Fig. 3: Functional assessment of the ability for in vitro expansion of SARS-CoV-2 nucleocapsid-specific CD8⁺ T cells.

a Experimental overview of functional assessment of in vitro antigen-induced activation and expansion of nucleocapsid-specific CD8⁺ T cells. AIM = activation induced marker measurement and APC = artificial antigen presentation complex assay. Image created using BioRender.com. b Ranking based on the percentage and degree of epitope-specific CD8⁺ T cell expansion post fourteen-day stimulation with nucleocapsid epitopes. Expansion is categorized based on the fold change of antigen-specific cells after fourteen days (none≤1, mild 1 <x < 3, robust ≥3 divisions). c Fold change of LLL-specific CD8⁺ T cells after stimulation. Each point represents an average value of each convalescent donor stimulated with LLL peptide-HLA-A2 (Convalescent n = 34, Uninfected n = 43), Two-tailed T-test adjusted for age and sex was carried out for all comparisons between convalescent and uninfected donor. p value, mean and SEM are shown. d Correlation between seeding LLL-specific T_EM cell counts on day 0 and harvested LLL-specific CD8⁺ T cell counts after stimulation. Values were log₁₀ transformed and the purple trend line across all data for each subject were generated by the mixed effect linear regression model (adjusted for age and sex) with error bounds indicating a 95% confidence interval (light gray) showing the correlation of cell numbers between day 0 and day 14 (R² = 0.09, p = 0.009). e Stability of in vitro expansion of LLL-specific CD8⁺ T cells over time. Expansion of LLL-specific CD8⁺ T cells of convalescent donors were placed into three categories (increased expansion, decreased expansion, no major change in expansion) based on changes in expansion across different visits among three designated degrees of expansion (no, mild and robust expansion).