# A novel luciferase-based assay for quantifying coronavirus-induced syncytia

## TL;DR

A new high-throughput luciferase-based assay efficiently quantifies coronavirus-induced cell fusion, aiding in antiviral drug discovery.

## Contribution

A novel split luciferase system is introduced for high-throughput detection of coronavirus-induced syncytia.

## Key findings

- The split Gaussia luciferase system effectively measures syncytial formation in a high-throughput manner.
- The assay is applicable to both feline coronavirus and SARS-CoV-2.
- This method accelerates antiviral drug discovery by enabling efficient quantification of cell fusion.

## Abstract

Coronaviruses can induce cell‒cell fusion that results in the formation of multinucleated syncytia through the interaction of viral spike proteins with host cell receptors. Quantifying syncytial formation is crucial for screening potential efficacious antiviral compounds. However, some traditional methods for syncytial quantification are often labor-intensive and limited by a low-throughput capacity. Therefore, we developed a novel high-throughput assay for the efficient quantification of syncytial formation induced by feline coronavirus (FCoV) and SARS-CoV-2. This assay, which is based on the split luciferase system, utilizes a split Gaussia luciferase (Gluc) system. In this system, fragments of Gluc are fused to the multimerizing Tau protein to reconstitute enzymatic activity upon cell fusion. In this study, the activity of the reconstituted luciferase was measured in 20 µL of culture medium to efficiently quantify syncytial formation induced by FCoV and SARS-CoV-2. Our findings demonstrate that this assay can accelerate the discovery of antiviral drugs that target coronaviruses.

The online version contains supplementary material available at 10.1038/s41598-025-02037-4.