Respiratory Syncytial Virus Fusion Activity Syncytia Assay.

The methods detailed here measure the membrane fusion activity of viral fusion proteins and are optimized for the respiratory syncytial virus (RSV). RSV utilizes a class I fusion protein (F) to facilitate fusion between a viral and cellular membrane to allow viral entry into host cells. This process is carried out with the assistance of the glycoprotein (G), which attaches to the host-cell surface, allowing F to interact with the target cell. The F protein then undergoes conformational changes, which drive membrane fusion, thus creating a path for viral entry. The fusogenic activity of viral fusion proteins can be quantified by observing and measuring syncytia formation via wide-field microscopy. Syncytia are multinucleated cell masses formed by cell-cell membrane fusion, which in this case are driven by viral fusion proteins expressed on the host-cell surface.