Spike is the most recognized antigen in the whole-blood platform in both acute and convalescent COVID-19 patients

OBJECTIVES: To identify the best experimental approach to detect a SARS-CoV-2-specific T cell response using a whole-blood platform. METHODS: Whole-blood from 56 COVID-19 and 23 “NO-COVID-19” individuals were stimulated overnight with different concentrations (0.1 or 1 μg/mL) of SARS-CoV-2 PepTivator® Peptide Pools, including spike (pool S), nucleocapsid (pool N), membrane (pool M), and a MegaPool (MP) of these three peptide pools. ELISA was used to analyse interferon (IFN)-γ levels. RESULTS: The IFN-γ-response to every SARS-CoV-2 peptide pool was significantly increased in COVID-19 patients compared with NO-COVID-19 individuals. Pool S and MegaPool were the most potent immunogenic stimuli (median: 0.51, IQR: 0.14–2.17; and median: 1.18, IQR: 0.27–4.72, respectively) compared with pools N and M (median: 0.22, IQR: 0.032–1.26; and median: 0.22, IQR: 0.01−0.71, respectively). The whole-blood test based on pool S and MegaPool showed a good sensitivity of 77% and a high specificity of 96%. The IFN-γ-response was mediated by both CD4(+) and CD8(+) T cells, and independently detected of clinical parameters in both hospitalized and recovered patients. CONCLUSIONS: This easy-to-use assay for detecting SARS-CoV-2-specific T cell responses may be implemented in clinical laboratories as a powerful diagnostic tool.