Comparison of T Cell Immune Responses Against SARS-CoV-2 Using QuantiFERON SARS-CoV-2 Assay Versus Peripheral Blood Mononuclear Cells Analysis by Flow Cytometry

Introduction COVID-19 continues to have a global impact with the emergence of the latest variant of interest: JN.01, the commonest worldwide. While most studies on immune responses against SARS-CoV-2 are based on the evaluation of the humoral arm, data regarding cell-mediated immune responses are sparse and still emerging. Materials and methods A sample of 51 study participants was subjected to an interferon gamma release assay (QuantiFERON SARS-CoV-2). T cell (CD4+ or CD8+) responses to SARS-CoV-2 were characterized in a subset of 10 participants using multicolor flow cytometry. Results Thirty-seven participants had positive results for the anti-SARS-CoV-2 IgG antibody, and QuantiFERON SARS-CoV-2 assay antigen 1 and 2 positivity was observed in two participants only. In comparison, upon analyzing peripheral blood mononuclear cells using flow cytometry in a subset of 10 participants negative for the QuantiFERON SARS-CoV-2 assay, five had positive T cell immune responses. Conclusion Our study demonstrates higher positivity for T cell response among 10 adult individuals when tested using flow cytometry for peripheral blood mononuclear cell analysis as compared to the interferon gamma release assay. Such data on immune responses to SARS-CoV-2 will be useful in developing predictive B- and T cell-based immune correlates and algorithms for personalized risk assessment and clinical response evaluation.