SARS-CoV-2 Permissive glioblastoma cell line for high throughput antiviral screening

Abstract

Despite the great success of the administered vaccines against SARS-CoV-2, the virus can still spread, as evidenced by the current circulation of the highly contagious Omicron variant. This emphasizes the additional need to develop effective antiviral countermeasures. In the context of early preclinical studies for antiviral assessment, robust cellular infection systems are required to screen drug libraries. In this study, we reported the implementation of a human glioblastoma cell line, stably expressing ACE2, in a SARS-CoV-2 cytopathic effect (CPE) reduction assay. These glioblastoma cells, designated as U87.ACE2⁺, expressed ACE2 and cathepsin B abundantly, but had low cellular levels of TMPRSS2 and cathepsin L. The U87.ACE2⁺ cells fused highly efficiently and quickly with SARS-CoV-2 spike expressing cells. Furthermore, upon infection with SARS-CoV-2 wild-type virus, the U87.ACE2⁺ cells displayed rapidly a clear CPE that resulted in complete cell lysis and destruction of the cell monolayer. By means of several readouts we showed that the U87.ACE2⁺ cells actively replicate SARS-CoV-2. Interestingly, the U87.ACE2⁺ cells could be successfully implemented in an MTS-based colorimetric CPE reduction assay, providing IC₅₀ values for Remdesivir and Nirmatrelvir in the (low) nanomolar range. Lastly, the U87.ACE2⁺ cells were consistently permissive to all tested SARS-CoV-2 variants of concern, including the current Omicron variant. Thus, ACE2 expressing glioblastoma cells are highly permissive to SARS-CoV-2 with productive viral replication and with the induction of a strong CPE that can be utilized in high-throughput screening platforms.

Keywords: Antiviral screen; CPE; Glioblastoma; Omicron; SARS-CoV-2; U87 cell line.