An Enzyme Linked Immunoassay (ELISA) to Detect Classical Swine Fever Antibodies and to Differentiate Infected from Vaccinated Animals (DIVA)

Scientific Abstract

Classical swine fever (CSF) outbreaks can pose serious threats to pork producers and the swine industry. Although mostly eradicated in the U.S. and other pork producing countries, the threat of CSF prevails. In China, CSFV genotype 2 isolates dominate the epizootics, which led China to develop the first subunit vaccine in 2018, Tian Wen Jing, TWJ-E2. TWJ-E2 contains a baculovirus-expressed E2 glycoprotein from a CSFV vaccine strain (genotype 1.1), which is cross-protective against different virulent genotype 2 Chinese field isolates. TWJ-E2 has been licensed in China and commercialized. Although genetic tests are commonly used to detect viruses, a serodiagnosis of disease and vaccination provides an important alternative. Serology tests can provide critical information about immune responses to infections and vaccines, such as an antibody titer, which cannot be derived from a genetic test. An enzyme linked immuno-assay (ELISA) is a common and accessible test format for serodiagnosis that allows high through-put testing (96-384 samples per test run) to detect immune responses to disease and vaccination. However, there are currently no USDA approved ELISA tests for CSF in the U.S. The overarching goal of our research is to produce an ELISA test to diagnose CSF infections and CSF vaccinated animals, also known as a ‘differentiating infected from vaccinated animals’ (DIVA) test. We aimed to develop enzyme linked immunosorbent-assay (ELISA) tests to detect antibodies against wild-type CSF virus and the CSF E2 subunit vaccine. The blocking and competitive ELISA formats (bELISA and cELISA) use monoclonal antibodies, which are highly specific and prevent false positive results. Most DIVA tests require two tests for each target, one for virus and one for vaccine. We aimed to develop a combined format, a dual-plex bELISA, which can detect antibodies for infections and vaccines in a single test. During this project, we generated CSF monoclonal antibodies and diagnostic reagents for surveillance of CSF infections, vaccinations, and immunity status.