Use of two enzyme-linked immunosorbent assays to monitor antibody responses in swine with experimentally induced infection with porcine epidemic diarrhea virus

Abstract

Summary A blocking elisa was developed to detect antibodies directed against porcine epidemic diarrhea virus (pedv). The pedv antigen was first incubated with dilutions of test sera. Any antigen that was not blocked by antibodies in the serum was assayed in a double-antibody sandwich elisa, using 2 monoclonal antibodies directed against different antigenic sites on pedv as capture and detecting antibodies, respectively. The blocking elisa was compared with a fixed-cell elisa that used monolayers of Vero cells infected with pedv prototype strain CV777 as a solid phase and a conjugate of an IgG-specific monoclonal antibody for antibody detection. Pigs were inoculated with pedv strain CV777 or 1 of 2 field isolates, and antibody responses were measured by use of the 2 tests. Antibodies were detected by the blocking elisa as early as postinoculation day 7 and, by the fixed-cell elisa, as early as postinoculation day 14. From day 14 on, antibody titers for both tests correlated highly. Titers for the fixed-cell elisa were 5.4 times higher than those for the blocking elisa. The latter technique is easier to perform and discriminates well between infected and noninfected pigs, which makes this test useful for routine diagnosis and serologic surveys of porcine epidemic diarrhea.