Novel T cell interferon gamma release assay (IGRA) using spike recombinant protein for COVID19 vaccine response and Nucleocapsid for SARS-Cov2 response.

We explored the performance of a whole blood interferon gamma release assay (IGRA) based on the stimulation of SARS-Cov2-specific T cells by purified recombinant proteins. Twenty volunteers vaccinated with BNT162b2 were selected first for T cell response evaluation using an in-house IGRA, a commercial IGRA, and ELISpot showing a S2 > S1 poly-epitopic response. Next, 64 vaccinated and 103 non-vaccinated individuals were tested for humoral and T cell response (IGRA-Spike/-nucleocapsid recombinant proteins). Following the second vaccine injection, humoral (100%) and IGRA-Spike T cell (95.3%) responses took place irrespective of sex, age, and vaccine type. The humoral response declined first, followed by IGRA-Spike T cell response after the second vaccine injection. Altogether, this study confirms the utility of the IGRA-Spike/-nucleocapsid assay to complement serology in COVID19 vaccinated individuals and those who have recovered from SARS-Cov2.