A Single Point Mutation Creating a Furin Cleavage Site in the Spike Protein Renders Porcine Epidemic Diarrhea Coronavirus Trypsin Independent for Cell Entry and Fusion

The emerging porcine epidemic diarrhea virus (PEDV) requires trypsin supplementation to activate its S protein for membrane fusion and virus propagation in cell culture. By substitution of a single amino acid in the S protein, we created a recombinant PEDV with an artificial furin protease cleavage site N terminal of the putative fusion peptide (PEDV-SFCS). PEDV-SFCS exhibited trypsin-independent cell-cell fusion and was able to replicate in culture cells independently of trypsin, though to low titer.