Baccatin III, a synthetic precursor of taxol, enhances MHC-restricted antigen presentation in dendritic cells.

Baccatin III, a precursor for the semisynthesis of taxol, is widely considered to be an inactive derivative of taxol. Here we show that baccatin III efficiently enhances MHC-restricted antigen presentation in dendritic cells. Baccatin III increased both class I- and class II-restricted presentation of exogenous OVA in bone marrow-derived dendritic cells (BM-DCs). Baccatin III also increased class I-restricted presentation of virus-encoded endogenous OVA in BM-DCs. Baccatin III did not affect the phagocytic activity of BM-DCs. The antigen presentation-enhancing activity of baccatin III was examined further with nanoparticles containing OVA and baccatin III. Inclusion of baccatin III to nanoparticles containing OVA greatly enhanced their capacity to induce class I-restricted OVA peptide presentation in DCs both in vitro and in vivo. Accordingly, nanoparticles containing both OVA and baccatin III were much more efficient in inducing an OVA-specific CTL response in mice compared to those containing OVA only. These results demonstrate that baccatin III exerts immunomodulatory activities in vivo as well as in vitro on the MHC-restricted antigen presentation.