2021 年 3 巻 3 号 p. 72-76
The fusion of viral and cellular membranes is an important step in infections caused by enveloped viruses. Safe and rapid cell-based assay systems have been developed to identify inhibitors of various infections caused by enveloped viruses. In this review, we have described a cell-based membrane fusion assay and its application in drug screening. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Middle East respiratory syndrome coronavirus (MERS-CoV) induce membrane fusion by cleavage of the N-terminal region of the fusion peptide in the Spike protein by cellular proteases. To quantify the membrane fusion mediated by SARS-CoV-2 and MERS-CoV, effector cells expressing the Spike protein and target cells expressing the receptor and host protease TMRPSS2 were used. Cell fusion caused by co-culture was measured by monitoring the signals from dual split proteins (DSPs) as the reporter. Using this assay system, nafamostat was identified as a potential inhibitor of the membrane fusion caused by MERS-CoV and SARS-CoV-2. Clinical trials of nafamostat are underway. Cell-based membrane fusion assays using DSPs are expected to be useful for the discovery of viral infection inhibitors and for the evaluation of neutralizing antibodies.