FDA authorizes COVID-19 diagnostic that uses immune cells

The US Food and Drug Administration has given Adaptive Biotechnologies an emergency use authorization for its COVID-19 diagnostic kit, which examines immune cells called T cells to determine whether a person was previously infected with SARS-CoV-2, the virus that causes COVID-19. The test, called T-Detect COVID, is the first of its kind available to US consumers.

When a person is infected with SARS-CoV-2, T cells latch onto bits of viral proteins that emerge on the surface of an infected cell. They latch via a protein called the T-cell receptor (TCR), which is genetically unique to each individual T cell. T cells last a long time and can ramp back up if a person gets infected again with the same microbe.

Adaptive’s chief medical officer, Lance Baldo, says the firm uses a combination of gene sequencing and bioinformatics to examine a person’s TCRs for genetic information that suggests the person encountered SARS-CoV-2 at some point. A laboratory technician isolates T cells from a tube of blood, sequences the TCRs, and scans the various sequences, looking for genetic signatures that correspond to T cells that have interacted with viral proteins.

The company developed its T-cell bioinformatics program in collaboration with Microsoft and validated the test using human blood samples taken before and after SARS-CoV-2 emerged. In developing the kit, Adaptive found that the test could detect a positive result 97% of the time and a negative result 100% of the time, Baldo says.

There are other diagnostics that look at immune responses—namely, the presence of antibodies to the virus. Most of those tests are designed to look for one particular antibody, and antibody levels fade over time. Baldo says one of the strengths of Adaptive’s test is that it is broad—it can detect nearly any TCR that corresponds to the virus and can identify TCRs that correspond to variants. The test costs $150.