Antiviral activity of interferon α-2b against SARS-CoV-2 in Calu-3 human lung adenocarcinoma cell culture
TL;DR
A study of recombinant IFNα-2b in a Calu-3 cell culture infected with SARS-CoV-2 demonstrated the possibility of highly sensitive determination of antiviral activity indicators such as 50% inhibitory concentration and selectivity index.
Abstract
INTRODUCTION. Despite the reclassification of the SARS-CoV-2 coronavirus as an etiological agent of seasonal respiratory viral infections, the problem of developing drugs against COVID-19 remains relevant. The development of antiviral drugs requires an adequate cellular model of infection to search for and test inhibitors of viral reproduction.
Aim
To study the feasibility of using a Calu-3 human lung adenocarcinoma cell culture-based test system to evaluate the antiviral activity of recombinant human interferon α-2b (IFNα-2b) against SARS-CoV-2.
Materials And Methods
SARS-CoV-2 coronavirus, Dubrovka strain (GenBank ID: MW514307.1) was grown in African green monkey kidney (Vero) cell culture. The infectious activity of the virus and the antiviral activity of IFNα-2b were determined in Vero and Calu-3 cell cultures. The antiviral activity of IFNα-2b in Calu-3 cells was assessed by viral antigen accumulation (In-Cell ELISA), and in the Vero cell-based reference test system by cell viability (MTT assay).
Results
Optimal conditions for evaluating antiviral activity in Calu-3 cells by measuring viral antigen accumulation in infected cells using In-Cell ELISA have been determined. A study of recombinant IFNα-2b in a Calu-3 cell culture infected with SARS-CoV-2 demonstrated the possibility of highly sensitive determination of antiviral activity indicators such as 50% inhibitory concentration (IC 50 ) and selectivity index. At different infection doses and treatment regimens, the Calu-3-based test system consistently showed greater sensitivity than the reference test system when evaluating IFNα-2b activity. Thus, in Calu-3 cells, the sensitivity of detecting IFNα-2b antiviral activity against SARS-CoV-2, expressed as IC 50 values, was more than 2 log 10 (i.e., 100- to 290-fold) higher than that in Vero cells. The observed differences in the sensitivity of the two test systems may be due to both the different endpoint measurement methods (viral antigen accumulation vs. cell viability) and the deficiency in interferon response genes in Vero cells.
Conclusions
When choosing a test system for evaluating the activity of immunomodulatory drugs (human IFNα-2b, interferon inducers), it is preferable to use Calu-3 cells and determine antiviral activity by viral antigen accumulation. In Vero cells, with assessment of antiviral activity based on cell viability, the therapeutic potential of such drugs may be greatly underestimated.