Core-specific adaptive regulatory T-cells in different outcomes of hepatitis C

CD4⁺ T_reg-cells (regulatory T-cells) probably contribute to the impaired virus-specific T-cell responses in chronic HCV (hepatitis C virus) infection; however, their antigen-specificity has remained elusive. In the present study, we analysed peripheral blood CD4⁺ T_reg-cells in patients with chronic hepatitis C and subjects with self-limited HCV infection and characterized individual T_reg-cell clones obtained from both groups at the phenotypic and functional level. Foxp3 (forkhead box p3)⁺CD25⁺CD4⁺ T_reg-cells were detected more frequently in patients with chronic hepatitis C than self-limited HCV infection, which responded to HCV core stimulation and inhibited proliferation of reporter cells. Cloning under limiting dilution conditions resulted in 14 and six hypoproliferative Foxp3⁺CD25⁺CD127⁻CD4⁺ T-cell clones from patients with chronic hepatitis C and subjects with self-limited HCV infection respectively. All clones expressed T_reg-cell markers and produced IL (interleukin)-10 upon mitogen stimulation. However, exclusively T_reg-cell clones from chronic hepatitis C produced IL-10 in response to HCV core and inhibited proliferation of reporter T-cells. These core-specific T_reg-cell clones recognized epitopes in two regions of HCV core (amino acids 1–44 and 79–113). Co-culture inhibition assays demonstrated T_reg-cells to inhibit reporter T-cells via secretion of IL-10 and IL-35 rather than cell-contact-dependent mechanisms. Finally, the HCV-specific T_reg-cell clones lost their functional capacity, along with Foxp3 expression, if kept in culture without HCV core exposure. In conclusion, we identified functionally active HCV core-specific T_reg-cells in patients with chronic hepatitis C, which share their epitopes with conventional T-cells and require the continued presence of antigen to maintain their functional differentiation. Thus HCV core-specific T_reg-cells may contribute to the immunoregulatory balance in chronic hepatitis C.