Figure 6: Proliferative capacity of HCV-specific CD8⁺ T cells correlates with TCF1 expression.

HCV epitope-specific CD8⁺ T cells of eight HCV-infected patients (eleven HCV epitope-specific CD8⁺ T-cell responses) and four spontaneous resolvers (SpR; five HCV epitope-specific CD8⁺ T-cell responses) were expanded at baseline and at end of therapy (EOT) for 14 days by HCV epitope-specific peptides and proliferative capacity was determined by the expansion factor. The expansion factor is the logarithmic fold-increase in absolute numbers of HCV epitope-specific CD8⁺ T cells from day 0 to day 14 of in vitro culture. (a) Representative dot plots of HCV epitope-specific CD8⁺ T cells determined by peptide/MHCI and CD8 staining at day 14 of expansion at baseline (left plot) or at end of therapy (EOT; right plot), respectively. Quantification of proliferative capacity of HCV epitope-specific CD8⁺ T cells derived from donors at baseline, at EOT and of SpR is depicted on the right. (b,c) Correlation analyses of the expansion factor with the abundance of memory-like CD127⁺PD1⁺ (b) or TCF1⁺ (c) HCV epitope-specific CD8⁺ T cells at day 0 of the assay, respectively (grey: baseline; black: EOT; open circles: SpR). Bar chart shows the median value with interquartile range. Statistical significance was assessed with Wilcoxon test (HCV/DAA Baseline to EOT), multiple comparisons with Kruskal–Wallis and Dunn’s test (SpR to cHCV Baseline/EOT). Pearson correlation in (b,c) was performed. (*P<0.05; **P<0.01; ****P<0.0001.)