Evaluation of serological tests for the detection of pseudorabies gE antibodies during early infection.

Two enzyme-linked immunosorbent assays (ELISAs) and a particle concentration fluorescence immunoassay (PCFIA) were compared for their ability to detect antibodies against pseudorabies virus (Aujeszky's disease virus) glycoprotein E (gE) in the early stages of infection in pigs previously vaccinated with gE-deleted pseudorabies vaccines. Seventy pigs were included in the study. Five groups of 6 pigs each were vaccinated with one of 5 different pseudorabies virus (PRV) gE-deleted vaccines, and subsequently infected intranasally with 10(5.6) TCID50 of the Iowa 4892 pneumotropic strain of PRV. This entire procedure was repeated using 10(4.6) TCID50 of the Rice strain of PRV. Five unvaccinated control pigs were also challenged with each virus strain. Three control pigs died before seroconverting, leaving 67 pigs for comparison. Blood samples were drawn from experimentally inoculated pigs on the day of vaccination, the day of challenge, and on 4-10, 14, and 21 days postchallenge (DPC). Serology test sensitivity estimates and comparisons among tests were made for each sampling day. Results of this study demonstrated differences among the tests in the time from inoculation to initial antibody detection, and the time to detect 50% and 75% of the infected pigs. The average time until first detection of pigs as seropositive for gE antibodies by PCFIA was 7.5 DPC. The blocking ELISA detected pigs as seropositive an average of 8.8 DPC, and the indirect ELISA first detected gE antibodies by 9.3 DPC. Fifty percent of the pigs were detected as seropositive by days 7, 8, and 9 for the PCFIA, blocking ELISA, and indirect ELISA, respectively. Similarly, 75% of the pigs were detected as seropositive by days 8, 9, and 10 for the PCFIA, blocking ELISA, and indirect ELISA, respectively. All pigs were detected as seropositive by 14 DPC for all 3 tests.