Performance comparison of a flow cytometry immunoassay for intracellular cytokine staining and the QuantiFERON® SARS-CoV-2 test for detection and quantification of SARS-CoV-2-Spike-reactive-IFN-γ-producing T cells after COVID-19 vaccination

• DOI: 10.1007/s10096-022-04422-7
• Publication Date: 2022-02-15T03:02:54Z
• Authors: Nuria Tormo; Estela Giménez; María Martínez-Na...; Eliseo Albert; David Navalpotro; Ignacio Torres; Concepción Gimeno; David Navarro
• Keywords: Adult; Immunoassay; Male; 0301 basic medicine; COVID-19 Vaccines; SARS-CoV-2 T cells; Staining and Labeling; SARS-CoV-2; Vaccination; COVID-19; CD8-Positive T-Lymphocytes; Flow cytometry-based immunoassay; Antibodies, Viral; Flow Cytometry; 3. Good health; SARS-CoV-2 S protein; 03 medical and health sciences; Spike Glycoprotein, Coronavirus; Cytokines; Humans; QuantiFERON® SARS-CoV-2; Original Article; COVID-19 vaccine

We compared the performance of an in-house-developed flow cytometry assay for intracellular cytokine staining (FC-ICS) and a commercially-available cytokine release assay (the QuantiFERON® SARS-CoV-2 Test [QF]) for detection and quantification of SARS-CoV-2-Spike (S)-reactive-IFN-γ-producing T cells after COVID-19 vaccination.The sample included 141 individuals (all male; median age, 42 years; 20-72) who had been fully vaccinated with the Comirnaty® COVID-19 vaccine (at a median of 114 days; 34-145). Prior to vaccination, 91 were categorized as being SARS-CoV-2-naïve and 50 as SARS-CoV-2-experienced. A whole blood-based FC-ICS using 15-mer overlapping peptides encompassing the entire SARS-CoV-2 S protein was used for enumeration of virus-specific IFN-γ-producing CD4+ and CD8+ T cells. The QF test (Ag1 for CD4+ T cells and Ag2 for CD4+ and CD8+ T cells in combination) was carried out following the manufacturer's instructions.The FC-ICS and the QF assays returned significantly discordant qualitative results in both the entire cohort (P<0.001 with QF Ag1 and QF Ag2) and in SARS-CoV-2-naïve participants alone (P=0.005 and P=0.01, respectively). Discrepant results mostly involved FC-ICS positive/QF negative specimens. Overall, no correlation was found either between SARS-CoV-2 IFN-γ- CD4+ T-cell frequencies and IFN-γ levels measured in the QF Ag1 tube (P=0.78) or between the sum of SARS-CoV-2 IFN-γ CD4+ and CD8+ T-cell frequencies and IFN-γ levels quantified in the QF Ag2 tube.The data suggest a greater sensitivity for the FC-ICS assay than the QF test, and urge caution when comparing SARS-CoV-2 T-cell immune responses assessed using different analytical platforms.