Coating of mannan on LPD particles containing HPV E7 peptide significantly enhances immunity against HPV-positive tumor.

Purpose: Previously, our laboratory has reported that liposome-protamine-DNA (LPD) nanoparticle is an effective delivery system for tumor-associated antigens. Mannan, which potentially targets antigen-presenting cells, was coated on LPD to further enhance its antitumor activity.

Methods: Cholesterol-conjugated mannan was coated on LPD. The abilities of mannan-coated LPD to target antigen-presenting cells, to activate dendritic cells, and to induce antitumor immunity were investigated and compared to those of LPD alone.

Results: Both in vitro and in vivo uptake of LPD showed that mannan-coated LPD particles were preferably taken up by dendritic cells and macrophages. In addition, the expression of co-stimulatory molecules CD80/CD86 on DC2.4 cells after co-incubation with mannan-coated LPD was significantly higher than that after co-incubation with LPD. A model major histocompatibility complex class I-restricted peptide antigen from HPV 16 E7 protein was incorporated into LPD to immunize mice against the growth of TC-1 tumor cells expressing E7 protein. Coating with mannan significantly enhanced both preventive and therapeutic activities of LPD/E7. Finally, the release of IFN-gamma from isolated splenocytes was significantly enhanced when mice were immunized with mannan-coated LPD/E7 than with LPD/E7 alone.

Conclusion: Targeting of the LPD/E7 to local draining lymph nodes by mannan is partially responsible for the enhanced anti-tumor activity.