Detection of pseudorabies virus antibody in swine oral fluid using a serum whole-virus indirect ELISA

Authors: CHENG, TING-YU - Iowa State University; Buckley, Alexandra; VAN GEELEN, ALBERT - Animal And Plant Health Inspection Service (APHIS); Lager, Kelly; HENAO-DIAZ, ALEXANDRA - Iowa State University; POONSUK, KORAKRIT - Iowa State University; PINEYRO, PABLO - Iowa State University; BAUM, DAVID - Iowa State University; JI, JU - Iowa State University; WANG, CHONG - Iowa State University; MAIN, RODGER - Iowa State University; 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: 4/13/2020
Publication Date: 5/25/2020
Citation: Cheng, T., Buckley, A.C., Van Geelen, A., Lager, K.M., Henao-Diaz, A., Poonsuk, K., Pineyro, P., Baum, D., Ji, J., Wang, C., Main, R., Zimmerman, J., Gimenez-Lirola, L. 2020. Detection of pseudorabies virus antibody in swine oral fluid using a serum whole-virus indirect ELISA. Journal of Veterinary Diagnostic Investigation. https://doi.org/10.1177/1040638720924386.
DOI: https://doi.org/10.1177/1040638720924386

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. In order to sample large groups of swine quickly in an outbreak, oral fluids have emerged as an easy to collect aggregate sample. But, studies need to be performed to ensure that the current diagnostic platforms 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 antibodies using a serum PRV whole-virus ELISA. Both samples had similar patterns of detection and analysis demonstrated that adapting the serum based assay to the oral fluids matrix had good diagnostic performance and excellent repeatability; therefore, oral fluids could be a useful tool for PRV surveillance and detection.

Technical Abstract: We evaluated the detection of pseudorabies virus (PRV) antibodies in swine oral fluid. Oral fluid and serum samples were obtained from 40 pigs allocated to 4 treatment groups (10 pigs/group): negative control (NC); wild-type PRV inoculation (PRV 3CR Ossabaw; hereafter PRV); PRV vaccination (Ingelvac Aujeszky MLV; Boehringer Ingelheim; hereafter MLV); and PRV vaccination followed by PRV inoculation at 21 d post-vaccination (MLV-PRV). Using a serum PRV whole-virus indirect IgG ELISA (Idexx Laboratories) adapted to the oral fluid matrix, PRV antibody was detected in oral fluid samples from treatment groups PRV, MLV, and MLV-PRV in a pattern similar to serum. Vaccination alone produced a low oral fluid antibody response (groups MLV and MLV-PRV), but a strong anamnestic response was observed following challenge with wild-type virus (group PRV). Analyses of the oral fluid PRV indirect IgG ELISA results showed good binary diagnostic performance (area under ROC curve equal 93%) and excellent assay repeatability (intra-class correlation coefficient equal 99.3%). The demonstrable presence of PRV antibodies in swine oral fluids suggests the possible use of oral fluids in pseudorabies surveillance.