SARS-CoV-2 mRNA vaccination induces an antigen-specific T cell response correlating with plasma interferon-gamma in B cell depleted patients.

Emerging evidence is encouraging and suggests that a substantial proportion of patients without antibody responses (due to anti-CD20 therapy or other etiologies) to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccines develop T cell responses. However, antigen-specific T cellular responses are notoriously difficult to assess clinically, given the lack of such assays under satisfactory CAP/CLIA regulation, and the laborious nature of the flow cytometric assessment. To evaluate the ability to apply a clinically feasible assay to measure T cellular responses to SARS-CoV-2 mRNA vaccination, we compared flow cytometric and enzyme-linked immunosorbent assay (ELISA) based assays in 24 participants treated with anti-CD20 therapy. T cellular activation (CD69 + CD137+ surface expression, i.e., activation induced markers [AIM]) and intracellular interferon gamma (INFγ) production via flow cytometry was compared to plasma Interferon Gamma Release Assay (IGRA) via ELISA. Plasma INFγ production measured by IGRA correlated with the percent of INFγ-producing AIM positive T cells, supporting the use of IGRA assay as a robust assessment of T cellular response to the SARS-CoV-2 vaccine for B-cell depleted patients that is clinically feasible, time efficient, and cost effective.