A novel peptide targeting Clec9a on dendritic cell for cancer immunotherapy

Dendritic cells (DCs) are professional antigen-presenting cells with antigen recognition molecules on the surface. Clec9a is selectively expressed on mouse CD8a+ DCs and CD103+ DCs subsets, which are functionally similar to human BDCA3+ DCs. It is reported that Clec9a is responsible for the antigen cross-presentation of these DC subsets. In the present study, by using phage display technique, we discovered a novel peptide WH, which can selectively bind to mouse Flt3L induced Clec9a+ DCs or Clec9a over-expressed HEK-293T cells. Furthermore, by using computer-aided docking model and mutation assay, we observed that Asp248 and Trp250 are two key residues for Clec9a to bind with peptide WH. When coupled with OVA257-264 epitope, peptide WH can significantly enhance the ability of Clec9a+ DCs to activate OVA-specific CD8+ T cells, which elicit strong ability to secret IFN-γ, express perforin and granzyme B mRNA. In B16-OVA lung metastasis mouse model, WH-OVA257-264 fusion peptide can also enhance the activation of CD8+ T cells and decrease the lung metastasis loci. All these results suggested that peptide WH could be considered as an antigen delivery carrier targeting Clec9a+ DCs for cancer immunotherapy.