Growth enhancement of porcine epidemic diarrhea virus (PEDV) in Vero E6 cells expressing PEDV nucleocapsid protein

More recently emerging strains of porcine epidemic diarrhea virus (PEDV) cause severe diarrhea and especially high mortality rates in infected piglets, leading to substantial economic loss to worldwide swine industry. These outbreaks urgently call for updated and effective PEDV vaccines. Better understanding in PEDV biology and improvement in technological platforms for virus production can immensely assist and accelerate PEDV vaccine development. In this study, we explored the ability of PEDV nucleocapsid (N) protein in improving viral yields in cell culture systems. We demonstrated that PEDV N expression positively affected both recovery of PEDV from infectious clones and PEDV propagation in cell culture. Compared to Vero E6 cells, Vero E6 cells expressing PEDV N could accelerate growth of a slow-growing PEDV strain to higher peak titers by 12 hours or enhance the yield of a vaccine candidate strain by two orders of magnitude. Interestingly, PEDV N also slightly enhances replication of porcine reproductive and respiratory virus, a PEDV relative in the Nidovirales order. These results solidify the importance of N in PEDV recovery and propagation and suggest a potentially useful consideration in designing vaccine production platforms for PEDV or closely related pathogens.