In vitro Activity Study of Chansu Injection against SARS-CoV-2 Virus Infection

OBJECTIVE To investigate the in vitro activity of Chansu injection against SARS-CoV-2 infection and determine whether bufalin is the primary active component responsible for its efficacy.

METHODS The half-maximal effective concentration (EC₅₀) of Chansu injection and bufalin against SARS-CoV-2 infection was determined using the CellTiter-Glo cell viability assay. qPCR was performed to assess the effects of Chansu injection and bufalin on mRNA levels of SARS-CoV-2 NP protein, inflammatory factors, and interferons in virus-infected cells. A cell-cell membrane fusion model was established, and the impact of the drugs on membrane fusion between HEK-293T and HEK-293T-ACE2 cells was evaluated using a luciferase reporter gene assay.

RESULTS Chansu injection exhibited anti-SARS-CoV-2 virus infection activity, with an EC₅₀ of 85.56 ng·mL^-1. Chansu injection significantly reduced the mRNA levels of viral NP protein (P < 0.05), IFN-λ2/3 (P < 0.05), ISG-15 and RIG-I (P < 0.000 1) in SARS-CoV-2 infected Calu-3 cells, and the mRNA levels of inflammatory factors IL-6 and TNF-α were significantly reduced (P < 0.000 1). The EC₅₀ of bufalin in inhibiting SARS-CoV-2 virus-infected cells was 13.3 nmol·L^-1, which might be the main active component of Chansu injection in resisting SARS-CoV-2 virus-infected cells. Chansu injection could significantly inhibit the cell membrane fusion mediated by the S protein of SARS-CoV-2 virus, thereby blocking the virus invasion.

CONCLUSION Chansu injection demonstrates in vitro anti-SARS-CoV-2 activity by suppressing NP protein expression, reducing inflammatory cytokine levels, and blocking viral entry through membrane fusion inhibition. Bufalin is likely the key active component responsible for its anti-SARS-CoV-2 effects.