S1 domain of the porcine epidemic diarrhea virus spike protein as a vaccine antigen

Makadiya, Niraj; Brownlie, Robert; van den Hurk, Jan; Berube, Nathalie; Allan, Brenda; Gerdts, Volker; Zakhartchouk, Alexander

Amongst three eukaryotic expression systems, the highest production of S1 was achieved using a mammalian expression with the TPA signal sequence. This method of expression can be used to produce large amount of S1 for vaccine, diagnostic and research purposes. A sow vaccinated three times with the S1 subunit vaccine had high IgG titres and high virus neutralization titres in the serum as compared to the control sow. Also, high levels of IgG and IgA titers were found in the colostrum of the vaccinated sow. Furthermore, maternal transfer of antibody was demonstrated as only the serum of suckling piglets had high titres of S1 specific IgG and viral-neutralizing antibody. There was higher survival rate among of piglets of vaccinated sow (87.5 %) than in the piglets of control sow (42.9 %) after oral PEDV challenge (P = 0.0002). These survival rates suggest the potential of the S1 protein subunit vaccine in preventing piglet mortality. The vaccinated sow's piglets exhibited lower clinical signs of disease except diarrhea throughout the six day post-challenge period than control piglets. Surprisingly, there was no difference in average weight and PEDV shedding among two groups of piglets. These observations suggest the inability of the S1 subunit vaccine in our experiment to control all PED clinical signs although more experiments involving a large number of sows are needed to confirm these findings.