Performance of the T-SPOT®.COVID test for detecting SARS-CoV-2-responsive T cells

Kruse, Margaret; Dark, Chris; Aspden, Megan; Cochrane, Daniel; Competiello, Rick; Peltz, Maya; Torres, Luis; Wrighton-Smith, Peter; Dudek, Magdalena

Objective This study evaluated the performance of the T-SPOT.COVID test for identifying SARS-CoV-2-responsive T-cells in subjects with SARS-CoV-2 infections. Methods The T-SPOT.COVID test uses ELISpot interferon-gamma release assay (IGRA) methodology to measure T cell responses to SARS-CoV-2 spike S1 and nucleocapsid peptides. T-SPOT.COVID and anti-N IgG serology tests were performed on blood from 186 subjects with NAAT-confirmed-SARS-CoV-2 infections and 100 control subjects. Results In the 2-8 week-period after NAAT-diagnosed SARS-CoV-2 infection, the T-SPOT.COVID test detected 98.4% (63/64) of infected subjects; in comparison, anti-N IgG serology detected fewer in this time period (82.8%, 53/64). In the first 2 weeks after diagnosis, during activation of the adaptive immune response, there were fewer reactive T-SPOT.COVID responses (75.7%, 28/37) and many fewer seropositive responses (32.4%, 12/37). Response numbers tapered somewhat after 8 weeks, although T-SPOT.COVID test continued to detect most of the confirmed-infection subjects (83.6%, 56/67) and continued to out-perform serology (52.2%, 35/67). The possibility of T-SPOT.COVID responses due to cross-reactive T cells was ruled out by demonstrating that, of 44 control subjects with T cells responsive to four human common cold coronavirus peptides, only 1 was T-SPOT.COVID reactive. Conclusion The T-SPOT.COVID test performed well in detecting SARS-CoV-2-sensitized T-cells over many months.