Oral delivery of maize-produced porcine epidemic diarrhea virus spike protein elicits neutralizing antibodies in pigs

Key Message Transgenic expression of spike protein antigen S1 from Porcine Epidemic Diarrhea Virus in maize accumulated sufficient antigen for oral immunization and elicited serum neutralizing antibodies in pigs. Porcine Epidemic Diarrhea Virus (PEDV) causes severe diarrhea and mortality in piglets. Robust immunity may break the transmission cycle. Expression of antigens in maize grains is a promising method for producing low-cost vaccines. As a first step, we expressed maize constructs containing PEDV S1 spike protein targeted to various cellular locations including the cell wall, endoplasmic reticulum, and vacuole, and fused to carrier proteins E. coli heat labile subunit (LTB) and a dendritic cell (DC) binding peptide, and obtained sufficient antigen for oral immunization. Constructs targeting S1 to the ER or fused to carrier proteins produced high levels of antigen of greater than 20 mg/kg. Oral administration to pigs elicited serum neutralizing antibodies, supporting oral immunization as a practical and cost-effective PEDV vaccine.