ABSTRACT
This study aims to investigate the protective effect of infected piglets which were immunized with different dose of inactivated porcine epidemic diarrhea virus (PEDV) vaccines. The number of infective virus particles and total virus particles of PEDV with different concentrations were determined, and the mice were immunized with different concentration vaccine prepared as antigen, respectively. The humoral and cellular immune production were determined by ELISA antibody detection method, neutralization test and ELISPOT method. Vaccine with appropriate antigen content was selected to immunize piglets, then the antibody was determined. The relationship between concentrated vaccine and protective effect was studied by challenge experiment. The results showed that, when the antigen dose was equal or greater than 8x106 pfu.mL-1, the inactive vaccine could effectively stimulate mice to produce humoral and cellular immunity. The piglets immunized with 2 mL inactivated PEDV vaccine containing 8x106 pfu.mL-1 antigen could resist diarrhea and continuous viral shedding caused by PEDV challenge. Compared with the total number of virus particles, the number of infectious virus particles was significantly correlated with antibody production (r=0.998 1), and neutralization titer was significantly correlated with piglet protection (r=0.974 7). PEDV inactivated vaccine can provide good immune protection, in which the number of infectious virus particles is the key factor to improve the antibody level. Antibody titer, as an index of humoral immunity, is an important reference for judging immune protection.