Herbal plant-derived compound, 1,2,3,4,6-penta-O-galloyl-β-d-glucose, increases cross-presentation by dendritic cells

Aim: Vaccines have made great contributions to human welfare, and can be used even more effectively with adjuvants. The immune-inducible effects of adjuvants are classified into four categories: T-helper (Th)1, Th2, antibody, and cytotoxic T-lymphocyte (CTL) responses. Exogenous antigens are mainly presented to major histocompatibility complex (MHC) class II molecules, but are also presented to MHC class I molecules via the antigen cross-presentation process in dendritic cells. The enhancement of cross-presentation of an injected vaccine antigen by an adjuvant leads to Th1 and CTL responses, resulting in successful intracellular infection and tumor vaccine therapy. Methods: It is widely known that herbal medicines have strong immune response effects. With this in mind, we developed a novel vaccine adjuvant from natural compounds used in herbal medicine, through an in vitro model vaccine antigen (ovalbumin, OVA) cross-presentation assay. Results: Among 89 natural compounds, 1,2,3,4,6-penta-O-galloyl-β-d-glucose (PGG) most enhanced cross-presentation in dendritic cells. While the expression of MHC class II molecules was suppressed, PGG enhanced the expression of MHC class I molecules, restricted to OVA-derived peptides. Conclusion: Restricted MHC class I expression resulting from the use of PGG enhanced cross-presentation by dendritic cells.