In vitro comparison of SARS-CoV-2 variants

The Coronaviridae family hosts various coronaviruses responsible for many diseases, from the common cold, severe lung infections to pneumonia. SARS-CoV-2 was discovered to be the etiologic agent of the Coronavirus pandemic, and numerous basic and applied laboratory techniques were utilized in virus culture and examination of the disease. Understanding the replication kinetics and characterizing the virus effect on different cell lines is crucial for developing in vitro studies. With the emergence of multiple variants of SARS-CoV-2, a comparison between their infectivity and replication in common cell lines will give us a clear understanding of the characteristic differences in pathogenicity. In this study, we compared the cytopathic effect (CPE) and replication of Wild Type (WT), Omicron (B.1.1.529), and Delta (B.1.617.2) variants on 5 different cell lines; VeroE6, VeroE6 expressing high endogenous ACE2, VeroE6 highly expressing human ACE2 (VeroE6/ACE2) and TMPRSS2 (VeroE6/hACE2/ TMPRSS2), Calu3 cells highly expressing human ACE2 and A549 cells. All 3 VeroE6 cell lines were susceptible to WT strain, where CPE and replication were observed. Along with being susceptible to Wild type, VeroE6/hACE2/TMPRSS2 cells were susceptible to both omicron and delta strains, whereas VeroE6/ACE2 cells were only susceptible to omicron in a dose-dependent manner. No CPE was observed in both human lung cell lines, A549 and Calu3/hACE2, but Wild type and omicron replication was observed. As SAR-CoV-2 continues to evolve, this data will benefit researchers in experimental planning, viral pathogenicity analysis, and providing a baseline for testing future variants.