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 (PEDV-S(FCS)) with an artificial furin protease cleavage site N-terminal of the putative fusion peptide. PEDV-S(FCS) exhibited trypsin-independent cell-cell fusion and was able to replicate in culture cells independent of trypsin, though to low titer