Illinois pathobiology professor Ying Fang and her colleagues developed a reliable coronavirus test that can be used to detect and monitor infection in wild and domesticated animals. Credit: Fred Zwicky
Key Points:
- A new coronavirus test works across all species.
- The test focuses on the N-protein, which is embedded in the virus’s nucleocapsid and makes a better target.
- Validation tests showed more than 97% sensitivity and 98% specificity.
In an advance that will help scientists track coronavirus variants in wild and domesticated animals, researchers report they can now detect exposure to the SARS-CoV-2 virus in any animal species—without specialized chemical reagents. Instead, the new test focuses on antibodies against a protein, called the N-protein, that is embedded in the virus’s nucleocapsid—a structure made up of proteins and nucleic acids contained within a viral membrane.
“The N-protein is more abundant and it is more conserved than the proteins used in most tests,” said University of Illinois Urbana-Champaign pathobiology professor and virologist Ying Fang, who led the new research. This means that the structure of the protein is more consistent across species, making it a good target for all-species antibody tests.
In the study, published in mSphere, Fang and team used an N-protein-based blocking ELISA. This method involves coating an ELISA plate with the N-protein, then adding a serum sample of whatever animal is being tested. If the animal has been infected with the coronavirus, its serum will contain anti-N-protein antibodies, which will bind to the N-protein-coated plate. The scientists then wash the plate and add a secondary biotin-tagged monoclonal antibody that targets the N-protein.
If the animal is positive for coronavirus infection, its antibodies will block the secondary antibodies from binding to the N-protein. If the animal has not been infected, the monoclonal antibodies will attach to the coated plate and generate a color signal when specific chemicals are added to the plate.
The researchers validated their test using samples from various animals with known SARS-CoV-2 infection status, finding the tests had more than 97% sensitivity and 98% specificity. Further tests in domestic cats showed that the assay was able to detect infection within 7 days of exposure to the virus.
“Highly sensitive and specific diagnostic reagents and assays are urgently needed for rapid detection and implementation of strategies for prevention and control of the infection in animals,” the researchers conclude in their paper.