Evaluation of antibody response of killed and live vaccines against porcine epidemic diarrhea virus in a field study.

Background: Porcine epidemic diarrhea virus (PEDV) is an infectious, highly contagious virus, and is an etiological agent of acute entero-pathogenic diarrhea in swine. Objectives: Evaluation of the antibody response of two types of PEDV vaccines is to be carried out. Animals and methods: Sows were vaccinated with either live or killed commercial PEDV SM98 (GenBank: GU937797.1) vaccines. Four different groups of sows with five sows in each group were used in this study: the unvaccinated negative control group, the killed virus vaccination group with killed virus boosting (K/K), the live virus vaccinated group with live virus boosting (L/L), and the combination group vaccinated with live virus and subsequently boosted with killed vaccine (L/K). Sows were vaccinated intramuscularly twice at four and two weeks prior to farrowing with 2ml/head vaccine dose. Antibody titers in sow and piglet serum one week after farrowing and that in colostrum were compared by enzyme-linked immunosorbent assay (ELISA) and serum neutralization test. Results: Vaccination with K/K vaccine induced the highest level of IgG and IgA in sow serum, colostrum, and especially in piglet serum, with the lowest levels found in the L/L group. The major neutralizing activity was also found in the K/K group, particularly in colostrum, with piglets bearing higher neutralizing activity compared to sow sera. Among recombinant spike S1, S2, S3, and nucleocapsid N protein of PEDV, S3 protein presented the highest antibody level in the K/K group. Conclusion: Killed PEDV SM98 vaccine induced higher antibody levels. Clinical importance: This study clearly confirms that killed vaccine has induced higher antibody levels and may contribute to the design of future research and vaccine programs.