Researchers create new type of COVID-19 antibody test

Scientists from the University of North Carolina School of Medicine have developed a new kind of antibody test for the novel coronavirus (COVID-19), a simplified experimental assay that could be ramped up to test thousands of blood samples at labs that do not have the resources of commercial labs and large academic medical centers, according to new research published in the journal Science Immunology.

As the COVID-19 pandemic continues with many thousands of new infections reported each day, there is a need for widely applicable surveillance testing to gain a better understanding of infection rates, especially the number of infections in people with mild or no symptoms, who can still be carriers, the researchers said.

The scientists created a blood test to pinpoint SARS-CoV-2 antibodies that target one unique piece of the SARS-CoV-2 spike protein. That piece is called a receptor binding domain (RBD). Their RBD-based antibody test can measure the levels of that domain, which they found correlate to the levels of the all-important neutralizing antibodies that provide immunity.

The RBD of the spike protein in SARS-CoV-2 is not shared among other known human or animal coronaviruses. Therefore, antibodies against this domain are likely to be highly specific to SARS-CoV-2, and so these antibodies reveal if an individual has been exposed to the virus that can cause COVID-19. When the researchers tested blood collected from people exposed to other coronaviruses, none had antibodies to the RBD of SARS-CoV-2.

"Our assay is extremely specific for antibodies to the virus that causes COVID-19, which is not the case for some currently available antibody tests," said Aravinda de Silva, PhD, MPH, co-senior author and professor of microbiology and immunology, in a statement. "Our results strongly support the use of RBD-based antibody assays for population-level surveillance and as a correlate of the neutralizing antibody levels in people who have recovered from SARS-CoV-2 infections."

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