Fig. 4.

Amiodarone (class II) inhibits the early stage of coronavirus infection. a) Antiviral activity of amiodarone demonstrated by an immunofluorescence-based MERS-CoV infection assay. In total, ten different concentrations (1–50 μM) of amiodarone were examined, and immunofluorescence images obtained from low (3.12 μM) and high (50 μM) compound concentrations were selected. Green signals represent cells infected with MERS-CoV and red signals indicate cell survival. b) Viral mRNA from cells infected with MERS-CoV quantified by qRT-PCR. Each data point represents the mean ± SEM of triplicate assays. c) Time-of-addition experiment performed by addition of 10 μM amiodarone at different time points during MERS-CoV infection. Drugs were added at 1 h before infection (−1), at the time of infection (0), or at various hours post-infection (+1 ∼ +6), and the extent of inhibition of the MERS-CoV infection was quantified by the immunofluorescence signals. Chloroquine and lopinavir were included at a concentration of 10 μM for comparison. Each data point represents the mean ± SEM of triplicate assays. d) Antiviral activity of amiodarone examined against the HCoV-229E and HCoV-OC43 viruses. Viruses were infected into Vero cells in the presence of amiodarone, and after 24 h of infection, viral mRNA was quantified by qRT-PCR. Each data point represents the mean ± SEM of triplicate assays. e) Graphical presentation of potential mechanisms of the antiviral activity of amiodarone. Amiodarone, as a weak base, could lead to an alkalization of the lysosome and therefore act as a potential inhibitor of lysosomal acid sphingomyelinase. ASM, acid-sphingomyelinase; AM, acid-sphingomyelin.