Discovery of KC-1: A Novel Porcine Dendritic Cell-Targeting Peptide with Potential Applications in Swine Vaccine Design

Dendritic cells (DCs) are key antigen-presenting cells essential for initiating and regulating immune responses. While DC targeting has proven to be an effective strategy for vaccine enhancement, and targeting peptides have been extensively utilized as efficient delivery tools in DC-targeted drug and vaccine development, there remains a notable scarcity of peptides specifically selected through porcine dendritic cell screening platforms. In this study, phage display biopanning was employed to screen a novel DC-targeting peptide, designated KC (KCCYPNQMAAFA). Systematic alanine-scanning mutagenesis identified the N-terminal hexapeptide KC-1 (KCCYPN) as the minimal functional epitope responsible for DC binding. In addition to DCs, KC-1 was also demonstrated selective binding to bone marrow-derived dendritic cells (BM-DCs) and porcine alveolar macrophages (PAMs) but exhibited no interaction with intestinal porcine epithelial (IPI) cells, swine testis (ST) cells, or Vero cells. Further analysis revealed that KC-1 specifically bounds to the N-terminal region (1-126 aa) of SLA-DRB1, which is a key domain of the MHC II β-chain involved in the formation of the peptide-binding groove. Using the PEDV S1 subunit as a model antigen, we further evaluated the immunomodulatory effects of KC-1 on DCs in vitro. The results demonstrated that KC-1-S1 significantly promoted dendritic cell maturation and T cell proliferation, accompanied by increased secretion of key cytokines IL-4, IL-12, and IFN-γ, indicating enhanced activation of both humoral and cellular immune responses with a balanced Th1/Th2 polarization compared to controls. Collectively, these findings establish a theoretical foundation for porcine DC-targeted peptides and provide critical insights for the development of next-generation porcine DC-targeted vaccines.