits, or handled as established data.

Journal reference:

  • Denisa Bojkova, Philipp Reus, Leona Panosch, et al. (2022). Identification of novel antiviral drug candidates utilizing an optimized 2 SARS-CoV-2 phenotypic screening platform. bioRxivdoi: material/10.1101/2022.07.17.500346v1

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