Several paramyxoviruses are of great public health importance causing decades of pandemics (such as Measles virus) and dangerous zoonosis (such as Nipah virus). In addition, new paramyxoviruses are continuously been discovered but no antiviral drug has been established yet. Their distinctive viral characteristic of syncytia formation in host cells was exploited to develop a novel split-green fluorescent screening assay, where non-functional fragments of a fluorescent protein attached to host cells, recombine and fluoresce when a syncytia is formed. The viability of the assay was confirmed through detecting infection and fusion by representative paramyxoviruses as well as testing against known broad-spectrum antiviral drugs. This protocol was subsequently used to screen for antiviral inhibitors in existing repurposed library of nearly 3000 compounds against Cedar virus, a non-pathogenic model Henipavirus. Two molecules, Cathepsin Inhibitor 1 and PF-543 were confirmed as potent inhibitors of Cedar virus, acting by blocking virus-induced cell-cell fusion. The assay is versatile as its mechanism targets the consequence of fusion rather than the specific viral protein which may enable application in other virus families that cause syncytia formation.
(SWM)
