Session Time: 6:00pm-7:00pm
Presentation Time: 6:25pm-6:30pm
*Purpose: The need to evaluate SARS-CoV-2 immune responses is an important clinical research focus. Detecting neutralizing antibodies is one measure of immune response, but the ability to evaluate CD4 and CD8 T cell responses specific to SARS-CoV-2 is also an important measure of immune status. The role these two arms of the immune system play in protection is currently unknown.
*Methods: We developed a whole blood flow cytometry assay that detects functional CD4 and CD8 responses to stimulation by peptide antigen pools encompassing the spike (S1 – receptor binding domain (RBD) and S2) and nucleocapsid (N) proteins to address this need. Activated T cells were defined as CD4 or CD8 T cells co-expressing the CD69 activation marker with IFN-γ, TNF-α or IL-2. Polyfunctional T cells, expressing multiple cytokines, were also identified. This assay was validated using whole blood from SARS-CoV-2 recovered volunteers and apparently normal donors who self-reported as uninfected by SARS-CoV-2.
*Results: The range in responses varied by donor and was not correlated with the reported severity of their disease. A positive response was defined as a 3-fold increase in the number of activated T cells over the unstimulated control. Of the 32 SARS-CoV-2 recovered donors tested, 25 responded to two or three of the peptide pools and five did not respond to any SARS-CoV-2 peptides. Responses ranged from 0.03% up to 1.23% of the CD4 or CD8 population. The responding T cells were predominantly CD4, but when CD8 T cells responded they tended to recognize the nucleocapsid peptides most strongly. Data from one individual with a robust response are shown below.
|Cell populations||No stim||S1 (RBD)||S2||N|
For uninfected donors, five of 21 showed a low, but detectable response to stimulation with at least one peptide pool. These responses could be attributed to an asymptomatic infection, or to cross-reactive T cells specific to one of the seasonal respiratory coronaviruses.
*Conclusions: In summary, we developed a sensitive assay to detect SARS-CoV-2 spike- and nucleocapsid-specific T cell responses in whole blood samples. This assay will be valuable in monitoring SARS-CoV-2 T cell response and duration in infected individuals. Measuring the T cell responses to SARS-CoV-2 vaccinated individuals is currently under investigation.
To cite this abstract in AMA style:Flebbe-Rehwaldt L, Hayden J, Mickey K, Manley S, Kleiboeker S. Detection of SARS-CoV-2 Specific Functional T Cells Using a Seven Color Flow Cytometry Assay [abstract]. Am J Transplant. 2021; 21 (suppl 3). https://atcmeetingabstracts.com/abstract/detection-of-sars-cov-2-specific-functional-t-cells-using-a-seven-color-flow-cytometry-assay/. Accessed June 18, 2021.
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