Detection of pseudorabies virus antibody in swine serum oral fluid specimens using a recombinant gE glycoprotein dual matrix indirect ELISA

Authors: CHENG, TING-YU - Iowa State University; MAGTOTO, RONALDO - Iowa State University; HENAO-DIAZ, ALEXANDRA - Iowa State University; POONSUK, KORAKRIT - Iowa State University; Buckley, Alexandra; VAN GEELEN, ALBERT - Animal And Plant Health Inspection Service (APHIS); Lager, Kelly; ZIMMERMAN, JEFF - Iowa State University; GIMENEZ-LIROLA, LUIS - Iowa State University

Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2021
Publication Date: 8/27/2021
Citation: Cheng, T., Magtoto, R., Henao-Diaz, A., Poonsuk, K., Devries, A.C., Van Geelen, A., Lager, K.M., Zimmerman, J., Gimenez-Lirola, L. 2021. Detection of pseudorabies virus antibody in swine serum oral fluid specimens using a recombinant gE glycoprotein dual matrix indirect ELISA. Journal of Veterinary Diagnostic Investigation. 33(6). p. 1106-1114. https://doi.org/10.1177/10406387211040755.
DOI: https://doi.org/10.1177/10406387211040755

Interpretive Summary: Pseudorabies virus (PRV) is a herpesvirus whose natural host is swine. Infection can result in central nervous system, reproductive, and respiratory clinical signs, which vary in severity with age of infection. PRV has been eradicated from the United States (US) domestic swine herd, but the virus can be found in some feral swine populations. Many other countries have also been successful in eradicating PRV from their domestic swine herds. However, in China PRV is endemic and there have been reports of highly pathogenic PRV isolates in swine. Thus, there has been renewed interest in ensuring there are validated diagnostic assays in preparation for control and elimination of PRV if it were to infect the US domestic swine herd. An important tool to eliminate a virus from the swine population is being able to differentiate infected from vaccinated animals (DIVA). A PRV DIVA vaccine has being developed that has a deletion in the region of the genome the encodes glycoprotein E (gE). Therefore, animals that have been exposed to wild-type PRV would have antibodies to gE, while vaccinated animals would not. In addition, for control and elimination strategies, sampling large groups of swine quickly is advantageous and oral fluids have emerged as an easy to collect aggregate sample. But, studies need to be performed to ensure that the current diagnostic platforms for serum are validated for swine oral fluids. In this study, pigs were challenged with wild-type PRV, vaccinated with a commercial PRV vaccine or vaccinated and then challenged with wild-type PRV. Oral fluids and serum were collected from these animals of known PRV status along with negative control animals. The samples were tested for gE antibodies using a commercial blocking ELISA (bELISA) and a dual matrix (serum and oral fluid) indirect IgG gE ELISA (iELISA). ROC analysis of serum bELISA, serum iELISA, and oral fluid iELISA showed no significant differences in performance. Overall, the data supported PRV surveillance based on oral fluid samples using an indirect gE ELISA.

Technical Abstract: Pseudorabies (Aujeszky’s disease) virus (PRV) was eliminated from domestic swine in many countries using glycoprotein E (gE) deleted vaccines and serum antibody gE ELISAs, but PRV continues to circulate in some regions and in most feral swine populations in the world. In this study, a dual matrix (serum and oral fluid) indirect IgG gE ELISA (iELISA) was created and its performance evaluated using samples from 4 treatment groups (10 pigs each): negative control (NC), vaccination (MLV), PRV inoculation (PRV), and vaccination followed by challenge (MLV-PRV). All serum and oral fluid samples collected prior to PRV challenge and all NC samples throughout the study were negative for gE antibodies by commercial blocking ELISA (bELISA) and iELISA. Nasal swab samples from 9 of 10 animals in the PRV group were gB qPCR positive at 2 days post inoculation (DPI). The oral fluid iELISA detected a significant S/P response in the PRV (p equal 0.03) and MLV-PRV (p equal 0.01) groups by 6 DPI. ROC analyses of serum bELISA (n equal 428), serum iELISA (n equal 426), and oral fluid iELISA (n equal 247) showed no significant differences in performance (p greater than 0.05). Overall, the data supported the concept of a PRV surveillance based on oral fluid samples tested on an indirect gE ELISA.