Detecting a T cell-mediated immune response might be the next frontier in Covid-19 testing. Qiagen, which already makes tests for the coronavirus’s RNA and antigens as well as for antibodies produced by Covid-19 patients, has just cut a deal to move into T-cell testing too.
The Dutch group has signed up Tscan Therapeutics, a biotech currently focused on oncology, to help it develop an assay for coronavirus-reactive T cells. The success of Qiagen’s Covid-19 testing business gave the group the courage to opt out of being acquired by Thermo Fisher Scientific, but it needs to keep on top of new innovations. So far, however, Qiagen is some way behind groups including Oxford Immunotec and Adaptive Biotechnologies in the T-cell testing space.
It is believed that a T-cell immune response to Covid-19 might provide longer-term protection against reinfection with the virus than antibodies, kicking in earlier and lasting longer. Detecting responsive T cells could provide a more reliable way to determine exposure to the coronavirus and, if a link to some level of immunity can be proven, perhaps allow at least some people to return to normal life.
Tscan’s technology is currently geared towards engineering T cells to recognise and kill cancer cells. Qiagen has taken an option to several of Tscan’s immunodominant T-cell targets, associated sequences and other data to help with the development of in vitro diagnostic tests. Before exercising this option, Qiagen has the right to further evaluate Tscan’s discoveries. Terms of the deal were not disclosed.
Immunodominance refers to the ability of some viral antigens or epitopes to induce a meaningful immune response, where others do not. The immunodominant targets Qiagen has licensed were identified by Tscan’s TCR/Target discovery platform, which mapped the specific epitopes in Sars-Cov-2 that are recognised by the CD8+ T cells of patients recovering from Covid-19.
Detect and discover
It is not clear how long it might take Qiagen to turn this technology into a working test for Covid-19 exposure. What is apparent is that the company is behind at least two others in this space.
This week data emerged on Oxford Immunotec’s T-Spot Discovery Sars-CoV-2 test, making a tentative link between a T-cell response and resistance to reinfection with the virus (First data hint at T-cell immunity to Covid-19, November 10, 2020). And a study of a T-cell test developed by Adaptive Biotechnologies has also been detailed in a preprint.
Adaptive conducted a 100-patient head-to-head study comparing its T-Detect Covid test with two antibody tests – Roche’s Elecsys Anti-Sars-Cov-2, which tests for both IgG and IgM, and Labcorp’s Sars-Cov-2 Antibody IgG test. The tests were set at 99.8% specificity to minimise false positives. In this study, 94% of patients were detected as positive by Adaptive’s T-cell test versus 90% for Roche’s and 87% for Labcorp’s respectively.
In a different study, performed in collaboration with the University of Padua in Italy, which has not been published but was toplined during Adaptive’s third-quarter call on Tuesday, T-Detect Covid identified 97% of PCR-confirmed past infections, while an antibody test from Diasorin identified only 77%.
Adaptive intends to submit these data to the FDA to support emergency use authorisation for T-Detect. Oxford Immunotec is cagey about its regulatory plans, but if Adaptive can get an EUA for a T-cell test then in principle there is nothing barring the way for T-Spot Discovery. Qiagen might have to get its skates on.