Improved dendritic cell‐based immunization against hepatitis C virus using peptide inhibitors of interleukin 10

The high levels of interleukin 10 (IL‐10) present in chronic hepatitis C virus (HCV) infection have been suggested as responsible for the poor antiviral cellular immune responses found in these patients. To overcome the immunosuppressive effect of IL‐10 on antigen‐presenting cells such as dendritic cells (DCs), we developed peptide inhibitors of IL‐10 to restore DC functions and concomitantly induce efficient antiviral immune responses. Two IL‐10‐binding peptides (p9 and p13) were selected using a phage‐displayed library and their capacity to inhibit IL‐10 was assessed in a bioassay and in STAT‐3 (signal transducer and activator of transcription 3) phosphorylation experiments in vitro. In cultures of human leukocytes where HCV core protein induces the production of IL‐10, p13 restored the ability of plasmacytoid DC to produce interferon alpha (IFN‐α) after Toll‐like receptor 9 (TLR9) stimulation. Similarly, when myeloid DCs were stimulated with CD40L in the presence of HCV core, p9 enhanced IL‐12 production by inhibiting HCV core‐induced as well as CD40L‐induced IL‐10. Moreover, in vitro, p13 potentiated the effect of maturation stimuli on human and murine DC, increasing their IL‐12 production and stimulatory activity, which resulted in enhanced proliferation and IFN‐γ production by responding T‐cells. Finally, immunization with p13‐treated murine DC induced stronger anti‐HCV T‐cell responses not only in wildtype mice but also in HCV transgenic mice and in mice transiently expressing HCV core in the liver. Conclusion: These results suggest that IL‐10 inhibiting peptides may have important applications to enhance anti‐HCV immune responses by restoring the immunostimulatory capabilities of DC. (HEPATOLOGY 2011.)